WorldWideScience

Sample records for density-dependent cell state-specific

  1. Maitra-Burke example of initial-state dependence in time-dependent density-functional theory

    International Nuclear Information System (INIS)

    Holas, A.; Balawender, R.

    2002-01-01

    In a recent paper, Maitra and Burke [Phys. Rev. A 63, 042501 (2001); 64, 039901(E) (2001)] have given an interesting and instructive example that illustrates a specific feature of the time-dependent density-functional theory--the dependence of the reconstructed time-dependent potential not only on the electron density, but also on the initial state of the system. However, a concise form of its presentation by these authors is insufficient to reveal all its peculiarities. Our paper represents a very detailed study of this valuable example, intended to facilitate a better understanding and appreciation

  2. Control of density-dependent, cell state-specific signal transduction by the cell adhesion molecule CEACAM1, and its influence on cell cycle regulation

    International Nuclear Information System (INIS)

    Scheffrahn, Inka; Singer, Bernhard B.; Sigmundsson, Kristmundur; Lucka, Lothar; Oebrink, Bjoern

    2005-01-01

    Growth factor receptors, extracellular matrix receptors, and cell-cell adhesion molecules co-operate in regulating the activities of intracellular signaling pathways. Here, we demonstrate that the cell adhesion molecule CEACAM1 co-regulates growth-factor-induced DNA synthesis in NBT-II epithelial cells in a cell-density-dependent manner. CEACAM1 exerted its effects by regulating the activity of the Erk 1/2 MAP kinase pathway and the expression levels of the cyclin-dependent kinase inhibitor p27 Kip1 . Interestingly, both inhibitory and stimulatory effects were observed. Confluent cells continuously exposed to fetal calf serum showed little Erk activity and DNA synthesis compared with sparse cells. Under these conditions, anti-CEACAM1 antibodies strongly stimulated Erk activation, decreased p27 expression, and induced DNA synthesis. In serum-starved confluent cells, re-addition of 10% fetal calf serum activated the Erk pathway, decreased p27 expression, and stimulated DNA synthesis to the same levels as in sparse cells. Under these conditions anti-CEACAM1 antibodies de-activated Erk, restored the level of p27, and inhibited DNA synthesis. These data indicate that CEACAM1 mediates contact inhibition of proliferation in cells that are constantly exposed to growth factors, but co-activates growth-factor-induced proliferation in cells that have been starved for growth factors; exposure to extracellular CEACAM1 ligands reverts these responses

  3. Electronic Excitations in Solution: The Interplay between State Specific Approaches and a Time-Dependent Density Functional Theory Description.

    Science.gov (United States)

    Guido, Ciro A; Jacquemin, Denis; Adamo, Carlo; Mennucci, Benedetta

    2015-12-08

    We critically analyze the performances of continuum solvation models when coupled to time-dependent density functional theory (TD-DFT) to predict solvent effects on both absorption and emission energies of chromophores in solution. Different polarization schemes of the polarizable continuum model (PCM), such as linear response (LR) and three different state specific (SS) approaches, are considered and compared. We show the necessity of introducing a SS model in cases where large electron density rearrangements are involved in the excitations, such as charge-transfer transitions in both twisted and quadrupolar compounds, and underline the very delicate interplay between the selected polarization method and the chosen exchange-correlation functional. This interplay originates in the different descriptions of the transition and ground/excited state multipolar moments by the different functionals. As a result, the choice of both the DFT functional and the solvent polarization scheme has to be consistent with the nature of the studied electronic excitation.

  4. Decay of autoionizing states in time-dependent density functional and reduced density matrix functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Kapoor, Varun; Brics, Martins; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)

    2013-07-01

    Autoionizing states are inaccessible to time-dependent density functional theory (TDDFT) using known, adiabatic Kohn-Sham (KS) potentials. We determine the exact KS potential for a numerically exactly solvable model Helium atom interacting with a laser field that is populating an autoionizing state. The exact single-particle density of the population in the autoionizing state corresponds to that of the energetically lowest quasi-stationary state in the exact KS potential. We describe how this exact potential controls the decay by a barrier whose height and width allows for the density to tunnel out and decay with the same rate as in the ab initio time-dependent Schroedinger calculation. However, devising a useful exchange-correlation potential that is capable of governing such a scenario in general and in more complex systems is hopeless. As an improvement over TDDFT, time-dependent reduced density matrix functional theory has been proposed. We are able to obtain for the above described autoionization process the exact time-dependent natural orbitals (i.e., the eigenfunctions of the exact, time-dependent one-body reduced density matrix) and study the potentials that appear in the equations of motion for the natural orbitals and the structure of the two-body density matrix expanded in them.

  5. Decay of hollow states in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Kapoor, Varun; Bauer, Dieter [Institut fuer Physik, Wismarsche Str. 43-45, Universitaet Rostock, Rostock-18051 (Germany)

    2012-07-01

    Hollow or multiply excited states are inaccessible in time dependent density functional theory (TDDFT) using adiabatic Kohn-Sham potentials. We determine the exact Kohn Sham (KS) potential for doubly excited states in an exactly solvable model Helium atom. The exact single-particle density corresponds to the energetically lowest quasi-stationary state in the exact KS potential. We describe how this exact potential controls the decay by a barrier whose origin is traced back to phase of the exact KS orbital. The potential controls the barrier height and width in order for the density to tunnel out and decay with the same rate as the doubly excited state in the ab initio time-dependent Schroedinger calculation. Instead, adiabatic KS potentials only show direct photoionization but no autoionization. A frequency-dependent linear response kernel would be necessary in order to capture the decay of autoionizing states.

  6. Separation of active and inactive fractions from starved culture of Vibrio parahaemolyticus by density dependent cell sorting.

    Science.gov (United States)

    Nayak, Binaya Bhusan; Kamiya, Eriko; Nishino, Tomohiko; Wada, Minoru; Nishimura, Masahiko; Kogure, Kazuhiro

    2005-01-01

    The co-existence of physiologically different cells in bacterial cultures is a general phenomenon. We have examined the applicability of the density dependent cell sorting (DDCS) method to separate subpopulations from a long-term starvation culture of Vibrio parahaemolyticus. The cells were subjected to Percoll density gradient and separated into 12 fractions of different buoyant densities, followed by measuring the cell numbers, culturability, respiratory activity and leucine incorporation activity. While more than 78% of cells were in lighter fractions, about 95% of culturable cells were present in heavier fractions. The high-density subpopulations also had high proportion of cells capable of forming formazan granules. Although this was accompanied by the cell specific INT-reduction rate, both leucine incorporation rates and INT-reduction rates per cell had a peak at mid-density fraction. The present results indicated that DDCS could be used to separate subpopulations of different physiological conditions.

  7. Cell density dependence of Microcystis aeruginosa responses to copper algaecide concentrations: Implications for microcystin-LR release.

    Science.gov (United States)

    Kinley, Ciera M; Iwinski, Kyla J; Hendrikse, Maas; Geer, Tyler D; Rodgers, John H

    2017-11-01

    Along with mechanistic models, predictions of exposure-response relationships for copper are often derived from laboratory toxicity experiments with standardized experimental exposures and conditions. For predictions of copper toxicity to algae, cell density is a critical factor often overlooked. For pulse exposures of copper-based algaecides in aquatic systems, cell density can significantly influence copper sorbed by the algal population, and consequent responses. A cyanobacterium, Microcystis aeruginosa, was exposed to a copper-based algaecide over a range of cell densities to model the density-dependence of exposures, and effects on microcystin-LR (MC-LR) release. Copper exposure concentrations were arrayed to result in a gradient of MC-LR release, and masses of copper sorbed to algal populations were measured following exposures. While copper exposure concentrations eliciting comparable MC-LR release ranged an order of magnitude (24-h EC50s 0.03-0.3mg Cu/L) among cell densities of 10 6 through 10 7 cells/mL, copper doses (mg Cu/mg algae) were similar (24-h EC50s 0.005-0.006mg Cu/mg algae). Comparisons of MC-LR release as a function of copper exposure concentrations and doses provided a metric of the density dependence of algal responses in the context of copper-based algaecide applications. Combined with estimates of other site-specific factors (e.g. water characteristics) and fate processes (e.g. dilution and dispersion, sorption to organic matter and sediments), measuring exposure-response relationships for specific cell densities can refine predictions for in situ exposures and algal responses. These measurements can in turn decrease the likelihood of amending unnecessary copper concentrations to aquatic systems, and minimize risks for non-target aquatic organisms. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Isotope effect with energy-dependent density of states and impurities

    International Nuclear Information System (INIS)

    Williams, P.J.; Carbotte, J.P.

    1992-01-01

    We have calculated the total isotope coefficient β in a model where there is energy-dependent structure in the electronic density of states. We model the structure with a simple Lorentzian. In our calculation, doping has the effect of shifting the Fermi level and broadening the structure in the density of states. We have treated the dopants both as normal and as magnetic impurities. The asymmetry observed in the experimental data is found in our results. However, the complete range of values observed is difficult to reproduce. We question also whether the shifts in Fermi level required in such models are reasonable

  9. Single-particle energies and density of states in density functional theory

    Science.gov (United States)

    van Aggelen, H.; Chan, G. K.-L.

    2015-07-01

    Time-dependent density functional theory (TD-DFT) is commonly used as the foundation to obtain neutral excited states and transition weights in DFT, but does not allow direct access to density of states and single-particle energies, i.e. ionisation energies and electron affinities. Here we show that by extending TD-DFT to a superfluid formulation, which involves operators that break particle-number symmetry, we can obtain the density of states and single-particle energies from the poles of an appropriate superfluid response function. The standard Kohn- Sham eigenvalues emerge as the adiabatic limit of the superfluid response under the assumption that the exchange- correlation functional has no dependence on the superfluid density. The Kohn- Sham eigenvalues can thus be interpreted as approximations to the ionisation energies and electron affinities. Beyond this approximation, the formalism provides an incentive for creating a new class of density functionals specifically targeted at accurate single-particle eigenvalues and bandgaps.

  10. Effects of hepatocyte growth factor on glutathione synthesis, growth, and apoptosis is cell density-dependent

    International Nuclear Information System (INIS)

    Yang Heping; Magilnick, Nathaniel; Xia Meng; Lu, Shelly C.

    2008-01-01

    Hepatocyte growth factor (HGF) is a potent hepatocyte mitogen that exerts opposing effects depending on cell density. Glutathione (GSH) is the main non-protein thiol in mammalian cells that modulates growth and apoptosis. We previously showed that GSH level is inversely related to cell density of hepatocytes and is positively related to growth. Our current work examined whether HGF can modulate GSH synthesis in a cell density-dependent manner and how GSH in turn influence HGF's effects. We found HGF treatment of H4IIE cells increased cell GSH levels only under subconfluent density. The increase in cell GSH under low density was due to increased transcription of GSH synthetic enzymes. This correlated with increased protein levels and nuclear binding activities of c-Jun, c-Fos, p65, p50, Nrf1 and Nrf2 to the promoter region of these genes. HGF acts as a mitogen in H4IIE cells under low cell density and protects against tumor necrosis factor α (TNFα)-induced apoptosis by limiting JNK activation. However, HGF is pro-apoptotic under high cell density and exacerbates TNFα-induced apoptosis by potentiating JNK activation. The increase in cell GSH under low cell density allows HGF to exert its full mitogenic effect but is not necessary for its anti-apoptotic effect

  11. Optimization of human corneal endothelial cell culture: density dependency of successful cultures in vitro.

    Science.gov (United States)

    Peh, Gary S L; Toh, Kah-Peng; Ang, Heng-Pei; Seah, Xin-Yi; George, Benjamin L; Mehta, Jodhbir S

    2013-05-03

    Global shortage of donor corneas greatly restricts the numbers of corneal transplantations performed yearly. Limited ex vivo expansion of primary human corneal endothelial cells is possible, and a considerable clinical interest exists for development of tissue-engineered constructs using cultivated corneal endothelial cells. The objective of this study was to investigate the density-dependent growth of human corneal endothelial cells isolated from paired donor corneas and to elucidate an optimal seeding density for their extended expansion in vitro whilst maintaining their unique cellular morphology. Established primary human corneal endothelial cells were propagated to the second passage (P2) before they were utilized for this study. Confluent P2 cells were dissociated and seeded at four seeding densities: 2,500 cells per cm2 ('LOW'); 5,000 cells per cm2 ('MID'); 10,000 cells per cm2 ('HIGH'); and 20,000 cells per cm2 ('HIGH(×2)'), and subsequently analyzed for their propensity to proliferate. They were also subjected to morphometric analyses comparing cell sizes, coefficient of variance, as well as cell circularity when each culture became confluent. At the two lower densities, proliferation rates were higher than cells seeded at higher densities, though not statistically significant. However, corneal endothelial cells seeded at lower densities were significantly larger in size, heterogeneous in shape and less circular (fibroblastic-like), and remained hypertrophic after one month in culture. Comparatively, cells seeded at higher densities were significantly homogeneous, compact and circular at confluence. Potentially, at an optimal seeding density of 10,000 cells per cm2, it is possible to obtain between 10 million to 25 million cells at the third passage. More importantly, these expanded human corneal endothelial cells retained their unique cellular morphology. Our results demonstrated a density dependency in the culture of primary human corneal endothelial

  12. Controlled cell morphology and liver-specific function of engineered primary hepatocytes by fibroblast layer cell densities.

    Science.gov (United States)

    Sakai, Yusuke; Koike, Makiko; Kawahara, Daisuke; Hasegawa, Hideko; Murai, Tomomi; Yamanouchi, Kosho; Soyama, Akihiko; Hidaka, Masaaki; Takatsuki, Mitsuhisa; Fujita, Fumihiko; Kuroki, Tamotsu; Eguchi, Susumu

    2018-03-05

    Engineered primary hepatocytes, including co-cultured hepatocyte sheets, are an attractive to basic scientific and clinical researchers because they maintain liver-specific functions, have reconstructed cell polarity, and have high transplantation efficiency. However, co-culture conditions regarding engineered primary hepatocytes were suboptimal in promoting these advantages. Here we report that the hepatocyte morphology and liver-specific function levels are controlled by the normal human diploid fibroblast (TIG-118 cell) layer cell density. Primary rat hepatocytes were plated onto TIG-118 cells, previously plated 3 days before at 1.04, 5.21, and 26.1×10 3  cells/cm 2 . Hepatocytes plated onto lower TIG-118 cell densities expanded better during the early culture period. The hepatocytes gathered as colonies and only exhibited small adhesion areas because of the pushing force from proliferating TIG-118 cells. The smaller areas of each hepatocyte result in the development of bile canaliculi. The highest density of TIG-118 cells downregulated albumin synthesis activity of hepatocytes. The hepatocytes may have undergone apoptosis associated with high TGF-β1 concentration and necrosis due to a lack of oxygen. These occurrences were supported by apoptotic chromatin condensation and high expression of both proteins HIF-1a and HIF-1b. Three types of engineered hepatocyte/fibroblast sheets comprising different TIG-118 cell densities were harvested after 4 days of hepatocyte culture and showed a complete cell sheet format without any holes. Hepatocyte morphology and liver-specific function levels are controlled by TIG-118 cell density, which helps to design better engineered hepatocytes for future applications such as in vitro cell-based assays and transplantable hepatocyte tissues. Copyright © 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  13. Cell-density-dependent lysis and sporulation of Myxococcus xanthus in agarose microbeads.

    OpenAIRE

    Rosenbluh, A; Nir, R; Sahar, E; Rosenberg, E

    1989-01-01

    Vegetative cells of Myxococcus xanthus were immobilized in 25-microns-diameter agarose microbeads and incubated in either growth medium or sporulation buffer. In growth medium, the cells multiplied, glided to the periphery, and then filled the beads. In sporulation buffer, up to 90% of the cells lysed and ca. 50% of the surviving cells formed resistant spores. A strong correlation between sporulation and cell lysis was observed; both phenomena were cell density dependent. Sporulation proficie...

  14. Density of states measurements in a p-i-n solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Crandall, R.S.; Wang, Q. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    The authors describe results of density of states (DOS) profiling in p-i-n solar-cell devices using drive-level capacitance (DLC) techniques. Near the p-i interface the defect density is high, decreasing rapidly into the interior, reaching low values in the central region of the cell, and rising rapidly again at the n-i interface. They show that the states in the central region are neutral dangling-bond defects, whereas those near the interfaces with the doped layers are charged dangling bonds.

  15. A Room to Grow: The Residential Density-dependence of Childbearing in Europe and the United States

    Directory of Open Access Journals (Sweden)

    Nathanael Lauster

    2010-01-01

    Full Text Available I argue that cultural processes linked to the demographic transition produce new density-dependent fertility dynamics. In particular, childbearing becomes dependent upon residential roominess. This relationship is culturally specific, and I argue that the cultural nature of this relationship means that professional and managerial classes are likely to be particularly influenced by residential roominess, while immigrants are less likely to be influenced. I test hypotheses linking residential roominess to the presence of an “own infant” in the household using census data from the Austria, Greece, Portugal, Spain, and the United States. Roominess predicts fertility in all countries, but to differing degrees.

  16. Watching excitons move: the time-dependent transition density matrix

    Science.gov (United States)

    Ullrich, Carsten

    2012-02-01

    Time-dependent density-functional theory allows one to calculate excitation energies and the associated transition densities in principle exactly. The transition density matrix (TDM) provides additional information on electron-hole localization and coherence of specific excitations of the many-body system. We have extended the TDM concept into the real-time domain in order to visualize the excited-state dynamics in conjugated molecules. The time-dependent TDM is defined as an implicit density functional, and can be approximately obtained from the time-dependent Kohn-Sham orbitals. The quality of this approximation is assessed in simple model systems. A computational scheme for real molecular systems is presented: the time-dependent Kohn-Sham equations are solved with the OCTOPUS code and the time-dependent Kohn-Sham TDM is calculated using a spatial partitioning scheme. The method is applied to show in real time how locally created electron-hole pairs spread out over neighboring conjugated molecular chains. The coupling mechanism, electron-hole coherence, and the possibility of charge separation are discussed.

  17. Benchmarks for electronically excited states: Time-dependent density functional theory and density functional theory based multireference configuration interaction

    DEFF Research Database (Denmark)

    Silva-Junior, Mario R.; Schreiber, Marko; Sauer, Stephan P. A.

    2008-01-01

    Time-dependent density functional theory (TD-DFT) and DFT-based multireference configuration interaction (DFT/MRCI) calculations are reported for a recently proposed benchmark set of 28 medium-sized organic molecules. Vertical excitation energies, oscillator strengths, and excited-state dipole...

  18. Spatio-temporal dependence of the signaling response in immune-receptor trafficking networks regulated by cell density: a theoretical model.

    Directory of Open Access Journals (Sweden)

    Pilar García-Peñarrubia

    Full Text Available Cell signaling processes involve receptor trafficking through highly connected networks of interacting components. The binding of surface receptors to their specific ligands is a key factor for the control and triggering of signaling pathways. In most experimental systems, ligand concentration and cell density vary within a wide range of values. Dependence of the signal response on cell density is related with the extracellular volume available per cell. This dependence has previously been studied using non-spatial models which assume that signaling components are well mixed and uniformly distributed in a single compartment. In this paper, a mathematical model that shows the influence exerted by cell density on the spatio-temporal evolution of ligands, cell surface receptors, and intracellular signaling molecules is developed. To this end, partial differential equations were used to model ligand and receptor trafficking dynamics through the different domains of the whole system. This enabled us to analyze several interesting features involved with these systems, namely: a how the perturbation caused by the signaling response propagates through the system; b receptor internalization dynamics and how cell density affects the robustness of dose-response curves upon variation of the binding affinity; and c that enhanced correlations between ligand input and system response are obtained under conditions that result in larger perturbations of the equilibrium ligand + surface receptor [Please see text] ligand - receptor complex. Finally, the results are compared with those obtained by considering that the above components are well mixed in a single compartment.

  19. Density dependent hadron field theory

    International Nuclear Information System (INIS)

    Fuchs, C.; Lenske, H.; Wolter, H.H.

    1995-01-01

    A fully covariant approach to a density dependent hadron field theory is presented. The relation between in-medium NN interactions and field-theoretical meson-nucleon vertices is discussed. The medium dependence of nuclear interactions is described by a functional dependence of the meson-nucleon vertices on the baryon field operators. As a consequence, the Euler-Lagrange equations lead to baryon rearrangement self-energies which are not obtained when only a parametric dependence of the vertices on the density is assumed. It is shown that the approach is energy-momentum conserving and thermodynamically consistent. Solutions of the field equations are studied in the mean-field approximation. Descriptions of the medium dependence in terms of the baryon scalar and vector density are investigated. Applications to infinite nuclear matter and finite nuclei are discussed. Density dependent coupling constants obtained from Dirac-Brueckner calculations with the Bonn NN potentials are used. Results from Hartree calculations for energy spectra, binding energies, and charge density distributions of 16 O, 40,48 Ca, and 208 Pb are presented. Comparisons to data strongly support the importance of rearrangement in a relativistic density dependent field theory. Most striking is the simultaneous improvement of charge radii, charge densities, and binding energies. The results indicate the appearance of a new ''Coester line'' in the nuclear matter equation of state

  20. Density of interface states, excess capacitance and series resistance in the metal-insulator-semiconductor (MIS) solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Altindal, Semsettin; Tataroglu, Adem; Dokme, Ilbilge [Faculty of Arts and Sciences, Physics Department, Gazi University, 06500, Ankara (Turkey)

    2005-01-31

    Dark and illuminated current-voltage (I-V) characteristics of Al/SiO{sub x}/p-Si metal-insulator-semiconductor (MIS) solar cells were measured at room temperature. In addition to capacitance-voltage (C-V) and conductance-voltage (G-V), characteristics are studied at a wide frequency range of 1kHz-10MHz. The dark I-V characteristics showed non-ideal behavior with an ideal factor of 3.2. The density of interface states distribution profiles as a function of (E{sub ss}-E{sub v}) deduced from the I-V measurements at room temperature for the MIS solar cells on the order of 10{sup 13}cm{sup -2}eV{sup -1}. These interface states were responsible for the non-ideal behavior of I-V, C-V and G-V characteristics. Frequency dispersion in capacitance for MIS solar cells can be interpreted only in terms of interface states. The interface states can follow the a.c. signal and yield an excess capacitance, which depends on the relaxation time of interface states and the frequency of the a.c. signal. It was observed that the excess capacitance C{sub o} caused by an interface state decreases with an increase of frequency. The capacitances characteristics of MIS solar cells are affected not only in interface states but also series resistance. Analysis of this data indicated that the high interface states and series resistance leads to lower values of open-circuit voltage, short-circuit current density, and fill factor. Experimental results show that the location of interface states and series resistance have a significant effect on I-V, C-V and G-V characteristics.

  1. Measuring single-cell density.

    Science.gov (United States)

    Grover, William H; Bryan, Andrea K; Diez-Silva, Monica; Suresh, Subra; Higgins, John M; Manalis, Scott R

    2011-07-05

    We have used a microfluidic mass sensor to measure the density of single living cells. By weighing each cell in two fluids of different densities, our technique measures the single-cell mass, volume, and density of approximately 500 cells per hour with a density precision of 0.001 g mL(-1). We observe that the intrinsic cell-to-cell variation in density is nearly 100-fold smaller than the mass or volume variation. As a result, we can measure changes in cell density indicative of cellular processes that would be otherwise undetectable by mass or volume measurements. Here, we demonstrate this with four examples: identifying Plasmodium falciparum malaria-infected erythrocytes in a culture, distinguishing transfused blood cells from a patient's own blood, identifying irreversibly sickled cells in a sickle cell patient, and identifying leukemia cells in the early stages of responding to a drug treatment. These demonstrations suggest that the ability to measure single-cell density will provide valuable insights into cell state for a wide range of biological processes.

  2. Local density approximation for exchange in excited-state density functional theory

    OpenAIRE

    Harbola, Manoj K.; Samal, Prasanjit

    2004-01-01

    Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies.

  3. Density-dependent phonoriton states in highly excited semiconductors

    International Nuclear Information System (INIS)

    Nguyen Hong Quang; Nguyen Minh Khue; Nguyen Que Huong

    1995-09-01

    The dynamical aspects of the phonoriton state in highly-photoexcited semiconductors is studied theoretically. The effect of the exciton-exciton interaction and nonbosonic character of high-density excitons are taken into account. Using Green's function method and within the Random Phase Approximation it is shown that the phonoriton dispersion and damping are very sensitive to the exciton density, characterizing the excitation degree of semiconductors. (author). 18 refs, 3 figs

  4. Specific immunotherapy modifies allergen-specific CD4+ T cell responses in an epitope-dependent manner

    Science.gov (United States)

    Wambre, Erik; DeLong, Jonathan H.; James, Eddie A.; Torres-Chinn, Nadia; Pfützner, Wolfgang; Möbs, Christian; Durham, Stephen R.; Till, Stephen J.; Robinson, David; Kwok, William W.

    2014-01-01

    Background Understanding the mechanisms by which the immune system induces and controls allergic inflammation at the T cell epitope level is critical for the design of new allergy vaccine strategies. Objective To characterize allergen-specific T cell responses linked with allergy or peripheral tolerance and to determine how CD4+ T cell responses to individual allergen-derived epitopes change over allergen-specific immunotherapy (ASIT). Methods Timothy grass pollen (TGP) allergy was used as a model for studying grass pollen allergies. The breadth, magnitude, epitope hierarchy and phenotype of the DR04:01-restricted TGP-specific T cell responses in ten grass pollen allergic, five non-atopic and six allergy vaccine-treated individuals was determined using an ex vivo pMHCII-tetramer approach. Results CD4+ T cells in allergic individuals are directed to a broad range of TGP epitopes characterized by defined immunodominance hierarchy patterns and with distinct functional profiles that depend on the epitope recognized. Epitopes that are restricted specifically to either TH2 or TH1/TR1 responses were identified. ASIT was associated with preferential deletion of allergen-specific TH2 cells and without significant change in frequency of TH1/TR1 cells. Conclusions Preferential allergen-specific TH2-cells deletion after repeated high doses antigen stimulation can be another independent mechanism to restore tolerance to allergen during immunotherapy. PMID:24373351

  5. Time dependentdensity functional theory characterization of organic dyes for dye-sensitized solar cells

    KAUST Repository

    Hilal, Rifaat; Aziz, Saadullah G.; Osman, Osman I.; Bredas, Jean-Luc

    2017-01-01

    We aim at providing better insight into the parameters that govern the intramolecular charge transfer (ICT) and photo-injection processes in dyes for dye-sensitised solar cells (DSSC). Density functional theory (DFT) and time-dependent DFT (TD

  6. Allergen-specific Th1 cells counteract efferent Th2 cell-dependent bronchial hyperresponsiveness and eosinophilic inflammation partly via IFN-gamma.

    Science.gov (United States)

    Huang, T J; MacAry, P A; Eynott, P; Moussavi, A; Daniel, K C; Askenase, P W; Kemeny, D M; Chung, K F

    2001-01-01

    Th2 T cell immune-driven inflammation plays an important role in allergic asthma. We studied the effect of counterbalancing Th1 T cells in an asthma model in Brown Norway rats that favors Th2 responses. Rats received i.v. transfers of syngeneic allergen-specific Th1 or Th2 cells, 24 h before aerosol exposure to allergen, and were studied 18-24 h later. Adoptive transfer of OVA-specific Th2 cells, but not Th1 cells, and OVA, but not BSA exposure, induced bronchial hyperresponsiveness (BHR) to acetylcholine and eosinophilia in a cell number-dependent manner. Importantly, cotransfer of OVA-specific Th1 cells dose-dependently reversed BHR and bronchoalveolar lavage (BAL) eosinophilia, but not mucosal eosinophilia. OVA-specific Th1 cells transferred alone induced mucosal eosinophilia, but neither BHR nor BAL eosinophilia. Th1 suppression of BHR and BAL eosinophilia was allergen specific, since cotransfer of BSA-specific Th1 cells with the OVA-specific Th2 cells was not inhibitory when OVA aerosol alone was used, but was suppressive with OVA and BSA challenge. Furthermore, recipients of Th1 cells alone had increased gene expression for IFN-gamma in the lungs, while those receiving Th2 cells alone showed increased IL-4 mRNA. Importantly, induction of these Th2 cytokines was inhibited in recipients of combined Th1 and Th2 cells. Anti-IFN-gamma treatment attenuated the down-regulatory effect of Th1 cells. Allergen-specific Th1 cells down-regulate efferent Th2 cytokine-dependent BHR and BAL eosinophilia in an asthma model via mechanisms that depend on IFN-gamma. Therapy designed to control the efferent phase of established asthma by augmenting down-regulatory Th1 counterbalancing mechanisms should be effective.

  7. Levels of high-density lipoprotein cholesterol (HDL-C among children with steady-state sickle cell disease

    Directory of Open Access Journals (Sweden)

    Seixas Magda O

    2010-08-01

    Full Text Available Abstract Background The search for sickle cell disease (SCD prognosis biomarkers is a challenge. These markers identification can help to establish further therapy, later severe clinical complications and with patients follow-up. We attempted to study a possible involvement of levels of high-density lipoprotein cholesterol (HDL-C in steady-state children with SCD, once that this lipid marker has been correlated with anti-inflammatory, anti-oxidative, anti-aggregation, anti-coagulant and pro-fibrinolytic activities, important aspects to be considered in sickle cell disease pathogenesis. Methods We prospectively analyzed biochemical, inflammatory and hematological biomarkers of 152 steady-state infants with SCD and 132 healthy subjects using immunochemistry, immunoassay and electronic cell counter respectively. Clinical data were collected from patient medical records. Results Of the 152 infants investigated had a significant positive association of high-density lipoprotein cholesterol with hemoglobin (P Conclusions We hypothesize that some SCD patients can have a specific dyslipidemic subphenotype characterized by low HDL-C with hypertriglyceridemia and high VLDL-C in association with other biomarkers, including those related to inflammation. This represents an important step toward a more reliable clinical prognosis. Additional studies are warranted to test this hypothesis and the probably mechanisms involved in this complex network of markers and their role in SCD pathogenesis.

  8. Cells determine cell density using a small protein bound to a unique tissue-specific phospholipid

    Directory of Open Access Journals (Sweden)

    Christopher J. Petzold

    2013-10-01

    Full Text Available Cell density is the critical parameter controlling tendon morphogenesis. Knowing its neighbors allows a cell to regulate correctly its proliferation and collagen production. A missing link to understanding this process is a molecular description of the sensing mechanism. Previously, this mechanism was shown in cell culture to rely on a diffusible factor (SNZR [sensor] with an affinity for the cell layer. This led to purifying conditioned medium over 4 columns and analyzing the final column fractions for band intensity on SDS gels versus biological activity – a 16 kD band strongly correlated between assays. N-terminal sequencing – EPLAVVDL – identified a large gene (424 AA, extremely conserved between chicken and human. In this paper we probe whether this is the correct gene. Can the predicted large protein be cleaved to a smaller protein? EPLAVVDL occurs towards the C-terminus and cleavage would create a small 94 AA protein. This protein would run at ∼10 kD, so what modifications or cofactor binding accounts for its running at 16 kD on SDS gels? This protein has no prominent hydrophobic regions, so can it be secreted? To validate its role, the chicken cDNA for this gene was tagged with myc and his and transfected into a human osteosarcoma cell line (U2OS. U2OS cells expressed the gene but not passively: differentiating into structures resembling spongy bone and expressing alkaline phosphatase, an early bone marker. Intracellularly, two bands were observed by Western blotting: the full length protein and a smaller form (26 kD. Outside the cell, a small band (28 kD was detected, although it was 40% larger than expected, as well as multiple larger bands. These larger forms could be converted to the predicted smaller protein (94 AA + tags by changing salt concentrations and ultrafiltering – releasing a cofactor to the filtrate while leaving a protein factor in the retentate. Using specific degradative enzymes and mass spectrometry, the

  9. On the density of states of disordered epitaxial graphene

    International Nuclear Information System (INIS)

    Davydov, S. Yu.

    2015-01-01

    The study is concerned with two types of disordered epitaxial graphene: (i) graphene with randomly located carbon vacancies and (ii) structurally amorphous graphene. The former type is considered in the coherent potential approximation, and for the latter type, a model of the density of states is proposed. The effects of two types of substrates, specifically, metal and semiconductor substrates are taken into account. The specific features of the density of states of epitaxial graphene at the Dirac point and the edges of the continuous spectrum are analyzed. It is shown that vacancies in epitaxial graphene formed on the metal substrate bring about logarithmic nulling of the density of states of graphene at the Dirac point and the edges of the continuous spectrum. If the Dirac point corresponds to the middle of the band gap of the semiconductor substrate, the linear trend of the density of states to zero in the vicinity of the Dirac point in defect-free graphene transforms into a logarithmic decrease in the presence of vacancies. In both cases, the graphene-substrate interaction is assumed to be weak (quasi-free graphene). In the study of amorphous epitaxial graphene, a simple model of free amorphous graphene is proposed as the initial model, in which account is taken of the nonzero density of states at the Dirac point, and then the interaction of the graphene sheet with the substrate is taken into consideration. It is shown that, near the Dirac point, the quadratic behavior of the density of states of free amorphous graphene transforms into a linear dependence for amorphous epitaxial graphene. In the study, the density of states of free graphene corresponds to the low-energy approximation of the electron spectrum

  10. Time dependentdensity functional theory characterization of organic dyes for dye-sensitized solar cells

    KAUST Repository

    Hilal, Rifaat

    2017-06-19

    We aim at providing better insight into the parameters that govern the intramolecular charge transfer (ICT) and photo-injection processes in dyes for dye-sensitised solar cells (DSSC). Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations are utilized to study the geometry, electronic structure, electrostatic potential (ESP) and absorption spectrum, for a representative donor-π bridge-acceptor (D–π–A) dye for DSSC. The coplanar geometry of the dye (D1) facilitates strong conjugation and considerable delocalization originating the π CT interaction from donor to acceptor orbitals and the hyper-conjugative interactions involving Rydberg states. A model simulating the adsorption of the dye on the TiO surface is utilized to estimate binding energies. The effect of fluorine substituents in the π-spacer on the quantum efficiency of DSSCs was investigated. Gibb’s free energy values, redox potentials, excited state lifetime, non-linear optical properties (NLO) and driving forces for D1 and its fluorinated derivatives were computed.

  11. Ploidy-dependent changes in the epigenome of symbiotic cells correlate with specific patterns of gene expression

    KAUST Repository

    Nagymihály, Marianna

    2017-04-13

    The formation of symbiotic nodule cells in Medicago truncatula is driven by successive endoreduplication cycles and transcriptional reprogramming in different temporal waves including the activation of more than 600 cysteine-rich NCR genes expressed only in nodules. We show here that the transcriptional waves correlate with growing ploidy levels and have investigated how the epigenome changes during endoreduplication cycles. Differential DNA methylation was found in only a small subset of symbiotic nodule-specific genes, including more than half of the NCR genes, whereas in most genes DNA methylation was unaffected by the ploidy levels and was independent of the genes\\' active or repressed state. On the other hand, expression of nodule-specific genes correlated with ploidy-dependent opening of the chromatin as well as, in a subset of tested genes, with reduced H3K27me3 levels combined with enhanced H3K9ac levels. Our results suggest that endoreduplication-dependent epigenetic changes contribute to transcriptional reprogramming in the differentiation of symbiotic cells.

  12. Density of states functions for photonic crystals

    International Nuclear Information System (INIS)

    McPhedran, R.C.; McOrist, J.; Sterke, C.M. de; Nicorovici, N.A.; Botten, L.C.; Asatryan, A.A.

    2004-01-01

    We discuss density of states functions for photonic crystals, in the context of the two-dimensional problem for arrays of cylinders of arbitrary cross section. We introduce the mutual density of states (MDOS), and show that this function can be used to calculate both the local density of states (LDOS), which gives position information for emission of radiation from photonic crystals, and the spectral density of states (SDOS), which gives angular information. We establish the connection between MDOS, LDOS, SDOS and the conventional density of states, which depends only on frequency. We relate all four functions to the band structure and propagating states within the crystal, and give numerical examples of the relation between band structure and density of states functions

  13. Tissue non-specific alkaline phosphatase production by human dental pulp stromal cells is enhanced by high density cell culture.

    Science.gov (United States)

    Tomlinson, Matthew J; Dennis, Caitriona; Yang, Xuebin B; Kirkham, Jennifer

    2015-08-01

    The cell surface hydrolase tissue non-specific alkaline phosphatase (TNAP) (also known as MSCA-1) is used to identify a sub-population of bone marrow stromal cells (BMSCs) with high mineralising potential and is found on subsets of cells within the dental pulp. We aim to determine whether TNAP is co-expressed by human dental pulp stromal cells (hDPSCs) alongside a range of BMSC markers, whether this is an active form of the enzyme and the effects of culture duration and cell density on its expression. Cells from primary dental pulp and culture expanded hDPSCs expressed TNAP. Subsequent analyses revealed persistent TNAP expression and co-expression with BMSC markers such as CD73 and CD90. Flow cytometry and biochemical assays showed that increased culture durations and cell densities enhanced TNAP expression by hDPSCs. Arresting the hDPSC cell cycle also increased TNAP expression. These data confirm that TNAP is co-expressed by hDPSCs together with other BMSC markers and show that cell density affects TNAP expression levels. We conclude that TNAP is a potentially useful marker for hDPSC selection especially for uses in mineralised tissue regenerative therapies.

  14. Density dependence of line intensities and application to plasma diagnostics

    International Nuclear Information System (INIS)

    Masai, Kuniaki.

    1993-02-01

    Electron density dependence of spectral lines are discussed in view of application to density diagnostics of plasmas. The dependence arises from competitive level population processes, radiative and collisional transitions from the excited states. Results of the measurement on tokamak plasmas are presented to demonstrate the usefulness of line intensity ratios for density diagnostics. Also general characteristics related to density dependence are discussed with atomic-number scaling for H-like and He-like systems to be helpful for application to higher density plasmas. (author)

  15. Tight-binding approximations to time-dependent density functional theory — A fast approach for the calculation of electronically excited states

    Energy Technology Data Exchange (ETDEWEB)

    Rüger, Robert, E-mail: rueger@scm.com [Scientific Computing & Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103 Leipzig (Germany); Lenthe, Erik van [Scientific Computing & Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Heine, Thomas [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103 Leipzig (Germany); Visscher, Lucas [Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)

    2016-05-14

    We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.

  16. Density regulation in Northeast Atlantic fish populations: Density dependence is stronger in recruitment than in somatic growth.

    Science.gov (United States)

    Zimmermann, Fabian; Ricard, Daniel; Heino, Mikko

    2018-05-01

    Population regulation is a central concept in ecology, yet in many cases its presence and the underlying mechanisms are difficult to demonstrate. The current paradigm maintains that marine fish populations are predominantly regulated by density-dependent recruitment. While it is known that density-dependent somatic growth can be present too, its general importance remains unknown and most practical applications neglect it. This study aimed to close this gap by for the first time quantifying and comparing density dependence in growth and recruitment over a large set of fish populations. We fitted density-dependent models to time-series data on population size, recruitment and age-specific weight from commercially exploited fish populations in the Northeast Atlantic Ocean and the Baltic Sea. Data were standardized to enable a direct comparison within and among populations, and estimated parameters were used to quantify the impact of density regulation on population biomass. Statistically significant density dependence in recruitment was detected in a large proportion of populations (70%), whereas for density dependence in somatic growth the prevalence of density dependence depended heavily on the method (26% and 69%). Despite age-dependent variability, the density dependence in recruitment was consistently stronger among age groups and between alternative approaches that use weight-at-age or weight increments to assess growth. Estimates of density-dependent reduction in biomass underlined these results: 97% of populations with statistically significant parameters for growth and recruitment showed a larger impact of density-dependent recruitment on population biomass. The results reaffirm the importance of density-dependent recruitment in marine fishes, yet they also show that density dependence in somatic growth is not uncommon. Furthermore, the results are important from an applied perspective because density dependence in somatic growth affects productivity and

  17. Dependency of a therapy-resistant state of cancer cells on a lipid peroxidase pathway.

    Science.gov (United States)

    Viswanathan, Vasanthi S; Ryan, Matthew J; Dhruv, Harshil D; Gill, Shubhroz; Eichhoff, Ossia M; Seashore-Ludlow, Brinton; Kaffenberger, Samuel D; Eaton, John K; Shimada, Kenichi; Aguirre, Andrew J; Viswanathan, Srinivas R; Chattopadhyay, Shrikanta; Tamayo, Pablo; Yang, Wan Seok; Rees, Matthew G; Chen, Sixun; Boskovic, Zarko V; Javaid, Sarah; Huang, Cherrie; Wu, Xiaoyun; Tseng, Yuen-Yi; Roider, Elisabeth M; Gao, Dong; Cleary, James M; Wolpin, Brian M; Mesirov, Jill P; Haber, Daniel A; Engelman, Jeffrey A; Boehm, Jesse S; Kotz, Joanne D; Hon, Cindy S; Chen, Yu; Hahn, William C; Levesque, Mitchell P; Doench, John G; Berens, Michael E; Shamji, Alykhan F; Clemons, Paul A; Stockwell, Brent R; Schreiber, Stuart L

    2017-07-27

    Plasticity of the cell state has been proposed to drive resistance to multiple classes of cancer therapies, thereby limiting their effectiveness. A high-mesenchymal cell state observed in human tumours and cancer cell lines has been associated with resistance to multiple treatment modalities across diverse cancer lineages, but the mechanistic underpinning for this state has remained incompletely understood. Here we molecularly characterize this therapy-resistant high-mesenchymal cell state in human cancer cell lines and organoids and show that it depends on a druggable lipid-peroxidase pathway that protects against ferroptosis, a non-apoptotic form of cell death induced by the build-up of toxic lipid peroxides. We show that this cell state is characterized by activity of enzymes that promote the synthesis of polyunsaturated lipids. These lipids are the substrates for lipid peroxidation by lipoxygenase enzymes. This lipid metabolism creates a dependency on pathways converging on the phospholipid glutathione peroxidase (GPX4), a selenocysteine-containing enzyme that dissipates lipid peroxides and thereby prevents the iron-mediated reactions of peroxides that induce ferroptotic cell death. Dependency on GPX4 was found to exist across diverse therapy-resistant states characterized by high expression of ZEB1, including epithelial-mesenchymal transition in epithelial-derived carcinomas, TGFβ-mediated therapy-resistance in melanoma, treatment-induced neuroendocrine transdifferentiation in prostate cancer, and sarcomas, which are fixed in a mesenchymal state owing to their cells of origin. We identify vulnerability to ferroptic cell death induced by inhibition of a lipid peroxidase pathway as a feature of therapy-resistant cancer cells across diverse mesenchymal cell-state contexts.

  18. Triplet state photochemistry and the three-state crossing of acetophenone within time-dependent density-functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Huix-Rotllant, Miquel, E-mail: miquel.huix@gmail.com; Ferré, Nicolas, E-mail: nicolas.ferre@univ-amu.fr [Institut de Chimie Radicalaire (UMR-7273), Aix-Marseille Université, CNRS, 13397 Marseille Cedex 20 (France)

    2014-04-07

    Even though time-dependent density-functional theory (TDDFT) works generally well for describing excited states energies and properties in the Franck-Condon region, it can dramatically fail in predicting photochemistry, notably when electronic state crossings occur. Here, we assess the ability of TDDFT to describe the photochemistry of an important class of triplet sensitizers, namely, aromatic ketones. We take acetophenone as a test molecule, for which accurate ab initio results exist in the literature. Triplet acetophenone is generated thanks to an exotic three-state crossing involving one singlet and two triplets states (i.e., a simultaneous intersystem crossing and triplet conical intersection), thus being a stringent test for approximate TDDFT. We show that most exchange-correlation functionals can only give a semi-qualitative picture of the overall photochemistry, in which the three-state crossing is rather represented as a triplet conical intersection separated from the intersystem crossing. The best result overall is given by the double hybrid functional mPW2PLYP, which is even able to reproduce quantitatively the three-state crossing region. We rationalize this results by noting that double hybrid functionals include a larger portion of double excitation character to the excited states.

  19. Escape from the competence state in Streptococcus mutans is governed by the bacterial population density.

    Science.gov (United States)

    Dufour, D; Villemin, C; Perry, J A; Lévesque, C M

    2016-12-01

    Horizontal gene transfer through natural DNA transformation is an important evolutionary mechanism among bacteria. Transformation requires that the bacteria are physiologically competent to take and incorporate free DNA directly from the environment. Although natural genetic transformation is a remarkable feature of many naturally competent bacteria, the process is energetically expensive for the cells. Consequently, a tight control of the competence state is necessary. The objective of the present work was to help decipher the molecular mechanisms regulating the escape from the competence state in Streptococcus mutans, the principal etiological agent responsible for tooth decay in humans. Our results showed that the cessation of competence in S. mutans was abrupt, and did not involve the accumulation of a competence inhibitor nor the depletion of a competence activator in the extracellular environment. The competence state was repressed at high cell population density via concomitant repression of sigX gene encoding the master regulator of the competence regulon. Co-culture experiments performed with oral and non-oral bacteria showed that S. mutans assesses its own population density and also the microbial density of its surroundings to regulate its competence escape. Interestingly, neither the intra-species and extra-species quorum-sensing systems nor the other 13 two-component regulatory systems identified in S. mutans were involved in the cell-density-dependent escape of the competence state. Altogether, our results suggest a complex mechanism regulating the competence shut-off involving cell-density-dependent repression of sigX through an as yet undefined system, and possibly SigX protein stability. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Founder takes all: density-dependent processes structure biodiversity.

    Science.gov (United States)

    Waters, Jonathan M; Fraser, Ceridwen I; Hewitt, Godfrey M

    2013-02-01

    Density-dependent processes play a key role in the spatial structuring of biodiversity. Specifically, interrelated demographic processes, such as gene surfing, high-density blocking, and competitive exclusion, can generate striking geographic contrasts in the distributions of genes and species. Here, we propose that well-studied evolutionary and ecological biogeographic patterns of postglacial recolonization, progressive island colonization, microbial sectoring, and even the 'Out of Africa' pattern of human expansion, are fundamentally similar, underpinned by a 'founder takes all' density-dependent principle. Additionally, we hypothesize that older historic constraints of density-dependent processes are seen today in the dramatic biogeographic shifts that occur in response to human-mediated extinction events, whereby surviving lineages rapidly expand their ranges to replace extinct sister taxa. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Time-dependent density functional theory for multi-component systems

    International Nuclear Information System (INIS)

    Tiecheng Li; Peiqing Tong

    1985-10-01

    The Runge-Gross version of Hohenberg-Kohn-Sham's density functional theory is generalized to multi-component systems, both for arbitrary time-dependent pure states and for arbitrary time-dependent ensembles. (author)

  2. Dependence of cancer cell adhesion kinetics on integrin ligand surface density measured by a high-throughput label-free resonant waveguide grating biosensor.

    Science.gov (United States)

    Orgovan, Norbert; Peter, Beatrix; Bősze, Szilvia; Ramsden, Jeremy J; Szabó, Bálint; Horvath, Robert

    2014-02-07

    A novel high-throughput label-free resonant waveguide grating (RWG) imager biosensor, the Epic® BenchTop (BT), was utilized to determine the dependence of cell spreading kinetics on the average surface density (v(RGD)) of integrin ligand RGD-motifs. v(RGD) was tuned over four orders of magnitude by co-adsorbing the biologically inactive PLL-g-PEG and the RGD-functionalized PLL-g-PEG-RGD synthetic copolymers from their mixed solutions onto the sensor surface. Using highly adherent human cervical tumor (HeLa) cells as a model system, cell adhesion kinetic data of unprecedented quality were obtained. Spreading kinetics were fitted with the logistic equation to obtain the spreading rate constant (r) and the maximum biosensor response (Δλmax), which is assumed to be directly proportional to the maximum spread contact area (Amax). r was found to be independent of the surface density of integrin ligands. In contrast, Δλmax increased with increasing RGD surface density until saturation at high densities. Interpreting the latter behavior with a simple kinetic mass action model, a 2D dissociation constant of 1753 ± 243 μm(-2) (corresponding to a 3D dissociation constant of ~30 μM) was obtained for the binding between RGD-specific integrins embedded in the cell membrane and PLL-g-PEG-RGD. All of these results were obtained completely noninvasively without using any labels.

  3. Stability of the phenotypic reversion of x-ray transformed C3H/10T1/2 cells depends on cellular proliferation after subcultivation at low cell density

    International Nuclear Information System (INIS)

    Brouty-Boye, D.; Gresser, I.; Bandu, M.T.

    1982-01-01

    Reversion from the transformed to the non-transformed phenotype could be obtained by seeding X-ray transformed C3H/10T1/2 cells at low cell density. Cloned revertant cells of varying degrees of reversion were obtained depending on the time they were isolated after one subculture at low cell density. Most of the revertants isolated 7 and 10 days after seeding at very low cell density eventually returned to the transformed phenotype when passaged serially at high cell density. In contrast, 25-35% of the revertants isolated 17-20 days after seeding at low cell density maintained the non-transformed phenotype despite subsequent serial passages at high cell density. The finding that there was a direct relationship between the time during which transformed cells seeded at low cell density multiplied and the number of stable revertant clones obtained, suggests the possibility that reversion from the transformed to the non-transformed phenotype may be a multistep process. Revertant cells displayed a chromosomal pattern characteristic of the transformed cells rather than that of the parental non-transformed 10T1/2 cells. (author)

  4. A mechanistic analysis of density dependence in algal population dynamics

    Directory of Open Access Journals (Sweden)

    Adrian eBorlestean

    2015-04-01

    Full Text Available Population density regulation is a fundamental principle in ecology, but the specific process underlying functional expression of density dependence remains to be fully elucidated. One view contends that patterns of density dependence are largely fixed across a species irrespective of environmental conditions, whereas another is that the strength and expression of density dependence are fundamentally variable depending on the nature of exogenous or endogenous constraints acting on the population. We conducted a study investigating the expression of density dependence in Chlamydomonas spp. grown under a gradient from low to high nutrient density. We predicted that the relationship between per capita growth rate (pgr and population density would vary from concave up to concave down as nutrient density became less limiting and populations experienced weaker density regulation. Contrary to prediction, we found that the relationship between pgr and density became increasingly concave-up as nutrient levels increased. We also found that variation in pgr increased, and pgr levels reached higher maxima in nutrient-limited environments. Most likely, these results are attributable to population growth suppression in environments with high intraspecific competition due to limited nutrient resources. Our results suggest that density regulation is strongly variable depending on exogenous and endogenous processes acting on the population, implying that expression of density dependence depends extensively on local conditions. Additional experimental work should reveal the mechanisms influencing how the expression of density dependence varies across populations through space and time.

  5. Time dependent density matrix theory and effective interaction

    Energy Technology Data Exchange (ETDEWEB)

    Tohyama, Mitsuru [Kyorin Univ., Mitaka, Tokyo (Japan). School of Medicine

    1998-07-01

    A correlated ground state of {sup 16}O and an E2 giant resonance built on it are calculated using an extended version of the time-dependent Hartree-Fock theory called the time-dependent density-matrix theory (TDDM). The Skyrme force is used in the calculation of both a mean field and two-body correlations. It is found that TDDM gives reasonable ground-state correlations and a large spreading width of the E2 giant resonance when single-particle states in the continuum are treated appropriately. (author)

  6. Cell Type-Specific Manipulation with GFP-Dependent Cre Recombinase

    Science.gov (United States)

    Tang, Jonathan C Y; Rudolph, Stephanie; Dhande, Onkar S; Abraira, Victoria E; Choi, Seungwon; Lapan, Sylvain; Drew, Iain R; Drokhlyansky, Eugene; Huberman, Andrew D; Regehr, Wade G; Cepko, Constance L

    2016-01-01

    Summary There are many transgenic GFP reporter lines that allow visualization of specific populations of cells. Using such lines for functional studies requires a method that transforms GFP into a molecule that enables genetic manipulation. Here we report the creation of a method that exploits GFP for gene manipulation, Cre Recombinase Dependent on GFP (CRE-DOG), a split component system that uses GFP and its derivatives to directly induce Cre/loxP recombination. Using plasmid electroporation and AAV viral vectors, we delivered CRE-DOG to multiple GFP mouse lines, leading to effective recombination selectively in GFP-labeled cells. Further, CRE-DOG enabled optogenetic control of these neurons. Beyond providing a new set of tools for manipulation of gene expression selectively in GFP+ cells, we demonstrate that GFP can be used to reconstitute the activity of a protein not known to have a modular structure, suggesting that this strategy might be applicable to a wide range of proteins. PMID:26258682

  7. Evaluating effect of surface state density at the interfaces in degraded bulk heterojunction organic solar cell

    International Nuclear Information System (INIS)

    Arora, Swati; Singh, Vinamrita; Arora, Manoj; Pal Tandon, Ram

    2012-01-01

    Degradation and short shelf life have been observed experimentally in poly(3-hexylthiophene) (P3HT): 6,6-phenyl C61-butyric acid methyl ester (PCBM) based blend solar cells. Both dark and illuminated current-voltage characteristics could be explained quantitatively with a proposed single model for a typical degraded organic solar cell-glass/ITO/PEDOT:PSS/P3HT:PCBM/Al. It has been found that surface state density, interface thickness, tunneling coefficient and occupation probabilities of the interface states becomes important with the passage of time. To look into the problem the activity at ITO/PEDOT:PSS and P3HT:PCBM/Al interfaces are studied using realistic values of the interfaces. The experimental J-V characteristics is well explained with the inclusion of tunneling current through these surface states and becomes the dominant current component for the degraded cell. It is also found that surface state density increases to 10 12 -10 13 cm -2 eV -1 , which has been verified with C-V measurements and also is in agreement with our proposed model for BHJ solar cell after 150 h of fabrication.

  8. Evaluating effect of surface state density at the interfaces in degraded bulk heterojunction organic solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Arora, Swati, E-mail: drswatia@yahoo.com [Department of Physics, Zakir Husain College, University of Delhi, Delhi 110002 (India); Singh, Vinamrita [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Arora, Manoj [Department of Physics, Ramjas College, University of Delhi, Delhi 110007 (India); Pal Tandon, Ram [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2012-08-01

    Degradation and short shelf life have been observed experimentally in poly(3-hexylthiophene) (P3HT): 6,6-phenyl C61-butyric acid methyl ester (PCBM) based blend solar cells. Both dark and illuminated current-voltage characteristics could be explained quantitatively with a proposed single model for a typical degraded organic solar cell-glass/ITO/PEDOT:PSS/P3HT:PCBM/Al. It has been found that surface state density, interface thickness, tunneling coefficient and occupation probabilities of the interface states becomes important with the passage of time. To look into the problem the activity at ITO/PEDOT:PSS and P3HT:PCBM/Al interfaces are studied using realistic values of the interfaces. The experimental J-V characteristics is well explained with the inclusion of tunneling current through these surface states and becomes the dominant current component for the degraded cell. It is also found that surface state density increases to 10{sup 12}-10{sup 13} cm{sup -2} eV{sup -1}, which has been verified with C-V measurements and also is in agreement with our proposed model for BHJ solar cell after 150 h of fabrication.

  9. Density of states and tunneling characteristics of layered superconductors

    International Nuclear Information System (INIS)

    Liu, S.H.; Klemm, R.A.

    1993-04-01

    We have studied the structure of the density-of-states (DOS) curves and tunneling characteristics of layered superconductors with two distinct layers in a unit cell. In general, the peaks of the DOS curves do not correspond to energy gaps of each layer, but depend on the gaps and the interlayer hopping strengths in a complex manner. This makes the interpretation of tunneling data of layered superconductors much less straightforward than isotropic superconductors. Our simulated tunneling characteristics bear certain resemblance to experimental results

  10. Identifying States along the Hematopoietic Stem Cell Differentiation Hierarchy with Single Cell Specificity via Raman Spectroscopy.

    Science.gov (United States)

    Ilin, Yelena; Choi, Ji Sun; Harley, Brendan A C; Kraft, Mary L

    2015-11-17

    A major challenge for expanding specific types of hematopoietic cells ex vivo for the treatment of blood cell pathologies is identifying the combinations of cellular and matrix cues that direct hematopoietic stem cells (HSC) to self-renew or differentiate into cell populations ex vivo. Microscale screening platforms enable minimizing the number of rare HSCs required to screen the effects of numerous cues on HSC fate decisions. These platforms create a strong demand for label-free methods that accurately identify the fate decisions of individual hematopoietic cells at specific locations on the platform. We demonstrate the capacity to identify discrete cells along the HSC differentiation hierarchy via multivariate analysis of Raman spectra. Notably, cell state identification is accurate for individual cells and independent of the biophysical properties of the functionalized polyacrylamide gels upon which these cells are cultured. We report partial least-squares discriminant analysis (PLS-DA) models of single cell Raman spectra enable identifying four dissimilar hematopoietic cell populations across the HSC lineage specification. Successful discrimination was obtained for a population enriched for long-term repopulating HSCs (LT-HSCs) versus their more differentiated progeny, including closely related short-term repopulating HSCs (ST-HSCs) and fully differentiated lymphoid (B cells) and myeloid (granulocytes) cells. The lineage-specific differentiation states of cells from these four subpopulations were accurately identified independent of the stiffness of the underlying biomaterial substrate, indicating subtle spectral variations that discriminated these populations were not masked by features from the culture substrate. This approach enables identifying the lineage-specific differentiation stages of hematopoietic cells on biomaterial substrates of differing composition and may facilitate correlating hematopoietic cell fate decisions with the extrinsic cues that

  11. Nonspherical atomic ground-state densities and chemical deformation densities from x-ray scattering

    International Nuclear Information System (INIS)

    Ruedenberg, K.; Schwarz, W.H.E.

    1990-01-01

    Presuming that chemical insight can be gained from the difference between the molecular electron density and the superposition of the ground-state densities of the atoms in a molecule, it is pointed out that, for atoms with degenerate ground states, an unpromoted ''atom in a molecule'' is represented by a specific ensemble of the degenerate atomic ground-state wave functions and that this ensemble is determined by the anisotropic local surroundings. The resulting atomic density contributions are termed oriented ground state densities, and the corresponding density difference is called the chemical deformation density. The constraints implied by this conceptual approach for the atomic density contributions are formulated and a method is developed for determining them from x-ray scattering data. The electron density of the appropriate promolecule and its x-ray scattering are derived, the determination of the parameters of the promolecule is outlined, and the chemical deformation density is formulated

  12. Carrier-density dependence of photoluminescence from localized states in InGaN/GaN quantum wells in nanocolumns and a thin film

    Energy Technology Data Exchange (ETDEWEB)

    Shimosako, N., E-mail: n-shimosako@sophia.jp; Inose, Y.; Satoh, H.; Kinjo, K.; Nakaoka, T.; Oto, T. [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Kishino, K.; Ema, K. [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Sophia Nanotechnology Research Center, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2015-11-07

    We have measured and analyzed the carrier-density dependence of photoluminescence (PL) spectra and the PL efficiency of InGaN/GaN multiple quantum wells in nanocolumns and in a thin film over a wide excitation range. The localized states parameters, such as the tailing parameter, density and size of the localized states, and the mobility edge density are estimated. The spectral change and reduction of PL efficiency are explained by filling of the localized states and population into the extended states around the mobility edge density. We have also found that the nanocolumns have a narrower distribution of the localized states and a higher PL efficiency than those of the film sample although the In composition of the nanocolumns is higher than that of the film.

  13. Cell-substrate interaction with cell-membrane-stress dependent adhesion.

    Science.gov (United States)

    Jiang, H; Yang, B

    2012-01-10

    Cell-substrate interaction is examined in a two-dimensional mechanics model. The cell and substrate are treated as a shell and an elastic solid, respectively. Their interaction through adhesion is treated using nonlinear springs. Compared to previous cell mechanics models, the present model introduces a cohesive force law that is dependent not only on cell-substrate distance but also on internal cell-membrane stress. It is postulated that a living cell would establish focal adhesion sites with density dependent on the cell-membrane stress. The formulated mechanics problem is numerically solved using coupled finite elements and boundary elements for the cell and the substrate, respectively. The nodes in the adhesion zone from either side are linked by the cohesive springs. The specific cases of a cell adhering to a homogeneous substrate and a heterogeneous bimaterial substrate are examined. The analyses show that the substrate stiffness affects the adhesion behavior significantly and regulates the direction of cell adhesion, in good agreement with the experimental results in the literature. By introducing a reactive parameter (i.e., cell-membrane stress) linking biological responses of a living cell to a mechanical environment, the present model offers a unified mechanistic vehicle for characterization and prediction of living cell responses to various kinds of mechanical stimuli including local extracellular matrix and neighboring cells. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Density-dependent squeezing of excitons in highly excited semiconductors

    International Nuclear Information System (INIS)

    Nguyen Hong Quang.

    1995-07-01

    The time evolution from coherent states to squeezed states of high density excitons is studied theoretically based on the boson formalism and within the Random Phase Approximation. Both the mutual interaction between excitons and the anharmonic exciton-photon interaction due to phase-space filling of excitons are taken into account. It is shown that the exciton squeezing depends strongly on the exciton density in semiconductors and becomes smaller with increasing the latter. (author). 16 refs, 2 figs

  15. Rydberg energies using excited state density functional theory

    International Nuclear Information System (INIS)

    Cheng, C.-L.; Wu Qin; Van Voorhis, Troy

    2008-01-01

    We utilize excited state density functional theory (eDFT) to study Rydberg states in atoms. We show both analytically and numerically that semilocal functionals can give quite reasonable Rydberg energies from eDFT, even in cases where time dependent density functional theory (TDDFT) fails catastrophically. We trace these findings to the fact that in eDFT the Kohn-Sham potential for each state is computed using the appropriate excited state density. Unlike the ground state potential, which typically falls off exponentially, the sequence of excited state potentials has a component that falls off polynomially with distance, leading to a Rydberg-type series. We also address the rigorous basis of eDFT for these systems. Perdew and Levy have shown using the constrained search formalism that every stationary density corresponds, in principle, to an exact stationary state of the full many-body Hamiltonian. In the present context, this means that the excited state DFT solutions are rigorous as long as they deliver the minimum noninteracting kinetic energy for the given density. We use optimized effective potential techniques to show that, in some cases, the eDFT Rydberg solutions appear to deliver the minimum kinetic energy because the associated density is not pure state v-representable. We thus find that eDFT plays a complementary role to constrained DFT: The former works only if the excited state density is not the ground state of some potential while the latter applies only when the density is a ground state density.

  16. Density of Ni-Cr Alloy in the Mushy State

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The density of Ni-Cr alloy in the mushy state has been measured using the modified sessile drop method. The density of Ni-Cr alloy in the mushy state was found to decrease with increasing temperature and Cr concentration in alloy.The molar volume of Ni-Cr alloy in the mushy state therefore increases with increasing the Cr concentration in alloy.The ratio of the difference of density divided by the temperature difference between liquidus and solidus temperatures decreases with increasing Cr concentration. The density of the alloy increased with the precipitation of a solid phase in alloy during the solidification process. The temperature dependence of the density of alloy in the mushy state was not linear but biquadratic.

  17. Excited states of ReO4-: A comprehensive time-dependent relativistic density functional theory study

    Science.gov (United States)

    Xu, Wenhua; Ma, Jianyi; Peng, Daoling; Zou, Wenli; Liu, Wenjian; Staemmler, Volker

    2009-02-01

    The perrhenate anion, ReO4-, is taken as a showcase of heavy transition metal complexes, to examine the performance of time-dependent relativistic density functional linear response theory for electronic excitations, which is based on a newly proposed exact two-component Hamiltonian resulting from the symmetrized elimination of the small component. In total 30 scalar and 63 spinor excited states are investigated and the results are grossly in good agreement with those by the singles and doubles coupled-cluster linear response theory. It is found that only a few scalar states of 3T1 and 3T2 symmetries are split significantly by the spin-orbit coupling, whereas only those excited states involving the Rydberg-type virtual orbital are affected by the solvent effects. The nature of the optical absorption spectra is also highlighted.

  18. Excited states of ReO4-: A comprehensive time-dependent relativistic density functional theory study

    International Nuclear Information System (INIS)

    Xu Wenhua; Ma Jianyi; Peng Daoling; Zou Wenli; Liu Wenjian; Staemmler, Volker

    2009-01-01

    The perrhenate anion, ReO 4 - , is taken as a showcase of heavy transition metal complexes, to examine the performance of time-dependent relativistic density functional linear response theory for electronic excitations, which is based on a newly proposed exact two-component Hamiltonian resulting from the symmetrized elimination of the small component. In total 30 scalar and 63 spinor excited states are investigated and the results are grossly in good agreement with those by the singles and doubles coupled-cluster linear response theory. It is found that only a few scalar states of 3 T 1 and 3 T 2 symmetries are split significantly by the spin-orbit coupling, whereas only those excited states involving the Rydberg-type virtual orbital are affected by the solvent effects. The nature of the optical absorption spectra is also highlighted

  19. Excited state nuclear forces from the Tamm-Dancoff approximation to time-dependent density functional theory within the plane wave basis set framework

    Science.gov (United States)

    Hutter, Jürg

    2003-03-01

    An efficient formulation of time-dependent linear response density functional theory for the use within the plane wave basis set framework is presented. The method avoids the transformation of the Kohn-Sham matrix into the canonical basis and references virtual orbitals only through a projection operator. Using a Lagrangian formulation nuclear derivatives of excited state energies within the Tamm-Dancoff approximation are derived. The algorithms were implemented into a pseudo potential/plane wave code and applied to the calculation of adiabatic excitation energies, optimized geometries and vibrational frequencies of three low lying states of formaldehyde. An overall good agreement with other time-dependent density functional calculations, multireference configuration interaction calculations and experimental data was found.

  20. Effect of monocular deprivation on rabbit neural retinal cell densities

    Directory of Open Access Journals (Sweden)

    Philip Maseghe Mwachaka

    2015-01-01

    Conclusion: In this rabbit model, monocular deprivation resulted in activity-dependent changes in cell densities of the neural retina in favour of the non-deprived eye along with reduced cell densities in the deprived eye.

  1. Communication: Orbital instabilities and triplet states from time-dependent density functional theory and long-range corrected functionals

    Science.gov (United States)

    Sears, John S.; Koerzdoerfer, Thomas; Zhang, Cai-Rong; Brédas, Jean-Luc

    2011-10-01

    Long-range corrected hybrids represent an increasingly popular class of functionals for density functional theory (DFT) that have proven to be very successful for a wide range of chemical applications. In this Communication, we examine the performance of these functionals for time-dependent (TD)DFT descriptions of triplet excited states. Our results reveal that the triplet energies are particularly sensitive to the range-separation parameter; this sensitivity can be traced back to triplet instabilities in the ground state coming from the large effective amounts of Hartree-Fock exchange included in these functionals. As such, the use of standard long-range corrected functionals for the description of triplet states at the TDDFT level is not recommended.

  2. Density-dependent intraspecific aggression regulates survival in northern Yellowstone wolves (Canis lupus).

    Science.gov (United States)

    Cubaynes, Sarah; MacNulty, Daniel R; Stahler, Daniel R; Quimby, Kira A; Smith, Douglas W; Coulson, Tim

    2014-11-01

    Understanding the population dynamics of top-predators is essential to assess their impact on ecosystems and to guide their management. Key to this understanding is identifying the mechanisms regulating vital rates. Determining the influence of density on survival is necessary to understand the extent to which human-caused mortality is compensatory or additive. In wolves (Canis lupus), empirical evidence for density-dependent survival is lacking. Dispersal is considered the principal way in which wolves adjust their numbers to prey supply or compensate for human exploitation. However, studies to date have primarily focused on exploited wolf populations, in which density-dependent mechanisms are likely weak due to artificially low wolf densities. Using 13 years of data on 280 collared wolves in Yellowstone National Park, we assessed the effect of wolf density, prey abundance and population structure, as well as winter severity, on age-specific survival in two areas (prey-rich vs. prey-poor) of the national park. We further analysed cause-specific mortality and explored the factors driving intraspecific aggression in the prey-rich northern area of the park. Overall, survival rates decreased during the study. In northern Yellowstone, density dependence regulated adult survival through an increase in intraspecific aggression, independent of prey availability. In the interior of the park, adult survival was less variable and density-independent, despite reduced prey availability. There was no effect of prey population structure in northern Yellowstone, or of winter severity in either area. Survival was similar among yearlings and adults, but lower for adults older than 6 years. Our results indicate that density-dependent intraspecific aggression is a major driver of adult wolf survival in northern Yellowstone, suggesting intrinsic density-dependent mechanisms have the potential to regulate wolf populations at high ungulate densities. When low prey availability or high

  3. Optical Absorption in Molecular Crystals from Time-Dependent Density Functional Theory

    Science.gov (United States)

    2017-04-23

    Our approach represents a full solid-state calculation, allowing for polarization ef- fects while still capable of capturing inter-molecular dis...AFRL-AFOSR-UK-TR-2017-0030 Optical absorption in molecular crystals from time-dependent density functional theory Leeor Kronik WEIZMANN INSTITUTE OF...from time-dependent density functional theory 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-15-1-0290 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S

  4. Global asymptotic stability of density dependent integral population projection models.

    Science.gov (United States)

    Rebarber, Richard; Tenhumberg, Brigitte; Townley, Stuart

    2012-02-01

    Many stage-structured density dependent populations with a continuum of stages can be naturally modeled using nonlinear integral projection models. In this paper, we study a trichotomy of global stability result for a class of density dependent systems which include a Platte thistle model. Specifically, we identify those systems parameters for which zero is globally asymptotically stable, parameters for which there is a positive asymptotically stable equilibrium, and parameters for which there is no asymptotically stable equilibrium. Copyright © 2011 Elsevier Inc. All rights reserved.

  5. Existence of time-dependent density-functional theory for open electronic systems: time-dependent holographic electron density theorem.

    Science.gov (United States)

    Zheng, Xiao; Yam, ChiYung; Wang, Fan; Chen, GuanHua

    2011-08-28

    We present the time-dependent holographic electron density theorem (TD-HEDT), which lays the foundation of time-dependent density-functional theory (TDDFT) for open electronic systems. For any finite electronic system, the TD-HEDT formally establishes a one-to-one correspondence between the electron density inside any finite subsystem and the time-dependent external potential. As a result, any electronic property of an open system in principle can be determined uniquely by the electron density function inside the open region. Implications of the TD-HEDT on the practicality of TDDFT are also discussed.

  6. Cell density dependence of transformation frequencies in C3H10T1/2 cells exposed to X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Bettega, D; Calzolari, P; Ottolenghi, A; Lombardi, L T [Milan Univ. (Italy). Ist. di Fisica; Rimoldi, E [Milan Univ. (Italy). Ist. di Radiologia Veterinaria

    1989-12-01

    The effects of cell density on transformation frequencies were studied in C3H10T1/2 cells exposed to 0.5 and 7 Gy of 200 kVp X-rays. Initial cell density strongly influenced transformation frequency; this decreased by a factor of between 4 and 10 when the initial seeding density was changed from 50 to 2500 cells/10 cm diameter Petri dish. The data were fitted with two equations: (a) an allometric function represented on a log-log scale by a straight line and (b) a sigmoidal function with plateaux between 50 and 250 cells/dish and above 600. The two curves are compared and their probabilities discussed. Our data indicate that the region between 50 and 250 cells/dish would be the most suitable region for dose-effect measurements. A study of the growth curves at 0.5 and 8.5 Gy shows that cell growth rates are not influenced by initial cell density. (author).

  7. Detection and quantification of subtle changes in red blood cell density using a cell phone.

    Science.gov (United States)

    Felton, Edward J; Velasquez, Anthony; Lu, Shulin; Murphy, Ryann O; ElKhal, Abdala; Mazor, Ofer; Gorelik, Pavel; Sharda, Anish; Ghiran, Ionita C

    2016-08-16

    Magnetic levitation has emerged as a technique that offers the ability to differentiate between cells with different densities. We have developed a magnetic levitation system for this purpose that distinguishes not only different cell types but also density differences in cells of the same type. This small-scale system suspends cells in a paramagnetic medium in a capillary placed between two rare earth magnets, and cells levitate to an equilibrium position determined solely by their density. Uniform reference beads of known density are used in conjunction with the cells as a means to quantify their levitation positions. In one implementation images of the levitating cells are acquired with a microscope, but here we also introduce a cell phone-based device that integrates the magnets, capillary, and a lens into a compact and portable unit that acquires images with the phone's camera. To demonstrate the effectiveness of magnetic levitation in cell density analysis we carried out levitation experiments using red blood cells with artificially altered densities, and also levitated those from donors. We observed that we can distinguish red blood cells of an anemic donor from those that are healthy. Since a plethora of disease states are characterized by changes in cell density magnetic cell levitation promises to be an effective tool in identifying and analyzing pathologic states. Furthermore, the low cost, portability, and ease of use of the cell phone-based system may potentially lead to its deployment in low-resource environments.

  8. Steady state and transient simulation of anion exchange membrane fuel cells

    Science.gov (United States)

    Dekel, Dario R.; Rasin, Igal G.; Page, Miles; Brandon, Simon

    2018-01-01

    We present a new model for anion exchange membrane fuel cells. Validation against experimental polarization curve data is obtained for current densities ranging from zero to above 2 A cm-2. Experimental transient data is also successfully reproduced. The model is very flexible and can be used to explore the system's sensitivity to a wide range of material properties, cell design specifications, and operating parameters. We demonstrate the impact of gas inlet relative humidity (RH), operating current density, ionomer loading and ionomer ion exchange capacity (IEC) values on cell performance. In agreement with the literature, high air RH levels are shown to improve cell performance. At high current densities (>1 A cm-2) this effect is observed to be especially significant. Simulated hydration number distributions across the cell reveal the related critical dependence of cathode hydration on air RH and current density values. When exploring catalyst layer design, optimal intermediate ionomer loading values are demonstrated. The benefits of asymmetric (cathode versus anode) electrode design are revealed, showing enhanced performance using higher cathode IEC levels. Finally, electrochemical reaction profiles across the electrodes uncover inhomogeneous catalyst utilization. Specifically, at high current densities the cathodic reaction is confined to a narrow region near the membrane.

  9. Why Density Dependent Propulsion?

    Science.gov (United States)

    Robertson, Glen A.

    2011-01-01

    In 2004 Khoury and Weltman produced a density dependent cosmology theory they call the Chameleon, as at its nature, it is hidden within known physics. The Chameleon theory has implications to dark matter/energy with universe acceleration properties, which implies a new force mechanism with ties to the far and local density environment. In this paper, the Chameleon Density Model is discussed in terms of propulsion toward new propellant-less engineering methods.

  10. Bistable Epigenetic States Explain Age-Dependent Decline in Mesenchymal Stem Cell Heterogeneity.

    Science.gov (United States)

    Hamidouche, Zahia; Rother, Karen; Przybilla, Jens; Krinner, Axel; Clay, Denis; Hopp, Lydia; Fabian, Claire; Stolzing, Alexandra; Binder, Hans; Charbord, Pierre; Galle, Joerg

    2017-03-01

    The molecular mechanisms by which heterogeneity, a major characteristic of stem cells, is achieved are yet unclear. We here study the expression of the membrane stem cell antigen-1 (Sca-1) in mouse bone marrow mesenchymal stem cell (MSC) clones. We show that subpopulations with varying Sca-1 expression profiles regenerate the Sca-1 profile of the mother population within a few days. However, after extensive replication in vitro, the expression profiles shift to lower values and the regeneration time increases. Study of the promoter of Ly6a unravels that the expression level of Sca-1 is related to the promoter occupancy by the activating histone mark H3K4me3. We demonstrate that these findings can be consistently explained by a computational model that considers positive feedback between promoter H3K4me3 modification and gene transcription. This feedback implicates bistable epigenetic states which the cells occupy with an age-dependent frequency due to persistent histone (de-)modification. Our results provide evidence that MSC heterogeneity, and presumably that of other stem cells, is associated with bistable epigenetic states and suggest that MSCs are subject to permanent state fluctuations. Stem Cells 2017;35:694-704. © The Authors Stem Cells published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.

  11. Population-Level Density Dependence Influences the Origin and Maintenance of Parental Care.

    Science.gov (United States)

    Reyes, Elijah; Thrasher, Patsy; Bonsall, Michael B; Klug, Hope

    2016-01-01

    Parental care is a defining feature of animal breeding systems. We now know that both basic life-history characteristics and ecological factors influence the evolution of care. However, relatively little is known about how these factors interact to influence the origin and maintenance of care. Here, we expand upon previous work and explore the relationship between basic life-history characteristics (stage-specific rates of mortality and maturation) and the fitness benefits associated with the origin and the maintenance of parental care for two broad ecological scenarios: the scenario in which egg survival is density dependent and the case in which adult survival is density dependent. Our findings suggest that high offspring need is likely critical in driving the origin, but not the maintenance, of parental care regardless of whether density dependence acts on egg or adult survival. In general, parental care is more likely to result in greater fitness benefits when baseline adult mortality is low if 1) egg survival is density dependent or 2) adult mortality is density dependent and mutant density is relatively high. When density dependence acts on egg mortality, low rates of egg maturation and high egg densities are less likely to lead to strong fitness benefits of care. However, when density dependence acts on adult mortality, high levels of egg maturation and increasing adult densities are less likely to maintain care. Juvenile survival has relatively little, if any, effect on the origin and maintenance of egg-only care. More generally, our results suggest that the evolution of parental care will be influenced by an organism's entire life history characteristics, the stage at which density dependence acts, and whether care is originating or being maintained.

  12. Pairing correction of particle-hole state densities for two kinds of Fermions

    International Nuclear Information System (INIS)

    Fu, C.Y.

    1985-01-01

    Pairing corrections in particle-hole (exciton) state-density formulas used in precompound nuclear reaction theories are, strictly speaking, dependent on the nuclear excitation energy U and the exciton number n. A general formula for (U,n)-dependent pairing corrections has been derived in an earlier paper for exciton state-density formulas for one kind of Fermion. In the present paper, a similar derivation is made for two kinds of Fermions. It is shown that the constant-pairing-energy correction used in standard level-density formulas, such as U 0 in Gilbert and Cameron, is a limiting case of the present general (U,n)-dependent results

  13. Derivation of the RPA (Random Phase Approximation) Equation of ATDDFT (Adiabatic Time Dependent Density Functional Ground State Response Theory) from an Excited State Variational Approach Based on the Ground State Functional.

    Science.gov (United States)

    Ziegler, Tom; Krykunov, Mykhaylo; Autschbach, Jochen

    2014-09-09

    The random phase approximation (RPA) equation of adiabatic time dependent density functional ground state response theory (ATDDFT) has been used extensively in studies of excited states. It extracts information about excited states from frequency dependent ground state response properties and avoids, thus, in an elegant way, direct Kohn-Sham calculations on excited states in accordance with the status of DFT as a ground state theory. Thus, excitation energies can be found as resonance poles of frequency dependent ground state polarizability from the eigenvalues of the RPA equation. ATDDFT is approximate in that it makes use of a frequency independent energy kernel derived from the ground state functional. It is shown in this study that one can derive the RPA equation of ATDDFT from a purely variational approach in which stationary states above the ground state are located using our constricted variational DFT (CV-DFT) method and the ground state functional. Thus, locating stationary states above the ground state due to one-electron excitations with a ground state functional is completely equivalent to solving the RPA equation of TDDFT employing the same functional. The present study is an extension of a previous work in which we demonstrated the equivalence between ATDDFT and CV-DFT within the Tamm-Dancoff approximation.

  14. Gaussian density matrices: Quantum analogs of classical states

    International Nuclear Information System (INIS)

    Mann, A.; Revzen, M.

    1993-01-01

    We study quantum analogs of clasical situations, i.e. quantum states possessing some specific classical attribute(s). These states seem quite generally, to have the form of gaussian density matrices. Such states can always be parametrized as thermal squeezed states (TSS). We consider the following specific cases: (a) Two beams that are built from initial beams which passed through a beam splitter cannot, classically, be distinguished from (appropriately prepared) two independent beams that did not go through a splitter. The only quantum states possessing this classical attribute are TSS. (b) The classical Cramer's theorem was shown to have a quantum version (Hegerfeldt). Again, the states here are Gaussian density matrices. (c) The special case in the study of the quantum version of Cramer's theorem, viz. when the state obtained after partial tracing is a pure state, leads to the conclusion that all states involved are zero temperature limit TSS. The classical analog here are gaussians of zero width, i.e. all distributions are δ functions in phase space. (orig.)

  15. Induction of apoptosis by Fe(salen)Cl through caspase-dependent pathway specifically in tumor cells.

    Science.gov (United States)

    Pradhan, Nitika; Pratheek, B M; Garai, Antara; Kumar, Ashutosh; Meena, Vikram S; Ghosh, Shyamasree; Singh, Sujay; Kumari, Shikha; Chandrashekar, T K; Goswami, Chandan; Chattopadhyay, Subhasis; Kar, Sanjib; Maiti, Prasanta K

    2014-10-01

    Iron-based compounds possess the capability of inducing cell death due to their reactivity with oxidant molecules, but their specificity towards cancer cells and the mechanism of action are hitherto less investigated. A Fe(salen)Cl derivative has been synthesized that remains active in monomer form. The efficacy of this compound as an anti-tumor agent has been investigated in mouse and human leukemia cell lines. Fe(salen)Cl induces cell death specifically in tumor cells and not in primary cells. Mouse and human T-cell leukemia cell lines, EL4 and Jurkat cells are found to be susceptible to Fe(salen)Cl and undergo apoptosis, but normal mouse spleen cells and human peripheral blood mononuclear cells (PBMC) remain largely unaffected by Fe(salen)Cl. Fe(salen)Cl treated tumor cells show significantly higher expression level of cytochrome c that might have triggered the cascade of reactions leading to apoptosis in cancer cells. A significant loss of mitochondrial membrane potential upon Fe(salen)Cl treatment suggests that Fe(salen)Cl induces apoptosis by disrupting mitochondrial membrane potential and homeostasis, leading to cytotoxity. We also established that apoptosis in the Fe(salen)Cl-treated tumor cells is mediated through caspase-dependent pathway. This is the first report demonstrating that Fe(salen)Cl can specifically target the tumor cells, leaving the primary cells least affected, indicating an excellent potential for this compound to emerge as a next-generation anti-tumor drug. © 2014 International Federation for Cell Biology.

  16. Induction of apoptosis by Fe(salenCl through caspase-dependent pathway specifically in tumor cells

    Directory of Open Access Journals (Sweden)

    Nitika Pradhan

    2017-10-01

    Full Text Available Iron-based compounds possess the capability of inducing cell death due to their reactivity with oxidant molecules, but their specificity towards cancer cells and the mechanism of action are hitherto less investigated. A Fe(salenCl derivative has been synthesized that remains active in monomer form. The efficacy of this compound as an anti-tumor agent has been investigated in mouse and human leukemia cell lines. Fe(salenCl induces cell death specifically in tumor cells and not in primary cells. Mouse and human T-cell leukemia cell lines, EL4 and Jurkat cells are found to be susceptible to Fe(salenCl and undergo apoptosis, but normal mouse spleen cells and human peripheral blood mononuclear cells (PBMC remain largely unaffected by Fe(salenCl. Fe(salenCl treated tumor cells show significantly higher expression level of cytochrome c that might have triggered the cascade of reactions leading to apoptosis in cancer cells. A significant loss of mitochondrial membrane potential upon Fe(salenCl treatment suggests that Fe(salenCl induces apoptosis by disrupting mitochondrial membrane potential and homeostasis, leading to cytotoxity. We also established that apoptosis in the Fe(salenCl-treated tumor cells is mediated through caspase-dependent pathway. This is the first report demonstrating that Fe(salenCl can specifically target the tumor cells, leaving the primary cells least affected, indicating an excellent potential for this compound to emerge as a next-generation anti-tumor drug.

  17. Population-Level Density Dependence Influences the Origin and Maintenance of Parental Care.

    Directory of Open Access Journals (Sweden)

    Elijah Reyes

    Full Text Available Parental care is a defining feature of animal breeding systems. We now know that both basic life-history characteristics and ecological factors influence the evolution of care. However, relatively little is known about how these factors interact to influence the origin and maintenance of care. Here, we expand upon previous work and explore the relationship between basic life-history characteristics (stage-specific rates of mortality and maturation and the fitness benefits associated with the origin and the maintenance of parental care for two broad ecological scenarios: the scenario in which egg survival is density dependent and the case in which adult survival is density dependent. Our findings suggest that high offspring need is likely critical in driving the origin, but not the maintenance, of parental care regardless of whether density dependence acts on egg or adult survival. In general, parental care is more likely to result in greater fitness benefits when baseline adult mortality is low if 1 egg survival is density dependent or 2 adult mortality is density dependent and mutant density is relatively high. When density dependence acts on egg mortality, low rates of egg maturation and high egg densities are less likely to lead to strong fitness benefits of care. However, when density dependence acts on adult mortality, high levels of egg maturation and increasing adult densities are less likely to maintain care. Juvenile survival has relatively little, if any, effect on the origin and maintenance of egg-only care. More generally, our results suggest that the evolution of parental care will be influenced by an organism's entire life history characteristics, the stage at which density dependence acts, and whether care is originating or being maintained.

  18. Incorporation of gene-specific variability improves expression analysis using high-density DNA microarrays

    Directory of Open Access Journals (Sweden)

    Spitznagel Edward

    2003-11-01

    Full Text Available Abstract Background The assessment of data reproducibility is essential for application of microarray technology to exploration of biological pathways and disease states. Technical variability in data analysis largely depends on signal intensity. Within that context, the reproducibility of individual probe sets has not been hitherto addressed. Results We used an extraordinarily large replicate data set derived from human placental trophoblast to analyze probe-specific contribution to variability of gene expression. We found that signal variability, in addition to being signal-intensity dependant, is probe set-specific. Importantly, we developed a novel method to quantify the contribution of this probe set-specific variability. Furthermore, we devised a formula that incorporates a priori-computed, replicate-based information on probe set- and intensity-specific variability in determination of expression changes even without technical replicates. Conclusion The strategy of incorporating probe set-specific variability is superior to analysis based on arbitrary fold-change thresholds. We recommend its incorporation to any computation of gene expression changes using high-density DNA microarrays. A Java application implementing our T-score is available at http://www.sadovsky.wustl.edu/tscore.html.

  19. Influence of linear-energy-dependent density of states on two-band superconductors: Three-square-well model approach

    International Nuclear Information System (INIS)

    Ogbuu, O.A.; Abah, O.C.; Asomba, G.C.; Okoye, C.M.I.

    2011-01-01

    We derived the transition temperature and the isotope exponent of two-band superconductor. We employed Bogoliubov-Valatin formalism assuming a three-square-well potential. The effect of linear-energy-dependent electronic DOS in superconductors is considered. The relevance of the studies to MgB 2 is analyzed. We have derived the expressions for the transition temperature and the isotope effect exponent within the framework of Bogoliubov-Valatin two-band formalism using a linear-energy-dependent electronic density of states assuming a three-square-well potentials model. Our results show that the approach could be used to account for a wide range of values of the transition temperature and isotope effect exponent. The relevance of the present calculations to MgB 2 is analyzed.

  20. Dispersal, density dependence, and population dynamics of a fungal microbe on leaf surfaces.

    Science.gov (United States)

    Woody, Scott T; Ives, Anthony R; Nordheim, Erik V; Andrews, John H

    2007-06-01

    Despite the ubiquity and importance of microbes in nature, little is known about their natural population dynamics, especially for those that occupy terrestrial habitats. Here we investigate the dynamics of the yeast-like fungus Aureobasidium pullulans (Ap) on apple leaves in an orchard. We asked three questions. (1) Is variation in fungal population density among leaves caused by variation in leaf carrying capacities and strong density-dependent population growth that maintains densities near carrying capacity? (2) Do resident populations have competitive advantages over immigrant cells? (3) Do Ap dynamics differ at different times during the growing season? To address these questions, we performed two experiments at different times in the growing season. Both experiments used a 2 x 2 factorial design: treatment 1 removed fungal cells from leaves to reveal density-dependent population growth, and treatment 2 inoculated leaves with an Ap strain engineered to express green fluorescent protein (GFP), which made it possible to track the fate of immigrant cells. The experiments showed that natural populations of Ap vary greatly in density due to sustained differences in carrying capacities among leaves. The maintenance of populations close to carrying capacities indicates strong density-dependent processes. Furthermore, resident populations are strongly competitive against immigrants, while immigrants have little impact on residents. Finally, statistical models showed high population growth rates of resident cells in one experiment but not in the other, suggesting that Ap experiences relatively "good" and "bad" periods for population growth. This picture of Ap dynamics conforms to commonly held, but rarely demonstrated, expectations of microbe dynamics in nature. It also highlights the importance of local processes, as opposed to immigration, in determining the abundance and dynamics of microbes on surfaces in terrestrial systems.

  1. Time-dependent density-functional tight-binding method with the third-order expansion of electron density.

    Science.gov (United States)

    Nishimoto, Yoshio

    2015-09-07

    We develop a formalism for the calculation of excitation energies and excited state gradients for the self-consistent-charge density-functional tight-binding method with the third-order contributions of a Taylor series of the density functional theory energy with respect to the fluctuation of electron density (time-dependent density-functional tight-binding (TD-DFTB3)). The formulation of the excitation energy is based on the existing time-dependent density functional theory and the older TD-DFTB2 formulae. The analytical gradient is computed by solving Z-vector equations, and it requires one to calculate the third-order derivative of the total energy with respect to density matrix elements due to the inclusion of the third-order contributions. The comparison of adiabatic excitation energies for selected small and medium-size molecules using the TD-DFTB2 and TD-DFTB3 methods shows that the inclusion of the third-order contributions does not affect excitation energies significantly. A different set of parameters, which are optimized for DFTB3, slightly improves the prediction of adiabatic excitation energies statistically. The application of TD-DFTB for the prediction of absorption and fluorescence energies of cresyl violet demonstrates that TD-DFTB3 reproduced the experimental fluorescence energy quite well.

  2. Power density and temperature dependent multi-excited states in InAs/GaAs quantum dots

    International Nuclear Information System (INIS)

    Bouzaïene, L.; Sfaxi, L.; Baira, M.; Maaref, H.; Bru-Chevallier, C.

    2011-01-01

    Self-assembled InAs/GaAs (001) quantum dots (QDs) were grown by molecular beam epitaxy using ultra low-growth rate. A typical dot diameter of around 28 ± 2 nm and a typical height of 5 ± 1 nm are observed based on atomic force microscopy image. The photoluminescence (PL) spectra, their power and temperature dependences have been studied for ground (GS) and three excited states (1–3ES) in InAs QDs. By changing the excitation power density, we can significantly influence the distribution of excitons within the QD ensemble. The PL peak energy positions of GS and ES emissions bands depend on an excitation light power. With increasing excitation power, the GS emission energy was red-shifted, while the 1–3ES emission energies were blue-shifted. It is found that the full width at half maximum of the PL spectra has unusual relationship with increasing temperature from 9 to 300 K. The temperature dependence of QD PL spectra shown the existence of two stages of PL thermal quenching and two distinct activation energies corresponding to the temperature ranges I (9–100 K) and II (100–300 K).

  3. Statistical density of nuclear excited states

    Directory of Open Access Journals (Sweden)

    V. M. Kolomietz

    2015-10-01

    Full Text Available A semi-classical approximation is applied to the calculations of single-particle and statistical level densities in excited nuclei. Landau's conception of quasi-particles with the nucleon effective mass m* < m is used. The approach provides the correct description of the continuum contribution to the level density for realistic finite-depth potentials. It is shown that the continuum states does not affect significantly the thermodynamic calculations for sufficiently small temperatures T ≤ 1 MeV but reduce strongly the results for the excitation energy at high temperatures. By use of standard Woods - Saxon potential and nucleon effective mass m* = 0.7m the A-dependency of the statistical level density parameter K was evaluated in a good qualitative agreement with experimental data.

  4. Momentum and density dependence of the nuclear mean field

    International Nuclear Information System (INIS)

    Behera, B.; Routray, T.R.

    1999-01-01

    The purpose of this is to analyse the momentum, density and temperature dependence of the mean field in nuclear matter derived from finite range effective interactions and to examine the influence of the functional form of the interaction on the high momentum behaviour of the mean field. Emphasis will be given to use very simple parametrizations of the effective interaction with a minimum number of adjustable parameters and yet capable of giving a good description of the mean field in nuclear matter over a wide range of momentum, density and temperature. As an application of the calculated equation of state of nuclear matter, phase transitions to quark-gluon plasma is studied where the quark phase is described by a zeroth order bag model equation of state

  5. Density of states in an optical speckle potential

    International Nuclear Information System (INIS)

    Falco, G. M.; Fedorenko, A. A.; Giacomelli, J.; Modugno, M.

    2010-01-01

    We study the single-particle density of states of a one-dimensional speckle potential, which is correlated and non-Gaussian. We consider both the repulsive and the attractive cases. The system is controlled by a single dimensionless parameter determined by the mass of the particle, the correlation length, and the average intensity of the field. Depending on the value of this parameter, the system exhibits different regimes, characterized by the localization properties of the eigenfunctions. We calculate the corresponding density of states using the statistical properties of the speckle potential. We find good agreement with the results of numerical simulations.

  6. Regulatory function of a novel population of mouse autoantigen-specific Foxp3 regulatory T cells depends on IFN-gamma, NO, and contact with target cells.

    Directory of Open Access Journals (Sweden)

    Cyndi Chen

    Full Text Available BACKGROUND: Both naturally arising Foxp3(+ and antigen-induced Foxp3(- regulatory T cells (Treg play a critical role in regulating immune responses, as well as in preventing autoimmune diseases and graft rejection. It is known that antigen-specific Treg are more potent than polyclonal Treg in suppressing pathogenic immune responses that cause autoimmunity and inflammation. However, difficulty in identifying and isolating a sufficient number of antigen-specific Treg has limited their use in research to elucidate the mechanisms underlying their regulatory function and their potential role in therapy. METHODOLOGY/PRINCIPAL FINDINGS: Using a novel class II MHC tetramer, we have isolated a population of CD4(+ Foxp3(- T cells specific for the autoantigen glutamic acid decarboxylase p286-300 peptide (NR286 T cells from diabetes-resistant non-obese resistant (NOR mice. These Foxp3(- NR286 T cells functioned as Treg that were able to suppress target T cell proliferation in vitro and inhibit type 1 diabetes in animals. Unexpected results from mechanistic studies in vitro showed that their regulatory function was dependent on not only IFN-gamma and nitric oxide, but also on cell contact with target cells. In addition, separating NR286 Treg from target T cells in transwell assays abolished both production of NO and suppression of target T cells, regardless of whether IFN-gamma was produced in cell cultures. Therefore, production of NO, not IFN-gamma, was cell contact dependent, suggesting that NO may function downstream of IFN-gamma in mediating regulatory function of NR286 Treg. CONCLUSIONS/SIGNIFICANCE: These studies identified a unique population of autoantigen-specific Foxp3(- Treg that can exert their regulatory function dependent on not only IFN-gamma and NO but also cell contact with target cells.

  7. Collective cell migration without proliferation: density determines cell velocity and wave velocity

    Science.gov (United States)

    Tlili, Sham; Gauquelin, Estelle; Li, Brigitte; Cardoso, Olivier; Ladoux, Benoît; Delanoë-Ayari, Hélène; Graner, François

    2018-05-01

    Collective cell migration contributes to embryogenesis, wound healing and tumour metastasis. Cell monolayer migration experiments help in understanding what determines the movement of cells far from the leading edge. Inhibiting cell proliferation limits cell density increase and prevents jamming; we observe long-duration migration and quantify space-time characteristics of the velocity profile over large length scales and time scales. Velocity waves propagate backwards and their frequency depends only on cell density at the moving front. Both cell average velocity and wave velocity increase linearly with the cell effective radius regardless of the distance to the front. Inhibiting lamellipodia decreases cell velocity while waves either disappear or have a lower frequency. Our model combines conservation laws, monolayer mechanical properties and a phenomenological coupling between strain and polarity: advancing cells pull on their followers, which then become polarized. With reasonable values of parameters, this model agrees with several of our experimental observations. Together, our experiments and model disantangle the respective contributions of active velocity and of proliferation in monolayer migration, explain how cells maintain their polarity far from the moving front, and highlight the importance of strain-polarity coupling and density in long-range information propagation.

  8. Differential cytotoxic effects of 7-dehydrocholesterol-derived oxysterols on cultured retina-derived cells: Dependence on sterol structure, cell type, and density.

    Science.gov (United States)

    Pfeffer, Bruce A; Xu, Libin; Porter, Ned A; Rao, Sriganesh Ramachandra; Fliesler, Steven J

    2016-04-01

    Tissue accumulation of 7-dehydrocholesterol (7DHC) is a hallmark of Smith-Lemli-Opitz Syndrome (SLOS), a human inborn error of the cholesterol (CHOL) synthesis pathway. Retinal 7DHC-derived oxysterol formation occurs in the AY9944-induced rat model of SLOS, which exhibits a retinal degeneration characterized by selective loss of photoreceptors and associated functional deficits, Müller cell hypertrophy, and engorgement of the retinal pigment epithelium (RPE) with phagocytic inclusions. We evaluated the relative effects of four 7DHC-derived oxysterols on three retina-derived cell types in culture, with respect to changes in cellular morphology and viability. 661W (photoreceptor-derived) cells, rMC-1 (Müller glia-derived) cells, and normal diploid monkey RPE (mRPE) cells were incubated for 24 h with dose ranges of either 7-ketocholesterol (7kCHOL), 5,9-endoperoxy-cholest-7-en-3β,6α-diol (EPCD), 3β,5α-dihydroxycholest-7-en-6-one (DHCEO), or 4β-hydroxy-7-dehydrocholesterol (4HDHC); CHOL served as a negative control (same dose range), along with appropriate vehicle controls, while staurosporine (Stsp) was used as a positive cytotoxic control. For 661W cells, the rank order of oxysterol potency was: EPCD > 7kCHOL > DHCEO > 4HDHC ≈ CHOL. EC50 values were higher for confluent vs. subconfluent cultures. 661W cells exhibited much higher sensitivity to EPCD and 7kCHOL than either rMC-1 or mRPE cells, with the latter being the most robust when challenged, either at confluence or in sub-confluent cultures. When tested on rMC-1 and mRPE cells, EPCD was again an order of magnitude more potent than 7kCHOL in compromising cellular viability. Hence, 7DHC-derived oxysterols elicit differential cytotoxicity that is dose-, cell type-, and cell density-dependent. These results are consistent with the observed progressive, photoreceptor-specific retinal degeneration in the rat SLOS model, and support the hypothesis that 7DHC-derived oxysterols are causally linked to that

  9. CCL22-specific T Cells

    DEFF Research Database (Denmark)

    Martinenaite, Evelina; Munir Ahmad, Shamaila; Hansen, Morten

    2016-01-01

    Tumor cells and tumor-infiltrating macrophages produce the chemokine CCL22, which attracts regulatory T cells (Tregs) into the tumor microenvironment, decreasing anticancer immunity. Here, we investigated the possibility of targeting CCL22-expressing cells by activating specific T cells. We...... analyzed the CCL22 protein signal sequence, identifying a human leukocyte antigen A2- (HLA-A2-) restricted peptide epitope, which we then used to stimulate peripheral blood mononuclear cells (PMBCs) to expand populations of CCL22-specific T cells in vitro. T cells recognizing an epitope derived from...... the signal-peptide of CCL22 will recognize CCL22-expressing cells even though CCL22 is secreted out of the cell. CCL22-specific T cells recognized and killed CCL22-expressing cancer cells. Furthermore, CCL22-specific T cells lysed acute monocytic leukemia cells in a CCL22 expression-dependent manner. Using...

  10. Cell kinetics of differentiation of Na+-dependent hexose transport in a cultured renal epithelial cell line

    International Nuclear Information System (INIS)

    Cook, J.S.; Weiss, E.R.

    1985-01-01

    Fully differentiated cells of the renal proximal tubule have the capability of taking up hexoses across their apical borders by transport coupled to the Na + -electrochemical gradient. This property is also found in postconfluent cultures of the cloned cell line LLC-PK 1 , a morphologically polarized line of renal cells. Postconfluent cells develop the Na + -dependent capacity to transport hexoses at their apical surface. This function is not observable during the growth phase of the cultures. To analyze the developmental process at the cellular level a method has been derived to separate transporting cells, expressing the differentiated function, from nontransporting cells. The method is based on the swelling of the cells accompanying the uptake of the nonmetabolizable glucose analog alpha methylglucoside. The swollen cells have a lower buoyant density than the undifferentiated cells and may be separated from them on density gradients. Analysis of the distribution of cells on such gradients shows that after the cells reach confluence the undifferentiated subpopulation is recruited onto the differentiation pathway with a rate constant of 0.2 per day, that 5 to 7 days are required for a cell to traverse this pathway to the fully differentiated state, and that once the maximum uptake capacity is achieved the cells do not develop further

  11. Herbivore-specific, density-dependent induction of plant volatiles: honest or "cry wolf" signals?

    Directory of Open Access Journals (Sweden)

    Kaori Shiojiri

    Full Text Available Plants release volatile chemicals upon attack by herbivorous arthropods. They do so commonly in a dose-dependent manner: the more herbivores, the more volatiles released. The volatiles attract predatory arthropods and the amount determines the probability of predator response. We show that seedlings of a cabbage variety (Brassica oleracea var. capitata, cv Shikidori also show such a response to the density of cabbage white (Pieris rapae larvae and attract more (naive parasitoids (Cotesia glomerata when there are more herbivores on the plant. However, when attacked by diamondback moth (Plutella xylostella larvae, seedlings of the same variety (cv Shikidori release volatiles, the total amount of which is high and constant and thus independent of caterpillar density, and naive parasitoids (Cotesia vestalis of diamondback moth larvae fail to discriminate herbivore-rich from herbivore-poor plants. In contrast, seedlings of another cabbage variety of B. oleracea (var. acephala: kale respond in a dose-dependent manner to the density of diamondback moth larvae and attract more parasitoids when there are more herbivores. Assuming these responses of the cabbage cultivars reflect behaviour of at least some genotypes of wild plants, we provide arguments why the behaviour of kale (B. oleracea var acephala is best interpreted as an honest signaling strategy and that of cabbage cv Shikidori (B. oleracea var capitata as a "cry wolf" signaling strategy, implying a conflict of interest between the plant and the enemies of its herbivores: the plant profits from being visited by the herbivore's enemies, but the latter would be better off by visiting other plants with more herbivores. If so, evolutionary theory on alarm signaling predicts consequences of major interest to students of plant protection, tritrophic systems and communication alike.

  12. Detection of density dependence requires density manipulations and calculation of lambda.

    Science.gov (United States)

    Fowler, N L; Overath, R Deborah; Pease, Craig M

    2006-03-01

    To investigate density-dependent population regulation in the perennial bunchgrass Bouteloua rigidiseta, we experimentally manipulated density by removing adults or adding seeds to replicate quadrats in a natural population for three annual intervals. We monitored the adjacent control quadrats for 14 annual intervals. We constructed a population projection matrix for each quadrat in each interval, calculated lambda, and did a life table response experiment (LTRE) analysis. We tested the effects of density upon lambda by comparing experimental and control quadrats, and by an analysis of the 15-year observational data set. As measured by effects on lambda and on N(t+1/Nt in the experimental treatments, negative density dependence was strong: the population was being effectively regulated. The relative contributions of different matrix elements to treatment effect on lambda differed among years and treatments; overall the pattern was one of small contributions by many different life cycle stages. In contrast, density dependence could not be detected using only the observational (control quadrats) data, even though this data set covered a much longer time span. Nor did experimental effects on separate matrix elements reach statistical significance. These results suggest that ecologists may fail to detect density dependence when it is present if they have only descriptive, not experimental, data, do not have data for the entire life cycle, or analyze life cycle components separately.

  13. Density-dependent growth in invasive Lionfish (Pterois volitans).

    Science.gov (United States)

    Benkwitt, Cassandra E

    2013-01-01

    Direct demographic density dependence is necessary for population regulation and is a central concept in ecology, yet has not been studied in many invasive species, including any invasive marine fish. The red lionfish (Pterois volitans) is an invasive predatory marine fish that is undergoing exponential population growth throughout the tropical western Atlantic. Invasive lionfish threaten coral-reef ecosystems, but there is currently no evidence of any natural population control. Therefore, a manipulative field experiment was conducted to test for density dependence in lionfish. Juvenile lionfish densities were adjusted on small reefs and several demographic rates (growth, recruitment, immigration, and loss) were measured throughout an 8-week period. Invasive lionfish exhibited direct density dependence in individual growth rates, as lionfish grew slower at higher densities throughout the study. Individual growth in length declined linearly with increasing lionfish density, while growth in mass declined exponentially with increasing density. There was no evidence, however, for density dependence in recruitment, immigration, or loss (mortality plus emigration) of invasive lionfish. The observed density-dependent growth rates may have implications for which native species are susceptible to lionfish predation, as the size and type of prey that lionfish consume is directly related to their body size. The absence of density-dependent loss, however, contrasts with many native coral-reef fish species and suggests that for the foreseeable future manual removals may be the only effective local control of this invasion.

  14. Density-dependent growth in invasive Lionfish (Pterois volitans.

    Directory of Open Access Journals (Sweden)

    Cassandra E Benkwitt

    Full Text Available Direct demographic density dependence is necessary for population regulation and is a central concept in ecology, yet has not been studied in many invasive species, including any invasive marine fish. The red lionfish (Pterois volitans is an invasive predatory marine fish that is undergoing exponential population growth throughout the tropical western Atlantic. Invasive lionfish threaten coral-reef ecosystems, but there is currently no evidence of any natural population control. Therefore, a manipulative field experiment was conducted to test for density dependence in lionfish. Juvenile lionfish densities were adjusted on small reefs and several demographic rates (growth, recruitment, immigration, and loss were measured throughout an 8-week period. Invasive lionfish exhibited direct density dependence in individual growth rates, as lionfish grew slower at higher densities throughout the study. Individual growth in length declined linearly with increasing lionfish density, while growth in mass declined exponentially with increasing density. There was no evidence, however, for density dependence in recruitment, immigration, or loss (mortality plus emigration of invasive lionfish. The observed density-dependent growth rates may have implications for which native species are susceptible to lionfish predation, as the size and type of prey that lionfish consume is directly related to their body size. The absence of density-dependent loss, however, contrasts with many native coral-reef fish species and suggests that for the foreseeable future manual removals may be the only effective local control of this invasion.

  15. Electron-Ion Dynamics with Time-Dependent Density Functional Theory: Towards Predictive Solar Cell Modeling: Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Maitra, Neepa [Hunter College City University of New York, New York, NY (United States)

    2016-07-14

    This project investigates the accuracy of currently-used functionals in time-dependent density functional theory, which is today routinely used to predict and design materials and computationally model processes in solar energy conversion. The rigorously-based electron-ion dynamics method developed here sheds light on traditional methods and overcomes challenges those methods have. The fundamental research undertaken here is important for building reliable and practical methods for materials discovery. The ultimate goal is to use these tools for the computational design of new materials for solar cell devices of high efficiency.

  16. Inflammation triggers emergency granulopoiesis through a density-dependent feedback mechanism.

    Directory of Open Access Journals (Sweden)

    Derek W Cain

    Full Text Available Normally, neutrophil pools are maintained by homeostatic mechanisms that require the transcription factor C/EBPα. Inflammation, however, induces neutrophilia through a distinct pathway of "emergency" granulopoiesis that is dependent on C/EBPβ. Here, we show in mice that alum triggers emergency granulopoiesis through the IL-1RI-dependent induction of G-CSF. G-CSF/G-CSF-R neutralization impairs proliferative responses of hematopoietic stem and progenitor cells (HSPC to alum, but also abrogates the acute mobilization of BM neutrophils, raising the possibility that HSPC responses to inflammation are an indirect result of the exhaustion of BM neutrophil stores. The induction of neutropenia, via depletion with Gr-1 mAb or myeloid-specific ablation of Mcl-1, elicits G-CSF via an IL-1RI-independent pathway, stimulating granulopoietic responses indistinguishable from those induced by adjuvant. Notably, C/EBPβ, thought to be necessary for enhanced generative capacity of BM, is dispensable for increased proliferation of HSPC to alum or neutropenia, but plays a role in terminal neutrophil differentiation during granulopoietic recovery. We conclude that alum elicits a transient increase in G-CSF production via IL-1RI for the mobilization of BM neutrophils, but density-dependent feedback sustains G-CSF for accelerated granulopoiesis.

  17. Dynamics of Spontaneous Emission Controlled by Local Density of States in Photonic Crystals

    DEFF Research Database (Denmark)

    Lodahl, Peter; Nikolaev, Ivan S.; van Driel, A. Floris

    2006-01-01

    We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter.......We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter....

  18. Density and starting-energy dependent effective interaction

    International Nuclear Information System (INIS)

    Yamaguchi, Norio; Nagata, Sinobu; Kasuga, Teruo

    1979-01-01

    A new effective potential constructed from the reaction matrix calculation of nuclear matters is proposed, taking three-body effects into account. Starting from the two-body scattering equation for nuclear matters, an equation with averaged momentum is introduced as the definition of effective interaction. The parameters in the equation are the Fermi momentum and the starting energy. The nuclear density dependence and the starting energy dependence are independently treated in the potential. The effective interactions including three-body effects were calculated. The dependence on the starting energy is large. The effective interaction is more attractive in the triplet E state, and assures overall saturation without any artificial renormalization. The reaction matrix calculation can be well reproduced by the calculation with this effective potential. The results of calculation for the binding energy of He-4 and O-16 and the shell model matrix elements of O-16 are represented. (Kato, T.)

  19. Time-Dependent Density Functional Theory for Open Systems and Its Applications.

    Science.gov (United States)

    Chen, Shuguang; Kwok, YanHo; Chen, GuanHua

    2018-02-20

    Photovoltaic devices, electrochemical cells, catalysis processes, light emitting diodes, scanning tunneling microscopes, molecular electronics, and related devices have one thing in common: open quantum systems where energy and matter are not conserved. Traditionally quantum chemistry is confined to isolated and closed systems, while quantum dissipation theory studies open quantum systems. The key quantity in quantum dissipation theory is the reduced system density matrix. As the reduced system density matrix is an O(M! × M!) matrix, where M is the number of the particles of the system of interest, quantum dissipation theory can only be employed to simulate systems of a few particles or degrees of freedom. It is thus important to combine quantum chemistry and quantum dissipation theory so that realistic open quantum systems can be simulated from first-principles. We have developed a first-principles method to simulate the dynamics of open electronic systems, the time-dependent density functional theory for open systems (TDDFT-OS). Instead of the reduced system density matrix, the key quantity is the reduced single-electron density matrix, which is an N × N matrix where N is the number of the atomic bases of the system of interest. As the dimension of the key quantity is drastically reduced, the TDDFT-OS can thus be used to simulate the dynamics of realistic open electronic systems and efficient numerical algorithms have been developed. As an application, we apply the method to study how quantum interference develops in a molecular transistor in time domain. We include electron-phonon interaction in our simulation and show that quantum interference in the given system is robust against nuclear vibration not only in the steady state but also in the transient dynamics. As another application, by combining TDDFT-OS with Ehrenfest dynamics, we study current-induced dissociation of water molecules under scanning tunneling microscopy and follow its time dependent

  20. Density-dependence as a size-independent regulatory mechanism.

    Science.gov (United States)

    de Vladar, Harold P

    2006-01-21

    The growth function of populations is central in biomathematics. The main dogma is the existence of density-dependence mechanisms, which can be modelled with distinct functional forms that depend on the size of the population. One important class of regulatory functions is the theta-logistic, which generalizes the logistic equation. Using this model as a motivation, this paper introduces a simple dynamical reformulation that generalizes many growth functions. The reformulation consists of two equations, one for population size, and one for the growth rate. Furthermore, the model shows that although population is density-dependent, the dynamics of the growth rate does not depend either on population size, nor on the carrying capacity. Actually, the growth equation is uncoupled from the population size equation, and the model has only two parameters, a Malthusian parameter rho and a competition coefficient theta. Distinct sign combinations of these parameters reproduce not only the family of theta-logistics, but also the van Bertalanffy, Gompertz and Potential Growth equations, among other possibilities. It is also shown that, except for two critical points, there is a general size-scaling relation that includes those appearing in the most important allometric theories, including the recently proposed Metabolic Theory of Ecology. With this model, several issues of general interest are discussed such as the growth of animal population, extinctions, cell growth and allometry, and the effect of environment over a population.

  1. Color ferromagnetic vacuum states in QCD and two-loop energy densities

    International Nuclear Information System (INIS)

    Nielsen, H.B.; Ninomiya, M.

    1979-12-01

    Two-loop energy densities of color ferromagnetic states are obtained using the β-function calculated to two-loop approximation and the exact formula for the energy density of such a state. This is used to derive bounds on the MIT bag constant correcting the previous bound in one-loop approximation. For a constant field color ferromagnetic ansatz state the bound on the QCD scale parameter Λsub(p) 3 -vacuum ansatz with two-loop and instanton correction gives Λsub(p)<= 0.16 GeV. Tt is stressed that the 'perturbative vacuum', which is identified with the inside bag state is a somewhat ill defined concept due to a path-dependence in the integral giving the energy density. (Auth.)

  2. Strong adhesion by regulatory T cells induces dendritic cell cytoskeletal polarization and contact-dependent lethargy.

    Science.gov (United States)

    Chen, Jiahuan; Ganguly, Anutosh; Mucsi, Ashley D; Meng, Junchen; Yan, Jiacong; Detampel, Pascal; Munro, Fay; Zhang, Zongde; Wu, Mei; Hari, Aswin; Stenner, Melanie D; Zheng, Wencheng; Kubes, Paul; Xia, Tie; Amrein, Matthias W; Qi, Hai; Shi, Yan

    2017-02-01

    Dendritic cells are targeted by regulatory T (T reg) cells, in a manner that operates as an indirect mode of T cell suppression. In this study, using a combination of single-cell force spectroscopy and structured illumination microscopy, we analyze individual T reg cell-DC interaction events and show that T reg cells exhibit strong intrinsic adhesiveness to DCs. This increased DC adhesion reduces the ability of contacted DCs to engage other antigen-specific cells. We show that this unusually strong LFA-1-dependent adhesiveness of T reg cells is caused in part by their low calpain activities, which normally release integrin-cytoskeleton linkage, and thereby reduce adhesion. Super resolution imaging reveals that such T reg cell adhesion causes sequestration of Fascin-1, an actin-bundling protein essential for immunological synapse formation, and skews Fascin-1-dependent actin polarization in DCs toward the T reg cell adhesion zone. Although it is reversible upon T reg cell disengagement, this sequestration of essential cytoskeletal components causes a lethargic state of DCs, leading to reduced T cell priming. Our results reveal a dynamic cytoskeletal component underlying T reg cell-mediated DC suppression in a contact-dependent manner. © 2017 Chen et al.

  3. Common themes and cell type specific variations of higher order chromatin arrangements in the mouse

    Directory of Open Access Journals (Sweden)

    Cremer Thomas

    2005-12-01

    Full Text Available Abstract Background Similarities as well as differences in higher order chromatin arrangements of human cell types were previously reported. For an evolutionary comparison, we now studied the arrangements of chromosome territories and centromere regions in six mouse cell types (lymphocytes, embryonic stem cells, macrophages, fibroblasts, myoblasts and myotubes with fluorescence in situ hybridization and confocal laser scanning microscopy. Both species evolved pronounced differences in karyotypes after their last common ancestors lived about 87 million years ago and thus seem particularly suited to elucidate common and cell type specific themes of higher order chromatin arrangements in mammals. Results All mouse cell types showed non-random correlations of radial chromosome territory positions with gene density as well as with chromosome size. The distribution of chromosome territories and pericentromeric heterochromatin changed during differentiation, leading to distinct cell type specific distribution patterns. We exclude a strict dependence of these differences on nuclear shape. Positional differences in mouse cell nuclei were less pronounced compared to human cell nuclei in agreement with smaller differences in chromosome size and gene density. Notably, the position of chromosome territories relative to each other was very variable. Conclusion Chromosome territory arrangements according to chromosome size and gene density provide common, evolutionary conserved themes in both, human and mouse cell types. Our findings are incompatible with a previously reported model of parental genome separation.

  4. Obtaining Hartree-Fock and density functional theory doubly excited states with Car-Parrinello density matrix search

    Science.gov (United States)

    Liang, Wenkel; Isborn, Christine M.; Li, Xiaosong

    2009-11-01

    The calculation of doubly excited states is one of the major problems plaguing the modern day excited state workhorse methodology of linear response time dependent Hartree-Fock (TDHF) and density function theory (TDDFT). We have previously shown that the use of a resonantly tuned field within real-time TDHF and TDDFT is able to simultaneously excite both the α and β electrons to achieve the two-electron excited states of minimal basis H2 and HeH+ [C. M. Isborn and X. Li, J. Chem. Phys. 129, 204107 (2008)]. We now extend this method to many electron systems with the use of our Car-Parrinello density matrix search (CP-DMS) with a first-principles fictitious mass method for wave function optimization [X. Li, C. L. Moss, W. Liang, and Y. Feng, J. Chem. Phys. 130, 234115 (2009)]. Real-time TDHF/TDDFT is used during the application of the laser field perturbation, driving the electron density toward the doubly excited state. The CP-DMS method then converges the density to the nearest stationary state. We present these stationary state doubly excited state energies and properties at the HF and DFT levels for H2, HeH+, lithium hydride, ethylene, and butadiene.

  5. Excitation dependence of resonance line self-broadening at different atomic densities

    OpenAIRE

    Li, Hebin; Sautenkov, Vladimir A.; Rostovtsev, Yuri V.; Scully, Marlan O.

    2009-01-01

    We study the dipole-dipole spectral broadening of a resonance line at high atomic densities when the self-broadening dominates. The selective reflection spectrum of a weak probe beam from the interface of the cell window and rubidium vapor are recorded in the presence of a far-detuned pump beam. The excitation due to the pump reduces the self-broadening. We found that the self-broadening reduction dependence on the pump power is atomic density independent. These results provide experimental e...

  6. Density dependence of the nuclear energy-density functional

    Science.gov (United States)

    Papakonstantinou, Panagiota; Park, Tae-Sun; Lim, Yeunhwan; Hyun, Chang Ho

    2018-01-01

    Background: The explicit density dependence in the coupling coefficients entering the nonrelativistic nuclear energy-density functional (EDF) is understood to encode effects of three-nucleon forces and dynamical correlations. The necessity for the density-dependent coupling coefficients to assume the form of a preferably small fractional power of the density ρ is empirical and the power is often chosen arbitrarily. Consequently, precision-oriented parametrizations risk overfitting in the regime of saturation and extrapolations in dilute or dense matter may lose predictive power. Purpose: Beginning with the observation that the Fermi momentum kF, i.e., the cubic root of the density, is a key variable in the description of Fermi systems, we first wish to examine if a power hierarchy in a kF expansion can be inferred from the properties of homogeneous matter in a domain of densities, which is relevant for nuclear structure and neutron stars. For subsequent applications we want to determine a functional that is of good quality but not overtrained. Method: For the EDF, we fit systematically polynomial and other functions of ρ1 /3 to existing microscopic, variational calculations of the energy of symmetric and pure neutron matter (pseudodata) and analyze the behavior of the fits. We select a form and a set of parameters, which we found robust, and examine the parameters' naturalness and the quality of resulting extrapolations. Results: A statistical analysis confirms that low-order terms such as ρ1 /3 and ρ2 /3 are the most relevant ones in the nuclear EDF beyond lowest order. It also hints at a different power hierarchy for symmetric vs. pure neutron matter, supporting the need for more than one density-dependent term in nonrelativistic EDFs. The functional we propose easily accommodates known or adopted properties of nuclear matter near saturation. More importantly, upon extrapolation to dilute or asymmetric matter, it reproduces a range of existing microscopic

  7. density-dependent selection revisited

    Indian Academy of Sciences (India)

    Unknown

    is a more useful way of looking at density-dependent selection, and then go on ... these models was that the condition for maintenance of ... In a way, their formulation may be viewed as ... different than competition among species, and typical.

  8. Effect of Monocular Deprivation on Rabbit Neural Retinal Cell Densities.

    Science.gov (United States)

    Mwachaka, Philip Maseghe; Saidi, Hassan; Odula, Paul Ochieng; Mandela, Pamela Idenya

    2015-01-01

    To describe the effect of monocular deprivation on densities of neural retinal cells in rabbits. Thirty rabbits, comprised of 18 subject and 12 control animals, were included and monocular deprivation was achieved through unilateral lid suturing in all subject animals. The rabbits were observed for three weeks. At the end of each week, 6 experimental and 3 control animals were euthanized, their retinas was harvested and processed for light microscopy. Photomicrographs of the retina were taken and imported into FIJI software for analysis. Neural retinal cell densities of deprived eyes were reduced along with increasing period of deprivation. The percentage of reductions were 60.9% (P < 0.001), 41.6% (P = 0.003), and 18.9% (P = 0.326) for ganglion, inner nuclear, and outer nuclear cells, respectively. In non-deprived eyes, cell densities in contrast were increased by 116% (P < 0.001), 52% (P < 0.001) and 59.6% (P < 0.001) in ganglion, inner nuclear, and outer nuclear cells, respectively. In this rabbit model, monocular deprivation resulted in activity-dependent changes in cell densities of the neural retina in favour of the non-deprived eye along with reduced cell densities in the deprived eye.

  9. Sequential double excitations from linear-response time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Mosquera, Martín A.; Ratner, Mark A.; Schatz, George C., E-mail: g-schatz@northwestern.edu [Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208 (United States); Chen, Lin X. [Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208 (United States); Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave., Lemont, Illinois 60439 (United States)

    2016-05-28

    Traditional UV/vis and X-ray spectroscopies focus mainly on the study of excitations starting exclusively from electronic ground states. However there are many experiments where transitions from excited states, both absorption and emission, are probed. In this work we develop a formalism based on linear-response time-dependent density functional theory to investigate spectroscopic properties of excited states. We apply our model to study the excited-state absorption of a diplatinum(II) complex under X-rays, and transient vis/UV absorption of pyrene and azobenzene.

  10. Time-dependent internal density functional theory formalism and Kohn-Sham scheme for self-bound systems

    International Nuclear Information System (INIS)

    Messud, Jeremie

    2009-01-01

    The stationary internal density functional theory (DFT) formalism and Kohn-Sham scheme are generalized to the time-dependent case. It is proven that, in the time-dependent case, the internal properties of a self-bound system (such as an atomic nuclei or a helium droplet) are all defined by the internal one-body density and the initial state. A time-dependent internal Kohn-Sham scheme is set up as a practical way to compute the internal density. The main difference from the traditional DFT formalism and Kohn-Sham scheme is the inclusion of the center-of-mass correlations in the functional.

  11. Hydrodynamic perspective on memory in time-dependent density-functional theory

    International Nuclear Information System (INIS)

    Thiele, M.; Kuemmel, S.

    2009-01-01

    The adiabatic approximation of time-dependent density-functional theory is studied in the context of nonlinear excitations of two-electron singlet systems. We compare the exact time evolution of these systems to the adiabatically exact one obtained from time-dependent Kohn-Sham calculations relying on the exact ground-state exchange-correlation potential. Thus, we can show under which conditions the adiabatic approximation breaks down and memory effects become important. The hydrodynamic formulation of quantum mechanics allows us to interpret these results and relate them to dissipative effects in the Kohn-Sham system. We show how the breakdown of the adiabatic approximation can be inferred from the rate of change of the ground-state noninteracting kinetic energy.

  12. Cells of the J774 macrophage cell line are primed for antibody-dependent cell-mediated cytotoxicity following exposure to γ-irradiation

    International Nuclear Information System (INIS)

    Duerst, R.; Werberig, K.

    1991-01-01

    Activation of macrophages (M phi) for host defense against tumor cells follows a sequence of priming events followed by an initiating stimulus that results in production and release of cytotoxic molecules that mediate target cell killing. The authors have developed a model to study specific macrophage cytotoxicity in vitro utilizing a cultured murine M phi cell line, J774. Specific cytotoxicity of cultured human gastrointestinal tumor cells is achieved in the presence of murine IgG2a monoclonal antibody (mAb) 17-1-A. The ability of these cells to mediate antibody-dependent cell-mediated cytotoxicity (ADCC) is greatly enhanced following gamma-irradiation. ADCC can be demonstrated at mAb 17-1-A concentrations greater than or equal to 1 microgram/ml and effector/target cell ratios greater than or equal to 2. Exposure to doses greater than or equal to 10 Gy of gamma-irradiation increases ADCC threefold. Varying the duration from J774 M phi exposure to γ-irradiation until addition of antibody-coated target cells showed that the primed state for ADCC is stable for at least 8 days but approximately 24 hr is required for complete development of the primed state. mAb-dependent target cell death begins 8 hr after addition of mAb and labeled target cells to primed effector cells and is complete by 24 hr. Incubation of unirradiated J774 M phi effector cells with recombinant murine interferon-γ (rmIFN-γ) also results in enhanced ADCC, but the extent of target cell killing achieved is less than that following priming by γ-irradiation. Concomitant priming of γ-irradiated J774 M phi with rmIFN-γ increases the extent of ADCC. Further study of irradiated J774 cells may elucidate the molecular pathways utilized by M phi for achieving and maintaining the primed state for ADCC

  13. Size-dependent oscillator strength and quantum efficiency of CdSe quantum dots controlled via the local density of states

    DEFF Research Database (Denmark)

    Leistikow, M.D.; Johansen, Jeppe; Kettelarij, A.J.

    2009-01-01

    We study experimentally time-resolved emission of colloidal CdSe quantum dots in an environment with a controlled local density of states LDOS. The decay rate is measured versus frequency and as a function of distance to a mirror. We observe a linear relation between the decay rate and the LDOS, ...... with the measured radiative rates. Our results are relevant for applications of CdSe quantum dots in spontaneous emission control and cavity quantum electrodynamics.......We study experimentally time-resolved emission of colloidal CdSe quantum dots in an environment with a controlled local density of states LDOS. The decay rate is measured versus frequency and as a function of distance to a mirror. We observe a linear relation between the decay rate and the LDOS......, allowing us to determine the size-dependent quantum efficiency and oscillator strength. We find that the quantum efficiency decreases with increasing emission energy mostly due to an increase in nonradiative decay. We manage to obtain the oscillator strength of the important class of CdSe quantum dots...

  14. Cell density-dependent nuclear/cytoplasmic localization of NORPEG (RAI14) protein

    International Nuclear Information System (INIS)

    Kutty, R. Krishnan; Chen, Shanyi; Samuel, William; Vijayasarathy, Camasamudram; Duncan, Todd; Tsai, Jen-Yue; Fariss, Robert N.; Carper, Deborah; Jaworski, Cynthia; Wiggert, Barbara

    2006-01-01

    NORPEG (RAI14), a developmentally regulated gene induced by retinoic acid, encodes a 980 amino acid (aa) residue protein containing six ankyrin repeats and a long coiled-coil domain [Kutty et al., J. Biol. Chem. 276 (2001), pp. 2831-2840]. We have expressed aa residues 1-287 of NORPEG and used the recombinant protein to produce an anti-NORPEG polyclonal antibody. Confocal immunofluorescence analysis showed that the subcellular localization of NORPEG in retinal pigment epithelial (ARPE-19) cells varies with cell density, with predominantly nuclear localization in nonconfluent cells, but a cytoplasmic localization, reminiscent of cytoskeleton, in confluent cultures. Interestingly, an evolutionarily conserved putative monopartite nuclear localization signal (P 27 KKRKAP 276 ) was identified by analyzing the sequences of NORPEG and its orthologs. GFP-NORPEG (2-287 aa), a fusion protein containing this signal, was indeed localized to nuclei when expressed in ARPE-19 or COS-7 cells. Deletion and mutation analysis indicated that the identified nuclear localization sequence is indispensable for nuclear targeting

  15. TRX-ASK1-JNK signaling regulation of cell density-dependent cytotoxicity in cigarette smoke-exposed human bronchial epithelial cells.

    Science.gov (United States)

    Lee, Yong Chan; Chuang, Chun-Yu; Lee, Pak-Kei; Lee, Jin-Soo; Harper, Richart W; Buckpitt, Alan B; Wu, Reen; Oslund, Karen

    2008-05-01

    Cigarette smoke is a major environmental air pollutant that injures airway epithelium and incites subsequent diseases including chronic obstructive pulmonary disease. The lesion that smoke induces in airway epithelium is still incompletely understood. Using a LIVE/DEAD cytotoxicity assay, we observed that subconfluent cultures of bronchial epithelial cells derived from both human and monkey airway tissues and an immortalized normal human bronchial epithelial cell line (HBE1) were more susceptible to injury by cigarette smoke extract (CSE) and by direct cigarette smoke exposure than cells in confluent cultures. Scraping confluent cultures also caused an enhanced cell injury predominately in the leading edge of the scraped confluent cultures by CSE. Cellular ATP levels in both subconfluent and confluent cultures were drastically reduced after CSE exposure. In contrast, GSH levels were significantly reduced only in subconfluent cultures exposed to smoke and not in confluent cultures. Western blot analysis demonstrated ERK activation in both confluent and subconfluent cultures after CSE. However, activation of apoptosis signal-regulating kinase 1 (ASK1), JNK, and p38 were demonstrated only in subconfluent cultures and not in confluent cultures after CSE. Using short interfering RNA (siRNA) to JNK1 and JNK2 and a JNK inhibitor, we attenuated CSE-mediated cell death in subconfluent cultures but not with an inhibitor of the p38 pathway. Using the tetracycline (Tet)-on inducible approach, overexpression of thioredoxin (TRX) attenuated CSE-mediated cell death and JNK activation in subconfluent cultures. These results suggest that the TRX-ASK1-JNK pathway may play a critical role in mediating cell density-dependent CSE cytotoxicity.

  16. Quorum sensing and density-dependent dispersal in an aquatic model system.

    Directory of Open Access Journals (Sweden)

    Simon Fellous

    Full Text Available Many organisms use cues to decide whether to disperse or not, especially those related to the composition of their environment. Dispersal hence sometimes depends on population density, which can be important for the dynamics and evolution of sub-divided populations. But very little is known about the factors that organisms use to inform their dispersal decision. We investigated the cues underlying density-dependent dispersal in inter-connected microcosms of the freshwater protozoan Paramecium caudatum. In two experiments, we manipulated (i the number of cells per microcosm and (ii the origin of their culture medium (supernatant from high- or low-density populations. We found a negative relationship between population density and rates of dispersal, suggesting the use of physical cues. There was no significant effect of culture medium origin on dispersal and thus no support for chemical cues usage. These results suggest that the perception of density - and as a result, the decision to disperse - in this organism can be based on physical factors. This type of quorum sensing may be an adaptation optimizing small scale monitoring of the environment and swarm formation in open water.

  17. A multiwell platform for studying stiffness-dependent cell biology.

    Science.gov (United States)

    Mih, Justin D; Sharif, Asma S; Liu, Fei; Marinkovic, Aleksandar; Symer, Matthew M; Tschumperlin, Daniel J

    2011-01-01

    Adherent cells are typically cultured on rigid substrates that are orders of magnitude stiffer than their tissue of origin. Here, we describe a method to rapidly fabricate 96 and 384 well platforms for routine screening of cells in tissue-relevant stiffness contexts. Briefly, polyacrylamide (PA) hydrogels are cast in glass-bottom plates, functionalized with collagen, and sterilized for cell culture. The Young's modulus of each substrate can be specified from 0.3 to 55 kPa, with collagen surface density held constant over the stiffness range. Using automated fluorescence microscopy, we captured the morphological variations of 7 cell types cultured across a physiological range of stiffness within a 384 well plate. We performed assays of cell number, proliferation, and apoptosis in 96 wells and resolved distinct profiles of cell growth as a function of stiffness among primary and immortalized cell lines. We found that the stiffness-dependent growth of normal human lung fibroblasts is largely invariant with collagen density, and that differences in their accumulation are amplified by increasing serum concentration. Further, we performed a screen of 18 bioactive small molecules and identified compounds with enhanced or reduced effects on soft versus rigid substrates, including blebbistatin, which abolished the suppression of lung fibroblast growth at 1 kPa. The ability to deploy PA gels in multiwell plates for high throughput analysis of cells in tissue-relevant environments opens new opportunities for the discovery of cellular responses that operate in specific stiffness regimes.

  18. A multiwell platform for studying stiffness-dependent cell biology.

    Directory of Open Access Journals (Sweden)

    Justin D Mih

    Full Text Available Adherent cells are typically cultured on rigid substrates that are orders of magnitude stiffer than their tissue of origin. Here, we describe a method to rapidly fabricate 96 and 384 well platforms for routine screening of cells in tissue-relevant stiffness contexts. Briefly, polyacrylamide (PA hydrogels are cast in glass-bottom plates, functionalized with collagen, and sterilized for cell culture. The Young's modulus of each substrate can be specified from 0.3 to 55 kPa, with collagen surface density held constant over the stiffness range. Using automated fluorescence microscopy, we captured the morphological variations of 7 cell types cultured across a physiological range of stiffness within a 384 well plate. We performed assays of cell number, proliferation, and apoptosis in 96 wells and resolved distinct profiles of cell growth as a function of stiffness among primary and immortalized cell lines. We found that the stiffness-dependent growth of normal human lung fibroblasts is largely invariant with collagen density, and that differences in their accumulation are amplified by increasing serum concentration. Further, we performed a screen of 18 bioactive small molecules and identified compounds with enhanced or reduced effects on soft versus rigid substrates, including blebbistatin, which abolished the suppression of lung fibroblast growth at 1 kPa. The ability to deploy PA gels in multiwell plates for high throughput analysis of cells in tissue-relevant environments opens new opportunities for the discovery of cellular responses that operate in specific stiffness regimes.

  19. Nuclear symmetry energy in density dependent hadronic models

    International Nuclear Information System (INIS)

    Haddad, S.

    2008-12-01

    The density dependence of the symmetry energy and the correlation between parameters of the symmetry energy and the neutron skin thickness in the nucleus 208 Pb are investigated in relativistic Hadronic models. The dependency of the symmetry energy on density is linear around saturation density. Correlation exists between the neutron skin thickness in the nucleus 208 Pb and the value of the nuclear symmetry energy at saturation density, but not with the slope of the symmetry energy at saturation density. (author)

  20. Advanced nickel/hydrogen dependent pressure vessel (DPV) cell and battery concepts

    Energy Technology Data Exchange (ETDEWEB)

    Caldwell, D.B. [Technologies Div., Eagle Picher Industries, Inc., Joplin, MO (United States); Fox, C.L. [Technologies Div., Eagle Picher Industries, Inc., Joplin, MO (United States); Miller, L.E. [Technologies Div., Eagle Picher Industries, Inc., Joplin, MO (United States)

    1997-03-01

    The dependent pressure vessel (DPV) nickel/hydrogen (NiH{sub 2}) design is being developed by Eagle-Picher industries, Inc. (EPI) as an advanced battery for military and commercial aerospace and terrestrial applications. The DPV cell design offers high specific energy and energy density as well as reduced cost, while retaining the established individual pressure vessel (IPV) technology, flight heritage and database. This advanced DPV design also offers a more efficient mechanical, electrical and thermal cell and battery configuration and a reduced parts count. The DPV battery design promotes compact, minimum volume packaging and weight efficiency, and delivers cost and weight savings with minimal design risks. (orig.)

  1. Regulatory domain selectivity in the cell-type specific PKN-dependence of cell migration.

    Directory of Open Access Journals (Sweden)

    Sylvie Lachmann

    Full Text Available The mammalian protein kinase N (PKN family of Serine/Threonine kinases comprises three isoforms, which are targets for Rho family GTPases. Small GTPases are major regulators of the cellular cytoskeleton, generating interest in the role(s of specific PKN isoforms in processes such as cell migration and invasion. It has been reported that PKN3 is required for prostate tumour cell invasion but not PKN1 or 2. Here we employ a cell model, the 5637 bladder tumour cell line where PKN2 is relatively highly expressed, to assess the potential redundancy of these isoforms in migratory responses. It is established that PKN2 has a critical role in the migration and invasion of these cells. Furthermore, using a PKN wild-type and chimera rescue strategy, it is shown that PKN isoforms are not simply redundant in supporting migration, but appear to be linked through isoform specific regulatory domain properties to selective upstream signals. It is concluded that intervention in PKNs may need to be directed at multiple isoforms to be effective in different cell types.

  2. Regulatory domain selectivity in the cell-type specific PKN-dependence of cell migration.

    Science.gov (United States)

    Lachmann, Sylvie; Jevons, Amy; De Rycker, Manu; Casamassima, Adele; Radtke, Simone; Collazos, Alejandra; Parker, Peter J

    2011-01-01

    The mammalian protein kinase N (PKN) family of Serine/Threonine kinases comprises three isoforms, which are targets for Rho family GTPases. Small GTPases are major regulators of the cellular cytoskeleton, generating interest in the role(s) of specific PKN isoforms in processes such as cell migration and invasion. It has been reported that PKN3 is required for prostate tumour cell invasion but not PKN1 or 2. Here we employ a cell model, the 5637 bladder tumour cell line where PKN2 is relatively highly expressed, to assess the potential redundancy of these isoforms in migratory responses. It is established that PKN2 has a critical role in the migration and invasion of these cells. Furthermore, using a PKN wild-type and chimera rescue strategy, it is shown that PKN isoforms are not simply redundant in supporting migration, but appear to be linked through isoform specific regulatory domain properties to selective upstream signals. It is concluded that intervention in PKNs may need to be directed at multiple isoforms to be effective in different cell types.

  3. Prefrontal cortical parvalbumin and somatostatin expression and cell density increase during adolescence and are modified by BDNF and sex.

    Science.gov (United States)

    Du, X; Serena, K; Hwang, W; Grech, A M; Wu, Y W C; Schroeder, A; Hill, R A

    2018-04-01

    Brain-derived neurotrophic factor (BDNF) is known to play a critical role early in the development of cortical GABAergic interneurons. Recently our laboratory and others have shown protracted development of specific subpopulations of GABAergic interneurons extending into adolescence. BDNF expression also changes significantly across adolescent development. However the role of BDNF in regulating GABAergic changes across adolescence remains unclear. Here, we performed a week-by-week analysis of the protein expression and cell density of three major GABAergic interneurons, parvalbumin (PV), somatostatin (SST) and calretinin (Cal) in the medial prefrontal cortex from prepubescence (week 3) to adulthood (week 12). In order to assess how BDNF and sex might influence the adolescent trajectory of GABAergic interneurons we compared WT as well as BDNF heterozygous (+/-) male and female mice. In both males and females PV expression increases during adolescent development in the mPFC. Compared to wild-types, PV expression was reduced in male but not female BDNF+/- mice throughout adolescent development. This reduction in protein expression corresponded with reduced cell density, specifically within the infralimbic prefrontal cortex. SST expression increased in early adolescent WT females and this upregulation was delayed in BDNF+/-. SST cell density also increased in early adolescent mPFC of WT female mice, with BDNF+/- again showing a reduced pattern of expression. Cal protein expression was also sex-dependently altered across adolescence with WT males showing a steady decline but that of BDNF+/- remaining unaltered. Reduced cell density in on the other hand was observed particularly in male BDNF+/- mice. In females, Cal protein expression and cell density remained largely stable. Our results show that PV, SST and calretinin interneurons are indeed still developing into early adolescence in the mPFC and that BDNF plays a critical, sex-specific role in mediating expression and

  4. Microfluidic engineered high cell density three-dimensional neural cultures

    Science.gov (United States)

    Cullen, D. Kacy; Vukasinovic, Jelena; Glezer, Ari; La Placa, Michelle C.

    2007-06-01

    Three-dimensional (3D) neural cultures with cells distributed throughout a thick, bioactive protein scaffold may better represent neurobiological phenomena than planar correlates lacking matrix support. Neural cells in vivo interact within a complex, multicellular environment with tightly coupled 3D cell-cell/cell-matrix interactions; however, thick 3D neural cultures at cell densities approaching that of brain rapidly decay, presumably due to diffusion limited interstitial mass transport. To address this issue, we have developed a novel perfusion platform that utilizes forced intercellular convection to enhance mass transport. First, we demonstrated that in thick (>500 µm) 3D neural cultures supported by passive diffusion, cell densities =104 cells mm-3), continuous medium perfusion at 2.0-11.0 µL min-1 improved viability compared to non-perfused cultures (p death and matrix degradation. In perfused cultures, survival was dependent on proximity to the perfusion source at 2.00-6.25 µL min-1 (p 90% viability in both neuronal cultures and neuronal-astrocytic co-cultures. This work demonstrates the utility of forced interstitial convection in improving the survival of high cell density 3D engineered neural constructs and may aid in the development of novel tissue-engineered systems reconstituting 3D cell-cell/cell-matrix interactions.

  5. Critical Assessment of Time-Dependent Density Functional Theory for Excited States of Open-Shell Systems: II. Doublet-Quartet Transitions.

    Science.gov (United States)

    Li, Zhendong; Liu, Wenjian

    2016-06-14

    Compared with closed-shell systems, open-shell systems place three additional challenges to time-dependent density functional theory (TD-DFT) for electronically excited states: (a) the spin-contamination problem is a serious issue; (b) the exchange-correlation (XC) kernel may be numerically instable; and (c) the single-determinant description of open-shell ground states readily becomes energetically instable. Confined to flip-up single excitations, the spin-contamination problem can largely be avoided by using the spin-flip TD-DFT (SF-TD-DFT) formalism, provided that a noncollinear XC kernel is employed. As for the numerical instabilities associated with such a kernel, only an ad hoc scheme has been proposed so far, viz., the ALDA0 kernel, which amounts to setting the divergent components (arising from density gradients and kinetic energy density) simply to zero. The ground-state instability problem can effectively be avoided by introducing the Tamm-Dancoff approximation (TDA) to TD-DFT. Therefore, on a general basis, the SF-TDA/ALDA0 Ansatz is so far the only promising means within the TD-DFT framework for flip-up single excitations of open-shell systems. To assess systematically the performance of SF-TDA/ALDA0, in total 61 low-lying quartet excited states of the benchmark set of 11 small radicals [J. Chem. Theory Comput. 2016, 12, 238] are investigated with various XC functionals. Taking the MRCISD+Q (multireference configuration interaction with singles and doubles plus the Davidson correction) results as benchmark, it is found that the mean absolute errors of SF-TDA/ALDA0 with the SAOP (statistical averaging of model orbital potentials), global hybrid, and range-separated hybrid functionals are in the range of 0.2-0.4 eV. This is in line not only with the typical accuracy of TD-DFT for singlet and triplet excited states of closed-shell systems but also with the gross accuracy of spin-adapted TD-DFT for spin-conserving excited states of open-shell systems.

  6. Natural excitation orbitals from linear response theories : Time-dependent density functional theory, time-dependent Hartree-Fock, and time-dependent natural orbital functional theory

    NARCIS (Netherlands)

    Van Meer, R.; Gritsenko, O. V.; Baerends, E. J.

    2017-01-01

    Straightforward interpretation of excitations is possible if they can be described as simple single orbital-to-orbital (or double, etc.) transitions. In linear response time-dependent density functional theory (LR-TDDFT), the (ground state) Kohn-Sham orbitals prove to be such an orbital basis. In

  7. Density-Dependent Phase Polyphenism in Nonmodel Locusts: A Minireview

    Directory of Open Access Journals (Sweden)

    Hojun Song

    2011-01-01

    Full Text Available Although the specific mechanisms of locust phase transformation are wellunderstood for model locust species such as the desert locust Schistocerca gregaria and the migratory locust Locusta migratoria, the expressions of density-dependent phase polyphenism in other nonmodel locust species are not wellknown. The present paper is an attempt to review and synthesize what we know about these nonmodel locusts. Based on all available data, I find that locust phase polyphenism is expressed in many different ways in different locust species and identify a pattern that locust species often belong to large taxonomic groups which contain mostly nonswarming grasshopper species. Although locust phase polyphenism has evolved multiple times within Acrididae, I argue that its evolution should be studied from a phylogenetic perspective because I find similar density-dependent phenotypic plasticity among closely related species. Finally, I emphasize the importance of comparative analyses in understanding the evolution of locust phase and propose a phylogeny-based research framework.

  8. The ideal free distribution as an evolutionarily stable state in density-dependent population games

    Czech Academy of Sciences Publication Activity Database

    Cressman, R.; Křivan, Vlastimil

    2010-01-01

    Roč. 119, č. 8 (2010), s. 1231-1242 ISSN 0030-1299 R&D Projects: GA AV ČR IAA100070601 Institutional research plan: CEZ:AV0Z50070508 Keywords : density-dependent population games Subject RIV: EH - Ecology, Behaviour Impact factor: 3.393, year: 2010

  9. Is contextual-potentiated eating dependent on caloric density of food?

    Directory of Open Access Journals (Sweden)

    Fernando Fernández-Aranda

    2009-01-01

    Full Text Available One experiment tested whether a specific context could elicit eating in rats as a result of Pavlovian conditioning and whether this effect depended on the caloric density of food. Thirty two deprived rats experienced two contexts. They had access to food in context A, but no food was available in context B. During conditioning, half of the animals received high density caloric food (HD groups whereas the other half, low density caloric food (LD groups. Then, half of the rats in each type of food group was tested in context A and the other half in context B. The results demonstrated an effect of context conditioning only in HD groups. These findings suggest the relevance of both contextual conditioning and caloric density of food in eating behaviour. Implications for the aetiology of binge eating will be discussed.

  10. Density dependent effective interactions

    International Nuclear Information System (INIS)

    Dortmans, P.J.; Amos, K.

    1994-01-01

    An effective nucleon-nucleon interaction is defined by an optimal fit to select on-and half-off-of-the-energy shell t-and g-matrices determined by solutions of the Lippmann-Schwinger and Brueckner-Bethe-Goldstone equations with the Paris nucleon-nucleon interaction as input. As such, it is seen to better reproduce the interaction on which it is based than other commonly used density dependent effective interactions. The new (medium modified) effective interaction when folded with appropriate density matrices, has been used to define proton- 12 C and proton- 16 O optical potentials. With them elastic scattering data are well fit and the medium effects identifiable. 23 refs., 8 figs

  11. Multi-configuration time-dependent density-functional theory based on range separation

    DEFF Research Database (Denmark)

    Fromager, E.; Knecht, S.; Jensen, Hans Jørgen Aagaard

    2013-01-01

    Multi-configuration range-separated density-functional theory is extended to the time-dependent regime. An exact variational formulation is derived. The approximation, which consists in combining a long-range Multi-Configuration- Self-Consistent Field (MCSCF) treatment with an adiabatic short...... (srGGA) approximations. As expected, when modeling long-range interactions with the MCSCF model instead of the adiabatic Buijse-Baerends density-matrix functional as recently proposed by Pernal [J. Chem. Phys. 136, 184105 (2012)10.1063/1.4712019], the description of both the 1D doubly-excited state...

  12. Cell density signal protein suitable for treatment of connective tissue injuries and defects

    Science.gov (United States)

    Schwarz, Richard I.

    2002-08-13

    Identification, isolation and partial sequencing of a cell density protein produced by fibroblastic cells. The cell density signal protein comprising a 14 amino acid peptide or a fragment, variant, mutant or analog thereof, the deduced cDNA sequence from the 14 amino acid peptide, a recombinant protein, protein and peptide-specific antibodies, and the use of the peptide and peptide-specific antibodies as therapeutic agents for regulation of cell differentiation and proliferation. A method for treatment and repair of connective tissue and tendon injuries, collagen deficiency, and connective tissue defects.

  13. Age-dependent tissue-specific exposure of cell phone users

    Energy Technology Data Exchange (ETDEWEB)

    Christ, Andreas; Gosselin, Marie-Christine; Kuehn, Sven; Kuster, Niels [Foundation for Research on Information Technologies in Society (IT' IS), Zeughausstr. 43, 8004 Zuerich (Switzerland); Christopoulou, Maria [National Technical University of Athens, School of Electrical and Computer Engineering, 9 Iroon Polytechniou Str., 15780 Athens (Greece)], E-mail: christ@itis.ethz.ch

    2010-04-07

    The peak spatial specific absorption rate (SAR) assessed with the standardized specific anthropometric mannequin head phantom has been shown to yield a conservative exposure estimate for both adults and children using mobile phones. There are, however, questions remaining concerning the impact of age-dependent dielectric tissue properties and age-dependent proportions of the skull, face and ear on the global and local absorption, in particular in the brain tissues. In this study, we compare the absorption in various parts of the cortex for different magnetic resonance imaging-based head phantoms of adults and children exposed to different models of mobile phones. The results show that the locally induced fields in children can be significantly higher (>3 dB) in subregions of the brain (cortex, hippocampus and hypothalamus) and the eye due to the closer proximity of the phone to these tissues. The increase is even larger for bone marrow (>10 dB) as a result of its significantly high conductivity. Tissues such as the pineal gland show no increase since their distances to the phone are not a function of age. This study, however, confirms previous findings saying that there are no age-dependent changes of the peak spatial SAR when averaged over the entire head.

  14. Age-dependent tissue-specific exposure of cell phone users

    International Nuclear Information System (INIS)

    Christ, Andreas; Gosselin, Marie-Christine; Kuehn, Sven; Kuster, Niels; Christopoulou, Maria

    2010-01-01

    The peak spatial specific absorption rate (SAR) assessed with the standardized specific anthropometric mannequin head phantom has been shown to yield a conservative exposure estimate for both adults and children using mobile phones. There are, however, questions remaining concerning the impact of age-dependent dielectric tissue properties and age-dependent proportions of the skull, face and ear on the global and local absorption, in particular in the brain tissues. In this study, we compare the absorption in various parts of the cortex for different magnetic resonance imaging-based head phantoms of adults and children exposed to different models of mobile phones. The results show that the locally induced fields in children can be significantly higher (>3 dB) in subregions of the brain (cortex, hippocampus and hypothalamus) and the eye due to the closer proximity of the phone to these tissues. The increase is even larger for bone marrow (>10 dB) as a result of its significantly high conductivity. Tissues such as the pineal gland show no increase since their distances to the phone are not a function of age. This study, however, confirms previous findings saying that there are no age-dependent changes of the peak spatial SAR when averaged over the entire head.

  15. Possibility of ΛΛ pairing and its dependence on background density in a relativistic Hartree-Bogoliubov model

    International Nuclear Information System (INIS)

    Tanigawa, Tomonori; Matsuzaki, Masayuki; Chiba, Satoshi

    2003-01-01

    We calculate a ΛΛ pairing gap in binary mixed matter of nucleons and Λ hyperons within the relativistic Hartree-Bogoliubov model. Λ hyperons to be paired up are immersed in background nucleons in a normal state. The gap is calculated with a one-boson-exchange interaction obtained from a relativistic Lagrangian. It is found that at background density ρ N =2.5ρ 0 the ΛΛ pairing gap is very small, and that a denser background makes it rapidly suppressed. This result suggests a mechanism, specific to mixed matter dealt with relativistic models, of its dependence on the nucleon density. An effect of weaker ΛΛ attraction on the gap is also examined in connection with the revised information of the ΛΛ interaction

  16. A high parasite density environment induces transcriptional changes and cell death in Plasmodium falciparum blood stages.

    Science.gov (United States)

    Chou, Evelyn S; Abidi, Sabia Z; Teye, Marian; Leliwa-Sytek, Aleksandra; Rask, Thomas S; Cobbold, Simon A; Tonkin-Hill, Gerry Q; Subramaniam, Krishanthi S; Sexton, Anna E; Creek, Darren J; Daily, Johanna P; Duffy, Michael F; Day, Karen P

    2018-03-01

    Transient regulation of Plasmodium numbers below the density that induces fever has been observed in chronic malaria infections in humans. This species transcending control cannot be explained by immunity alone. Using an in vitro system we have observed density dependent regulation of malaria population size as a mechanism to possibly explain these in vivo observations. Specifically, Plasmodium falciparum blood stages from a high but not low-density environment exhibited unique phenotypic changes during the late trophozoite (LT) and schizont stages of the intraerythrocytic cycle. These included in order of appearance: failure of schizonts to mature and merozoites to replicate, apoptotic-like morphological changes including shrinking, loss of mitochondrial membrane potential, and blebbing with eventual release of aberrant parasites from infected erythrocytes. This unique death phenotype was triggered in a stage-specific manner by sensing of a high-density culture environment. Conditions of glucose starvation, nutrient depletion, and high lactate could not induce the phenotype. A high-density culture environment induced rapid global changes in the parasite transcriptome including differential expression of genes involved in cell remodeling, clonal antigenic variation, metabolism, and cell death pathways including an apoptosis-associated metacaspase gene. This transcriptional profile was also characterized by concomitant expression of asexual and sexual stage-specific genes. The data show strong evidence to support our hypothesis that density sensing exists in P. falciparum. They indicate that an apoptotic-like mechanism may play a role in P. falciparum density regulation, which, as in yeast, has features quite distinguishable from mammalian apoptosis. Gene expression data are available in the GEO databases under the accession number GSE91188. © 2017 Federation of European Biochemical Societies.

  17. XES studies of density of states of high temperature superconductors

    Science.gov (United States)

    Jasiolek, Gabriel

    1991-01-01

    X-ray emission spectroscopic studies concerning the superconducting crystals, thin films, and ceramics of the Y-Ba-Cu-O, Tm-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Bi-Pb-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O types are presented. The contributions of the 13d(9)L, 13d(10)L, 13d(10)LL, and 13d(10)L(2) configurations, where L denotes a ligand hole at the oxygen orbitals in the spectroscopic pattern of these superconductors are discussed. An attempt to connect the x-ray 'as registered' Cu L(alpha) emission spectra with the density of states close to the Fermi level, considering an influence of the CuL3 absorption edge, is presented. The corrected intensity distributions below the Fermi level are found to correspond to the theoretical density of states. Furthermore, an approach to the average valence of copper basing on the account of the self-absorption and fluorescence effects and on the configurations listed above is shown. The average valence of copper in the materials investigated is estimated to lie in the range of +2.10 to 2.32 when the formal trivalent copper is considered as that characterized by the 13d(9)L configuration. The density of states at the Fermi level was estimated to be 2.4 states/eV-cell for a Bi-Sr-Ca-Cu-O crystal and 3.6 states/eV-cell for a Tl-Ba-Ca-CU-O ceramic.

  18. Element-specific density profiles in interacting biomembrane models

    International Nuclear Information System (INIS)

    Schneck, Emanuel; Rodriguez-Loureiro, Ignacio; Bertinetti, Luca; Gochev, Georgi; Marin, Egor; Novikov, Dmitri; Konovalov, Oleg

    2017-01-01

    Surface interactions involving biomembranes, such as cell–cell interactions or membrane contacts inside cells play important roles in numerous biological processes. Structural insight into the interacting surfaces is a prerequisite to understand the interaction characteristics as well as the underlying physical mechanisms. Here, we work with simplified planar experimental models of membrane surfaces, composed of lipids and lipopolymers. Their interaction is quantified in terms of pressure–distance curves using ellipsometry at controlled dehydrating (interaction) pressures. For selected pressures, their internal structure is investigated by standing-wave x-ray fluorescence (SWXF). This technique yields specific density profiles of the chemical elements P and S belonging to lipid headgroups and polymer chains, as well as counter-ion profiles for charged surfaces. (paper)

  19. Deletion of Batf3-dependent antigen-presenting cells does not affect atherosclerotic lesion formation in mice.

    Directory of Open Access Journals (Sweden)

    Jesus Gil-Pulido

    Full Text Available Atherosclerosis is the main underlying cause for cardiovascular events such as myocardial infarction and stroke and its development might be influenced by immune cells. Dendritic cells (DCs bridge innate and adaptive immune responses by presenting antigens to T cells and releasing a variety of cytokines. Several subsets of DCs can be discriminated that engage specific transcriptional pathways for their development. Basic leucine zipper transcription factor ATF-like 3 (Batf3 is required for the development of classical CD8α+ and CD103+ DCs. By crossing mice deficient in Batf3 with atherosclerosis-prone low density lipoprotein receptor (Ldlr-/--deficient mice we here aimed to further address the contribution of Batf3-dependent CD8α+ and CD103+ antigen-presenting cells to atherosclerosis. We demonstrate that deficiency in Batf3 entailed mild effects on the immune response in the spleen but did not alter atherosclerotic lesion formation in the aorta or aortic root, nor affected plaque phenotype in low density lipoprotein receptor-deficient mice fed a high fat diet. We thus provide evidence that Batf3-dependent antigen-presenting cells do not have a prominent role in atherosclerosis.

  20. Nuclear spectroscopy with density dependent effective interactions

    International Nuclear Information System (INIS)

    Krewald, S.

    1976-07-01

    The paper investigates excited nuclear states with density-dependent effective interactions. In the first part of the paper, the structure and the width of the multipole giant resonances discovered in 1972 are derived microscopically. Because of their high excitation energy, these giant resonances are unstable to particle emission and thus often have a considerable decay width. Due to their collective structure, the giant resonances can be described by RPA in good approximation. In this paper, the continuum RPA is applied to the spherical nuclei 16 O, 40 Ca, 90 Zr and 208 Pb. The experimental centroid energy are in very good agreement with the calculations performed in the paper. (orig./WL) [de

  1. Laminin-dependent and laminin-independent adhesion of human melanoma cells to sulfatides

    DEFF Research Database (Denmark)

    Roberts, D D; Wewer, U M; Liotta, L A

    1988-01-01

    Sulfatides (galactosylceramide-I3-sulfate) but not neutral glycolipids or gangliosides adsorbed on plastic promote adhesion of the human melanoma cell line G361. Direct adhesion of G361 cells requires densities of sulfatide greater than 1 pmol/mm2. In the presence of laminin, however, specific...... adhesion of G361 cells to sulfatide or seminolipid (galactosylalkylacyl-glycerol-I3-sulfate) but not to other lipids is strongly stimulated and requires only 25 fmol/mm2 of adsorbed lipid. The effects of laminin and sulfatide on adhesion are synergistic, suggesting that laminin is mediating adhesion...... by cross-linking receptors on the melanoma cell surface to sulfatide adsorbed on the plastic. Although thrombospondin binds to sulfatides and G361 cells, it does not enhance, but rather inhibits direct and laminin-dependent G361 cell adhesion to sulfatide. In contrast, C32 melanoma cells also adhere...

  2. High power density yeast catalyzed microbial fuel cells

    Science.gov (United States)

    Ganguli, Rahul

    Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density

  3. Hot-electron-assisted femtochemistry at surfaces: A time-dependent density functional theory approach

    DEFF Research Database (Denmark)

    Gavnholt, Jeppe; Rubio, Angel; Olsen, Thomas

    2009-01-01

    Using time-evolution time-dependent density functional theory (TDDFT) within the adiabatic local-density approximation, we study the interactions between single electrons and molecular resonances at surfaces. Our system is a nitrogen molecule adsorbed on a ruthenium surface. The surface is modele...... resonance and the lowering of the resonance energy due to an image charge effect. Finally we apply the TDDFT procedure to only consider the decay of molecular excitations and find that it agrees quite well with the width of the projected density of Kohn-Sham states....

  4. Excited-state density functional theory

    International Nuclear Information System (INIS)

    Harbola, Manoj K; Hemanadhan, M; Shamim, Md; Samal, P

    2012-01-01

    Starting with a brief introduction to excited-state density functional theory, we present our method of constructing modified local density approximated (MLDA) energy functionals for the excited states. We show that these functionals give accurate results for kinetic energy and exchange energy compared to the ground state LDA functionals. Further, with the inclusion of GGA correction, highly accurate total energies for excited states are obtained. We conclude with a brief discussion on the further direction of research that include the construction of correlation energy functional and exchange potential for excited states.

  5. Ground-state densities from the Rayleigh-Ritz variation principle and from density-functional theory.

    Science.gov (United States)

    Kvaal, Simen; Helgaker, Trygve

    2015-11-14

    The relationship between the densities of ground-state wave functions (i.e., the minimizers of the Rayleigh-Ritz variation principle) and the ground-state densities in density-functional theory (i.e., the minimizers of the Hohenberg-Kohn variation principle) is studied within the framework of convex conjugation, in a generic setting covering molecular systems, solid-state systems, and more. Having introduced admissible density functionals as functionals that produce the exact ground-state energy for a given external potential by minimizing over densities in the Hohenberg-Kohn variation principle, necessary and sufficient conditions on such functionals are established to ensure that the Rayleigh-Ritz ground-state densities and the Hohenberg-Kohn ground-state densities are identical. We apply the results to molecular systems in the Born-Oppenheimer approximation. For any given potential v ∈ L(3/2)(ℝ(3)) + L(∞)(ℝ(3)), we establish a one-to-one correspondence between the mixed ground-state densities of the Rayleigh-Ritz variation principle and the mixed ground-state densities of the Hohenberg-Kohn variation principle when the Lieb density-matrix constrained-search universal density functional is taken as the admissible functional. A similar one-to-one correspondence is established between the pure ground-state densities of the Rayleigh-Ritz variation principle and the pure ground-state densities obtained using the Hohenberg-Kohn variation principle with the Levy-Lieb pure-state constrained-search functional. In other words, all physical ground-state densities (pure or mixed) are recovered with these functionals and no false densities (i.e., minimizing densities that are not physical) exist. The importance of topology (i.e., choice of Banach space of densities and potentials) is emphasized and illustrated. The relevance of these results for current-density-functional theory is examined.

  6. Multicomponent Time-Dependent Density Functional Theory: Proton and Electron Excitation Energies.

    Science.gov (United States)

    Yang, Yang; Culpitt, Tanner; Hammes-Schiffer, Sharon

    2018-04-05

    The quantum mechanical treatment of both electrons and protons in the calculation of excited state properties is critical for describing nonadiabatic processes such as photoinduced proton-coupled electron transfer. Multicomponent density functional theory enables the consistent quantum mechanical treatment of more than one type of particle and has been implemented previously for studying ground state molecular properties within the nuclear-electronic orbital (NEO) framework, where all electrons and specified protons are treated quantum mechanically. To enable the study of excited state molecular properties, herein the linear response multicomponent time-dependent density functional theory (TDDFT) is derived and implemented within the NEO framework. Initial applications to FHF - and HCN illustrate that NEO-TDDFT provides accurate proton and electron excitation energies within a single calculation. As its computational cost is similar to that of conventional electronic TDDFT, the NEO-TDDFT approach is promising for diverse applications, particularly nonadiabatic proton transfer reactions, which may exhibit mixed electron-proton vibronic excitations.

  7. Cdc42-mediated tubulogenesis controls cell specification

    DEFF Research Database (Denmark)

    Kesavan, Gokul; Sand, Fredrik Wolfhagen; Greiner, Thomas Uwe

    2009-01-01

    Understanding how cells polarize and coordinate tubulogenesis during organ formation is a central question in biology. Tubulogenesis often coincides with cell-lineage specification during organ development. Hence, an elementary question is whether these two processes are independently controlled......, or whether proper cell specification depends on formation of tubes. To address these fundamental questions, we have studied the functional role of Cdc42 in pancreatic tubulogenesis. We present evidence that Cdc42 is essential for tube formation, specifically for initiating microlumen formation and later...... for maintaining apical cell polarity. Finally, we show that Cdc42 controls cell specification non-cell-autonomously by providing the correct microenvironment for proper control of cell-fate choices of multipotent progenitors. For a video summary of this article, see the PaperFlick file with the Supplemental Data...

  8. High cell density strategy for poly(3-hydroxybutyrate production by Cupriavidus necator

    Directory of Open Access Journals (Sweden)

    J. L. Ienczak

    2011-12-01

    Full Text Available Poly(3-hydroxybutyrate (P(3HB is a carbon and intracellular storage source for different microorganisms and its production can achieve high productivities by means of high cell density cultures. The aim of this study was to propose a high cell density strategy for P(3HB production by Cupriavidus necator. The exponential growth phase demands an accurate control of the oxygen transfer system in the bioreactor, due to maximum specific growth rate (µXr, and, consequently, a maximum specific oxygen uptake rate (QO2, in addition to significant residual biomass (Xr growth in high cell density cultures. In this context, this work investigated the strategy for obtaining high cell density, with the inclusion of a linear growth phase for P(3HB production by C. necator in a fed-batch culture. The linear growth phase was included between the exponential growth phase and the P(3HB production phase as a strategy to reduce the specific growth rate (µXr and specific oxygen uptake rate (QO2, with constant residual biomass growth rate (d(V.Xr/dt = k = constant and linear increase of biomass. Three strategies of culture were performed. The results showed that a high residual biomass concentration (30 gXr.L-1 can be reached by the inclusion of the linear growth strategy and specific growth rates (µXr between 0.08 and 0.05 h-1, at the beginning of the production phase, are necessary to attain a high P(3HB productivity.

  9. An Intraoperative Site-specific Bone Density Device: A Pilot Test Case.

    Science.gov (United States)

    Arosio, Paolo; Moschioni, Monica; Banfi, Luca Maria; Di Stefano, Anilo Alessio

    2015-08-01

    This paper reports a case of all-on-four rehabilitation where bone density at implant sites was assessed both through preoperative computed tomographic (CT) scans and using a micromotor working as an intraoperative bone density measurement device. Implant-supported rehabilitation is a predictable treatment option for tooth replacement whose success depends on the clinician's experience, the implant characteristics and location and patient-related factors. Among the latter, bone density is a determinant for the achievement of primary implant stability and, eventually, for implant success. The ability to measure bone density at the placement site before implant insertion could be important in the clinical setting. A patient complaining of masticatory impairment was presented with a plan calling for extraction of all her compromised teeth, followed by implant rehabilitation. A week before surgery, she underwent CT examination, and the bone density on the CT scans was measured. When the implant osteotomies were created, the bone density was again measured with a micromotor endowed with an instantaneous torque-measuring system. The implant placement protocols were adapted for each implant, according to the intraoperative measurements, and the patient was rehabilitated following an all-on-four immediate loading protocol. The bone density device provided valuable information beyond that obtained from CT scans, allowing for site-specific, intraoperative assessment of bone density immediately before implant placement and an estimation of primary stability just after implant insertion. Measuring jaw-bone density could help clinicians to select implant-placement protocols and loading strategies based on site-specific bone features.

  10. Relativistic Random-Phase Approximation with Density-dependent Meson-nucleon Couplings at Finite Temperature

    International Nuclear Information System (INIS)

    Niu, Y.; Paar, N.; Vretenar, D.; Meng, J.

    2009-01-01

    The fully self-consistent relativistic random-phase approximation (RRPA) framework based on effective interactions with a phenomenological density dependence is extended to finite temperatures. The RRPA configuration space is built from the spectrum of single-nucleon states at finite temperature obtained by the temperature dependent relativistic mean field (RMF-T) theory based on effective Lagrangian with density dependent meson-nucleon vertex functions. As an illustration, the dependence of binding energy, radius, entropy and single particle levels on temperature for spherical nucleus 2 08P b is investigated in RMF-T theory. The finite temperature RRPA has been employed in studies of giant monopole and dipole resonances, and the evolution of resonance properties has been studied as a function of temperature. In addition, exotic modes of excitation have been systematically explored at finite temperatures, with an emphasis on the case of pygmy dipole resonances.(author)

  11. Nuclear matter studies with density-dependent meson-nucleon coupling constants

    International Nuclear Information System (INIS)

    Banerjee, M.K.; Tjon, J.A.; Banerjee, M.K.; Tjon, J.A.

    1997-01-01

    Due to the internal structure of the nucleon, we should expect, in general, that the effective meson nucleon parameters may change in nuclear medium. We study such changes by using a chiral confining model of the nucleon. We use density-dependent masses for all mesons except the pion. Within a Dirac-Brueckner analysis, based on the relativistic covariant structure of the NN amplitude, we show that the effect of such a density dependence in the NN interaction on the saturation properties of nuclear matter, while not large, is quite significant. Due to the density dependence of the g σNN , as predicted by the chiral confining model, we find, in particular, a looping behavior of the binding energy at saturation as a function of the saturation density. A simple model is described, which exhibits looping and which is shown to be mainly caused by the presence of a peak in the density dependence of the medium modified σN coupling constant at low density. The effect of density dependence of the coupling constants and the meson masses tends to improve the results for E/A and density of nuclear matter at saturation. From the present study we see that the relationship between binding energy and saturation density may not be as universal as found in nonrelativistic studies and that more model dependence is exhibited once medium modifications of the basic nuclear interactions are considered. copyright 1997 The American Physical Society

  12. Perspective: Fundamental aspects of time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Maitra, Neepa T. [Department of Physics and Astronomy, Hunter College and the Physics Program at the Graduate Center of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States)

    2016-06-14

    In the thirty-two years since the birth of the foundational theorems, time-dependent density functional theory has had a tremendous impact on calculations of electronic spectra and dynamics in chemistry, biology, solid-state physics, and materials science. Alongside the wide-ranging applications, there has been much progress in understanding fundamental aspects of the functionals and the theory itself. This Perspective looks back to some of these developments, reports on some recent progress and current challenges for functionals, and speculates on future directions to improve the accuracy of approximations used in this relatively young theory.

  13. Charge Transfer Enhancement in the D-π-A Type Porphyrin Dyes: A Density Functional Theory (DFT and Time-Dependent Density Functional Theory (TD-DFT Study

    Directory of Open Access Journals (Sweden)

    Guo-Jun Kang

    2016-11-01

    Full Text Available The electronic geometries and optical properties of two D-π-A type zinc porphyrin dyes (NCH3-YD2 and TPhe-YD were systematically investigated by density functional theory (DFT and time-dependent density functional theory (TD-DFT to reveal the origin of significantly altered charge transfer enhancement by changing the electron donor of the famous porphyrin-based sensitizer YD2-o-C8. The molecular geometries and photophysical properties of dyes before and after binding to the TiO2 cluster were fully investigated. From the analyses of natural bond orbital (NBO, extended charge decomposition analysis (ECDA, and electron density variations (Δρ between the excited state and ground state, it was found that the introduction of N(CH32 and 1,1,2-triphenylethene groups enhanced the intramolecular charge-transfer (ICT character compared to YD2-o-C8. The absorption wavelength and transition possess character were significantly influenced by N(CH32 and 1,1,2-triphenylethene groups. NCH3-YD2 with N(CH32 groups in the donor part is an effective way to improve the interactions between the dyes and TiO2 surface, light having efficiency (LHE, and free energy change (ΔGinject, which is expected to be an efficient dye for use in dye-sensitized solar cells (DSSCs.

  14. Density dependence of reactor performance with thermal confinement scalings

    International Nuclear Information System (INIS)

    Stotler, D.P.

    1992-03-01

    Energy confinement scalings for the thermal component of the plasma published thus far have a different dependence on plasma density and input power than do scalings for the total plasma energy. With such thermal scalings, reactor performance (measured by Q, the ratio of the fusion power to the sum of the ohmic and auxiliary input powers) worsens with increasing density. This dependence is the opposite of that found using scalings based on the total plasma energy, indicating that reactor operation concepts may need to be altered if this density dependence is confirmed in future research

  15. NEW HYPERON EQUATIONS OF STATE FOR SUPERNOVAE AND NEUTRON STARS IN DENSITY-DEPENDENT HADRON FIELD THEORY

    Energy Technology Data Exchange (ETDEWEB)

    Banik, Sarmistha [BITS Pilani, Hyderabad Campus, Hyderabad-500078 (India); Hempel, Matthias [Departement Physik, Universität Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Bandyopadhyay, Debades [Astroparticle Physics and Cosmology Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064 (India)

    2014-10-01

    We develop new hyperon equation of state (EoS) tables for core-collapse supernova simulations and neutron stars. These EoS tables are based on a density-dependent relativistic hadron field theory where baryon-baryon interaction is mediated by mesons, using the parameter set DD2 for nucleons. Furthermore, light and heavy nuclei along with interacting nucleons are treated in the nuclear statistical equilibrium model of Hempel and Schaffner-Bielich which includes excluded volume effects. Of all possible hyperons, we consider only the contribution of Λs. We have developed two variants of hyperonic EoS tables: in the npΛφ case the repulsive hyperon-hyperon interaction mediated by the strange φ meson is taken into account, and in the npΛ case it is not. The EoS tables for the two cases encompass a wide range of densities (10{sup –12} to ∼1 fm{sup –3}), temperatures (0.1 to 158.48 MeV), and proton fractions (0.01 to 0.60). The effects of Λ hyperons on thermodynamic quantities such as free energy per baryon, pressure, or entropy per baryon are investigated and found to be significant at higher densities. The cold, β-equilibrated EoS (with the crust included self-consistently) results in a 2.1 M {sub ☉} maximum mass neutron star for the npΛφ case, whereas that for the npΛ case is 1.95 M {sub ☉}. The npΛφ EoS represents the first supernova EoS table involving hyperons that is directly compatible with the recently measured 2 M {sub ☉} neutron stars.

  16. The dependence of stellar properties on initial cloud density

    Science.gov (United States)

    Jones, Michael O.; Bate, Matthew R.

    2018-05-01

    We investigate the dependence of stellar properties on the initial mean density of the molecular cloud in which stellar clusters form using radiation hydrodynamical simulations that resolve the opacity limit for fragmentation. We have simulated the formation of three star clusters from the gravitational collapse of molecular clouds whose densities vary by a factor of a hundred. As with previous calculations including radiative feedback, we find that the dependence of the characteristic stellar mass, Mc, on the initial mean density of the cloud, ρ, is weaker than the dependence of the thermal Jeans mass. However, unlike previous calculations, which found no statistically significant variation in the median mass with density, we find a weak dependence approximately of the form Mc∝ρ-1/5. The distributions of properties of multiple systems do not vary significantly between the calculations. We compare our results to the result of observational surveys of star-forming regions, and suggest that the similarities between the properties of our lowest density calculation and the nearby Taurus-Auriga region indicate that the apparent excess of solar-type stars observed may be due to the region's low density.

  17. Effect of cell density on adipogenic differentiation of mesenchymal stem cells

    International Nuclear Information System (INIS)

    Lu, Hongxu; Guo, Likun; Wozniak, Michal J.; Kawazoe, Naoki; Tateishi, Tetsuya; Zhang, Xingdong; Chen, Guoping

    2009-01-01

    The effect of cell density on the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells (MSCs) was investigated by using a patterning technique to induce the formation of a cell density gradient on a micropatterned surface. The adipogenic differentiation of MSCs at a density gradient from 5 x 10 3 to 3 x 10 4 cells/cm 2 was examined. Lipid vacuoles were observed at all cell densities after 1-3 weeks of culture in adipogenic differentiation medium although the lipid vacuoles were scarce at the low cell density and abundant at the high cell density. Real-time RT-PCR analysis showed that adipogenesis marker genes encoding peroxisome proliferator-activated receptor γ2 (PPARγ2), lipoprotein lipase (LPL), and fatty acid binding protein-4 (FABP4) were detected in the MSCs cultured at all cell densities. The results suggest that there was no apparent effect of cell density on the adipogenic differentiation of human MSCs.

  18. Remarks on time-dependent [current]-density functional theory for open quantum systems.

    Science.gov (United States)

    Yuen-Zhou, Joel; Aspuru-Guzik, Alán

    2013-08-14

    Time-dependent [current]-density functional theory for open quantum systems (OQS) has emerged as a formalism that can incorporate dissipative effects in the dynamics of many-body quantum systems. Here, we review and clarify some formal aspects of these theories that have been recently questioned in the literature. In particular, we provide theoretical support for the following conclusions: (1) contrary to what we and others had stated before, within the master equation framework, there is in fact a one-to-one mapping between vector potentials and current densities for fixed initial state, particle-particle interaction, and memory kernel; (2) regardless of the first conclusion, all of our recently suggested Kohn-Sham (KS) schemes to reproduce the current and particle densities of the original OQS, and in particular, the use of a KS closed driven system, remains formally valid; (3) the Lindblad master equation maintains the positivity of the density matrix regardless of the time-dependence of the Hamiltonian or the dissipation operators; (4) within the stochastic Schrödinger equation picture, a one-to-one mapping from stochastic vector potential to stochastic current density for individual trajectories has not been proven so far, except in the case where the vector potential is the same for every member of the ensemble, in which case, it reduces to the Lindblad master equation picture; (5) master equations may violate certain desired properties of the density matrix, such as positivity, but they remain as one of the most useful constructs to study OQS when the environment is not easily incorporated explicitly in the calculation. The conclusions support our previous work as formally rigorous, offer new insights into it, and provide a common ground to discuss related theories.

  19. Optical properties of Al nanostructures from time dependent density functional theory

    KAUST Repository

    Mokkath, Junais Habeeb

    2016-04-05

    The optical properties of Al nanostructures are investigated by means of time dependent density functional theory, considering chains of varying length and ladders/stripes of varying aspect ratio. The absorption spectra show redshifting for increasing length and aspect ratio. For the chains the absorption is dominated by HOMO → LUMO transitions, whereas ladders and stripes reveal more complex spectra of plasmonic nature above a specific aspect ratio.

  20. Multicomponent density-functional theory for time-dependent systems

    NARCIS (Netherlands)

    Butriy, O.; Ebadi, H.; de Boeij, P. L.; van Leeuwen, R.; Gross, E. K. U.

    2007-01-01

    We derive the basic formalism of density functional theory for time-dependent electron-nuclear systems. The basic variables of this theory are the electron density in body-fixed frame coordinates and the diagonal of the nuclear N-body density matrix. The body-fixed frame transformation is carried

  1. In vitro cell quality of articular chondrocytes assigned for autologous implantation in dependence of specific patient characteristics

    DEFF Research Database (Denmark)

    Pestka, Jan M; Schmal, Hagen; Salzmann, Gian

    2011-01-01

    OBJECTIVE: Autologous chondrocyte implantation (ACI) is a well-established therapeutic option for the treatment of cartilage defects of the knee joint. Since information concerning the cellular aspects of ACI is still limited, the aim of the present study was to investigate relevant differences...... between chondrocyte quality after in vitro cultivation and possible correlations with patient-specific factors. DESIGN: Cell quality of 252 consecutive ACI patients was assessed after chondrocyte in vitro expansion by determination of the expression of cartilage relevant surface marker CD44 and cartilage......, aggrecan or collagen type II nor cell density or viability after proliferation seemed to correlate with the grade of joint degeneration, defect aetiology or patient gender. However, chondrocytes harvested from the knee joints of patients at less than 20 years of age showed significantly higher expression...

  2. Density and Specific Gravity Metrics in Biomass Research

    Science.gov (United States)

    Micheal C. Wiemann; G. Bruce Williamson

    2012-01-01

    Following the 2010 publication of Measuring Wood Specific Gravity… Correctly in the American Journal of Botany, readers contacted us to inquire about application of wood density and specific gravity to biomass research. Here we recommend methods for sample collection, volume measurement, and determination of wood density and specific gravity for...

  3. Cell thickness of UV absorption by the cell: relation to UV action spectrum shift in mammalian cells in culture

    International Nuclear Information System (INIS)

    Sakharov, V.H.; Voronkova, L.N.; Blokhin, A.V.

    1985-01-01

    By means of reconstruction of series half - thin transverse sections the three - dimensional morphometry of SPEV cells for a series of their specific states in culture is performed: for exponential growth in a monolayer, in a merged monolayer, in the mitosis phase, for giant cells and suspension cells. In the monolayer the cell thickness in its central part depended mainly on the nucleus thickness and in average changed but slightly despite a wide range of changes in volumes of nuclei and cells and their density in culture. The cell thickness has noticeably increased in mitosis. For the above states of cells UV radiation absorption spectra are determined. It is shown that a certain shift of action spectrus of death of mammalian cells as compared with that for bacterial cell can be a seguence of selfshielding and not differences in the nature of active chromophores

  4. Extensive gene-specific translational reprogramming in a model of B cell differentiation and Abl-dependent transformation.

    Directory of Open Access Journals (Sweden)

    Jamie G Bates

    Full Text Available To what extent might the regulation of translation contribute to differentiation programs, or to the molecular pathogenesis of cancer? Pre-B cells transformed with the viral oncogene v-Abl are suspended in an immortalized, cycling state that mimics leukemias with a BCR-ABL1 translocation, such as Chronic Myelogenous Leukemia (CML and Acute Lymphoblastic Leukemia (ALL. Inhibition of the oncogenic Abl kinase with imatinib reverses transformation, allowing progression to the next stage of B cell development. We employed a genome-wide polysome profiling assay called Gradient Encoding to investigate the extent and potential contribution of translational regulation to transformation and differentiation in v-Abl-transformed pre-B cells. Over half of the significantly translationally regulated genes did not change significantly at the level of mRNA abundance, revealing biology that might have been missed by measuring changes in transcript abundance alone. We found extensive, gene-specific changes in translation affecting genes with known roles in B cell signaling and differentiation, cancerous transformation, and cytoskeletal reorganization potentially affecting adhesion. These results highlight a major role for gene-specific translational regulation in remodeling the gene expression program in differentiation and malignant transformation.

  5. Role of the Coulomb interaction in the low-frequency density of states of DNA double helices

    International Nuclear Information System (INIS)

    Garcia, A.E.; Krumhansl, J.A.

    1988-01-01

    The complete vibrational frequency spectrum of several DNA double-helical oligomers is calculated using established pair potentials. Various cutoff values are used for the range of the Coulomb interactions. At very low frequency the integrated density of states shows a noninteger exponent with values ranging from 0.75 to 1.55, depending on the cutoff value for the Coulomb interactions. We conclude that the cumulative densities of states in those molecules depend more on competing interactions than on various proposed universal laws

  6. Composition dependence of density of states in a-Se100−xSnx thin ...

    Indian Academy of Sciences (India)

    genide glassy semiconductors [5–15] and the results have been interpreted in terms of space charge limited conduction or Poole–Frenkel conduction. One of the most direct methods for the determination of the density of the localised states g0 in the mobility gap involves the measurements of SCLC, which can be easily ...

  7. Mechanisms maintaining enhancement of allografts. I. Demonstration of a specific suppressor cell

    International Nuclear Information System (INIS)

    Hall, B.M.

    1985-01-01

    DA rats treated with hyperimmune anti-PVG serum and grafted with (DA X PVG)F1 heart grafts in which graft survival was prolonged for greater than 75 d were used to examine the cellular mechanisms that maintain the state of specific unresponsiveness found in these animals. The capacity of lymphocytes from these animals to effect or inhibit graft rejection on adoptive transfer to irradiated heart-grafted hosts was tested. Spleen cell populations and the T cell subpopulation separated from spleen cells in vitro failed to restore rejection of PVG heart grafts in irradiated DA recipients but restored third party Lew graft rejection. Whole spleen cells had the capacity to suppress the ability of normal DA LNC to cause graft rejection, but T cells from spleen only delayed the restoration of rejection. LNC and recirculating T cells from rats with enhanced grafts adoptively restored PVG rejection, however. These studies show that the state of specific unresponsiveness that follows the induction of passive enhancement is dependent in part upon active suppression, which is induced or mediated by T lymphocytes. The recirculating pool of lymphocytes in these animals is not depleted of specific alloreactive cells with the capacity to initiate and effect rejection. Thus, these animals responsiveness is not like that found in transplantation tolerance induced in neonatal rats, but is, in part, due to a suppressor response that can inhibit normal alloreactive cells capacity to initiate and effect rejection

  8. Experimental evidence for density-dependent reproduction in a cooperatively breeding passerine

    NARCIS (Netherlands)

    Brouwer, Lyanne; Tinbergen, Joost M.; Both, Christiaan; Bristol, Rachel; Richardson, David S.; Komdeur, Jan; Sauer, J.R.

    Temporal variation in survival, fecundity, and dispersal rates is associated with density-dependent and density-independent processes. Stable natural populations are expected to be regulated by density-dependent factors. However, detecting this by investigating natural variation in density is

  9. Density functional and theoretical study of the temperature and pressure dependency of the plasmon energy of solids

    International Nuclear Information System (INIS)

    Attarian Shandiz, M.; Gauvin, R.

    2014-01-01

    The temperature and pressure dependency of the volume plasmon energy of solids was investigated by density functional theory calculations. The volume change of crystal is the major factor responsible for the variation of valence electron density and plasmon energy in the free electron model. Hence, to introduce the effect of temperature and pressure for the density functional theory calculations of plasmon energy, the temperature and pressure dependency of lattice parameter was used. Also, by combination of the free electron model and the equation of state based on the pseudo-spinodal approach, the temperature and pressure dependency of the plasmon energy was modeled. The suggested model is in good agreement with the results of density functional theory calculations and available experimental data for elements with the free electron behavior.

  10. Demonstration-Scale High-Cell-Density Fermentation of Pichia pastoris.

    Science.gov (United States)

    Liu, Wan-Cang; Zhu, Ping

    2018-01-01

    Pichia pastoris has been one of the most successful heterologous overexpression systems in generating proteins for large-scale production through high-cell-density fermentation. However, optimizing conditions of the large-scale high-cell-density fermentation for biochemistry and industrialization is usually a laborious and time-consuming process. Furthermore, it is often difficult to produce authentic proteins in large quantities, which is a major obstacle for functional and structural features analysis and industrial application. For these reasons, we have developed a protocol for efficient demonstration-scale high-cell-density fermentation of P. pastoris, which employs a new methanol-feeding strategy-biomass-stat strategy and a strategy of increased air pressure instead of pure oxygen supplement. The protocol included three typical stages of glycerol batch fermentation (initial culture phase), glycerol fed-batch fermentation (biomass accumulation phase), and methanol fed-batch fermentation (induction phase), which allows direct online-monitoring of fermentation conditions, including broth pH, temperature, DO, anti-foam generation, and feeding of glycerol and methanol. Using this protocol, production of the recombinant β-xylosidase of Lentinula edodes origin in 1000-L scale fermentation can be up to ~900 mg/L or 9.4 mg/g cells (dry cell weight, intracellular expression), with the specific production rate and average specific production of 0.1 mg/g/h and 0.081 mg/g/h, respectively. The methodology described in this protocol can be easily transferred to other systems, and eligible to scale up for a large number of proteins used in either the scientific studies or commercial purposes.

  11. Cell wall microstructure, pore size distribution and absolute density of hemp shiv

    Science.gov (United States)

    Jiang, Y.; Lawrence, M.; Ansell, M. P.; Hussain, A.

    2018-04-01

    This paper, for the first time, fully characterizes the intrinsic physical parameters of hemp shiv including cell wall microstructure, pore size distribution and absolute density. Scanning electron microscopy revealed microstructural features similar to hardwoods. Confocal microscopy revealed three major layers in the cell wall: middle lamella, primary cell wall and secondary cell wall. Computed tomography improved the visualization of pore shape and pore connectivity in three dimensions. Mercury intrusion porosimetry (MIP) showed that the average accessible porosity was 76.67 ± 2.03% and pore size classes could be distinguished into micropores (3-10 nm) and macropores (0.1-1 µm and 20-80 µm). The absolute density was evaluated by helium pycnometry, MIP and Archimedes' methods. The results show that these methods can lead to misinterpretation of absolute density. The MIP method showed a realistic absolute density (1.45 g cm-3) consistent with the density of the known constituents, including lignin, cellulose and hemi-cellulose. However, helium pycnometry and Archimedes' methods gave falsely low values owing to 10% of the volume being inaccessible pores, which require sample pretreatment in order to be filled by liquid or gas. This indicates that the determination of the cell wall density is strongly dependent on sample geometry and preparation.

  12. Fundamentals of time-dependent density functional theory

    International Nuclear Information System (INIS)

    Marques, Miguel A.L.; Rubio, Angel

    2012-01-01

    There have been many significant advances in time-dependent density functional theory over recent years, both in enlightening the fundamental theoretical basis of the theory, as well as in computational algorithms and applications. This book, as successor to the highly successful volume Time-Dependent Density Functional Theory (Lect. Notes Phys. 706, 2006) brings together for the first time all recent developments in a systematic and coherent way. First, a thorough pedagogical presentation of the fundamental theory is given, clarifying aspects of the original proofs and theorems, as well as presenting fresh developments that extend the theory into new realms such as alternative proofs of the original Runge-Gross theorem, open quantum systems, and dispersion forces to name but a few. Next, all of the basic concepts are introduced sequentially and building in complexity, eventually reaching the level of open problems of interest. Contemporary applications of the theory are discussed, from real-time coupled-electron-ion dynamics, to excited-state dynamics and molecular transport. Last but not least, the authors introduce and review recent advances in computational implementation, including massively parallel architectures and graphical processing units. Special care has been taken in editing this volume as a multi-author textbook, following a coherent line of thought, and making all the relevant connections between chapters and concepts consistent throughout. As such it will prove to be the text of reference in this field, both for beginners as well as expert researchers and lecturers teaching advanced quantum mechanical methods to model complex physical systems, from molecules to nanostructures, from biocomplexes to surfaces, solids and liquids. (orig.)

  13. Self-consistent RPA and the time-dependent density matrix approach

    Energy Technology Data Exchange (ETDEWEB)

    Schuck, P. [Institut de Physique Nucleaire, Orsay (France); CNRS et Universite Joseph Fourier, Laboratoire de Physique et Modelisation des Milieux Condenses, Grenoble (France); Tohyama, M. [Kyorin University School of Medicine, Mitaka, Tokyo (Japan)

    2016-10-15

    The time-dependent density matrix (TDDM) or BBGKY (Bogoliubov, Born, Green, Kirkwood, Yvon) approach is decoupled and closed at the three-body level in finding a natural representation of the latter in terms of a quadratic form of two-body correlation functions. In the small amplitude limit an extended RPA coupled to an also extended second RPA is obtained. Since including two-body correlations means that the ground state cannot be a Hartree-Fock state, naturally the corresponding RPA is upgraded to Self-Consistent RPA (SCRPA) which was introduced independently earlier and which is built on a correlated ground state. SCRPA conserves all the properties of standard RPA. Applications to the exactly solvable Lipkin and the 1D Hubbard models show good performances of SCRPA and TDDM. (orig.)

  14. Computational complexity of time-dependent density functional theory

    International Nuclear Information System (INIS)

    Whitfield, J D; Yung, M-H; Tempel, D G; Aspuru-Guzik, A; Boixo, S

    2014-01-01

    Time-dependent density functional theory (TDDFT) is rapidly emerging as a premier method for solving dynamical many-body problems in physics and chemistry. The mathematical foundations of TDDFT are established through the formal existence of a fictitious non-interacting system (known as the Kohn–Sham system), which can reproduce the one-electron reduced probability density of the actual system. We build upon these works and show that on the interior of the domain of existence, the Kohn–Sham system can be efficiently obtained given the time-dependent density. We introduce a V-representability parameter which diverges at the boundary of the existence domain and serves to quantify the numerical difficulty of constructing the Kohn-Sham potential. For bounded values of V-representability, we present a polynomial time quantum algorithm to generate the time-dependent Kohn–Sham potential with controllable error bounds. (paper)

  15. Density-dependent electron scattering in photoexcited GaAs

    DEFF Research Database (Denmark)

    Mics, Zoltán; D'’Angio, Andrea; Jensen, Søren A.

    2013-01-01

    —In a series of systematic optical pump - terahertz probe experiments we study the density-dependent electron scattering rate in photoexcited GaAs in a large range of carrier densities. The electron scattering time decreases by as much as a factor of 4, from 320 to 60 fs, as the electron density...

  16. Prevalence and strength of density-dependent tree recruitment

    Science.gov (United States)

    Kai Zhu; Christopher W. Woodall; Joao V.D. Monteiro; James S. Clark

    2015-01-01

    Density dependence could maintain diversity in forests, but studies continue to disagree on its role. Part of the disagreement results from the fact that different studies have evaluated different responses (survival, recruitment, or growth) of different stages (seeds, seedlings, or adults) to different inputs (density of seedlings, density or distance to adults). Most...

  17. State of charge monitoring of vanadium redox flow batteries using half cell potentials and electrolyte density

    Science.gov (United States)

    Ressel, Simon; Bill, Florian; Holtz, Lucas; Janshen, Niklas; Chica, Antonio; Flower, Thomas; Weidlich, Claudia; Struckmann, Thorsten

    2018-02-01

    The operation of vanadium redox flow batteries requires reliable in situ state of charge (SOC) monitoring. In this study, two SOC estimation approaches for the negative half cell are investigated. First, in situ open circuit potential measurements are combined with Coulomb counting in a one-step calibration of SOC and Nernst potential which doesn't need additional reference SOCs. In-sample and out-of-sample SOCs are estimated and analyzed, estimation errors ≤ 0.04 are obtained. In the second approach, temperature corrected in situ electrolyte density measurements are used for the first time in vanadium redox flow batteries for SOC estimation. In-sample and out-of-sample SOC estimation errors ≤ 0.04 demonstrate the feasibility of this approach. Both methods allow recalibration during battery operation. The actual capacity obtained from SOC calibration can be used in a state of health model.

  18. Extracellular matrix-dependent myosin dynamics during G1-S phase cell cycle progression in hepatocytes

    International Nuclear Information System (INIS)

    Bhadriraju, Kiran; Hansen, Linda K.

    2004-01-01

    Cell spreading and proliferation are tightly coupled in anchorage-dependent cells. While adhesion-dependent proliferation signals require an intact actin cytoskeleton, and some of these signals such as ERK activation have been characterized, the role of myosin in spreading and cell cycle progression under different extracellular matrix (ECM) conditions is not known. Studies presented here examine changes in myosin activity in freshly isolated hepatocytes under ECM conditions that promote either proliferation (high fibronectin density) or growth arrest (low fibronectin density). Three different measures were obtained and related to both spreading and cell cycle progression: myosin protein levels and association with cytoskeleton, myosin light chain phosphorylation, and its ATPase activity. During the first 48 h in culture, corresponding with transit through G1 phase, there was a six-fold increase in both myosin protein levels and myosin association with actin cytoskeleton. There was also a steady increase in myosin light chain phosphorylation and ATPase activity with spreading, which did not occur in non-spread, growth-arrested cells on low density of fibronectin. Myosin-inhibiting drugs blocked ERK activation, cyclin D1 expression, and S phase entry. Overexpression of the cell cycle protein cyclin D1 overcame both ECM-dependent and actomyosin-dependent inhibition of DNA synthesis, suggesting that cyclin D1 is a key event downstream of myosin-dependent cell cycle regulation

  19. State-Dependent Implication and Equivalence in Quantum Logic

    Directory of Open Access Journals (Sweden)

    Fedor Herbut

    2012-01-01

    Full Text Available Ideal occurrence of an event (projector leads to the known change of a state (density operator into (the Lüders state. It is shown that two events and give the same Lüders state if and only if the equivalence relation is valid. This relation determines equivalence classes. The set of them and each class, are studied in detail. It is proved that the range projector of the Lüders state can be evaluated as , where denotes the greatest lower bound, and is the null projector of . State-dependent implication extends absolute implication (which, in turn, determines the entire structure of quantum logic. and are investigated in a closely related way to mutual benefit. Inherent in the preorder is the state-dependent equivalence , defining equivalence classes in a given Boolean subalgebra. The quotient set, in which the classes are the elements, has itself a partially ordered structure, and so has each class. In a complete Boolean subalgebra, both structures are complete lattices. Physical meanings are discussed.

  20. Intercohort density dependence drives brown trout habitat selection

    Science.gov (United States)

    Ayllón, Daniel; Nicola, Graciela G.; Parra, Irene; Elvira, Benigno; Almodóvar, Ana

    2013-01-01

    Habitat selection can be viewed as an emergent property of the quality and availability of habitat but also of the number of individuals and the way they compete for its use. Consequently, habitat selection can change across years due to fluctuating resources or to changes in population numbers. However, habitat selection predictive models often do not account for ecological dynamics, especially density dependent processes. In stage-structured population, the strength of density dependent interactions between individuals of different age classes can exert a profound influence on population trajectories and evolutionary processes. In this study, we aimed to assess the effects of fluctuating densities of both older and younger competing life stages on the habitat selection patterns (described as univariate and multivariate resource selection functions) of young-of-the-year, juvenile and adult brown trout Salmo trutta. We observed all age classes were selective in habitat choice but changed their selection patterns across years consistently with variations in the densities of older but not of younger age classes. Trout of an age increased selectivity for positions highly selected by older individuals when their density decreased, but this pattern did not hold when the density of younger age classes varied. It suggests that younger individuals are dominated by older ones but can expand their range of selected habitats when density of competitors decreases, while older trout do not seem to consider the density of younger individuals when distributing themselves even though they can negatively affect their final performance. Since these results may entail critical implications for conservation and management practices based on habitat selection models, further research should involve a wider range of river typologies and/or longer time frames to fully understand the patterns of and the mechanisms underlying the operation of density dependence on brown trout habitat

  1. Anthropogenically-Mediated Density Dependence in a Declining Farmland Bird.

    Directory of Open Access Journals (Sweden)

    Jenny C Dunn

    Full Text Available Land management intrinsically influences the distribution of animals and can consequently alter the potential for density-dependent processes to act within populations. For declining species, high densities of breeding territories are typically considered to represent productive populations. However, as density-dependent effects of food limitation or predator pressure may occur (especially when species are dependent upon separate nesting and foraging habitats, high territory density may limit per-capita productivity. Here, we use a declining but widespread European farmland bird, the yellowhammer Emberiza citrinella L., as a model system to test whether higher territory densities result in lower fledging success, parental provisioning rates or nestling growth rates compared to lower densities. Organic landscapes held higher territory densities, but nests on organic farms fledged fewer nestlings, translating to a 5 times higher rate of population shrinkage on organic farms compared to conventional. In addition, when parental provisioning behaviour was not restricted by predation risk (i.e., at times of low corvid activity, nestling provisioning rates were higher at lower territory densities, resulting in a much greater increase in nestling mass in low density areas, suggesting that food limitation occurred at high densities. These findings in turn suggest an ecological trap, whereby preferred nesting habitat does not provide sufficient food for rearing nestlings at high population density, creating a population sink. Habitat management for farmland birds should focus not simply on creating a high nesting density, but also on ensuring heterogeneous habitats to provide food resources in close proximity to nesting birds, even if this occurs through potentially restricting overall nest density but increasing population-level breeding success.

  2. Temperature Dependence Viscosity and Density of Different Biodiesel Blends

    Directory of Open Access Journals (Sweden)

    Vojtěch Kumbár

    2015-01-01

    Full Text Available The main goal of this paper is to assess the effect of rapeseed oil methyl ester (RME concentration in diesel fuel on its viscosity and density behaviour. The density and dynamic viscosity were observed at various mixing ratios of RME and diesel fuel. All measurements were performed at constant temperature of 40 °C. Increasing ratio of RME in diesel fuel was reflected in increased density value and dynamic viscosity of the blend. In case of pure RME, pure diesel fuel, and a blend of both (B30, temperature dependence of dynamic viscosity and density was examined. Temperature range in the experiment was −10 °C to 80 °C. Considerable temperature dependence of dynamic viscosity and density was found and demonstrated for all three samples. This finding is in accordance with theoretical assumptions and reference data. Mathematical models were developed and tested. Temperature dependence of dynamic viscosity was modeled using a polynomial 3rd polynomial degree. Correlation coefficients R −0.796, −0.948, and −0.974 between measured and calculated values were found. Temperature dependence of density was modeled using a 2nd polynomial degree. Correlation coefficients R −0.994, −0.979, and −0.976 between measured and calculated values were acquired. The proposed models can be used for flow behaviour prediction of RME, diesel fuel, and their blends.

  3. Relativistic mean field theory with density dependent coupling constants for nuclear matter and finite nuclei with large charge asymmetry

    Energy Technology Data Exchange (ETDEWEB)

    Typel, S; Wolter, H H [Sektion Physik, Univ. Muenchen, Garching (Germany)

    1998-06-01

    Nuclear matter and ground state properties for (proton and neutron) semi-closed shell nuclei are described in relativistic mean field theory with coupling constants which depend on the vector density. The parametrization of the density dependence for {sigma}-, {omega}- and {rho}-mesons is obtained by fitting to properties of nuclear matter and some finite nuclei. The equation of state for symmetric and asymmetric nuclear matter is discussed. Finite nuclei are described in Hartree approximation, including a charge and an improved center-of-mass correction. Pairing is considered in the BCS approximation. Special attention is directed to the predictions for properties at the neutron and proton driplines, e.g. for separation energies, spin-orbit splittings and density distributions. (orig.)

  4. Electromagnetic local density of states in graphene-covered porous silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ting [Department of Physics, Nanchang University, Nanchang 330031 (China); Wang, Tong-Biao, E-mail: tbwang@ncu.edu.cn [Department of Physics, Nanchang University, Nanchang 330031 (China); Liao, Qing-Hua; Liu, Jiang-Tao; Yu, Tian-Bao [Department of Physics, Nanchang University, Nanchang 330031 (China); Liu, Nian-Hua [Institute for Advanced Study, Nanchang University, Nanchang 330031 (China)

    2017-06-21

    Surface phonon polariton supported by silicon carbide (SiC) can be strongly coupled with graphene plasmon in the graphene-covered SiC bulk. The spectrum of the electromagnetic local density of states exhibits two peaks whose positions can be tuned by the chemical potential of graphene. In this work, we study the electromagnetic local density of states in the proximity of a graphene-covered SiC with periodic hole arrays. The well-known peak from the coupling of surface polariton supported by SiC and graphene plasmon splits into two. With increased volume ratio of holes, one of the split peak shifts towards high frequencies, whereas the other moves towards low frequencies. The dependence of split-peak positions on the chemical potential and permittivity of filling materials in the holes are also investigated. This study offers another method of modulating the electromagnetic local density of states. - Highlights: • The electromagnetic local density of states in the proximity of graphene-covered anisotropic SiC is firstly studied. • The peak from resonance of surface phonon polaritons in the EM-LDOS spectrum can be split into two. • The split peaks can be tuned by chemical potential, filling factor, and filling materials. • Our results provide a new method to modulate the EM-LDOS.

  5. Thermal state of the general time-dependent harmonic oscillator

    Indian Academy of Sciences (India)

    Taking advantage of dynamical invariant operator, we derived quantum mechanical solution of general time-dependent harmonic oscillator. The uncertainty relation of the system is always larger than ħ=2 not only in number but also in the thermal state as expected. We used the diagonal elements of density operator ...

  6. Temperature and carrier-density dependence of Auger and radiative recombination in nitride optoelectronic devices

    International Nuclear Information System (INIS)

    Kioupakis, Emmanouil; Yan, Qimin; Steiauf, Daniel; Van de Walle, Chris G

    2013-01-01

    Nitride light-emitting diodes are a promising solution for efficient solid-state lighting, but their performance at high power is affected by the efficiency-droop problem. Previous experimental and theoretical work has identified Auger recombination, a three-particle nonradiative carrier recombination mechanism, as the likely cause of the droop. In this work, we use first-principles calculations to elucidate the dependence of the radiative and Auger recombination rates on temperature, carrier density and quantum-well confinement. Our calculated data for the temperature dependence of the recombination coefficients are in good agreement with experiment and provide further validation on the role of Auger recombination in the efficiency reduction. Polarization fields and phase-space filling negatively impact device efficiency because they increase the operating carrier density at a given current density and increase the fraction of carriers lost to Auger recombination. (paper)

  7. Online traffic flow model applying dynamic flow-density relation

    International Nuclear Information System (INIS)

    Kim, Y.

    2002-01-01

    This dissertation describes a new approach of the online traffic flow modelling based on the hydrodynamic traffic flow model and an online process to adapt the flow-density relation dynamically. The new modelling approach was tested based on the real traffic situations in various homogeneous motorway sections and a motorway section with ramps and gave encouraging simulation results. This work is composed of two parts: first the analysis of traffic flow characteristics and second the development of a new online traffic flow model applying these characteristics. For homogeneous motorway sections traffic flow is classified into six different traffic states with different characteristics. Delimitation criteria were developed to separate these states. The hysteresis phenomena were analysed during the transitions between these traffic states. The traffic states and the transitions are represented on a states diagram with the flow axis and the density axis. For motorway sections with ramps the complicated traffic flow is simplified and classified into three traffic states depending on the propagation of congestion. The traffic states are represented on a phase diagram with the upstream demand axis and the interaction strength axis which was defined in this research. The states diagram and the phase diagram provide a basis for the development of the dynamic flow-density relation. The first-order hydrodynamic traffic flow model was programmed according to the cell-transmission scheme extended by the modification of flow dependent sending/receiving functions, the classification of cells and the determination strategy for the flow-density relation in the cells. The unreasonable results of macroscopic traffic flow models, which may occur in the first and last cells in certain conditions are alleviated by applying buffer cells between the traffic data and the model. The sending/receiving functions of the cells are determined dynamically based on the classification of the

  8. Nonadiabatic dynamics with intersystem crossings: A time-dependent density functional theory implementation

    Energy Technology Data Exchange (ETDEWEB)

    Franco de Carvalho, F. [Centre Européen de Calcul Atomique et Moléculaire, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland); Tavernelli, I. [IBM Research GmbH, Zurich Research Laboratory, 8803 Ruschlikon (Switzerland)

    2015-12-14

    In this work, we derive a method to perform trajectory-based nonadiabatic dynamics that is able to describe both nonadiabatic transitions and intersystem crossing events (transitions between states of different spin-multiplicity) at the same level of theory, namely, time-dependent density functional theory (TDDFT). To this end, we combined our previously developed TDDFT-based trajectory surface hopping scheme with an accurate and efficient algorithm for the calculation of the spin-orbit coupling (SOC) matrix elements. More specifically, we designed two algorithms for the calculation of intersystem crossing transitions, one based on an extended Tully’s surface hopping scheme including SOC and the second based on a Landau-Zener approximation applied to the spin sector of the electronic Hilbert space. This development allows for the design of an efficient on-the-fly nonadiabatic approach that can handle, on an equal footing, nonadiabatic and intersystem crossing transitions. The method is applied to the study of the photophysics of sulfur dioxide (SO{sub 2}) in gas and liquid phases.

  9. Thermodynamics of strange quark matter with the density-dependent bag constant

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The thermodynamics of strange quark matter with density dependent bag constant are studied self-consistently in the framework of the general ensemble theory and the MIT bag model.In our treatment,an additional term is found in the expression of pressure.With the additional term,the zero pressure locates exactly at the lowest energy state,indicating that our treatment is a self-consistently thermodynamic treatment.The self-consistent equations of state of strange quark matter in both the normal and color-flavor-locked phase are derived.They are both softer than the inconsistent ones.Strange stars in both the normal and color-flavor locked phase have smaller masses and radii in our treatment.It is also interesting to find that the energy density at a star surface in our treatment is much higher than that in the inconsistent treatment for both phases.Consequently,the surface properties and the corresponding observational properties of strange stars in our treatment are different from those in the inconsistent treatment.

  10. Thermodynamics of strange quark matter with the density-dependent bag constant

    Institute of Scientific and Technical Information of China (English)

    ZHU MingFeng; LIU GuangZhou; YU Zi; XU Yan; SONG WenTao

    2009-01-01

    The thermodynamics of strange quark matter with density dependent bag constant are studied selfconsistently in the framework of the general ensemble theory and the MIT bag model.In our treatment,an additional term Is found in the expression of pressure.With the additional term,the zero pressure locates exactly at the lowest energy state,Indicating that our treatment is a self-consistently thermodynamic treatment.The self-consistent equations of state of strange quark matter in both the normal and color-flavor-locked phase are derived.They are both softer than the inconsistent ones.Strange stars in both the normal and color-flavor locked phase have smaller masses and radii in our treatment.It is also interesting to find that the energy density at a star surface in our treatment is much higher than that In the inconsistent treatment for both phases.Consequently,the surface properties and the corresponding observational properties of strange stars in our treatment are different from those in the inconsistent treatment.

  11. Analyzing the dependence of oxygen incorporation current density on overpotential and oxygen partial pressure in mixed conducting oxide electrodes.

    Science.gov (United States)

    Guan, Zixuan; Chen, Di; Chueh, William C

    2017-08-30

    The oxygen incorporation reaction, which involves the transformation of an oxygen gas molecule to two lattice oxygen ions in a mixed ionic and electronic conducting solid, is a ubiquitous and fundamental reaction in solid-state electrochemistry. To understand the reaction pathway and to identify the rate-determining step, near-equilibrium measurements have been employed to quantify the exchange coefficients as a function of oxygen partial pressure and temperature. However, because the exchange coefficient contains contributions from both forward and reverse reaction rate constants and depends on both oxygen partial pressure and oxygen fugacity in the solid, unique and definitive mechanistic assessment has been challenging. In this work, we derive a current density equation as a function of both oxygen partial pressure and overpotential, and consider both near and far from equilibrium limits. Rather than considering specific reaction pathways, we generalize the multi-step oxygen incorporation reaction into the rate-determining step, preceding and following quasi-equilibrium steps, and consider the number of oxygen ions and electrons involved in each. By evaluating the dependence of current density on oxygen partial pressure and overpotential separately, one obtains the reaction orders for oxygen gas molecules and for solid-state species in the electrode. We simulated the oxygen incorporation current density-overpotential curves for praseodymium-doped ceria for various candidate rate-determining steps. This work highlights a promising method for studying the exchange kinetics far away from equilibrium.

  12. Pathological significance and prognostic roles of densities of CD57+ cells, CD68+ cells, and mast cells, and their ratios in clear cell renal cell carcinoma.

    Science.gov (United States)

    Nakanishi, Hiromi; Miyata, Yasuyoshi; Mochizuki, Yasushi; Yasuda, Takuji; Nakamura, Yuichiro; Araki, Kyohei; Sagara, Yuji; Matsuo, Tomohiro; Ohba, Kojiro; Sakai, Hideki

    2018-05-19

    The immune system is closely associated with malignant behavior in renal cell carcinoma (RCC). Therefore, understanding the pathological roles of immune cells in tumor stroma is essential to discuss the pathological characteristics of RCC. In this study, the clinical significance of densities of CD57+ cells, CD68+ cells, and mast cells, and their ratios were investigated in patients with clear cell RCC. The densities of CD57+, CD68+, and mast cells were evaluated by immunohistochemical techniques in 179 patients. Proliferation index (PI), apoptotic index (AI), and microvessel density (MVD) were evaluated by using anti-Ki-67, anti-cleaved caspase-3, and anti-CD31 antibodies, respectively. The density of CD57+ cell was negatively correlated with grade, pT stage, and metastasis, although densities of CD68+ cell and mast cell were positively correlated. Ratios of CD68+ cell/CD57+ cell and mast cell/CD57+ cell were significantly correlated with grade, pT stage, and metastasis. Survival analyses showed that the CD68+ cell/CD57+ cell ratio was a significant predictor for cause-specific survival by multi-variate analyses (hazard ratio=1.41, 95% confidential interval=1.03-1.93, P=.031), and was significantly correlated with PI, AI, and MVD (r=.47; P <. 001, r=-.31, P<.001, and r=.40, P<.001, respectively). In conclusion, CD57+ cell, CD68+ cell, and mast cell played important roles in malignancy in clear cell RCC. The CD68+ cell/CD57+ cell ratio was strongly correlated with pathological features and prognosis in these patients because this ratio reflected the status of cancer cell proliferation, apoptosis, and angiogenesis. Copyright © 2018. Published by Elsevier Inc.

  13. Insulin-like growth factor-II receptors in cultured rat hepatocytes: regulation by cell density

    International Nuclear Information System (INIS)

    Scott, C.D.; Baxter, R.C.

    1987-01-01

    Insulin-like growth factor-II (IGF-II) receptors in primary cultures of adult rat hepatocytes were characterized and their regulation by cell density examined. In hepatocytes cultured at 5 X 10(5) cells per 3.8 cm2 plate [ 125 I]IGF-II bound to specific, high affinity receptors (Ka = 4.4 +/- 0.5 X 10(9) l/mol). Less than 1% cross-reactivity by IGF-I and no cross-reactivity by insulin were observed. IGF-II binding increased when cells were permeabilized with 0.01% digitonin, suggesting the presence of an intracellular receptor pool. Determined by Scatchard analysis and by polyacrylamide gel electrophoresis after affinity labeling, the higher binding was due solely to an increase in binding sites present on 220 kDa type II IGF receptors. In hepatocytes cultured at low densities, the number of cell surface receptors increased markedly, from 10-20,000 receptors per cell at a culture density of 6 X 10(5) cells/well to 70-80,000 receptors per cell at 0.38 X 10(5) cells/well. The increase was not due simply to the exposure of receptors from the intracellular pool, as a density-related increase in receptors was also seen in cells permeabilized with digitonin. There was no evidence that IGF binding proteins, either secreted by hepatocytes or present in fetal calf serum, had any effect on the measurement of receptor concentration or affinity. We conclude that rat hepatocytes in primary culture contain specific IGF-II receptors and that both cell surface and intracellular receptors are regulated by cell density

  14. Self-Consistent Optimization of Excited States within Density-Functional Tight-Binding.

    Science.gov (United States)

    Kowalczyk, Tim; Le, Khoa; Irle, Stephan

    2016-01-12

    We present an implementation of energies and gradients for the ΔDFTB method, an analogue of Δ-self-consistent-field density functional theory (ΔSCF) within density-functional tight-binding, for the lowest singlet excited state of closed-shell molecules. Benchmarks of ΔDFTB excitation energies, optimized geometries, Stokes shifts, and vibrational frequencies reveal that ΔDFTB provides a qualitatively correct description of changes in molecular geometries and vibrational frequencies due to excited-state relaxation. The accuracy of ΔDFTB Stokes shifts is comparable to that of ΔSCF-DFT, and ΔDFTB performs similarly to ΔSCF with the PBE functional for vertical excitation energies of larger chromophores where the need for efficient excited-state methods is most urgent. We provide some justification for the use of an excited-state reference density in the DFTB expansion of the electronic energy and demonstrate that ΔDFTB preserves many of the properties of its parent ΔSCF approach. This implementation fills an important gap in the extended framework of DFTB, where access to excited states has been limited to the time-dependent linear-response approach, and affords access to rapid exploration of a valuable class of excited-state potential energy surfaces.

  15. Spin-adapted open-shell time-dependent density functional theory. II. Theory and pilot application.

    Science.gov (United States)

    Li, Zhendong; Liu, Wenjian; Zhang, Yong; Suo, Bingbing

    2011-04-07

    The excited states of open-shell systems calculated by unrestricted Kohn-Sham-based time-dependent density functional theory (U-TD-DFT) are often heavily spin-contaminated and hence meaningless. This is solved ultimately by the recently proposed spin-adapted time-dependent density functional theory (TD-DFT) (S-TD-DFT) [J. Chem. Phys. 133, 064106 (2010)]. Unlike the standard restricted open-shell Kohn-Sham-based TD-DFT (R-TD-DFT) which can only access the singlet-coupled single excitations, the S-TD-DFT can capture both the singlet- and triplet-coupled single excitations with the same computational effort as the U-TD-DFT. The performances of the three approaches (U-TD-DFT, R-TD-DFT, and S-TD-DFT) are compared for both the spin-conserving and spin-flip excitations of prototypical open-shell systems, the nitrogen (N(2)(+)) and naphthalene (C(10)H(8)(+)) cations. The results show that the S-TD-DFT gives rise to balanced descriptions of excited states of open-shell systems.

  16. Equation of state at finite net-baryon density using Taylor coefficients up to sixth order

    International Nuclear Information System (INIS)

    Huovinen, Pasi; Petreczky, Péter; Schmidt, Christian

    2014-01-01

    We employ the lattice QCD data on Taylor expansion coefficients up to sixth order to construct an equation of state at finite net-baryon density. When we take into account how hadron masses depend on lattice spacing and quark mass, the coefficients evaluated using the p4 action are equal to those of hadron resonance gas at low temperature. Thus the parametrised equation of state can be smoothly connected to the hadron resonance gas equation of state. We see that the equation of state using Taylor coefficients up to second order is realistic only at low densities, and that at densities corresponding to s/n B ≳40, the expansion converges by the sixth order term

  17. Probability density of tunneled carrier states near heterojunctions calculated numerically by the scattering method.

    Energy Technology Data Exchange (ETDEWEB)

    Wampler, William R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Myers, Samuel M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Modine, Normand A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    The energy-dependent probability density of tunneled carrier states for arbitrarily specified longitudinal potential-energy profiles in planar bipolar devices is numerically computed using the scattering method. Results agree accurately with a previous treatment based on solution of the localized eigenvalue problem, where computation times are much greater. These developments enable quantitative treatment of tunneling-assisted recombination in irradiated heterojunction bipolar transistors, where band offsets may enhance the tunneling effect by orders of magnitude. The calculations also reveal the density of non-tunneled carrier states in spatially varying potentials, and thereby test the common approximation of uniform- bulk values for such densities.

  18. Dependence of Relative Expression of NTR1 and EGFR on Cell Density and Extracellular pH in Human Pancreatic Cancer Cell Lines

    International Nuclear Information System (INIS)

    Olszewski-Hamilton, Ulrike; Hamilton, Gerhard

    2011-01-01

    Pancreatic adenocarcinoma is a devastating disease characterized by early dissemination and poor prognosis. These solid tumors express receptors for neuropeptides like neurotensin (NT) or epidermal growth factor (EGF) and exhibit acidic regions when grown beyond a certain size. We previously demonstrated increases in intracellular Ca 2+ levels, intracellular pH and interleukin-8 (IL-8) secretion in BxPC-3 and PANC-1 pancreatic cancer cells in response to a stable NT analog. The present study aimed at investigation of the dependence of the relative expression of NT receptor 1 (NTR1) and EGFR in BxPC-3 and MIA PaCa-2 cells on cell density and extracellular pH (pH e ). MTT assays revealed the NTR1 inhibitor SR 142948-sensitive Lys 8 -ψ-Lys 9 NT (8–13)-induced proliferation in BxPC-3 and PANC-1 cells. Confluent cultures of BxPC3 and HT-29 lines exhibited highest expression of NTR1 and lowest of EGFR and expression of NTR1 was maximal at slightly acidic pH e . IL-8 production was stimulated by Lys 8 -ψ-Lys 9 NT (8–13) and even enhanced at both acidic and alkaline pH e in BxPC-3 and PANC-1 cells. In conclusion, our in vitro study suggests that one contributing factor to the minor responses obtained with EGFR-directed therapy may be downregulation of this receptor in tumor cell aggregates, possibly resulting in acquisition of a more aggressive phenotype via other growth factor receptors like NTR1

  19. Low density lipoprotein uptake by an endothelial-smooth muscle cell bilayer

    International Nuclear Information System (INIS)

    Alexander, J.J.; Miguel, R.; Graham, D.

    1991-01-01

    To study the interaction of endothelial and smooth muscle cells, and the means by which such interaction may affect lipid permeability of the arterial wall, cell bilayers were established by use of a transwell culture system. After confluent growth of both cell types had been achieved, iodine 125 bound to low-density lipoprotein (10 ng protein/ml) was added to the media of the upper well. After a 3-hour incubation period, the iodine 125-bound low-density lipoprotein content of the upper and lower media demonstrated an impedance to lipoprotein movement across the endothelial cell monolayer as compared to the bare porous polycarbonate filter of the transwell (p less than 10(-6)). The presence of smooth muscle cells in the bottom well significantly enhanced the permeability of the endothelial cell layer (p less than 10(-60)). This effect remained unchanged over a 9-day time course. Membrane binding and cellular uptake of low-density lipoprotein by endothelial cells was not altered by smooth muscle cells, indicating that this change in permeability could not be easily attributed to changes in receptor-mediated transport or transcytosis. Membrane binding (p less than 0.02) and cellular uptake (p less than 10(-6)) of low-density lipoprotein by smooth muscle cells in the bilayer, when adjusted for counts available in the smooth muscle cell media, were both reduced in the early incubation period as compared to isolated smooth muscle cells. The disproportionate reduction in uptake as compared to binding would suggest that this was not entirely a receptor-dependent process

  20. A generalizable platform for interrogating target- and signal-specific consequences of electrophilic modifications in redox-dependent cell signaling.

    Science.gov (United States)

    Lin, Hong-Yu; Haegele, Joseph A; Disare, Michael T; Lin, Qishan; Aye, Yimon

    2015-05-20

    Despite the known propensity of small-molecule electrophiles to react with numerous cysteine-active proteins, biological actions of individual signal inducers have emerged to be chemotype-specific. To pinpoint and quantify the impacts of modifying one target out of the whole proteome, we develop a target-protein-personalized "electrophile toolbox" with which specific intracellular targets can be selectively modified at a precise time by specific reactive signals. This general methodology, T-REX (targetable reactive electrophiles and oxidants), is established by (1) constructing a platform that can deliver a range of electronic and sterically different bioactive lipid-derived signaling electrophiles to specific proteins in cells; (2) probing the kinetics of targeted delivery concept, which revealed that targeting efficiency in cells is largely driven by initial on-rate of alkylation; and (3) evaluating the consequences of protein-target- and small-molecule-signal-specific modifications on the strength of downstream signaling. These data show that T-REX allows quantitative interrogations into the extent to which the Nrf2 transcription factor-dependent antioxidant response element (ARE) signaling is activated by selective electrophilic modifications on Keap1 protein, one of several redox-sensitive regulators of the Nrf2-ARE axis. The results document Keap1 as a promiscuous electrophile-responsive sensor able to respond with similar efficiencies to discrete electrophilic signals, promoting comparable strength of Nrf2-ARE induction. T-REX is also able to elicit cell activation in cases in which whole-cell electrophile flooding fails to stimulate ARE induction prior to causing cytotoxicity. The platform presents a previously unavailable opportunity to elucidate the functional consequences of small-molecule-signal- and protein-target-specific electrophilic modifications in an otherwise unaffected cellular background.

  1. The impacts of marijuana dispensary density and neighborhood ecology on marijuana abuse and dependence

    Science.gov (United States)

    Mair, Christina; Freisthler, Bridget; Ponicki, William R.; Gaidus, Andrew

    2015-01-01

    Background As an increasing number of states liberalize cannabis use and develop laws and local policies, it is essential to better understand the impacts of neighborhood ecology and marijuana dispensary density on marijuana use, abuse, and dependence. We investigated associations between marijuana abuse/dependence hospitalizations and community demographic and environmental conditions from 2001–2012 in California, as well as cross-sectional associations between local and adjacent marijuana dispensary densities and marijuana hospitalizations. Methods We analyzed panel population data relating hospitalizations coded for marijuana abuse or dependence and assigned to residential ZIP codes in California from 2001 through 2012 (20,219 space-time units) to ZIP code demographic and ecological characteristics. Bayesian space-time misalignment models were used to account for spatial variations in geographic unit definitions over time, while also accounting for spatial autocorrelation using conditional autoregressive priors. We also analyzed cross-sectional associations between marijuana abuse/dependence and the density of dispensaries in local and spatially adjacent ZIP codes in 2012. Results An additional one dispensary per square mile in a ZIP code was cross-sectionally associated with a 6.8% increase in the number of marijuana hospitalizations (95% credible interval 1.033, 1.105) with a marijuana abuse/dependence code. Other local characteristics, such as the median household income and age and racial/ethnic distributions, were associated with marijuana hospitalizations in cross-sectional and panel analyses. Conclusions Prevention and intervention programs for marijuana abuse and dependence may be particularly essential in areas of concentrated disadvantage. Policy makers may want to consider regulations that limit the density of dispensaries. PMID:26154479

  2. Application of the Real-Time Time-Dependent Density Functional Theory to Excited-State Dynamics of Molecules and 2D Materials

    Science.gov (United States)

    Miyamoto, Yoshiyuki; Rubio, Angel

    2018-04-01

    We review our recent developments in the ab initio simulation of excited-state dynamics within the framework of time-dependent density functional theory (TDDFT). Our targets range from molecules to 2D materials, although the methods are general and can be applied to any other finite and periodic systems. We discuss examples of excited-state dynamics obtained by real-time TDDFT coupled with molecular dynamics (MD) and the Ehrenfest approximation, including photoisomerization in molecules, photoenhancement of the weak interatomic attraction of noble gas atoms, photoenhancement of the weak interlayer interaction of 2D materials, pulse-laser-induced local bond breaking of adsorbed atoms on 2D sheets, modulation of UV light intensity by graphene nanoribbons at terahertz frequencies, and collision of high-speed ions with the 2D material to simulate the images taken by He ion microscopy. We illustrate how the real-time TDDFT approach is useful for predicting and understanding non-equilibrium dynamics in condensed matter. We also discuss recent developments that address the excited-state dynamics of systems out of equilibrium and future challenges in this fascinating field of research.

  3. Importance of Sox2 in maintenance of cell proliferation and multipotency of mesenchymal stem cells in low-density culture.

    Science.gov (United States)

    Yoon, D S; Kim, Y H; Jung, H S; Paik, S; Lee, J W

    2011-10-01

    This study has aimed to repopulate 'primitive' cells from late-passage mesenchymal stem cells (MSCs) of poor multipotentiality and low cell proliferation rate, by simply altering plating density. Effects of low density culture compared t high density culture on late-passage bone marrow (BM)-derived MSCs and pluripotency markers of multipotentiality were investigated. Cell proliferation, gene expression, RNA interference and differentiation potential were assayed. We repopulated 'primitive' cells by replating late-passage MSCs at low density (17 cells/cm(2) ) regardless of donor age. Repopulated MSCs from low-density culture were smaller cells with spindle shaped morphology compared to MSCs from high-density culture. The latter had enhanced colony-forming ability, proliferation rate, and adipogenic and chondrogenic potential. Strong expression of osteogenic-related genes (Cbfa1, Dlx5, alkaline phosphatase and type Ι collagen) in late-passage MSCs was reduced by replating at low density, whereas expression of three pluripotency markers (Sox2, Nanog and Oct-4), Osterix and Msx2 reverted to levels of early-passage MSCs. Knockdown of Sox2 and Msx2 but not Nanog, using RNA interference, showed significant decrease in colony-forming ability. Specifically, knockdown of Sox2 significantly inhibited multipotentiality and cell proliferation. Our data suggest that plating density should be considered to be a critical factor for enrichment of 'primitive' cells from heterogeneous BM and that replicative senescence and multipotentiality of MSCs during in vitro expansion may be predominantly regulated through Sox2. © 2011 Blackwell Publishing Ltd.

  4. Colony Development and Density-Dependent Processes in Breeding Grey Herons

    Directory of Open Access Journals (Sweden)

    Takeshi Shirai

    2013-01-01

    Full Text Available The density-dependent processes that limit the colony size of colonially breeding birds such as herons and egrets remain unclear, because it is difficult to monitor colonies from the first year of their establishment, and the most previous studies have considered mixed-species colonies. In the present study, single-species colonies of the Grey Heron (Ardea cinerea were observed from the first year of their establishment for 16 years in suburban Tokyo. Colony size increased after establishment, illustrating a saturation curve. The breeding duration (days from nest building to fledging by a pair increased, but the number of fledglings per nest decreased, with colony size. The reproductive season in each year began earlier, and there was greater variation in the timing of individual breeding when the colony size was larger. The prolonged duration until nestling feeding by early breeders of the colony suggests that herons at the beginning of the new breeding season exist in an unsteady state with one another, likely owing to interactions with immigrant individuals. Such density-dependent interference may affect reproductive success and limit the colony size of Grey Herons.

  5. Discrete density of states

    International Nuclear Information System (INIS)

    Aydin, Alhun; Sisman, Altug

    2016-01-01

    By considering the quantum-mechanically minimum allowable energy interval, we exactly count number of states (NOS) and introduce discrete density of states (DOS) concept for a particle in a box for various dimensions. Expressions for bounded and unbounded continua are analytically recovered from discrete ones. Even though substantial fluctuations prevail in discrete DOS, they're almost completely flattened out after summation or integration operation. It's seen that relative errors of analytical expressions of bounded/unbounded continua rapidly decrease for high NOS values (weak confinement or high energy conditions), while the proposed analytical expressions based on Weyl's conjecture always preserve their lower error characteristic. - Highlights: • Discrete density of states considering minimum energy difference is proposed. • Analytical DOS and NOS formulas based on Weyl conjecture are given. • Discrete DOS and NOS functions are examined for various dimensions. • Relative errors of analytical formulas are much better than the conventional ones.

  6. One-dimensional time-dependent fluid model of a very high density low-pressure inductively coupled plasma

    Science.gov (United States)

    Chaplin, Vernon H.; Bellan, Paul M.

    2015-12-01

    A time-dependent two-fluid model has been developed to understand axial variations in the plasma parameters in a very high density (peak ne≳ 5 ×1019 m-3 ) argon inductively coupled discharge in a long 1.1 cm radius tube. The model equations are written in 1D with radial losses to the tube walls accounted for by the inclusion of effective particle and energy sink terms. The ambipolar diffusion equation and electron energy equation are solved to find the electron density ne(z ,t ) and temperature Te(z ,t ) , and the populations of the neutral argon 4s metastable, 4s resonant, and 4p excited state manifolds are calculated to determine the stepwise ionization rate and calculate radiative energy losses. The model has been validated through comparisons with Langmuir probe ion saturation current measurements; close agreement between the simulated and measured axial plasma density profiles and the initial density rise rate at each location was obtained at pA r=30 -60 mTorr . We present detailed results from calculations at 60 mTorr, including the time-dependent electron temperature, excited state populations, and energy budget within and downstream of the radiofrequency antenna.

  7. Study of nuclear level density parameter and its temperature dependence

    International Nuclear Information System (INIS)

    Nasrabadi, M. N.; Behkami, A. N.

    2000-01-01

    The nuclear level density ρ is the basic ingredient required for theoretical studies of nuclear reaction and structure. It describes the statistical nuclear properties and is expressed as a function of various constants of motion such as number of particles, excitation energy and angular momentum. In this work the energy and spin dependence of nuclear level density will be presented and discussed. In addition the level density parameter α will be extracted from this level density information, and its temperature and mass dependence will be obtained

  8. Temperature dependent spin momentum densities in Ni-Mn-In alloys

    International Nuclear Information System (INIS)

    Ahuja, B L; Dashora, Alpa; Vadkhiya, L; Heda, N L; Priolkar, K R; Lobo, Nelson; Itou, M; Sakurai, Y; Chakrabarti, Aparna; Singh, Sanjay; Barman, S R

    2010-01-01

    The spin-dependent electron momentum densities in Ni 2 MnIn and Ni 2 Mn 1.4 In 0.6 shape memory alloy using magnetic Compton scattering with 182.2 keV circularly polarized synchrotron radiation are reported. The magnetic Compton profiles were measured at different temperatures ranging between 10 and 300 K. The profiles have been analyzed mainly in terms of Mn 3d electrons to determine their role in the formation of the total spin moment. We have also computed the spin polarized energy bands, partial and total density of states, Fermi surfaces and spin moments using full potential linearized augmented plane wave and spin polarized relativistic Korringa-Kohn-Rostoker methods. The total spin moments obtained from our magnetic Compton profile data are explained using both the band structure models. The present Compton scattering investigations are also compared with magnetization measurements.

  9. and density-dependent quark mass model

    Indian Academy of Sciences (India)

    Since a fair proportion of such dense proto stars are likely to be ... the temperature- and density-dependent quark mass (TDDQM) model which we had em- ployed in .... instead of Tc ~170 MeV which is a favoured value for the ud matter [26].

  10. The CD8+ memory T-cell state of readiness is actively maintained and reversible

    Science.gov (United States)

    Allam, Atef; Conze, Dietrich B.; Giardino Torchia, Maria Letizia; Munitic, Ivana; Yagita, Hideo; Sowell, Ryan T.; Marzo, Amanda L.

    2009-01-01

    The ability of the adaptive immune system to respond rapidly and robustly upon repeated antigen exposure is known as immunologic memory, and it is thought that acquisition of memory T-cell function is an irreversible differentiation event. In this study, we report that many phenotypic and functional characteristics of antigen-specific CD8 memory T cells are lost when they are deprived of contact with dendritic cells. Under these circumstances, memory T cells reverted from G1 to the G0 cell-cycle state and responded to stimulation like naive T cells, as assessed by proliferation, dependence upon costimulation, and interferon-γ production, without losing cell surface markers associated with memory. The memory state was maintained by signaling via members of the tumor necrosis factor receptor superfamily, CD27 and 4-1BB. Foxo1, a transcription factor involved in T-cell quiescence, was reduced in memory cells, and stimulation of naive CD8 cells via CD27 caused Foxo1 to be phosphorylated and emigrate from the nucleus in a phosphatidylinositol-3 kinase–dependent manner. Consistent with these results, maintenance of G1 in vivo was compromised in antigen-specific memory T cells in vesicular stomatitis virus-infected CD27-deficient mice. Therefore, sustaining the functional phenotype of T memory cells requires active signaling and maintenance. PMID:19617575

  11. Model for the orientation, magnetic field, and temperature dependence of the specific heat of CeCu6

    International Nuclear Information System (INIS)

    Edelstein, A.S.

    1988-01-01

    The results of a model calculation of the orientation, magnetic field, and temperature dependence of the specific heat C of CeCu 6 are found to be in good agreement with the single-crystal data of Amato et al. The model incorporates both the Kondo and crystal-field effects. It is suggested that the low-temperature Wilson's ratio CTchi, where chi is the susceptibility, may not change in an applied field H and that both CT and chi at low temperatures as a function of H may be proportional to the many-body density of states at the energy μH

  12. Information geometry of density matrices and state estimation

    International Nuclear Information System (INIS)

    Brody, Dorje C

    2011-01-01

    Given a pure state vector |x) and a density matrix ρ-hat, the function p(x|ρ-hat)= defines a probability density on the space of pure states parameterised by density matrices. The associated Fisher-Rao information measure is used to define a unitary invariant Riemannian metric on the space of density matrices. An alternative derivation of the metric, based on square-root density matrices and trace norms, is provided. This is applied to the problem of quantum-state estimation. In the simplest case of unitary parameter estimation, new higher-order corrections to the uncertainty relations, applicable to general mixed states, are derived. (fast track communication)

  13. Roles of density-dependent growth and life history evolution in accounting for fisheries-induced trait changes.

    Science.gov (United States)

    Eikeset, Anne Maria; Dunlop, Erin S; Heino, Mikko; Storvik, Geir; Stenseth, Nils C; Dieckmann, Ulf

    2016-12-27

    The relative roles of density dependence and life history evolution in contributing to rapid fisheries-induced trait changes remain debated. In the 1930s, northeast Arctic cod (Gadus morhua), currently the world's largest cod stock, experienced a shift from a traditional spawning-ground fishery to an industrial trawl fishery with elevated exploitation in the stock's feeding grounds. Since then, age and length at maturation have declined dramatically, a trend paralleled in other exploited stocks worldwide. These trends can be explained by demographic truncation of the population's age structure, phenotypic plasticity in maturation arising through density-dependent growth, fisheries-induced evolution favoring faster-growing or earlier-maturing fish, or a combination of these processes. Here, we use a multitrait eco-evolutionary model to assess the capacity of these processes to reproduce 74 y of historical data on age and length at maturation in northeast Arctic cod, while mimicking the stock's historical harvesting regime. Our results show that model predictions critically depend on the assumed density dependence of growth: when this is weak, life history evolution might be necessary to prevent stock collapse, whereas when a stronger density dependence estimated from recent data is used, the role of evolution in explaining fisheries-induced trait changes is diminished. Our integrative analysis of density-dependent growth, multitrait evolution, and stock-specific time series data underscores the importance of jointly considering evolutionary and ecological processes, enabling a more comprehensive perspective on empirically observed stock dynamics than previous studies could provide.

  14. Temperature and carrier density dependence of anisotropy in supercurrent density in layered cuprate superconductors

    International Nuclear Information System (INIS)

    Singh, M.P.; Tewari, B.S.; Ajay

    2006-01-01

    In the present work, we have studied the effect of temperature and carrier density on anisotropy in supercurrent density in bilayer cuprate superconductors. Here, we have considered a tight binding bilayered Hubbard Hamiltonian containing intra and interlayer attractive interactions. The situation considered here is similar to a SIS junction. We have got the expressions for the superconducting order parameters, carrier density and anisotropy in superconducting density (I ab /I c ) for such SIS junction. The numerical analysis show that the anisotropy in the supercurrent density depends on temperature and carrier density in layered high T c cuprates. (author)

  15. Mechanisms of cross-suppression of TNP-specific plaque forming cell responses by TMA-specific first-order T suppressor factor

    Energy Technology Data Exchange (ETDEWEB)

    Jendrisak, G.S.; Bellone, C.J.

    1986-03-05

    The addition of hybridoma-derived phenyltrimethylammonium (TMA)-specific first-order T suppressor factor (TsF/sub 1/) into cultures containing Brucella abortus coupled with the TMA and trinitrophenol haptens (TMA-BA-TNP) results in the cross-suppression of TNP-specific plaque forming cell (PFC) responses. The suppression mediated by TMA-TsF/sub 1/ is dependent on the presence of T cells and specific antigen (TMA). Subculturing of whole spleen cells with TMA-TsF/sub 1/ and specific soluble antigen (TMA-BSA) is able to induce suppressor T cells which cross-suppress the TNP-specific PFC of spleen cell cultures stimulated with TMA-BA-TNP in an antigen (TMA)-dependent manner at the effector phase of the response. The effector acting T suppressor cells (Tse) are nylon wool nonadherent and appears to require whole spleen cells in responding cultures for suppression, suggesting that the target of the Tse is not the TNP-specific B cell. The authors are presently characterizing the mechanisms of cross-suppression by TMA-TsF/sub 1/ and Tse utilizing the described primary in vitro antibody assay.

  16. Density-dependent quiescence in glioma invasion: instability in a simple reaction–diffusion model for the migration/proliferation dichotomy

    KAUST Repository

    Pham, Kara

    2012-01-01

    Gliomas are very aggressive brain tumours, in which tumour cells gain the ability to penetrate the surrounding normal tissue. The invasion mechanisms of this type of tumour remain to be elucidated. Our work is motivated by the migration/proliferation dichotomy (go-or-grow) hypothesis, i.e. the antagonistic migratory and proliferating cellular behaviours in a cell population, which may play a central role in these tumours. In this paper, we formulate a simple go-or-grow model to investigate the dynamics of a population of glioma cells for which the switch from a migratory to a proliferating phenotype (and vice versa) depends on the local cell density. The model consists of two reaction-diffusion equations describing cell migration, proliferation and a phenotypic switch. We use a combination of numerical and analytical techniques to characterize the development of spatio-temporal instabilities and travelling wave solutions generated by our model. We demonstrate that the density-dependent go-or-grow mechanism can produce complex dynamics similar to those associated with tumour heterogeneity and invasion.

  17. Discrete density of states

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, Alhun; Sisman, Altug, E-mail: sismanal@itu.edu.tr

    2016-03-22

    By considering the quantum-mechanically minimum allowable energy interval, we exactly count number of states (NOS) and introduce discrete density of states (DOS) concept for a particle in a box for various dimensions. Expressions for bounded and unbounded continua are analytically recovered from discrete ones. Even though substantial fluctuations prevail in discrete DOS, they're almost completely flattened out after summation or integration operation. It's seen that relative errors of analytical expressions of bounded/unbounded continua rapidly decrease for high NOS values (weak confinement or high energy conditions), while the proposed analytical expressions based on Weyl's conjecture always preserve their lower error characteristic. - Highlights: • Discrete density of states considering minimum energy difference is proposed. • Analytical DOS and NOS formulas based on Weyl conjecture are given. • Discrete DOS and NOS functions are examined for various dimensions. • Relative errors of analytical formulas are much better than the conventional ones.

  18. A dimensionless ordered pull-through model of the mammalian lens epithelium evidences scaling across species and explains the age-dependent changes in cell density in the human lens

    Science.gov (United States)

    Wu, Jun Jie; Wu, Weiju; Tholozan, Frederique M.; Saunter, Christopher D.; Girkin, John M.; Quinlan, Roy A.

    2015-01-01

    We present a mathematical (ordered pull-through; OPT) model of the cell-density profile for the mammalian lens epithelium together with new experimental data. The model is based upon dimensionless parameters, an important criterion for inter-species comparisons where lens sizes can vary greatly (e.g. bovine (approx. 18 mm); mouse (approx. 2 mm)) and confirms that mammalian lenses scale with size. The validated model includes two parameters: β/α, which is the ratio of the proliferation rate in the peripheral and in the central region of the lens; and γGZ, a dimensionless pull-through parameter that accounts for the cell transition and exit from the epithelium into the lens body. Best-fit values were determined for mouse, rat, rabbit, bovine and human lens epithelia. The OPT model accounts for the peak in cell density at the periphery of the lens epithelium, a region where cell proliferation is concentrated and reaches a maximum coincident with the germinative zone. The β/α ratio correlates with the measured FGF-2 gradient, a morphogen critical to lens cell survival, proliferation and differentiation. As proliferation declines with age, the OPT model predicted age-dependent changes in cell-density profiles, which we observed in mouse and human lenses. PMID:26236824

  19. Performance of conversion efficiency of a crystalline silicon solar cell with base doping density

    Directory of Open Access Journals (Sweden)

    Gokhan Sahin

    Full Text Available In this study, we investigate theoretically the electrical parameters of a crystalline silicon solar cell in steady state. Based on a one-dimensional modeling of the cell, the short circuit current density, the open circuit voltage, the shunt and series resistances and the conversion efficiency are calculated, taking into account the base doping density. Either the I-V characteristic, series resistance, shunt resistance and conversion efficiency are determined and studied versus base doping density. The effects applied of base doping density on these parameters have been studied. The aim of this work is to show how short circuit current density, open circuit voltage and parasitic resistances are related to the base doping density and to exhibit the role played by those parasitic resistances on the conversion efficiency of the crystalline silicon solar. Keywords: Crystalline silicon solar cell, Base doping density, Series resistance, Shunt resistance, Conversion efficiency

  20. Density Dependence of Particle Transport in ECH Plasmas of the TJ-II Stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, V. I.; Lopez-Bruna, D.; Guasp, J.; Herranz, J.; Estrada, T.; Medina, F.; Ochando, M.A.; Velasco, J.L.; Reynolds, J.M.; Ferreira, J.A.; Tafalla, D.; Castejon, F.; Salas, A.

    2009-05-21

    We present the experimental dependence of particle transport on average density in electron cyclotron heated (ECH) hydrogen plasmas of the TJ-II stellarator. The results are based on: (I) electron density and temperature data from Thomson Scattering and reflectometry diagnostics; (II) a transport model that reproduces the particle density profiles in steady state; and (III) Eirene, a code for neutrals transport that calculates the particle source in the plasma from the particle confinement time and the appropriate geometry of the machine/plasma. After estimating an effective particle diffusivity and the particle confinement time, a threshold density separating qualitatively and quantitatively different plasma transport regimes is found. The poor confinement times found below the threshold are coincident with the presence of ECH-induced fast electron losses and a positive radial electric field all over the plasma. (Author) 40 refs.

  1. Cell culture density affects the proliferation activity of human adipose tissue stem cells.

    Science.gov (United States)

    Kim, Dae Seong; Lee, Myoung Woo; Ko, Young Jong; Chun, Yong Hoon; Kim, Hyung Joon; Sung, Ki Woong; Koo, Hong Hoe; Yoo, Keon Hee

    2016-01-01

    In this study, we investigated the effect of cell density on the proliferation activity of human mesenchymal stem cells (MSCs) derived from adipose tissue (AT-MSCs) over time in culture. Passage #4 (P4) and #12 (P12) AT-MSCs from two donors were plated at a density of 200 (culture condition 1, CC1) or 5000 (culture condition 2, CC2) cells cm(-2) . After 7 days of incubation, P4 and P12 AT-MSCs cultured in CC1 were thin and spindle-shaped, whereas those cultured in CC2 had extensive cell-to-cell contacts and an expanded cell volume. In addition, P4 and P12 AT-MSCs in CC1 divided more than three times, while those in CC2 divided less than once on average. Flow cytometric analysis using 5(6)-carboxyfluorescein diacetate N-succinimidyl ester dye showed that the fluorescence intensity of AT-MSCs was lower in CC1 than in CC2. Furthermore, expression of proliferation-associated genes, such as CDC45L, CDC20A and KIF20A, in P4 AT-MSCs was higher in CC1 than in CC2, and this difference was also observed in P12 AT-MSCs. These data demonstrated that cell culture density affects the proliferation activity of MSCs, suggesting that it is feasible to design a strategy to prepare suitable MSCs using specific culture conditions. Copyright © 2016 John Wiley & Sons, Ltd.

  2. Continuum corrections to the level density and its dependence on excitation energy, n-p asymmetry, and deformation

    International Nuclear Information System (INIS)

    Charity, R.J.; Sobotka, L.G.

    2005-01-01

    In the independent-particle model, the nuclear level density is determined from the neutron and proton single-particle level densities. The single-particle level density for the positive-energy continuum levels is important at high excitation energies for stable nuclei and at all excitation energies for nuclei near the drip lines. This single-particle level density is subdivided into compound-nucleus and gas components. Two methods are considered for this subdivision: In the subtraction method, the single-particle level density is determined from the scattering phase shifts. In the Gamov method, only the narrow Gamov states or resonances are included. The level densities calculated with these two methods are similar; both can be approximated by the backshifted Fermi-gas expression with level-density parameters that are dependent on A, but with very little dependence on the neutron or proton richness of the nucleus. However, a small decrease in the level-density parameter is predicted for some nuclei very close to the drip lines. The largest difference between the calculations using the two methods is the deformation dependence of the level density. The Gamov method predicts a very strong peaking of the level density at sphericity for high excitation energies. This leads to a suppression of deformed configurations and, consequently, the fission rate predicted by the statistical model is reduced in the Gamov method

  3. Cell-Type-Specific Circuit Connectivity of Hippocampal CA1 Revealed through Cre-Dependent Rabies Tracing

    Directory of Open Access Journals (Sweden)

    Yanjun Sun

    2014-04-01

    Full Text Available We developed and applied a Cre-dependent, genetically modified rabies-based tracing system to map direct synaptic connections to specific CA1 neuron types in the mouse hippocampus. We found common inputs to excitatory and inhibitory CA1 neurons from CA3, CA2, the entorhinal cortex (EC, the medial septum (MS, and, unexpectedly, the subiculum. Excitatory CA1 neurons receive inputs from both cholinergic and GABAergic MS neurons, whereas inhibitory neurons receive a great majority of inputs from GABAergic MS neurons. Both cell types also receive weaker input from glutamatergic MS neurons. Comparisons of inputs to CA1 PV+ interneurons versus SOM+ interneurons showed similar strengths of input from the subiculum, but PV+ interneurons received much stronger input than SOM+ neurons from CA3, the EC, and the MS. Thus, rabies tracing identifies hippocampal circuit connections and maps how the different input sources to CA1 are distributed with different strengths on each of its constituent cell types.

  4. Cell Seeding Densities in Autologous Chondrocyte Implantation Techniques for Cartilage Repair.

    Science.gov (United States)

    Foldager, Casper Bindzus; Gomoll, Andreas H; Lind, Martin; Spector, Myron

    2012-04-01

    Cartilage repair techniques have been among the most intensively investigated treatments in orthopedics for the past decade, and several different treatment modalities are currently available. Despite the extensive research effort within this field, the generation of hyaline cartilage remains a considerable challenge. There are many parameters attendant to each of the cartilage repair techniques that can affect the amount and types of reparative tissue generated in the cartilage defect, and some of the most fundamental of these parameters have yet to be fully investigated. For procedures in which in vitro-cultured autologous chondrocytes are implanted under a periosteal or synthetic membrane cover, or seeded onto a porous membrane or scaffold, little is known about how the number of cells affects the clinical outcome. Few published clinical studies address the cell seeding density that was employed. The principal objective of this review is to provide an overview of the cell seeding densities used in cell-based treatments currently available in the clinic for cartilage repair. Select preclinical studies that have informed the use of specific cell seeding densities in the clinic are also discussed.

  5. Evaluating the B-cell density with various activation functions using White Noise Path Integral Approach

    Science.gov (United States)

    Aban, C. J. G.; Bacolod, R. O.; Confesor, M. N. P.

    2015-06-01

    A The White Noise Path Integral Approach is used in evaluating the B-cell density or the number of B-cell per unit volume for a basic type of immune system response based on the modeling done by Perelson and Wiegel. From the scaling principles of Perelson [1], the B- cell density is obtained where antigens and antibodies mutates and activation function f(|S-SA|) is defined describing the interaction between a specific antigen and a B-cell. If the activation function f(|S-SA|) is held constant, the major form of the B-cell density evaluated using white noise analysis is similar to the form of the B-cell density obtained by Perelson and Wiegel using a differential approach.A piecewise linear functionis also used to describe the activation f(|S-SA|). If f(|S-SA|) is zero, the density decreases exponentially. If f(|S-SA|) = S-SA-SB, the B- cell density increases exponentially until it reaches a certain maximum value. For f(|S-SA|) = 2SA-SB-S, the behavior of B-cell density is oscillating and remains to be in small values.

  6. Density and temperature dependence of carrier dynamics in self-organized InGaAs quantum dots

    International Nuclear Information System (INIS)

    Norris, T B; Kim, K; Urayama, J; Wu, Z K; Singh, J; Bhattacharya, P K

    2005-01-01

    We have used two- and three-pulse femtosecond differential transmission spectroscopy to study the dependence of quantum dot carrier dynamics on temperature. At low temperatures and densities, the rates for relaxation between the quantum dot confined states and for capture from the barrier region into the various dot levels could be directly determined. For electron-hole pairs generated directly in the quantum dot excited state, relaxation is dominated by electron-hole scattering, and occurs on a 5 ps time scale. Capture times from the barrier into the quantum dot are of the order of 2 ps (into the excited state) and 10 ps (into the ground state). The phonon bottleneck was clearly observed in low-density capture experiments, and the conditions for its observation (namely, the suppression of electron-hole scattering for nongeminately captured electrons) were determined. As temperature increases beyond about 100 K, the dynamics become dominated by the re-emission of carriers from the lower dot levels, due to the large density of states in the wetting layer and barrier region. Measurements of the gain dynamics show fast (130 fs) gain recovery due to intradot carrier-carrier scattering, and picosecond-scale capture. Direct measurement of the transparency density versus temperature shows the dramatic effect of carrier re-emission for the quantum dots on thermally activated scattering. The carrier dynamics at elevated temperature are thus strongly dominated by the high density of the high energy continuum states relative to the dot confined levels. Deleterious hot carrier effects can be suppressed in quantum dot lasers by resonant tunnelling injection

  7. Quantum electrodynamical time-dependent density functional theory for many-electron systems on a lattice

    Science.gov (United States)

    Farzanehpour, Mehdi; Tokatly, Ilya; Nano-Bio Spectroscopy Group; ETSF Scientific Development Centre Team

    2015-03-01

    We present a rigorous formulation of the time-dependent density functional theory for interacting lattice electrons strongly coupled to cavity photons. We start with an example of one particle on a Hubbard dimer coupled to a single photonic mode, which is equivalent to the single mode spin-boson model or the quantum Rabi model. For this system we prove that the electron-photon wave function is a unique functional of the electronic density and the expectation value of the photonic coordinate, provided the initial state and the density satisfy a set of well defined conditions. Then we generalize the formalism to many interacting electrons on a lattice coupled to multiple photonic modes and prove the general mapping theorem. We also show that for a system evolving from the ground state of a lattice Hamiltonian any density with a continuous second time derivative is locally v-representable. Spanish Ministry of Economy and Competitiveness (Grant No. FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT578-13), COST Actions CM1204 (XLIC) and MP1306 (EUSpec).

  8. Does density-dependent diversification mirror ecological competitive exclusion?

    Directory of Open Access Journals (Sweden)

    Melanie J Monroe

    Full Text Available Density-dependence is a term used in ecology to describe processes such as birth and death rates that are regulated by the number of individuals in a population. Evolutionary biologists have borrowed the term to describe decreasing rates of species accumulation, suggesting that speciation and extinction rates depend on the total number of species in a clade. If this analogy with ecological density-dependence holds, diversification of clades is restricted because species compete for limited resources. We hypothesize that such competition should not only affect numbers of species, but also prevent species from being phenotypically similar. Here, we present a method to detect whether competitive interactions between species have ordered phenotypic traits on a phylogeny, assuming that competition prevents related species from having identical trait values. We use the method to analyze clades of birds and mammals, with body size as the phenotypic trait. We find no sign that competition has prevented species from having the same body size. Thus, since body size is a key ecological trait and competition does not seem to be responsible for differences in body size between species, we conclude that the diversification slowdown that is prevalent in these clades is unlikely due to the ecological interference implied by the term density dependence.

  9. Influence of tracks densities in solid state nuclear track detectors

    International Nuclear Information System (INIS)

    Guedes O, S.; Hadler N.; Lunes, P.; Saenz T, C.

    1996-01-01

    When Solid State Nuclear Track Detectors (SSNTD) is employed to measure nuclear tracks produced mainly by fission fragments and alpha particles, it is considered that the tracks observation work is performed under an efficiency, ε 0 , which is independent of the track density (number of tracks/area unit). There are not published results or experimental data supporting such an assumption. In this work the dependence of ε 0 with track density is studied basing on experimental data. To perform this, pieces of CR-39 cut from a sole 'mother sheet' were coupled to thin uranium films for different exposition times and the resulting ratios between track density and exposition time were compared. Our results indicate that ε 0 is constant for track densities between 10 3 and 10 5 cm -2 . At our etching conditions track overlapping makes impossible the counting for densities around 1.7 x 10 5 cm -2 . For track densities less than 10 3 cm -2 , ε 0 , was not observed to be constant. (authors). 4 refs., 2 figs

  10. Charge carrier transport in Cu(In,Ga)Se2 thin-film solar-cells studied by electron beam induced current and temperature and illumination dependent current voltage analysis

    International Nuclear Information System (INIS)

    Nichterwitz, Melanie

    2012-01-01

    This work contributes to the understanding of generation dependent charge-carrier transport properties in Cu(In,Ga)Se 2 (CIGSe)/ CdS/ ZnO solar cells and a consistent model for the electronic band diagram of the heterojunction region of the device is developed. Cross section electron-beam induced current (EBIC) and temperature and illumination dependent current voltage (IV) measurements are performed on CIGSe solar cells with varying absorber layer compositions and CdS thickness. For a better understanding of possibilities and limitations of EBIC measurements applied on CIGSe solar cells, detailed numerical simulations of cross section EBIC profiles for varying electron beam and solar cell parameters are performed and compared to profiles obtained from an analytical description. Especially the effects of high injection conditions are considered. Even though the collection function of the solar cell is not independent of the generation function of the electron beam, the local electron diffusion length in CIGSe can still be extracted. Grain specific values ranging from (480±70) nm to (2.3±0.2) μm are determined for a CuInSe 2 absorber layer and a value of (2.8±0.3) μm for CIGSe with a Ga-content of 0.3. There are several models discussed in literature to explain generation dependent charge carrier transport, all assuming a high acceptor density either located in the CIGSe layer close to the CIGSe/CdS interface (p + layer), within the CdS layer or at the CdS/ZnO interface. In all models, a change in charge carrier collection properties is caused by a generation dependent occupation probability of the acceptor type defect state and the resulting potential distribution throughout the device. Numerical simulations of EBIC and IV data are performed with parameters according to these models. The model that explains the experimental data best is that of a p + layer at the CIGSe/CdS interface and acceptor type defect states at the CdS/ZnO interface. The p + layer leads

  11. Evolution of density-dependent movement during experimental range expansions.

    Science.gov (United States)

    Fronhofer, E A; Gut, S; Altermatt, F

    2017-12-01

    Range expansions and biological invasions are prime examples of transient processes that are likely impacted by rapid evolutionary changes. As a spatial process, range expansions are driven by dispersal and movement behaviour. Although it is widely accepted that dispersal and movement may be context-dependent, for instance density-dependent, and best represented by reaction norms, the evolution of density-dependent movement during range expansions has received little experimental attention. We therefore tested current theory predicting the evolution of increased movement at low densities at range margins using highly replicated and controlled range expansion experiments across multiple genotypes of the protist model system Tetrahymena thermophila. Although rare, we found evolutionary changes during range expansions even in the absence of initial standing genetic variation. Range expansions led to the evolution of negatively density-dependent movement at range margins. In addition, we report the evolution of increased intrastrain competitive ability and concurrently decreased population growth rates in range cores. Our findings highlight the importance of understanding movement and dispersal as evolving reaction norms and plastic life-history traits of central relevance for range expansions, biological invasions and the dynamics of spatially structured systems in general. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

  12. Accurate Ground-State Energies of Solids and Molecules from Time-Dependent Density-Functional Theory

    DEFF Research Database (Denmark)

    Olsen, Thomas; Thygesen, Kristian Sommer

    2014-01-01

    We demonstrate that ground-state energies approaching chemical accuracy can be obtained by combining the adiabatic-connection fluctuation-dissipation theorem with time-dependent densityfunctional theory. The key ingredient is a renormalization scheme, which eliminates the divergence...

  13. Critique of the foundations of time-dependent density-functional theory

    International Nuclear Information System (INIS)

    Schirmer, J.; Dreuw, A.

    2007-01-01

    The general expectation that, in principle, the time-dependent density-functional theory (TDDFT) is an exact formulation of the time evolution of an interacting N-electron system is critically reexamined. It is demonstrated that the previous TDDFT foundation, resting on four theorems by Runge and Gross (RG) [Phys. Rev. Lett. 52, 997 (1984)], is invalid because undefined phase factors corrupt the RG action integral functionals. Our finding confirms much of a previous analysis by van Leeuwen [Int. J. Mod. Phys. B 15, 1969 (2001)]. To analyze the RG theorems and other aspects of TDDFT, an utmost simplification of the Kohn-Sham (KS) concept has been introduced, in which the ground-state density is obtained from a single KS equation for one spatial (spinless) orbital. The time-dependent (TD) form of this radical Kohn-Sham (rKS) scheme, which has the same validity status as the ordinary KS version, has proved to be a valuable tool for analysis. The rKS concept is used to clarify also the alternative nonvariational formulation of TD KS theory. We argue that it is just a formal theory, allowing one to reproduce but not predict the time development of the exact density of the interacting N-electron system. Besides the issue of the formal exactness of TDDFT, it is shown that both the static and time-dependent KS linear response equations neglect the particle-particle (p-p) and hole-hole (h-h) matrix elements of the perturbing operator. For a local (multiplicative) operator this does not lead to a loss of information due to a remarkable general property of local operators. Accordingly, no logical inconsistency arises with respect to DFT, because DFT requires any external potential to be local. For a general nonlocal operator the error resulting from the neglected matrix elements is of second order in the electronic repulsion

  14. Pressure-Dependent Electronic and Transport Properties of Bulk Platinum Oxide by Density Functional Theory

    Science.gov (United States)

    Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh; Nekrasov, Kirill A.; Kichigina, Natalia V.

    2018-02-01

    The structural, electronic, and vibrational properties of bulk platinum oxide (PtO) at compressive pressures in the interval from 0 GPa to 35 GPa are investigated using the density functional theory. The calculated electronic band structure of PtO shows poor metallicity at very low density of states on the Fermi level. However, the hybrid pseudopotential calculation yielded 0.78 eV and 1.30 eV direct band and indirect gap, respectively. Importantly, our results predict that PtO has a direct band gap within the framework of HSE06, and it prefers equally zero magnetic order at different pressures. In the Raman spectra, peaks are slightly shifted towards higher frequency with the decrease in pressure. We have also calculated the thermoelectric properties, namely the electronic thermal conductivity and electrical conductivity, with respect to temperature and thermodynamic properties such as entropy, specific heat at constant volume, enthalpy and Gibbs free energy with respect to pressure. The result shows that PtO is a promising candidate for use as a catalyst, in sensors, as a photo-cathode in water electrolysis, for thermal decomposition of inorganic salt and fuel cells.

  15. Duodenal L cell density correlates with features of metabolic syndrome and plasma metabolites

    Directory of Open Access Journals (Sweden)

    Annieke C G van Baar

    2018-05-01

    Full Text Available Background: Enteroendocrine cells are essential for the regulation of glucose metabolism, but it is unknown whether they are associated with clinical features of metabolic syndrome (MetS and fasting plasma metabolites. Objective: We aimed to identify fasting plasma metabolites that associate with duodenal L cell, K cell and delta cell densities in subjects with MetS with ranging levels of insulin resistance. Research design and methods: In this cross-sectional study, we evaluated L, K and delta cell density in duodenal biopsies from treatment-naïve males with MetS using machine-learning methodology. Results: We identified specific clinical biomarkers and plasma metabolites associated with L cell and delta cell density. L cell density was associated with increased plasma metabolite levels including symmetrical dimethylarginine, 3-aminoisobutyric acid, kynurenine and glycine. In turn, these L cell-linked fasting plasma metabolites correlated with clinical features of MetS. Conclusions: Our results indicate a link between duodenal L cells, plasma metabolites and clinical characteristics of MetS. We conclude that duodenal L cells associate with plasma metabolites that have been implicated in human glucose metabolism homeostasis. Disentangling the causal relation between L cells and these metabolites might help to improve the (small intestinal-driven pathophysiology behind insulin resistance in human obesity.

  16. Density dependence in a recovering osprey population: demographic and behavioural processes.

    Science.gov (United States)

    Bretagnolle, V; Mougeot, F; Thibault, J-C

    2008-09-01

    1. Understanding how density-dependent and independent processes influence demographic parameters, and hence regulate population size, is fundamental within population ecology. We investigated density dependence in growth rate and fecundity in a recovering population of a semicolonial raptor, the osprey Pandion haliaetus [Linnaeus, 1758], using 31 years of count and demographic data in Corsica. 2. The study population increased from three pairs in 1974 to an average of 22 pairs in the late 1990s, with two distinct phases during the recovery (increase followed by stability) and contrasted trends in breeding parameters in each phase. 3. We show density dependence in population growth rate in the second phase, indicating that the stabilized population was regulated. We also show density dependence in productivity (fledging success between years and hatching success within years). 4. Using long-term data on behavioural interactions at nest sites, and on diet and fish provisioning rate, we evaluated two possible mechanisms of density dependence in productivity, food depletion and behavioural interference. 5. As density increased, both provisioning rate and the size of prey increased, contrary to predictions of a food-depletion mechanism. In the time series, a reduction in fledging success coincided with an increase in the number of non-breeders. Hatching success decreased with increasing local density and frequency of interactions with conspecifics, suggesting that behavioural interference was influencing hatching success. 6. Our study shows that, taking into account the role of non-breeders, in particular in species or populations where there are many floaters and where competition for nest sites is intense, can improve our understanding of density-dependent processes and help conservation actions.

  17. Specific heat of the 38-K superconductor MgB_2 in the normal and superconducting state: bulk evidence for a double gap

    OpenAIRE

    Junod, Alain; Wang, Yuxing; Bouquet, Frederic; Toulemonde, Pierre

    2001-01-01

    The specific heat of two polycrystalline samples of MgB_2 is presented and analyzed (2 - 300 K, 0 - 16 T), together with magnetic properties. The main characteristics are a low density of states at the Fermi level, high phonon frequencies, and an anomalous temperature- and field- dependence of the specific heat at T < T_c. A two-gap model with a gap ratio of 3:1 fits the specific heat in zero field. The smaller gap is washed out by a field of 0.5 T.

  18. Epidermal growth factor receptor mediated proliferation depends on increased lipid droplet density regulated via a negative regulatory loop with FOXO3/Sirtuin6

    Energy Technology Data Exchange (ETDEWEB)

    Penrose, Harrison; Heller, Sandra; Cable, Chloe [Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, 1430 Tulane Ave SL-79, New Orleans, LA 70112 (United States); Makboul, Rania [Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, 1430 Tulane Ave SL-79, New Orleans, LA 70112 (United States); Pathology Department, Assiut University, Assiut (Egypt); Chadalawada, Gita; Chen, Ying [Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, 1430 Tulane Ave SL-79, New Orleans, LA 70112 (United States); Crawford, Susan E. [Department of Pathology, Saint Louis University School of Medicine, 1402 South Grand Blvd, Saint Louis, MO 63104 (United States); Savkovic, Suzana D., E-mail: ssavkovi@tulane.edu [Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, 1430 Tulane Ave SL-79, New Orleans, LA 70112 (United States)

    2016-01-15

    The proliferation of colon cancer cells is mediated in part by epidermal growth factor receptor (EGFR) signaling and requires sustained levels of cellular energy to meet its high metabolic needs. Intracellular lipid droplets (LDs) are a source of energy used for various cellular functions and they are elevated in density in human cancer, yet their regulation and function are not well understood. Here, in human colon cancer cells, EGF stimulates increases in LD density, which depends on EGFR expression and activation as well as the individual cellular capacity for lipid synthesis. Increases in LDs are blockaded by inhibition of PI3K/mTOR and PGE2 synthesis, supporting their dependency on select upstream pathways. In colon cancer cells, silencing of the FOXO3 transcription factor leads to down regulation of SIRT6, a negative regulator of lipid synthesis, and consequent increases in the LD coat protein PLIN2, revealing that increases in LDs depend on loss of FOXO3/SIRT6. Moreover, EGF stimulates loss of FOXO3/SIRT6, which is blockaded by the inhibition of upstream pathways as well as lipid synthesis, revealing existence of a negative regulatory loop between LDs and FOXO3/SIRT6. Elevated LDs are utilized by EGF treatment and their depletion through the inhibition of lipid synthesis or silencing of PLIN2 significantly attenuates proliferation. This novel mechanism of proliferative EGFR signaling leading to elevated LD density in colon cancer cells could potentially be therapeutically targeted for the treatment of tumor progression. - Highlights: • In colon cancer cells, EGFR activation leads to increases in LD density. • EGFR signaling includes PI3K/mTOR and PGE2 leading to lipid synthesis. • Increases in LDs are controlled by a negative regulatory loop with FOXO3/SIRT6. • EGFR mediated colon cancer cell proliferation depends on increased LD density.

  19. Epidermal growth factor receptor mediated proliferation depends on increased lipid droplet density regulated via a negative regulatory loop with FOXO3/Sirtuin6

    International Nuclear Information System (INIS)

    Penrose, Harrison; Heller, Sandra; Cable, Chloe; Makboul, Rania; Chadalawada, Gita; Chen, Ying; Crawford, Susan E.; Savkovic, Suzana D.

    2016-01-01

    The proliferation of colon cancer cells is mediated in part by epidermal growth factor receptor (EGFR) signaling and requires sustained levels of cellular energy to meet its high metabolic needs. Intracellular lipid droplets (LDs) are a source of energy used for various cellular functions and they are elevated in density in human cancer, yet their regulation and function are not well understood. Here, in human colon cancer cells, EGF stimulates increases in LD density, which depends on EGFR expression and activation as well as the individual cellular capacity for lipid synthesis. Increases in LDs are blockaded by inhibition of PI3K/mTOR and PGE2 synthesis, supporting their dependency on select upstream pathways. In colon cancer cells, silencing of the FOXO3 transcription factor leads to down regulation of SIRT6, a negative regulator of lipid synthesis, and consequent increases in the LD coat protein PLIN2, revealing that increases in LDs depend on loss of FOXO3/SIRT6. Moreover, EGF stimulates loss of FOXO3/SIRT6, which is blockaded by the inhibition of upstream pathways as well as lipid synthesis, revealing existence of a negative regulatory loop between LDs and FOXO3/SIRT6. Elevated LDs are utilized by EGF treatment and their depletion through the inhibition of lipid synthesis or silencing of PLIN2 significantly attenuates proliferation. This novel mechanism of proliferative EGFR signaling leading to elevated LD density in colon cancer cells could potentially be therapeutically targeted for the treatment of tumor progression. - Highlights: • In colon cancer cells, EGFR activation leads to increases in LD density. • EGFR signaling includes PI3K/mTOR and PGE2 leading to lipid synthesis. • Increases in LDs are controlled by a negative regulatory loop with FOXO3/SIRT6. • EGFR mediated colon cancer cell proliferation depends on increased LD density.

  20. Excited-state quantum phase transitions in systems with two degrees of freedom: Level density, level dynamics, thermal properties

    International Nuclear Information System (INIS)

    Stránský, Pavel; Macek, Michal; Cejnar, Pavel

    2014-01-01

    Quantum systems with a finite number of freedom degrees f develop robust singularities in the energy spectrum of excited states as the system’s size increases to infinity. We analyze the general form of these singularities for low f, particularly f=2, clarifying the relation to classical stationary points of the corresponding potential. Signatures in the smoothed energy dependence of the quantum state density and in the flow of energy levels with an arbitrary control parameter are described along with the relevant thermodynamical consequences. The general analysis is illustrated with specific examples of excited-state singularities accompanying the first-order quantum phase transition. -- Highlights: •ESQPTs found in infinite-size limit of systems with low numbers of freedom degrees f. •ESQPTs related to non-analytical evolutions of classical phase–space properties. •ESQPT signatures analyzed for general f, particularly f=2, extending known case f=1. •ESQPT signatures identified in smoothened density and flow of energy spectrum. •ESQPTs shown to induce a new type of thermodynamic anomalies

  1. Design of State-of-the-art Flow Cells for Energy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2018-01-31

    The worldwide energy demand is increasing every day and it necessitates rational and efficient usage of renewable energy. Undoubtedly, utilization of renewable energy can address various environmental challenges. However, all current renewable energy resources (wind, solar, and hydroelectric power) are intermittent and fluctuating in their nature that raises an important question of introducing effective energy storage solutions. Utilization of redox flow cells (RFCs) has recently been recognized as a viable technology for large-scale energy storage and, hence, is well suited for integrating renewable energy and balancing electricity grids. In brief, RFC is an electrochemical storage device where energy is stored in chemical bonds, similar to a battery, but with reactants external to the cell. The state-of-the-art in flow cell technology uses an aqueous acidic electrolyte and simple metal redox couples. Thus, there is an urgent call to develop efficient (high-energy density) and low-cost RFCs to meet the efflorescent energy storage demands. To address the first challenge of achieving high-energy density, we plan to design and further modify complexes composed of bifunctional multidentate ligands and specific metal centers, capable of storing as many electrons as possible. In order to address the second challenge of reducing cost of the RFCs, we plan to use iron (Fe) metal as it regularly occupies multiple oxidation states and is the second most abundant metal in the earth’s crust that makes it an ideal metal for improved energy densities, higher potentials, and numbers of electrons per molecule while maintaining potential cost competitiveness. Density functional theory calculations considering solvation effects will be performed to yield accurate predictions of redox potentials.

  2. Density-dependence as a size-independent regulatory mechanism

    NARCIS (Netherlands)

    De Vladar, H.P.

    2006-01-01

    The growth function of populations is central in biomathematics. The main dogma is the existence of density-dependence mechanisms, which can be modelled with distinct functional forms that depend on the size of the Population. One important class of regulatory functions is the theta-logistic, which

  3. Excited-state absorption in tetrapyridyl porphyrins: comparing real-time and quadratic-response time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, David N. [Department of Chemistry; Supercomputing Institute and Chemical Theory Center; University of Minnesota; Minneapolis; USA; Asher, Jason C. [Department of Chemistry; Supercomputing Institute and Chemical Theory Center; University of Minnesota; Minneapolis; USA; Fischer, Sean A. [William R. Wiley Environmental Molecular Sciences Laboratory; Pacific Northwest National Laboratory; P.O. Box 999; Richland; USA; Cramer, Christopher J. [Department of Chemistry; Supercomputing Institute and Chemical Theory Center; University of Minnesota; Minneapolis; USA; Govind, Niranjan [William R. Wiley Environmental Molecular Sciences Laboratory; Pacific Northwest National Laboratory; P.O. Box 999; Richland; USA

    2017-01-01

    Threemeso-substituted tetrapyridyl porphyrins (free base, Ni(ii), and Cu(ii)) were investigated for their optical limiting (OL) capabilities using real-time (RT-), linear-response (LR-), and quadratic-response (QR-) time-dependent density functional theory (TDDFT) methods.

  4. The relative importance of topography and RGD ligand density for endothelial cell adhesion.

    Directory of Open Access Journals (Sweden)

    Guillaume Le Saux

    Full Text Available The morphology and function of endothelial cells depends on the physical and chemical characteristics of the extracellular environment. Here, we designed silicon surfaces on which topographical features and surface densities of the integrin binding peptide arginine-glycine-aspartic acid (RGD could be independently controlled. We used these surfaces to investigate the relative importance of the surface chemistry of ligand presentation versus surface topography in endothelial cell adhesion. We compared cell adhesion, spreading and migration on surfaces with nano- to micro-scaled pyramids and average densities of 6×10(2-6×10(11 RGD/mm(2. We found that fewer cells adhered onto rough than flat surfaces and that the optimal average RGD density for cell adhesion was 6×10(5 RGD/mm(2 on flat surfaces and substrata with nano-scaled roughness. Only on surfaces with micro-scaled pyramids did the topography hinder cell migration and a lower average RGD density was optimal for adhesion. In contrast, cell spreading was greatest on surfaces with 6×10(8 RGD/mm(2 irrespectively of presence of feature and their size. In summary, our data suggest that the size of pyramids predominately control the number of endothelial cells that adhere to the substratum but the average RGD density governs the degree of cell spreading and length of focal adhesion within adherent cells. The data points towards a two-step model of cell adhesion: the initial contact of cells with a substratum may be guided by the topography while the engagement of cell surface receptors is predominately controlled by the surface chemistry.

  5. Widespread Dependence of Backup NHEJ on Growth State: Ramifications for the Use of DNA-PK Inhibitors

    International Nuclear Information System (INIS)

    Singh, Satyendra K.; Wu Wenqi; Zhang Lihua; Klammer, Holger; Wang Minli; Iliakis, George

    2011-01-01

    Purpose: The backup pathway of nonhomologous end joining (B-NHEJ) enables cells to process DNA double-strand breaks (DSBs) when the DNA-PK-dependent pathway of NHEJ (D-NHEJ) is compromised. Our previous results show marked reduction in the activity of B-NHEJ when LIG4 -/- mouse embryo fibroblasts (MEFs) cease to grow and enter a plateau phase. The dependence of B-NHEJ on growth state is substantially stronger than that of D-NHEJ and points to regulatory mechanisms or processing determinants that require elucidation. Because the different D-NHEJ mutants show phenotypes distinct in their details, it is necessary to characterize the dependence of their DSB repair capacity on growth state and to explore species-specific responses. Methods and Materials: DSB repair was measured in cells of different genetic background from various species using pulsed-field gel electrophoresis, or the formation of γ-H2AX foci, at different stages of growth. Results: Using pulsed-field gel electrophoresis, we report a marked reduction of B-NHEJ during the plateau phase of growth in KU and XRCC4, mouse or Chinese hamster, mutants. Notably, this reduction is only marginal in DNA-PKcs-deficient cells. However, reduced B-NHEJ is also observed in repair proficient, plateau-phase cells after treatment with DNA-PK inhibitors. The reduction of B-NHEJ activity in the plateau phase of growth does not derive from the reduced expression of participating proteins, is detectable by γ-H2AX foci analysis, and leads to enhanced cell killing. Conclusions: These results further document the marked dependence on growth state of an essential DSB repair pathway and show the general nature of the effect. Molecular characterization of the mechanism underlying this response will help to optimize the administration of DNA repair inhibitors as adjuvants in radiation therapy.

  6. Dependence of performance of Si nanowire solar cells on geometry of the nanowires.

    Science.gov (United States)

    Khan, Firoz; Baek, Seong-Ho; Kim, Jae Hyun

    2014-01-01

    The dependence of performance of silicon nanowires (SiNWs) solar cells on the growth condition of the SiNWs has been described. Metal-assisted electroless etching (MAE) technique has been used to grow SiNWs array. Different concentration of aqueous solution containing AgNO3 and HF for Ag deposition is used. The diameter and density of SiNWs are found to be dependent on concentration of solution used for Ag deposition. The diameter and density of SiNWs have been used to calculate the filling ratio of the SINWs arrays. The filling ratio is increased with increase in AgNO3 concentration, whereas it is decreased with increase in HF concentration. The minimum reflectance value achieved is ~1% for SiNWs of length of ~1.2 μ m in the wavelength range of 300-1000 nm. The performance and diode parameters strongly depend on the geometry of SiNWs. The maximum short circuit current density achieved is 35.6 mA/cm(2). The conversion efficiency of solar cell is 9.73% for SiNWs with length, diameter, and wire density of ~1.2 μ m, ~75 nm, and 90 μ m(-2), respectively.

  7. Accuracy of the calculations of the ionization-state densities in a steady-state plasma

    International Nuclear Information System (INIS)

    Salzmann, D.

    1980-01-01

    A quantitative definition is given to the accuracy of the computation of the partial densities of the ionization states in a steady-state plasma when there is an inaccuracy in the rate coefficients used in the rate equation. It is found that the partial density of the most abundant ion species is almost independent of the exact form of the rate coefficients, but large errors may occur for the rare species. The effect of the variation of the total ion density on the partial densities is also calculated. For low-ion densities the partial ionization-state densities grow proportionally to the change of the total density, but at high densities there is an alteration of the charge-state distribution as well

  8. Quasiparticle density of states, localization, and distributed disorder in the cuprate superconductors

    Science.gov (United States)

    Sulangi, Miguel Antonio; Zaanen, Jan

    2018-04-01

    We explore the effects of various kinds of random disorder on the quasiparticle density of states of two-dimensional d -wave superconductors using an exact real-space method, incorporating realistic details known about the cuprates. Random on-site energy and pointlike unitary impurity models are found to give rise to a vanishing DOS at the Fermi energy for narrow distributions and low concentrations, respectively, and lead to a finite, but suppressed, DOS at unrealistically large levels of disorder. Smooth disorder arising from impurities located away from the copper-oxide planes meanwhile gives rise to a finite DOS at realistic impurity concentrations. For the case of smooth disorder whose average potential is zero, a resonance is found at zero energy for the quasiparticle DOS at large impurity concentrations. We discuss the implications of these results on the computed low-temperature specific heat, the behavior of which we find is strongly affected by the amount of disorder present in the system. We also compute the localization length as a function of disorder strength for various types of disorder and find that intermediate- and high-energy states are quasiextended for low disorder, and that states near the Fermi energy are strongly localized and have a localization length that exhibits an unusual dependence on the amount of disorder. We comment on the origin of disorder in the cuprates and provide constraints on these based on known results from scanning tunneling spectroscopy and specific heat experiments.

  9. Density-dependent feedbacks can mask environmental drivers of populations

    DEFF Research Database (Denmark)

    Dahlgren, Johan Petter

    I present some results from studies identifying environmental drivers of vital rates and population dynamics when controlling for intraspecific density statistically or experimentally, show that density dependence can be strong even in populations of slow-growing species in stressful habitats, an...

  10. Oxygen-dependent sensitization of irradiated cells

    International Nuclear Information System (INIS)

    Ewing, D.; Powers, E.L.

    1979-01-01

    Attention is focused primarily on O 2 effects in three biological systems, all tested in suspension: bacterial spores, vegetative bacterial cells, and mammalian cells. Information from these systems shows that O 2 has more than one process through which it can act. Studies with bacterial spore suspensions provide clear evidence that multiple components to oxygen-dependent radiation sensitization exist. Studies with mammalian cell suspensions also show that at least two oxygen-dependent sensitization processes can be distinguished. Similar studies with vegetative bacteria in suspension have not resolved oxic sensitization into components. The roles of water-derived radicals in radiation sensitivity and, specifically, in sensitization by O 2 were examined. OH radicals are clearly implicated in damage in all three biological test systems. However, the specific roles proposed for OH radicals are different in these organisms. In bacterial spores, OH radical removal in itself does not protect in anoxia or in high concentrations of O 2 . OH radical removal over a limited intermediate range of O 2 concentrations will, however, protect. OH radical scavenging probably results in the formation of the actual protector. In bacteria, the supposition is that OH radical removal will protect both in anoxia and in the presence of O 2 . OH radicals probably react with a cellular target molecule and leave a radicalsite; this is the site which can then react with O 2 to cause damage; DNA is the likely cellular target. In mammalian cells, a reaction scheme, similar to that proposed for bacteria, has been suggested for O 2 -dependent sensitization

  11. Natural killer cells facilitate PRAME-specific T-cell reactivity against neuroblastoma

    Science.gov (United States)

    Spel, Lotte; Boelens, Jaap-Jan; van der Steen, Dirk M.; Blokland, Nina J.G.; van Noesel, Max M.; Molenaar, Jan J.; Heemskerk, Mirjam H.M.

    2015-01-01

    Neuroblastoma is the most common solid tumor in children with an estimated 5-year progression free survival of 20–40% in stage 4 disease. Neuroblastoma actively avoids recognition by natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). Although immunotherapy has gained traction for neuroblastoma treatment, these immune escape mechanisms restrain clinical results. Therefore, we aimed to improve neuroblastoma immunogenicity to further the development of antigen-specific immunotherapy against neuroblastoma. We found that neuroblastoma cells significantly increase surface expression of MHC I upon exposure to active NK cells which thereby readily sensitize neuroblastoma cells for recognition by CTLs. We show that oncoprotein PRAME serves as an immunodominant antigen for neuroblastoma as NK-modulated neuroblastoma cells are recognized by PRAMESLLQHLIGL/A2-specific CTL clones. Furthermore, NK cells induce MHC I upregulation in neuroblastoma through contact-dependent secretion of IFNγ. Our results demonstrate remarkable plasticity in the peptide/MHC I surface expression of neuroblastoma cells, which is reversed when neuroblastoma cells experience innate immune attack by sensitized NK cells. These findings support the exploration of NK cells as adjuvant therapy to enforce neuroblastoma-specific CTL responses. PMID:26452036

  12. Self-interaction corrected density functional calculations of molecular Rydberg states

    International Nuclear Information System (INIS)

    Gudmundsdóttir, Hildur; Zhang, Yao; Weber, Peter M.; Jónsson, Hannes

    2013-01-01

    A method is presented for calculating the wave function and energy of Rydberg excited states of molecules. A good estimate of the Rydberg state orbital is obtained using ground state density functional theory including Perdew-Zunger self-interaction correction and an optimized effective potential. The total energy of the excited molecule is obtained using the Delta Self-Consistent Field method where an electron is removed from the highest occupied orbital and placed in the Rydberg orbital. Results are presented for the first few Rydberg states of NH 3 , H 2 O, H 2 CO, C 2 H 4 , and N(CH 3 ) 3 . The mean absolute error in the energy of the 33 molecular Rydberg states presented here is 0.18 eV. The orbitals are represented on a real space grid, avoiding the dependence on diffuse atomic basis sets. As in standard density functional theory calculations, the computational effort scales as NM 2 where N is the number of orbitals and M is the number of grid points included in the calculation. Due to the slow scaling of the computational effort with system size and the high level of parallelism in the real space grid approach, the method presented here makes it possible to estimate Rydberg electron binding energy in large molecules

  13. Density-dependent cladogenesis in birds.

    Directory of Open Access Journals (Sweden)

    Albert B Phillimore

    2008-03-01

    Full Text Available A characteristic signature of adaptive radiation is a slowing of the rate of speciation toward the present. On the basis of molecular phylogenies, studies of single clades have frequently found evidence for a slowdown in diversification rate and have interpreted this as evidence for density dependent speciation. However, we demonstrated via simulation that large clades are expected to show stronger slowdowns than small clades, even if the probability of speciation and extinction remains constant through time. This is a consequence of exponential growth: clades, which, by chance, diversify at above the average rate early in their history, will tend to be large. They will also tend to regress back to the average diversification rate later on, and therefore show a slowdown. We conducted a meta-analysis of the distribution of speciation events through time, focusing on sequence-based phylogenies for 45 clades of birds. Thirteen of the 23 clades (57% that include more than 20 species show significant slowdowns. The high frequency of slowdowns observed in large clades is even more extreme than expected under a purely stochastic constant-rate model, but is consistent with the adaptive radiation model. Taken together, our data strongly support a model of density-dependent speciation in birds, whereby speciation slows as ecological opportunities and geographical space place limits on clade growth.

  14. Effects of Density-Dependent Bag Constant and Strange Star Rotation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Qiao-Er; GUO Hua

    2003-01-01

    With the emphasis on the effects of the density-dependent bag constant and the rotation of strange star the limiting mass of strange star is calculated. The obtained results show that the limiting mass and the corresponding radius of strange star increase as the rotation frequency increases, and tend to be lowered when the density-dependent bag constant is considered.

  15. FasL and FADD delivery by a glioma-specific and cell cycle-dependent HSV-1 amplicon virus enhanced apoptosis in primary human brain tumors

    Directory of Open Access Journals (Sweden)

    Lam Paula Y

    2010-10-01

    Full Text Available Abstract Background Glioblastoma multiforme is the most malignant cancer of the brain and is notoriously difficult to treat due to the highly proliferative and infiltrative nature of the cells. Herein, we explored the combination treatment of pre-established human glioma xenograft using multiple therapeutic genes whereby the gene expression is regulated by both cell-type and cell cycle-dependent transcriptional regulatory mechanism conferred by recombinant HSV-1 amplicon vectors. Results We demonstrated for the first time that Ki67-positive proliferating primary human glioma cells cultured from biopsy samples were effectively induced into cell death by the dual-specific function of the pG8-FasL amplicon vectors. These vectors were relatively stable and exhibited minimal cytotoxicity in vivo. Intracranial implantation of pre-transduced glioma cells resulted in better survival outcome when compared with viral vectors inoculated one week post-implantation of tumor cells, indicating that therapeutic efficacy is dependent on the viral spread and mode of viral vectors administration. We further showed that pG8-FasL amplicon vectors are functional in the presence of commonly used treatment regimens for human brain cancer. In fact, the combined therapies of pG8-FasL and pG8-FADD in the presence of temozolomide significantly improved the survival of mice bearing intracranial high-grade gliomas. Conclusion Taken together, our results showed that the glioma-specific and cell cycle-dependent HSV-1 amplicon vector is potentially useful as an adjuvant therapy to complement the current gene therapy strategy for gliomas.

  16. Deriving the coronal hole electron temperature: electron density dependent ionization / recombination considerations

    International Nuclear Information System (INIS)

    Doyle, John Gerard; Perez-Suarez, David; Singh, Avninda; Chapman, Steven; Bryans, Paul; Summers, Hugh; Savin, Daniel Wolf

    2010-01-01

    Comparison of appropriate theoretically derived line ratios with observational data can yield estimates of a plasma's physical parameters, such as electron density or temperature. The usual practice in the calculation of the line ratio is the assumption of excitation by electrons/protons followed by radiative decay. Furthermore, it is normal to use the so-called coronal approximation, i.e. one only considers ionization and recombination to and from the ground-state. A more accurate treatment is to include ionization/recombination to and from metastable levels. Here, we apply this to two lines from adjacent ionization stages, Mg IX 368 A and Mg X 625 A, which has been shown to be a very useful temperature diagnostic. At densities typical of coronal hole conditions, the difference between the electron temperature derived assuming the zero density limit compared with the electron density dependent ionization/recombination is small. This, however, is not the case for flares where the electron density is orders of magnitude larger. The derived temperature for the coronal hole at solar maximum is around 1.04 MK compared to just below 0.82 MK at solar minimum.

  17. Method of observation of low density interface states by means of X-ray photoelectron spectroscopy under bias and passivation by cyanide ions

    International Nuclear Information System (INIS)

    Kobayashi, H.; Sakurai, T.; Yamashita, Y.; Kubota, T.; Maida, O.; Takahashi, M.

    2006-01-01

    X-ray photoelectron spectroscopy (XPS) measurements under bias can observe low density interface states for metal-oxide-semiconductor (MOS) diodes with low densities. This method can give energy distribution of interface states for ultrathin insulating layers for which electrical measurements cannot be performed due to a high density leakage current. During the XPS measurements, a bias voltage is applied to the rear semiconductor surface with respect to the ∼3 nm-thick front platinum layer connected to the ground, and the bias voltage changes the occupation of interface states. Charges accumulated in the interface states shift semiconductor core levels at the interface, and thus the analysis of the bias-induced shifts of the semiconductor core levels measured as a function of the bias voltage gives energy distribution of interface states. In the case of Si-based MOS diodes, the energy distribution and density of interface states strongly depend on the atomic density of silicon dioxide (SiO 2 ) layers and the interfacial roughness, respectively. All the observed interface state spectra possess peaked-structures, indicating that they are due to defect states. An interface state peak near the Si midgap is attributable to isolated Si dangling bonds at the interface, while those above and below the midgap to Si dangling bonds interacting weakly with Si or oxygen atoms in the SiO 2 layers. A method of the elimination of interface states and defect states in Si using cyanide solutions has been developed. The cyanide method simply involves the immersion of Si in KCN solutions. Due to the high Si-CN bond energy of ∼4.5 eV, the bonds are not ruptured at 800 deg. C and upon irradiation. The cyanide treatment results in the improvement of the electrical characteristics of MOS diodes and solar cells

  18. A study on specific heat capacities of Li-ion cell components and their influence on thermal management

    Science.gov (United States)

    Loges, André; Herberger, Sabrina; Seegert, Philipp; Wetzel, Thomas

    2016-12-01

    Thermal models of Li-ion cells on various geometrical scales and with various complexity have been developed in the past to account for the temperature dependent behaviour of Li-ion cells. These models require accurate data on thermal material properties to offer reliable validation and interpretation of the results. In this context a thorough study on the specific heat capacities of Li-ion cells starting from raw materials and electrode coatings to representative unit cells of jelly rolls/electrode stacks with lumped values was conducted. The specific heat capacity is reported as a function of temperature and state of charge (SOC). Seven Li-ion cells from different manufactures with different cell chemistry, application and design were considered and generally applicable correlations were developed. A 2D thermal model of an automotive Li-ion cell for plug-in hybrid electric vehicle (PHEV) application illustrates the influence of specific heat capacity on the effectivity of cooling concepts and the temperature development of Li-ion cells.

  19. Cuticular antifungals in spiders: density- and condition dependence.

    Directory of Open Access Journals (Sweden)

    Daniel González-Tokman

    Full Text Available Animals living in groups face a high risk of disease contagion. In many arthropod species, cuticular antimicrobials constitute the first protective barrier that prevents infections. Here we report that group-living spiders produce cuticular chemicals which inhibit fungal growth. Given that cuticular antifungals may be costly to produce, we explored whether they can be modulated according to the risk of contagion (i.e. under high densities. For this purpose, we quantified cuticular antifungal activity in the subsocial crab spider Diaea ergandros in both natural nests and experimentally manipulated nests of varying density. We quantified the body-condition of spiders to test whether antifungal activity is condition dependent, as well as the effect of spider density on body-condition. We predicted cuticular antifungal activity to increase and body-condition to decrease with high spider densities, and that antifungal activity would be inversely related to body-condition. Contrary to our predictions, antifungal activity was neither density- nor condition-dependent. However, body-condition decreased with density in natural nests, but increased in experimental nests. We suggest that pathogen pressure is so important in nature that it maintains high levels of cuticular antifungal activity in spiders, impacting negatively on individual energetic condition. Future studies should identify the chemical structure of the isolated antifungal compounds in order to understand the physiological basis of a trade-off between disease prevention and energetic condition caused by group living, and its consequences in the evolution of sociality in spiders.

  20. Cuticular antifungals in spiders: density- and condition dependence.

    Science.gov (United States)

    González-Tokman, Daniel; Ruch, Jasmin; Pulpitel, Tamara; Ponton, Fleur

    2014-01-01

    Animals living in groups face a high risk of disease contagion. In many arthropod species, cuticular antimicrobials constitute the first protective barrier that prevents infections. Here we report that group-living spiders produce cuticular chemicals which inhibit fungal growth. Given that cuticular antifungals may be costly to produce, we explored whether they can be modulated according to the risk of contagion (i.e. under high densities). For this purpose, we quantified cuticular antifungal activity in the subsocial crab spider Diaea ergandros in both natural nests and experimentally manipulated nests of varying density. We quantified the body-condition of spiders to test whether antifungal activity is condition dependent, as well as the effect of spider density on body-condition. We predicted cuticular antifungal activity to increase and body-condition to decrease with high spider densities, and that antifungal activity would be inversely related to body-condition. Contrary to our predictions, antifungal activity was neither density- nor condition-dependent. However, body-condition decreased with density in natural nests, but increased in experimental nests. We suggest that pathogen pressure is so important in nature that it maintains high levels of cuticular antifungal activity in spiders, impacting negatively on individual energetic condition. Future studies should identify the chemical structure of the isolated antifungal compounds in order to understand the physiological basis of a trade-off between disease prevention and energetic condition caused by group living, and its consequences in the evolution of sociality in spiders.

  1. Quasi-one-dimensional density of states in a single quantum ring.

    Science.gov (United States)

    Kim, Heedae; Lee, Woojin; Park, Seongho; Kyhm, Kwangseuk; Je, Koochul; Taylor, Robert A; Nogues, Gilles; Dang, Le Si; Song, Jin Dong

    2017-01-05

    Generally confinement size is considered to determine the dimensionality of nanostructures. While the exciton Bohr radius is used as a criterion to define either weak or strong confinement in optical experiments, the binding energy of confined excitons is difficult to measure experimentally. One alternative is to use the temperature dependence of the radiative recombination time, which has been employed previously in quantum wells and quantum wires. A one-dimensional loop structure is often assumed to model quantum rings, but this approximation ceases to be valid when the rim width becomes comparable to the ring radius. We have evaluated the density of states in a single quantum ring by measuring the temperature dependence of the radiative recombination of excitons, where the photoluminescence decay time as a function of temperature was calibrated by using the low temperature integrated intensity and linewidth. We conclude that the quasi-continuous finely-spaced levels arising from the rotation energy give rise to a quasi-one-dimensional density of states, as long as the confined exciton is allowed to rotate around the opening of the anisotropic ring structure, which has a finite rim width.

  2. Time-dependent cell disintegration kinetics in lung tumors after irradiation

    International Nuclear Information System (INIS)

    Chvetsov, Alexei V; Palta, Jatinder J; Nagata, Yasushi

    2008-01-01

    We study the time-dependent disintegration kinetics of tumor cells that did not survive radiotherapy treatment. To evaluate the cell disintegration rate after irradiation, we studied the volume changes of solitary lung tumors after stereotactic radiotherapy. The analysis is performed using two approximations: (1) tumor volume is a linear function of the total cell number in the tumor and (2) the cell disintegration rate is governed by the exponential decay with constant risk, which is defined by the initial cell number and a half-life T 1/2 . The half-life T 1/2 is determined using the least-squares fit to the clinical data on lung tumor size variation with time after stereotactic radiotherapy. We show that the tumor volume variation after stereotactic radiotherapy of solitary lung tumors can be approximated by an exponential function. A small constant component in the volume variation does not change with time; however, this component may be the residual irregular density due to radiation fibrosis and was, therefore, subtracted from the total volume variation in our computations. Using computerized fitting of the exponent function to the clinical data for selected patients, we have determined that the average half-life T 1/2 of cell disintegration is 28.2 days for squamous cell carcinoma and 72.4 days for adenocarcinoma. This model is needed for simulating the tumor volume variation during radiotherapy, which may be important for time-dependent treatment planning of proton therapy that is sensitive to density variations

  3. Experimental evidence for density dependence of reproduction in great tits

    NARCIS (Netherlands)

    Both, C.

    1998-01-01

    1. Density dependence of avian reproduction has often been analysed using correlations between annual mean reproductive output and population density. Experiments are necessary to prove that density is the cause of the observed patterns, but so far, three out of four experimental studies do not

  4. Experimental evidence that density dependence strongly influences plant invasions through fragmented landscapes.

    Science.gov (United States)

    Williams, Jennifer L; Levine, Jonathan M

    2018-04-01

    Populations of range expanding species encounter patches of both favorable and unfavorable habitat as they spread across landscapes. Theory shows that increasing patchiness slows the spread of populations modeled with continuously varying population density when dispersal is not influence by the environment or individual behavior. However, as is found in uniformly favorable landscapes, spread remains driven by fecundity and dispersal from low density individuals at the invasion front. In contrast, when modeled populations are composed of discrete individuals, patchiness causes populations to build up to high density before dispersing past unsuitable habitat, introducing an important influence of density dependence on spread velocity. To test the hypothesized interaction between habitat patchiness and density dependence, we simultaneously manipulated these factors in a greenhouse system of annual plants spreading through replicated experimental landscapes. We found that increasing the size of gaps and amplifying the strength of density dependence both slowed spread velocity, but contrary to predictions, the effect of amplified density dependence was similar across all landscape types. Our results demonstrate that the discrete nature of individuals in spreading populations has a strong influence on how both landscape patchiness and density dependence influence spread through demographic and dispersal stochasticity. Both finiteness and landscape structure should be critical components to theoretical predictions of future spread for range expanding native species or invasive species colonizing new habitat. © 2018 by the Ecological Society of America.

  5. Experimental evidence for density dependence of reproduction in great tits

    NARCIS (Netherlands)

    Both, Christiaan

    1998-01-01

    1.  Density dependence of avian reproduction has often been analysed using correlations between annual mean reproductive output and population density. Experiments are necessary to prove that density is the cause of the observed patterns, but so far, three out of four experimental studies do not

  6. Effect of neutron irradiation on the density of low-energy excitations in vitreous silica

    International Nuclear Information System (INIS)

    Smith, T.L.

    1979-01-01

    Systematic low-temperature measurements of the thermal conductivity, specific heat, dielectric constant, and temperature-dependent ultrasound velocity were made on a single piece of vitreous silica. These measurements were repeated after fast neutron irradiation of the material. It was found that the irradiation produced changes of the same relative magnitude in the low-temperature excess specific heat C/sub ex/, the thermal conductivity kappa, and the anomalous temperature dependence of the ultrasound velocity Δv/v. A corresponding change in the temperature dependent dielectric constant was not observed. It is therefore likely that kappa and Δv/v are determined by the same localized excitations responsible for C/sub ex/, but the temperature dependence of the dielectric constant may have a different, though possibly related, origin. A consistent account for the measured C/sub ex/, kappa, and Δv/v of unirradiated silica is given by the tunneling-state model with a single, energy-dependent density of states. Changes in these three properties due to irradiation can be explained by altering only the density of tunneling states incorporated in the model

  7. Time-dependent occupation numbers in reduced-density-matrix-functional theory: Application to an interacting Landau-Zener model

    International Nuclear Information System (INIS)

    Requist, Ryan; Pankratov, Oleg

    2011-01-01

    We prove that if the two-body terms in the equation of motion for the one-body reduced density matrix are approximated by ground-state functionals, the eigenvalues of the one-body reduced density matrix (occupation numbers) remain constant in time. This deficiency is related to the inability of such an approximation to account for relative phases in the two-body reduced density matrix. We derive an exact differential equation giving the functional dependence of these phases in an interacting Landau-Zener model and study their behavior in short- and long-time regimes. The phases undergo resonances whenever the occupation numbers approach the boundaries of the interval [0,1]. In the long-time regime, the occupation numbers display correlation-induced oscillations and the memory dependence of the functionals assumes a simple form.

  8. Antigen-Specific Th17 Cells Are Primed by Distinct and Complementary Dendritic Cell Subsets in Oropharyngeal Candidiasis.

    Directory of Open Access Journals (Sweden)

    Kerstin Trautwein-Weidner

    2015-10-01

    Full Text Available Candida spp. can cause severe and chronic mucocutaneous and systemic infections in immunocompromised individuals. Protection from mucocutaneous candidiasis depends on T helper cells, in particular those secreting IL-17. The events regulating T cell activation and differentiation toward effector fates in response to fungal invasion in different tissues are poorly understood. Here we generated a Candida-specific TCR transgenic mouse reactive to a novel endogenous antigen that is conserved in multiple distant species of Candida, including the clinically highly relevant C. albicans and C. glabrata. Using TCR transgenic T cells in combination with an experimental model of oropharyngeal candidiasis (OPC we investigated antigen presentation and Th17 priming by different subsets of dendritic cells (DCs present in the infected oral mucosa. Candida-derived endogenous antigen accesses the draining lymph nodes and is directly presented by migratory DCs. Tissue-resident Flt3L-dependent DCs and CCR2-dependent monocyte-derived DCs collaborate in antigen presentation and T cell priming during OPC. In contrast, Langerhans cells, which are also present in the oral mucosa and have been shown to prime Th17 cells in the skin, are not required for induction of the Candida-specific T cell response upon oral challenge. This highlights the functional compartmentalization of specific DC subsets in different tissues. These data provide important new insights to our understanding of tissue-specific antifungal immunity.

  9. Cell density and actomyosin contractility control the organization of migrating collectives within an epithelium

    Science.gov (United States)

    Loza, Andrew J.; Koride, Sarita; Schimizzi, Gregory V.; Li, Bo; Sun, Sean X.; Longmore, Gregory D.

    2016-01-01

    The mechanisms underlying collective migration are important for understanding development, wound healing, and tumor invasion. Here we focus on cell density to determine its role in collective migration. Our findings show that increasing cell density, as might be seen in cancer, transforms groups from broad collectives to small, narrow streams. Conversely, diminishing cell density, as might occur at a wound front, leads to large, broad collectives with a distinct leader–follower structure. Simulations identify force-sensitive contractility as a mediator of how density affects collectives, and guided by this prediction, we find that the baseline state of contractility can enhance or reduce organization. Finally, we test predictions from these data in an in vivo epithelium by using genetic manipulations to drive collective motion between predicted migratory phases. This work demonstrates how commonly altered cellular properties can prime groups of cells to adopt migration patterns that may be harnessed in health or exploited in disease. PMID:27605707

  10. CHANGES OF BUOYANT DENSITY DURING THE S-PHASE OF THE CELL-CYCLE - DIRECT EVIDENCE DEMONSTRATED IN ACUTE MYELOID-LEUKEMIA BY FLOW-CYTOMETRIC

    NARCIS (Netherlands)

    DAENEN, S; HUIGES, W; MODDERMAN, E; HALIE, MR

    Studies with synchronized or exponentially growing bacteria and mammalian cell lines are not able to demonstrate small changes in buoyant density during the cell cycle. Flowcytometric analysis of density separated acute myeloid leukemia cells, a system not dependent on time-related variables, shows

  11. Modes of competition: adding and removing brown trout in the wild to understand the mechanisms of density-dependence.

    Directory of Open Access Journals (Sweden)

    Rasmus Kaspersson

    Full Text Available While the prevalence of density-dependence is well-established in population ecology, few field studies have investigated its underlying mechanisms and their relative population-level importance. Here, we address these issues, and more specifically, how differences in body-size influence population regulation. For this purpose, two experiments were performed in a small coastal stream on the Swedish west coast, using juvenile brown trout (Salmo trutta as a study species. We manipulated densities of large and small individuals, and observed effects on survival, migration, condition and individual growth rate in a target group of intermediate-sized individuals. The generality of the response was investigated by reducing population densities below and increasing above the natural levels (removing and adding large and small individuals. Reducing the density (relaxing the intensity of competition had no influence on the response variables, suggesting that stream productivity was not a limiting factor at natural population density. Addition of large individuals resulted in a negative density-dependent response, while no effect was detected when adding small individuals or when maintaining the natural population structure. We found that the density-dependent response was revealed as reduced growth rate rather than increased mortality and movement, an effect that may arise from exclusion to suboptimal habitats or increased stress levels among inferior individuals. Our findings confirm the notion of interference competition as the primary mode of competition in juvenile salmonids, and also show that the feedback-mechanisms of density-dependence are primarily acting when increasing densities above their natural levels.

  12. CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, accumulates at the postsynaptic density in an activity-dependent manner

    International Nuclear Information System (INIS)

    Dosemeci, Ayse; Thein, Soe; Yang, Yijung; Reese, Thomas S.; Tao-Cheng, Jung-Hwa

    2013-01-01

    Highlights: ► CYLD is a deubiquitinase specific for lysine63-linked polyubiquitins. ► Presence of CYLD in PSDs is established by biochemistry and immunoEM. ► CYLD accumulates on PSDs upon depolarization of neurons. ► Accumulation of CYLD at PSDs may regulate trafficking/degradation of synaptic proteins. -- Abstract: Polyubiquitin chains on proteins flag them for distinct fates depending on the type of polyubiquitin linkage. While lysine48-linked polyubiquitination directs proteins to proteasomal degradation, lysine63-linked polyubiquitination promotes different protein trafficking and is involved in autophagy. Here we show that postsynaptic density (PSD) fractions from adult rat brain contain deubiquitinase activity that targets both lysine48 and lysine63-linked polyubiquitins. Comparison of PSD fractions with parent subcellular fractions by Western immunoblotting reveals that CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, is highly enriched in the PSD fraction. Electron microscopic examination of hippocampal neurons in culture under basal conditions shows immunogold label for CYLD at the PSD complex in approximately one in four synapses. Following depolarization by exposure to high K+, the proportion of CYLD-labeled PSDs as well as the labeling intensity of CYLD at the PSD increased by more than eighty percent, indicating that neuronal activity promotes accumulation of CYLD at the PSD. An increase in postsynaptic CYLD following activity would promote removal of lysine63-polyubiquitins from PSD proteins and thus could regulate their trafficking and prevent their autophagic degradation.

  13. Charge-Transfer Dynamics in the Lowest Excited State of a Pentacene–Fullerene Complex: Implications for Organic Solar Cells

    KAUST Repository

    Joseph, Saju

    2017-10-02

    We characterize the dynamic nature of the lowest excited state in a pentacene/C60 complex on the femtosecond time scale, via a combination of ab initio molecular dynamics and time-dependent density functional theory. We analyze the correlations between the molecular vibrations of the complex and the oscillations in the electron-transfer character of its lowest excited state, which point to vibration-induced coherences between the (pentacene-based) local-excitation (LE) state and the complex charge-transfer (CT) state. We discuss the implications of our results on this model system for the exciton-dissociation process in organic solar cells.

  14. Dependence of Performance of Si Nanowire Solar Cells on Geometry of the Nanowires

    Directory of Open Access Journals (Sweden)

    Firoz Khan

    2014-01-01

    Full Text Available The dependence of performance of silicon nanowires (SiNWs solar cells on the growth condition of the SiNWs has been described. Metal-assisted electroless etching (MAE technique has been used to grow SiNWs array. Different concentration of aqueous solution containing AgNO3 and HF for Ag deposition is used. The diameter and density of SiNWs are found to be dependent on concentration of solution used for Ag deposition. The diameter and density of SiNWs have been used to calculate the filling ratio of the SINWs arrays. The filling ratio is increased with increase in AgNO3 concentration, whereas it is decreased with increase in HF concentration. The minimum reflectance value achieved is ~1% for SiNWs of length of ~1.2 μm in the wavelength range of 300–1000 nm. The performance and diode parameters strongly depend on the geometry of SiNWs. The maximum short circuit current density achieved is 35.6 mA/cm2. The conversion efficiency of solar cell is 9.73% for SiNWs with length, diameter, and wire density of ~1.2 μm, ~75 nm, and 90 μm−2, respectively.

  15. dc Resistivity of Quantum Critical, Charge Density Wave States from Gauge-Gravity Duality.

    Science.gov (United States)

    Amoretti, Andrea; Areán, Daniel; Goutéraux, Blaise; Musso, Daniele

    2018-04-27

    In contrast to metals with weak disorder, the resistivity of weakly pinned charge density waves (CDWs) is not controlled by irrelevant processes relaxing momentum. Instead, the leading contribution is governed by incoherent, diffusive processes which do not drag momentum and can be evaluated in the clean limit. We compute analytically the dc resistivity for a family of holographic charge density wave quantum critical phases and discuss its temperature scaling. Depending on the critical exponents, the ground state can be conducting or insulating. We connect our results to dc electrical transport in underdoped cuprate high T_{c} superconductors. We conclude by speculating on the possible relevance of unstable, semilocally critical CDW states to the strange metallic region.

  16. dc Resistivity of Quantum Critical, Charge Density Wave States from Gauge-Gravity Duality

    Science.gov (United States)

    Amoretti, Andrea; Areán, Daniel; Goutéraux, Blaise; Musso, Daniele

    2018-04-01

    In contrast to metals with weak disorder, the resistivity of weakly pinned charge density waves (CDWs) is not controlled by irrelevant processes relaxing momentum. Instead, the leading contribution is governed by incoherent, diffusive processes which do not drag momentum and can be evaluated in the clean limit. We compute analytically the dc resistivity for a family of holographic charge density wave quantum critical phases and discuss its temperature scaling. Depending on the critical exponents, the ground state can be conducting or insulating. We connect our results to dc electrical transport in underdoped cuprate high Tc superconductors. We conclude by speculating on the possible relevance of unstable, semilocally critical CDW states to the strange metallic region.

  17. Excitation energy and angular momentum dependence of the nuclear level densities

    International Nuclear Information System (INIS)

    Razavi, R.; Kakavand, T.; Behkami, A. N.

    2007-01-01

    We have investigated the excitation energy (E) dependence of nuclear level density for Bethe formula and constant temperature model. The level density parameter aa nd the back shifted energy from the Bethe formula are obtained by fitting the complete level schemes. Also the level density parameters from the constant temperature model have been determined for several nuclei. we have shown that the microscopic theory provides more precise information on the nuclear level densities. On the other hand, the spin cut-off parameter and effective moment of inertia are determined by studying of the angular momentum (J) dependence of the nuclear level density, and effective moment of inertia is compared with rigid body value.

  18. Slc3a2 Mediates Branched-Chain Amino-Acid-Dependent Maintenance of Regulatory T Cells

    Directory of Open Access Journals (Sweden)

    Kayo Ikeda

    2017-11-01

    Full Text Available Summary: Foxp3+ regulatory T (Treg cells, which suppress immune responses, are highly proliferative in vivo. However, it remains unclear how the active replication of Treg cells is maintained in vivo. Here, we show that branched-chain amino acids (BCAAs, including isoleucine, are required for maintenance of the proliferative state of Treg cells via the amino acid transporter Slc3a2-dependent metabolic reprogramming. Mice fed BCAA-reduced diets showed decreased numbers of Foxp3+ Treg cells with defective in vivo proliferative capacity. Mice lacking Slc3a2 specifically in Foxp3+ Treg cells showed impaired in vivo replication and decreased numbers of Treg cells. Slc3a2-deficient Treg cells showed impaired isoleucine-induced activation of the mTORC1 pathway and an altered metabolic state. Slc3a2 mutant mice did not show an isoleucine-induced increase of Treg cells in vivo and exhibited multi-organ inflammation. Taken together, these findings demonstrate that BCAA controls Treg cell maintenance via Slc3a2-dependent metabolic regulation. : Treg cells regulate excess immune responses and are highly proliferative in vivo. Ikeda et al. find that branched-chain amino acids (BCAAs are essentially required to maintain expansion and the suppressive capacity of Treg cells via Slc3a2 and mTORC1. Keywords: Treg cells, amino acids, immunometabolism, immune regulation, transporter

  19. Cell state switching factors and dynamical patterning modules ...

    Indian Academy of Sciences (India)

    Prakash

    segmented, differentiated and additional complex structures, with minimal evolution ...... (b, c) Hematoxylin and Oil-red (lipid specific) staining of low density cell culture grown ..... description to elaborated structural and functional classification;.

  20. Probing topological relations between high-density and low-density regions of 2MASS with hexagon cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yongfeng [American Physical Society, San Diego, CA (United States); Xiao, Weike, E-mail: yongfeng.wu@maine.edu [Department of Astronautics Engineering, Harbin Institute of Technology, P.O. Box 345, Heilongjiang Province 150001 (China)

    2014-02-01

    We introduced a new two-dimensional (2D) hexagon technique for probing the topological structure of the universe in which we mapped regions of the sky with high and low galaxy densities onto a 2D lattice of hexagonal unit cells. We defined filled cells as corresponding to high-density regions and empty cells as corresponding to low-density regions. The numbers of filled cells and empty cells were kept the same by controlling the size of the cells. By analyzing the six sides of each hexagon, we could obtain and compare the statistical topological properties of high-density and low-density regions of the universe in order to have a better understanding of the evolution of the universe. We applied this hexagonal method to Two Micron All Sky Survey data and discovered significant topological differences between the high-density and low-density regions. Both regions had significant (>5σ) topological shifts from both the binomial distribution and the random distribution.

  1. Time-dependent reduced density matrix functional theory applied to laser-driven, correlated two-electron dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brics, Martins; Kapoor, Varun; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)

    2013-07-01

    Time-dependent density functional theory (TDDFT) with known and practicable exchange-correlation potentials does not capture highly correlated electron dynamics such as single-photon double ionization, autoionization, or nonsequential ionization. Time-dependent reduced density matrix functional theory (TDRDMFT) may remedy these problems. The key ingredients in TDRDMFT are the natural orbitals (NOs), i.e., the eigenfunctions of the one-body reduced density matrix (1-RDM), and the occupation numbers (OCs), i.e., the respective eigenvalues. The two-body reduced density matrix (2-RDM) is then expanded in NOs, and equations of motion for the NOs can be derived. If the expansion coefficients of the 2-RDM were known exactly, the problem at hand would be solved. In practice, approximations have to be made. We study the prospects of TDRDMFT following a top-down approach. We solve the exact two-electron time-dependent Schroedinger equation for a model Helium atom in intense laser fields in order to study highly correlated phenomena such as the population of autoionizing states or single-photon double ionization. From the exact wave function we calculate the exact NOs, OCs, the exact expansion coefficients of the 2-RDM, and the exact potentials in the equations of motion. In that way we can identify how many NOs and which level of approximations are necessary to capture such phenomena.

  2. Model dependence of isospin sensitive observables at high densities

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wen-Mei [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); School of Science, Huzhou Teachers College, Huzhou 313000 (China); Yong, Gao-Chan, E-mail: yonggaochan@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, Yongjia [School of Science, Huzhou Teachers College, Huzhou 313000 (China); School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Li, Qingfeng [School of Science, Huzhou Teachers College, Huzhou 313000 (China); Zhang, Hongfei [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zuo, Wei [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2013-10-07

    Within two different frameworks of isospin-dependent transport model, i.e., Boltzmann–Uehling–Uhlenbeck (IBUU04) and Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport models, sensitive probes of nuclear symmetry energy are simulated and compared. It is shown that neutron to proton ratio of free nucleons, π{sup −}/π{sup +} ratio as well as isospin-sensitive transverse and elliptic flows given by the two transport models with their “best settings”, all have obvious differences. Discrepancy of numerical value of isospin-sensitive n/p ratio of free nucleon from the two models mainly originates from different symmetry potentials used and discrepancies of numerical value of charged π{sup −}/π{sup +} ratio and isospin-sensitive flows mainly originate from different isospin-dependent nucleon–nucleon cross sections. These demonstrations call for more detailed studies on the model inputs (i.e., the density- and momentum-dependent symmetry potential and the isospin-dependent nucleon–nucleon cross section in medium) of isospin-dependent transport model used. The studies of model dependence of isospin sensitive observables can help nuclear physicists to pin down the density dependence of nuclear symmetry energy through comparison between experiments and theoretical simulations scientifically.

  3. Low- and high-density nuclear equation of state and the hyperon puzzle

    Energy Technology Data Exchange (ETDEWEB)

    Colucci, Giuseppe; Sedrakian, Armen [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik

    2013-07-01

    The measurements of the unusually high mass of the millisecond pulsar PSR J1614-2230 (1.97 ± 0.04 M {sub CircleDot}) imposes a strong constraint on the nuclear Equation of State (EoS), in particular for what concerns the finite density behaviour of nuclear and neutron matter. In my talk I first discuss a model for the low-density part of the EoS, based on chiral one-pion exchange. I consider a self-consistent approach at finite temperature and density and show that even in a fully-relativistic theory the one-pion exchange contribution is dominated by a contact interaction. Then, a relativistic mean-field approach is used to discuss the high-density part of the EoS, including the presence of hyperons. In the latter, a density dependent parametrization is used and a parameter study on the hyperon-scalar meson coupling is performed.

  4. Critic: a new program for the topological analysis of solid-state electron densities

    Science.gov (United States)

    Otero-de-la-Roza, A.; Blanco, M. A.; Pendás, A. Martín; Luaña, Víctor

    2009-01-01

    In this paper we introduce CRITIC, a new program for the topological analysis of the electron densities of crystalline solids. Two different versions of the code are provided, one adapted to the LAPW (Linear Augmented Plane Wave) density calculated by the WIEN2K package and the other to the ab initio Perturbed Ion ( aiPI) density calculated with the PI7 code. Using the converged ground state densities, CRITIC can locate their critical points, determine atomic basins and integrate properties within them, and generate several graphical representations which include topological atomic basins and primary bundles, contour maps of ρ and ∇ρ, vector maps of ∇ρ, chemical graphs, etc. Program summaryProgram title: CRITIC Catalogue identifier: AECB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL, version 3 No. of lines in distributed program, including test data, etc.: 1 206 843 No. of bytes in distributed program, including test data, etc.: 12 648 065 Distribution format: tar.gz Programming language: FORTRAN 77 and 90 Computer: Any computer capable of compiling Fortran Operating system: Unix, GNU/Linux Classification: 7.3 Nature of problem: Topological analysis of the electron density in periodic solids. Solution method: The automatic localization of the electron density critical points is based on a recursive partitioning of the Wigner-Seitz cell into tetrahedra followed by a Newton search from significant points on each tetrahedra. Plotting of and integration on the atomic basins is currently based on a new implementation of Keith's promega algorithm. Running time: Variable, depending on the task. From seconds to a few minutes for the localization of critical points. Hours to days for the determination of the atomic basins shape and properties. Times correspond to a typical 2007 PC.

  5. A Quasi-Solid-State Sodium-Ion Capacitor with High Energy Density.

    Science.gov (United States)

    Wang, Faxing; Wang, Xiaowei; Chang, Zheng; Wu, Xiongwei; Liu, Xiang; Fu, Lijun; Zhu, Yusong; Wu, Yuping; Huang, Wei

    2015-11-18

    A quasi-solid-state sodium-ion capacitor is demonstrated with nanoporous disordered carbon and macroporous graphene as the negative and positive electrodes, respectively, using a sodium-ion-conducting gel polymer electrolyte. It can operate at a cell voltage as high as 4.2 V with an energy density of record high 168 W h kg(-1). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Density-dependent electron scattering in photoexcited GaAs in strongly diffusive regime

    DEFF Research Database (Denmark)

    Mics, Zoltán; D’Angio, Andrea; Jensen, Søren A.

    2013-01-01

    In a series of systematic optical pump–terahertz probe experiments, we study the density-dependent electron scattering rate in photoexcited GaAs in the regime of strong carrier diffusion. The terahertz frequency-resolved transient sheet conductivity spectra are perfectly described by the Drude...... model, directly yielding the electron scattering rates. A diffusion model is applied to determine the spatial extent of the photoexcited electron-hole gas at each moment after photoexcitation, yielding the time-dependent electron density, and hence the density-dependent electron scattering time. We find...

  7. Time-dependent cell disintegration kinetics in lung tumors after irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Chvetsov, Alexei V; Palta, Jatinder J [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Nagata, Yasushi [Department of Therapeutic Radiology and Oncology, Kyoto University, Kyoto (Japan)], E-mail: chvetsov@ufl.edu

    2008-05-07

    We study the time-dependent disintegration kinetics of tumor cells that did not survive radiotherapy treatment. To evaluate the cell disintegration rate after irradiation, we studied the volume changes of solitary lung tumors after stereotactic radiotherapy. The analysis is performed using two approximations: (1) tumor volume is a linear function of the total cell number in the tumor and (2) the cell disintegration rate is governed by the exponential decay with constant risk, which is defined by the initial cell number and a half-life T{sub 1/2}. The half-life T{sub 1/2} is determined using the least-squares fit to the clinical data on lung tumor size variation with time after stereotactic radiotherapy. We show that the tumor volume variation after stereotactic radiotherapy of solitary lung tumors can be approximated by an exponential function. A small constant component in the volume variation does not change with time; however, this component may be the residual irregular density due to radiation fibrosis and was, therefore, subtracted from the total volume variation in our computations. Using computerized fitting of the exponent function to the clinical data for selected patients, we have determined that the average half-life T{sub 1/2} of cell disintegration is 28.2 days for squamous cell carcinoma and 72.4 days for adenocarcinoma. This model is needed for simulating the tumor volume variation during radiotherapy, which may be important for time-dependent treatment planning of proton therapy that is sensitive to density variations.

  8. Time-dependent density functional theory beyond Kohn-Sham Slater determinants.

    Science.gov (United States)

    Fuks, Johanna I; Nielsen, Søren E B; Ruggenthaler, Michael; Maitra, Neepa T

    2016-08-03

    When running time-dependent density functional theory (TDDFT) calculations for real-time simulations of non-equilibrium dynamics, the user has a choice of initial Kohn-Sham state, and typically a Slater determinant is used. We explore the impact of this choice on the exchange-correlation potential when the physical system begins in a 50 : 50 superposition of the ground and first-excited state of the system. We investigate the possibility of judiciously choosing a Kohn-Sham initial state that minimizes errors when adiabatic functionals are used. We find that if the Kohn-Sham state is chosen to have a configuration matching the one that dominates the interacting state, this can be achieved for a finite time duration for some but not all such choices. When the Kohn-Sham system does not begin in a Slater determinant, we further argue that the conventional splitting of the exchange-correlation potential into exchange and correlation parts has limited value, and instead propose a decomposition into a "single-particle" contribution that we denote v, and a remainder. The single-particle contribution can be readily computed as an explicit orbital-functional, reduces to exchange in the Slater determinant case, and offers an alternative to the adiabatic approximation as a starting point for TDDFT approximations.

  9. Antibody-dependent NK cell activation is associated with late kidney allograft dysfunction and the complement-independent alloreactive potential of donor-specific antibodies

    Directory of Open Access Journals (Sweden)

    Tristan Legris

    2016-08-01

    Full Text Available Although kidney transplantation remains the best treatment for end-stage renal failure, it is limited by chronic humoral aggression of the graft vasculature by donor-specific antibodies (DSAs. The complement-independent mechanisms that lead to the antibody-mediated rejection (ABMR of kidney allografts remain poorly understood. Increasing lines of evidence have revealed the relevance of natural killer (NK cells as innate immune effectors of antibody-dependent cellular cytotoxicity, but few studies have investigated their alloreactive potential in the context of solid organ transplantation. Our study aimed to investigate the potential contribution of the antibody-dependent alloreactive function of NK cells to kidney graft dysfunction. We first conducted an observational study to investigate whether the cytotoxic function of NK cells is associated with chronic allograft dysfunction. The NK-Cellular Humoral Activation Test (NK-CHAT was designed to evaluate the recipient and antibody-dependent reactivity of NK cells against allogeneic target cells. The release of CD107a/Lamp1+ cytotoxic granules, resulting from the recognition of rituximab-coated B cells by NK cells, was analyzed in 148 kidney transplant recipients (KTRs, mean graft duration: 6.2 years. Enhanced ADCC responsiveness was associated with reduced graft function and identified as an independent risk factor predicting a decline in the estimated glomerular filtration rate (eGFR over a 1-year period (hazard ratio: 2.83. In a second approach, we used the NK-CHAT to reveal the cytotoxic potential of circulating alloantibodies in vitro. The level of CD16 engagement resulting from the in vitro recognition of serum-coated allogeneic B cells or splenic cells was further identified as a specific marker of DSA-induced ADCC. The NK-CHAT scoring of sera obtained from 40 patients at the time of transplant biopsy was associated with ABMR diagnosis. Our findings indicate that despite the administration

  10. Oxidized low-density lipoproteins upregulate proline oxidase to initiate ROS-dependent autophagy.

    Science.gov (United States)

    Zabirnyk, Olga; Liu, Wei; Khalil, Shadi; Sharma, Anit; Phang, James M

    2010-03-01

    Epidemiological studies showed that high levels of oxidized low-density lipoproteins (oxLDLs) are associated with increased cancer risk. We examined the direct effect of physiologic concentrations oxLDL on cancer cells. OxLDLs were cytotoxic and activate both apoptosis and autophagy. OxLDLs have ligands for peroxisome proliferator-activated receptor gamma and upregulated proline oxidase (POX) through this nuclear receptor. We identified 7-ketocholesterol (7KC) as a main component responsible for the latter. To elucidate the role of POX in oxLDL-mediated cytotoxicity, we knocked down POX via small interfering RNA and found that this (i) further reduced viability of cancer cells treated with oxLDL; (ii) decreased oxLDL-associated reactive oxygen species generation; (iii) decreased autophagy measured via beclin-1 protein level and light-chain 3 protein (LC3)-I into LC3-II conversion. Using POX-expressing cell model, we established that single POX overexpression was sufficient to activate autophagy. Thus, it led to autophagosomes accumulation and increased conversion of LC3-I into LC3-II. Moreover, beclin-1 gene expression was directly dependent on POX catalytic activity, namely the generation of POX-dependent superoxide. We conclude that POX is critical in the cellular response to the noxious effects of oxLDL by activating protective autophagy.

  11. CD1d-dependent NKT cells play a protective role in acute and chronic arthritis models by ameliorating antigen-specific Th1 responses

    DEFF Research Database (Denmark)

    Teige, Anna; Bockermann, Robert; Hasan, Maruf

    2010-01-01

    -induced arthritis (AIA) and collagen-induced arthritis (CIA), to evaluate acute and chronic arthritis in CD1d knockout mice and mice depleted of NK1.1(+) cells. CD1d-deficient mice developed more severe AIA compared with wild-type littermates, with a higher degree of inflammation and proteoglycan depletion. Chronic...... arthritis in CIA was also worse in the absence of CD1d-dependent NKTs. Elevated levels of Ag-specific IFN-gamma production accompanied these findings rather than changes in IL-17alpha. Depletion of NK1.1(+) cells supported these findings in AIA and CIA. This report provides support for CD1d-dependent NKTs...

  12. Membrane microdomain-associated uroplakin IIIa contributes to Src-dependent mechanisms of anti-apoptotic proliferation in human bladder carcinoma cells

    Directory of Open Access Journals (Sweden)

    Shigeru Kihira

    2012-08-01

    Our previous study demonstrated that tyrosine phosphorylation of p145met/β-subunit of hepatocyte growth factor receptor by epidermal growth factor receptor and Src contributes to the anti-apoptotic growth of human bladder carcinoma cell 5637 under serum-starved conditions. Here, we show that some other cell lines of human bladder carcinoma, but not other types of human cancer cells, also exhibit Src-dependent, anti-apoptotic proliferation under serum-starved conditions, and that low-density, detergent-insoluble membrane microdomains (MD serve as a structural platform for signaling events involving p145met, EGFR, and Src. As an MD-associated molecule that may contribute to bladder carcinoma-specific cellular function, we identified uroplakin IIIa (UPIIIa, an urothelium-specific protein. Results obtained so far revealed: 1 UPIIIa undergoes partial proteolysis in serum-starved cells; 2 a specific antibody to the extracellular domain of UPIIIa inhibits the proteolysis of UPIIIa and the activation of Src, and promotes apoptosis in serum-starved cells; and 3 knockdown of UPIIIa by short interfering RNA also promotes apoptosis in serum-starved cells. GM6001, a potent inhibitor of matrix metalloproteinase (MMP, inhibits the proteolysis of UPIIIa and promotes apoptosis in serum-starved cells. Furthermore, serum starvation promotes expression and secretion of the heparin-binding EGF-like growth factor in a manner that depends on the functions of MMP, Src, and UPIIIa. These results highlight a hitherto unknown signaling network involving a subset of MD-associated molecules in the anti-apoptotic mechanisms of human bladder carcinoma cells.

  13. Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Sissay, Adonay [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Lopata, Kenneth, E-mail: klopata@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

    2016-09-07

    Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

  14. Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

    International Nuclear Information System (INIS)

    Sissay, Adonay; Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J.; Lopata, Kenneth

    2016-01-01

    Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

  15. Violations of the Born rule in cool state-dependent horizons

    Science.gov (United States)

    Marolf, Donald; Polchinski, Joseph

    2016-01-01

    The black hole information problem has motivated many proposals for new physics. One idea, known as state-dependence, is that quantum mechanics must be generalized to describe the physics of black holes, and that fixed linear operators do not provide the fundamental description of experiences for infalling observers. Instead, such experiences are to be described by operators with an extra dependence on the global quantum state. By generalizing a previous argument for firewalls in generic black holes, we show that any implementation of this idea strong enough to remove firewalls from generic states requires massive violations of the Born rule. We also demonstrate a sense in which such violations are visible to infalling observers involved in preparing the initial state of the black hole. We emphasize the generality of our results; no details of any specific proposal for state-dependence are required.

  16. Violations of the Born rule in cool state-dependent horizons

    Energy Technology Data Exchange (ETDEWEB)

    Marolf, Donald [Department of Physics, University of California,Santa Barbara, CA 93106-9530 (United States); Polchinski, Joseph [Kavli Institute for Theoretical Physics, University of California,Santa Barbara, CA 93106-4030 (United States)

    2016-01-04

    The black hole information problem has motivated many proposals for new physics. One idea, known as state-dependence, is that quantum mechanics must be generalized to describe the physics of black holes, and that fixed linear operators do not provide the fundamental description of experiences for infalling observers. Instead, such experiences are to be described by operators with an extra dependence on the global quantum state. By generalizing a previous argument for firewalls in generic black holes, we show that any implementation of this idea strong enough to remove firewalls from generic states requires massive violations of the Born rule. We also demonstrate a sense in which such violations are visible to infalling observers involved in preparing the initial state of the black hole. We emphasize the generality of our results; no details of any specific proposal for state-dependence are required.

  17. Gut Immune Maturation Depends on Colonization with a Host-Specific Microbiota

    Science.gov (United States)

    Chung, Hachung; Pamp, Sünje J.; Hill, Jonathan A.; Surana, Neeraj K.; Edelman, Sanna M.; Troy, Erin B.; Reading, Nicola C.; Villablanca, Eduardo J.; Wang, Sen; Mora, Jorge R.; Umesaki, Yoshinori; Mathis, Diane; Benoist, Christophe; Relman, David A.; Kasper, Dennis L.

    2012-01-01

    SUMMARY Gut microbial induction of host immune maturation exemplifies host-microbe mutualism. We colonized germ-free (GF) mice with mouse microbiota (MMb) or human microbiota (HMb) to determine whether small intestinal immune maturation depends on a coevolved host-specific microbiota. Gut bacterial numbers and phylum abundance were similar in MMb and HMb mice, but bacterial species differed, especially the Firmicutes. HMb mouse intestines had low levels of CD4+ and CD8+ T cells, few proliferating T cells, few dendritic cells, and low antimicrobial peptide expression–all characteristics of GF mice. Rat microbiota also failed to fully expand intestinal T cell numbers in mice. Colonizing GF or HMb mice with mouse-segmented filamentous bacteria (SFB) partially restored T cell numbers, suggesting that SFB and other MMb organisms are required for full immune maturation in mice. Importantly, MMb conferred better protection against Salmonella infection than HMb. A host-specific microbiota appears to be critical for a healthy immune system. PMID:22726443

  18. Cell-type specificity of ChIP-predicted transcription factor binding sites

    Directory of Open Access Journals (Sweden)

    Håndstad Tony

    2012-08-01

    Full Text Available Abstract Background Context-dependent transcription factor (TF binding is one reason for differences in gene expression patterns between different cellular states. Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq identifies genome-wide TF binding sites for one particular context—the cells used in the experiment. But can such ChIP-seq data predict TF binding in other cellular contexts and is it possible to distinguish context-dependent from ubiquitous TF binding? Results We compared ChIP-seq data on TF binding for multiple TFs in two different cell types and found that on average only a third of ChIP-seq peak regions are common to both cell types. Expectedly, common peaks occur more frequently in certain genomic contexts, such as CpG-rich promoters, whereas chromatin differences characterize cell-type specific TF binding. We also find, however, that genotype differences between the cell types can explain differences in binding. Moreover, ChIP-seq signal intensity and peak clustering are the strongest predictors of common peaks. Compared with strong peaks located in regions containing peaks for multiple transcription factors, weak and isolated peaks are less common between the cell types and are less associated with data that indicate regulatory activity. Conclusions Together, the results suggest that experimental noise is prevalent among weak peaks, whereas strong and clustered peaks represent high-confidence binding events that often occur in other cellular contexts. Nevertheless, 30-40% of the strongest and most clustered peaks show context-dependent regulation. We show that by combining signal intensity with additional data—ranging from context independent information such as binding site conservation and position weight matrix scores to context dependent chromatin structure—we can predict whether a ChIP-seq peak is likely to be present in other cellular contexts.

  19. Ubiquitin-specific protease 14 regulates cell proliferation and apoptosis in oral squamous cell carcinoma.

    Science.gov (United States)

    Chen, Xiangyun; Wu, Jingjing; Chen, Yitian; Ye, Dongxia; Lei, Hu; Xu, Hanzhang; Yang, Li; Wu, Yingli; Gu, Wenli

    2016-10-01

    Ubiquitin-specific protease 14, a deubiquitinating enzyme, has been implicated in the tumorigenesis and progression of several cancers, but its role in oral squamous cell carcinoma remains to be elucidated. The aim of this study was to explore the expression pattern and roles of Ubiquitin-specific protease 14 in the occurrence and development of oral squamous cell carcinoma. Interestingly, Ubiquitin-specific protease 14 was overexpressed in oral cancer tissues and cell lines at both mRNA and protein levels. b-AP15, a specific inhibitor of Ubiquitin-specific protease 14, significantly inhibited the growth of cancer cells and increased cell apoptosis in a dose-dependent manner. Moreover, knockdown of Ubiquitin-specific protease 14 by shRNA significantly inhibited the proliferation and migration of cancer cells in vitro. Finally, using a xenograft mouse model of oral squamous cell carcinoma, knockdown of Ubiquitin-specific protease 14 markedly inhibited tumor growth and triggered the cancer cell apoptosis in vivo, supporting previous results. In conclusion, for the first time we have demonstrated the expression pattern of Ubiquitin-specific protease 14 in oral squamous cell carcinoma and verified a relationship with tumor growth and metastasis. These results may highlight new therapeutic strategies for tumor treatment, application of Ubiquitin-specific protease 14 selective inhibitor, such as b-AP15, or knockdown by shRNA. Collectively, Ubiquitin-specific protease 14 could be a potential therapeutic target for oral squamous cell carcinoma patients. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Effective size of density-dependent two-sex populations: the effect of mating systems.

    Science.gov (United States)

    Myhre, A M; Engen, S; SAEther, B-E

    2017-08-01

    Density dependence in vital rates is a key feature affecting temporal fluctuations of natural populations. This has important implications for the rate of random genetic drift. Mating systems also greatly affect effective population sizes, but knowledge of how mating system and density regulation interact to affect random genetic drift is poor. Using theoretical models and simulations, we compare N e in short-lived, density-dependent animal populations with different mating systems. We study the impact of a fluctuating, density-dependent sex ratio and consider both a stable and a fluctuating environment. We find a negative relationship between annual N e /N and adult population size N due to density dependence, suggesting that loss of genetic variation is reduced at small densities. The magnitude of this decrease was affected by mating system and life history. A male-biased, density-dependent sex ratio reduces the rate of genetic drift compared to an equal, density-independent sex ratio, but a stochastic change towards male bias reduces the N e /N ratio. Environmental stochasticity amplifies temporal fluctuations in population size and is thus vital to consider in estimation of effective population sizes over longer time periods. Our results on the reduced loss of genetic variation at small densities, particularly in polygamous populations, indicate that density regulation may facilitate adaptive evolution at small population sizes. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

  1. Engineering photonic density of states using metamaterials

    DEFF Research Database (Denmark)

    Jacob, Z.; Kim, J.Y.; Naik, G.V.

    2010-01-01

    The photonic density of states (PDOS), like its electronic counterpart, is one of the key physical quantities governing a variety of phenomena and hence PDOS manipulation is the route to new photonic devices. The PDOS is conventionally altered by exploiting the resonance within a device such as a......The photonic density of states (PDOS), like its electronic counterpart, is one of the key physical quantities governing a variety of phenomena and hence PDOS manipulation is the route to new photonic devices. The PDOS is conventionally altered by exploiting the resonance within a device...... such as a microcavity or a bandgap structure like a photonic crystal. Here we show that nanostructured metamaterials with hyperbolic dispersion can dramatically enhance the photonic density of states paving the way for metamaterial-based PDOS engineering....

  2. The effect of electrodeposition process parameters on the current density distribution in an electrochemical cell

    Directory of Open Access Journals (Sweden)

    R. M. STEVANOVIC

    2001-02-01

    Full Text Available Cell voltage – current density dependences for a model electrochemical cell of fixed geometry were calculated for different electrolyte conductivities, Tafel slopes and cathodic exchange current densities. The ratio between the current density at the part of the cathode nearest to the anode and the one furthest away were taken as a measure for the estimation of the current density distribution. The calculations reveal that increasing the conductivity of the electrolyte, as well as increasing the cathodic Tafel slope should both improve the current density distribution. Also, the distribution should be better under total activation control or total diffusion control rather than at mixed activation-diffusion-Ohmic control of the deposition process. On the contrary, changes in the exchange current density should not affect it. These results, being in agreement with common knowledge about the influence of different parameters on the current distribution in an electrochemical cell, demonstrate that a quick estimation of the current distribution can be performed by a simple comparison of the current density at the point of the cathode closest to anode with that at furthest point.

  3. Comprehensive benchmarking reveals H2BK20 acetylation as a distinctive signature of cell-state-specific enhancers and promoters.

    Science.gov (United States)

    Kumar, Vibhor; Rayan, Nirmala Arul; Muratani, Masafumi; Lim, Stefan; Elanggovan, Bavani; Xin, Lixia; Lu, Tess; Makhija, Harshyaa; Poschmann, Jeremie; Lufkin, Thomas; Ng, Huck Hui; Prabhakar, Shyam

    2016-05-01

    Although over 35 different histone acetylation marks have been described, the overwhelming majority of regulatory genomics studies focus exclusively on H3K27ac and H3K9ac. In order to identify novel epigenomic traits of regulatory elements, we constructed a benchmark set of validated enhancers by performing 140 enhancer assays in human T cells. We tested 40 chromatin signatures on this unbiased enhancer set and identified H2BK20ac, a little-studied histone modification, as the most predictive mark of active enhancers. Notably, we detected a novel class of functionally distinct enhancers enriched in H2BK20ac but lacking H3K27ac, which was present in all examined cell lines and also in embryonic forebrain tissue. H2BK20ac was also unique in highlighting cell-type-specific promoters. In contrast, other acetylation marks were present in all active promoters, regardless of cell-type specificity. In stimulated microglial cells, H2BK20ac was more correlated with cell-state-specific expression changes than H3K27ac, with TGF-beta signaling decoupling the two acetylation marks at a subset of regulatory elements. In summary, our study reveals a previously unknown connection between histone acetylation and cell-type-specific gene regulation and indicates that H2BK20ac profiling can be used to uncover new dimensions of gene regulation. © 2016 Kumar et al.; Published by Cold Spring Harbor Laboratory Press.

  4. Betulinic acid inhibits colon cancer cell and tumor growth and induces proteasome-dependent and -independent downregulation of specificity proteins (Sp transcription factors

    Directory of Open Access Journals (Sweden)

    Pathi Satya

    2011-08-01

    Full Text Available Abstract Background Betulinic acid (BA inhibits growth of several cancer cell lines and tumors and the effects of BA have been attributed to its mitochondriotoxicity and inhibition of multiple pro-oncogenic factors. Previous studies show that BA induces proteasome-dependent degradation of specificity protein (Sp transcription factors Sp1, Sp3 and Sp4 in prostate cancer cells and this study focused on the mechanism of action of BA in colon cancer cells. Methods The effects of BA on colon cancer cell proliferation and apoptosis and tumor growth in vivo were determined using standardized assays. The effects of BA on Sp proteins and Sp-regulated gene products were analyzed by western blots, and real time PCR was used to determine microRNA-27a (miR-27a and ZBTB10 mRNA expression. Results BA inhibited growth and induced apoptosis in RKO and SW480 colon cancer cells and inhibited tumor growth in athymic nude mice bearing RKO cells as xenograft. BA also decreased expression of Sp1, Sp3 and Sp4 transcription factors which are overexpressed in colon cancer cells and decreased levels of several Sp-regulated genes including survivin, vascular endothelial growth factor, p65 sub-unit of NFκB, epidermal growth factor receptor, cyclin D1, and pituitary tumor transforming gene-1. The mechanism of action of BA was dependent on cell context, since BA induced proteasome-dependent and proteasome-independent downregulation of Sp1, Sp3 and Sp4 in SW480 and RKO cells, respectively. In RKO cells, the mechanism of BA-induced repression of Sp1, Sp3 and Sp4 was due to induction of reactive oxygen species (ROS, ROS-mediated repression of microRNA-27a, and induction of the Sp repressor gene ZBTB10. Conclusions These results suggest that the anticancer activity of BA in colon cancer cells is due, in part, to downregulation of Sp1, Sp3 and Sp4 transcription factors; however, the mechanism of this response is cell context-dependent.

  5. Betulinic acid inhibits colon cancer cell and tumor growth and induces proteasome-dependent and -independent downregulation of specificity proteins (Sp) transcription factors

    International Nuclear Information System (INIS)

    Chintharlapalli, Sudhakar; Papineni, Sabitha; Lei, Ping; Pathi, Satya; Safe, Stephen

    2011-01-01

    Betulinic acid (BA) inhibits growth of several cancer cell lines and tumors and the effects of BA have been attributed to its mitochondriotoxicity and inhibition of multiple pro-oncogenic factors. Previous studies show that BA induces proteasome-dependent degradation of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 in prostate cancer cells and this study focused on the mechanism of action of BA in colon cancer cells. The effects of BA on colon cancer cell proliferation and apoptosis and tumor growth in vivo were determined using standardized assays. The effects of BA on Sp proteins and Sp-regulated gene products were analyzed by western blots, and real time PCR was used to determine microRNA-27a (miR-27a) and ZBTB10 mRNA expression. BA inhibited growth and induced apoptosis in RKO and SW480 colon cancer cells and inhibited tumor growth in athymic nude mice bearing RKO cells as xenograft. BA also decreased expression of Sp1, Sp3 and Sp4 transcription factors which are overexpressed in colon cancer cells and decreased levels of several Sp-regulated genes including survivin, vascular endothelial growth factor, p65 sub-unit of NFκB, epidermal growth factor receptor, cyclin D1, and pituitary tumor transforming gene-1. The mechanism of action of BA was dependent on cell context, since BA induced proteasome-dependent and proteasome-independent downregulation of Sp1, Sp3 and Sp4 in SW480 and RKO cells, respectively. In RKO cells, the mechanism of BA-induced repression of Sp1, Sp3 and Sp4 was due to induction of reactive oxygen species (ROS), ROS-mediated repression of microRNA-27a, and induction of the Sp repressor gene ZBTB10. These results suggest that the anticancer activity of BA in colon cancer cells is due, in part, to downregulation of Sp1, Sp3 and Sp4 transcription factors; however, the mechanism of this response is cell context-dependent

  6. Microstructure characterisation of solid oxide electrolysis cells operated at high current density

    DEFF Research Database (Denmark)

    Bowen, Jacob R.; Bentzen, Janet Jonna; Chen, Ming

    degradation of cell components in relation to the loss of electrochemical performance specific to the mode of operation. Thus descriptive microstructure characterization methods are required in combination with electrochemical characterization methods to decipher degradation mechanisms. In the present work......High temperature solid oxide cells can be operated either as fuel cells or electrolysis cells for efficient power generation or production of hydrogen from steam or synthesis gas (H2 + CO) from steam and CO2 respectively. When operated under harsh conditions, they often exhibit microstructural...... quantified using the mean linear intercept method as a function of current density and correlated to increases in serial resistance. The above structural changes are then compared in terms of electrode degradation observed during the co-electrolysis of steam and CO2 at current densities up to -1.5 A cm-2...

  7. Ecological change points: The strength of density dependence and the loss of history.

    Science.gov (United States)

    Ponciano, José M; Taper, Mark L; Dennis, Brian

    2018-05-01

    Change points in the dynamics of animal abundances have extensively been recorded in historical time series records. Little attention has been paid to the theoretical dynamic consequences of such change-points. Here we propose a change-point model of stochastic population dynamics. This investigation embodies a shift of attention from the problem of detecting when a change will occur, to another non-trivial puzzle: using ecological theory to understand and predict the post-breakpoint behavior of the population dynamics. The proposed model and the explicit expressions derived here predict and quantify how density dependence modulates the influence of the pre-breakpoint parameters into the post-breakpoint dynamics. Time series transitioning from one stationary distribution to another contain information about where the process was before the change-point, where is it heading and how long it will take to transition, and here this information is explicitly stated. Importantly, our results provide a direct connection of the strength of density dependence with theoretical properties of dynamic systems, such as the concept of resilience. Finally, we illustrate how to harness such information through maximum likelihood estimation for state-space models, and test the model robustness to widely different forms of compensatory dynamics. The model can be used to estimate important quantities in the theory and practice of population recovery. Copyright © 2018 Elsevier Inc. All rights reserved.

  8. Microvessel and mast cell densities in malignant laryngeal neoplasm

    Directory of Open Access Journals (Sweden)

    Balica Nicolae Constantin

    2014-01-01

    Full Text Available Laryngeal neoplasm contributes to 30-40% of carcinomas of the head and neck. Mast cells are normal connective tissue residents, well represented in the respiratory tract. Experimental evidence suggests that the growth of a tumor beyond a certain size requires angiogenesis, which may also permit metastasis. The aim of this study was to evaluate the correlation between mast cell density, microvascular density, histopathological type and histological grade. Our study included 38 laryngeal carcinomas as follows: adenoid cystic carcinoma (2 cases, malignant papilloma (2 cases and squamous cell carcinoma (34 cases. The combined technique of CD 34-alcian blue safranin (ABS was used to identify microvessel and mast cell density, which was quantified by the hot spot method. A significant correlation was found between both mast cell and microvascular density, and G1/G2 histological grade (p=0.002 and p=0.004, respectively. Squamous cell carcinoma was significantly correlated with mast cell density (p=0.003, but not with microvascular density (p=0.454.

  9. State-Dependent Impulsive Control Strategies for a Tumor-Immune Model

    Directory of Open Access Journals (Sweden)

    Kwang Su Kim

    2016-01-01

    Full Text Available Controlling the number of tumor cells leads us to expect more efficient strategies for treatment of tumor. Towards this goal, a tumor-immune model with state-dependent impulsive treatments is established. This model may give an efficient treatment schedule to control tumor’s abnormal growth. By using the Poincaré map and analogue of Poincaré criterion, some conditions for the existence and stability of a positive order-1 periodic solution of this model are obtained. Moreover, we carry out numerical simulations to illustrate the feasibility of our main results and compare fixed-time impulsive treatment effects with state-dependent impulsive treatment effects. The results of our simulations say that, in determining optimal treatment timing, the model with state-dependent impulsive control is more efficient than that with fixed-time impulsive control.

  10. Isolating peripheral lymphocytes by density gradient centrifugation and magnetic cell sorting.

    Science.gov (United States)

    Brosseron, Frederic; Marcus, Katrin; May, Caroline

    2015-01-01

    Combining density gradient centrifugation with magnetic cell sorting provides a powerful tool to isolate blood cells with high reproducibility, yield, and purity. It also allows for subsequent separation of multiple cell types, resulting in the possibility to analyze different purified fractions from one donor's sample. The centrifugation step divides whole blood into peripheral blood mononuclear cells (PBMC), erythrocytes, and platelet-rich plasma. In the following, lymphocyte subtypes can be consecutively isolated from the PBMC fraction. This chapter describes enrichment of erythrocytes, CD14-positive monocytes and CD3-positive T lymphocytes. Alternatively, other cell types can be targeted by using magnetic beads specific for the desired subpopulation.

  11. Density dependent forces and large basis structure models in the analyses of 12C(p,p') reactions at 135 MeV

    International Nuclear Information System (INIS)

    Bauhoff, W.; Collins, S.F.; Henderson, R.S.

    1983-01-01

    Differential cross-sections have been measured for the elastic and inelastic scattering of 135 MeV protons from 12 C. The data from the transitions to 9 select states up to 18.3 MeV in excitation have been analysed using a distorted wave approximation with various microscopic model nuclear structure transition densities and free and density dependent two nucleon t-matrices. Clear signatures of the density dependence of the t-matrix are defined and the utility of select transitions to test different attributes of that t-matrix when good nuclear structure models are used is established

  12. Effects of Density-Dependent Quark Mass on Phase Diagram of Color-Flavor-Locked Quark Matter

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Considering the density dependence of quark mass, we investigate the phase transition between the (unpaired) strange quark matter and the color-flavor-locked matter, which are supposed to be two candidates for the ground state of strongly interacting matter. We find that if the current mass of strange quark ms is small, the strange quark matter remains stable unless the baryon density is very high. If ms is large, the phase transition from the strange quark matter to the color-flavor-locked matter in particular to its gapless phase is found to be different from the results predicted by previous works. A complicated phase diagram of three-flavor quark matter is presented, in which the color-flavor-locked phase region is suppressed for moderate densities.

  13. Recruitment of Mediator Complex by Cell Type and Stage-Specific Factors Required for Tissue-Specific TAF Dependent Gene Activation in an Adult Stem Cell Lineage.

    Science.gov (United States)

    Lu, Chenggang; Fuller, Margaret T

    2015-12-01

    Onset of terminal differentiation in adult stem cell lineages is commonly marked by robust activation of new transcriptional programs required to make the appropriate differentiated cell type(s). In the Drosophila male germ line stem cell lineage, the switch from proliferating spermatogonia to spermatocyte is accompanied by one of the most dramatic transcriptional changes in the fly, as over 1000 new transcripts turn on in preparation for meiosis and spermatid differentiation. Here we show that function of the coactivator complex Mediator is required for activation of hundreds of new transcripts in the spermatocyte program. Mediator appears to act in a sequential hierarchy, with the testis activating Complex (tMAC), a cell type specific form of the Mip/dREAM general repressor, required to recruit Mediator subunits to the chromatin, and Mediator function required to recruit the testis TAFs (tTAFs), spermatocyte specific homologs of subunits of TFIID. Mediator, tMAC and the tTAFs co-regulate expression of a major set of spermatid differentiation genes. The Mediator subunit Med22 binds the tMAC component Topi when the two are coexpressed in S2 cells, suggesting direct recruitment. Loss of Med22 function in spermatocytes causes meiosis I maturation arrest male infertility, similar to loss of function of the tMAC subunits or the tTAFs. Our results illuminate how cell type specific versions of the Mip/dREAM complex and the general transcription machinery cooperate to drive selective gene activation during differentiation in stem cell lineages.

  14. State-to-State Mode Specificity: Energy Sequestration and Flow Gated by Transition State.

    Science.gov (United States)

    Zhao, Bin; Sun, Zhigang; Guo, Hua

    2015-12-23

    Energy flow and sequestration at the state-to-state level are investigated for a prototypical four-atom reaction, H2 + OH → H + H2O, using a transition-state wave packet (TSWP) method. The product state distribution is found to depend strongly on the reactant vibrational excitation, indicating mode specificity at the state-to-state level. From a local-mode perspective, it is shown that the vibrational excitation of the H2O product derives from two different sources, one attributable to the energy flow along the reaction coordinate into the newly formed OH bond and the other due to the sequestration of the vibrational energy in the OH spectator moiety during the reaction. The analysis provided a unified interpretation of some seemingly contradicting experimental observations. It is further shown that the transfer of vibrational energy from the OH reactant to H2O product is gated by the transition state, accomplished coherently by multiple TSWPs with the corresponding OH vibrational excitation.

  15. Phage-Bacterial Dynamics with Spatial Structure: Self Organization around Phage Sinks Can Promote Increased Cell Densities.

    Science.gov (United States)

    Bull, James J; Christensen, Kelly A; Scott, Carly; Jack, Benjamin R; Crandall, Cameron J; Krone, Stephen M

    2018-01-29

    Bacteria growing on surfaces appear to be profoundly more resistant to control by lytic bacteriophages than do the same cells grown in liquid. Here, we use simulation models to investigate whether spatial structure per se can account for this increased cell density in the presence of phages. A measure is derived for comparing cell densities between growth in spatially structured environments versus well mixed environments (known as mass action). Maintenance of sensitive cells requires some form of phage death; we invoke death mechanisms that are spatially fixed, as if produced by cells. Spatially structured phage death provides cells with a means of protection that can boost cell densities an order of magnitude above that attained under mass action, although the effect is sometimes in the opposite direction. Phage and bacteria self organize into separate refuges, and spatial structure operates so that the phage progeny from a single burst do not have independent fates (as they do with mass action). Phage incur a high loss when invading protected areas that have high cell densities, resulting in greater protection for the cells. By the same metric, mass action dynamics either show no sustained bacterial elevation or oscillate between states of low and high cell densities and an elevated average. The elevated cell densities observed in models with spatial structure do not approach the empirically observed increased density of cells in structured environments with phages (which can be many orders of magnitude), so the empirical phenomenon likely requires additional mechanisms than those analyzed here.

  16. Effect of the density of the electronic states at the valence orbital of the bridge redox molecule on the dependence of the tunnel current on the overvoltage in the case of fully adiabatic electron transition

    International Nuclear Information System (INIS)

    Medvedev, Igor G.

    2008-01-01

    Effect of the density of the electronic states at the valence orbital of the bridge redox molecule on the dependence of the tunnel current on the overvoltage and on the width at half maximum of the current-overvoltage curve is studied. A number of the approximate expressions for the density of states, the tunnel current and the width are obtained in the fully adiabatic limit for different particular cases. It is shown that at small values of the coupling of the electronic levels of the electrodes with the valence orbital of the redox molecule and the small values of the bias voltage two regions of the reorganization Gibbs energy exist with different dependence of the width on the reorganization Gibbs energy. The results of calculations of the density of states, the tunnel current and the width are presented and used for the interpretation of the experimental data [N.G. Tao, Phys. Rev. Lett. 76 (1996) 4066, I. Visoly-Fisher, K. Daie, Y. Terazono, C. Herrero, F. Fungo, L. Otero, E. Durantini, J.J. Silber, L. Sereno, D. Gust, T.A. Moore, A.L. Moore, S.M. Lindsay, PNAS 103 (2006) 8686

  17. CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, accumulates at the postsynaptic density in an activity-dependent manner

    Energy Technology Data Exchange (ETDEWEB)

    Dosemeci, Ayse, E-mail: dosemeca@mail.nih.gov [Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892 (United States); Thein, Soe; Yang, Yijung; Reese, Thomas S. [Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892 (United States); Tao-Cheng, Jung-Hwa [EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892 (United States)

    2013-01-04

    Highlights: Black-Right-Pointing-Pointer CYLD is a deubiquitinase specific for lysine63-linked polyubiquitins. Black-Right-Pointing-Pointer Presence of CYLD in PSDs is established by biochemistry and immunoEM. Black-Right-Pointing-Pointer CYLD accumulates on PSDs upon depolarization of neurons. Black-Right-Pointing-Pointer Accumulation of CYLD at PSDs may regulate trafficking/degradation of synaptic proteins. -- Abstract: Polyubiquitin chains on proteins flag them for distinct fates depending on the type of polyubiquitin linkage. While lysine48-linked polyubiquitination directs proteins to proteasomal degradation, lysine63-linked polyubiquitination promotes different protein trafficking and is involved in autophagy. Here we show that postsynaptic density (PSD) fractions from adult rat brain contain deubiquitinase activity that targets both lysine48 and lysine63-linked polyubiquitins. Comparison of PSD fractions with parent subcellular fractions by Western immunoblotting reveals that CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, is highly enriched in the PSD fraction. Electron microscopic examination of hippocampal neurons in culture under basal conditions shows immunogold label for CYLD at the PSD complex in approximately one in four synapses. Following depolarization by exposure to high K+, the proportion of CYLD-labeled PSDs as well as the labeling intensity of CYLD at the PSD increased by more than eighty percent, indicating that neuronal activity promotes accumulation of CYLD at the PSD. An increase in postsynaptic CYLD following activity would promote removal of lysine63-polyubiquitins from PSD proteins and thus could regulate their trafficking and prevent their autophagic degradation.

  18. Multiconfiguration Pair-Density Functional Theory Outperforms Kohn-Sham Density Functional Theory and Multireference Perturbation Theory for Ground-State and Excited-State Charge Transfer.

    Science.gov (United States)

    Ghosh, Soumen; Sonnenberger, Andrew L; Hoyer, Chad E; Truhlar, Donald G; Gagliardi, Laura

    2015-08-11

    The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn-Sham (KS) density functional theory (DFT). KS-DFT exchange-correlation functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a theory called multiconfiguration pair-density functional theory (MC-PDFT), which is based on a combination of multiconfiguration wave function theory with a new type of density functional called an on-top density functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top density functionals obtained by translating KS exchange-correlation functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation functional or CASPT2 wave function theory. For excited-state charge transfer, MC-PDFT (unlike KS-DFT) shows qualitatively correct behavior at long-range with great improvement in predicted excitation energies.

  19. IRF8-dependent DCs play a key role in the regulation of CD8 T cell responses to epithelial-derived antigen in the steady state but not in inflammation

    DEFF Research Database (Denmark)

    Joeris, Thorsten

    Along the process of epithelial self-renewal, antigens derived from apoptotic intestinal epithelial cells (IECs) are taken up by antigen presenting cells (APCs), transported to gut-draining lymph nodes and crosspresented to CD8 T cells. In steady state, rapid tolerization of CD8 T cells reactive...... towards epithelialderived antigens is crucial to maintain tissue homeostasis. Since IRF8-dependent dendritic dells (IRF8-DCs) have superior cross-presenting capabilities, we aimed to investigate their role in this process. IFABP-tOva mice, expressing the model-antigen Ovalbumin (Ova) in IECs, were used...... as recipients to set up chimeras using either CD11c-cre.Irf8fl/fl bone marrow, which cannot generate IRF8-DCs, or cre-negative Irf8fl/fl control bone marrow. Whereas transfer of Ova-specific CD8 T cells (OT-I cells) to control chimeras resulted in their rapid tolerization, OT-I cells transferred to CD11c...

  20. Effect of wetting-layer density of states on the gain and phase recovery dynamics of quantum-dot semiconductor optical amplifiers

    International Nuclear Information System (INIS)

    Kim, Jungho; Yu, Bong-Ahn

    2015-01-01

    We numerically investigate the effect of the wetting-layer (WL) density of states on the gain and phase recovery dynamics of quantum-dot semiconductor optical amplifiers in both electrical and optical pumping schemes by solving 1088 coupled rate equations. The temporal variations of the ultrafast gain and phase recovery responses at the ground state (GS) are calculated as a function of the WL density of states. The ultrafast gain recovery responses do not significantly depend on the WL density of states in the electrical pumping scheme and the three optical pumping schemes such as the optical pumping to the WL, the optical pumping to the excited state ensemble, and the optical pumping to the GS ensemble. The ultrafast phase recovery responses are also not significantly affected by the WL density of states except the optical pumping to the WL, where the phase recovery component caused by the WL becomes slowed down as the WL density of states increases. (paper)

  1. Studies on ADCC (antibody-dependent cell-mediated cytotoxicity) using sheep red blood cells as target cells, 2

    International Nuclear Information System (INIS)

    Ichikawa, Yukinobu; Takaya, Masatoshi; Arimori, Shigeru

    1979-01-01

    A non-specific cytotoxic mediator from effector cells (human peripheral blood leukocytes) was investigated in the ADCC (antibody-dependent cell-mediated cytotoxicity) system using antibody-coated sheep red blood cells (SRBC) as target cells. 51 Cr-labelled homologous (sheep) or heterologous (human) red blood cells were used as adjacent cells. Either crude lymphocyte fraction, phagocyte depleted fraction or granulocyte rich fraction separated from human peripheral leukocytes showed moderate cytotoxic effect on homologous adjacent cells, however no cytotoxic activity on heterologous adjacent cells was demonstrated in any leukocyte fraction. This suggests that the cytotoxic effects on homologous adjacent cells were resulted from the translocation of antibody molecules to adjacent cells from antibody-coated target cells. We concluded that the cytotoxic mechanism in this ADCC system was not mediated by non-specific soluble factors released from either human peripheral lymphocytes, monocytes or granulocytes. (author)

  2. Dependence of the critical current density on the history of magnetic field and temperature

    International Nuclear Information System (INIS)

    Kuepfer, H.

    1976-08-01

    The dependence of the volume pinning force on different paths taken to arrive at a state (H,T) is investigated. The local magnetic induction is measured by means of an ac technique on samples with different Hsub(c), kappa, pinning centres and densities. Line pinning and a distorted flux line lattice are properties of those samples which show the above mentioned history dependence. Using the model of E.J. Kramer it is deduced the reason of the history effect is the dependence of the shear modulus on the defect structure of the flux line lattice. The differences occur in the lower field region and are also observed in materials with kappa approximately = 40 and large volume pinning forces. (orig.) [de

  3. Linear-chain model to explain density of states and Tsub(c) changes with atomic ordering

    International Nuclear Information System (INIS)

    Junod, A.

    1978-01-01

    The effect of long-range atomic order on the electronic density of states has been recalculated for the A15-type structure within the linear-chain model. It is found that a defect concentration c reduces the density of states at the Fermi level by a factor (1 + c/c 0 )(c/c 0 ) -3 [ln(1 + c/c 0 )] 3 . This result is in qualitative agreement with experimental data on the specific heat, magnetic susceptibility and superconducting transition temperature of V 3 Au. (author)

  4. Breaking down pluripotency in the porcine embryo reveals both a premature and reticent stem cell state in the inner cell mass and unique expression profiles of the naive and primed stem cell states.

    Science.gov (United States)

    Hall, Vanessa Jane; Hyttel, Poul

    2014-09-01

    To date, it has been difficult to establish bona fide porcine embryonic stem cells (pESC) and stable induced pluripotent stem cells. Reasons for this remain unclear, but they may depend on inappropriate culture conditions. This study reports the most insights to date on genes expressed in the pluripotent cells of the porcine embryo, namely the inner cell mass (ICM), the trophectoderm-covered epiblast (EPI), and the embryonic disc epiblast (ED). Specifically, we reveal that the early porcine ICM represents a premature state of pluripotency due to lack of translation of key pluripotent proteins, and the late ICM enters a transient, reticent pluripotent state which lacks expression of most genes associated with pluripotency. We describe a unique expression profile of the porcine EPI, reflecting the naive stem cell state, including expression of OCT4, NANOG, CRIPTO, and SSEA-1; weak expression of NrOB1 and REX1; but very limited expression of genes in classical pathways involved in regulating pluripotency. The porcine ED, reflecting the primed stem cell state, can be characterized by the expression of OCT4, NANOG, SOX2, KLF4, cMYC, REX1, CRIPTO, and KLF2. Further cell culture experiments using inhibitors against FGF, JAK/STAT, BMP, WNT, and NODAL pathways on cell cultures derived from day 5 and 10 embryos reveal the importance of FGF, JAK/STAT, and BMP signaling in maintaining cell proliferation of pESCs in vitro. Together, this article provides new insights into the regulation of pluripotency, revealing unique stem cell states in the different porcine stem cell populations derived from the early developing embryo.

  5. Interpretation of monoclinic hafnia valence electron energy-loss spectra by time-dependent density functional theory

    Science.gov (United States)

    Hung, L.; Guedj, C.; Bernier, N.; Blaise, P.; Olevano, V.; Sottile, F.

    2016-04-01

    We present the valence electron energy-loss spectrum and the dielectric function of monoclinic hafnia (m -HfO2) obtained from time-dependent density-functional theory (TDDFT) predictions and compared to energy-filtered spectroscopic imaging measurements in a high-resolution transmission-electron microscope. Fermi's golden rule density-functional theory (DFT) calculations can capture the qualitative features of the energy-loss spectrum, but we find that TDDFT, which accounts for local-field effects, provides nearly quantitative agreement with experiment. Using the DFT density of states and TDDFT dielectric functions, we characterize the excitations that result in the m -HfO2 energy-loss spectrum. The sole plasmon occurs between 13 and 16 eV, although the peaks ˜28 and above 40 eV are also due to collective excitations. We furthermore elaborate on the first-principles techniques used, their accuracy, and remaining discrepancies among spectra. More specifically, we assess the influence of Hf semicore electrons (5 p and 4 f ) on the energy-loss spectrum, and find that the inclusion of transitions from the 4 f band damps the energy-loss intensity in the region above 13 eV. We study the impact of many-body effects in a DFT framework using the adiabatic local-density approximation (ALDA) exchange-correlation kernel, as well as from a many-body perspective using "scissors operators" matched to an ab initio G W calculation to account for self-energy corrections. These results demonstrate some cancellation of errors between self-energy and excitonic effects, even for excitations from the Hf 4 f shell. We also simulate the dispersion with increasing momentum transfer for plasmon and collective excitation peaks.

  6. Unraveling surface and bulk trap states in lead halide perovskite solar cells using impedance spectroscopy

    Science.gov (United States)

    Han, Changfeng; Wang, Kai; Zhu, Xixiang; Yu, Haomiao; Sun, Xiaojuan; Yang, Qin; Hu, Bin

    2018-03-01

    Organic-inorganic hybrid perovskites (OIHPs) have been widely recognized as an excellent candidate for next-generation photovoltaic materials because of their highly efficient power conversion. Acquiring a complete understanding of trap states and dielectric properties in OIHP-based solar cells at the steady state is highly desirable in order to further explore and improve their optoelectronic functionalities and properties. We report CH3NH3PbI3-x Cl x -based planar solar cells with a power conversion efficiency (PCE) of 15.8%. The illumination intensity dependence of the current density-voltage (J-V) revealed the presence of trap-assisted recombination at low fluences. Non-destructive ac impedance spectroscopy (ac-IS) was applied to characterize the device at the steady state. The capacitance-voltage (C-V) spectra exhibited some distinct variations at a wide range of ac modulation frequencies with and without photo-excitations. Since the frequency-dependent chemical capacitance ({{C}μ }) is concerned with the surface and bulk related density of states (DOS) in CH3NH3PbI3-x Cl x , we verified this by fitting the corresponding DOS by a Gaussian distribution function. We ascertained that the electronic sub-gap trap states present in the solution processed CH3NH3PbI3-x Cl x and their distribution differs from the surface to the bulk. In fact, we demonstrated that both surfaces that were adjacent to the electron and hole transport layers featured analogous DOS. Despite this, photo- and bias-induced giant dielectric responses (i.e. both real and imaginary parts) were detected. A remarkable reduction of {{C}μ } at higher frequencies (i.e. more than 100 kHz) was ascribed to the effect of dielectric loss in CH3NH3PbI3-x Cl x .

  7. Disentangling the effects of climate, density dependence, and harvest on an iconic large herbivore's population dynamics

    DEFF Research Database (Denmark)

    Koons, David; Colchero, Fernando; Hersey, Kent

    2015-01-01

    Understanding the relative effects of climate, harvest, and density dependence on population dynamics is critical for guiding sound population management, especially for ungulates in arid and semi-arid environments experiencing climate change. To address these issues for bison in southern Utah, we...... than precipitation and other temperature-related variables (model weight > 3 times more than that for other climate variables). Although we hypothesized that harvest is the primary driving force of bison population dynamics in southern Utah, our elasticity analysis indicated that changes in early...... spring temperature could have a greater ‘relative effect’ on equilibrium abundance than either harvest or the strength of density dependence. Our findings highlight the utility of incorporating elasticity analyses into state-space population models, and the need to include climatic processes in wildlife...

  8. A numerical study of spin-dependent organization of alkali-metal atomic clusters using density-functional method

    International Nuclear Information System (INIS)

    Liu Xuan; Ito, Haruhiko; Torikai, Eiko

    2012-01-01

    We calculate the different geometric isomers of spin clusters composed of a small number of alkali-metal atoms using the UB3LYP density-functional method. The electron density distribution of clusters changes according to the value of total spin. Steric structures as well as planar structures arise when the number of atoms increases. The lowest spin state is the most stable and Li n , Na n , K n , Rb n , and Cs n with n = 2–8 can be formed in higher spin states. In the highest spin state, the preparation of clusters depends on the kind and the number of constituent atoms. The interaction energy between alkali-metal atoms and rare-gas atoms is smaller than the binding energy of spin clusters. Consequently, it is possible to self-organize the alkali-metal-atom clusters on a non-wetting substrate coated with rare-gas atoms.

  9. A numerical study of spin-dependent organization of alkali-metal atomic clusters using density-functional method

    Energy Technology Data Exchange (ETDEWEB)

    Liu Xuan, E-mail: liu.x.ad@m.titech.ac.jp; Ito, Haruhiko [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology (Japan); Torikai, Eiko [Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi (Japan)

    2012-08-15

    We calculate the different geometric isomers of spin clusters composed of a small number of alkali-metal atoms using the UB3LYP density-functional method. The electron density distribution of clusters changes according to the value of total spin. Steric structures as well as planar structures arise when the number of atoms increases. The lowest spin state is the most stable and Li{sub n}, Na{sub n}, K{sub n}, Rb{sub n}, and Cs{sub n} with n = 2-8 can be formed in higher spin states. In the highest spin state, the preparation of clusters depends on the kind and the number of constituent atoms. The interaction energy between alkali-metal atoms and rare-gas atoms is smaller than the binding energy of spin clusters. Consequently, it is possible to self-organize the alkali-metal-atom clusters on a non-wetting substrate coated with rare-gas atoms.

  10. Intraspecific density dependence and a guild of consumers coexisting on one resource.

    Science.gov (United States)

    McPeek, Mark A

    2012-12-01

    The importance of negative intraspecific density dependence to promoting species coexistence in a community is well accepted. However, such mechanisms are typically omitted from more explicit models of community dynamics. Here I analyze a variation of the Rosenzweig-MacArthur consumer-resource model that includes negative intraspecific density dependence for consumers to explore its effect on the coexistence of multiple consumers feeding on a single resource. This analysis demonstrates that a guild of multiple consumers can easily coexist on a single resource if each limits its own abundance to some degree, and stronger intraspecific density dependence permits a wider variety of consumers to coexist. The mechanism permitting multiple consumers to coexist works in a fashion similar to apparent competition or to each consumer having its own specialized predator. These results argue for a more explicit emphasis on how negative intraspecific density dependence is generated and how these mechanisms combine with species interactions to shape overall community structure.

  11. Durability of Low Platinum Fuel Cells Operating at High Power Density

    Energy Technology Data Exchange (ETDEWEB)

    Polevaya, Olga [Nuvera Fuel Cells Inc.; Blanchet, Scott [Nuvera Fuel Cells Inc.; Ahluwalia, Rajesh [Argonne National Lab; Borup, Rod [Los-Alamos National Lab; Mukundan, Rangachary [Los-Alamos National Lab

    2014-03-19

    Understanding and improving the durability of cost-competitive fuel cell stacks is imperative to successful deployment of the technology. Stacks will need to operate well beyond today’s state-of-the-art rated power density with very low platinum loading in order to achieve the cost targets set forth by DOE ($15/kW) and ultimately be competitive with incumbent technologies. An accelerated cost-reduction path presented by Nuvera focused on substantially increasing power density to address non-PGM material costs as well as platinum. The study developed a practical understanding of the degradation mechanisms impacting durability of fuel cells with low platinum loading (≤0.2mg/cm2) operating at high power density (≥1.0W/cm2) and worked out approaches for improving the durability of low-loaded, high-power stack designs. Of specific interest is the impact of combining low platinum loading with high power density operation, as this offers the best chance of achieving long-term cost targets. A design-of-experiments approach was utilized to reveal and quantify the sensitivity of durability-critical material properties to high current density at two levels of platinum loading (the more conventional 0.45 mgPt.cm–1 and the much lower 0.2 mgPt.cm–2) across several cell architectures. We studied the relevance of selected component accelerated stress tests (AST) to fuel cell operation in power producing mode. New stress tests (NST) were designed to investigate the sensitivity to the addition of electrical current on the ASTs, along with combined humidity and load cycles and, eventually, relate to the combined city/highway drive cycle. Changes in the cathode electrochemical surface area (ECSA) and average oxygen partial pressure on the catalyst layer with aging under AST and NST protocols were compared based on the number of completed cycles. Studies showed elevated sensitivity of Pt growth to the potential limits and the initial particle size distribution. The ECSA loss

  12. Recruitment of Mediator Complex by Cell Type and Stage-Specific Factors Required for Tissue-Specific TAF Dependent Gene Activation in an Adult Stem Cell Lineage.

    Directory of Open Access Journals (Sweden)

    Chenggang Lu

    2015-12-01

    Full Text Available Onset of terminal differentiation in adult stem cell lineages is commonly marked by robust activation of new transcriptional programs required to make the appropriate differentiated cell type(s. In the Drosophila male germ line stem cell lineage, the switch from proliferating spermatogonia to spermatocyte is accompanied by one of the most dramatic transcriptional changes in the fly, as over 1000 new transcripts turn on in preparation for meiosis and spermatid differentiation. Here we show that function of the coactivator complex Mediator is required for activation of hundreds of new transcripts in the spermatocyte program. Mediator appears to act in a sequential hierarchy, with the testis activating Complex (tMAC, a cell type specific form of the Mip/dREAM general repressor, required to recruit Mediator subunits to the chromatin, and Mediator function required to recruit the testis TAFs (tTAFs, spermatocyte specific homologs of subunits of TFIID. Mediator, tMAC and the tTAFs co-regulate expression of a major set of spermatid differentiation genes. The Mediator subunit Med22 binds the tMAC component Topi when the two are coexpressed in S2 cells, suggesting direct recruitment. Loss of Med22 function in spermatocytes causes meiosis I maturation arrest male infertility, similar to loss of function of the tMAC subunits or the tTAFs. Our results illuminate how cell type specific versions of the Mip/dREAM complex and the general transcription machinery cooperate to drive selective gene activation during differentiation in stem cell lineages.

  13. α-Tocopherol modulates the low density lipoprotein receptor of human HepG2 cells

    Directory of Open Access Journals (Sweden)

    Bottema Cynthia DK

    2003-05-01

    Full Text Available Abstract The aim of this study was to determine the effects of vitamin E (α-tocopherol on the low density lipoprotein (LDL receptor, a cell surface protein which plays an important role in controlling blood cholesterol. Human HepG2 hepatoma cells were incubated for 24 hours with increasing amounts of α, δ, or γ-tocopherol. The LDL receptor binding activity, protein and mRNA, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase mRNA, cell cholesterol and cell lathosterol were measured. The effect of α-tocopherol was biphasic. Up to a concentration of 50 μM, α-tocopherol progressively increased LDL receptor binding activity, protein and mRNA to maximum levels 2, 4 and 6-fold higher than control, respectively. The HMG-CoA reductase mRNA and the cell lathosterol concentration, indices of cholesterol synthesis, were also increased by 40% over control by treatment with 50 μM α-tocopherol. The cell cholesterol concentration was decreased by 20% compared to control at 50 μM α-tocopherol. However, at α-tocopherol concentrations higher than 50 μM, the LDL receptor binding activity, protein and mRNA, the HMG-CoA reductase mRNA and the cell lathosterol and cholesterol concentrations all returned to control levels. The biphasic effect on the LDL receptor was specific for α-tocopherol in that δ and γ-tocopherol suppressed LDL receptor binding activity, protein and mRNA at all concentrations tested despite the cells incorporating similar amounts of the three homologues. In conclusion, α-tocopherol, exhibits a specific, concentration-dependent and biphasic "up then down" effect on the LDL receptor of HepG2 cells which appears to be at the level of gene transcription. Cholesterol synthesis appears to be similarly affected and the cell cholesterol concentration may mediate these effects.

  14. Influence of anatomy and basic density on specific cutting force for wood from Corymbia citriodora Hill & Johnson

    Directory of Open Access Journals (Sweden)

    Luiz-E. de L. Melo

    2015-12-01

    Full Text Available Aim of the study: The aim of this study was to evaluate the influence of xylem tissue cell structure, determined through biometry and basic density of the wood from Corymbia citriodora Hill & Johnson on consumption of specific 90º-0º longitudinal cutting force.Area of study: The study area was in the region of the Vale do Rio Doce - Minas Gerais, Brazil.Material and methods: A diametrical board with dimensions of 60 x 18 x 5 cm (length x width x thickness, respectively, with more than 1.3 m from the ground, was removed. In machining trials, a 400 mm diameter circular saw was used, with 24 “WZ” teeth, feed rate of 10 m.min-1, cutting speed of 61 m.s-1, and maximum instantaneous torque of 92.5 N.m. During cutting, test specimens were removed with alternated and parallel 1.5 cm edges in 6 radial positions, which were used for biometric determination of cell structure and basic density.Main results: It was observed that wood basic density, vessel diameter, fiber wall thickness, fiber wall fraction and fiber wall portion were directly proportional to the specific cutting force. In contrast, vessel frequency and fiber lumen diameter proved to be inversely proportional to cutting force.Research highlights: This work provides important values of quantification of influence of xylem tissue cell structure, determined through biometry and physical properties of the wood that may be used to prediction of consumption of specific cutting force.Keywords: wood machining; wood properties; optimization of the process.

  15. BMP signaling regulates satellite cell-dependent postnatal muscle growth.

    Science.gov (United States)

    Stantzou, Amalia; Schirwis, Elija; Swist, Sandra; Alonso-Martin, Sonia; Polydorou, Ioanna; Zarrouki, Faouzi; Mouisel, Etienne; Beley, Cyriaque; Julien, Anaïs; Le Grand, Fabien; Garcia, Luis; Colnot, Céline; Birchmeier, Carmen; Braun, Thomas; Schuelke, Markus; Relaix, Frédéric; Amthor, Helge

    2017-08-01

    Postnatal growth of skeletal muscle largely depends on the expansion and differentiation of resident stem cells, the so-called satellite cells. Here, we demonstrate that postnatal satellite cells express components of the bone morphogenetic protein (BMP) signaling machinery. Overexpression of noggin in postnatal mice (to antagonize BMP ligands), satellite cell-specific knockout of Alk3 (the gene encoding the BMP transmembrane receptor) or overexpression of inhibitory SMAD6 decreased satellite cell proliferation and accretion during myofiber growth, and ultimately retarded muscle growth. Moreover, reduced BMP signaling diminished the adult satellite cell pool. Abrogation of BMP signaling in satellite cell-derived primary myoblasts strongly diminished cell proliferation and upregulated the expression of cell cycle inhibitors p21 and p57 In conclusion, these results show that BMP signaling defines postnatal muscle development by regulating satellite cell-dependent myofiber growth and the generation of the adult muscle stem cell pool. © 2017. Published by The Company of Biologists Ltd.

  16. The impact of new evidence on state-of-knowledge dependence

    International Nuclear Information System (INIS)

    Haim, M.; Apostolakis, G.

    1987-01-01

    When modeling a SOK (state-of-knowledge) dependence it is sometimes essential to apply a multivariate SOK distribution, e.g. when a new evidence is used to update a current assessment. As shown a SOK dependence may arise due to updating a prior distribution by dependent test-results. In two specific extreme cases SOK dependence (independence) cannot be influenced by updating the prior by new evidence: the case of identical units (a complete dependence), the case of independence (i.e., no SOK dependence) and evidence consists of conditionally independent test-results. (orig./HP)

  17. Dimethylfumarate attenuates restenosis after acute vascular injury by cell-specific and Nrf2-dependent mechanisms

    Directory of Open Access Journals (Sweden)

    Chang Joo Oh

    2014-01-01

    Full Text Available Excessive proliferation of vascular smooth muscle cells (VSMCs and incomplete re-endothelialization is a major clinical problem limiting the long-term efficacy of percutaneous coronary angioplasty. We tested if dimethylfumarate (DMF, an anti-psoriasis drug, could inhibit abnormal vascular remodeling via NF−E2-related factor 2 (Nrf2-NAD(PH quinone oxidoreductase 1 (NQO1 activity. DMF significantly attenuated neointimal hyperplasia induced by balloon injury in rat carotid arteries via suppression of the G1 to S phase transition resulting from induction of p21 protein in VSMCs. Initially, DMF increased p21 protein stability through an enhancement in Nrf2 activity without an increase in p21 mRNA. Later on, DMF stimulated p21 mRNA expression through a process dependent on p53 activity. However, heme oxygenase-1 (HO-1 or NQO1 activity, well-known target genes induced by Nrf2, were dispensable for the DMF induction of p21 protein and the effect on the VSMC proliferation. Likewise, DMF protected endothelial cells from TNF-α-induced apoptosis and the dysfunction characterized by decreased eNOS expression. With knock-down of Nrf2 or NQO1, DMF failed to prevent TNF-α-induced cell apoptosis and decreased eNOS expression. Also, CD31 expression, an endothelial specific marker, was restored in vivo by DMF. In conclusion, DMF prevented abnormal proliferation in VSMCs by G1 cell cycle arrest via p21 upregulation driven by Nrf2 and p53 activity, and had a beneficial effect on TNF-α-induced apoptosis and dysfunction in endothelial cells through Nrf2–NQO1 activity suggesting that DMF might be a therapeutic drug for patients with vascular disease.

  18. Density dependence of dielectronic recombination in selenium

    International Nuclear Information System (INIS)

    Hagelstein, P.L.; Rosen, M.D.; Jacobs, V.L.

    1986-01-01

    Dielectronic recombination has been found to be the dominant recombination process in the determination of the ionization balance of selenium near the Ne-like sequence under conditions relevant to the exploding-foil EUV laser plasmas. The dielectronic recombination process tends to populate excited levels, and these levels in turn are more susceptible to subsequent excitation and ionization than are the ground-state ions. If one defines an effective recombination rate which includes, in addition to the primary recombination, the subsequent excitation and ionization of the additional excited-state population due to the primary recombination, then this effective recombination rate can be density-sensitive at relatively low electron density. We present results for this effective dielectronic recombination rate at an electron density of 3 x 10/sup 20/ electrons/cm 3 for recombination from Ne-like to Na-like selenium and from F-like to Ne-like selenium. In the former case, the effective recombination rate coefficient is found to be 1.8 x 10/sup -11/ cm 3 /sec at 1.0 keV, which is to be compared with the zero-density value of 2.8 x 10/sup -11/ cm 3 /sec. In the latter case (F-like to Ne-like), the effective recombination rate coefficient is found to be 1.3 x 10/sup -11/ cm 3 /sec, which is substantially reduced from the zero-density result of 3.3 x 10/sup -11/ cm 3 /sec. We have examined the effects of dielectronic recombination on the laser gain of the dominant Ne-like 3p-3s transitions and have compared our results with those presented by Whitten et al. [Phys. Rev. A 33, 2171 (1986)

  19. Epigenetic regulation of normal human mammary cell type-specific miRNAs

    Energy Technology Data Exchange (ETDEWEB)

    Vrba, Lukas [Univ. of Arizona, Tucson, AZ (United States). Arizona Cancer Center; Inst. of Plant Molecular Biology, Ceske Budejovice (Czech Republic). Biology Centre ASCR; Garbe, James C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Life Sciences Center; Stampfer, Martha R. [Univ. of Arizona, Tucson, AZ (United States). Arizona Cancer Center; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Life Sciences Center; Futscher, Bernard W. [Univ. of Arizona, Tucson, AZ (United States). Arizona Cancer Center and Dept. of Pharmacology & Toxicology

    2011-08-26

    Epigenetic mechanisms are important regulators of cell type–specific genes, including miRNAs. In order to identify cell type-specific miRNAs regulated by epigenetic mechanisms, we undertook a global analysis of miRNA expression and epigenetic states in three isogenic pairs of human mammary epithelial cells (HMEC) and human mammary fibroblasts (HMF), which represent two differentiated cell types typically present within a given organ, each with a distinct phenotype and a distinct epigenotype. While miRNA expression and epigenetic states showed strong interindividual concordance within a given cell type, almost 10% of the expressed miRNA showed a cell type–specific pattern of expression that was linked to the epigenetic state of their promoter. The tissue-specific miRNA genes were epigenetically repressed in nonexpressing cells by DNA methylation (38%) and H3K27me3 (58%), with only a small set of miRNAs (21%) showing a dual epigenetic repression where both DNA methylation and H3K27me3 were present at their promoters, such as MIR10A and MIR10B. Individual miRNA clusters of closely related miRNA gene families can each display cell type–specific repression by the same or complementary epigenetic mechanisms, such as the MIR200 family, and MIR205, where fibroblasts repress MIR200C/141 by DNA methylation, MIR200A/200B/429 by H3K27me3, and MIR205 by both DNA methylation and H3K27me3. Since deregulation of many of the epigenetically regulated miRNAs that we identified have been linked to disease processes such as cancer, it is predicted that compromise of the epigenetic control mechanisms is important for this process. Overall, these results highlight the importance of epigenetic regulation in the control of normal cell type–specific miRNA expression.

  20. Volume-dependent K+ transport in rabbit red blood cells comparison with oxygenated human SS cells

    Energy Technology Data Exchange (ETDEWEB)

    Al-Rohil, N.; Jennings, M.L.

    1989-07-01

    In this study the volume-dependent or N-ethylmaleimide (NEM)-stimulated, ouabain-insensitive K+ influx and efflux were measured with the tracer 86Rb+ in rabbit red blood cells. The purpose of the work was to examine the rabbit as a potential model for cell volume regulation in human SS red blood cells and also to investigate the relationship between the NEM-reactive sulfhydryl group(s) and the signal by which cell swelling activates the transport. Ouabain-resistant K+ efflux and influx increase nearly threefold in cells swollen hypotonically by 15%. Pretreatment with 2 mM NEM stimulates efflux 5-fold and influx 10-fold (each measured in an isotonic medium). The ouabain-resistant K+ efflux was dependent on the major anion in the medium. The anion dependence of K+ efflux in swollen or NEM-stimulated cells was as follows: Br- greater than Cl- much greater than NO3- = acetate. The magnitudes of both the swelling- and the NEM-stimulated fluxes are much higher in young cells (density separated but excluding reticulocytes) than in older cells. Swelling- or NEM-stimulated K+ efflux in rabbit red blood cells was inhibited 50% by 1 mM furosemide, and the inhibitory potency of furosemide was enhanced by extracellular K+, as is known to be true for human AA and low-K+ sheep red blood cells. The swelling-stimulated flux in both rabbit and human SS cells has a pH optimum at approximately 7.4. We conclude that rabbit red blood cells are a good model for swelling-stimulated K+ transport in human SS cells.

  1. Calculation of the structural properties of a strange quark star in the presence of a strong magnetic field using a density dependent bag constant

    Institute of Scientific and Technical Information of China (English)

    Gholam Hossein Bordbar; Hajar Bahri; Fatemeh Kayanikhoo

    2012-01-01

    We have calculated the structural properties of a strange quark star with a static model in the presence of a strong magnetic field.To this end,we use the MITbag model with a density dependent bag constant.To parameterize the density dependence of the bag constant,we have used our results for the lowest order constrained variational calculation of the asymmetric nuclear matter.By calculating the equation of state of strange quark matter,we have shown that the pressure of this system increases by increasing both density and magnetic field.Finally,we have investigated the effect of density dependence of the bag constant on the structural properties of a strange quark star.

  2. Effects of matrix elasticity and cell density on human mesenchymal stem cells differentiation.

    Science.gov (United States)

    Xue, Ruyue; Li, Julie Yi-Shuan; Yeh, Yiting; Yang, Li; Chien, Shu

    2013-09-01

    Human mesenchymal stem cells (hMSCs) can differentiate into various cell types, including osteogenic and chondrogenic cells. The matrix elasticity and cell seeding density are important factors in hMSCs differentiation. We cultured hMSCs at different seeding densities on polyacrylamide hydrogels with different stiffness corresponding to Young's moduli of 1.6 ± 0.3 and 40 ± 3.6 kPa. The promotion of osteogenic marker expression by hard gel is overridden by a high seeding density. Cell seeding density, however, did not influence the chondrogenic marker expressions induced by soft gel. These findings suggest that interplays between cell-matrix and cell-cell interactions contribute to hMSCs differentiation. The promotion of osteogenic differentiation on hard matrix was shown to be mediated through the Ras pathway. Inhibition of Ras (RasN17) significantly decreased ERK, Smad1/5/8 and AKT activation, and osteogenic markers expression. However, constitutively active Ras (RasV12) had little effect on osteogenic marker expression, suggesting that the Ras pathways are necessary but not sufficient for osteogenesis. Taken together, our results indicate that matrix elasticity and cell density are important microenvironmental cues driving hMSCs proliferation and differentiation. Copyright © 2013 Orthopaedic Research Society.

  3. Postnatal development of depth-dependent collagen density in ovine articular cartilage

    Directory of Open Access Journals (Sweden)

    Kranenbarg Sander

    2010-10-01

    Full Text Available Abstract Background Articular cartilage (AC is the layer of tissue that covers the articulating ends of the bones in diarthrodial joints. Adult AC is characterised by a depth-dependent composition and structure of the extracellular matrix that results in depth-dependent mechanical properties, important for the functions of adult AC. Collagen is the most abundant solid component and it affects the mechanical behaviour of AC. The current objective is to quantify the postnatal development of depth-dependent collagen density in sheep (Ovis aries AC between birth and maturity. We use Fourier transform infra-red micro-spectroscopy to investigate collagen density in 48 sheep divided over ten sample points between birth (stillborn and maturity (72 weeks. In each animal, we investigate six anatomical sites (caudal, distal and rostral locations at the medial and lateral side of the joint in the distal metacarpus of a fore leg and a hind leg. Results Collagen density increases from birth to maturity up to our last sample point (72 weeks. Collagen density increases at the articular surface from 0.23 g/ml ± 0.06 g/ml (mean ± s.d., n = 48 at 0 weeks to 0.51 g/ml ± 0.10 g/ml (n = 46 at 72 weeks. Maximum collagen density in the deeper cartilage increases from 0.39 g/ml ± 0.08 g/ml (n = 48 at 0 weeks to 0.91 g/ml ± 0.13 g/ml (n = 46 at 72 weeks. Most collagen density profiles at 0 weeks (85% show a valley, indicating a minimum, in collagen density near the articular surface. At 72 weeks, only 17% of the collagen density profiles show a valley in collagen density near the articular surface. The fraction of profiles with this valley stabilises at 36 weeks. Conclusions Collagen density in articular cartilage increases in postnatal life with depth-dependent variation, and does not stabilize up to 72 weeks, the last sample point in our study. We find strong evidence for a valley in collagen densities near the articular surface that is present in the youngest

  4. Cortical cell and neuron density estimates in one chimpanzee hemisphere.

    Science.gov (United States)

    Collins, Christine E; Turner, Emily C; Sawyer, Eva Kille; Reed, Jamie L; Young, Nicole A; Flaherty, David K; Kaas, Jon H

    2016-01-19

    The density of cells and neurons in the neocortex of many mammals varies across cortical areas and regions. This variability is, perhaps, most pronounced in primates. Nonuniformity in the composition of cortex suggests regions of the cortex have different specializations. Specifically, regions with densely packed neurons contain smaller neurons that are activated by relatively few inputs, thereby preserving information, whereas regions that are less densely packed have larger neurons that have more integrative functions. Here we present the numbers of cells and neurons for 742 discrete locations across the neocortex in a chimpanzee. Using isotropic fractionation and flow fractionation methods for cell and neuron counts, we estimate that neocortex of one hemisphere contains 9.5 billion cells and 3.7 billion neurons. Primary visual cortex occupies 35 cm(2) of surface, 10% of the total, and contains 737 million densely packed neurons, 20% of the total neurons contained within the hemisphere. Other areas of high neuron packing include secondary visual areas, somatosensory cortex, and prefrontal granular cortex. Areas of low levels of neuron packing density include motor and premotor cortex. These values reflect those obtained from more limited samples of cortex in humans and other primates.

  5. Tuning the Density of Poly(ethylene glycol Chains to Control Mammalian Cell and Bacterial Attachment

    Directory of Open Access Journals (Sweden)

    Ahmed Al-Ani

    2017-08-01

    Full Text Available Surface modification of biomaterials with polymer chains has attracted great attention because of their ability to control biointerfacial interactions such as protein adsorption, cell attachment and bacterial biofilm formation. The aim of this study was to control the immobilisation of biomolecules on silicon wafers using poly(ethylene glycol(PEG chains by a “grafting to” technique. In particular, to control the polymer chain graft density in order to capture proteins and preserve their activity in cell culture as well as find the optimal density that would totally prevent bacterial attachment. The PEG graft density was varied by changing the polymer solubility using an increasing salt concentration. The silicon substrates were initially modified with aminopropyl-triethoxysilane (APTES, where the surface density of amine groups was optimised using different concentrations. The results showed under specific conditions, the PEG density was highest with grafting under “cloud point” conditions. The modified surfaces were characterised with X-ray photoelectron spectroscopy (XPS, ellipsometry, atomic force microscopy (AFM and water contact angle measurements. In addition, all modified surfaces were tested with protein solutions and in cell (mesenchymal stem cells and MG63 osteoblast-like cells and bacterial (Pseudomonas aeruginosa attachment assays. Overall, the lowest protein adsorption was observed on the highest polymer graft density, bacterial adhesion was very low on all modified surfaces, and it can be seen that the attachment of mammalian cells gradually increased as the PEG grafting density decreased, reaching the maximum attachment at medium PEG densities. The results demonstrate that, at certain PEG surface coverages, mammalian cell attachment can be tuned with the potential to optimise their behaviour with controlled serum protein adsorption.

  6. Modelling interactions of toxicants and density dependence in wildlife populations

    Science.gov (United States)

    Schipper, Aafke M.; Hendriks, Harrie W.M.; Kauffman, Matthew J.; Hendriks, A. Jan; Huijbregts, Mark A.J.

    2013-01-01

    1. A major challenge in the conservation of threatened and endangered species is to predict population decline and design appropriate recovery measures. However, anthropogenic impacts on wildlife populations are notoriously difficult to predict due to potentially nonlinear responses and interactions with natural ecological processes like density dependence. 2. Here, we incorporated both density dependence and anthropogenic stressors in a stage-based matrix population model and parameterized it for a density-dependent population of peregrine falcons Falco peregrinus exposed to two anthropogenic toxicants [dichlorodiphenyldichloroethylene (DDE) and polybrominated diphenyl ethers (PBDEs)]. Log-logistic exposure–response relationships were used to translate toxicant concentrations in peregrine falcon eggs to effects on fecundity. Density dependence was modelled as the probability of a nonbreeding bird acquiring a breeding territory as a function of the current number of breeders. 3. The equilibrium size of the population, as represented by the number of breeders, responded nonlinearly to increasing toxicant concentrations, showing a gradual decrease followed by a relatively steep decline. Initially, toxicant-induced reductions in population size were mitigated by an alleviation of the density limitation, that is, an increasing probability of territory acquisition. Once population density was no longer limiting, the toxicant impacts were no longer buffered by an increasing proportion of nonbreeders shifting to the breeding stage, resulting in a strong decrease in the equilibrium number of breeders. 4. Median critical exposure concentrations, that is, median toxicant concentrations in eggs corresponding with an equilibrium population size of zero, were 33 and 46 μg g−1 fresh weight for DDE and PBDEs, respectively. 5. Synthesis and applications. Our modelling results showed that particular life stages of a density-limited population may be relatively insensitive to

  7. The local density of optical states of a metasurface

    Science.gov (United States)

    Lunnemann, Per; Koenderink, A. Femius

    2016-02-01

    While metamaterials are often desirable for near-field functions, such as perfect lensing, or cloaking, they are often quantified by their response to plane waves from the far field. Here, we present a theoretical analysis of the local density of states near lattices of discrete magnetic scatterers, i.e., the response to near field excitation by a point source. Based on a pointdipole theory using Ewald summation and an array scanning method, we can swiftly and semi-analytically evaluate the local density of states (LDOS) for magnetoelectric point sources in front of an infinite two-dimensional (2D) lattice composed of arbitrary magnetoelectric dipole scatterers. The method takes into account radiation damping as well as all retarded electrodynamic interactions in a self-consistent manner. We show that a lattice of magnetic scatterers evidences characteristic Drexhage oscillations. However, the oscillations are phase shifted relative to the electrically scattering lattice consistent with the difference expected for reflection off homogeneous magnetic respectively electric mirrors. Furthermore, we identify in which source-surface separation regimes the metasurface may be treated as a homogeneous interface, and in which homogenization fails. A strong frequency and in-plane position dependence of the LDOS close to the lattice reveals coupling to guided modes supported by the lattice.

  8. Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus.

    Directory of Open Access Journals (Sweden)

    D T Tyler Flockhart

    Full Text Available A central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the breeding season. We used laboratory experiments to measure the strength of density-dependent intraspecific competition on egg laying rate and larval survival and then applied our results to density estimates of wild monarch populations to model the strength of density dependence during the breeding season. Egg laying rates did not change with density but larvae at high densities were smaller, had lower survival, and weighed less as adults compared to lower densities. Using mean larval densities from field surveys resulted in conservative estimates of density-dependent population reduction that varied between breeding regions and different phases of the breeding season. Our results suggest the highest levels of population reduction due to density-dependent intraspecific competition occur early in the breeding season in the southern portion of the breeding range. However, we also found that the strength of density dependence could be almost five times higher depending on how many life-stages were used as part of field estimates. Our study is the first to link experimental results of a density-dependent reduction in vital rates to observed monarch densities in the wild and show that the effects of density dependent competition in monarchs varies across space and time, providing valuable information for developing robust, year-round population models in this migratory organism.

  9. A density-dependent switch drives stochastic clustering and polarization of signaling molecules.

    Directory of Open Access Journals (Sweden)

    Alexandra Jilkine

    2011-11-01

    Full Text Available Positive feedback plays a key role in the ability of signaling molecules to form highly localized clusters in the membrane or cytosol of cells. Such clustering can occur in the absence of localizing mechanisms such as pre-existing spatial cues, diffusional barriers, or molecular cross-linking. What prevents positive feedback from amplifying inevitable biological noise when an un-clustered "off" state is desired? And, what limits the spread of clusters when an "on" state is desired? Here, we show that a minimal positive feedback circuit provides the general principle for both suppressing and amplifying noise: below a critical density of signaling molecules, clustering switches off; above this threshold, highly localized clusters are recurrently generated. Clustering occurs only in the stochastic regime, suggesting that finite sizes of molecular populations cannot be ignored in signal transduction networks. The emergence of a dominant cluster for finite numbers of molecules is partly a phenomenon of random sampling, analogous to the fixation or loss of neutral mutations in finite populations. We refer to our model as the "neutral drift polarity model." Regulating the density of signaling molecules provides a simple mechanism for a positive feedback circuit to robustly switch between clustered and un-clustered states. The intrinsic ability of positive feedback both to create and suppress clustering is a general mechanism that could operate within diverse biological networks to create dynamic spatial organization.

  10. Cell-type-dependent action potentials and voltage-gated currents in mouse fungiform taste buds.

    Science.gov (United States)

    Kimura, Kenji; Ohtubo, Yoshitaka; Tateno, Katsumi; Takeuchi, Keita; Kumazawa, Takashi; Yoshii, Kiyonori

    2014-01-01

    Taste receptor cells fire action potentials in response to taste substances to trigger non-exocytotic neurotransmitter release in type II cells and exocytotic release in type III cells. We investigated possible differences between these action potentials fired by mouse taste receptor cells using in situ whole-cell recordings, and subsequently we identified their cell types immunologically with cell-type markers, an IP3 receptor (IP3 R3) for type II cells and a SNARE protein (SNAP-25) for type III cells. Cells not immunoreactive to these antibodies were examined as non-IRCs. Here, we show that type II cells and type III cells fire action potentials using different ionic mechanisms, and that non-IRCs also fire action potentials with either of the ionic mechanisms. The width of action potentials was significantly narrower and their afterhyperpolarization was deeper in type III cells than in type II cells. Na(+) current density was similar in type II cells and type III cells, but it was significantly smaller in non-IRCs than in the others. Although outwardly rectifying current density was similar between type II cells and type III cells, tetraethylammonium (TEA) preferentially suppressed the density in type III cells and the majority of non-IRCs. Our mathematical model revealed that the shape of action potentials depended on the ratio of TEA-sensitive current density and TEA-insensitive current one. The action potentials of type II cells and type III cells under physiological conditions are discussed. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  11. Effect of culture density on biomass production and light utilization efficiency of Synechocystis sp. PCC 6803.

    Science.gov (United States)

    Straka, Levi; Rittmann, Bruce E

    2018-02-01

    The viability of large-scale microalgae cultivation depends on providing optimal growth conditions, for which a key operational parameter is culture density. Using Synechocystis sp. PCC 6803, we conducted a series of fixed-density, steady-state experiments and one batch-growth experiment to investigate the role of culture density on biomass production and light utilization efficiency. In all cases, the fixed-density, steady-state experiments and batch-growth experiment showed good agreement. The highest biomass production rates (260 mg L -1  d -1 ) and efficiency for converting light energy to biomass (0.80 μg (μmol photons) -1 ) occurred together at a culture density near 760 mg L -1 , which approximately corresponded to the lowest culture density where almost all incident light was absorbed. The ratio of OD 680 /OD 735 increased with culture density up to the point of maximum productivity, where it plateaued (at a value of 2.4) for higher culture densities. This change in OD 680 /OD 735 indicates a photoacclimation effect that depended on culture density. Very high culture densities led to a sharp decline in efficiency of biomass production per photons absorbed, likely due to a combination of increased decay relative to growth, metabolic changes due to cell-cell interactions, and photodamage due to mixing between regions with high light intensity and zero light intensity. © 2017 Wiley Periodicals, Inc.

  12. Density-dependent selection on mate search and evolution of Allee effects.

    Science.gov (United States)

    Berec, Luděk; Kramer, Andrew M; Bernhauerová, Veronika; Drake, John M

    2018-01-01

    Sexually reproducing organisms require males and females to find each other. Increased difficulty of females finding mates as male density declines is the most frequently reported mechanism of Allee effects in animals. Evolving more effective mate search may alleviate Allee effects, but may depend on density regimes a population experiences. In particular, high-density populations may evolve mechanisms that induce Allee effects which become detrimental when populations are reduced and maintained at a low density. We develop an individual-based, eco-genetic model to study how mating systems and fitness trade-offs interact with changes in population density to drive evolution of the rate at which males or females search for mates. Finite mate search rate triggers Allee effects in our model and we explore how these Allee effects respond to such evolution. We allow a population to adapt to several population density regimes and examine whether high-density populations are likely to reverse adaptations attained at low densities. We find density-dependent selection in most of scenarios, leading to search rates that result in lower Allee thresholds in populations kept at lower densities. This mainly occurs when fecundity costs are imposed on mate search, and provides an explanation for why Allee effects are often observed in anthropogenically rare species. Optimizing selection, where the attained trait value minimizes the Allee threshold independent of population density, depended on the trade-off between search and survival, combined with monogamy when females were searching. Other scenarios led to runaway selection on the mate search rate, including evolutionary suicide. Trade-offs involved in mate search may thus be crucial to determining how density influences the evolution of Allee effects. Previous studies did not examine evolution of a trait related to the strength of Allee effects under density variation. We emphasize the crucial role that mating systems, fitness

  13. AMPK governs lineage specification through Tfeb-dependent regulation of lysosomes.

    Science.gov (United States)

    Young, Nathan P; Kamireddy, Anwesh; Van Nostrand, Jeanine L; Eichner, Lillian J; Shokhirev, Maxim Nikolaievich; Dayn, Yelena; Shaw, Reuben J

    2016-03-01

    Faithful execution of developmental programs relies on the acquisition of unique cell identities from pluripotent progenitors, a process governed by combinatorial inputs from numerous signaling cascades that ultimately dictate lineage-specific transcriptional outputs. Despite growing evidence that metabolism is integrated with many molecular networks, how pathways that control energy homeostasis may affect cell fate decisions is largely unknown. Here, we show that AMP-activated protein kinase (AMPK), a central metabolic regulator, plays critical roles in lineage specification. Although AMPK-deficient embryonic stem cells (ESCs) were normal in the pluripotent state, these cells displayed profound defects upon differentiation, failing to generate chimeric embryos and preferentially adopting an ectodermal fate at the expense of the endoderm during embryoid body (EB) formation. AMPK(-/-) EBs exhibited reduced levels of Tfeb, a master transcriptional regulator of lysosomes, leading to diminished endolysosomal function. Remarkably, genetic loss of Tfeb also yielded endodermal defects, while AMPK-null ESCs overexpressing this transcription factor normalized their differential potential, revealing an intimate connection between Tfeb/lysosomes and germ layer specification. The compromised endolysosomal system resulting from AMPK or Tfeb inactivation blunted Wnt signaling, while up-regulating this pathway restored expression of endodermal markers. Collectively, these results uncover the AMPK pathway as a novel regulator of cell fate determination during differentiation. © 2016 Young et al.; Published by Cold Spring Harbor Laboratory Press.

  14. Acetylation-Dependent Chromatin Reorganization by BRDT, a Testis-Specific Bromodomain-Containing Protein

    Science.gov (United States)

    Pivot-Pajot, Christophe; Caron, Cécile; Govin, Jérôme; Vion, Alexandre; Rousseaux, Sophie; Khochbin, Saadi

    2003-01-01

    The association between histone acetylation and replacement observed during spermatogenesis prompted us to consider the testis as a source for potential factors capable of remodelling acetylated chromatin. A systematic search of data banks for open reading frames encoding testis-specific bromodomain-containing proteins focused our attention on BRDT, a testis-specific protein of unknown function containing two bromodomains. BRDT specifically binds hyperacetylated histone H4 tail depending on the integrity of both bromodomains. Moreover, in somatic cells, the ectopic expression of BRDT triggered a dramatic reorganization of the chromatin only after induction of histone hyperacetylation by trichostatin A (TSA). We then defined critical domains of BRDT involved in its activity. Both bromodomains of BRDT, as well as flanking regions, were found indispensable for its histone acetylation-dependent remodelling activity. Interestingly, we also observed that recombinant BRDT was capable of inducing reorganization of the chromatin of isolated nuclei in vitro only when the nuclei were from TSA-treated cells. This assay also allowed us to show that the action of BRDT was ATP independent, suggesting a structural role for the protein in the remodelling of acetylated chromatin. This is the first demonstration of a large-scale reorganization of acetylated chromatin induced by a specific factor. PMID:12861021

  15. Secondary immunization generates clonally related antigen-specific plasma cells and memory B cells.

    Science.gov (United States)

    Frölich, Daniela; Giesecke, Claudia; Mei, Henrik E; Reiter, Karin; Daridon, Capucine; Lipsky, Peter E; Dörner, Thomas

    2010-09-01

    Rechallenge with T cell-dependent Ags induces memory B cells to re-enter germinal centers (GCs) and undergo further expansion and differentiation into plasma cells (PCs) and secondary memory B cells. It is currently not known whether the expanded population of memory B cells and PCs generated in secondary GCs are clonally related, nor has the extent of proliferation and somatic hypermutation of their precursors been delineated. In this study, after secondary tetanus toxoid (TT) immunization, TT-specific PCs increased 17- to 80-fold on days 6-7, whereas TT-specific memory B cells peaked (delayed) on day 14 with a 2- to 22-fold increase. Molecular analyses of V(H)DJ(H) rearrangements of individual cells revealed no major differences of gene usage and CDR3 length between TT-specific PCs and memory B cells, and both contained extensive evidence of somatic hypermutation with a pattern consistent with GC reactions. This analysis identified clonally related TT-specific memory B cells and PCs. Within clusters of clonally related cells, sequences shared a number of mutations but also could contain additional base pair changes. The data indicate that although following secondary immunization PCs can derive from memory B cells without further somatic hypermutation, in some circumstances, likely within GC reactions, asymmetric mutation can occur. These results suggest that after the fate decision to differentiate into secondary memory B cells or PCs, some committed precursors continue to proliferate and mutate their V(H) genes.

  16. Effect of state-dependent delay on a weakly damped nonlinear oscillator.

    Science.gov (United States)

    Mitchell, Jonathan L; Carr, Thomas W

    2011-04-01

    We consider a weakly damped nonlinear oscillator with state-dependent delay, which has applications in models for lasers, epidemics, and microparasites. More generally, the delay-differential equations considered are a predator-prey system where the delayed term is linear and represents the proliferation of the predator. We determine the critical value of the delay that causes the steady state to become unstable to periodic oscillations via a Hopf bifurcation. Using asymptotic averaging, we determine how the system's behavior is influenced by the functional form of the state-dependent delay. Specifically, we determine whether the branch of periodic solutions will be either sub- or supercritical as well as an accurate estimation of the amplitude. Finally, we choose a few examples of state-dependent delay to test our analytical results by comparing them to numerical continuation.

  17. Multi-temperature state-dependent equivalent circuit discharge model for lithium-sulfur batteries

    DEFF Research Database (Denmark)

    Propp, Karsten; Marinescu, Monica; Auger, Daniel J.

    2016-01-01

    Lithium-sulfur (Li-S) batteries are described extensively in the literature, but existing computational models aimed at scientific understanding are too complex for use in applications such as battery management. Computationally simple models are vital for exploitation. This paper proposes a non......-linear state-of-charge dependent Li-S equivalent circuit network (ECN) model for a Li-S cell under discharge. Li-S batteries are fundamentally different to Li-ion batteries, and require chemistry-specific models. A new Li-S model is obtained using a ‘behavioural’ interpretation of the ECN model; as Li...... pulse profile at four temperatures from 10 °C to 50 °C, giving linearized ECN parameters for a range of states-of-charge, currents and temperatures. These are used to create a nonlinear polynomial-based battery model suitable for use in a battery management system. When the model is used to predict...

  18. Angular dependences of the luminescence and density of photon states in a chiral liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Umanskii, B A; Blinov, L M; Palto, S P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation)

    2013-11-30

    Luminescence spectra of a laser dye-doped chiral liquid crystal have been studied in a wide range of angles (up to 60°) to the axis of its helical structure using a semicylindrical quartz prism, which made it possible to observe the shift and evolution of the photonic band gap in response to changes in angle. Using measured spectra and numerical simulation, we calculated the spectral distributions of the density of photon states in such a cholesteric crystal for polarised and unpolarised light, which characterise its structure as that of a chiral one-dimensional photonic crystal. (optics of liquid crystals)

  19. Density Dependence and Growth Rate: Evolutionary Effects on Resistance Development to Bt (Bacillus thuringiensis).

    Science.gov (United States)

    Martinez, Jeannette C; Caprio, Michael A; Friedenberg, Nicholas A

    2018-02-09

    It has long been recognized that pest population dynamics can affect the durability of a pesticide, but dose remains the primary component of insect resistance management (IRM). For transgenic pesticidal traits such as Bt (Bacillus thuringiensis Berliner (Bacillales: Bacillaceae)), dose (measured as the mortality of susceptibles caused by a toxin) is a relatively fixed characteristic and often falls below the standard definition of high dose. Hence, it is important to understand how pest population dynamics modify durability and what targets they present for IRM. We used a deterministic model of a generic arthropod pest to examine how timing and strength of density dependence interacted with population growth rate and Bt mortality to affect time to resistance. As in previous studies, durability typically reached a minimum at intermediate doses. However, high population growth rates could eliminate benefits of high dose. The timing of density dependence had a more subtle effect. If density dependence operated simultaneously with Bt mortality, durability was insensitive to its strengths. However, if density dependence was driven by postselection densities, decreasing its strength could increase durability. The strength of density dependence could affect durability of both single traits and pyramids, but its influence depended on the timing of density dependence and size of the refuge. Our findings suggest the utility of a broader definition of high dose, one that incorporates population-dynamic context. That maximum growth rates and timing and strength of interactions causing density dependent mortality can all affect durability, also highlights the need for ecologically integrated approaches to IRM research. © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. Pulse frequency dependency of photobiomodulation on the bioenergetic functions of human dental pulp stem cells.

    Science.gov (United States)

    Kim, Hong Bae; Baik, Ku Youn; Choung, Pill-Hoon; Chung, Jong Hoon

    2017-11-21

    Photobiomodulation (PBM) therapy contributes to pain relief, wound healing, and tissue regeneration. The pulsed wave (PW) mode has been reported to be more effective than the continuous wave (CW) mode when applying PBM to many biological systems. However, the reason for the higher effectiveness of PW-PBM is poorly understood. Herein, we suggest using delayed luminescence (DL) as a reporter of mitochondrial activity after PBM treatment. DL originates mainly from mitochondrial electron transport chain systems, which produce reactive oxygen species (ROS) and adenosine triphosphate (ATP). The decay time of DL depends on the pulse frequencies of applied light, which correlate with the biological responses of human dental pulp stem cells (hDPSCs). Using a low-power light whose wavelength is 810 nm and energy density is 38 mJ/cm 2 , we find that a 300-Hz pulse frequency prolonged the DL pattern and enhanced alkaline phosphatase activity. In addition, we analyze mitochondrial morphological changes and their volume density and find evidence supporting mitochondrial physiological changes from PBM treatment. Our data suggest a new methodology for determining the effectiveness of PBM and the specific pulse frequency dependency of PBM in the differentiation of hDPSCs.

  1. Density matrix-based time-dependent configuration interaction approach to ultrafast spin-flip dynamics

    Science.gov (United States)

    Wang, Huihui; Bokarev, Sergey I.; Aziz, Saadullah G.; Kühn, Oliver

    2017-08-01

    Recent developments in attosecond spectroscopy yield access to the correlated motion of electrons on their intrinsic timescales. Spin-flip dynamics is usually considered in the context of valence electronic states, where spin-orbit coupling is weak and processes related to the electron spin are usually driven by nuclear motion. However, for core-excited states, where the core-hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter timescale. Using density matrix-based time-dependent restricted active space configuration interaction including spin-orbit coupling, we address an unprecedentedly short spin-crossover for the example of L-edge (2p→3d) excited states of a prototypical Fe(II) complex. This process occurs on a timescale, which is faster than that of Auger decay (∼4 fs) treated here explicitly. Modest variations of carrier frequency and pulse duration can lead to substantial changes in the spin-state yield, suggesting its control by soft X-ray light.

  2. Rapid and selective expansion of nonclonotypic T cells in regulatory T cell-deficient, foreign antigen-specific TCR-transgenic scurfy mice: antigen-dependent expansion and TCR analysis.

    Science.gov (United States)

    Sharma, Rahul; Ju, Angela Chiao-Ying; Kung, John T; Fu, Shu Man; Ju, Shyr-Te

    2008-11-15

    Foreign Ag-specific TCR-transgenic (Tg) mice contain a small fraction of T cells bearing the endogenous Vbeta and Valpha chains as well as a population expressing an intermediate level of Tg TCR. Importantly, these minor nonclonotypic populations contain > or = 99% of the CD4(+)Foxp3(+) regulatory T cells (Treg) and, despite low overall Treg expression, peripheral tolerance is maintained. In the OT-II TCR (OVA-specific, Vbeta5(high)Valpha2(high)) Tg scurfy (Sf) mice (OT-II Sf) that lack Treg, nonclonotypic T cells markedly expanded in the periphery but not in the thymus. Expanded T cells expressed memory/effector phenotype and were enriched in blood and inflamed lungs. In contrast, Vbeta5(high)Valpha2(high) clonotypic T cells were not expanded, displayed the naive phenotype, and found mainly in the lymph nodes. Importantly, Vbeta5(neg) T cells were able to transfer multiorgan inflammation in Rag1(-/-) recipients. T cells bearing dual TCR (dual Vbeta or dual Valpha) were demonstrated frequently in the Vbeta5(int) and Valpha2(int) populations. Our study demonstrated that in the absence of Treg, the lack of peripheral expansion of clonotypic T cells is due to the absence of its high-affinity Ag OVA. Thus, the rapid expansion of nonclonotypic T cells in OT-II Sf mice must require Ag (self and foreign) with sufficient affinity. Our study has implications with respect to the roles of Ag and dual TCR in the selection and regulation of Treg and Treg-controlled Ag-dependent T cell expansion in TCR Tg and TCR Tg Sf mice, respectively.

  3. Activation of nickel-specific CD4+ T lymphocytes in the absence of professional antigen-presenting cells.

    Science.gov (United States)

    Nasorri, Francesca; Sebastiani, Silvia; Mariani, Valentina; De Pità, Ornella; Puddu, Pietro; Girolomoni, Giampiero; Cavani, Andrea

    2002-01-01

    Allergic contact dermatitis ensues from exaggerated T cell responses to haptens. Dendritic cells are required for the initiation of hapten sensitization, but they may not be necessary for disease expression. Here we investigated the antigen-presenting cell requirement of nickel-specific CD4+ lymphocytes isolated from the blood of six allergic individuals. A significant proportion (42 out of 121; 35%) of the T cell clones proliferated in vitro to nickel also in the absence of professional antigen-presenting cells, suggesting a direct T-T hapten presentation. Antigen-presenting-cell-independent T cells showed a predominant T helper 1 phenotype. Nickel recognition by these T cells was major histocompatibility complex class II restricted, not influenced by CD28 triggering, independent from their state of activation, and did not require processing. The capacity of this T cell subset to be directly stimulated by nickel was not due to unique antigen-presenting properties, as both antigen-presenting-cell-dependent and antigen-presenting-cell-independent clones displayed comparable levels of HLA-DR, CD80, and CD86, and were equally capable of presenting nickel to antigen-presenting-cell-independent clones. In contrast, neither T cell types activated antigen-presenting-cell-dependent T lymphocytes. T-T presentation induced T cell receptor downregulation, CD25, CD80, CD86, and HLA-DR upregulation, and interferon-gamma release, although to a lesser extent compared to those induced by dendritic cell-T presentation. Following T-T presentation, the clones did not undergo unresponsiveness and maintained the capacity to respond to dendritic cells pulsed with antigen. In aggregate, our data suggest that antigen-presenting-cell-independent T cell activation can effectively amplify hapten- specific immune responses.

  4. An atomic orbital based real-time time-dependent density functional theory for computing electronic circular dichroism band spectra

    Energy Technology Data Exchange (ETDEWEB)

    Goings, Joshua J.; Li, Xiaosong, E-mail: xsli@uw.edu [Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States)

    2016-06-21

    One of the challenges of interpreting electronic circular dichroism (ECD) band spectra is that different states may have different rotatory strength signs, determined by their absolute configuration. If the states are closely spaced and opposite in sign, observed transitions may be washed out by nearby states, unlike absorption spectra where transitions are always positive additive. To accurately compute ECD bands, it is necessary to compute a large number of excited states, which may be prohibitively costly if one uses the linear-response time-dependent density functional theory (TDDFT) framework. Here we implement a real-time, atomic-orbital based TDDFT method for computing the entire ECD spectrum simultaneously. The method is advantageous for large systems with a high density of states. In contrast to previous implementations based on real-space grids, the method is variational, independent of nuclear orientation, and does not rely on pseudopotential approximations, making it suitable for computation of chiroptical properties well into the X-ray regime.

  5. The Impact of HLA Class I-Specific Killer Cell Immunoglobulin-Like Receptors on Antibody-Dependent Natural Killer Cell-Mediated Cytotoxicity and Organ Allograft Rejection.

    Science.gov (United States)

    Rajalingam, Raja

    2016-01-01

    Natural killer (NK) cells of the innate immune system are cytotoxic lymphocytes that play an important roles following transplantation of solid organs and hematopoietic stem cells. Recognition of self-human leukocyte antigen (HLA) class I molecules by inhibitory killer cell immunoglobulin-like receptors (KIRs) is involved in the calibration of NK cell effector capacities during the developmental stage, allowing the subsequent recognition and elimination of target cells with decreased expression of self-HLA class I (due to virus infection or tumor transformation) or HLA class I disparities (in the setting of allogeneic transplantation). NK cells expressing an inhibitory KIR-binding self-HLA can be activated when confronted with allografts lacking a ligand for the inhibitory receptor. Following the response of the adaptive immune system, NK cells can further destroy allograft endothelium by antibody-dependent cell-mediated cytotoxicity (ADCC), triggered through cross-linking of the CD16 Fc receptor by donor-specific antibodies bound to allograft. Upon recognizing allogeneic target cells, NK cells also secrete cytokines and chemokines that drive maturation of dendritic cells to promote cellular and humoral adaptive immune responses against the allograft. The cumulative activating and inhibitory signals generated by ligation of the receptors regulates mature NK cell killing of target cells and their production of cytokines and chemokines. This review summarizes the role of NK cells in allograft rejection and proposes mechanistic concepts that indicate a prominent role for KIR-HLA interactions in facilitating NK cells for Fc receptor-mediated ADCC effector function involved in antibody-mediated rejection of solid organ transplants.

  6. The impact of HLA class I-specific killer cell immunoglobulin-like receptors on antibody-dependent natural killer cell-mediated cytotoxicity and organ allograft rejection

    Directory of Open Access Journals (Sweden)

    Raja Rajalingam

    2016-12-01

    Full Text Available Natural killer (NK cells of the innate immune system are cytotoxic lymphocytes that play important roles following transplantation of solid organs and hematopoietic stem cells. Recognition of self HLA class I molecules by inhibitory killer cell immunoglobulin-like receptors (KIR is involved in the calibration of NK cell effector capacities during a developmental stage, allowing the subsequent recognition and elimination of target cells with decreased expression of self HLA class I (due to virus infection or tumor transformation or HLA class I disparities (in the setting of allogeneic transplantation. NK cells expressing an inhibitory KIR binding self HLA can be activated when confronted with allografts lacking a ligand for the inhibitory receptor. Following the response of the adaptive immune system, NK cells can further destroy allograft endothelium by antibody-dependent cell-mediated cytotoxicity (ADCC, triggered through cross-linking of the CD16 Fc receptor by donor-specific antibodies bound to allograft. Upon recognizing allogeneic target cells, NK cells also secrete cytokines and chemokines that drive maturation of dendritic cells to promote cellular and humoral adaptive immune responses against the allograft. The cumulative activating and inhibitory signals generated by ligation of the receptors regulates mature NK cell killing of target cells and their production of cytokines and chemokines. This review summarizes the role of NK cells in allograft rejection and proposes mechanistic concepts that indicate a prominent role for KIR-HLA interactions in facilitating NK cells for Fc receptor-mediated ADCC effector function involved in antibody-mediated rejection of solid organ transplants.

  7. Cell-type-specific and differentiation-status-dependent variations in cytotoxicity of tributyltin in cultured rat cerebral neurons and astrocytes.

    Science.gov (United States)

    Oyanagi, Koshi; Tashiro, Tomoko; Negishi, Takayuki

    2015-08-01

    Tributyltin (TBT) is an organotin used as an anti-fouling agent for fishing nets and ships and it is a widespread environmental contaminant at present. There is an increasing concern about imperceptible but serious adverse effect(s) of exposure to chemicals existing in the environment on various organs and their physiological functions, e.g. brain and mental function. Here, so as to contribute to improvement of and/or advances in in vitro cell-based assay systems for evaluating brain-targeted adverse effect of chemicals, we tried to evaluate cell-type-specific and differentiation-status-dependent variations in the cytotoxicity of TBT towards neurons and astrocytes using the four culture systems differing in the relative abundance of these two types of cells; primary neuron culture (> 95% neurons), primary neuron-astrocyte (2 : 1) mix culture, primary astrocyte culture (> 95% astrocytes), and passaged astrocyte culture (100% proliferative astrocytes). Cell viability was measured at 48 hr after exposure to TBT in serum-free medium. IC50's of TBT were 198 nM in primary neuron culture, 288 nM in primary neuron-astrocyte mix culture, 2001 nM in primary astrocyte culture, and 1989 nM in passaged astrocyte culture. Furthermore, in primary neuron-astrocyte mix culture, vulnerability of neurons cultured along with astrocytes to TBT toxicity was lower than that of neurons cultured purely in primary neuron culture. On the other hand, astrocytes in primary neuron-astrocyte mix culture were considered to be more vulnerable to TBT than those in primary or passaged astrocyte culture. The present study demonstrated variable cytotoxicity of TBT in neural cells depending on the culture condition.

  8. Temperature-dependent surface density of alkylthiol monolayers on gold nanocrystals

    Science.gov (United States)

    Liu, Xuepeng; Lu, Pin; Zhai, Hua; Wu, Yucheng

    2018-03-01

    Atomistic molecular dynamics (MD) simulations are performed to study the surface density of passivating monolayers of alkylthiol chains on gold nanocrystals at temperatures ranging from 1 to 800 K. The results show that the surface density of alkylthiol monolayer reaches a maximum value at near room temperature (200-300 K), while significantly decreases with increasing temperature in the higher temperature region (> 300 {{K}}), and slightly decreases with decreasing temperature at low temperature (< 200 {{K}}). We find that the temperature dependence of surface ligand density in the higher temperature region is attributed to the substantial ligand desorption induced by the thermal fluctuation, while that at low temperature results from the reduction in entropy caused by the change in the ordering of passivating monolayer. These results are expected helpful to understand the temperature-dependent surface coverage of gold nanocrystals.

  9. Metastable primordial germ cell-like state induced from mouse embryonic stem cells by Akt activation

    Energy Technology Data Exchange (ETDEWEB)

    Yamano, Noriko [Graduate School of Frontier Biosciences, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Kimura, Tohru, E-mail: tkimura@patho.med.osaka-u.ac.jp [Department of Pathology, Medical School, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Watanabe-Kushima, Shoko [Graduate School of Frontier Biosciences, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Shinohara, Takashi [Department of Molecular Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8501 (Japan); Nakano, Toru, E-mail: tnakano@patho.med.osaka-u.ac.jp [Graduate School of Frontier Biosciences, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Department of Pathology, Medical School, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan)

    2010-02-12

    Specification to primordial germ cells (PGCs) is mediated by mesoderm-induction signals during gastrulation. We found that Akt activation during in vitro mesodermal differentiation of embryonic stem cells (ESCs) generated self-renewing spheres with differentiation states between those of ESCs and PGCs. Essential regulators for PGC specification and their downstream germ cell-specific genes were expressed in the spheres, indicating that the sphere cells had commenced differentiation to the germ lineage. However, the spheres did not proceed to spermatogenesis after transplantation into testes. Sphere cell transfer to the original feeder-free ESC cultures resulted in chaotic differentiation. In contrast, when the spheres were cultured on mouse embryonic fibroblasts or in the presence of ERK-cascade and GSK3 inhibitors, reversion to the ESC-like state was observed. These results indicate that Akt signaling promotes a novel metastable and pluripotent state that is intermediate to those of ESCs and PGCs.

  10. Chimeric antigen receptor (CAR-specific monoclonal antibody to detect CD19-specific T cells in clinical trials.

    Directory of Open Access Journals (Sweden)

    Bipulendu Jena

    Full Text Available Clinical trials targeting CD19 on B-cell malignancies are underway with encouraging anti-tumor responses. Most infuse T cells genetically modified to express a chimeric antigen receptor (CAR with specificity derived from the scFv region of a CD19-specific mouse monoclonal antibody (mAb, clone FMC63. We describe a novel anti-idiotype monoclonal antibody (mAb to detect CD19-specific CAR(+ T cells before and after their adoptive transfer. This mouse mAb was generated by immunizing with a cellular vaccine expressing the antigen-recognition domain of FMC63. The specificity of the mAb (clone no. 136.20.1 was confined to the scFv region of the CAR as validated by inhibiting CAR-dependent lysis of CD19(+ tumor targets. This clone can be used to detect CD19-specific CAR(+ T cells in peripheral blood mononuclear cells at a sensitivity of 1∶1,000. In clinical settings the mAb is used to inform on the immunophenotype and persistence of administered CD19-specific T cells. Thus, our CD19-specific CAR mAb (clone no. 136.20.1 will be useful to investigators implementing CD19-specific CAR(+ T cells to treat B-lineage malignancies. The methodology described to develop a CAR-specific anti-idiotypic mAb could be extended to other gene therapy trials targeting different tumor associated antigens in the context of CAR-based adoptive T-cell therapy.

  11. Intensity-dependent resonant transmission of x-rays in solid-density aluminum plasma

    Science.gov (United States)

    Cho, M. S.; Chung, H.-K.; Cho, B. I.

    2018-05-01

    X-ray free-electron lasers (XFELs) provide unique opportunities to generate and investigate dense plasmas. The absorption and transmission properties of x-ray photons in dense plasmas are important in characterizing the state of the plasmas. Experimental evidence shows that the transmission of x-ray photons through dense plasmas depends greatly on the incident XFEL intensity. Here, we present a detailed analysis of intensity-dependent x-ray transmission in solid-density aluminum using collisional-radiative population kinetics calculations. Reverse saturable absorption (RSA), i.e., an increase in x-ray absorption with intensity has been observed for photon energies below the K-absorption edge and in the intensity range of 1016-1017 W/cm2 for XFEL photons with 1487 eV. At higher intensities, a transition from RSA to saturable absorption (SA) is predicted; thus, the x-ray absorption decreases with intensity above a threshold value. For XFEL photon energies of 1501 eV and 1515 eV, the transition from RSA to SA occurs at XFEL intensities between 1017-1018 W/cm2. Electron temperatures are predicted to be in the range of 30-50 eV for the given experimental conditions. Detailed population kinetics of the charge states explains the intensity-dependent absorption of x-ray photons and the fast modulation of XFEL pulses for both RSA and SA.

  12. Shape transition of state density for bosonic systems

    Indian Academy of Sciences (India)

    ... while the shape of the state density for EGOE(2) with m ≫ 2, is close to Gaussian. The change in shape of the state density, from semicircle to Gaussian for EGOE(k), as m increases from k to m ≫ k for fermions, has been explained mathematically by Mon and French [4] and also by Benet. Pramana – J. Phys., Vol. 81, No.

  13. Energy Efficient Pico Cell Range Expansion and Density Joint Optimization for Heterogeneous Networks with eICIC

    Directory of Open Access Journals (Sweden)

    Yanzan Sun

    2018-03-01

    Full Text Available Heterogeneous networks, constituted by conventional macro cells and overlaying pico cells, have been deemed a promising paradigm to support the deluge of data traffic with higher spectral efficiency and Energy Efficiency (EE. In order to deploy pico cells in reality, the density of Pico Base Stations (PBSs and the pico Cell Range Expansion (CRE are two important factors for the network spectral efficiency as well as EE improvement. However, associated with the range and density evolution, the inter-tier interference within the heterogeneous architecture will be challenging, and the time domain Enhanced Inter-cell Interference Coordination (eICIC technique becomes necessary. Aiming to improve the network EE, the above factors are jointly considered in this paper. More specifically, we first derive the closed-form expression of the network EE as a function of the density of PBSs and pico CRE bias based on stochastic geometry theory, followed by a linear search algorithm to optimize the pico CRE bias and PBS density, respectively. Moreover, in order to realize the pico CRE bias and PBS density joint optimization, a heuristic algorithm is proposed to achieve the network EE maximization. Numerical simulations show that our proposed pico CRE bias and PBS density joint optimization algorithm can improve the network EE significantly with low computational complexity.

  14. ERE environment- and cell type-specific transcriptional effects of estrogen in normal endometrial cells.

    Science.gov (United States)

    Lascombe, I; Sallot, M; Vuillermoz, C; Weisz, A; Adessi, G L; Jouvenot, M

    1998-04-30

    Our previous results have suggested a repression of E2 (17beta-estradiol) effect on the c-fos gene of cultured guinea-pig endometrial cells. To investigate this repression, the expression of three human c-fos gene recombinants, pFC1-BL (-2250/+41), pFC2-BL (-1400/+41) and pFC2E (-1300/-1050 and -230/+41), known to be E2-responsive in Hela cells, was studied in stromal (SC) and glandular epithelial cells (GEC). In both cellular types, pFC1-BL was not induced by E2, even in the presence of growth factors or co-transfected estrogen receptor. The pattern of pFC2-BL and pFC2E expression was strikingly different and depended on the cellular type: pFC2-BL and pFC2E induction was restricted to the glandular epithelial cells and did not occur in the SCs. We argue for a repression of E2 action which is dependent on the estrogen-responsive cis-acting element (ERE) environment and also cell type-specific involving DNA/protein and/or protein/protein interactions with cellular type-specific factors.

  15. Color-flavor locked strange quark matter in a mass density-dependent model

    International Nuclear Information System (INIS)

    Chen Yuede; Wen Xinjian

    2007-01-01

    Properties of color-flavor locked (CFL) strange quark matter have been studied in a mass-density-dependent model, and compared with the results in the conventional bag model. In both models, the CFL phase is more stable than the normal nuclear matter for reasonable parameters. However, the lower density behavior of the sound velocity in this model is completely opposite to that in the bag model, which makes the maximum mass of CFL quark stars in the mass-density-dependent model larger than that in the bag model. (authors)

  16. Achieving 12.8% Efficiency by Simultaneously Improving Open-Circuit Voltage and Short-Circuit Current Density in Tandem Organic Solar Cells.

    Science.gov (United States)

    Qin, Yunpeng; Chen, Yu; Cui, Yong; Zhang, Shaoqing; Yao, Huifeng; Huang, Jiang; Li, Wanning; Zheng, Zhong; Hou, Jianhui

    2017-06-01

    Tandem organic solar cells (TOSCs), which integrate multiple organic photovoltaic layers with complementary absorption in series, have been proved to be a strong contender in organic photovoltaic depending on their advantages in harvesting a greater part of the solar spectrum and more efficient photon utilization than traditional single-junction organic solar cells. However, simultaneously improving open circuit voltage (V oc ) and short current density (J sc ) is a still particularly tricky issue for highly efficient TOSCs. In this work, by employing the low-bandgap nonfullerene acceptor, IEICO, into the rear cell to extend absorption, and meanwhile introducing PBDD4T-2F into the front cell for improving V oc , an impressive efficiency of 12.8% has been achieved in well-designed TOSC. This result is also one of the highest efficiencies reported in state-of-the-art organic solar cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. State-dependent alterations of lipid profiles in patients with bipolar disorder.

    Science.gov (United States)

    Huang, Yu-Jui; Tsai, Shang-Ying; Chung, Kuo-Hsuan; Chen, Pao-Huan; Huang, Shou-Hung; Kuo, Chian-Jue

    2018-07-01

    Objective Serum lipid levels may be associated with the affective severity of bipolar disorder, but data on lipid profiles in Asian patients with bipolar disorder and the lipid alterations in different states of opposite polarities are scant. We investigated the lipid profiles of patients in the acute affective, partial, and full remission state in bipolar mania and depression. Methods The physically healthy patients aged between 18 and 45 years with bipolar I disorder, as well as age-matched healthy normal controls were enrolled. We compared the fasting blood levels of glucose, cholesterol, triglyceride, low-density lipoprotein, and high-density lipoprotein of manic or depressed patients in the acute phase and subsequent partial and full remission with those of their normal controls. Results A total of 32 bipolar manic patients (12 women and 20 men), 32 bipolar depressed participants (18 women and 14 men), and 64 healthy control participants took part in this study. The mean cholesterol level in acute mania was significantly lower than that in acute depression (p bipolar mania. Conclusion Circulating lipid profiles may be easily affected by affective states. The acute manic state may be accompanied by state-dependent lower cholesterol and triglyceride levels relative to that in other mood states.

  18. Stationary solution of a time dependent density matrix formalism

    International Nuclear Information System (INIS)

    Tohyama, Mitsuru

    1994-01-01

    A stationary solution of a time-dependent density-matrix formalism, which is an extension of the time-dependent Hartree-Fock theory to include the effects of two-body correlations, is obtained for the Lipkin model hamiltonian, using an adiabatic treatment of the two-body interaction. It is found that the obtained result is a reasonable approximation for the exact solution of the model. (author)

  19. Information in a Network of Neuronal Cells: Effect of Cell Density and Short-Term Depression

    KAUST Repository

    Onesto, Valentina; Cosentino, Carlo; Di Fabrizio, Enzo M.; Cesarelli, Mario; Amato, Francesco; Gentile, Francesco

    2016-01-01

    Neurons are specialized, electrically excitable cells which use electrical to chemical signals to transmit and elaborate information. Understanding how the cooperation of a great many of neurons in a grid may modify and perhaps improve the information quality, in contrast to few neurons in isolation, is critical for the rational design of cell-materials interfaces for applications in regenerative medicine, tissue engineering, and personalized lab-on-a-chips. In the present paper, we couple an integrate-and-fire model with information theory variables to analyse the extent of information in a network of nerve cells. We provide an estimate of the information in the network in bits as a function of cell density and short-term depression time. In the model, neurons are connected through a Delaunay triangulation of not-intersecting edges; in doing so, the number of connecting synapses per neuron is approximately constant to reproduce the early time of network development in planar neural cell cultures. In simulations where the number of nodes is varied, we observe an optimal value of cell density for which information in the grid is maximized. In simulations in which the posttransmission latency time is varied, we observe that information increases as the latency time decreases and, for specific configurations of the grid, it is largely enhanced in a resonance effect.

  20. Information in a Network of Neuronal Cells: Effect of Cell Density and Short-Term Depression

    KAUST Repository

    Onesto, Valentina

    2016-05-10

    Neurons are specialized, electrically excitable cells which use electrical to chemical signals to transmit and elaborate information. Understanding how the cooperation of a great many of neurons in a grid may modify and perhaps improve the information quality, in contrast to few neurons in isolation, is critical for the rational design of cell-materials interfaces for applications in regenerative medicine, tissue engineering, and personalized lab-on-a-chips. In the present paper, we couple an integrate-and-fire model with information theory variables to analyse the extent of information in a network of nerve cells. We provide an estimate of the information in the network in bits as a function of cell density and short-term depression time. In the model, neurons are connected through a Delaunay triangulation of not-intersecting edges; in doing so, the number of connecting synapses per neuron is approximately constant to reproduce the early time of network development in planar neural cell cultures. In simulations where the number of nodes is varied, we observe an optimal value of cell density for which information in the grid is maximized. In simulations in which the posttransmission latency time is varied, we observe that information increases as the latency time decreases and, for specific configurations of the grid, it is largely enhanced in a resonance effect.

  1. Information in a Network of Neuronal Cells: Effect of Cell Density and Short-Term Depression

    Directory of Open Access Journals (Sweden)

    Valentina Onesto

    2016-01-01

    Full Text Available Neurons are specialized, electrically excitable cells which use electrical to chemical signals to transmit and elaborate information. Understanding how the cooperation of a great many of neurons in a grid may modify and perhaps improve the information quality, in contrast to few neurons in isolation, is critical for the rational design of cell-materials interfaces for applications in regenerative medicine, tissue engineering, and personalized lab-on-a-chips. In the present paper, we couple an integrate-and-fire model with information theory variables to analyse the extent of information in a network of nerve cells. We provide an estimate of the information in the network in bits as a function of cell density and short-term depression time. In the model, neurons are connected through a Delaunay triangulation of not-intersecting edges; in doing so, the number of connecting synapses per neuron is approximately constant to reproduce the early time of network development in planar neural cell cultures. In simulations where the number of nodes is varied, we observe an optimal value of cell density for which information in the grid is maximized. In simulations in which the posttransmission latency time is varied, we observe that information increases as the latency time decreases and, for specific configurations of the grid, it is largely enhanced in a resonance effect.

  2. Context-dependent incremental timing cells in the primate hippocampus.

    Science.gov (United States)

    Sakon, John J; Naya, Yuji; Wirth, Sylvia; Suzuki, Wendy A

    2014-12-23

    We examined timing-related signals in primate hippocampal cells as animals performed an object-place (OP) associative learning task. We found hippocampal cells with firing rates that incrementally increased or decreased across the memory delay interval of the task, which we refer to as incremental timing cells (ITCs). Three distinct categories of ITCs were identified. Agnostic ITCs did not distinguish between different trial types. The remaining two categories of cells signaled time and trial context together: One category of cells tracked time depending on the behavioral action required for a correct response (i.e., early vs. late release), whereas the other category of cells tracked time only for those trials cued with a specific OP combination. The context-sensitive ITCs were observed more often during sessions where behavioral learning was observed and exhibited reduced incremental firing on incorrect trials. Thus, single primate hippocampal cells signal information about trial timing, which can be linked with trial type/context in a learning-dependent manner.

  3. Quantification of mammalian tumor cell state plasticity with digital holographic cytometry

    Science.gov (United States)

    Hejna, Miroslav; Jorapur, Aparna; Zhang, Yuntian; Song, Jun S.; Judson, Robert L.

    2018-02-01

    Individual cells within isogenic tumor populations can exhibit distinct cellular morphologies, behaviors, and molecular profiles. Cell state plasticity refers to the propensity of a cell to transition between these different morphologies and behaviors. Elevation of cell state plasticity is thought to contribute to critical stages in tumor evolution, including metastatic dissemination and acquisition of therapeutic resistance. However, methods for quantifying general plasticity in mammalian cells remain limited. Working with a HoloMonitor M4 digital holographic cytometry platform, we have established a machine learning-based pipeline for high accuracy and label-free classification of adherent cells. We use twenty-six morphological and optical density-derived features for label-free identification of cell state in heterogeneous cultures. The system is housed completely within a mammalian cell incubator, permitting the monitoring of changes in cell state over time. Here we present an application of our approach for studying cell state plasticity. Human melanoma cell lines of known metastatic potential were monitored in standard growth conditions. The rate of feature change was quantified for each individual cell in the populations. We observed that cells of higher metastatic potential exhibited more rapid fluctuation of cell state in homeostatic conditions. The approach we demonstrate will be advantageous for further investigations into the factors that influence cell state plasticity.

  4. Shell correction approach to nuclear state densities and the competition between fission and neutron emission of 210Po

    International Nuclear Information System (INIS)

    Gottschalk, P.A.; Ledergerber, T.

    Starting from the Hartree-Fock approximation to the grand-canonical partition function we formulate a consistent renormalization of the ground state energy and the intrinsic state density as a function of deformation. The relationship to recent selfconsistent temperature dependent calculations is discussed. The competition between fission and neutron emission, GAMMA sub(f)/GAMMA sub(n)(E), of 210 Po is studied within the framework of the statistical theory as an example. Calculations using renormalized state densities are compared with usual shell model calculations and experimental data. It is found that the usual calculations reflect the incorrect uniform deformation dependence of the shell model spectral function. Important changes due to renormalization are found: a rapid change of the shape of the transition state at approximately 45 MeV excitation energy, GAMMA sub(f)/GAMMA sub(n)(E) remains smaller than unity for all excitation energies and the deformation of the transition state increases after the 'shape transition' at 45 MeV monotonically towards the liquid drop saddle point deformation with a tendency towards slightly larger deformations. (author)

  5. A murine ESC-like state facilitates transgenesis and homologous recombination in human pluripotent stem cells

    NARCIS (Netherlands)

    C. Buecker (Christa); H.H. Chen; J.M. Polo (Jose); L. Daheron (Laurence); L. Bu (Lei); T.S. Barakat (Tahsin Stefan); P. Okwieka (Patricia); A. Porter (Andrew); J.H. Gribnau (Joost); K. Hochedlinger (Konrad); N. Geijsen (Niels)

    2010-01-01

    textabstractMurine pluripotent stem cells can exist in two functionally distinct states, LIF-dependent embryonic stem cells (ESCs) and bFGF-dependent epiblast stem cells (EpiSCs). However, human pluripotent cells so far seemed to assume only an epiblast-like state. Here we demonstrate that human

  6. Capacity of lung stroma to educate dendritic cells inhibiting mycobacteria-specific T-cell response depends upon genetic susceptibility to tuberculosis.

    Science.gov (United States)

    Kapina, Marina A; Rubakova, Elvira I; Majorov, Konstantin B; Logunova, Nadezhda N; Apt, Alexander S

    2013-01-01

    The balance between activation and inhibition of local immune responses in affected tissues during prolonged chronic infections is important for host protection. There is ample evidence that regulatory, tolerogenic dendritic cells (DC) are developed and present in tissues and inhibit overwhelming inflammatory reactions. Also, it was firmly established that stromal microenvironment of many organs is able to induce development of immature regulatory DC (DCreg), an essential element of a general immune regulatory network. However, direct experimental data demonstrating inhibition of immune responses by stroma-instructed immature DCreg in infectious models are scarce, and virtually nothing is known about functioning of this axis of immunity during tuberculosis (TB) infection. In this study, we demonstrate that lung stromal cells are capable of supporting the development in culture of immature CD11b(+)CD11c(low)CD103(-) DCreg from lineage-negative (lin(-)) bone marrow precursors. DCreg developed on lung stroma isolated from mice of genetically TB-hyper-susceptible I/St and relatively resistant B6 inbred strains inhibited proliferative response of mycobacteria-specific CD4(+) T-cell lines a dose-dependent manner. Importantly, the inhibitory activity of B6 DCreg was substantially higher than that of I/St Dcreg. Moreover, when the donors of stromal cells were chronically infected with virulent mycobacteria, the capacity to instruct inhibitory DCreg was retained in B6, but further diminished in I/St stromal cells. DCreg-provided suppression was mediated by a few soluble mediators, including PGE2, NO and IL-10. The content of CD4(+)Foxp3(+) Treg cells in the mediastinal, lung-draining lymph nodes at the advanced stages of chronic infection did not change in I/St, but increased 2-fold in B6 mice, and lung pathology was much more pronounced in the former mice. Taken together, these data provide genetic evidence that the capacity to maintain populations of regulatory cells

  7. Capacity of lung stroma to educate dendritic cells inhibiting mycobacteria-specific T-cell response depends upon genetic susceptibility to tuberculosis.

    Directory of Open Access Journals (Sweden)

    Marina A Kapina

    Full Text Available The balance between activation and inhibition of local immune responses in affected tissues during prolonged chronic infections is important for host protection. There is ample evidence that regulatory, tolerogenic dendritic cells (DC are developed and present in tissues and inhibit overwhelming inflammatory reactions. Also, it was firmly established that stromal microenvironment of many organs is able to induce development of immature regulatory DC (DCreg, an essential element of a general immune regulatory network. However, direct experimental data demonstrating inhibition of immune responses by stroma-instructed immature DCreg in infectious models are scarce, and virtually nothing is known about functioning of this axis of immunity during tuberculosis (TB infection. In this study, we demonstrate that lung stromal cells are capable of supporting the development in culture of immature CD11b(+CD11c(lowCD103(- DCreg from lineage-negative (lin(- bone marrow precursors. DCreg developed on lung stroma isolated from mice of genetically TB-hyper-susceptible I/St and relatively resistant B6 inbred strains inhibited proliferative response of mycobacteria-specific CD4(+ T-cell lines a dose-dependent manner. Importantly, the inhibitory activity of B6 DCreg was substantially higher than that of I/St Dcreg. Moreover, when the donors of stromal cells were chronically infected with virulent mycobacteria, the capacity to instruct inhibitory DCreg was retained in B6, but further diminished in I/St stromal cells. DCreg-provided suppression was mediated by a few soluble mediators, including PGE2, NO and IL-10. The content of CD4(+Foxp3(+ Treg cells in the mediastinal, lung-draining lymph nodes at the advanced stages of chronic infection did not change in I/St, but increased 2-fold in B6 mice, and lung pathology was much more pronounced in the former mice. Taken together, these data provide genetic evidence that the capacity to maintain populations of regulatory

  8. Time-dependent density functional theory (TD-DFT) coupled with reference interaction site model self-consistent field explicitly including spatial electron density distribution (RISM-SCF-SEDD)

    Energy Technology Data Exchange (ETDEWEB)

    Yokogawa, D., E-mail: d.yokogawa@chem.nagoya-u.ac.jp [Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8602 (Japan)

    2016-09-07

    Theoretical approach to design bright bio-imaging molecules is one of the most progressing ones. However, because of the system size and computational accuracy, the number of theoretical studies is limited to our knowledge. To overcome the difficulties, we developed a new method based on reference interaction site model self-consistent field explicitly including spatial electron density distribution and time-dependent density functional theory. We applied it to the calculation of indole and 5-cyanoindole at ground and excited states in gas and solution phases. The changes in the optimized geometries were clearly explained with resonance structures and the Stokes shift was correctly reproduced.

  9. Specific dose-dependent effects of ethane 1,2-dimethanesulfonate in rat and mouse Leydig cells and non-steroidogenic cells on programmed cell death

    NARCIS (Netherlands)

    F.F.G. Rommerts (Focko); L. Kuhne; W.A. van Cappellen (Gert); D.M. Stocco; S.R. King (Steven); A. Jankowska

    2004-01-01

    textabstractThe mechanism by which ethane 1,2-dimethanesulfonate (EDS) selectively kills Leydig cells is poorly understood. To characterize further the cell-specific actions of EDS, we studied biochemical and morphological changes during apoptosis in different Leydig cell and

  10. Particle-particle and hole-hole RPA correlations at finite temperature and the temperature dependence of the level density parameter

    International Nuclear Information System (INIS)

    Vinh Mau, N.

    1987-11-01

    The pp-hh RPA equations obtained by summing the infinite series of ladder, upwards and backwards going diagrams in the temperature two particle Green's functions are derived at finite temperature. The contribution to the thermodynamic grand potential due to pp-hh RPA correlations is calculated simultaneously to that of ph RPA correlations. A schematic model is constructed which shows that, as for ph RPA states, the energies of pp and hh RPA states have no temperature dependence at not too high temperature. Within the same model, the temperature dependence of the level density parameter is discussed

  11. Particle-particle and hole-hole RPA correlations at finite temperature and the temperature dependence of the level density parameter

    International Nuclear Information System (INIS)

    Vinh Mau, N.

    1989-01-01

    The pp-hh RPA equations obtained by summing the infinite series of ladder, upwards- and backwards-going diagrams in the temperature two-particle Green functions are derived at finite temperature. The contribution to the thermodynamic grand potential due to pp-hh RPA correlations is calculated simultaneously to that of ph RPA correlations. A schematic model is constructed which shows that, as for ph RPA states, the energies of pp and hh RPA states have no temperature dependence at not too high temperature. Within the same model, the temperature dependence of the level density parameter is discussed. (orig.)

  12. Density dependence of relaxation dynamics in glass formers, and ...

    Indian Academy of Sciences (India)

    Anshul D S Parmar

    formers, we study the variation of relaxation dynamics with density, rather than temperature, as a control ... stronger behaviour, the use of scaled variables involving temperature and ... of the temperature dependence of B as written defines.

  13. (p,V{sub m},T,x) measurements for aqueous LiNO{sub 3} solutions[Density; Concentration; Electrolyte solutions; Equation of state; Lithium nitrate; Saturated density; Saturated pressure; Temperature; Water

    Energy Technology Data Exchange (ETDEWEB)

    Abdulagatov, I.M. E-mail: ilmutdin@boulder.nist.govmangur@datacom.ru; Azizov, N.D. E-mail: Nazim_Azizov@yahoo.com

    2004-01-01

    (p,V{sub m},T,x) properties of four aqueous LiNO{sub 3} solutions (0.181, 0.526, 0.963, and 1.728) mol {center_dot} kg{sup -1} H{sub 2}O were measured in the liquid phase with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made for 10 isotherms between (298 and 573) K. The range of pressure was from (2 to 40) MPa. The total uncertainty of density, pressure, temperature, and concentration measurements were estimated to be less than 0.06 %, 0.05 %, 10 mK, and 0.014 %, respectively. The values of saturated density were determined by extrapolating experimental (p,{rho}) data to the vapor-pressure at fixed temperature and composition using an interpolating equation. A polynomial type of equation of state for specific volume was obtained as a function of temperature, pressure, and composition by a least-squares method from the experimental data. The average absolute deviation (AAD) between measured and calculated values from this polynomial equation for density was 0.02 %. Measured values of solution density were compared with values calculated from Pitzer's ion-interaction equation. The agreement is within (0.2 to 0.4) % depending of concentration range.

  14. Explaining density-dependent regulation in earthworm populations using life-history analysis

    NARCIS (Netherlands)

    Kammenga, J.E.; Spurgeon, D.J.; Svendsen, C.; Weeks, J.M.

    2003-01-01

    At present there is little knowledge about how density regulates population growth rate and to what extent this is determined by life-history patterns. We compared density dependent population consequences in the Nicholsonian sense based oil experimental observations and life-history modeling for

  15. Tuberculosis Therapy Modifies the Cytokine Profile, Maturation State, and Expression of Inhibitory Molecules on Mycobacterium tuberculosis-Specific CD4+ T-Cells.

    Directory of Open Access Journals (Sweden)

    Kapil K Saharia

    Full Text Available Little is known about the expression of inhibitory molecules cytotoxic T-lymphocyte antigen-4 (CTLA-4 and programmed-death-1 (PD-1 on Mycobacterium tuberculosis (Mtb-specific CD4 T-cells and how their expression is impacted by TB treatment.Cryopreserved PBMCs from HIV-TB co-infected and TB mono-infected patients with untreated and treated tuberculosis (TB disease were stimulated for six hours with PPD and stained. Using polychromatic flow cytometry, we characterized the differentiation state, cytokine profile, and inhibitory molecule expression on PPD-specific CD4 T-cells.In our HIV-TB co-infected cohort, TB treatment increased the proportion of PPD-specific CD4 T-cells co-producing IFN-γ+IL-2+TNF-α+ and IFN-γ+IL-2+ (p = 0.0004 and p = 0.0002, respectively while decreasing the proportion of PPD-specific CD4 T-cells co-producing IFN-γ+MIP1-β+TNF-α+ and IFN-γ+MIP1-β+. The proportion of PPD-specific CD4 T-cells expressing an effector memory phenotype decreased (63.6% vs 51.6%, p = 0.0015 while the proportion expressing a central memory phenotype increased (7.8% vs. 21.7%, p = 0.001 following TB treatment. TB treatment reduced the proportion of PPD-specific CD4 T-cells expressing CTLA-4 (72.4% vs. 44.3%, p = 0.0005 and PD-1 (34.5% vs. 29.2%, p = 0.03. Similar trends were noted in our TB mono-infected cohort.TB treatment alters the functional profile of Mtb-specific CD4 T-cells reflecting shifts towards a less differentiated maturational profile and decreases PD-1 and CTLA-4 expression. These could serve as markers of reduced mycobacterial burden. Further study is warranted.

  16. The electronic density of states of disordered compounds

    International Nuclear Information System (INIS)

    Geertsma, W.; Dijkstra, J.

    1984-11-01

    Recently, the electronic properties of liquid alkali (Li, Na, K, Rb, Cs)-group IV (Si, Ge, Sn, Pb) alloys have been discussed by the present authors using a tight-binding model. Only anion orbitals (= group IV) are taken into account. Disorder is described by a pseudo lattice, which takes into account local coordination in one of the sublattices (cation or anion) only. In the first part of this paper it is shown that this approximation is consistent with the usual valence rules used by structural chemists for crystalline structures. In the second part of the paper the solutions for the density of states of the tight-binding Hamiltonian are studied for a number of pseudolattices. The infinite set of Green function equations is solved by using the effective transfer method, which replaces the famous Block condition. It is shown that such a model can explain the formation of bandgaps in disordered systems. By choosing the proper smallest cluster(s) of transfer loops to model the real structure by a pseudolattice, a density of states is obtained which represents properly that of the corresponding crystalline structure. Structures reminiscent to those caused by van Hove singularities already appear in the electronic density of states when relatively small cluster(s) of transfer loops are used. The approach outlined in this paper is capable of describing the electronic density of states due to various degrees of local order in a sublattice. Some of the peculiarities occurring in the solution of the density of states of certain pseudolattices, such as poles outside the band, are discussed in an appendix. (author)

  17. Changes in seasonal climate outpace compensatory density-dependence in eastern brook trout

    Science.gov (United States)

    Bassar, Ronald D.; Letcher, Benjamin H.; Nislow, Keith H.; Whiteley, Andrew R.

    2016-01-01

    Understanding how multiple extrinsic (density-independent) factors and intrinsic (density-dependent) mechanisms influence population dynamics has become increasingly urgent in the face of rapidly changing climates. It is particularly unclear how multiple extrinsic factors with contrasting effects among seasons are related to declines in population numbers and changes in mean body size and whether there is a strong role for density-dependence. The primary goal of this study was to identify the roles of seasonal variation in climate driven environmental direct effects (mean stream flow and temperature) versus density-dependence on population size and mean body size in eastern brook trout (Salvelinus fontinalis). We use data from a 10-year capture-mark-recapture study of eastern brook trout in four streams in Western Massachusetts, USA to parameterize a discrete-time population projection model. The model integrates matrix modeling techniques used to characterize discrete population structures (age, habitat type and season) with integral projection models (IPMs) that characterize demographic rates as continuous functions of organismal traits (in this case body size). Using both stochastic and deterministic analyses we show that decreases in population size are due to changes in stream flow and temperature and that these changes are larger than what can be compensated for through density-dependent responses. We also show that the declines are due mostly to increasing mean stream temperatures decreasing the survival of the youngest age class. In contrast, increases in mean body size over the same period are the result of indirect changes in density with a lesser direct role of climate-driven environmental change.

  18. Evidence of Change in the Density of States during the Martensitic Phase Transformation of Ni-Mn-In Metamagnetic Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Rie Y Umetsu

    2017-10-01

    Full Text Available Specific heat measurements were performed at low temperatures for Ni50Mn50−xInx alloys to determine their Debye temperatures (θD and electronic specific heat coefficients (γ. For x ≤ 15, where the ground state is the martensite (M phase, θD decreases linearly and γ increases slightly with increasing In content. For x ≥ 16.2, where the ground state is the ferromagnetic parent (P phase, γ increases with decreasing In content. Extrapolations of the composition dependences of θD and γ in both the phases suggest that these values change discontinuously during the martensitic phase transformation. The value of θD in the M phase is larger than that in the P phase. The behavior is in accordance with the fact that the volume of the M phase is more compressive than that of the P phase. On the other hand, γ is slightly larger in the P phase, in good agreement with the reported density of states around the Fermi energy obtained by the first-principle calculations.

  19. Density of states in Mo-Ru amorphous alloys

    International Nuclear Information System (INIS)

    Miyakawa, W.

    1985-01-01

    The density of states is calculated for several compositions of amorphous Mo 1-x Ru x . In order to simulate amorphous clusters, the structures (atomic positions) utilized in the calculations were built from a small dense randomly packed unit of hard spheres with periodic boundary conditions. The density of states is calculated from a tight-binding Hamiltonian with hopping integrals parametrized in terms of the ddσ, ddΠ and ddδ molecular integrals. The results for pure Mo and pure Ru, compared in the canonical band aproximation, agree well with the literature. For binary alloys, the comparison of the calculated density of states with the rigid band aproximation results indicates that a more complex approach than the rigid band model must be used, even when the two atoms have similar bands, with band centers at nearly the same energy. The results also indicate that there is no relation between the peak in the superconducting critical temperature as a function of the number of valence eletrons per atom (e/a) in the region near Mo(e/a=6) and the peak of the density of states at the Fermi level in the same region, as has been sugested by some authors. (Author) [pt

  20. Compositions and methods for xylem-specific expression in plant cells

    Energy Technology Data Exchange (ETDEWEB)

    Han, Kyung-Hwan; Ko, Jae-Heung

    2017-12-19

    The invention provides promoter sequences that regulate specific expression of operably linked sequences in developing xylem cells and/or in developing xylem tissue. The developing xylem-specific sequences are exemplified by the DX5, DX8, DX11, and DX15 promoters, portions thereof, and homologs thereof. The invention further provides expression vectors, cells, tissues and plants that contain the invention's sequences. The compositions of the invention and methods of using them are useful in, for example, improving the quantity (biomass) and/or the quality (wood density, lignin content, sugar content etc.) of expressed biomass feedstock products that may be used for bioenergy, biorefinary, and generating wood products such as pulp, paper, and solid wood.

  1. Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

    International Nuclear Information System (INIS)

    Duverger, James Elber; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

    2014-01-01

    Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction–diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh–Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation. (paper)

  2. Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

    Science.gov (United States)

    Elber Duverger, James; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

    2014-11-01

    Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction-diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh-Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation.

  3. Advanced Space Power Systems (ASPS): High Specific Energy Li-ion Battery Cells

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of this project element is to increase the specific energy of Li-ion battery cells to 265 Wh/kg and the energy density to 500 Wh/L at 10oC while maintaining...

  4. Density dependence, density independence, and recruitment in the American shad (Alosa sapidissima) population of the Connecticut River

    International Nuclear Information System (INIS)

    Leggett, W.C.

    1977-01-01

    The role of density-dependent and density-independent factors in the regulation of the stock-recruitment relationship of the American shad (Alosa sapidissima) population of the Connecticut River was investigated. Significant reductions in egg-to-adult survival and juvenile growth rates occurred in the Holyoke--Turners Falls region in response to increases in the intensity of spawning in this area. For the Connecticut River population as a whole, egg-to-adult survival was estimated to be 0.00056 percent at replacement levels, and 0.00083 percent at the point of maximum population growth. Density-independent factors result in significant annual deviations from recruitment levels predicted by the density-dependent model. Temperature and flow regimes during spawning and early larval development are involved, but they explain only a small portion (less than 16 percent) of the total variation. In spite of an extensive data base, the accuracy of predictions concerning the potential effects of additional mortality to pre-recruit stages is low. The implications of these findings for environmental impact assessment are discussed

  5. Cannabinoid Receptor 2 (CB2 Plays a Role in the Generation of Germinal Center and Memory B Cells, but Not in the Production of Antigen-Specific IgG and IgM, in Response to T-dependent Antigens.

    Directory of Open Access Journals (Sweden)

    Sreemanti Basu

    Full Text Available The cannabinoid receptor 2 (CB2 has been reported to modulate B cell functions including migration, proliferation and isotype class switching. Since these processes are required for the generation of the germinal center (GC and antigen-specific plasma and memory cells following immunization with a T-dependent antigen, CB2 has the capacity to alter the quality and magnitude of T-dependent immune responses. To address this question, we immunized WT and CB2(-/- mice with the T-dependent antigen 4-hydroxy-3-nitrophenylacetyl (NP-chicken-gamma-globulin (CGG and measured GC B cell formation and the generation of antigen-specific B cells and serum immunoglobulin (Ig. While there was a significant reduction in the number of splenic GC B cells in CB2(-/- mice early in the response there was no detectable difference in the number of NP-specific IgM and IgG1 plasma cells. There was also no difference in NP-specific IgM and class switched IgG1 in the serum. In addition, we found no defect in the homing of plasma cells to the bone marrow (BM and affinity maturation, although memory B cell cells in the spleen were reduced in CB2(-/- mice. CB2-deficient mice also generated similar levels of antigen-specific IgM and IgG in the serum as WT following immunization with sheep red blood cells (sRBC. This study demonstrates that although CB2 plays a role in promoting GC and memory B cell formation/maintenance in the spleen, it is dispensable on all immune cell types required for the generation of antigen-specific IgM and IgG in T-dependent immune responses.

  6. Low density of membrane particles in auditory hair cells of lizards and birds suggests an absence of somatic motility.

    Science.gov (United States)

    Köppl, Christine; Forge, Andrew; Manley, Geoffrey A

    2004-11-08

    Hair cells are the mechanoreceptive cells of the vertebrate lateral line and inner ear. In addition to their sensory function, hair cells display motility and thus themselves generate mechanical energy, which is thought to enhance sensitivity. Two principal cellular mechanism are known that can mediate hair-cell motility in vitro. One of these is based on voltage-dependent changes of an intramembrane protein and has so far been demonstrated only in outer hair cells of the mammalian cochlea. Correlated with this, the cell membranes of outer hair cells carry an extreme density of embedded particles, as revealed by freeze fracturing. The present study explored the possibility of membrane-based motility in hair cells of nonmammals, by determining their density of intramembrane particles. Replicas of freeze-fractured membrane were prepared from auditory hair cells of a lizard, the Tokay gecko, and a bird, the barn owl. These species were chosen because of independent evidence for active cochlear mechanics, in the form of spontaneous otoacoustic emissions. For quantitative comparison, mammalian inner and outer hair cells, as well as vestibular hair, cells were reevaluated. Lizard and bird hair cells displayed median densities of 2,360 and 1,880 intramembrane particles/microm2, respectively. This was not significantly different from the densities in vestibular and mammalian inner hair cells; however, it was about half the density in of mammalian outer hair cells. This suggests that nonmammalian hair cells do not possess high densities of motor protein in their membranes and are thus unlikely to be capable of somatic motility. 2004 Wiley-Liss, Inc.

  7. Temperature dependence of photovoltaic cells, modules, and systems

    Energy Technology Data Exchange (ETDEWEB)

    Emery, K.; Burdick, J.; Caiyem, Y. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1996-05-01

    Photovoltaic (PV) cells and modules are often rated in terms of a set of standard reporting conditions defined by a temperature, spectral irradiance, and total irradiance. Because PV devices operates over a wide range of temperatures and irradiances, the temperature and irradiance related behavior must be known. This paper surveys the temperature dependence of crystalline and thin-film, state-of-the-art, research-size cells, modules, and systems measured by a variety of methods. The various error sources and measurement methods that contribute to cause differences in the temperature coefficient for a given cell or module measured with various methods are discussed.

  8. The time-dependent density matrix renormalisation group method

    Science.gov (United States)

    Ma, Haibo; Luo, Zhen; Yao, Yao

    2018-04-01

    Substantial progress of the time-dependent density matrix renormalisation group (t-DMRG) method in the recent 15 years is reviewed in this paper. By integrating the time evolution with the sweep procedures in density matrix renormalisation group (DMRG), t-DMRG provides an efficient tool for real-time simulations of the quantum dynamics for one-dimensional (1D) or quasi-1D strongly correlated systems with a large number of degrees of freedom. In the illustrative applications, the t-DMRG approach is applied to investigate the nonadiabatic processes in realistic chemical systems, including exciton dissociation and triplet fission in polymers and molecular aggregates as well as internal conversion in pyrazine molecule.

  9. Time-dependent quantum many-body systems. Linear response, electronic transport, and reduced density matrices

    International Nuclear Information System (INIS)

    Appel, H.

    2007-05-01

    In part I of this work we present a double-pole approximation (DPA) to the response equations of time-dependent density functional theory (TDDFT). The double-pole approximation provides an exact description of systems with two strongly coupled excitations which are isolated from the rest of the spectrum. In contrast to the traditional single-pole approximation of TDDFT the DPA also yields corrections to the Kohn-Sham oscillator strengths. We also demonstrate how to invert the double-pole solution which allows us to predict matrix elements of the exchange-correlation kernel f xc from experimental input. We attempt some first steps towards a time-dependent generalization of reduced density matrix functional theory (RDMFT). In part II we derive equations of motion for natural orbitals and occupation numbers. Using the equation of motion for the occupation numbers we show that an adiabatic extension of presently known ground-state functionals of static RDMFT always leads to occupation numbers which are constant in time. From the stationary conditions of the equations of motion for the N-body correlations (correlated parts of the N-body matrices) we derive a new class of ground-state functionals which can be used in static RDMFT. Applications are presented for a one-dimensional model system where the time-dependent many-body Schroedinger equation can be propagated numerically. We use optimal control theory to find optimized laser pulses for transitions in a model for atomic Helium. From the numerically exact correlated wavefunction we extract the exact time evolution of natural orbitals and occupation numbers for (i) laser-driven Helium and (ii) electron-ion scattering. Part III of this work considers time-dependent quantum transport within TDDFT. We present an algorithm for the calculation of extended eigenstates of single-particle Hamiltonians which is especially tailored to a finite-difference discretization of the Schroedinger equation. We consider the propagation

  10. Time-dependent quantum many-body systems. Linear response, electronic transport, and reduced density matrices

    Energy Technology Data Exchange (ETDEWEB)

    Appel, H.

    2007-05-15

    In part I of this work we present a double-pole approximation (DPA) to the response equations of time-dependent density functional theory (TDDFT). The double-pole approximation provides an exact description of systems with two strongly coupled excitations which are isolated from the rest of the spectrum. In contrast to the traditional single-pole approximation of TDDFT the DPA also yields corrections to the Kohn-Sham oscillator strengths. We also demonstrate how to invert the double-pole solution which allows us to predict matrix elements of the exchange-correlation kernel f{sub xc} from experimental input. We attempt some first steps towards a time-dependent generalization of reduced density matrix functional theory (RDMFT). In part II we derive equations of motion for natural orbitals and occupation numbers. Using the equation of motion for the occupation numbers we show that an adiabatic extension of presently known ground-state functionals of static RDMFT always leads to occupation numbers which are constant in time. From the stationary conditions of the equations of motion for the N-body correlations (correlated parts of the N-body matrices) we derive a new class of ground-state functionals which can be used in static RDMFT. Applications are presented for a one-dimensional model system where the time-dependent many-body Schroedinger equation can be propagated numerically. We use optimal control theory to find optimized laser pulses for transitions in a model for atomic Helium. From the numerically exact correlated wavefunction we extract the exact time evolution of natural orbitals and occupation numbers for (i) laser-driven Helium and (ii) electron-ion scattering. Part III of this work considers time-dependent quantum transport within TDDFT. We present an algorithm for the calculation of extended eigenstates of single-particle Hamiltonians which is especially tailored to a finite-difference discretization of the Schroedinger equation. We consider the

  11. How can we model selectively neutral density dependence in evolutionary games.

    Science.gov (United States)

    Argasinski, Krzysztof; Kozłowski, Jan

    2008-03-01

    The problem of density dependence appears in all approaches to the modelling of population dynamics. It is pertinent to classic models (i.e., Lotka-Volterra's), and also population genetics and game theoretical models related to the replicator dynamics. There is no density dependence in the classic formulation of replicator dynamics, which means that population size may grow to infinity. Therefore the question arises: How is unlimited population growth suppressed in frequency-dependent models? Two categories of solutions can be found in the literature. In the first, replicator dynamics is independent of background fitness. In the second type of solution, a multiplicative suppression coefficient is used, as in a logistic equation. Both approaches have disadvantages. The first one is incompatible with the methods of life history theory and basic probabilistic intuitions. The logistic type of suppression of per capita growth rate stops trajectories of selection when population size reaches the maximal value (carrying capacity); hence this method does not satisfy selective neutrality. To overcome these difficulties, we must explicitly consider turn-over of individuals dependent on mortality rate. This new approach leads to two interesting predictions. First, the equilibrium value of population size is lower than carrying capacity and depends on the mortality rate. Second, although the phase portrait of selection trajectories is the same as in density-independent replicator dynamics, pace of selection slows down when population size approaches equilibrium, and then remains constant and dependent on the rate of turn-over of individuals.

  12. B7h-expressing dendritic cells and plasma B cells mediate distinct outcomes of ICOS costimulation in T cell-dependent antibody responses

    Directory of Open Access Journals (Sweden)

    Larimore Kevin

    2012-06-01

    Full Text Available Abstract Background The ICOS-B7h costimulatory receptor-ligand pair is required for germinal center formation, the production of isotype-switched antibodies, and antibody affinity maturation in response to T cell-dependent antigens. However, the potentially distinct roles of regulated B7h expression on B cells and dendritic cells in T cell-dependent antibody responses have not been defined. Results We generated transgenic mice with lineage-restricted B7h expression to assess the cell-type specific roles of B7h expression on B cells and dendritic cells in regulating T cell-dependent antibody responses. Our results show that endogenous B7h expression is reduced on B cells after activation in vitro and is also reduced in vivo on antibody-secreting plasma B cells in comparison to both naïve and germinal center B cells from which they are derived. Increasing the level of B7h expression on activated and plasma B cells in B-B7hTg mice led to an increase in the number of antibody-secreting plasma cells generated after immunization and a corresponding increase in the concentration of antigen-specific high affinity serum IgG antibodies of all isotypes, without affecting the number of responding germinal center B cells. In contrast, ICOS costimulation mediated by dendritic cells in DC-B7hTg mice contributed to germinal center formation and selectively increased IgG2a production without affecting the overall magnitude of antibody responses. Conclusions Using transgenic mice with lineage-restricted B7h expression, we have revealed distinct roles of ICOS costimulation mediated by dendritic cells and B cells in the regulation of T cell-dependent antibody responses.

  13. Probing the density dependence of the symmetry potential in intermediate-energy heavy ion collisions

    International Nuclear Information System (INIS)

    Li Qingfeng; Li Zhuxia; Soff, Sven; Gupta, Raj K; Bleicher, Marcus; Stoecker, Horst

    2005-01-01

    Based on the ultrarelativistic quantum molecular dynamics model, the effects of the density-dependent symmetry potential for baryons and of the Coulomb potential for produced mesons are investigated for neutron-rich heavy ion collisions at intermediate energies. The calculated results of the Δ - /Δ ++ and π - /π + production ratios show a clear beam-energy dependence on the density-dependent symmetry potential, which is stronger for the π - /π + ratio close to the pion production threshold. The Coulomb potential of the mesons changes the transverse momentum distribution of the π - /π + ratio significantly, though it alters only slightly the π - and π + total yields. The π - yields, especially at midrapidity or at low transverse momenta and the π - /π + ratios at low transverse momenta are shown to be sensitive probes of the density-dependent symmetry potential in dense nuclear matter. The effect of the density-dependent symmetry potential on the production of both K 0 and K + mesons is also investigated

  14. A fourteen-year review of radical cystectomy for transitional cell carcinoma demonstrating the usefulness of the concept of lymph node density

    Directory of Open Access Journals (Sweden)

    Chi W. Cheng

    2006-10-01

    Full Text Available OBJECTIVE: We studied the long-term outcome of radical cystectomy for transitional cell carcinoma and evaluated prognostic factors for disease specific survival. MATERIALS AND METHODS: A retrospective review was carried out for all cystectomies performed for transitional cell carcinoma between 1989 and 2002. Disease specific survival was correlated to patient, pathological and operative factors as well as to adjuvant therapy. RESULTS: Of the 133 cystectomies included, 100 were male and 33 were female patients. The median age was 69 years (range 43 to 86. The median follow up was 20 months (range 0 to 158. With univariate analysis, pT stage, N stage, lymph node density, carcinoma in-situ, surgical margin and post-operative radiotherapy to distant metastasis were predictive of disease specific survival. On the other hand, with multivariate analysis, only pT stage, lymph node density and post-operative radiotherapy to distant metastasis were predictive of disease specific survival. Within the group of node positive disease, lymph node density also predicted disease specific survival with both univariate and multivariate analyses. Patients with lymph node density 20% or below showed better disease specific survival. CONCLUSIONS: pT stage and lymph node density were found to be the most important predictive factors for disease specific survival after cystectomy in the Asian population.

  15. Angular momentum dependence of the nuclear level density parameter

    International Nuclear Information System (INIS)

    Aggarwal, Mamta; Kailas, S.

    2010-01-01

    Dependence of nuclear level density parameter on the angular momentum and temperature is investigated in a theoretical framework using the statistical theory of hot rotating nuclei. The structural effects are incorporated by including shell correction, shape, and deformation. The nuclei around Z≅50 with an excitation energy range of 30 to 40 MeV are considered. The calculations are in good agreement with the experimentally deduced inverse level density parameter values especially for 109 In, 113 Sb, 122 Te, 123 I, and 127 Cs nuclei.

  16. Presynaptic Regulation of Leptin in a Defined Lateral Hypothalamus-Ventral Tegmental Area Neurocircuitry Depends on Energy State.

    Science.gov (United States)

    Liu, Jing-Jing; Bello, Nicholas T; Pang, Zhiping P

    2017-12-06

    Synaptic transmission controls brain activity and behaviors, including food intake. Leptin, an adipocyte-derived hormone, acts on neurons located in the lateral hypothalamic area (LHA) to maintain energy homeostasis and regulate food intake behavior. The specific synaptic mechanisms, cell types, and neural projections mediating this effect remain unclear. In male mice, using pathway-specific retrograde tracing, whole-cell patch-clamp recordings and post hoc cell type identification, we found that leptin reduces excitatory synaptic strength onto both melanin-concentrating hormone- and orexin-expressing neurons projecting from the LHA to the ventral tegmental area (VTA), which may affect dopamine signaling and motivation for feeding. A presynaptic mechanism mediated by distinct intracellular signaling mechanisms may account for this regulation by leptin. The regulatory effects of leptin depend on intact leptin receptor signaling. Interestingly, the synaptic regulatory function of leptin in the LHA-to-VTA neuronal pathway is highly sensitive to energy states: both energy deficiency (acute fasting) and excessive energy storage (high-fat diet-induced obesity) blunt the effect of leptin. These data revealed that leptin may regulate synaptic transmission in the LHA-to-VTA neurocircuitry in an inverted "U-shape" fashion dependent on plasma glucose levels and related to metabolic states. SIGNIFICANCE STATEMENT The lateral hypothalamic area (LHA) to ventral tegmental area (VTA) projection is an important neural pathway involved in balancing whole-body energy states and reward. We found that the excitatory synaptic inputs to both orexin- and melanin-concentrating hormone expressing LHA neurons projecting to the VTA were suppressed by leptin, a peptide hormone derived from adipocytes that signals peripheral energy status to the brain. Interestingly, energy states seem to affect how leptin regulates synaptic transmission since both the depletion of energy induced by acute food

  17. Density dependence of avian clutch size in resident and migrant species: is there a constraint on the predictability of competitor density?

    NARCIS (Netherlands)

    Both, C.

    2000-01-01

    The presence of density dependence of clutch size is tested in 57 long-term population studies of 10 passerine bird species. In about half of the studies of tit species Parus spp. density dependence of clutch size was found, while none was found in studies of two flycatcher species Ficedula spp. One

  18. Solvent effects in ionic liquids: empirical linear energy-density relationships.

    Science.gov (United States)

    Cerda-Monje, A; Aizman, A; Tapia, R A; Chiappe, C; Contreras, R

    2012-07-28

    Multiparameter linear energy-density relationships to model solvent effects in room temperature ionic liquids (RTILs) are introduced and tested. The model incorporates two solvent dependent and two specific solute-solvent parameters represented by a set of electronic indexes derived from the conceptual density functional theory. The specific solute-solvent interactions are described in terms of the electronic chemical potential for proton migration between the anion or cation and the transition state structure of a specific reaction. These indexes provide a quantitative estimation of the hydrogen bond (HB) acceptor basicity and the hydrogen bond donor acidity of the ionic solvent, respectively. A sound quantitative scale of HB strength is thereby obtained. The solvent dependent contributions are described by the global electrophilicity of the cation and nucleophilicity of the anion forming the ionic liquid. The model is illustrated for the kinetics of cycloaddition of cyclopentadiene towards acrolein. In general, cation HB acidity outweighs the remaining parameters for this reaction.

  19. Nanofiber density determines endothelial cell behavior on hydrogel matrix

    Energy Technology Data Exchange (ETDEWEB)

    Berti, Fernanda V., E-mail: fernanda@intelab.ufsc.br [Department of Chemical and Food Engineering, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil); Rambo, Carlos R. [Department of Electrical Engineering, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil); Dias, Paulo F. [Department of Cell Biology, Embryology and Genetics, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil); Porto, Luismar M. [Department of Chemical and Food Engineering, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil)

    2013-12-01

    When cultured under static conditions, bacterial cellulose pellicles, by the nature of the polymer synthesis that involves molecular oxygen, are characterized by two distinct surface sides. The upper surface is denser in fibers (entangled) than the lower surface that shows greater surface porosity. Human umbilical vein endothelial cells (HUVECs) were used to exploit how the microarchitecture (i.e., surface porosity, fiber network structure, surface topology, and fiber density) of bacterial cellulose pellicle surfaces influence cell–biomaterial interaction and therefore cell behavior. Adhesion, cell ingrowth, proliferation, viability and cell death mechanisms were evaluated on the two pellicle surface sides. Cell behavior, including secondary necrosis, is influenced only by the microarchitecture of the surface, since the biomaterial is extremely pure (constituted of cellulose and water only). Cell–cellulose fiber interaction is the determinant signal in the cell–biomaterial responses, isolated from other frequently present interferences such as protein and other chemical traces usually present in cell culture matrices. Our results suggest that microarchitecture of hydrogel materials might determine the performance of biomedical products, such as bacterial cellulose tissue engineering constructs (BCTECs). - Highlights: • Topography of BC pellicle is relevant to determine endothelial cells' fate. • Cell–biomaterial response is affected by the topography of BC-pellicle surface. • Endothelial cells exhibit different behavior depending on the BC topography. • Apoptosis and necrosis of endothelial cells were affected by the BC topography.

  20. Nanofiber density determines endothelial cell behavior on hydrogel matrix

    International Nuclear Information System (INIS)

    Berti, Fernanda V.; Rambo, Carlos R.; Dias, Paulo F.; Porto, Luismar M.

    2013-01-01

    When cultured under static conditions, bacterial cellulose pellicles, by the nature of the polymer synthesis that involves molecular oxygen, are characterized by two distinct surface sides. The upper surface is denser in fibers (entangled) than the lower surface that shows greater surface porosity. Human umbilical vein endothelial cells (HUVECs) were used to exploit how the microarchitecture (i.e., surface porosity, fiber network structure, surface topology, and fiber density) of bacterial cellulose pellicle surfaces influence cell–biomaterial interaction and therefore cell behavior. Adhesion, cell ingrowth, proliferation, viability and cell death mechanisms were evaluated on the two pellicle surface sides. Cell behavior, including secondary necrosis, is influenced only by the microarchitecture of the surface, since the biomaterial is extremely pure (constituted of cellulose and water only). Cell–cellulose fiber interaction is the determinant signal in the cell–biomaterial responses, isolated from other frequently present interferences such as protein and other chemical traces usually present in cell culture matrices. Our results suggest that microarchitecture of hydrogel materials might determine the performance of biomedical products, such as bacterial cellulose tissue engineering constructs (BCTECs). - Highlights: • Topography of BC pellicle is relevant to determine endothelial cells' fate. • Cell–biomaterial response is affected by the topography of BC-pellicle surface. • Endothelial cells exhibit different behavior depending on the BC topography. • Apoptosis and necrosis of endothelial cells were affected by the BC topography

  1. An experimental field study of delayed density dependence in natural populations of Aedes albopictus.

    Directory of Open Access Journals (Sweden)

    Rachael K Walsh

    Full Text Available Aedes albopictus, a species known to transmit dengue and chikungunya viruses, is primarily a container-inhabiting mosquito. The potential for pathogen transmission by Ae. albopictus has increased our need to understand its ecology and population dynamics. Two parameters that we know little about are the impact of direct density-dependence and delayed density-dependence in the larval stage. The present study uses a manipulative experimental design, under field conditions, to understand the impact of delayed density dependence in a natural population of Ae. albopictus in Raleigh, North Carolina. Twenty liter buckets, divided in half prior to experimentation, placed in the field accumulated rainwater and detritus, providing oviposition and larval production sites for natural populations of Ae. albopictus. Two treatments, a larvae present and larvae absent treatment, were produced in each bucket. After five weeks all larvae were removed from both treatments and the buckets were covered with fine mesh cloth. Equal numbers of first instars were added to both treatments in every bucket. Pupae were collected daily and adults were frozen as they emerged. We found a significant impact of delayed density-dependence on larval survival, development time and adult body size in containers with high larval densities. Our results indicate that delayed density-dependence will have negative impacts on the mosquito population when larval densities are high enough to deplete accessible nutrients faster than the rate of natural food accumulation.

  2. Density-dependence of functional spiking networks in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Ham, Michael I [Los Alamos National Laboratory; Gintautuas, Vadas [Los Alamos National Laboratory; Rodriguez, Marko A [Los Alamos National Laboratory; Bettencourt, Luis M A [Los Alamos National Laboratory; Bennett, Ryan [UNIV OF NORTH TEXAS; Santa Maria, Cara L [UNIV OF NORTH TEXAS

    2008-01-01

    During development, the mammalian brain differentiates into specialized regions with unique functional abilities. While many factors contribute to this functional specialization, we explore the effect neuronal density can have on neuronal interactions. Two types of networks, dense (50,000 neurons and glia support cells) and sparse (12,000 neurons and glia support cells), are studied. A competitive first response model is applied to construct activation graphs that represent pairwise neuronal interactions. By observing the evolution of these graphs during development in vitro we observe that dense networks form activation connections earlier than sparse networks, and that link-!llltropy analysis of the resulting dense activation graphs reveals that balanced directional connections dominate. Information theoretic measures reveal in addition that early functional information interactions (of order 3) are synergetic in both dense and sparse networks. However, during development in vitro, such interactions become redundant in dense, but not sparse networks. Large values of activation graph link-entropy correlate strongly with redundant ensembles observed in the dense networks. Results demonstrate differences between dense and sparse networks in terms of informational groups, pairwise relationships, and activation graphs. These differences suggest that variations in cell density may result in different functional specialization of nervous system tissue also in vivo.

  3. JTC801 Induces pH-dependent Death Specifically in Cancer Cells and Slows Growth of Tumors in Mice.

    Science.gov (United States)

    Song, Xinxin; Zhu, Shan; Xie, Yangchun; Liu, Jiao; Sun, Lingyi; Zeng, Dexing; Wang, Pengcheng; Ma, Xiaochao; Kroemer, Guido; Bartlett, David L; Billiar, Timothy R; Lotze, Michael T; Zeh, Herbert J; Kang, Rui; Tang, Daolin

    2018-04-01

    lineage kinase domain like pseudokinase [MLKL]), or ferroptosis (degradation of glutathione peroxidase 4 [GPX4]). Inhibitors of apoptosis (Z-VAD-FMK), necroptosis (necrosulfonamide), ferroptosis (ferrostatin-1), or autophagy (hydroxychloroquine) did not prevent JTC801-induced death of PANC1 or MiaPaCa2 cells. The cytotoxic effects of JTC801 in immortalized fibroblast cell lines was not affected by disruption of genes that promote apoptosis (Bax -/- /Bak -/- cells), necroptosis (Ripk1 -/- , Ripk3 -/- , or Mlkl -/- cells), ferroptosis (Gpx4 -/- cells), or autophagy (Atg3 -/- , Atg5 -/- , Atg7 -/- , or Sqstm1 -/- cells). We found JTC801 to induce a pH-dependent form cell death (alkaliptosis) in cancer cells but not normal cells (hepatocytes, bone marrow CD34 + progenitor cells, peripheral blood mononuclear cells, or dermal fibroblasts) or healthy tissues of C57BL/6 mice. JTC801 induced alkaliptosis in cancer cells by activating NF-κB, which repressed expression of the carbonic anhydrase 9 gene (CA9), whose product regulates pH balance in cells. In analyses of Cancer Genome Atlas data and tissue microarrays, we associated increased tumor level of CA9 mRNA or protein with shorter survival times of patients with pancreatic, kidney, or lung cancers. Knockdown of CA9 reduced the protective effects of NF-κB inhibition on JTC801-induced cell death and intracellular alkalinization in PANC1 and MiaPaCa2 cell lines. Oral administration of JTC801 inhibited growth of xenograft tumors (from PANC1, MiaPaCa2, SK-MEL-28, PC-3, 786-0, SF-295, HCT116, OV-CAR3, and HuH7 cells), orthotropic tumors (from KPC cells), lung metastases (from KPC cells) of mice, and slowed growth of tumors in KCH mice. In a screen of agents that interact with GPCR pathways, we found JTC801 to induce pH-dependent cell death (alkaliptosis) specifically in cancer cells such as PDAC cells, by reducing expression of CA9. Levels of CA9 are increased in human cancer tissues. JTC801 might be developed for treatment of

  4. Bacteria and viruses modulate FcεRI-dependent mast cell activity 

    Directory of Open Access Journals (Sweden)

    Aleksandra Słodka

    2013-03-01

    Full Text Available Undoubtedly, mast cells play a central role in allergic processes. Specific allergen cross-linking of IgE bound to the high affinity receptors (FcεRI on the mast cell surface leads to the release of preformed mediators and newly synthesized mediators, i.e. metabolites of arachidonic acid and cytokines. More and more data indicate that bacteria and viruses can influence FcεRI-dependent mast cell activation. Some bacterial and viral components can reduce the surface expression of FcεRI. There are also findings that ligation of Toll-like receptors (TLRs by bacterial or viral antigens can affect IgE-dependent mast cell degranulation and preformed mediator release as well as eicosanoid production. The synergistic interaction of TLR ligands and allergen can also modify cytokine synthesis by mast cells stimulated via FcεRI. Moreover, data suggest that specific IgE for bacterial or viral antigens can influence mast cell activity. What is more, some bacterial and viral components or some endogenous proteins produced during viral infection can act as superantigens by interacting with the VH3 domain of IgE. All these observations indicate that bacterial and viral infections modify the course of allergic diseases by affecting FcεRI-dependent mast cell activation. 

  5. A PKA survival pathway inhibited by DPT-PKI, a new specific cell permeable PKA inhibitor, is induced by T. annulata in parasitized B-lymphocytes.

    Science.gov (United States)

    Guergnon, Julien; Dessauge, Frederic; Traincard, François; Cayla, Xavier; Rebollo, Angelita; Bost, Pierre Etienne; Langsley, Gordon; Garcia, Alphonse

    2006-08-01

    T. annulata, an intracellular pathogenic parasite of the Aplicomplexa protozoan family infects bovine B-lymphocytes and macrophages. Parasitized cells that become transformed survive and proliferate independently of exogenous growth factors. In the present study, we used the isogenic non parasitized BL3 and parasitized TBL3 B cell lines, as a model to evaluate the contribution of two-major PI3-K- and PKA-dependent anti-apoptotic pathways in the survival of T. annulata parasitized B lymphocytes. We found that T. annulata increases PKA activity, induces over-expression of the catalytic subunit and down-regulates the pro-survival phosphorylation state of Akt/PKB. Consistent with a role of PKA activation in survival, two pharmacological inhibitors H89 and KT5720 ablate PKA-dependent survival of parasitized cells. To specifically inhibit PKA pro-survival pathways we linked the DPTsh1 peptide shuttle sequence to PKI(5-24) and we generated DPT-PKI, a cell permeable PKI. DPT-PKI specifically inhibited PKA activity in bovine cell extracts and, as expected, also inhibited the PKA-dependent survival of T. annulata parasitized TBL3 cells. Thus, parasite-dependent constitutive activation of PKA in TBL3 cells generates an anti-apoptotic pathway that can protect T. annulata-infected B cells from apoptosis. These results also indicate that DPT-PKI could be a powerful tool to inhibit PKA pathways in other cell types.

  6. Multiply gapped density of states in a normal metal in contact with a superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Reutlinger, Johannes; Belzig, Wolfgang [Department of Physics, University of Konstanz, 78457 Konstanz (Germany); Nazarov, Yuli V. [Kavli Institute of Nanoscience Delft, Delft University of Technology, 2628 CJ Delft (Netherlands); Glazman, Leonid I. [Department of Physics, Yale University, New Haven CT 06511-8499 (United States)

    2012-07-01

    The spectral properties of a normal metal adjacent to a superconductor are strongly dependent on the characteristic mesoscopic energy scale - the Thouless energy E{sub Th} - and the strength of the connection. In this work, we predict that the local density of states (LDOS), besides the well know minigap {proportional_to}E{sub Th}, can exhibit a multiple gap structure, which strongly depends on the type of the contact. For ballistic contacts we calculate these secondary gaps analytically in the framework of quantum circuit theory of mesoscopic transport. The secondary gaps are absent in the case of tunnel contacts. In the general case the equations are solved numerically for more realistic contacts, like for example diffusive connectors or dirty interfaces, which are characterized by continuous distributions of transmission eigenvalues between 0 and 1. We find that the gap vanishes in these cases, but the density of states is still suppressed around the superconducting gap edge. Distribution functions with a stronger weight at higher transmissions can be modeled through asymmetric ballistic double junctions, which even exhibit multiple gaps. Such spectral signatures are fundamental to disordered nanoscopic conductors and experimentally accessible.

  7. State densities and spectrum fluctuations: Information propagation in complex nuclei

    International Nuclear Information System (INIS)

    French, J.B.; Kota, V.K.B.

    1988-01-01

    At excitation energies in nuclei where the state density is unambiguously defined there is a sharp separation between the smoothed spectrum (which defines the density) and fluctuations about it which have recently been studied with a view to understanding some aspects of quantum chaos. We briefly review these two complementary subjects, paying special attention to: the role of the effective interaction in determining the density; the calculation of interacting-particle state and level densities, and of expectation values of interesting operators; the information about the effective nucleon-nucleon interaction which is carried both by the density and the fluctuations. 28 refs., 1 fig

  8. Collagen Matrix Density Drives the Metabolic Shift in Breast Cancer Cells

    Directory of Open Access Journals (Sweden)

    Brett A. Morris

    2016-11-01

    Full Text Available Increased breast density attributed to collagen I deposition is associated with a 4–6 fold increased risk of developing breast cancer. Here, we assessed cellular metabolic reprogramming of mammary carcinoma cells in response to increased collagen matrix density using an in vitro 3D model. Our initial observations demonstrated changes in functional metabolism in both normal mammary epithelial cells and mammary carcinoma cells in response to changes in matrix density. Further, mammary carcinoma cells grown in high density collagen matrices displayed decreased oxygen consumption and glucose metabolism via the tricarboxylic acid (TCA cycle compared to cells cultured in low density matrices. Despite decreased glucose entry into the TCA cycle, levels of glucose uptake, cell viability, and ROS were not different between high and low density matrices. Interestingly, under high density conditions the contribution of glutamine as a fuel source to drive the TCA cycle was significantly enhanced. These alterations in functional metabolism mirrored significant changes in the expression of metabolic genes involved in glycolysis, oxidative phosphorylation, and the serine synthesis pathway. This study highlights the broad importance of the collagen microenvironment to cellular expression profiles, and shows that changes in density of the collagen microenvironment can modulate metabolic shifts of cancer cells.

  9. Differential Activity of Voltage- and Ca2+-Dependent Potassium Channels in Leukemic T Cell Lines: Jurkat Cells Represent an Exceptional Case

    Directory of Open Access Journals (Sweden)

    Salvador Valle-Reyes

    2018-05-01

    Full Text Available Activation of resting T cells relies on sustained Ca2+ influx across the plasma membrane, which in turn depends on the functional expression of potassium channels, whose activity repolarizes the membrane potential. Depending on the T-cells subset, upon activation the expression of Ca2+- or voltage-activated K+ channels, KCa or Kv, is up-regulated. In this study, by means of patch-clamp technique in the whole cell mode, we have studied in detail the characteristics of Kv and KCa currents in resting and activated human T cells, the only well explored human T-leukemic cell line Jurkat, and two additional human leukemic T cell lines, CEM and MOLT-3. Voltage dependence of activation and inactivation of Kv1.3 current were shifted up to by 15 mV to more negative potentials upon a prolonged incubation in the whole cell mode and displayed little difference at a stable state in all cell lines but CEM, where the activation curve was biphasic, with a high and low potential components. In Jurkat, KCa currents were dominated by apamine-sensitive KCa2.2 channels, whereas only KCa3.1 current was detected in healthy T and leukemic CEM and MOLT-3 cells. Despite a high proliferation potential of Jurkat cells, Kv and KCa currents were unexpectedly small, more than 10-fold lesser as compared to activated healthy human T cells, CEM and MOLT-3, which displayed characteristic Kv1.3high:KCa3.1high phenotype. Our results suggest that Jurkat cells represent perhaps a singular case and call for more extensive studies on primary leukemic T cell lines as well as a verification of the therapeutic potential of specific KCa3.1 blockers to combat acute lymphoblastic T leukemias.

  10. Control of anode supported SOFCs (solid oxide fuel cells): Part I. mathematical modeling and state estimation within one cell

    International Nuclear Information System (INIS)

    Amedi, Hamid Reza; Bazooyar, Bahamin; Pishvaie, Mahmoud Reza

    2015-01-01

    In this paper, a 3-dimensional mathematical model for one cell of an anode-supported SOFC (solid oxide fuel cells) is presented. The model is derived from the partial differential equations representing the conservation laws of ionic and electronic charges, mass, energy, and momentum. The model is implemented to fully characterize the steady state operation of the cell with countercurrent flow pattern of fuel and air. The model is also used for the comparison of countercurrent with concurrent flow patterns in terms of thermal stress (temperature distribution) and quality of operation (current density). Results reveal that the steady-state cell performance curve and output of simulations qualitatively match experimental data of the literature. Results also demonstrate that countercurrent flow pattern leads to an even distribution of temperature, more uniform current density along the cell and thus is more enduring and superior to the concurrent flow pattern. Afterward, the thorough 3-dimensional model is used for state estimation instead of a real cell. To estimate states, the model is simplified and changed to a 1-dimensional model along flow streams. This simplified model includes uncertainty (because of simplifying assumptions of the model), noise, and disturbance (because of measurements). The behaviors of extended and ensemble Kalman filter as an observer are evaluated in terms of estimating the states and filtering the noises. Results demonstrate that, like extended Kalman filter, ensemble Kalman filter properly estimates the states with 20 sets. - Highlights: • A 3-dimensional model for one cell of SOFC (solid oxide fuel cells) is presented. • Higher voltages and thermal stress in countercurrent than concurrent flow pattern. • State estimation of the cell is examined by ensemble and extended Kalman filters. • Ensemble with 20 sets is as good as extended Kalman filter.

  11. Programmed Death-1 expression on Epstein Barr virus specific CD8+ T cells varies by stage of infection, epitope specificity, and T-cell receptor usage.

    Directory of Open Access Journals (Sweden)

    Thomas C Greenough

    Full Text Available BACKGROUND: Programmed Death-1 (PD-1 is an inhibitory member of the CD28 family of molecules expressed on CD8+ T cells in response to antigenic stimulation. To better understand the role of PD-1 in antiviral immunity we examined the expression of PD-1 on Epstein-Barr virus (EBV epitope-specific CD8+ T cells during acute infectious mononucleosis (AIM and convalescence. METHODOLOGY/PRINCIPAL FINDINGS: Using flow cytometry, we observed higher frequencies of EBV-specific CD8+ T cells and higher intensity of PD-1 expression on EBV-specific CD8+ T cells during AIM than during convalescence. PD-1 expression during AIM directly correlated with viral load and with the subsequent degree of CD8+ T cell contraction in convalescence. Consistent differences in PD-1 expression were observed between CD8+ T cells with specificity for two different EBV lytic antigen epitopes. Similar differences were observed in the degree to which PD-1 was upregulated on these epitope-specific CD8+ T cells following peptide stimulation in vitro. EBV epitope-specific CD8+ T cell proliferative responses to peptide stimulation were diminished during AIM regardless of PD-1 expression and were unaffected by blocking PD-1 interactions with PD-L1. Significant variability in PD-1 expression was observed on EBV epitope-specific CD8+ T cell subsets defined by V-beta usage. CONCLUSIONS/SIGNIFICANCE: These observations suggest that PD-1 expression is not only dependent on the degree of antigen presentation, but also on undefined characteristics of the responding cell that segregate with epitope specificity and V-beta usage.

  12. Density dependence of SOL power width in ASDEX upgrade L-Mode

    Directory of Open Access Journals (Sweden)

    B. Sieglin

    2017-08-01

    A recent study [4] with an open divertor configuration found an asymmetry of the power fall-off length between inner and outer target with a smaller power fall-off length λq,i on the inner divertor target. Measurements with a closed divertor configuration find a similar asymmetry for low recycling divertor conditions. It is found, in the experiment, that the in/out asymmetry λq,i/λq,o is strongly increasing with increasing density. Most notably the heat flux density at the inner divertor target is reducing with increasing λq,i whilst the total power onto each divertor target stays constant. It is found that λq,o exhibits no significant density dependence for hydrogen and deuterium but increases with about the square root of the electron density for helium. The difference between H,D and He could be due to the different recycling behaviour in the divertor. These findings may help current modelling attempts to parametrize the density dependence of the widening of the power channel and thus allow for detailed comparison to both divertor effects like recycling or increased upstream SOL cross field transport.

  13. Specific insulin binding in bovine chromaffin cells; demonstration of preferential binding to adrenalin-storing cells

    International Nuclear Information System (INIS)

    Serck-Hanssen, G.; Soevik, O.

    1987-01-01

    Insulin binding was studied in subpopulations of bovine chromaffin cells enriched in adrenalin-producing cells (A-cells) or noradrenalin-producing cells (NA-cells). Binding of 125 I-insulin was carried out at 15 0 C for 3 hrs in the absence or presence of excess unlabeled hormone. Four fractions of cells were obtained by centrifugation on a stepwise bovine serum albumin gradient. The four fractions were all shown to bind insulin in a specific manner and the highest binding was measured in the cell layers of higher densities, containing mainly A-cells. The difference in binding of insulin to the four subpopulations of chromaffin cells seemed to be related to differences in numbers of receptors as opposed to receptor affinities. The authors conclude that bovine chromaffin cells possess high affinity binding sites for insulin and that these binding sites are mainly confined to A-cells. 24 references, 2 figures, 1 table

  14. Self-consistent DFT +U method for real-space time-dependent density functional theory calculations

    Science.gov (United States)

    Tancogne-Dejean, Nicolas; Oliveira, Micael J. T.; Rubio, Angel

    2017-12-01

    We implemented various DFT+U schemes, including the Agapito, Curtarolo, and Buongiorno Nardelli functional (ACBN0) self-consistent density-functional version of the DFT +U method [Phys. Rev. X 5, 011006 (2015), 10.1103/PhysRevX.5.011006] within the massively parallel real-space time-dependent density functional theory (TDDFT) code octopus. We further extended the method to the case of the calculation of response functions with real-time TDDFT+U and to the description of noncollinear spin systems. The implementation is tested by investigating the ground-state and optical properties of various transition-metal oxides, bulk topological insulators, and molecules. Our results are found to be in good agreement with previously published results for both the electronic band structure and structural properties. The self-consistent calculated values of U and J are also in good agreement with the values commonly used in the literature. We found that the time-dependent extension of the self-consistent DFT+U method yields improved optical properties when compared to the empirical TDDFT+U scheme. This work thus opens a different theoretical framework to address the nonequilibrium properties of correlated systems.

  15. Isoscalar giant resonances and Landau parameters with density-dependent effective interactions

    International Nuclear Information System (INIS)

    Kohno, Michio; Ando, Kazuhiko

    1979-01-01

    Discussion is given on the relations between the Landau parameters and the isoscalar giant (quadrupole- and monopole-) resonance energies by using general density-dependent interactions. In the limit of infinite nuclear matter, the isoscalar giant quadrupole energy is shown to depend not only on the effective mass but also on the Landau parameter F 2 . Collective energies of the isoscalar giant resonances are calculated for 16 O and 40 Ca with four different effective interactions, G-0, B1, SII and SV, by using the scaling- and constrained Hartree-Fock-methods. It is shown that the dependence of the collective energies on the effective interactions is essentially determined by the Landau parameters. The G-0 force is found to be most successful in reproducing the giant resonance energies. Validity of the RPA-moment theorems is examined for the case of local density-dependent interactions. (author)

  16. Density increment and decreased survival of rat red blood cells induced by cadmium

    International Nuclear Information System (INIS)

    Kunimoto, M.; Miura, T.

    1986-01-01

    Male Wistar rats were injected with CdCl 2 subcutaneously to examine in vivo effects of Cd on density and survival of red blood cells. During the 7 days after administration of 1.0 mg Cd/kg, the following sequence of events occurred: (1) a progressive increase in the amount of more dense red blood cells concomitant with a decrease in that of light red blood cells from the first to the third day; (2) an increase in the spleen weight at the third day; (3) a decrease in the hematocrit value and an increase in the amount of light red blood cells at the fifth day; and (4) a recovery of the hematocrit value at the seventh day. Five days after administration, the hematocrit value decreased in a dose-dependent mode and the decrease was significant at the 1% level at 1.0 and 1.5 mg Cd/kg. A highly significant splenomegaly was also observed at 0.5 to 1.5 mg Cd/kg. In order to label red blood cells in vivo, [ 3 H] diisopropylfluorophosphate ([ 3 H]DFP) was injected into rats. At Day 11, Cd at either 0.5 or 1.0 mg/kg was administered to [ 3 H]DFP-prelabeled animals. Cd administration accelerated 3 H-labeled red cell clearance from the blood. Six days after Cd administration, the radioactivity of red blood cells was 76 and 68% of the control at 0.5 and 1.0 mg Cd/kg, respectively. In vitro treatment of rat red density and accelerated in vivo clearance of red blood cells from the recipient circulation. These results show that Cd at low dose can cause anemia by increasing red cell density and by accelerating red cell sequestration, presumably in the spleen

  17. Haematopoietic depletion in vaccine-induced neonatal pancytopenia depends on both the titre and specificity of alloantibody and levels of MHC I expression.

    Science.gov (United States)

    Bell, Charlotte R; MacHugh, Niall D; Connelley, Timothy K; Degnan, Kathryn; Morrison, W Ivan

    2015-07-09

    Bovine Neonatal Pancytopenia (BNP) is a disease of calves characterised by haematopoietic depletion, mediated by ingestion of alloantibodies in colostrum. It has been linked epidemiologically to vaccination of the dams of affected calves with a particular vaccine (Pregsure) containing a novel adjuvant. Evidence suggests that BNP-alloantibodies are directed against MHC I molecules, induced by contaminant bovine cellular material from Madin-Darby Bovine Kidney (MDBK) cells used in the vaccine's production. We aimed to investigate the specificity of BNP-alloantibody for bovine MHC I alleles, particularly those expressed by MDBK cells, and whether depletion of particular cell types is due to differential MHC I expression levels. A complement-mediated cytotoxicity assay was used to assess functional serum alloantibody titres in BNP-dams, Pregsure-vaccinated dams with healthy calves, cows vaccinated with an alternative product and unvaccinated controls. Alloantibody specificity was investigated using transfected mouse lines expressing the individual MHC I alleles identified from MDBK cells and MHC I-defined bovine leukocyte lines. All BNP-dams and 50% of Pregsure-vaccinated cows were shown to have MDBK-MHC I specific alloantibodies, which cross-reacted to varying degrees with other MHC I genotypes. MHC I expression levels on different blood cell types, assessed by flow cytometry, were found to correlate with levels of alloantibody-mediated damage in vitro and in vivo. Alloantibody-killed bone marrow cells were shown to express higher levels of MHC I than undamaged cells. The results provide evidence that MHC I-specific alloantibodies play a dominant role in the pathogenesis of BNP. Haematopoietic depletion was shown to be dependent on the titre and specificity of alloantibody produced by individual cows and the density of surface MHC I expression by different cell types. Collectively, the results support the hypothesis that MHC I molecules originating from MDBK cells

  18. Parameter dependence and outcome dependence in dynamical models for state vector reduction

    International Nuclear Information System (INIS)

    Ghirardi, G.C.; Grassi, R.; Butterfield, J.; Fleming, G.N.

    1993-01-01

    The authors apply the distinction between parameter independence and outcome independence to the linear and nonlinear models of a recent nonrelativistic theory of continuous state vector reduction. It is shown that in the nonlinear model there is a set of realizations of the stochastic process that drives the state vector reduction for which parameter independence is violated for parallel spin components in the EPR-Bohm setup. Such a set has an appreciable probability of occurrence (∼ 1/2). On the other hand, the linear model exhibits only extremely small parameter dependence effects. Some specific features of the models are investigated and it is recalled that, as has been pointed out recently, to be able to speak of definite outcomes (or equivalently of possessed objective elements of reality) at finite times, the criteria for their attribution to physical systems must be slightly changed. The concluding section is devoted to a detailed discussion of the difficulties met when attempting to take, as a starting point for the formulation of a relativistic theory, a nonrelativistic scheme which exhibits parameter dependence. Here the authors derive a theorem which identifies the precise sense in which the occurrence of parameter dependence forbids a genuinely relativistic generalization. Finally, the authors show how the appreciable parameter dependence of the nonlinear model gives rise to problems with relativity, while the extremely weak parameter dependence of the linear model does not give rise to any difficulty, provided the appropriate criteria for the attribution of definite outcomes are taken into account. 19 refs

  19. Multireference Density Functional Theory with Generalized Auxiliary Systems for Ground and Excited States.

    Science.gov (United States)

    Chen, Zehua; Zhang, Du; Jin, Ye; Yang, Yang; Su, Neil Qiang; Yang, Weitao

    2017-09-21

    To describe static correlation, we develop a new approach to density functional theory (DFT), which uses a generalized auxiliary system that is of a different symmetry, such as particle number or spin, from that of the physical system. The total energy of the physical system consists of two parts: the energy of the auxiliary system, which is determined with a chosen density functional approximation (DFA), and the excitation energy from an approximate linear response theory that restores the symmetry to that of the physical system, thus rigorously leading to a multideterminant description of the physical system. The electron density of the physical system is different from that of the auxiliary system and is uniquely determined from the functional derivative of the total energy with respect to the external potential. Our energy functional is thus an implicit functional of the physical system density, but an explicit functional of the auxiliary system density. We show that the total energy minimum and stationary states, describing the ground and excited states of the physical system, can be obtained by a self-consistent optimization with respect to the explicit variable, the generalized Kohn-Sham noninteracting density matrix. We have developed the generalized optimized effective potential method for the self-consistent optimization. Among options of the auxiliary system and the associated linear response theory, reformulated versions of the particle-particle random phase approximation (pp-RPA) and the spin-flip time-dependent density functional theory (SF-TDDFT) are selected for illustration of principle. Numerical results show that our multireference DFT successfully describes static correlation in bond dissociation and double bond rotation.

  20. Nuclear level density parameter 's dependence on angular momentum

    International Nuclear Information System (INIS)

    Aggarwal, Mamta; Kailas, S.

    2009-01-01

    Nuclear level densities represent a very important ingredient in the statistical Model calculations of nuclear reaction cross sections and help to understand the microscopic features of the excited nuclei. Most of the earlier experimental nuclear level density measurements are confined to low excitation energy and low spin region. A recent experimental investigation of nuclear level densities in high excitation energy and angular momentum domain with some interesting results on inverse level density parameter's dependence on angular momentum in the region around Z=50 has motivated us to study and analyse these experimental results in a microscopic theoretical framework. In the experiment, heavy ion fusion reactions are used to populate the excited and rotating nuclei and measured the α particle evaporation spectra in coincidence with ray multiplicity. Residual nuclei are in the range of Z R 48-55 with excitation energy range 30 to 40 MeV and angular momentum in 10 to 25. The inverse level density parameter K is found to be in the range of 9.0 - 10.5 with some exceptions

  1. Time-dependent density-functional theory in massively parallel computer architectures: the OCTOPUS project.

    Science.gov (United States)

    Andrade, Xavier; Alberdi-Rodriguez, Joseba; Strubbe, David A; Oliveira, Micael J T; Nogueira, Fernando; Castro, Alberto; Muguerza, Javier; Arruabarrena, Agustin; Louie, Steven G; Aspuru-Guzik, Alán; Rubio, Angel; Marques, Miguel A L

    2012-06-13

    Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn-Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn-Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures.

  2. Time-dependent density-functional theory in massively parallel computer architectures: the octopus project

    Science.gov (United States)

    Andrade, Xavier; Alberdi-Rodriguez, Joseba; Strubbe, David A.; Oliveira, Micael J. T.; Nogueira, Fernando; Castro, Alberto; Muguerza, Javier; Arruabarrena, Agustin; Louie, Steven G.; Aspuru-Guzik, Alán; Rubio, Angel; Marques, Miguel A. L.

    2012-06-01

    Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn-Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn-Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures.

  3. Time-dependent density-functional theory in massively parallel computer architectures: the octopus project

    International Nuclear Information System (INIS)

    Andrade, Xavier; Aspuru-Guzik, Alán; Alberdi-Rodriguez, Joseba; Rubio, Angel; Strubbe, David A; Louie, Steven G; Oliveira, Micael J T; Nogueira, Fernando; Castro, Alberto; Muguerza, Javier; Arruabarrena, Agustin; Marques, Miguel A L

    2012-01-01

    Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn-Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn-Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures. (topical review)

  4. Using Regularization to Infer Cell Line Specificity in Logical Network Models of Signaling Pathways

    Directory of Open Access Journals (Sweden)

    Sébastien De Landtsheer

    2018-05-01

    Full Text Available Understanding the functional properties of cells of different origins is a long-standing challenge of personalized medicine. Especially in cancer, the high heterogeneity observed in patients slows down the development of effective cures. The molecular differences between cell types or between healthy and diseased cellular states are usually determined by the wiring of regulatory networks. Understanding these molecular and cellular differences at the systems level would improve patient stratification and facilitate the design of rational intervention strategies. Models of cellular regulatory networks frequently make weak assumptions about the distribution of model parameters across cell types or patients. These assumptions are usually expressed in the form of regularization of the objective function of the optimization problem. We propose a new method of regularization for network models of signaling pathways based on the local density of the inferred parameter values within the parameter space. Our method reduces the complexity of models by creating groups of cell line-specific parameters which can then be optimized together. We demonstrate the use of our method by recovering the correct topology and inferring accurate values of the parameters of a small synthetic model. To show the value of our method in a realistic setting, we re-analyze a recently published phosphoproteomic dataset from a panel of 14 colon cancer cell lines. We conclude that our method efficiently reduces model complexity and helps recovering context-specific regulatory information.

  5. First-principles analysis of the Raman spectrum of vitreous silica: comparison with the vibrational density of states

    International Nuclear Information System (INIS)

    Umari, P; Pasquarello, Alfredo

    2003-01-01

    The HH and HV Raman spectra of vitreous silica are calculated from first principles for a model structure consisting of a disordered network of corner-sharing tetrahedra, for which the vibrational properties were obtained previously. We analyse the contribution of specific atomic motions to the Raman spectra and perform a detailed comparison with respect to the vibrational density of states. We find that the HV spectrum closely resembles the vibrational density of states. By comparison, the HH spectrum shows significant differences and arises almost exclusively from oxygen vibrations

  6. First-principles analysis of the Raman spectrum of vitreous silica: comparison with the vibrational density of states

    Energy Technology Data Exchange (ETDEWEB)

    Umari, P; Pasquarello, Alfredo [Institut de Theorie des Phenomenes Physiques (ITP), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Institut Romand de Recherche Numerique en Physique des Materiaux (IRRMA), CH-1015 Lausanne (Switzerland)

    2003-04-30

    The HH and HV Raman spectra of vitreous silica are calculated from first principles for a model structure consisting of a disordered network of corner-sharing tetrahedra, for which the vibrational properties were obtained previously. We analyse the contribution of specific atomic motions to the Raman spectra and perform a detailed comparison with respect to the vibrational density of states. We find that the HV spectrum closely resembles the vibrational density of states. By comparison, the HH spectrum shows significant differences and arises almost exclusively from oxygen vibrations.

  7. Density-dependent effects on physical condition and reproduction in North American elk: an experimental test.

    Science.gov (United States)

    Kelley M. Stewart; R. Terry Bowyer; Brian L. Dick; Bruce K. Johnson; John G. Kie

    2005-01-01

    Density dependence plays a key role in life-history characteristics and population ecology of large, herbivorous mammals. We designed a manipulative experiment to test hypotheses relating effects of density-dependent mechanisms on physical condition and fecundity of North American elk (Cervus elaphus) by creating populations at low and high density...

  8. Generation of Patient-Specific induced Pluripotent Stem Cell from Peripheral Blood Mononuclear Cells by Sendai Reprogramming Vectors.

    Science.gov (United States)

    Quintana-Bustamante, Oscar; Segovia, Jose C

    2016-01-01

    Induced pluripotent stem cells (iPSC) technology has changed preclinical research since their generation was described by Shinya Yamanaka in 2006. iPSCs are derived from somatic cells after being reprogrammed back to an embryonic state by specific combination of reprogramming factors. These reprogrammed cells resemble all the characteristic of embryonic stem cells (ESC). The reprogramming technology is even more valuable to research diseases biology and treatment by opening gene and cell therapies in own patient's iPSC. Patient-specific iPSC can be generated from a large variety of patient cells by any of the myriad of reprogramming platforms described. Here, we describe the generation of patient-specific iPSC from patient peripheral blood mononuclear cells by Sendai Reprogramming vectors.

  9. How important is self-consistency for the dDsC density dependent dispersion correction?

    Energy Technology Data Exchange (ETDEWEB)

    Brémond, Éric; Corminboeuf, Clémence, E-mail: clemence.corminboeuf@epfl.ch [Laboratory for Computational Molecular Design, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Golubev, Nikolay [Laboratory for Computational Molecular Design, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Department of Chemistry, M. V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Steinmann, Stephan N., E-mail: sns25@duke.edu [Laboratory for Computational Molecular Design, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States)

    2014-05-14

    The treatment of dispersion interactions is ubiquitous but computationally demanding for seamless ab initio approaches. A highly popular and simple remedy consists in correcting for the missing interactions a posteriori by adding an attractive energy term summed over all atom pairs to standard density functional approximations. These corrections were originally based on atom pairwise parameters and, hence, had a strong touch of empiricism. To overcome such limitations, we recently proposed a robust system-dependent dispersion correction, dDsC, that is computed from the electron density and that provides a balanced description of both weak inter- and intramolecular interactions. From the theoretical point of view and for the sake of increasing reliability, we here verify if the self-consistent implementation of dDsC impacts ground-state properties such as interaction energies, electron density, dipole moments, geometries, and harmonic frequencies. In addition, we investigate the suitability of the a posteriori scheme for molecular dynamics simulations, for which the analysis of the energy conservation constitutes a challenging tests. Our study demonstrates that the post-SCF approach in an excellent approximation.

  10. Statistical mechanics of Roskilde liquids: configurational adiabats, specific heat contours, and density dependence of the scaling exponent.

    Science.gov (United States)

    Bailey, Nicholas P; Bøhling, Lasse; Veldhorst, Arno A; Schrøder, Thomas B; Dyre, Jeppe C

    2013-11-14

    We derive exact results for the rate of change of thermodynamic quantities, in particular, the configurational specific heat at constant volume, CV, along configurational adiabats (curves of constant excess entropy Sex). Such curves are designated isomorphs for so-called Roskilde liquids, in view of the invariance of various structural and dynamical quantities along them. The slope of the isomorphs in a double logarithmic representation of the density-temperature phase diagram, γ, can be interpreted as one third of an effective inverse power-law potential exponent. We show that in liquids where γ increases (decreases) with density, the contours of CV have smaller (larger) slope than configurational adiabats. We clarify also the connection between γ and the pair potential. A fluctuation formula for the slope of the CV-contours is derived. The theoretical results are supported with data from computer simulations of two systems, the Lennard-Jones fluid, and the Girifalco fluid. The sign of dγ∕dρ is thus a third key parameter in characterizing Roskilde liquids, after γ and the virial-potential energy correlation coefficient R. To go beyond isomorph theory we compare invariance of a dynamical quantity, the self-diffusion coefficient, along adiabats and CV-contours, finding it more invariant along adiabats.

  11. Anorexia Reduces GFAP+ Cell Density in the Rat Hippocampus.

    Science.gov (United States)

    Reyes-Haro, Daniel; Labrada-Moncada, Francisco Emmanuel; Varman, Durairaj Ragu; Krüger, Janina; Morales, Teresa; Miledi, Ricardo; Martínez-Torres, Ataúlfo

    2016-01-01

    Anorexia nervosa is an eating disorder observed primarily in young women. The neurobiology of the disorder is unknown but recently magnetic resonance imaging showed a volume reduction of the hippocampus in anorexic patients. Dehydration-induced anorexia (DIA) is a murine model that mimics core features of this disorder, including severe weight loss due to voluntary reduction in food intake. The energy supply to the brain is mediated by astrocytes, but whether their density is compromised by anorexia is unknown. Thus, the aim of this study was to estimate GFAP+ cell density in the main regions of the hippocampus (CA1, CA2, CA3, and dentate gyrus) in the DIA model. Our results showed that GFAP+ cell density was significantly reduced (~20%) in all regions of the hippocampus, except in CA1. Interestingly, DIA significantly reduced the GFAP+ cells/nuclei ratio in CA2 (-23%) and dentate gyrus (-48%). The reduction of GFAP+ cell density was in agreement with a lower expression of GFAP protein. Additionally, anorexia increased the expression of the intermediate filaments vimentin and nestin. Accordingly, anorexia increased the number of reactive astrocytes in CA2 and dentate gyrus more than twofold. We conclude that anorexia reduces the hippocampal GFAP+ cell density and increases vimentin and nestin expression.

  12. Evolution with Composition of the d-Band Density of States at the Fermi Level in Highly Spin Polarized Co1-xFexS2

    Science.gov (United States)

    Kuhns, P. L.; Hoch, M. J. R.; Reyes, A. P.; Moulton, W. G.; Wang, L.; Leighton, C.

    2006-04-01

    Highly spin polarized (SP) and half-metallic ferromagnetic systems are of considerable current interest and of potential importance for spintronic applications. Recent work has demonstrated that Co1-xFexS2 is a highly polarized ferromagnet (FM) where the spin polarization can be tuned by alloy composition. Using Co59 FM-NMR as a probe, we have measured the low-temperature spin relaxation in this system in magnetic fields from 0 to 1.0 T for 0≤x≤0.3. The Co59 spin-lattice relaxation rates follow a linear T dependence. Analysis of the data, using expressions for a FM system, permits information to be obtained on the d-band density of states at the Fermi level. The results are compared with independent density of states values inferred from electronic specific heat measurements and band structure calculations. It is shown that FM-NMR can be an important method for investigating highly SP systems.

  13. Determining the Limiting Current Density of Vanadium Redox Flow Batteries

    Directory of Open Access Journals (Sweden)

    Jen-Yu Chen

    2014-09-01

    Full Text Available All-vanadium redox flow batteries (VRFBs are used as energy storage systems for intermittent renewable power sources. The performance of VRFBs depends on materials of key components and operating conditions, such as current density, electrolyte flow rate and electrolyte composition. Mass transfer overpotential is affected by the electrolyte flow rate and electrolyte composition, which is related to the limiting current density. In order to investigate the effect of operating conditions on mass transport overpotential, this study established a relationship between the limiting current density and operating conditions. First, electrolyte solutions with different states of charge were prepared and used for a single cell to obtain discharging polarization curves under various operating conditions. The experimental results were then analyzed and are discussed in this paper. Finally, this paper proposes a limiting current density as a function of operating conditions. The result helps predict the effect of operating condition on the cell performance in a mathematical model.

  14. HIV-1 Vif's Capacity To Manipulate the Cell Cycle Is Species Specific.

    Science.gov (United States)

    Evans, Edward L; Becker, Jordan T; Fricke, Stephanie L; Patel, Kishan; Sherer, Nathan M

    2018-04-01

    Cells derived from mice and other rodents exhibit profound blocks to HIV-1 virion production, reflecting species-specific incompatibilities between viral Tat and Rev proteins and essential host factors cyclin T1 (CCNT1) and exportin-1 (XPO1, also known as CRM1), respectively. To determine if mouse cell blocks other than CCNT1 and XPO1 affect HIV's postintegration stages, we studied HIV-1 NL4-3 gene expression in mouse NIH 3T3 cells modified to constitutively express HIV-1-compatible versions of CCNT1 and XPO1 (3T3.CX cells). 3T3.CX cells supported both Rev-independent and Rev-dependent viral gene expression and produced relatively robust levels of virus particles, confirming that CCNT1 and XPO1 represent the predominant blocks to these stages. Unexpectedly, however, 3T3.CX cells were remarkably resistant to virus-induced cytopathic effects observed in human cell lines, which we mapped to the viral protein Vif and its apparent species-specific capacity to induce G 2 /M cell cycle arrest. Vif was able to mediate rapid degradation of human APOBEC3G and the PPP2R5D regulatory B56 subunit of the PP2A phosphatase holoenzyme in mouse cells, thus demonstrating that Vif NL4-3 's modulation of the cell cycle can be functionally uncoupled from some of its other defined roles in CUL5-dependent protein degradation. Vif was also unable to induce G 2 /M cell cycle arrest in other nonhuman cell types, including cells derived from nonhuman primates, leading us to propose that one or more human-specific cofactors underpin Vif's ability to modulate the cell cycle. IMPORTANCE Cells derived from mice and other rodents exhibit profound blocks to HIV-1 replication, thus hindering the development of a low-cost small-animal model for studying HIV/AIDS. Here, we engineered otherwise-nonpermissive mouse cells to express HIV-1-compatible versions of two species-specific host dependency factors, cyclin T1 (CCNT1) and exportin-1 (XPO1) (3T3.CX cells). We show that 3T3.CX cells rescue HIV-1

  15. Rotating Hele-Shaw cell with a time-dependent angular velocity

    Science.gov (United States)

    Anjos, Pedro H. A.; Alvarez, Victor M. M.; Dias, Eduardo O.; Miranda, José A.

    2017-12-01

    Despite the large number of existing studies of viscous flows in rotating Hele-Shaw cells, most investigations analyze rotational motion with a constant angular velocity, under vanishing Reynolds number conditions in which inertial effects can be neglected. In this work, we examine the linear and weakly nonlinear dynamics of the interface between two immiscible fluids in a rotating Hele-Shaw cell, considering the action of a time-dependent angular velocity, and taking into account the contribution of inertia. By using a generalized Darcy's law, we derive a second-order mode-coupling equation which describes the time evolution of the interfacial perturbation amplitudes. For arbitrary values of viscosity and density ratios, and for a range of values of a rotational Reynolds number, we investigate how the time-dependent angular velocity and inertia affect the important finger competition events that traditionally arise in rotating Hele-Shaw flows.

  16. Changes in density of aluminium, lead and zinc melts dependent on temperature

    International Nuclear Information System (INIS)

    Kazachkov, S.P.; Kochegura, N.M.; Markovskij, E.A.

    1979-01-01

    Density of aluminium, lead and zinc in various aggregate states has been studied in a wide temperature range. The density of the above metals was found to manifest temperature hysteresis after melting and cyclic change at the temperature of melting and crystallization. These phenomena are in agreement with the Stuart model of liquid state

  17. Flagellum density regulates Proteus mirabilis swarmer cell motility in viscous environments.

    Science.gov (United States)

    Tuson, Hannah H; Copeland, Matthew F; Carey, Sonia; Sacotte, Ryan; Weibel, Douglas B

    2013-01-01

    Proteus mirabilis is an opportunistic pathogen that is frequently associated with urinary tract infections. In the lab, P. mirabilis cells become long and multinucleate and increase their number of flagella as they colonize agar surfaces during swarming. Swarming has been implicated in pathogenesis; however, it is unclear how energetically costly changes in P. mirabilis cell morphology translate into an advantage for adapting to environmental changes. We investigated two morphological changes that occur during swarming--increases in cell length and flagellum density--and discovered that an increase in the surface density of flagella enabled cells to translate rapidly through fluids of increasing viscosity; in contrast, cell length had a small effect on motility. We found that swarm cells had a surface density of flagella that was ∼5 times larger than that of vegetative cells and were motile in fluids with a viscosity that inhibits vegetative cell motility. To test the relationship between flagellum density and velocity, we overexpressed FlhD(4)C(2), the master regulator of the flagellar operon, in vegetative cells of P. mirabilis and found that increased flagellum density produced an increase in cell velocity. Our results establish a relationship between P. mirabilis flagellum density and cell motility in viscous environments that may be relevant to its adaptation during the infection of mammalian urinary tracts and movement in contact with indwelling catheters.

  18. Particle-hole state densities for statistical multi-step compound reactions

    International Nuclear Information System (INIS)

    Oblozinsky, P.

    1986-01-01

    An analytical relation is derived for the density of particle-hole bound states applying the equidistant-spacing approximation and the Darwin-Fowler statistical method. The Pauli exclusion principle as well as the finite depth of the potential well are taken into account. The set of densities needed for calculations of multi-step compound reactions is completed by deriving the densities of accessible final states for escape and damping. (orig.)

  19. Density of biogas digestate depending on temperature and composition.

    Science.gov (United States)

    Gerber, Mandy; Schneider, Nico

    2015-09-01

    Density is one of the most important physical properties of biogas digestate to ensure an optimal dimensioning and a precise design of biogas plant components like stirring devices, pumps and heat exchangers. In this study the density of biogas digestates with different compositions was measured using pycnometers at ambient pressure in a temperature range from 293.15 to 313.15K. The biogas digestates were taken from semi-continuous experiments, in which the marine microalga Nannochloropsis salina, corn silage and a mixture of both were used as feedstocks. The results show an increase of density with increasing total solid content and a decrease with increasing temperature. Three equations to calculate the density of biogas digestate were set up depending on temperature as well as on the total solid content, organic composition and elemental composition, respectively. All correlations show a relative deviation below 1% compared to experimental data. Copyright © 2015. Published by Elsevier Ltd.

  20. High volumetric power density, non-enzymatic, glucose fuel cells.

    Science.gov (United States)

    Oncescu, Vlad; Erickson, David

    2013-01-01

    The development of new implantable medical devices has been limited in the past by slow advances in lithium battery technology. Non-enzymatic glucose fuel cells are promising replacement candidates for lithium batteries because of good long-term stability and adequate power density. The devices developed to date however use an "oxygen depletion design" whereby the electrodes are stacked on top of each other leading to low volumetric power density and complicated fabrication protocols. Here we have developed a novel single-layer fuel cell with good performance (2 μW cm⁻²) and stability that can be integrated directly as a coating layer on large implantable devices, or stacked to obtain a high volumetric power density (over 16 μW cm⁻³). This represents the first demonstration of a low volume non-enzymatic fuel cell stack with high power density, greatly increasing the range of applications for non-enzymatic glucose fuel cells.

  1. Parity dependence of the nuclear level density at high excitation

    International Nuclear Information System (INIS)

    Rao, B.V.; Agrawal, H.M.

    1995-01-01

    The basic underlying assumption ρ(l+1, J)=ρ(l, J) in the level density function ρ(U, J, π) has been checked on the basis of high quality data available on individual resonance parameters (E 0 , Γ n , J π ) for s- and p-wave neutrons in contrast to the earlier analysis where information about p-wave resonance parameters was meagre. The missing level estimator based on the partial integration over a Porter-Thomas distribution of neutron reduced widths and the Dyson-Mehta Δ 3 statistic for the level spacing have been used to ascertain that the s- and p-wave resonance level spacings D(0) and D(1) are not in error because of spurious and missing levels. The present work does not validate the tacit assumption ρ(l+1, J)=ρ(l, J) and confirms that the level density depends upon parity at high excitation. The possible implications of the parity dependence of the level density on the results of statistical model calculations of nuclear reaction cross sections as well as on pre-compound emission have been emphasized. (orig.)

  2. Antigen-specific tolerance of human alpha1-antitrypsin induced by helper-dependent adenovirus.

    Science.gov (United States)

    Cerullo, V; McCormack, W; Seiler, M; Mane, V; Cela, R; Clarke, C; Rodgers, J R; Lee, B

    2007-12-01

    As efficient and less toxic virus-derived gene therapy vectors are developed, a pressing problem is to avoid immune response to the therapeutic gene product. Secreted therapeutic proteins potentially represent a special problem, as they are readily available to professional antigen-presenting cells throughout the body. Some studies suggest that immunity to serum proteins can be avoided in some mouse strains by using tissue-specific promoters. Here we show that expression of human alpha1-antitrypsin (AAT) was nonimmunogenic in the immune-responsive strain C3H/HeJ, when expressed from helper-dependent (HD) vectors using ubiquitous as well as tissue-specific promoters. Coadministration of less immunogenic HD vectors with an immunogenic first-generation vector failed to immunize, suggesting immune suppression rather than immune stealth. Indeed, mice primed with HD vectors were tolerant to immune challenge with hAAT emulsified in complete Freund's adjuvant. Such animals developed high-titer antibodies to coemulsified human serum albumin, showing that tolerance was antigen specific. AAT-specific T cell responses were depressed in tolerized animals, suggesting that tolerance affects both T and B cells. These results are consistent with models of high-dose tolerance of B cells and certain other suppressive mechanisms, and suggest that a high level of expression from HD vectors can be sufficient to induce specific immune tolerance to serum proteins.

  3. Advances in cell culture: anchorage dependence

    Science.gov (United States)

    Merten, Otto-Wilhelm

    2015-01-01

    Anchorage-dependent cells are of great interest for various biotechnological applications. (i) They represent a formidable production means of viruses for vaccination purposes at very large scales (in 1000–6000 l reactors) using microcarriers, and in the last decade many more novel viral vaccines have been developed using this production technology. (ii) With the advent of stem cells and their use/potential use in clinics for cell therapy and regenerative medicine purposes, the development of novel culture devices and technologies for adherent cells has accelerated greatly with a view to the large-scale expansion of these cells. Presently, the really scalable systems—microcarrier/microcarrier-clump cultures using stirred-tank reactors—for the expansion of stem cells are still in their infancy. Only laboratory scale reactors of maximally 2.5 l working volume have been evaluated because thorough knowledge and basic understanding of critical issues with respect to cell expansion while retaining pluripotency and differentiation potential, and the impact of the culture environment on stem cell fate, etc., are still lacking and require further studies. This article gives an overview on critical issues common to all cell culture systems for adherent cells as well as specifics for different types of stem cells in view of small- and large-scale cell expansion and production processes. PMID:25533097

  4. Specific heat of ceramic and single crystal MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Junod, A.; Wang, Y.; Bouquet, F.; Sheikin, I.; Toulemonde, P.; Eskildsen, M.R.; Eisterer, M.; Weber, H.W.; Lee, S.; Tajima, S

    2003-05-15

    The two-gap structure of MgB{sub 2} gives rise to unusual thermodynamic properties which depart markedly from the single-gap BCS model, both in their temperature- and field-dependence. We report measurements of the specific heat up to 16 T on ceramic and single crystal samples, which demonstrate these effects in bulk. The low-temperature mixed-state specific heat reveals a field-dependent anisotropy, and points to the existence of unusually large vortices, in agreement with local density-of-states measurements by scanning tunneling spectroscopy. It is finally shown that a suitable irradiation process nearly doubles H{sub c2} in the bulk.

  5. The redox state and the phosphorylation state of the mannitol-specific carrier of the E. coli phosphoenolpyruvate-dependent phosphotransferase system

    NARCIS (Netherlands)

    Robillard, G.T.; Pas, H.H.; Gage, D.; Elferink, M.G.L.

    1988-01-01

    This review summarizes the recent developments in identifying the activity-linked cysteine as one of the phosphorylation sites on the mannitol-specific EII of the E. coli phosphoenolpyruvate-dependent mannitol transport system. Two phosphorylation sites have been identified, one being the HPr/P-HPr

  6. Measuring the effective phonon density of states of a quantum dot in cavity quantum electrodynamics

    DEFF Research Database (Denmark)

    Madsen, Kristian Høeg; Nielsen, Per Kær; Kreiner-Møller, Asger

    2013-01-01

    We employ detuning-dependent decay-rate measurements of a quantum dot in a photonic-crystal cavity to study the influence of phonon dephasing in a solid-state quantum-electrodynamics experiment. The experimental data agree with a microscopic non-Markovian model accounting for dephasing from...... longitudinal acoustic phonons, and the analysis explains the difference between nonresonant cavity feeding in different nanocavities. From the comparison between experiment and theory we extract the effective phonon density of states experienced by the quantum dot in the nanocavity. This quantity determines...

  7. Efficient genome editing in hematopoietic stem cells with helper-dependent Ad5/35 vectors expressing site-specific endonucleases under microRNA regulation

    Directory of Open Access Journals (Sweden)

    Kamola Saydaminova

    Full Text Available Genome editing with site-specific endonucleases has implications for basic biomedical research as well as for gene therapy. We generated helper-dependent, capsid-modified adenovirus (HD-Ad5/35 vectors for zinc-finger nuclease (ZFN– or transcription activator-like effector nuclease (TALEN–mediated genome editing in human CD34+ hematopoietic stem cells (HSCs from mobilized adult donors. The production of these vectors required that ZFN and TALEN expression in HD-Ad5/35 producer 293-Cre cells was suppressed. To do this, we developed a microRNA (miRNA-based system for regulation of gene expression based on miRNA expression profiling of 293-Cre and CD34+ cells. Using miR-183-5p and miR-218-5p based regulation of transgene gene expression, we first produced an HD-Ad5/35 vector expressing a ZFN specific to the HIV coreceptor gene ccr5. We demonstrated that HD-Ad5/35.ZFNmiR vector conferred ccr5 knock out in primitive HSC (i.e., long-term culture initiating cells and NOD/SCID repopulating cells. The ccr5 gene disruption frequency achieved in engrafted HSCs found in the bone marrow of transplanted mice is clinically relevant for HIV therapy considering that these cells can give rise to multiple lineages, including all the lineages that represent targets and reservoirs for HIV. We produced a second HD-Ad5/35 vector expressing a TALEN targeting the DNase hypersensitivity region 2 (HS2 within the globin locus control region. This vector has potential for targeted gene correction in hemoglobinopathies. The miRNA regulated HD-Ad5/35 vector platform for expression of site-specific endonucleases has numerous advantages over currently used vectors as a tool for genome engineering of HSCs for therapeutic purposes.

  8. Dendritic cell maturation: functional specialization through signaling specificity and transcriptional programming.

    Science.gov (United States)

    Dalod, Marc; Chelbi, Rabie; Malissen, Bernard; Lawrence, Toby

    2014-05-16

    Dendritic cells (DC) are key regulators of both protective immune responses and tolerance to self-antigens. Soon after their discovery in lymphoid tissues by Steinman and Cohn, as cells with the unique ability to prime naïve antigen-specific T cells, it was realized that DC can exist in at least two distinctive states characterized by morphological, phenotypic and functional changes-this led to the description of DC maturation. It is now well appreciated that there are several subsets of DC in both lymphoid and non-lymphoid tissues of mammals, and these cells show remarkable functional specialization and specificity in their roles in tolerance and immunity. This review will focus on the specific characteristics of DC subsets and how their functional specialization may be regulated by distinctive gene expression programs and signaling responses in both steady-state and in the context of inflammation. In particular, we will highlight the common and distinctive genes and signaling pathways that are associated with the functional maturation of DC subsets. © 2014 The Authors.

  9. Dependences of Ultrasonic Parameters for Osteoporosis Diagnosis on Bone Mineral Density

    International Nuclear Information System (INIS)

    Hwang, Kyo Seung; Kim, Yoon Mi; Park, Jong Chan; Choi, Min Joo; Lee, Kang Il

    2012-01-01

    Quantitative ultrasound technologies for osteoporosis diagnosis measure ultrasonic parameters such as speed of sound(SOS) and normalized broadband ultrasound attenuation(nBUA) in the calcaneus (heel bone). In the present study, the dependences of SOS and nBUA on bone mineral density in the proximal femur with high risk of fracture were investigated by using 20 trabecular bone samples extracted from bovine femurs. SOS and nBUA in the femoral trabecular bone samples were measured by using a transverse transmission method with one matched pair of ultrasonic transducers with a center frequency of 1.0 MHz. SOS and nBUA measured in the 20 trabecular bone samples exhibited high Pearson's correlation coefficients (r) of r = 0.83 and 0.72 with apparent bone density, respectively. The multiple regression analysis with SOS and nBUA as independent variables and apparent bone density as a dependent variable showed that the correlation coefficient r = 0.85 of the multiple linear regression model was higher than those of the simple linear regression model with either parameter SOS or nBUA as an independent variable. These high linear correlations between the ultrasonic parameters and the bone density suggest that the ultrasonic parameters measured in the femur can be useful for predicting the femoral bone mineral density.

  10. Time-dependent quantum fluid density functional theory of hydrogen ...

    Indian Academy of Sciences (India)

    A time-dependent generalized non-linear Schrödinger equation (GNLSE) of motion was earlier derived in our laboratory by combining density functional theory and quantum fluid dynamics in threedimensional space. In continuation of the work reported previously, the GNLSE is applied to provide additional knowledge on ...

  11. Characterizing steady states of genome-scale metabolic networks in continuous cell cultures.

    Directory of Open Access Journals (Sweden)

    Jorge Fernandez-de-Cossio-Diaz

    2017-11-01

    Full Text Available In the continuous mode of cell culture, a constant flow carrying fresh media replaces culture fluid, cells, nutrients and secreted metabolites. Here we present a model for continuous cell culture coupling intra-cellular metabolism to extracellular variables describing the state of the bioreactor, taking into account the growth capacity of the cell and the impact of toxic byproduct accumulation. We provide a method to determine the steady states of this system that is tractable for metabolic networks of arbitrary complexity. We demonstrate our approach in a toy model first, and then in a genome-scale metabolic network of the Chinese hamster ovary cell line, obtaining results that are in qualitative agreement with experimental observations. We derive a number of consequences from the model that are independent of parameter values. The ratio between cell density and dilution rate is an ideal control parameter to fix a steady state with desired metabolic properties. This conclusion is robust even in the presence of multi-stability, which is explained in our model by a negative feedback loop due to toxic byproduct accumulation. A complex landscape of steady states emerges from our simulations, including multiple metabolic switches, which also explain why cell-line and media benchmarks carried out in batch culture cannot be extrapolated to perfusion. On the other hand, we predict invariance laws between continuous cell cultures with different parameters. A practical consequence is that the chemostat is an ideal experimental model for large-scale high-density perfusion cultures, where the complex landscape of metabolic transitions is faithfully reproduced.

  12. Density dependence governs when population responses to multiple stressors are magnified or mitigated.

    Science.gov (United States)

    Hodgson, Emma E; Essington, Timothy E; Halpern, Benjamin S

    2017-10-01

    Population endangerment typically arises from multiple, potentially interacting anthropogenic stressors. Extensive research has investigated the consequences of multiple stressors on organisms, frequently focusing on individual life stages. Less is known about population-level consequences of exposure to multiple stressors, especially when exposure varies through life. We provide the first theoretical basis for identifying species at risk of magnified effects from multiple stressors across life history. By applying a population modeling framework, we reveal conditions under which population responses from stressors applied to distinct life stages are either magnified (synergistic) or mitigated. We find that magnification or mitigation critically depends on the shape of density dependence, but not the life stage in which it occurs. Stressors are always magnified when density dependence is linear or concave, and magnified or mitigated when it is convex. Using Bayesian numerical methods, we estimated the shape of density dependence for eight species across diverse taxa, finding support for all three shapes. © 2017 by the Ecological Society of America.

  13. States of high energy density

    International Nuclear Information System (INIS)

    Murray, M.

    1988-02-01

    The transverse energy, E/sub tau/ spectra for O 16 and S 32 incident for various elements at 200 GeVnucleon are shown. The target and projectile dependencies of the data are discussed. The energy density achieved is estimated. For O 16 on Tungsten the multiplicity spectrum is also presented as well as the pseudorapidity spectra as a function of the transverse energy. The multiplicity cross section dσdN as measured in the backward hemisphere (0.9 < /eta/ < 2.9/ is found to be very similar in shape to the transverse energy distribution dσdE/tau/ reflecting the particular geometry of nucleus nucleus nucleus collisions. The dependence on the atomic mass of the target, A/sub tau/ and projectile A/sub p/ is not what one would expect from naive considerations

  14. Abnormal mitosis triggers p53-dependent cell cycle arrest in human tetraploid cells.

    Science.gov (United States)

    Kuffer, Christian; Kuznetsova, Anastasia Yurievna; Storchová, Zuzana

    2013-08-01

    Erroneously arising tetraploid mammalian cells are chromosomally instable and may facilitate cell transformation. An increasing body of evidence shows that the propagation of mammalian tetraploid cells is limited by a p53-dependent arrest. The trigger of this arrest has not been identified so far. Here we show by live cell imaging of tetraploid cells generated by an induced cytokinesis failure that most tetraploids arrest and die in a p53-dependent manner after the first tetraploid mitosis. Furthermore, we found that the main trigger is a mitotic defect, in particular, chromosome missegregation during bipolar mitosis or spindle multipolarity. Both a transient multipolar spindle followed by efficient clustering in anaphase as well as a multipolar spindle followed by multipolar mitosis inhibited subsequent proliferation to a similar degree. We found that the tetraploid cells did not accumulate double-strand breaks that could cause the cell cycle arrest after tetraploid mitosis. In contrast, tetraploid cells showed increased levels of oxidative DNA damage coinciding with the p53 activation. To further elucidate the pathways involved in the proliferation control of tetraploid cells, we knocked down specific kinases that had been previously linked to the cell cycle arrest and p53 phosphorylation. Our results suggest that the checkpoint kinase ATM phosphorylates p53 in tetraploid cells after abnormal mitosis and thus contributes to proliferation control of human aberrantly arising tetraploids.

  15. Large variability in synaptic N-methyl-D-aspartate receptor density on interneurons and a comparison with pyramidal-cell spines in the rat hippocampus.

    Science.gov (United States)

    Nyíri, G; Stephenson, F A; Freund, T F; Somogyi, P

    2003-01-01

    receptor density differs between pyramidal cells and interneurons. Some interneurons may have a high NMDA receptor content, whereas others, like some parvalbumin-expressing cells, a particularly low synaptic NMDA receptor content. Consequently, fast glutamatergic activation of interneurons is expected to show cell type-specific time course and state-dependent dynamics.

  16. Analytic solution of the BCS gap equation with a logarithmic singularity in the density of states

    International Nuclear Information System (INIS)

    Bhardwaj, A.; Muthu, S.K.

    1999-01-01

    The Bardeen-Cooper-Schrieffer (BCS) gap equation is solved analytically for a density of states function with a logarithmic singularity. It is an extension of our earlier work where we had assumed a constant density of states. We continue to work in the weak-coupling limit and consider both phononic and non-phononic pairings. Expressions are obtained for T c , Δ 0 (the gap at T=0), and the jump in the electronic specific heat at T=T c . We also calculate the isotope exponent and show that it is possible to reproduce the broad features of the experimental results in this framework. (orig.)

  17. Coherent states for certain time-dependent systems

    International Nuclear Information System (INIS)

    Pedrosa, I.A.

    1989-01-01

    Hartley and Ray have constructed and studied coherent states for the time-dependent oscillator. Here we show how to construct states for more general time-dependent systems. We also show that these states are equivalent to the well-known squeezed states. (author) [pt

  18. Contribution of herpesvirus specific CD8 T cells to anti-viral T cell response in humans.

    Directory of Open Access Journals (Sweden)

    Elena Sandalova

    Full Text Available Herpesviruses infect most humans. Their infections can be associated with pathological conditions and significant changes in T cell repertoire but evidences of symbiotic effects of herpesvirus latency have never been demonstrated. We tested the hypothesis that HCMV and EBV-specific CD8 T cells contribute to the heterologous anti-viral immune response. Volume of activated/proliferating virus-specific and total CD8 T cells was evaluated in 50 patients with acute viral infections: 20 with HBV, 12 with Dengue, 12 with Influenza, 3 with Adenovirus infection and 3 with fevers of unknown etiology. Virus-specific (EBV, HCMV, Influenza pentamer+ and total CD8 T cells were analyzed for activation (CD38/HLA-DR, proliferation (Ki-67/Bcl-2(low and cytokine production. We observed that all acute viral infections trigger an expansion of activated/proliferating CD8 T cells, which differs in size depending on the infection but is invariably inflated by CD8 T cells specific for persistent herpesviruses (HCMV/EBV. CD8 T cells specific for other non-related non persistent viral infection (i.e. Influenza were not activated. IL-15, which is produced during acute viral infections, is the likely contributing mechanism driving the selective activation of herpesvirus specific CD8 T cells. In addition we were able to show that herpesvirus specific CD8 T cells displayed an increased ability to produce the anti-viral cytokine interferon-gamma during the acute phase of heterologous viral infection. Taken together, these data demonstrated that activated herpesvirus specific CD8 T cells inflate the activated/proliferating CD8 T cells population present during acute viral infections in human and can contribute to the heterologous anti-viral T cell response.

  19. Band dependence of charge density wave in quasi-one-dimensional Ta2NiSe7 probed by orbital magnetoresistance

    Science.gov (United States)

    He, Jiaming; Zhang, Yiran; Wen, Libin; Yang, Yusen; Liu, Jinyu; Wu, Yueshen; Lian, Hailong; Xing, Hui; Wang, Shun; Mao, Zhiqiang; Liu, Ying

    2017-07-01

    Ta2NiSe7 is a quasi-one-dimensional (quasi-1D) transition-metal chalcogenide with Ta and Ni chain structures. An incommensurate charge-density wave (CDW) in this quasi-1D structure was well studied previously using tunnelling spectrum, X-ray, and electron diffraction, whereas its transport property and the relation to the underlying electronic states remain to be explored. Here, we report our results of the magnetoresistance (MR) on Ta2NiSe7. A breakdown of Kohler's rule is found upon entering the CDW state. Concomitantly, a clear change in curvature in the field dependence of MR is observed. We show that the curvature change is well described by the two-band orbital MR, with the hole density being strongly suppressed in the CDW state, indicating that the p orbitals from Se atoms dominate the change in transport through CDW transition.

  20. Effect of vibrational states on nuclear level density

    International Nuclear Information System (INIS)

    Plujko, V. A.; Gorbachenko, O. M.

    2007-01-01

    Simple methods to calculate a vibrational enhancement factor of a nuclear level density with allowance for damping of collective state are considered. The results of the phenomenological approach and the microscopic quasiparticle-phonon model are compared. The practical method of calculation of a vibrational enhancement factor and level density parameters is recommended

  1. Differential state-dependent modification of rat Na{sub v}1.6 sodium channels expressed in human embryonic kidney (HEK293) cells by the pyrethroid insecticides tefluthrin and deltamethrin

    Energy Technology Data Exchange (ETDEWEB)

    He, Bingjun [College of Life Sciences, Nankai University, Tianjin 300071 (China); Soderlund, David M., E-mail: dms6@cornell.edu [Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456 (United States)

    2011-12-15

    We expressed rat Na{sub v}1.6 sodium channels in combination with the rat {beta}1 and {beta}2 auxiliary subunits in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on expressed sodium currents using the whole-cell patch clamp technique. Both pyrethroids produced concentration-dependent, resting modification of Na{sub v}1.6 channels, prolonging the kinetics of channel inactivation and deactivation to produce persistent 'late' currents during depolarization and tail currents following repolarization. Both pyrethroids also produced concentration dependent hyperpolarizing shifts in the voltage dependence of channel activation and steady-state inactivation. Maximal shifts in activation, determined from the voltage dependence of the pyrethroid-induced late and tail currents, were {approx} 25 mV for tefluthrin and {approx} 20 mV for deltamethrin. The highest attainable concentrations of these compounds also caused shifts of {approx} 5-10 mV in the voltage dependence of steady-state inactivation. In addition to their effects on the voltage dependence of inactivation, both compounds caused concentration-dependent increases in the fraction of sodium current that was resistant to inactivation following strong depolarizing prepulses. We assessed the use-dependent effects of tefluthrin and deltamethrin on Na{sub v}1.6 channels by determining the effect of trains of 1 to 100 5-ms depolarizing prepulses at frequencies of 20 or 66.7 Hz on the extent of channel modification. Repetitive depolarization at either frequency increased modification by deltamethrin by {approx} 2.3-fold but had no effect on modification by tefluthrin. Tefluthrin and deltamethrin were equally potent as modifiers of Na{sub v}1.6 channels in HEK293 cells using the conditions producing maximal modification as the basis for comparison. These findings show that the actions of tefluthrin and deltamethrin of Na{sub v}1.6 channels

  2. A unified dislocation density-dependent physical-based constitutive model for cold metal forming

    Science.gov (United States)

    Schacht, K.; Motaman, A. H.; Prahl, U.; Bleck, W.

    2017-10-01

    Dislocation-density-dependent physical-based constitutive models of metal plasticity while are computationally efficient and history-dependent, can accurately account for varying process parameters such as strain, strain rate and temperature; different loading modes such as continuous deformation, creep and relaxation; microscopic metallurgical processes; and varying chemical composition within an alloy family. Since these models are founded on essential phenomena dominating the deformation, they have a larger range of usability and validity. Also, they are suitable for manufacturing chain simulations since they can efficiently compute the cumulative effect of the various manufacturing processes by following the material state through the entire manufacturing chain and also interpass periods and give a realistic prediction of the material behavior and final product properties. In the physical-based constitutive model of cold metal plasticity introduced in this study, physical processes influencing cold and warm plastic deformation in polycrystalline metals are described using physical/metallurgical internal variables such as dislocation density and effective grain size. The evolution of these internal variables are calculated using adequate equations that describe the physical processes dominating the material behavior during cold plastic deformation. For validation, the model is numerically implemented in general implicit isotropic elasto-viscoplasticity algorithm as a user-defined material subroutine (UMAT) in ABAQUS/Standard and used for finite element simulation of upsetting tests and a complete cold forging cycle of case hardenable MnCr steel family.

  3. Electrochemical evaluation of sulfur poisoning in a methane-fuelled solid oxide fuel cell: Effect of current density and sulfur concentration

    DEFF Research Database (Denmark)

    Hagen, Anke; Johnson, Gregory B.; Hjalmarsson, Per

    2014-01-01

    , the effect of sulfur was less pronounced on mass transfer/fuel reforming processes but quite significant on the charge transfer/TPB processes. Overall, sulfur related performance loss was more severe at the highest current density (1 A cm−2), due to the deactivation of catalytic fuel reforming reactions......A Ni/ScYSZ based SOFC was tested at 1, 0.5, 0.25, and 0 (OCV) A cm−2 in methane fuel containing 0–100 ppm H2S. Analysis of cell voltage loss during short-term H2S poisoning showed that SOFC performance loss was generally larger at higher current loads. Separating the effect of H2S on catalytic...... reforming and electrochemical activity by evaluating the relevant area specific resistances and charge transfer processes based on impedance spectroscopy revealed that the poisoning of electrochemical activity was not dependent on current density. Two major anode processes were significantly affected...

  4. X-ray absorption in insulators with non-Hermitian real-time time-dependent density functional theory.

    Science.gov (United States)

    Fernando, Ranelka G; Balhoff, Mary C; Lopata, Kenneth

    2015-02-10

    Non-Hermitian real-time time-dependent density functional theory was used to compute the Si L-edge X-ray absorption spectrum of α-quartz using an embedded finite cluster model and atom-centered basis sets. Using tuned range-separated functionals and molecular orbital-based imaginary absorbing potentials, the excited states spanning the pre-edge to ∼20 eV above the ionization edge were obtained in good agreement with experimental data. This approach is generalizable to TDDFT studies of core-level spectroscopy and dynamics in a wide range of materials.

  5. CORNEAL ENDOTHELIAL CELL DENSITY IN ACUTE ANGLE CLOSURE GLAUCOMA

    Directory of Open Access Journals (Sweden)

    Nishat Sultana K

    2016-09-01

    Full Text Available BACKGROUND Angle closure is characterised by apposition of the peripheral iris against the trabecular meshwork resulting in obstruction of aqueous outflow. Acute angle-closure glaucoma is characterised by pain, redness and blurred vision. The pain is typically a severe deep ache that follows the trigeminal distribution and maybe associated with nausea, vomiting, bradycardia and profuse sweating. The blurred vision, which is typically marked maybe caused by stretching of the corneal lamellae initially and later oedema of the cornea as well as a direct effect of the IOP on the optic nerve head. The modifications in corneal endothelial cell density after a crisis of angle-closure glaucoma is being evaluated. AIMS AND OBJECTIVES The objective of the study is to assess the corneal endothelial cell count (density by specular microscopy in patients presenting with acute angle-closure glaucoma. METHODS Corneal endothelial cell counts of 20 eyes of patients with PACG with an earlier documented symptomatic acute attack unilaterally were compared with 20 fellow eyes. Evaluation of patient included visual acuity, intraocular pressure, gonioscopy, disc findings and specular microscopy. RESULTS The mean endothelial cell density was 2104 cells/mm2 in the eye with acute attack and 2615 cells/mm2 in the fellow eye. The average endothelial cell count when the duration of attack lasted more than 72 hours was 1861 cells/mm2 . CONCLUSION Corneal endothelial cell density was found to be significantly reduced in eyes following an acute attack of primary angle closure glaucoma.

  6. Ghrelin plasma levels, gastric ghrelin cell density and bone mineral density in women with rheumatoid arthritis.

    Science.gov (United States)

    Maksud, F A N; Kakehasi, A M; Guimarães, M F B R; Machado, C J; Barbosa, A J A

    2017-05-18

    Generalized bone loss can be considered an extra-articular manifestation of rheumatoid arthritis (RA) that may lead to the occurrence of fractures, resulting in decreased quality of life and increased healthcare costs. The peptide ghrelin has demonstrated to positively affect osteoblasts in vitro and has anti-inflammatory actions, but the studies that correlate ghrelin plasma levels and RA have contradictory results. We aimed to evaluate the correlation between total ghrelin plasma levels, density of ghrelin-immunoreactive cells in the gastric mucosa, and bone mineral density (BMD) in twenty adult women with established RA with 6 months or more of symptoms (mean age of 52.70±11.40 years). Patients with RA presented higher ghrelin-immunoreactive cells density in gastric mucosa (P=0.008) compared with healthy females. There was a positive relationship between femoral neck BMD and gastric ghrelin cell density (P=0.007). However, these same patients presented a negative correlation between plasma ghrelin levels and total femoral BMD (P=0.03). The present results indicate that ghrelin may be involved in bone metabolism of patients with RA. However, the higher density of ghrelin-producing cells in the gastric mucosa of these patients does not seem to induce a corresponding elevation in the plasma levels of this peptide.

  7. Ghrelin plasma levels, gastric ghrelin cell density and bone mineral density in women with rheumatoid arthritis

    Directory of Open Access Journals (Sweden)

    F.A.N. Maksud

    Full Text Available Generalized bone loss can be considered an extra-articular manifestation of rheumatoid arthritis (RA that may lead to the occurrence of fractures, resulting in decreased quality of life and increased healthcare costs. The peptide ghrelin has demonstrated to positively affect osteoblasts in vitro and has anti-inflammatory actions, but the studies that correlate ghrelin plasma levels and RA have contradictory results. We aimed to evaluate the correlation between total ghrelin plasma levels, density of ghrelin-immunoreactive cells in the gastric mucosa, and bone mineral density (BMD in twenty adult women with established RA with 6 months or more of symptoms (mean age of 52.70±11.40 years. Patients with RA presented higher ghrelin-immunoreactive cells density in gastric mucosa (P=0.008 compared with healthy females. There was a positive relationship between femoral neck BMD and gastric ghrelin cell density (P=0.007. However, these same patients presented a negative correlation between plasma ghrelin levels and total femoral BMD (P=0.03. The present results indicate that ghrelin may be involved in bone metabolism of patients with RA. However, the higher density of ghrelin-producing cells in the gastric mucosa of these patients does not seem to induce a corresponding elevation in the plasma levels of this peptide.

  8. Low-temperature specific heat of the quasi-two-dimensional charge-density wave compound KMo6O17

    Science.gov (United States)

    Wang, Junfeng; Xiong, Rui; Yin, Di; Li, Changzhen; Tang, Zheng; Wang, Ququan; Shi, Jing; Wang, Yue; Wen, Haihu

    2006-05-01

    Low temperature specific heat (Cp) of quasi-two-dimensional charge-density wave (CDW) compound KMo6O17 has been studied by a relaxation method from 2to48K under zero and 12T magnetic fields. The results show that no specific heat anomaly is found at 16K under both zero and 12T magnetic fields, although an anomaly is clearly observed in the resistivity and magnetoresistance measurements. From the data between 2 and 4K , the density of states at Fermi level is estimated as 0.2eV-1permolecule and the Debye temperature is extracted to be 418K . A bump appearing in Cp/T3 is found between 4 and 48K centered around 12.5-15K , indicating that the phason excitations contribute to the total specific heat similarly as in quasi-one-dimensional CDW conductors. Using a modified Debye model, a pinning frequency of 0.73THz for KMo6O17 is estimated from the phason contribution.

  9. Computational neuroanatomy: mapping cell-type densities in the mouse brain, simulations from the Allen Brain Atlas

    Science.gov (United States)

    Grange, Pascal

    2015-09-01

    The Allen Brain Atlas of the adult mouse (ABA) consists of digitized expression profiles of thousands of genes in the mouse brain, co-registered to a common three-dimensional template (the Allen Reference Atlas).This brain-wide, genome-wide data set has triggered a renaissance in neuroanatomy. Its voxelized version (with cubic voxels of side 200 microns) is available for desktop computation in MATLAB. On the other hand, brain cells exhibit a great phenotypic diversity (in terms of size, shape and electrophysiological activity), which has inspired the names of some well-studied cell types, such as granule cells and medium spiny neurons. However, no exhaustive taxonomy of brain cell is available. A genetic classification of brain cells is being undertaken, and some cell types have been chraracterized by their transcriptome profiles. However, given a cell type characterized by its transcriptome, it is not clear where else in the brain similar cells can be found. The ABA can been used to solve this region-specificity problem in a data-driven way: rewriting the brain-wide expression profiles of all genes in the atlas as a sum of cell-type-specific transcriptome profiles is equivalent to solving a quadratic optimization problem at each voxel in the brain. However, the estimated brain-wide densities of 64 cell types published recently were based on one series of co-registered coronal in situ hybridization (ISH) images per gene, whereas the online ABA contains several image series per gene, including sagittal ones. In the presented work, we simulate the variability of cell-type densities in a Monte Carlo way by repeatedly drawing a random image series for each gene and solving the optimization problem. This yields error bars on the region-specificity of cell types.

  10. Continuity of integrated density of states – independent randomness

    Indian Academy of Sciences (India)

    Abstract. In this paper we discuss the continuity properties of the integrated density ... Density of states; Wegner estimate; Hölder continuous. 1. Introduction ..... and inverse spectral theory (Goa, 2000), Proc. Indian Acad. Sci. (Math. Sci.) 112(1).

  11. Triplet excited electronic state switching induced by hydrogen bonding: A transient absorption spectroscopy and time-dependent DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Ravi Kumar, Venkatraman; Ariese, Freek; Umapathy, Siva, E-mail: umapathy@ipc.iisc.ernet.in [Inorganic and Physical Chemistry Department, Indian Institute of Science, Bangalore 560012 (India)

    2016-03-21

    The solvent plays a decisive role in the photochemistry and photophysics of aromatic ketones. Xanthone (XT) is one such aromatic ketone and its triplet-triplet (T-T) absorption spectra show intriguing solvatochromic behavior. Also, the reactivity of XT towards H-atom abstraction shows an unprecedented decrease in protic solvents relative to aprotic solvents. Therefore, a comprehensive solvatochromic analysis of the triplet-triplet absorption spectra of XT was carried out in conjunction with time dependent density functional theory using the ad hoc explicit solvent model approach. A detailed solvatochromic analysis of the T-T absorption bands of XT suggests that the hydrogen bonding interactions are different in the corresponding triplet excited states. Furthermore, the contributions of non-specific and hydrogen bonding interactions towards differential solvation of the triplet states in protic solvents were found to be of equal magnitude. The frontier molecular orbital and electron density difference analysis of the T{sub 1} and T{sub 2} states of XT indicates that the charge redistribution in these states leads to intermolecular hydrogen bond strengthening and weakening, respectively, relative to the S{sub 0} state. This is further supported by the vertical excitation energy calculations of the XT-methanol supra-molecular complex. The intermolecular hydrogen bonding potential energy curves obtained for this complex in the S{sub 0}, T{sub 1}, and T{sub 2} states support the model. In summary, we propose that the different hydrogen bonding mechanisms exhibited by the two lowest triplet excited states of XT result in a decreasing role of the nπ{sup ∗} triplet state, and are thus responsible for its reduced reactivity towards H-atom abstraction in protic solvents.

  12. Nuclear ``pasta'' phase within density dependent hadronic models

    Science.gov (United States)

    Avancini, S. S.; Brito, L.; Marinelli, J. R.; Menezes, D. P.; de Moraes, M. M. W.; Providência, C.; Santos, A. M.

    2009-03-01

    In the present paper, we investigate the onset of the “pasta” phase with different parametrizations of the density dependent hadronic model and compare the results with one of the usual parametrizations of the nonlinear Walecka model. The influence of the scalar-isovector virtual δ meson is shown. At zero temperature, two different methods are used, one based on coexistent phases and the other on the Thomas-Fermi approximation. At finite temperature, only the coexistence phases method is used. npe matter with fixed proton fractions and in β equilibrium are studied. We compare our results with restrictions imposed on the values of the density and pressure at the inner edge of the crust, obtained from observations of the Vela pulsar and recent isospin diffusion data from heavy-ion reactions, and with predictions from spinodal calculations.

  13. Nuclear 'pasta' phase within density dependent hadronic models

    International Nuclear Information System (INIS)

    Avancini, S. S.; Marinelli, J. R.; Menezes, D. P.; Moraes, M. M. W. de; Brito, L.; Providencia, C.; Santos, A. M.

    2009-01-01

    In the present paper, we investigate the onset of the 'pasta' phase with different parametrizations of the density dependent hadronic model and compare the results with one of the usual parametrizations of the nonlinear Walecka model. The influence of the scalar-isovector virtual δ meson is shown. At zero temperature, two different methods are used, one based on coexistent phases and the other on the Thomas-Fermi approximation. At finite temperature, only the coexistence phases method is used. npe matter with fixed proton fractions and in β equilibrium are studied. We compare our results with restrictions imposed on the values of the density and pressure at the inner edge of the crust, obtained from observations of the Vela pulsar and recent isospin diffusion data from heavy-ion reactions, and with predictions from spinodal calculations

  14. Sex-Dependent Gene Expression in Human Pluripotent Stem Cells

    Directory of Open Access Journals (Sweden)

    Daniel Ronen

    2014-08-01

    Full Text Available Males and females have a variety of sexually dimorphic traits, most of which result from hormonal differences. However, differences between male and female embryos initiate very early in development, before hormonal influence begins, suggesting the presence of genetically driven sexual dimorphisms. By comparing the gene expression profiles of male and X-inactivated female human pluripotent stem cells, we detected Y-chromosome-driven effects. We discovered that the sex-determining gene SRY is expressed in human male pluripotent stem cells and is induced by reprogramming. In addition, we detected more than 200 differentially expressed autosomal genes in male and female embryonic stem cells. Some of these genes are involved in steroid metabolism pathways and lead to sex-dependent differentiation in response to the estrogen precursor estrone. Thus, we propose that the presence of the Y chromosome and specifically SRY may drive sex-specific differences in the growth and differentiation of pluripotent stem cells.

  15. Tissue-specific control of latent CMV reactivation by regulatory T cells.

    Directory of Open Access Journals (Sweden)

    Maha Almanan

    2017-08-01

    Full Text Available Cytomegalovirus (CMV causes a persistent, lifelong infection. CMV persists in a latent state and undergoes intermittent subclinical viral reactivation that is quelled by ongoing T cell responses. While T cells are critical to maintain control of infection, the immunological factors that promote CMV persistence remain unclear. Here, we investigated the role of regulatory T cells (Treg in a mouse model of latent CMV infection using Foxp3-diphtheria toxin receptor (Foxp3-DTR mice. Eight months after infection, MCMV had established latency in the spleen, salivary gland, lung, and pancreas, which was accompanied by an increased frequency of Treg. Administration of diphtheria toxin (DT after establishment of latency efficiently depleted Treg and drove a significant increase in the numbers of functional MCMV-specific CD4+ and CD8+ T cells. Strikingly, Treg depletion decreased the number of animals with reactivatable latent MCMV in the spleen. Unexpectedly, in the same animals, ablation of Treg drove a significant increase in viral reactivation in the salivary gland that was accompanied with augmented local IL-10 production by Foxp3-CD4+T cells. Further, neutralization of IL-10 after Treg depletion significantly decreased viral load in the salivary gland. Combined, these data show that Treg have divergent control of MCMV infection depending upon the tissue. In the spleen, Treg antagonize CD8+ effector function and promote viral persistence while in the salivary gland Treg prevent IL-10 production and limit viral reactivation and replication. These data provide new insights into the organ-specific roles of Treg in controlling the reactivation of latent MCMV infection.

  16. Cancer-associated fibroblasts regulate keratinocyte cell-cell adhesion via TGF-β-dependent pathways in genotype-specific oral cancer.

    Science.gov (United States)

    Cirillo, N; Hassona, Y; Celentano, A; Lim, K P; Manchella, S; Parkinson, E K; Prime, S S

    2017-01-01

    The interrelationship between malignant epithelium and the underlying stroma is of fundamental importance in tumour development and progression. In the present study, we used cancer-associated fibroblasts (CAFs) derived from genetically unstable oral squamous cell carcinomas (GU-OSCC), tumours that are characterized by the loss of genes such as TP53 and p16 INK4A and with extensive loss of heterozygosity, together with CAFs from their more genetically stable (GS) counterparts that have wild-type TP53 and p16 INK4A and minimal loss of heterozygosity (GS-OSCC). Using a systems biology approach to interpret the genome-wide transcriptional profile of the CAFs, we show that transforming growth factor-β (TGF-β) family members not only had biological relevance in silico but also distinguished GU-OSCC-derived CAFs from GS-OSCC CAFs and fibroblasts from normal oral mucosa. In view of the close association between TGF-β family members, we examined the expression of TGF-β1 and TGF-β2 in the different fibroblast subtypes and showed increased levels of active TGF-β1 and TGF-β2 in CAFs from GU-OSCC. CAFs from GU-OSCC, but not GS-OSCC or normal fibroblasts, induced epithelial-mesenchymal transition and down-regulated a broad spectrum of cell adhesion molecules resulting in epithelial dis-cohesion and invasion of target keratinocytes in vitro in a TGF-β-dependent manner. The results demonstrate that the TGF-β family of cytokines secreted by CAFs derived from genotype-specific oral cancer (GU-OSCC) promote, at least in part, the malignant phenotype by weakening intercellular epithelial adhesion. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  17. Density-dependent seedling mortality varies with light availability and species abundance in wet and dry Hawaiian forests

    Science.gov (United States)

    Faith Inman-Narahari; Rebecca Ostertag; Stephen P. Hubbell; Christian P. Giardina; Susan Cordell; Lawren Sack; Andrew MacDougall

    2016-01-01

    Conspecific density may contribute to patterns of species assembly through negative density dependence (NDD) as predicted by the Janzen-Connell hypothesis, or through facilitation (positive density dependence; PDD). Conspecific density effects are expected to be more negative in darker and wetter environments due to higher pathogen abundance and...

  18. Refitting density dependent relativistic model parameters including Center-of-Mass corrections

    International Nuclear Information System (INIS)

    Avancini, Sidney S.; Marinelli, Jose R.; Carlson, Brett Vern

    2011-01-01

    Full text: Relativistic mean field models have become a standard approach for precise nuclear structure calculations. After the seminal work of Serot and Walecka, which introduced a model Lagrangian density where the nucleons interact through the exchange of scalar and vector mesons, several models were obtained through its generalization, including other meson degrees of freedom, non-linear meson interactions, meson-meson interactions, etc. More recently density dependent coupling constants were incorporated into the Walecka-like models, which are then extensively used. In particular, for these models a connection with the density functional theory can be established. Due to the inherent difficulties presented by field theoretical models, only the mean field approximation is used for the solution of these models. In order to calculate finite nuclei properties in the mean field approximation, a reference set has to be fixed and therefore the translational symmetry is violated. It is well known that in such case spurious effects due to the center-of-mass (COM) motion are present, which are more pronounced for light nuclei. In a previous work we have proposed a technique based on the Pierls-Yoccoz projection operator applied to the mean-field relativistic solution, in order to project out spurious COM contributions. In this work we obtain a new fitting for the density dependent parameters of a density dependent hadronic model, taking into account the COM corrections. Our fitting is obtained taking into account the charge radii and binding energies for He 4 , O 16 , Ca 40 , Ca 48 , Ni 56 , Ni 68 , Sn 100 , Sn 132 and Pb 208 . We show that the nuclear observables calculated using our fit are of a quality comparable to others that can be found in the literature, with the advantage that now a translational invariant many-body wave function is at our disposal. (author)

  19. Current State of Technology of Fuel Cell Power Systems for Autonomous Underwater Vehicles

    Directory of Open Access Journals (Sweden)

    Alejandro Mendez

    2014-07-01

    Full Text Available Autonomous Underwater Vehicles (AUVs are vehicles that are primarily used to accomplish oceanographic research data collection and auxiliary offshore tasks. At the present time, they are usually powered by lithium-ion secondary batteries, which have insufficient specific energies. In order for this technology to achieve a mature state, increased endurance is required. Fuel cell power systems have been identified as an effective means to achieve this endurance but no implementation in a commercial device has yet been realized. This paper summarizes the current state of development of the technology in this field of research. First, the most adequate type of fuel cell for this application is discussed. The prototypes and design concepts of AUVs powered by fuel cells which have been developed in the last few years are described. Possible commercial and experimental fuel cell stack options are analyzed, examining solutions adopted in the analogous aerial vehicle applications, as well as the underwater ones, to see if integration in an AUV is feasible. Current solutions in oxygen and hydrogen storage systems are overviewed and energy density is objectively compared between battery power systems and fuel cell power systems for AUVs. A couple of system configuration solutions are described including the necessary lithium-ion battery hybrid system. Finally, some closing remarks on the future of this technology are given.

  20. Density of states and excitonic condensation in the double layer correlated systems

    Energy Technology Data Exchange (ETDEWEB)

    Apinyan, V., E-mail: v.apinyan@int.pan.wroc.pl; Kopeć, T.K.

    2016-01-15

    We consider the single-particle density of states (DOS) in the strongly correlated double layer (DL) system, without applied external fields. We demonstrate an unusual collapse effect in the spectrum of the normal single-particle spectral function at the particular high-symmetry point corresponding to the specific bunching-point solution of the chemical potential in the Frenkel channel. We show that at the low-temperature limit the anomalous spectral function obeys a concave like structure, which is directly related to the interlayer pair formation and condensation. We calculate the normal DOS functions, and we find their temperature dependence for different values of the interlayer Coulomb interaction parameter. We show that the normal electron and hole DOS functions demonstrate typical condensates double peak structures on the background of the excitonic pair formation quasiparticle spectra and we have found the evidence of the hybridization gap in the case of high-temperature limit, and small interlayer coupling parameter. Meanwhile, we show a possible crossover from the excitonic condensate regime into the band insulator state. The structure of the normal DOS spectra, in the Frenkel channel and for the strong interlayer coupling regime, is found gapless for all temperature limits, which clearly indicates the strong coherence effects in the DL structure, and the excitonic condensates therein. We have shown that the excitonic pair formation and pair condensation occur simultaneously in the DL system, in contrast with the purely three-dimensional (3D) or two-dimensional cases (2D), discussed previously.