WorldWideScience

Sample records for charge density-dependent strength

  1. The importance of spatial models for estimating the strength of density dependence

    DEFF Research Database (Denmark)

    Thorson, James T.; Skaug, Hans J.; Kristensen, Kasper;

    2014-01-01

    Identifying the existence and magnitude of density dependence is one of the oldest concerns in ecology. Ecologists have aimed to estimate density dependence in population and community data by fitting a simple autoregressive (Gompertz) model for density dependence to time series of abundance...... for an entire population. However, it is increasingly recognized that spatial heterogeneity in population densities has implications for population and community dynamics. We therefore adapt the Gompertz model to approximate local densities over continuous space instead of population-wide abundance......, and to allow productivity to vary spatially. Using simulated data generated from a spatial model, we show that the conventional (nonspatial) Gompertz model will result in biased estimates of density dependence, e.g., identifying oscillatory dynamics when not present. By contrast, the spatial Gompertz model...

  2. Constraining the density dependence of the symmetry energy using the multiplicity and average pT ratios of charged pions

    Science.gov (United States)

    Cozma, M. D.

    2017-01-01

    The charged pion multiplicity ratio in intermediate-energy heavy-ion collisions, a probe of the density dependence of symmetry energy above the saturation point, has been proven in a previous study to be extremely sensitive to the strength of the isovector Δ (1232 ) potential in nuclear matter. As there is no knowledge, either from theory or experiment, about the magnitude of this quantity, the extraction of constraints on the slope of the symmetry energy at saturation by using exclusively the mentioned observable is hindered at present. It is shown that, by including the ratio of average pT of charged pions / in the list of fitted observables, the noted problem can be circumvented. A realistic description of this observable requires accounting for the interaction of pions with the dense nuclear matter environment by the incorporation of the so-called S -wave and P -wave pion optical potentials. This is performed within the framework of a quantum molecular dynamics transport model that enforces the conservation of the total energy of the system. It is shown that constraints on the slope of the symmetry energy at saturation density and the strength of the Δ (1232) potential can be simultaneously extracted. A symmetry energy with a value of the slope parameter L >50 MeV is favored, at 1 σ confidence level, from a comparison with published FOPI experimental data. A precise constraint will require experimental data more accurate than presently available, particularly for the charged pion multiplicity ratio, and better knowledge of the density and momentum dependence of the pion potential for the whole range of these two variables probed in intermediate-energy heavy-ion collisions.

  3. Constraining the density dependence of the symmetry energy using the multiplicity and average $p_T$ ratios of charged pions

    CERN Document Server

    Cozma, M D

    2016-01-01

    The charged pion multiplicity ratio in intermediate energy heavy-ion collisions, a probe of the density dependence of symmetry energy above the saturation point, has been proven in a previous study to be extremely sensitive to the strength of the isovector $\\Delta$(1232) potential in nuclear matter. As there is no current knowledge, either from theory or experiment, about the magnitude of this quantity, the extraction of constraints for the slope of the symmetry energy at saturation by using exclusively the mentioned observable is hindered at present. It is shown that, by including the ratio of average $p_T$ of charged pions $\\langle p_T^{(\\pi^+)}\\rangle/\\langle p_T^{(\\pi^-)}\\rangle$ in the list of fitted observables, the noted problem can be circumvented. A realistic description of this observable requires the accounting for the interaction of pions with the dense nuclear matter environment by the incorporation of the so called S-wave and P-wave pion optical potentials. This is performed within the framework...

  4. Charge carrier density dependence of the hole mobility in poly(p-phenylene vinylene)

    OpenAIRE

    Tanase, C; Blom, PWM; De Leeuw, DM; de Meijer, EJ

    2004-01-01

    The hole transport in various poly(p-phenylene vinylene) (PPV) derivatives has been investigated in field-effect transistors (FETs) and light-emitting diodes (LEDs) as a function of temperature and applied bias. The discrepancy between the experimental hole mobilities extracted from FETs and LEDs based on a single disordered polymeric semiconductor originates from the strong dependence of the hole mobility on the charge carrier density. The microscopic charge transport parameters are directly...

  5. 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.)

  6. Density Dependence of Nuclear Symmetry Energy

    CERN Document Server

    Behera, B; Tripathy, S K

    2016-01-01

    High density behaviour of nuclear symmetry energy is studied on the basis of a stiffest density dependence of asymmetric contribution to energy per nucleon in charge neutral $n+p+e+\\mu$ matter under beta equilibrium. The density dependence of nuclear symmetry energy obtained in this way is neither very stiff nor soft at high densities and is found to be in conformity with recent observations of neutron stars

  7. Density dependence of nuclear symmetry energy

    Science.gov (United States)

    Behera, B.; Routray, T. R.; Tripathy, S. K.

    2016-10-01

    High density behavior of nuclear symmetry energy is studied on the basis of the stiffest density dependence of asymmetric contribution to energy per nucleon in charge neutral n + p + e + μ matter under beta equilibrium. The density dependence of nuclear symmetry energy obtained in this way is neither very stiff nor soft at high densities and is found to be in conformity with recent observations of neutron stars.

  8. 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.

  9. Ionic strength independence of charge distributions in solvation of biomolecules

    Energy Technology Data Exchange (ETDEWEB)

    Virtanen, J. J. [Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States); James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States); Sosnick, T. R. [Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637 (United States); Computation Institute, University of Chicago, Chicago, Illinois 60637 (United States); Freed, K. F. [Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States); James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States); Computation Institute, University of Chicago, Chicago, Illinois 60637 (United States)

    2014-12-14

    Electrostatic forces enormously impact the structure, interactions, and function of biomolecules. We perform all-atom molecular dynamics simulations for 5 proteins and 5 RNAs to determine the dependence on ionic strength of the ion and water charge distributions surrounding the biomolecules, as well as the contributions of ions to the electrostatic free energy of interaction between the biomolecule and the surrounding salt solution (for a total of 40 different biomolecule/solvent combinations). Although water provides the dominant contribution to the charge density distribution and to the electrostatic potential even in 1M NaCl solutions, the contributions of water molecules and of ions to the total electrostatic interaction free energy with the solvated biomolecule are comparable. The electrostatic biomolecule/solvent interaction energies and the total charge distribution exhibit a remarkable insensitivity to salt concentrations over a huge range of salt concentrations (20 mM to 1M NaCl). The electrostatic potentials near the biomolecule's surface obtained from the MD simulations differ markedly, as expected, from the potentials predicted by continuum dielectric models, even though the total electrostatic interaction free energies are within 11% of each other.

  10. Effects of density dependence in a temperate forest in northeastern China

    Science.gov (United States)

    Yao, Jie; Zhang, Xinna; Zhang, Chunyu; Zhao, Xiuhai; von Gadow, Klaus

    2016-09-01

    Negative density dependence may cause reduced clustering among individuals of the same species, and evidence is accumulating that conspecific density-dependent self-thinning is an important mechanism regulating the spatial structure of plant populations. This study evaluates that specific density dependence in three very large observational studies representing three successional stages in a temperate forest in northeastern China. The methods include standard spatial point pattern analysis and a heterogeneous Poisson process as the null model to eliminate the effects of habitat heterogeneity. The results show that most of the species exhibit conspecific density-dependent self-thinning. In the early successional stage 11 of the 16 species, in the intermediate successional stage 18 of the 21 species and in the old growth stage all 21 species exhibited density dependence after removing the effects of habitat heterogeneity. The prevalence of density dependence thus varies among the three successional stages and exhibits an increase with increasing successional stage. The proportion of species showing density dependence varied depending on whether habitat heterogeneity was removed or not. Furthermore, the strength of density dependence is closely related with species abundance. Abundant species with high conspecific aggregation tend to exhibit greater density dependence than rare species.

  11. Saturating interactions in /sup 4/He with density dependence

    Energy Technology Data Exchange (ETDEWEB)

    Bloom, S.D.; Resler, D.A.; Moszkowski, S.A.

    1989-05-03

    With the advent of larger and faster computers, as well as modern shell model codes, nuclear structure calculations for the light nuclei (A<16) which include full 2/bar h/..omega.. model spaces are quite feasible. However, there can be serious problems in the mixing of 2/bar h/..omega.. and higher excitations into the low-lying spectra if the effective interaction is non-saturating. Furthermore, effective interactions which are both saturating and density dependent have not generally been used in previous nuclear structure calculations. Therefore, we have undertaken studies of /sup 4/He using two-body potential interactions which incorporate both saturation and density-dependence. Encouraging initial results in remedying the mixing of 0 and 2/bar h/..omega.. excitations have been obtained. We have also considered the effects of our interaction on the /sup 4/He compressibility and the centroid of the breathing mode strength. First indications are that a saturating effective interaction, with a short-range density dependent part and a long-range density independent part, comes close to matching crude predictions for the compressibility of /sup 4/He. 11 refs., 6 tabs.

  12. Predation, habitat complexity, and variation in density-dependent mortality of temperate reef fishes.

    Science.gov (United States)

    Johnson, Darren W

    2006-05-01

    Density dependence in demographic rates can strongly affect the dynamics of populations. However, the mechanisms generating density dependence (e.g., predation) are also dynamic processes and may be influenced by local conditions. Understanding the manner in which local habitat features affect the occurrence and/or strength of density dependence will increase our understanding of population dynamics in heterogeneous environments. In this study I conducted two separate field experiments to investigate how local predator density and habitat complexity affect the occurrence and form of density-dependent mortality of juvenile rockfishes (Sebastes spp.). I also used yearly censuses of rockfish populations on nearshore reefs throughout central California to evaluate mortality of juvenile rockfish at large spatial scales. Manipulations of predators (juvenile bocaccio, S. paucispinus) and prey (kelp, gopher, and black-and-yellow [KGB] rockfish, Sebastes spp.) demonstrated that increasing the density of predators altered their functional response and thus altered patterns of density dependence in mortality of their prey. At low densities of predators, the number of prey consumed per predator was a decelerating function, and mortality of prey was inversely density dependent. However, at high densities of predators, the number of prey killed per predator became an accelerating response, and prey mortality was directly density dependent. Results of field experiments and large-scale surveys both indicated that the strength of density-dependent mortality may also be affected by the structural complexity of the habitat. In small-scale field experiments, increased habitat complexity increased the strength of density-dependent mortality. However, at large scales, increasing complexity resulted in a decrease in the strength of density dependence. I suggest that these differences resulted from scale-dependent changes in the predatory response that generated mortality. Whether

  13. Host range expansion is density dependent.

    Science.gov (United States)

    Castagneyrol, Bastien; Jactel, Hervé; Brockerhoff, Eckehard G; Perrette, Nicolas; Larter, Maximilien; Delzon, Sylvain; Piou, Dominique

    2016-11-01

    The realized host range of herbivores is expected to increase with herbivore population density. Theory also predicts that trait similarity and phylogenetic relatedness between native and exotic plants is expected to increase the susceptibility of introduced plants to feeding by native herbivores. Whether the ability of native herbivores to extend their host range to introduced species is density dependent is still unknown. We addressed this question by monitoring pine processionary moth (PPM, Thaumetopoea pityocampa) attacks during nine consecutive years on 41 pine species (8 native and 33 introduced) planted in an arboretum. The survey encompassed latent and outbreak periods. A total of 28 pine species were attacked by PPM. There was no difference in the probability of attack between native and introduced pine species. Host range increased and was more phylogenetically clustered during outbreak than latent periods. When population density increased, PPM expanded its diet breadth by attacking introduced pine species that were closely related to native hosts. This study demonstrates the density dependence of host range expansion in a common pine herbivore. Importantly, it supports the idea that the degree of phylogenetic proximity between host species can be a better predictor of attacks than the introduction status, which may help to predict the outcomes of new plant-herbivore interactions.

  14. 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.

  15. Wildlife disease elimination and density dependence

    KAUST Repository

    Potapov, A.

    2012-05-16

    Disease control by managers is a crucial response to emerging wildlife epidemics, yet the means of control may be limited by the method of disease transmission. In particular, it is widely held that population reduction, while effective for controlling diseases that are subject to density-dependent (DD) transmission, is ineffective for controlling diseases that are subject to frequency-dependent (FD) transmission. We investigate control for horizontally transmitted diseases with FD transmission where the control is via culling or harvest that is non-selective with respect to infection and the population can compensate through DD recruitment or survival. Using a mathematical model, we show that culling or harvesting can eradicate the disease, even when transmission dynamics are FD. Eradication can be achieved under FD transmission when DD birth or recruitment induces compensatory growth of new, healthy individuals, which has the net effect of reducing disease prevalence by dilution. We also show that if harvest is used simultaneously with vaccination, and there is high enough transmission coefficient, application of both controls may be less efficient than vaccination alone. We illustrate the effects of these control approaches on disease prevalence for chronic wasting disease in deer where the disease is transmitted directly among deer and through the environment.

  16. Stochasticity and Determinism: How Density-Independent and Density-Dependent Processes Affect Population Variability

    OpenAIRE

    Jan Ohlberger; Rogers, Lauren A.; Nils Chr. Stenseth

    2014-01-01

    A persistent debate in population ecology concerns the relative importance of environmental stochasticity and density dependence in determining variability in adult year-class strength, which contributes to future reproduction as well as potential yield in exploited populations. Apart from the strength of the processes, the timing of density regulation may affect how stochastic variation, for instance through climate, translates into changes in adult abundance. In this study, we develop a lif...

  17. Electric field strength of charged conducting balls and the breakdown of the air gap between them

    Energy Technology Data Exchange (ETDEWEB)

    Saranin, Vladimir A [Department of Physics, V.G. Korolenko Glazov State Pedagogical Institute, Glazov (Russian Federation)

    2002-12-31

    Field amplification factors at the surfaces of two charged conducting balls are calculated numerically. It is shown that as the balls are brought closer together, except when their potentials are equal, the amplification factors go to infinity, and in the case of like-charged balls the field at the surface of one of them changes sign. Breakdown field strengths for the air gap between balls of a different diameter are calculated using the experimental data of other authors as the base. The results suggest that the minimum breakdown field strength is 26 kV cm{sup -1} . The author's earlier results on the interaction force between the balls are revised. (methodological notes)

  18. Modulating the Arrangement of Charged Nanotubes by Ionic Strength in Salty Water.

    Science.gov (United States)

    Tao, Jiaojiao; Huang, Ningdong; Li, Junjun; Chen, Mingming; Wei, Chengsha; Li, Liangbin; Wu, Ziyu

    2014-04-03

    Despite the important role and potential application of charged cylindrical polyelectrolytes, biomacromolecules, and self-assembles, salt-modulated organization of those 1D charged nanostructures remains a topic relatively unexplored with an obscure underlying mechanism. In this Letter, the aggregation of oriented nanotubes self-assembled by ionic aromatic oligoamide in aqueous solution of NaCl over a wide concentration range is probed via small-angle X-ray scattering and a transmission electron microscope. The arrangement of nanotubes undergoes order-disorder transition sequences from an ordered rectangular phase to hexagonal packing and then to a lamellar gel. The observed transitions are understood by ionic effects on the electrostatic interaction between charged nanotubes and osmotic pressure due to ion partitioning. Above the physiological condition, electrostatic interactions are largely screened by the salts, while osmotic effects start to regulate the aggregation behavior and concomitantly deform the nanotubes. The study demonstrates rich phase behaviors of ordered, charged 1D nanostructures by tuning the ionic strength and underlying key physical principles.

  19. Disentangling density-dependent dynamics using full annual cycle models and Bayesian model weight updating

    Science.gov (United States)

    Robinson, Orin J.; McGowan, Conor; Devers, Patrick K.

    2017-01-01

    Density dependence regulates populations of many species across all taxonomic groups. Understanding density dependence is vital for predicting the effects of climate, habitat loss and/or management actions on wild populations. Migratory species likely experience seasonal changes in the relative influence of density dependence on population processes such as survival and recruitment throughout the annual cycle. These effects must be accounted for when characterizing migratory populations via population models.To evaluate effects of density on seasonal survival and recruitment of a migratory species, we used an existing full annual cycle model framework for American black ducks Anas rubripes, and tested different density effects (including no effects) on survival and recruitment. We then used a Bayesian model weight updating routine to determine which population model best fit observed breeding population survey data between 1990 and 2014.The models that best fit the survey data suggested that survival and recruitment were affected by density dependence and that density effects were stronger on adult survival during the breeding season than during the non-breeding season.Analysis also suggests that regulation of survival and recruitment by density varied over time. Our results showed that different characterizations of density regulations changed every 8–12 years (three times in the 25-year period) for our population.Synthesis and applications. Using a full annual cycle, modelling framework and model weighting routine will be helpful in evaluating density dependence for migratory species in both the short and long term. We used this method to disentangle the seasonal effects of density on the continental American black duck population which will allow managers to better evaluate the effects of habitat loss and potential habitat management actions throughout the annual cycle. The method here may allow researchers to hone in on the proper form and/or strength of

  20. Determination of Surface Charge of Titanium Dioxide (Anatase) at High Ionic Strength

    Science.gov (United States)

    Schoonen, M. A.; Strongin, D. R.

    2014-12-01

    Charge development on mineral surfaces is an important control on the fate of minor and trace elements in a wide range of environments, including in possible radioactive waste repositories. Formation waters have often a high ionic strength. In this study, we determined the zeta potential (ζ) of anatase in potassium chloride solutions with concentrations up to 3M (25°C). The zeta potential is the potential at the hydrodynamic shear plane. In this study, we made use of the electro-acoustic effect. This effect is based on the development of a measureable potential/current when the electrical double layer outside the shearplane is separated from a charged particle through rapid oscillation induced by a sound wave. The advantage of this type of measurement is that the particles are not subjected to a high electric field (common to typical zeta potential measurements), which leads to electrode reactions and a shift of solution pH. Measurements were collected by subtracting the ion vibration current (IVI) due to the presence of potassium and chloride ions from the CVI. The correction is necessary for measurements in solutions with I > 0.25 M. This subtraction was done at each of the measurement conditions by centrifuging the slurrly, measuring the IVI of the supernatant, reconstituting the slurry, and then measuring CVI of the slurry. Subtraction of IVI at each condition is critical because IVI changes with pH and accounts for most of raw signal. The results show that the anatase isoelectric point shifts from a pH ~6.5 to a value of ~4.5 at 1M KCl. At ionic strength in excess of 1 M KCl, the surface appears to be slightly negatively charged accross the pH range accessible by this technique (pH 2.5-10). The loss of an isoelectric point suggests that KCl is no longer an indifferent electrolyte at 1 M KCl and higher. The results are in disagreement with earlier measurements in which anatase was shown to have a positive charge at high ionic strength across the pH scale. The

  1. 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.

  2. Characterization of Final State Interaction Strength in Plastic Scintillator by Muon-Neutrino Charged Current Charged Pion Production

    Energy Technology Data Exchange (ETDEWEB)

    Eberly, Brandon M. [Univ. of Pittsburgh, PA (United States)

    2014-01-01

    Precise knowledge of neutrino-nucleus interactions is increasingly important as neutrino oscillation measurements transition into the systematics-limited era. In addition to modifying the initial interaction, the nuclear medium can scatter and absorb the interaction by-products through final state interactions, changing the types and kinematic distributions of particles seen by the detector. Recent neutrino pion production data from MiniBooNE is inconsistent with the final state interaction strength predicted by models and theoretical calculations, and some models fit best to the MiniBooNE data only after removing final state interactions entirely. This thesis presents a measurement of dσ/dTπ and dσ/dθπ for muon-neutrino charged current charged pion production in the MINER A scintillator tracker. MINER A is a neutrino-nucleus scattering experiment installed in the few-GeV NuMI beam line at Fermilab. The analysis is limited to neutrino energies between 1.5-10 GeV. Dependence on invariant hadronic mass W is studied through two versions of the analysis that impose the limits W < 1.4 GeV and W < 1.8 GeV. The lower limit on W increases compatibility with the MiniBooNE pion data. The shapes of the differential cross sections, which depend strongly on the nature of final state interactions, are compared to Monte Carlo and theoretical predictions. It is shown that the measurements presented in this thesis favor models that contain final state interactions. Additionally, a variety of neutrino-nucleus interaction models are shown to successfully reproduce the thesis measurements, while simultaneously failing to describe the shape of the MiniBooNE data.

  3. Stochasticity and determinism: how density-independent and density-dependent processes affect population variability.

    Science.gov (United States)

    Ohlberger, Jan; Rogers, Lauren A; Stenseth, Nils Chr

    2014-01-01

    A persistent debate in population ecology concerns the relative importance of environmental stochasticity and density dependence in determining variability in adult year-class strength, which contributes to future reproduction as well as potential yield in exploited populations. Apart from the strength of the processes, the timing of density regulation may affect how stochastic variation, for instance through climate, translates into changes in adult abundance. In this study, we develop a life-cycle model for the population dynamics of a large marine fish population, Northeast Arctic cod, to disentangle the effects of density-independent and density-dependent processes on early life-stages, and to quantify the strength of compensatory density dependence in the population. The model incorporates information from scientific surveys and commercial harvest, and dynamically links multiple effects of intrinsic and extrinsic factors on all life-stages, from eggs to spawners. Using a state-space approach we account for observation error and stochasticity in the population dynamics. Our findings highlight the importance of density-dependent survival in juveniles, indicating that this period of the life cycle largely determines the compensatory capacity of the population. Density regulation at the juvenile life-stage dampens the impact of stochastic processes operating earlier in life such as environmental impacts on the production of eggs and climate-dependent survival of larvae. The timing of stochastic versus regulatory processes thus plays a crucial role in determining variability in adult abundance. Quantifying the contribution of environmental stochasticity and compensatory mechanisms in determining population abundance is essential for assessing population responses to climate change and exploitation by humans.

  4. 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.

  5. Half lives of spherical proton emitters using density dependent M3Y interaction

    CERN Document Server

    Chowdhury, P R; Basu, D N

    2005-01-01

    The proton radioactivity lifetimes of spherical proton emitters from the ground and the isomeric states are calculated using the microscopic nucleon-nucleus interaction potentials. The daughter nuclei density distributions are folded with a realistic density dependent M3Y effective interaction supplemented by a zero-range pseudo-potential. The density dependence parameters of the interaction are extracted from the nuclear matter calculations. The saturation energy per nucleon used for nuclear matter calculations is determined from the co-efficient of the volume term of Bethe-Weizsacker mass formula which is evaluated by fitting the recent experimental and estimated atomic mass excesses from Audi-Wapstra-Thibault atomic mass table by minimizing the mean square deviation. The quantum mechanical tunneling probability is calculated within the WKB approximation. Spherical charge distributions are used for calculating the Coulomb interaction potentials. These calculations provide good estimates for the observed pro...

  6. 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

  7. 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 sup

  8. Effect of ionic strength on adsorption of As(Ⅲ) and As(Ⅴ) on variable charge soils

    Institute of Scientific and Technical Information of China (English)

    XU Renkou; WANG Yong; TIWARI Diwakar; WANG Houyan

    2009-01-01

    The study was to investigate the adsorption behavior of arsenite (As(Ⅲ)) and arsenate (As(Ⅴ)) on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with batch methods. Results indicated that the amount of As(Ⅲ) adsorbed by these two soils increased with increasing solution pH, whereas it decreased with increasing ionic strength under the acidic condition. This suggested that As(Ⅲ) was mainly adsorbed on soil positive charge sites through electrostatic attraction under the acidic condition. Moreover, intersects of As(Ⅴ) adsorption-pH curves at different ionic strengths (a characteristic pH) are obtained for both soils. It was noted that above this pH, the adsorption of As(Ⅴ) was increased with increasing ionic strength, whereas below it the reverse trend was true. Precisely the intersect pH was 3.6 for Haplic Acrisol and 4.5 for Rhodic Ferralsol, which was near the values of PZSE (soil point of zero salt effect) of these soils. The effects of ionic strength and pH on arsenate adsorption by these soils were interpreted by the adsorption model. The results of zeta potential suggested that the potential in adsorption plane becomes less negative with increasing ionic strength above soil PZSE and decreases with increasing ionic strength below soil PZSE. These results further supported the hypothesis of the adsorption model that the potential in the adsorption plane changes with ionic strength with an opposite trend to surface charge of the soils. Therefore, the change of the potential in the adsorption plane was mainly responsible for the change of arsenate adsorption induced by ionic strength on variable charge soils.

  9. Negative density dependence is stronger in resource-rich environments and diversifies communities when stronger for common but not rare species.

    Science.gov (United States)

    LaManna, Joseph A; Walton, Maranda L; Turner, Benjamin L; Myers, Jonathan A

    2016-06-01

    Conspecific negative density dependence is thought to maintain diversity by limiting abundances of common species. Yet the extent to which this mechanism can explain patterns of species diversity across environmental gradients is largely unknown. We examined density-dependent recruitment of seedlings and saplings and changes in local species diversity across a soil-resource gradient for 38 woody-plant species in a temperate forest. At both life stages, the strength of negative density dependence increased with resource availability, becoming relatively stronger for rare species during seedling recruitment, but stronger for common species during sapling recruitment. Moreover, negative density dependence appeared to reduce diversity when stronger for rare than common species, but increase diversity when stronger for common species. Our results suggest that negative density dependence is stronger in resource-rich environments and can either decrease or maintain diversity depending on its relative strength among common and rare species.

  10. 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.

  11. Limit Theorems for Competitive Density Dependent Population Processes

    CERN Document Server

    Parsons, Todd L

    2010-01-01

    Near the beginning of the century, Wright and Fisher devised an elegant, mathematically tractable model of gene reproduction and replacement that laid the foundation for contemporary population genetics. The Wright-Fisher model and its extensions have given biologists powerful tools of statistical inference that enabled the quantification of genetic drift and selection. Given the utility of these tools, we often forget that their model - for mathematical, and not biological reasons - makes assumptions that are violated in most real-world populations. In this paper, I consider an alternative framework that merges P. A. P. Moran's continuous-time Markov chain model of allele frequency with the density dependent models of ecological competition proposed by Gause, Lotka and Volterra, that, unlike Moran's model allow for a stochastically varying -- but bounded -- population size. I require that allele numbers vary according to a density-dependent population process, for which the limiting law of large numbers is a...

  12. Viscosity and density dependence during maximal flow in man.

    Science.gov (United States)

    Staats, B A; Wilson, T A; Lai-Fook, S J; Rodarte, J R; Hyatt, R E

    1980-02-01

    Maximal expiratory flow curves were obtained from ten healthy subjects white breathing air and three other gas mixtures with different densities and viscosities. From these data, the magnitudes of the dependence of maximal flow on gas density and viscosity were obtained. The scaling laws of fluid mechanics, together with a model for the flow-limiting mechanism, were used to obtain a prediction of the relationship between the density dependence and the viscosity dependence of maximal flow. Although the data for individual subjects were too variable to allow a precise comparison with this prediction, the relationship between the mean density dependence and the mean viscosity dependence of all usbjects agreed with the theoretic prediction. This agreement supports the assumption, which is frequently made, that flow resistance rather than tissue visoelasticity is the dominant contributor to peripheral resistance. Information on the relationships between the pressure drop to the flow-limiting segment and flow, gas density and viscosity, and lung volume were also obtained.

  13. Approximate particle number projection for finite range density dependent forces

    CERN Document Server

    Valor, A; Robledo, L M

    1996-01-01

    The Lipkin-Nogami method is generalized to deal with finite range density dependent forces. New expressions are derived and realistic calculations with the Gogny force are performed for the nuclei ^{164}Er and ^{168}Er. The sharp phase transition predicted by the mean field approximation is washed out by the Lipkin-Nogami approach; a much better agreement with the experimental data is reached with the new approach than with the Hartree-Fock_Bogoliubov one, specially at high spins.

  14. Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

    Energy Technology Data Exchange (ETDEWEB)

    Bajaj, Sanyam, E-mail: bajaj.10@osu.edu; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Reza, Shahed; Chumbes, Eduardo M. [Raytheon Integrated Defense Systems, Andover, Massachusetts 01810 (United States); Khurgin, Jacob [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Material Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-10-12

    We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10{sup 7 }cm/s at a low sheet charge density of 7.8 × 10{sup 11 }cm{sup −2}. An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

  15. Characterization and Modeling of Received Signal Strength and Charging Time for Wireless Energy Transfer

    Directory of Open Access Journals (Sweden)

    Uthman Baroudi

    2015-01-01

    Full Text Available Wireless sensor networks can provide effective means for monitoring and controlling a wide range of applications. Recently, tremendous effort was directed towards devising sensors powered from ambient sources such as heat, wind, and vibration. Wireless energy transfer is another source that has attractive features that make it a promising candidate for supplying power to wireless sensor nodes. This paper is concerned with characterizing and modeling the charging time and received signal strength indicator for wireless energy transfer system. These parameters play a vital role in deciding the geometry of sensor network and the routing protocols to be deployed. The development of communication protocols for wireless-powered wireless sensor networks is also improved with the knowledge of such models. These two quantities were computed from data acquired at various coordinates of the harvester relative to a fixed position of RF energy source. Data was acquired for indoor and outdoor scenarios using the commercially available PowerCast energy harvester and evaluation board. Mathematical models for both indoor and outdoor environments were developed and analyzed. A few guidelines on how to use these models were suggested. Finally, the possibility of harvesting the energy from the ambient RF power to energize wireless sensor nodes was also investigated.

  16. Evaluation of the strength of electron-proton scattering data for determining the proton charge radius

    CERN Document Server

    Horbatsch, M

    2015-01-01

    Precisely measured electron-proton elastic scattering cross sections [Phys. Rev. Lett. {\\bf 105}, 242002 (2010)] are reanalyzed to evaluate their strength for determining the rms charge radius ($R_{\\rm E}$) of the proton. More than half of the cross sections at lowest $Q^2$ are fit using two single-parameter form-factor models, with the first based on a dipole parametrization, and the second on a linear fit to a conformal-mapping variable. These low-$Q^2$ fits extrapolate the slope of the form factor to $Q^2$=0 and determine $R_{\\rm E}$ values of approximately 0.84 and 0.89~fm, respectively. Fits spanning all $Q^2$, in which the single constants are replaced with cubic splines at larger $Q^2$, lead to similar results for $R_{\\rm E}$. We conclude that the scattering data is consistent with $R_{\\rm E}$ ranging from at least 0.84 to 0.89~fm, and therefore cannot resolve the discrepancy between determinations of $R_{\\rm E}$ made using muonic and electronic hydrogen-atom spectroscopy.

  17. Influence of ionic strength and beta2-glycoprotein I concentration on agglutination of like-charged phospholipid membranes.

    Science.gov (United States)

    Perutková, Šárka; Frank-Bertoncelj, Mojca; Rozman, Blaž; Kralj-Iglič, Veronika; Iglič, Aleš

    2013-11-01

    The effect of ionic strength on adhesion between negatively charged giant unilamellar vesicles induced by beta2-glycoprotein I (β2-GPI) was studied experimentally and theoretically. Measuring the effective angle of contact between adhering vesicles indicated that the strength of adhesion between vesicles decreases with increasing ionic strength, and increases with concentration of β2-GPI. In the theoretical part we focused on the study of the average orientation of β2-GPI near the charged membrane and its role in mediating the attractive interactions between the vesicles. β2-GPI proteins were modelled as rods with internal distribution of electric charge. The predictions of Monte Carlo simulations show orthogonal orientation of some of the membrane attached β2-GPI in narrow gap between two vesicles. On the contrary, at larger distances between vesicles the proteins are parallelly attached to the membrane surface. A local minimum of the free energy corresponding to β2-GPI-mediated adhesion of two neighbouring vesicles was predicted. The strength of adhesion was confirmed to decrease at high ionic strength.

  18. Density-dependent acoustic properties of PBX 9502

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Geoffrey W [Los Alamos National Laboratory; Thompson, Darla G [Los Alamos National Laboratory; Deluca, Racci [Los Alamos National Laboratory; Hartline, Ernest L [Los Alamos National Laboratory; Hagelberg, Stephanie I [Los Alamos National Laboratory

    2009-07-31

    We have measured the longitudinal and shear acoustic velocities of PBX 9502 as a function of density for die-pressed samples over the range 1.795 g/cc to 1.888 g/cc. The density dependence of the velocities is linear. Thermal cycling of PBX 9502 is known to induce irreversible volume growth. We have measured this volume growth dependence on density for a subset of the pressed parts and find that the most growth occurs for the samples with lowest initial density. The acoustic velocity changes due to the volume growth are significant and reflect damage in the samples.

  19. Effect of the density dependent symmetry energy on fragmentation

    CERN Document Server

    Vinayak, Karan Singh

    2011-01-01

    The effect of the density dependence of symmetry energy on fragmentation is studied using isospin-dependent quantum molecular dynamics model(IQMD) Model. We have used the reduced isospin-dependent cross-section with soft equation of state to explain the experimental findings for the system 79_Au^197 + 79_Au^197 for the full colliding geometry. In addition to that we have tried to study the collective response of the momentum dependent interactions(MDI) and symmetry energy towards the multifragmentation

  20. The population dynamical consequences of density-dependent prophylaxis.

    Science.gov (United States)

    Reynolds, Jennifer J H; White, Andrew; Sherratt, Jonathan A; Boots, Mike

    2011-11-07

    When infectious disease transmission is density-dependent, the risk of infection will tend to increase with host population density. Since host defence mechanisms can be costly, individual hosts may benefit from increasing their investment in immunity in response to increasing population density. Such "density-dependent prophylaxis" (DDP) has now indeed been demonstrated experimentally in several species. However, it remains unclear how DDP will affect the population dynamics of the host-pathogen interaction, with previous theoretical work making conflicting predictions. We develop a general host-pathogen model and assess the role of DDP on the population dynamics. The ability of DDP to drive population cycles is critically dependent on the time delay between the change in density and the subsequent phenotypic change in the level of resistance. When the delay is absent or short, DDP destabilises the system. As the delay increases, its destabilising effect first diminishes and then DDP becomes increasingly stabilising. Our work highlights the significance of the time delay and suggests that it must be estimated experimentally or varied in theoretical investigations in order to understand the implications of DDP for the population dynamics of particular systems.

  1. Density-dependent potential for multi-neutron halo nuclei

    Institute of Scientific and Technical Information of China (English)

    CHEN Shuang; CHU Yan-Yun; REN Zhong-Zhou

    2009-01-01

    We apply a simple density-dependent potential model to the three-body calculation of the ground-state structure of drip-line nuclei with a weakly bound core. The hyperspherical harmonics method is used to solve the Faddeev equations. There are no undetermined potential parameters in this calculation. We find that for the halo nuclei with a weakly-bound core, the calculated properties of the ground-state structure are in better agreement with experimental data than the results calculated from the standard Woods-Saxon and Gauss type potentials. We also successfully reproduce the experimental cross sections by using the density calculated from this method. This may be explained by the fact that the simple Fermi or Gaussian function can not exactly describe the density distribution of the drip-line nuclei.

  2. The pasta phase within density dependent hadronic models

    CERN Document Server

    Avancini, S S; Marinelli, J R; Peres-Menezes, D; Watanabe de Moraes, M M; Providência, C; Santos, A M

    2008-01-01

    In the present paper we investigate the onset of the pasta phase with different parametrisations of the density dependent hadronic model and compare the results with one of the usual parametrisation of the non-linear Walecka model. The influence of the scalar-isovector virtual delta 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 beta-equilibrium are studied. We compare our results with restrictions imposed on the 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.

  3. Exploration of a modified density dependence in the Skyrme functional

    CERN Document Server

    Erler, J; Reinhard, P -G

    2010-01-01

    A variant of the basic Skyrme-Hartree-Fock (SHF) functional is considered dealing with a new form of density dependence. It employs only integer powers and thus will allow a more sound basis for projection schemes (particle number, angular momentum). We optimize the new functional with exactly the same adjustment strategy as used in an earlier study with a standard Skyrme functional. This allows direct comparisons of the performance of the new functional relative to the standard one. We discuss various observables: bulk properties of finite nuclei, nuclear matter, giant resonances, super-heavy elements, and energy systematics. The new functional performs at least as well as the standard one, but offers a wider range of applicability (e.g. for projection) and more flexibility in the regime of high densities.

  4. Effect of hydrogen charging on the mechanical properties of medium strength aluminium alloys 2091 and 2014

    DEFF Research Database (Denmark)

    Bandopadhyay, A.; Ambat, Rajan; Dwarakadasa, E.S.

    1992-01-01

    Cathodic hydrogen charging in 3.5% NaCl solution altered the mechanical properties of 2091-T351 (Al-Cu-Li-Mg-Zr) determined by a slow (10(-3)/s) strain rate tensile testing technique. UTS and YS decreased in the caw of 2091-T351 and 2014-T6(Al-Cu-Mn-Si-Mg) with increase in charging current density...

  5. Charge Transfer and Bonding Strength in Lithium-intercalated Polyaromatic Hydrocarbons Studied by Photoelectron Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    R.Friedlein

    2007-01-01

    1 Results The potential applications of small-, medium-and large-size polyaromatic hydrocarbons for charge and energy storage in lithium metal and lithium ion batteries are discussed. In order to find the best carbon-based electrode materials, the specific roles of the molecular and solid-state contributions have to be understood. For the molecular contributions, a semi-quantitative method is proposed to compare the charge storage capability of polyaromatic hydrocarbon molecules. A compilation of result...

  6. Incorporating density dependence into the directed-dispersal hypothesis.

    Science.gov (United States)

    Spiegel, Orr; Nathan, Ran

    2010-05-01

    The directed-dispersal (DrD) hypothesis, one of the main explanations for the adaptive value of seed dispersal, asserts that enhanced (nonrandom) arrival to favorable establishment sites is advantageous for plant fitness. However, as anticipated by the ideal free distribution theory, enhanced seed deposition may impair site suitability by increasing density-dependent mortality, thus negating the advantage postulated by the DrD hypothesis. Although the role of density effects is thoroughly discussed in the seed-dispersal literature, this DrD paradox remains largely overlooked. The paradox, however, may be particularly pronounced in animal-mediated dispersal systems, in which DrD is relatively common, because animals tend to generate local seed aggregations due to their nonrandom movements. To investigate possible solutions to the DrD paradox, we first introduce a simple analytical model that calculates the optimal DrD level at which seed arrival to favorable establishment sites yields maximal fitness gain in comparison to a null model of random arrival. This model predicts intermediate optimal DrD levels that correspond to various attributes of the plants, the dispersers, and the habitat. We then use a simulation model to explore the temporal dynamics of the invasion process of the DrD strategy in a randomly dispersed population, and the resistance of a DrD population against invasion of other dispersal strategies. This model demonstrates that some properties of the invasion process (e.g., mutant persistence ratio in the population and generations until initial establishment) are facilitated by high DrD levels, and not by intermediate levels as expected from the analytical model. These results highlight the need to revise the DrD hypothesis to include the countering effects of density-dependent mortality inherently imposed by enhanced arrival of seeds to specific sites. We illustrate how the revised hypothesis can elucidate previous results from empirical studies

  7. A density-dependent endochronic plasticity for powder compaction processes

    Science.gov (United States)

    Bakhshiani, A.; Khoei, A. R.; Mofid, M.

    This paper is concerned with the numerical modeling of powder cold compaction process using a density-dependent endochronic plasticity model. Endochronic plasticity theory is developed based on a large strain plasticity to describe the nonlinear behavior of powder material. The elastic response is stated in terms of hypoelastic model and endochronic plasticity constitutive equations are stated in unrotated frame of reference. A trivially incrementally objective integration scheme for rate constitutive equations is established. Algorithmic modulus consistent with numerical integration algorithm of constitutive equations is extracted. It is shown how the endochronic plasticity describes the behavior of powder material from the initial stage of compaction to final stage, in which material behaves as solid metals. It is also shown that some commonly used plasticity models for powder material can be derived as special cases of the proposed endochronic theory. Finally, the numerical schemes are examined for efficiency in the modeling of a plain bush, a rotational-flanged and a shaped tablet powder compaction component.

  8. Balancing selection shapes density-dependent foraging behaviour.

    Science.gov (United States)

    Greene, Joshua S; Brown, Maximillian; Dobosiewicz, May; Ishida, Itzel G; Macosko, Evan Z; Zhang, Xinxing; Butcher, Rebecca A; Cline, Devin J; McGrath, Patrick T; Bargmann, Cornelia I

    2016-11-10

    The optimal foraging strategy in a given environment depends on the number of competing individuals and their behavioural strategies. Little is known about the genes and neural circuits that integrate social information into foraging decisions. Here we show that ascaroside pheromones, small glycolipids that signal population density, suppress exploratory foraging in Caenorhabditis elegans, and that heritable variation in this behaviour generates alternative foraging strategies. We find that natural C. elegans isolates differ in their sensitivity to the potent ascaroside icas#9 (IC-asc-C5). A quantitative trait locus (QTL) regulating icas#9 sensitivity includes srx-43, a G-protein-coupled icas#9 receptor that acts in the ASI class of sensory neurons to suppress exploration. Two ancient haplotypes associated with this QTL confer competitive growth advantages that depend on ascaroside secretion, its detection by srx-43 and the distribution of food. These results suggest that balancing selection at the srx-43 locus generates alternative density-dependent behaviours, fulfilling a prediction of foraging game theory.

  9. Lower within-community variance of negative density dependence increases forest diversity.

    Directory of Open Access Journals (Sweden)

    António Miranda

    Full Text Available Local abundance of adult trees impedes growth of conspecific seedlings through host-specific enemies, a mechanism first proposed by Janzen and Connell to explain plant diversity in forests. While several studies suggest the importance of this mechanism, there is still little information of how the variance of negative density dependence (NDD affects diversity of forest communities. With computer simulations, we analyzed the impact of strength and variance of NDD within tree communities on species diversity. We show that stronger NDD leads to higher species diversity. Furthermore, lower range of strengths of NDD within a community increases species richness and decreases variance of species abundances. Our results show that, beyond the average strength of NDD, the variance of NDD is also crucially important to explain species diversity. This can explain the dissimilarity of biodiversity between tropical and temperate forest: highly diverse forests could have lower NDD variance. This report suggests that natural enemies and the variety of the magnitude of their effects can contribute to the maintenance of biodiversity.

  10. Charged-particle spectroscopy for diagnosing shock ρR and strength in NIF implosions.

    Science.gov (United States)

    Zylstra, A B; Frenje, J A; Séguin, F H; Rosenberg, M J; Rinderknecht, H G; Johnson, M Gatu; Casey, D T; Sinenian, N; Manuel, M J-E; Waugh, C J; Sio, H W; Li, C K; Petrasso, R D; Friedrich, S; Knittel, K; Bionta, R; McKernan, M; Callahan, D; Collins, G W; Dewald, E; Döppner, T; Edwards, M J; Glenzer, S; Hicks, D G; Landen, O L; London, R; Mackinnon, A; Meezan, N; Prasad, R R; Ralph, J; Richardson, M; Rygg, J R; Sepke, S; Weber, S; Zacharias, R; Moses, E; Kilkenny, J; Nikroo, A; Sangster, T C; Glebov, V; Stoeckl, C; Olson, R; Leeper, R J; Kline, J; Kyrala, G; Wilson, D

    2012-10-01

    The compact Wedge Range Filter (WRF) proton spectrometer was developed for OMEGA and transferred to the National Ignition Facility (NIF) as a National Ignition Campaign diagnostic. The WRF measures the spectrum of protons from D-(3)He reactions in tuning-campaign implosions containing D and (3)He gas; in this work we report on the first proton spectroscopy measurement on the NIF using WRFs. The energy downshift of the 14.7-MeV proton is directly related to the total ρR through the plasma stopping power. Additionally, the shock proton yield is measured, which is a metric of the final merged shock strength.

  11. Ionic Strength, Surface Charge, and Packing Density Effects on the Properties of Peptide Self-Assembled Monolayers.

    Science.gov (United States)

    Leo, Norman; Liu, Juan; Archbold, Ian; Tang, Yongan; Zeng, Xiangqun

    2017-02-28

    The various environmental parameters of packing density, ionic strength, and solution charge were examined for their effects on the properties of the immobilized peptide mimotope CH19 (CGSGSGSQLGPYELWELSH) that binds with the therapeutic antibody Trastuzumab (Herceptin) on a gold substrate. The immobilization of CH19 onto gold was examined with a quartz crystal microbalance (QCM). The QCM data showed the presence of intermolecular interactions resulting in the increase of viscoelastic properties of the peptide self-assembled monolayer (SAM). The CH19 SAM was diluted with CS7 (CGSGSGS) to decrease the packing density as CH19/CS7. The packing density and ionic strength parameters were evaluated by atomic force microscopy (AFM), ellipsometry, and QCM. AFM and ellipsometry showed a distinct conformational difference between CH19 and CH19/CS7, indicating a relationship between packing density and conformational state of the immobilized peptide. The CH19 SAM thickness was 40 Å with a rough topology, while the CH19/CS7 SAM thickness was 20 Å with a smooth topology. The affinity studies showed that the affinity of CH19 and CH19/CS7 to Trastuzumab were both on the order of 10(7) M(-1) in undiluted PBS buffer, while the dilution of the buffer by 1000× increased both SAMs affinities to Trastuzumab to the order of 10(15) M(-2) and changed the binding behavior from noncooperative to cooperative binding. This indicated that ionic strength had a more pronounced effect on binding properties of the CH19 SAM than packing density. Electrochemical impedance spectroscopy (EIS) was conducted on the CH19/CS7 SAM, which showed an increase in impedance after each EIS measurement cycle. Cyclic voltammetry on the CH19/CS7 SAM decreased impedance to near initial values. The impact of the packing density, buffer ionic strength, and local charge perturbation of the peptide SAM properties was interpreted based on the titratable sites in CH19 that could participate in the proton transfer and

  12. Charge carrier density dependence of the hole mobility in poly(p-phenylene vinylene)

    NARCIS (Netherlands)

    Tanase, C; Blom, PWM; de Leeuw, DM; Meijer, EJ

    2004-01-01

    The hole transport in various poly(p-phenylene vinylene) (PPV) derivatives has been investigated in field-effect transistors (FETs) and light-emitting diodes (LEDs) as a function of temperature and applied bias. The discrepancy between the experimental hole mobilities extracted from FETs and LEDs ba

  13. Demographic models reveal the shape of density dependence for a specialist insect herbivore on variable host plants.

    Science.gov (United States)

    Miller, Tom E X

    2007-07-01

    1. It is widely accepted that density-dependent processes play an important role in most natural populations. However, persistent challenges in our understanding of density-dependent population dynamics include evaluating the shape of the relationship between density and demographic rates (linear, concave, convex), and identifying extrinsic factors that can mediate this relationship. 2. I studied the population dynamics of the cactus bug Narnia pallidicornis on host plants (Opuntia imbricata) that varied naturally in relative reproductive effort (RRE, the proportion of meristems allocated to reproduction), an important plant quality trait. I manipulated per-plant cactus bug densities, quantified subsequent dynamics, and fit stage-structured models to the experimental data to ask if and how density influences demographic parameters. 3. In the field experiment, I found that populations with variable starting densities quickly converged upon similar growth trajectories. In the model-fitting analyses, the data strongly supported a model that defined the juvenile cactus bug retention parameter (joint probability of surviving and not dispersing) as a nonlinear decreasing function of density. The estimated shape of this relationship shifted from concave to convex with increasing host-plant RRE. 4. The results demonstrate that host-plant traits are critical sources of variation in the strength and shape of density dependence in insects, and highlight the utility of integrated experimental-theoretical approaches for identifying processes underlying patterns of change in natural populations.

  14. Image Charge and Electric Field Effects on Hydrogen-like Impurity-bound Polaron Energies and Oscillator Strengths in a Quantum Dot

    Science.gov (United States)

    Vardanyan, L. A.; Vartanian, A. L.; Asatryan, A. L.; Kirakosyan, A. A.

    2016-11-01

    By using Landau-Pekar variational method, the ground and the first excited state energies and the transition frequencies between the ground and the first excited states of a hydrogen-like impurity-bound polaron in a spherical quantum dot (QD) have been studied by taking into account the image charge effect (ICE). We employ the dielectric continuum model to describe the phonon confinement effects. The oscillator strengths (OSs) of transitions from the 1 s-like state to excited states of 2 s, 2 p x , and 2 p z symmetries are calculated as functions of the applied electric field and strength of the confinement potential. We have shown that with and without image charge effect, the increase of the strength of the parabolic confinement potential leads to the increase of the oscillator strengths of 1 s - 2 p x and 1 s - 2 p z transitions. This indicates that the energy differences between 1 s- and 2 p x - as well as 1 s- and 2 p z -like states have a dominant role determining the oscillator strength. Although there is almost no difference in the oscillator strengths for transitions 1 s - 2 p x and 1 s -2 p z when the image charge effect is not taken into account, it becomes significant with the image charge effect.

  15. Impact of density-dependent symmetry energy and Coulomb interactions on the evolution of intermediate mass fragments

    Indian Academy of Sciences (India)

    Karan Singh Vinayak; Suneel Kumar

    2014-03-01

    Within the framework of isospin-dependent quantum molecular dynamics (IQMD) model, we demonstrate the evolution of intermediate mass fragments in heavy-ion collisions. In this paper, we study the time evolution, impact parameter, and excitation energy dependence of IMF production for the different forms of density-dependent symmetry energy. The IMF production and charge distribution show a minor but considerable sensitivity towards various forms of densitydependent symmetry energy. The Coulomb interactions affect the IMF production significantly at peripheral collisions. The IMF production increases with the stiffness of symmetry energy.

  16. 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.

  17. 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

    2017-02-27

    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

  18. A scale of metal ion binding strengths correlating with ionic charge, Pauling electronegativity, toxicity, and other physiological effects.

    Science.gov (United States)

    Kinraide, Thomas B; Yermiyahu, Uri

    2007-09-01

    Equilibrium constants for binding to plant plasma membranes have been reported for several metal ions, based upon adsorption studies and zeta-potential measurements. LogK values for the ions are these: Al(3+), 4.30; La(3+), 3.34; Cu(2+), 2.60; Ca(2+) and Mg(2+), 1.48; Na(+) and K(+), 0 M(-1). These values correlate well with logK values for ion binding to many organic and inorganic ligands. LogK values for metal ion binding to 12 ligands were normalized and averaged to produce a scale for the binding of 49 ions. The scale correlates well with the values presented above (R(2)=0.998) and with ion binding to cell walls and other biomass. The scale is closely related to the charge (Z) and Pauling electronegativity (PE) of 48 ions (all but Hg(2+)); R(2)=0.969 for the equation (Scale values)=-1.68+Z(1.22+0.444PE). Minimum rhizotoxicity of metal ions appears to be determined by binding strengths: log a(PM,M)=1.60-2.41exp[0.238(Scale values)] determines the value of ion activities at the plasma membrane surface (a(PM,M)) that will ensure inhibition of root elongation. Additional toxicity appears to be related to softness, accounting for the great toxicity of Ag(+), for example. These binding-strength values correlate with additional physiological effects and are suitable for the computation of cell-surface electrical potentials.

  19. $\\beta$- decay of $^{58}$Zn. A critical test for the charge-exchange reaction as a probe for the $\\beta$- decay strength distribution

    CERN Multimedia

    2002-01-01

    % IS353 \\\\ \\\\ Due to its importance in fundamental physics and astrophysics, a great effort both theoretically and experimentally is devoted to study Gamow Teller (GT)-strength. The GT-strength and its distribution play a key role in late stellar evolution. During the pre-supernova core-collapse of massive stars, the electron capture and nuclear $\\beta$ -decay determine the electron-to-baryon ratio, which influences the infall dynamics and the mass of the final core. The cross-section of the charge-exchange reaction at forward angles with energies above 100~MeV is expected to be proportional to the squares of Fermi and GT matrix elements. This proportionality should provide a Q-value free method to probe the weak interaction strength and renormalization effects in nuclei. Thus charge-exchange reactions are often used to determine the experimental GT-strength. However, the connection between the GT-strength and the cross-section of the charge-exchange reaction is partially model-dependent and the question aris...

  20. Regional differences in density-dependent mortality and reproduction in Finnish reindeer

    Directory of Open Access Journals (Sweden)

    Ilpo Kojola

    1993-10-01

    Full Text Available Reindeer in the southern and central regions of reindeer husbandry in Finland feed on arboreal lichens or are given supplementary rations from midwinter whereas in the northern region reindeer use snow-covered forage throughout winter. Rates of mortality and reproduction were examined using data from population crashes of semi-domesticated reindeer that occurred in Northern Finland during 1960-1987. The mortality and reproductive rate were density-dependent in the southern region and the mortality was density-dependent in the central region. The density-dependence was most probably due to food competition in forest cutting areas where reindeer gather to feed on arboreal lichens from felled trees. In the northern region mortality was not density-dependent indicating that where reindeer feed on over-utilized winter range the effects of increased feeding competition are masked by very large changes in the availability of forage.

  1. 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.

  2. Density-dependent prophylaxis and condition-dependent immune function in Lepidopteran larvae: a multivariate approach

    OpenAIRE

    Cotter, Sheena; Hails, R. S.; Cory, J S; Wilson, K.

    2004-01-01

    1. The risk of parasitism and infectious disease is expected to increase with population density as a consequence of positive density-dependent transmission rates. Therefore, species that encounter large fluctuations in population density are predicted to exhibit plasticity in their immune system, such that investment in costly immune defences is adjusted to match the probability of exposure to parasites and pathogens (i.e. density-dependent prophylaxis).

  3. Habitat- and density-dependent demography of a colonial raptor in Mediterranean agro-ecosystems

    OpenAIRE

    2016-01-01

    Agricultural intensification is considered the major cause of decline in farmland bird populations, especially in the Mediterranean region. Food shortage increased by the interaction between agricultural intensification and density-dependent mechanisms could influence the population dynamics of colonial birds.Weused demographic data on lesser kestrels (Falco naumanni), a key species of Mediterranean pseudo-steppes, to understand the importance of land-use changes and density-dependent mechani...

  4. 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.

  5. Adult trees cause density-dependent mortality in conspecific seedlings by regulating the frequency of pathogenic soil fungi.

    Science.gov (United States)

    Liang, Minxia; Liu, Xubing; Gilbert, Gregory S; Zheng, Yi; Luo, Shan; Huang, Fengmin; Yu, Shixiao

    2016-12-01

    Negative density-dependent seedling mortality has been widely detected in tropical, subtropical and temperate forests, with soil pathogens as a major driver. Here we investigated how host density affects the composition of soil pathogen communities and consequently influences the strength of plant-soil feedbacks. In field censuses of six 1-ha permanent plots, we found that survival was much lower for newly germinated seedlings that were surrounded by more conspecific adults. The relative abundance of pathogenic fungi in soil increased with increasing conspecific tree density for five of nine tree species; more soil pathogens accumulated around roots where adult tree density was higher, and this greater pathogen frequency was associated with lower seedling survival. Our findings show how tree density influences populations of soil pathogens, which creates plant-soil feedbacks that contribute to community-level and population-level compensatory trends in seedling survival.

  6. Recent works carried out at the IDIEM by the group in charge of probabilistic strength of materials

    Directory of Open Access Journals (Sweden)

    Kittl, P.

    1990-09-01

    Full Text Available This updating review describes, from the conceptual standpoint, all the research works so far carried out at the IDIEM by the group in charge of Probabilistic Strength of Materials as well as research activities under way at present. This description considers three aspects. First, the general purposes of the commented discipline and the discussion of its theoretical foundations are presented. In the second place, an analysis is conducted in connection with materials subjected to diverse stresses of tension, compression, shearing, bending, torsion, eccentrical bending, and also subjected to buckling, eccentrical compressive and eccentrical tensile stresses: in all these cases the pertaining parameters of Weibull's function are determined. Thirdly, sundry engineering applications of said discipline are set out in such fields as, for example, soil mechanics, rock mechanics, seismology, nuclear reactors industry, fatigue, and concrete pavements. At last a brief description of research work now in progress is given.

    Se describen, desde un punto de vista conceptual, todos los trabajos desarrollados hasta la fecha por el grupo de Resistencia Probabilística de Materiales del IDIEM así como los que están actualmente en ejecución. Se consideran tres aspectos en la descripción. En primer lugar, se comentan los objetivos generales de la disciplina discutiendo su fundamentación teórica. En segundo lugar, se analizan casos de materiales sometidos a esfuerzos de tracción, compresión, corte, flexión, torsión, flexión excéntrica, pandeo, compresión y tracción excéntricas y la consecuente determinación de los parámetros de la función de Weibull en todos ellos. En tercer lugar, se mencionan las aplicaciones que esta disciplina tiene en la ingeniería, tales como en: mecánica de suelos, mecánica de rocas, fatiga, pavimentos de hormigón, sismología, industria nuclear, entre otras. Por último, se hace una sucinta descripción de los

  7. Density dependence of the /s-wave repulsion in pionic atoms

    Science.gov (United States)

    Friedman, E.

    2002-11-01

    Several mechanisms of density dependence of the s-wave repulsion in pionic atoms, beyond the conventional model, are tested by parameter fits to a large (106 points) set of data from 16O to 238U, including 'deeply bound' states in 205Pb. Special attention is paid to the proper choice of nuclear density distributions. A density-dependent isovector scattering amplitude suggested recently by Weise to result from a density dependence of the pion decay constant is introduced and found to account for most of the so-called anomalous repulsion. The presence of such an effect might indicate partial chiral symmetry restoration in dense matter. The anomalous repulsion is fully accounted for when an additional relativistic impulse approximation term is included in the potential.

  8. 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.

  9. Radial oscillations of magnetized proto strange stars in temperature- and density-dependent quark mass model

    Indian Academy of Sciences (India)

    V K Gupta; Asha Gupta; S Singh; J D Anand

    2003-10-01

    We report on the study of the mass–radius (–) relation and the radial oscillations of magnetized proto strange stars. For the quark matter we have employed the very recent modification, the temperature- and density-dependent quark mass model of the well-known density-dependent quark mass model. We find that the effect of magnetic field, both on the maximum mass and radial frequencies, is rather small. Also a proto strange star, whether magnetized or otherwise, is more likely to evolve into a strange star rather than transform into a black hole.

  10. A spatial interpretation of the density dependence model in industrial demography

    NARCIS (Netherlands)

    van Wissen, L

    2004-01-01

    In this paper the density dependence model, which was developed in organizational ecology, is compared to the economic-geographical notion of agglomeration economies. There is a basic resemblance: both involve some form of positive feedback between size of the population and growth. The paper explor

  11. Maxwell equation violation by density dependent magnetic fields in neutron stars

    CERN Document Server

    Menezes, Débora P

    2016-01-01

    We show that the widely used density dependent magnetic field prescriptions, necessary to account for the variation of the field intensity from the crust to the core of neutron stars violate one of the Maxwell equations. We estimate how strong the violation is when different equations of state are used and check for which cases the pathological problem can be cured.

  12. Negative density dependence of seed dispersal and seedling recruitment in a Neotropical palm

    NARCIS (Netherlands)

    Jansen, Patrick A.; Visser, Marco D.; Wright, S. Joseph; Rutten, Gemma; Muller-Landau, Helene C.

    2014-01-01

    Negative density dependence (NDD) of recruitment is pervasive in tropical tree species. We tested the hypotheses that seed dispersal is NDD, due to intraspecific competition for dispersers, and that this contributes to NDD of recruitment. We compared dispersal in the palm Attalea butyracea across a

  13. Investigation of a growth model incorporating density dependence for the mackerel management plan simulations

    NARCIS (Netherlands)

    Brunel, T.P.A.

    2015-01-01

    This report presents a framework to model density dependent growth for the North East Atlantic mackerel. The model used is the classical von Bertalanffy equation, but modified so that growth is reduced when stock size increases. The model developed was able to reproduce quite closely the trends in t

  14. Density dependent state space model for population abundance data with unequal time intervals

    Science.gov (United States)

    Dennis, Brian; Ponciano, José Miguel

    2014-01-01

    The Gompertz state-space (GSS) model is a stochastic model for analyzing time series observations of population abundances. The GSS model combines density dependence, environmental process noise, and observation error toward estimating quantities of interest in biological monitoring and population viability analysis. However, existing methods for estimating the model parameters apply only to population data with equal time intervals between observations. In the present paper, we extend the GSS model to data with unequal time intervals, by embedding it within a state-space version of the Ornstein-Uhlenbeck process, a continuous-time model of an equilibrating stochastic system. Maximum likelihood and restricted maximum likelihood calculations for the Ornstein-Uhlenbeck state-space model involve only numerical maximization of an explicit multivariate normal likelihood, and so the extension allows for easy bootstrapping, yielding confidence intervals for model parameters, statistical hypothesis testing of density dependence, and selection among sub-models using information criteria. Ecologists and managers previously drawn to models lacking density dependence or observation error because such models accommodated unequal time intervals (for example, due to missing data) now have an alternative analysis framework incorporating density dependence, process noise and observation error. PMID:25230459

  15. 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...

  16. Age-specific density-dependent survival in Mediterranean Gulls Larus melanocephalus

    NARCIS (Netherlands)

    te Marvelde, Luc; Meininger, Peter L.; Flamant, Renaud; Dingemanse, Niels J.

    2009-01-01

    Survival and reproductive rates often decrease with increasing population density. Such negative density dependence reflects a changing net balance between the benefits and costs of presence of others with increasing density. When densities are low, however, survival and reproductive rates might inc

  17. Density dependent hadron field theory for asymmetric nuclear matter and exotic nuclei

    NARCIS (Netherlands)

    Hofmann, F. Keil; Lenske, H.

    2001-01-01

    Published in: Phys. Rev. C 64 (2001) , pp.034314 citations recorded in [Science Citation Index] Abstract: The density dependent relativistic hadron field (DDRH) theory is applied to strongly asymmetric nuclear matter and finite nuclei far off stability. A new set of in-medium meson-nucleon vertices

  18. Stochastic seasonality and nonlinear density-dependent factors regulate population size in an African rodent

    DEFF Research Database (Denmark)

    Leirs, Herwig; Steneth, Nils Chr.; Nichols, James D.

    1997-01-01

    , but clear examples of both processes acting in the same population are rare(7,8). Key-factor analysis (regression of population changes on possible causal factors) and time-series analysis are often used to investigate the presence of density dependence, but such approaches may be biased and provide...

  19. Charge transport in polycrystalline alumina materials: application to the optimization of dielectric breakdown strength; Transport de charges dans les alumines polycristallines: application a l'optimisation de la rigidite dielectrique

    Energy Technology Data Exchange (ETDEWEB)

    Touzin, M.

    2005-12-15

    Dielectric breakdown constitutes an important limitation in the use of insulating materials under high-tension since it leads to the local fusion and the sublimation of material. The microstructure (average grain size, intergranular phase) has a great influence on the ability of material to resist this catastrophic phenomenon. Indeed, the interfaces between the various phases constitute potential sites of trapping for the charges. The optimization of the dielectric breakdown strength of a polycrystalline alumina sintered with a liquid phase passes necessarily through the control of the microstructural parameters. Thus, it is shown that by controlling the conditions of the process (rate of sintering aids, powder grain size and thermal cycle), it is possible to control the density (by the average grain size) but also the nature (by the crystallization or not of anorthite) of the grain boundaries. The study of the influence of these two parameters as well temperature on the properties of charge transport and storage was carried out by methods ICM and SEMME. The results, interpreted in light of the numerical simulation of the charge transport in bulk alumina sample during electron beam irradiation, allowed to highlight behaviors, and the corresponding microstructures, favourable to the dielectric breakdown resistance according to the considered temperature. Thus, at room temperature a high density of interfaces (low grain size and crystallized intergranular phase) makes it possible material to durably trap a great amount of charges, which leads to a high dielectric strength. On the other hand, at higher temperature, the presence of shallow traps (vitreous intergranular phase) supports the charge diffusion and makes it possible to delay breakdown. (author)

  20. Gamow-Teller strength in deformed nuclei within the self-consistent charge-exchange quasi-particle random-phase approximation with the Gogny force

    CERN Document Server

    Martini, M; Goriely, S

    2014-01-01

    The charge-exchange excitations in nuclei are studied within the fully self-consistent proton-neutron quasiparticle random-phase approximation using the finite-range Gogny interaction. No additional parameters beyond those included in the effective nuclear force are included. Axially symmetric deformations are consistently taken into account, both in the description of the ground states and spin-isospin excitations. We focus on the isobaric analog and Gamow-Teller resonances. A comparison of the predicted strength distributions to the existing experimental data is presented and the role of nuclear deformation analyzed. The Gamow-Teller strength is used to estimate the beta-decay half-life of nuclei for which experimental data exist. A satisfactory agreement with experimental half-lives is found and justifies the additional study of the exotic neutron-rich N=82, 126 and 184 isotonic chains of relevance for the r-process nucleosynthesis.

  1. Charge-changing transitions and capture strengths of pf-shell nuclei with $T_{z} = -2$ at proton drip-line

    CERN Document Server

    Rahman, Muneeb-Ur

    2016-01-01

    Charge-changing transitions, commonly referred to as Gamow-Teller (GT) transitions, and electron capture/$\\beta^{+}$-decay strengths for pf-shell nuclei with $T_{z} = - 2$ at proton drip-line have been calculated using the proton-neutron quasi-particle random phase approximation (pn-QRPA) model. The total GT$_{+}$ strength values and electron capture/$\\beta^{+}$-decay rates are needed for the study of the late stages of the stellar evolution. The pn-QRPA theory is used for a microscopic calculation of GT strength distribution functions and associated stellar electron capture/$\\beta^{+}$-decay rates of proton-rich pf-shell nuclei with $T_{z} = - 2$ in the mass range 46 $\\leq$ A $\\leq$ 56 at proton drip-line. Standard quenching factor of 0.74, usually implemented in the shell model calculation, has been incorporated for the comparison with experimental data (wherever available). The calculated GT strength of the two proton-rich nuclei, $^{52}$Ni and $^{56}$Zn are compared with experimental data of corresponding...

  2. 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...... applied a Bayesian state-space model to a 72-year time series of abundance counts. While accounting for known harvest (as well as live removal) from the population, we found that the bison population in southern Utah exhibited strong potential to grow from low density (β0 = 0.26; Bayesian credible...... interval based on 95% of the highest posterior density: BCI = 0.19 to 0.33), and weak but statistically significant density dependence (β1 = -0.02, BCI = -0.04 to -0.004). Early spring temperatures also had strong positive effects on population growth (βfebaprtemp1 = 0.09, BCI = 0.04 to 0.14), much more so...

  3. Competitive effects of nuclear deformation and density dependence of $\\Lambda\\!N$ interaction

    CERN Document Server

    Isaka, M; Rijken, T h A

    2016-01-01

    Competitive effects of nuclear deformation and density dependence of $\\Lambda\\!N$-interaction in $\\Lambda$ binding energies $B_\\Lambda$ of hypernuclei are studied systematically on the basis of the baryon-baryon interaction model ESC including many-body effects. By using the $\\Lambda\\!N$ G-matrix interaction derived from ESC, we perform microscopic calculations of $B_\\Lambda$ in $\\Lambda$ hypernuclei within the framework of the antisymmetrized molecular dynamics under the averaged-density approximation. The calculated values of $B_\\Lambda$ reproduce experimental data within a few hundred keV in the wide mass regions from 9 to 51. It is found that competitive effects of nuclear deformation and density dependence of $\\Lambda\\!N$-interaction work decisively for fine tuning of $B_\\Lambda$ values.

  4. Hybrid stars Spin polarised nuclear matter and density dependent quark masses

    CERN Document Server

    Maheswari, V S U; Samaddar, S K

    1998-01-01

    The possibility of formation of a droplet phase (DP) inside a star and its consequences on the structural properties of the star are investigated. For nuclear matter (NM), an equation of state (EOS) based on finite range, momentum and density dependent interaction, and which predicts that neutron matter undergoes ferromagnetic transition at densities realisable inside the neutron star is employed. An EOS for quark matter (QM) with density dependent quark masses, the so-called effective mass model, is constructed by correctly treating the quark chemical potentials. It is then found that a droplet phase consisting of strange quark matter and unpolarised nuclear matter sandwiched between a core of polarised nuclear matter and a crust containing unpolarised nuclear matter exists. Moreover, we could explain the mass and surface magnetic field satisfactorily, and as well allow, due to the presence of a droplet phase, the direct URCA process to happen.

  5. Postcatastrophe population dynamics and density dependence of an endemic island duck

    Science.gov (United States)

    Seavy, N.E.; Reynolds, M.H.; Link, W.A.; Hatfield, J.S.

    2009-01-01

    Laysan ducks (Anas laysanensis) are restricted to approximately 9 km2 in the Northwestern Hawaiian Islands, USA. To evaluate the importance of density dependence for Laysan ducks, we conducted a Bayesian analysis to estimate the parameters of a Gompertz model and the magnitude of process variation and observation error based on the fluctuations in Laysan duck abundance on Laysan Island from 1994 to 2007. This model described a stationary distribution for the population at carrying capacity that fluctuates around a long-term mean of 456 ducks and is between 316 to 636 ducks 95% of the time. This range of expected variability can be used to identify changes in population size that warn of catastrophic events. Density-dependent population dynamics may explain the recovery of Laysan duck from catastrophic declines and allow managers to identify population monitoring thresholds.

  6. Study of Proto Strange Stars (PSS) in Temperature and Density Dependent Quark Mass Model

    CERN Document Server

    Gupta, V K; Singh, S; Anand, J D; Gupta, Asha

    2003-01-01

    We report on the study of the mass-radius (M-R) relation and the radial oscillations of proto strange stars. For the quark matter we have employed the well known density dependent quark mass model and its very recent modification, the temperature and density dependent quark mass model. We find that the maximum mass the star can support increases significantly with the temperature of the star in this model which implies that transition to a black hole at the early stage of formation of the star is inhibited. As for the neutrinos, we find, contrary to the expectation that the M-R and oscillation frequencies are almost independent of the neutrino chemical potentials.

  7. Density-dependent prey mortality is determined by the spatial scale of predator foraging.

    Science.gov (United States)

    McCarthy, Erin K; White, J Wilson

    2016-02-01

    Foraging theory predicts which prey patches predators should target. However, in most habitats, what constitutes a 'patch' and how prey density is calculated are subjective concepts and depend on the spatial scale at which the predator (or scientist) is observing. Moreover, the predator's 'foraging scale' affects prey population dynamics: predators should produce directly density-dependent (DDD) prey mortality at the foraging scale, but inversely density-dependent (IDD) mortality (safety-in-numbers) at smaller scales. We performed the first experimental test of these predictions using behavioral assays with guppies (Poecilia reticulata) feeding on bloodworm 'prey' patches. The guppy's foraging scale had already been estimated in a prior study. Our experimental results confirmed theoretical predictions: predation was IDD when prey were aggregated at a scale smaller than the foraging scale, but not when prey were aggregated at larger scales. These results could be used to predict outcomes of predator-prey interactions in continuous, non-discrete habitats in the field.

  8. Nuclear Density-Dependent Effective Coupling Constants in the Mean-Field Theory

    CERN Document Server

    Lee, J H; Lee, S J; Lee, Jae Hwang; Lee, Young Jae; Lee, Suk-Joon

    1996-01-01

    It is shown that the equation of state of nuclear matter can be determined within the mean-field theory of $\\sigma \\omega$ model provided only that the nucleon effective mass curve is given. We use a family of the possible nucleon effective mass curves that reproduce the empirical saturation point in the calculation of the nuclear binding energy curves in order to obtain density-dependent effective coupling constants. The resulting density-dependent coupling constants may be used to study a possible equation of state of nuclear system at high density or neutron matter. Within the constraints used in this paper to $M^*$ of nuclear matter at saturation point and zero density, neutron matter of large incompressibility is strongly bound at high density while soft neutron matter is weakly bound at low density. The study also exhibits the importance of surface vibration modes in the study of nuclear equation of state.

  9. Density-dependent changes in effective area occupied for sea-bottom-associated marine fishes

    DEFF Research Database (Denmark)

    Thorson, James T.; Rindorf, Anna; Gao, Jin

    2016-01-01

    The spatial distribution of marine fishes can change for many reasons, including density-dependent distributional shifts. Previous studies show mixed support for either the proportional-density model (PDM; no relationship between abundance and area occupied, supported by ideal-free distribution...... theory) or the basin model (BM; positive abundance–area relationship, supported by density-dependent habitat selection theory). The BM implies that fishes move towards preferred habitat as the population declines. We estimate the average relationship using bottom trawl data for 92 fish species from six...... marine regions, to determine whether the BM or PDM provides a better description for sea-bottom-associated fishes. We fit a spatio-temporal model and estimate changes in effective area occupied and abundance, and combine results to estimate the average abundance–area relationship as well as variability...

  10. Population-level consequences of heterospecific density-dependent movements in predator-prey systems

    OpenAIRE

    2013-01-01

    In this paper we elucidate how small-scale movements, such as those associated with searching for food and avoiding predators, affect the stability of predator-prey dynamics. We investigate an individual-based Lotka-Volterra model with density dependent movement, in which the predator and prey populations live in a very large number of coupled patches. The rates at which individuals leave patches depend on the local densities of heterospecifics, giving rise to one reaction norm for each of th...

  11. Remark on compressible Navier-Stokes equations with density-dependent viscosity and discontinuous initial data

    Science.gov (United States)

    Zhang, Ting; Fang, Daoyuan

    2008-03-01

    In this paper, we study the free boundary problem for 1D compressible Navier-Stokes equations with density-dependent viscosity. We focus on the case where the viscosity coefficient vanishes on vacuum. We prove the global existence and uniqueness for discontinuous solutions to the Navier-Stokes equations when the initial density is a bounded variation function, and give a decay result for the density as t-->+[infinity].

  12. Density dependence in an age-structured population of great tits: identifying the critical age classes.

    Science.gov (United States)

    Gamelon, Marlène; Grøtan, Vidar; Engen, Steinar; Bjørkvoll, Eirin; Visser, Marcel E; Saether, Bernt-Erik

    2016-09-01

    Classical approaches for the analyses of density dependence assume that all the individuals in a population equally respond and equally contribute to density dependence. However, in age-structured populations, individuals of different ages may differ in their responses to changes in population size and how they contribute to density dependence affecting the growth rate of the whole population. Here we apply the concept of critical age classes, i.e., a specific scalar function that describes how one or a combination of several age classes affect the demographic rates negatively, in order to examine how total density dependence acting on the population growth rate depends on the age-specific population sizes. In a 38-yr dataset of an age-structured great tit (Parus major) population, we find that the age classes, including the youngest breeding females, were the critical age classes for density regulation. These age classes correspond to new breeders that attempt to take a territory and that have the strongest competitive effect on other breeding females. They strongly affected population growth rate and reduced recruitment and survival rates of all breeding females. We also show that depending on their age class, females may differently respond to varying density. In particular, the negative effect of the number of breeding females was stronger on recruitment rate of the youngest breeding females. These findings question the classical assumptions that all the individuals of a population can be treated as having an equal contribution to density regulation and that the effect of the number of individuals is age independent. Our results improve our understanding of density regulation in natural populations.

  13. 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.

  14. Density-dependent nerve growth factor regulation of Gs-alpha RNA in pheochromocytoma 12 cells.

    Science.gov (United States)

    Tjaden, G; Aguanno, A; Kumar, R; Benincasa, D; Gubits, R M; Yu, H; Dolan, K P

    1990-01-01

    Nerve growth factor (NGF) affects levels of the alpha subunit of the stimulatory G protein (Gs-alpha) in pheochromocytoma 12 cells in a bidirectional, density-dependent manner. Cells grown at high density responded to NGF treatment with increased levels of Gs-alpha mRNA and protein. Conversely, in cells grown in low-density cultures, levels of this mRNA were lowered by NGF treatment. Images PMID:2160599

  15. -selection, -selection, effectiveness, and tolerance in competition: density-dependent selection revisited

    Indian Academy of Sciences (India)

    Amitabh Joshi; N. G. Prasad; Mallikarjun Shakarad

    2001-08-01

    In the Drosophila literature, selection for faster development and selection for adapting to high density are often confounded, leading, for example, to the expectation that selection for faster development should also lead to higher competitive ability. At the same time, results from experimental studies on evolution at high density do not agree with many of the predictions from classical density-dependent selection theory. We put together a number of theoretical and empirical results from the literature, and some new experimental results on Drosophila populations successfully subjected to selection for faster development, to argue for a broader interpretation of density-dependent selection. We show that incorporating notions of -selection, and the division of competitive ability into effectiveness and tolerance components, into the concept of density-dependent selection yields a formulation that allows for a better understanding of the empirical results. We also use this broader formulation to predict that selection for faster development in Drosophila should, in fact, lead to the correlated evolution of decreased competitive ability, even though it does lead to the evolution of greater efficiency and higher population growth rates at high density when in monotypic culture.

  16. Native birds and alien insects: spatial density dependence in songbird predation of invading oak gallwasps.

    Directory of Open Access Journals (Sweden)

    Karsten Schönrogge

    Full Text Available Revealing the interactions between alien species and native communities is central to understanding the ecological consequences of range expansion. Much has been learned through study of the communities developing around invading herbivorous insects. Much less, however, is known about the significance of such aliens for native vertebrate predators for which invaders may represent a novel food source. We quantified spatial patterns in native bird predation of invading gall-inducing Andricus wasps associated with introduced Turkey oak (Quercus cerris at eight sites across the UK. These gallwasps are available at high density before the emergence of caterpillars that are the principle spring food of native insectivorous birds. Native birds showed positive spatial density dependence in gall attack rates at two sites in southern England, foraging most extensively on trees with highest gall densities. In a subsequent study at one of these sites, positive spatial density dependence persisted through four of five sequential week-long periods of data collection. Both patterns imply that invading galls are a significant resource for at least some native bird populations. Density dependence was strongest in southern UK bird populations that have had longest exposure to the invading gallwasps. We hypothesise that this pattern results from the time taken for native bird populations to learn how to exploit this novel resource.

  17. Bayesian Inference on the Effect of Density Dependence and Weather on a Guanaco Population from Chile

    Science.gov (United States)

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E.; Colchero, Fernando

    2014-01-01

    Understanding the mechanisms that drive population dynamics is fundamental for management of wild populations. The guanaco (Lama guanicoe) is one of two wild camelid species in South America. We evaluated the effects of density dependence and weather variables on population regulation based on a time series of 36 years of population sampling of guanacos in Tierra del Fuego, Chile. The population density varied between 2.7 and 30.7 guanaco/km2, with an apparent monotonic growth during the first 25 years; however, in the last 10 years the population has shown large fluctuations, suggesting that it might have reached its carrying capacity. We used a Bayesian state-space framework and model selection to determine the effect of density and environmental variables on guanaco population dynamics. Our results show that the population is under density dependent regulation and that it is currently fluctuating around an average carrying capacity of 45,000 guanacos. We also found a significant positive effect of previous winter temperature while sheep density has a strong negative effect on the guanaco population growth. We conclude that there are significant density dependent processes and that climate as well as competition with domestic species have important effects determining the population size of guanacos, with important implications for management and conservation. PMID:25514510

  18. Travelling Waves for a Density Dependent Diffusion Nagumo Equation over the Real Line

    Institute of Scientific and Technical Information of China (English)

    Robert A. Van Gorder

    2012-01-01

    We consider the density dependent diffusion Nagumo equation, where the diffusion coefficient is a simple power function. This equation is used in modelling electrical pulse propagation in nerve axons and in population genetics (amongst other areas). In the present paper, the δ-expansion method is applied to a travelling wave reduction of the problem, so that we may obtain globally valid perturbation solutions (in the sense that the perturbation solutions are valid over the entire infinite domain, not just locally; hence the results are a generalization of the local solutions considered recently in the literature). The resulting boundary value problem is solved on the real line subject to conditions at z →±∞. Whenever a perturbative method is applied, it is important to discuss the accuracy and convergence properties of the resulting perturbation expansions. We compare our results with those of two different numerical methods (designed for initial and boundary value problems, respectively) and deduce that the perturbation expansions agree with the numerical results after a reasonable number of iterations. Finally, we are able to discuss the influence of the wave speed c and the asymptotic concentration value α on the obtained solutions. Upon recasting the density dependent diffusion Nagumo equation as a two-dimensional dynamical system, we are also able to discuss the influence of the nonlinear density dependence (which is governed by a power-law parameter m) on oscillations of the travelling wave solutions.

  19. A consumer-resource approach to the density-dependent population dynamics of mutualism

    Science.gov (United States)

    Holland, J. Nathaniel; DeAngelis, Donald L.

    2010-01-01

    Like predation and competition, mutualism is now recognized as a consumer resource (C-R) interaction, including, in particular, bi-directional (e.g., coral, plant- mycorrhizae) and uni-directional (e.g., ant-plant defense, plant-pollinator) C-R mutualisms. Here, we develop general theory for the density-dependent population dynamics of mutualism based on the C-R mechanism of interspecific interaction. To test the influence of C-R interactions on the dynamics and stability of bi- and uni-directional C-R mutualisms, we developed simple models that link consumer functional response of one mutualistic species with the resources supplied by another. Phase-plane analyses show that the ecological dynamics of C-R mutualisms are stable in general. Most transient behavior leads to an equilibrium of mutualistic coexistence, at which both species densities are greater than in the absence of interactions. However, due to the basic nature of C-R interactions, certain density-dependent conditions can lead to C-R dynamics characteristic of predator-prey interactions, in which one species overexploits and causes the other to go extinct. Consistent with empirical phenomena, these results suggest that the C-R interaction can provide a broad mechanism for understanding density-dependent population dynamics of mutualism. By unifying predation, competition, and mutualism under the common ecological framework of consumer-resource theory, we may also gain a better understanding of the universal features of interspecific interactions in general.

  20. Assessing the impact of density dependence in field populations of Aedes aegypti.

    Science.gov (United States)

    Walsh, R K; Facchinelli, L; Ramsey, J M; Bond, J G; Gould, F

    2011-12-01

    Although many laboratory studies of intra-specific competition have been conducted with Ae. aegypti, there have been few studies in natural environments and none that examined density dependence in natural containers at normal field densities. Additionally, current mathematical models that predict Ae. aegypti population dynamics lack empirically-based functions for density-dependence. We performed field experiments in Tapachula, Mexico, where dengue is a significant public health concern. Twenty-one containers with natural food and water that already contained larvae were collected from local houses. Each container was divided in half and the naturally occurring larvae were apportioned in a manner that resulted in one side of the container (high density) having four times the density of the second side (low density). Larvae were counted and pupae were removed daily. Once adults emerged, wing span was measured to estimate body size. Density had a significant impact on larval survival, adult body size, and the time taken to transition from 4(th) instar to pupation. Increased density decreased larval survival by 20% and decreased wing length by an average of 0.19 mm. These results provide a starting point for a better understanding of density dependence in field populations of Ae. aegypti.

  1. Computer-aided model analysis for ionic strength-dependent effective charge of protein in ion-exchange chromatography

    DEFF Research Database (Denmark)

    Lim, Young-il; Jørgensen, Sten Bay; Kim, In-Ho

    2005-01-01

    A packed-bed chromatographic model developed in this study includes adsorption isotherms considering steric mass action (SMA) as well as non-linearity in liquid/solid phases, adsorption kinetics and mass transport. For solving the nonlinear and nonequilibrium adsorption model described by a partial...... differential algebraic equation (PDAE) system, a fast and accurate numerical method (i.e., conservation element/solution element (CE/SE) method), is proposed. Sensitivity and elasticity of the model parameters (e.g., steric/shape factors, adsorption heat coefficient, effective protein charge, equilibrium...

  2. Density-dependence and within-host competition in a semelparous parasite of leaf-cutting ants

    Directory of Open Access Journals (Sweden)

    Thomsen Lene

    2004-11-01

    Full Text Available Abstract Background Parasite heterogeneity and within-host competition are thought to be important factors influencing the dynamics of host-parasite relationships. Yet, while there have been many theoretical investigations of how these factors may act, empirical data is more limited. We investigated the effects of parasite density and heterogeneity on parasite virulence and fitness using four strains of the entomopathogenic fungus, Metarhizium anisopliae var. anisopliae, and its leaf-cutting ant host Acromyrmex echinatior as the model system. Results The relationship between parasite density and infection was sigmoidal, with there being an invasion threshold for an infection to occur (an Allee effect. Although spore production was positively density-dependent, parasite fitness decreased with increasing parasite density, indicating within-host scramble competition. The dynamics differed little between the four strains tested. In mixed infections of three strains the infection-growth dynamics were unaffected by parasite heterogeneity. Conclusions The strength of within-host competition makes dispersal the best strategy for the parasite. Parasite heterogeneity may not have effected virulence or the infection dynamics either because the most virulent strain outcompeted the others, or because the interaction involved scramble competition that was impervious to parasite heterogeneity. The dynamics observed may be common for virulent parasites, such as Metarhizium, that produce aggregated transmission stages. Such parasites make useful models for investigating infection dynamics and the impact of parasite competition.

  3. Density-dependent natal dispersal patterns in a leopard population recovering from over-harvest.

    Directory of Open Access Journals (Sweden)

    Julien Fattebert

    Full Text Available Natal dispersal enables population connectivity, gene flow and metapopulation dynamics. In polygynous mammals, dispersal is typically male-biased. Classically, the 'mate competition', 'resource competition' and 'resident fitness' hypotheses predict density-dependent dispersal patterns, while the 'inbreeding avoidance' hypothesis posits density-independent dispersal. In a leopard (Panthera pardus population recovering from over-harvest, we investigated the effect of sex, population density and prey biomass, on age of natal dispersal, distance dispersed, probability of emigration and dispersal success. Over an 11-year period, we tracked 35 subadult leopards using VHF and GPS telemetry. Subadult leopards initiated dispersal at 13.6 ± 0.4 months. Age at commencement of dispersal was positively density-dependent. Although males (11.0 ± 2.5 km generally dispersed further than females (2.7 ± 0.4 km, some males exhibited opportunistic philopatry when the population was below capacity. All 13 females were philopatric, while 12 of 22 males emigrated. Male dispersal distance and emigration probability followed a quadratic relationship with population density, whereas female dispersal distance was inversely density-dependent. Eight of 12 known-fate females and 5 of 12 known-fate male leopards were successful in settling. Dispersal success did not vary with population density, prey biomass, and for males, neither between dispersal strategies (philopatry vs. emigration. Females formed matrilineal kin clusters, supporting the resident fitness hypothesis. Conversely, mate competition appeared the main driver for male leopard dispersal. We demonstrate that dispersal patterns changed over time, i.e. as the leopard population density increased. We conclude that conservation interventions that facilitated local demographic recovery in the study area also restored dispersal patterns disrupted by unsustainable harvesting, and that this indirectly improved

  4. Predictions of Taylor's power law, density dependence and pink noise from a neutrally modeled time series.

    Science.gov (United States)

    Keil, Petr; Herben, Tomás; Rosindell, James; Storch, David

    2010-07-07

    There has recently been increasing interest in neutral models of biodiversity and their ability to reproduce the patterns observed in nature, such as species abundance distributions. Here we investigate the ability of a neutral model to predict phenomena observed in single-population time series, a study complementary to most existing work that concentrates on snapshots in time of the whole community. We consider tests for density dependence, the dominant frequencies of population fluctuation (spectral density) and a relationship between the mean and variance of a fluctuating population (Taylor's power law). We simulated an archipelago model of a set of interconnected local communities with variable mortality rate, migration rate, speciation rate, size of local community and number of local communities. Our spectral analysis showed 'pink noise': a departure from a standard random walk dynamics in favor of the higher frequency fluctuations which is partly consistent with empirical data. We detected density dependence in local community time series but not in metacommunity time series. The slope of the Taylor's power law in the model was similar to the slopes observed in natural populations, but the fit to the power law was worse. Our observations of pink noise and density dependence can be attributed to the presence of an upper limit to community sizes and to the effect of migration which distorts temporal autocorrelation in local time series. We conclude that some of the phenomena observed in natural time series can emerge from neutral processes, as a result of random zero-sum birth, death and migration. This suggests the neutral model would be a parsimonious null model for future studies of time series data.

  5. Non-formation of vacuum states for Navier-Stokes equations with density-dependent viscosity

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We consider the Cauchy problem, free boundary problem and piston problem for one-dimensional compressible Navier-Stokes equations with density-dependent viscosity. Using the reduction to absurdity method, we prove that the weak solutions to these systems do not exhibit vacuum states, provided that no vacuum states are present initially. The essential requirements on the solutions are that the mass and energy of the fluid are locally integrable at each time, and the Lloc1-norm of the velocity gradient is locally integrable in time.

  6. Extended density-dependent mortality in mature conifer forests: causes and implications for ecosystem management.

    Science.gov (United States)

    Gendreau-Berthiaume, Benoit; Macdonald, S Ellen; Stadt, J John

    2016-07-01

    Understanding processes driving mortality in forests is important for comprehension of natural stand dynamics and for informing natural disturbance-based ecosystem management. There has been considerable study of mortality in forests during the self-thinning phase but we know much less about processes driving mortality in stands at later successional stages. We addressed this through study of five 1-ha spatially explicit permanent plots in mature (111-186 yr old in 2012) Pinus contorta stands in the Canadian Rocky Mountains using data from repeated measurements over a 45-yr period, dendrochronological information, and point pattern analysis. We tested the hypothesis that these stands had completed the self-thinning/density-dependent mortality stage of succession. Contrary to our expectations, the self-thinning phase can persist for more than 140 yr following stand establishment. Our findings suggest this was attributable to prolonged post-fire establishment periods due to surface fires in three of the plots while in the other two plots moist conditions and slow growth most likely delayed the onset of competition. Several pieces of evidence indicated the importance of density-dependent mortality in these stands over the study period: (1) The diameter distribution of individuals changed from initially right-skewed toward normality as a result of mortality of smaller-diameter stems. (2) Individuals of lower canopy positions were proportionally more affected by mortality. (3) When compared to the pre-mortality pattern, surviving stems in all stands had an increasingly uniform spatial distribution. In two of the plots, recent windthrow and/or ingrowth initially hindered our ability to detect density-dependent mortality but our dendrochronological sampling and permanent plot data allowed us to untangle the different processes at play; in doing so we demonstrate for the first time how density-independent processes can mask underlying density-dependent mortality

  7. Bulk viscosity of strange quark matter in density dependent quark mass model

    Indian Academy of Sciences (India)

    J D Anand; N Chandrika Devi; V K Gupta; S Singh

    2000-05-01

    We have studied the bulk viscosity of strange quark matter in the density dependent quark mass model (DDQM) and compared results with calculations done earlier in the MIT bag model where , masses were neglected and first order interactions were taken into account. We find that at low temperatures and high relative perturbations, the bulk viscosity is higher by 2 to 3 orders of magnitude while at low perturbations the enhancement is by 1–2 order of magnitude as compared to earlier results. Also the damping time is 2–3 orders of magnitude lower implying that the star reaches stability much earlier than in MIT bag model calculations.

  8. Density-dependent population dynamics in larvae of the dragonfly Pachydiplax longipennis: a field experiment.

    Science.gov (United States)

    Van Buskirk, J

    1987-05-01

    Several features of dragonfly population biology suggest that population regulation occurs in the larval stage. This study was designed to determine if density-dependent interactions among larval odonates can affect survival, growth and emergence. First-instar larvae of the dragonfly Pachydiplax longipennis were raised in outdoor experimental ponds at initial densities of 38, 152, and 608 larvae · m(-2), under two levels of food availability. Food availability was supplemented in half the pools by volumetric addition of zooplankton every other day. Pools in the low food treatment did not receive the zooplankton supplement.There was a strong negative effect of density on the mean growth rate of survivors, which included both emerging tenerals and individuals overwintering in the larval stage. A higher proportion emerged from low density than high density pools. Metamorphs from high density populations were smaller and emerged slightly later than those from low density, but the absolute number of metamorphs did not differ significantly among density treatments. Food supplementation significantly increased the proportion of overwintering larvae. There were no significant food-by-density interactions, indicating that food and density acted independently on larval population dynamics. Density-dependent mechanisms can clearly contribute to odonate population regulation, especially by controlling the number of larvae which emerge and the average age at reproduction. Population-level responses to density may be a result of interference among larvae.

  9. Larval density dependence in Anopheles gambiae s.s., the major African vector of malaria

    Science.gov (United States)

    Muriu, Simon M.; Coulson, Tim; Mbogo, Charles M.; Godfray, H. Charles J.

    2017-01-01

    Summary Anopheles gambiae sensu stricto is the most important vector of malaria in Africa although relatively little is known about the density-dependent processes determining its population size.Mosquito larval density was manipulated under semi-natural conditions using artificial larval breeding sites placed in the field in coastal Kenya; two experiments were conducted: one manipulating the density of a single cohort of larvae across a range of densities and the other employing fewer densities but with the treatments crossed with four treatments manipulating predator access.In the first experiment, larval survival, development rate and the size of the adult mosquito all decreased with larval density (controlling for block effects between 23% and 31% of the variance in the data could be explained by density).In the second experiment, the effects of predator manipulation were not significant, but again we observed strong density dependence in larval survival (explaining 30% of the variance).The results are compared with laboratory studies of A. gambiae larval competition and the few other studies conducted in the field, and the consequences for malaria control are discussed PMID:23163565

  10. The Oxygen Charge-state Ratio as an Indicator of Footpoint Field Strength in the Source Regions of the Solar Wind

    Science.gov (United States)

    Wang, Y.-M.

    2016-12-01

    Because of its distinctive compositional properties and high variability, the slow solar wind is widely believed to originate from coronal streamers, unlike high-speed wind, which emanates from coronal holes. Based on measurements from the Advanced Composition Explorer, it has been proposed that an oxygen charge-state ratio O7+/O6+ of 0.145 is the threshold that separates streamer from coronal hole wind. During the 2007-2009 sunspot minimum, however, the median value of O7+/O6+ fell to only 0.06, implying that almost all of the near-Earth wind came from coronal holes, despite the fact that the streamer belt lay much closer to the ecliptic plane at that time than at solar maximum. Employing extrapolations of photospheric field maps to derive the footpoint field strengths B 0 of the near-Earth wind, we find that the median value of B 0 decreased to only 2.6 G during 2007-2009, from a value of 21 G during 1998-2004. The factor of ˜2 decrease in the median value of O7+/O6+ thus reflects the factor of ˜8 decrease in the footpoint field strength. Variations in O7+/O6+ are strongly anticorrelated with the wind speed on timescales of days, but not on long timescales, which are dominated by changes in B 0. We suggest that the charge-state ratio is determined by the amount of energy deposited near the coronal base, which in turn depends on B 0 and the local flux-tube expansion rate. High values of O7+/O6+ are associated with rapidly diverging flux tubes rooted just inside the boundaries of coronal holes with strong footpoint fields.

  11. Calix[4]arene-linked bisporphyrin hosts for fullerenes: binding strength, solvation effects, and porphyrin-fullerene charge transfer bands.

    Science.gov (United States)

    Hosseini, Ali; Taylor, Steven; Accorsi, Gianluca; Armaroli, Nicola; Reed, Christopher A; Boyd, Peter D W

    2006-12-13

    A calix[4]arene scaffolding has been used to construct bisporphyrin ("jaws" porphyrin) hosts for supramolecular binding of fullerene guests. Fullerene affinities were optimized by varying the nature of the covalent linkage of the porphyrins to the calixarenes. Binding constants for C60 and C70 in toluene were explored as a function of substituents at the periphery of the porphyrin, and 3,5-di-tert-butylphenyl groups gave rise to the highest fullerene affinities (26,000 M(-1) for C60). The origin of this high fullerene affinity has been traced to differential solvation effects rather than to electronic effects. Studies of binding constants as a function of solvent (toluene solubility, indicating that desolvation of the fullerene is a major factor determining the magnitude of binding constants. The energetics of fullerene binding have been determined in terms of DelatH and DeltaS and are consistent with an enthalpy-driven, solvation-dependent process. A direct relationship between supramolecular binding of a fullerene guest to a bisporphyrin host and the appearance of a broad NIR absorption band have been established. The energy of this band moves in a predictable manner as a function of the electronic structure of the porphyrin, thereby establishing its origin in porphyrin-to-fullerene charge transfer.

  12. Charge heterogeneity profiling of monoclonal antibodies using low ionic strength ion-exchange chromatography and well-controlled pH gradients on monolithic columns.

    Science.gov (United States)

    Talebi, Mohammad; Nordborg, Anna; Gaspar, Andras; Lacher, Nathan A; Wang, Qian; He, Xiaoping Z; Haddad, Paul R; Hilder, Emily F

    2013-11-22

    In this work, the suitability of employing shallow pH gradients generated using single component buffer systems as eluents through cation-exchange (CEX) monolithic columns is demonstrated for the high-resolution separation of monoclonal antibody (mAb) charge variants in three different biopharmaceuticals. A useful selection of small molecule buffer species is described that can be used within very narrow pH ranges (typically 1 pH unit) defined by their buffer capacity for producing controlled and smooth pH profiles when used together with porous polymer monoliths. Using very low ionic strength eluents also enabled direct coupling with electrospray ionisation mass spectrometry. The results obtained by the developed pH gradient approach for the separation of closely related antibody species appear to be consistent with those obtained by imaged capillary isoelectric focusing (iCE) in terms of both resolution and separation profile. Both determinants of resolution, i.e., peak compression and peak separation contribute to the gains in resolution, evidently through the Donnan potential effect, which is increased by decreasing the eluent concentration, and also through the way electrostatic charges are distributed on the protein surface. Retention mechanisms based on the trends observed in retention of proteins at pH values higher than the electrophoretic pI are also discussed using applicable theories. Employing monolithic ion-exchangers is shown to enable fast method development, short analysis time, and high sample throughput owing to the accelerated mass transport of the monolithic media. The possibility of short analysis time, typically less than 15 min, and high sample throughput is extremely useful in the assessment of charge-based changes to the mAb products, such as during manufacturing or storage.

  13. Testing predictions of the Janzen-Connell hypothesis: a meta-analysis of experimental evidence for distance- and density-dependent seed and seedling survival.

    Science.gov (United States)

    Comita, Liza S; Queenborough, Simon A; Murphy, Stephen J; Eck, Jenalle L; Xu, Kaiyang; Krishnadas, Meghna; Beckman, Noelle; Zhu, Yan; Gómez-Aparicio, Lorena

    2014-07-01

    The Janzen-Connell hypothesis proposes that specialist natural enemies, such as herbivores and pathogens, maintain diversity in plant communities by reducing survival rates of conspecific seeds and seedlings located close to reproductive adults or in areas of high conspecific density. Variation in the strength of distance- and density-dependent effects is hypothesized to explain variation in plant species richness along climatic gradients, with effects predicted to be stronger in the tropics than the temperate zone and in wetter habitats compared to drier habitats.We conducted a comprehensive literature search to identify peer-reviewed experimental studies published in the 40+ years since the hypothesis was first proposed. Using data from these studies, we conducted a meta-analysis to assess the current weight of evidence for the distance and density predictions of the Janzen-Connell hypothesis.Overall, we found significant support for both the distance- and density-dependent predictions. For all studies combined, survival rates were significantly reduced near conspecifics compared to far from conspecifics, and in areas with high densities of conspecifics compared to areas with low conspecific densities. There was no indication that these results were due to publication bias.The strength of distance and density effects varied widely among studies. Contrary to expectations, this variation was unrelated to latitude, and there was no significant effect of study region. However, we did find a trend for stronger distance and density dependence in wetter sites compared to sites with lower annual precipitation. In addition, effects were significantly stronger at the seedling stage compared to the seed stage.Synthesis. Our study provides support for the idea that distance- and density-dependent mortality occurs in plant communities world-wide. Available evidence suggests that natural enemies are frequently the cause of such patterns, consistent with the Janzen

  14. Non-swarming grasshoppers exhibit density-dependent phenotypic plasticity reminiscent of swarming locusts.

    Science.gov (United States)

    Gotham, Steven; Song, Hojun

    2013-11-01

    Locusts are well known for exhibiting an extreme form of density-dependent phenotypic plasticity known as locust phase polyphenism. At low density, locust nymphs are cryptically colored and shy, but at high density they transform into conspicuously colored and gregarious individuals. Most of what we know about locust phase polyphenism come from the study of the desert locust Schistocerca gregaria (Forskål), which is a devastating pest species affecting many countries in North Africa and the Middle East. The desert locust belongs to the grasshopper genus Schistocerca Stål, which includes mostly non-swarming, sedentary species. Recent phylogenetic studies suggest that the desert locust is the earliest branching lineage within Schistocerca, which raises a possibility that the presence of density-dependent phenotypic plasticity may be a plesiomorphic trait for the whole genus. In order to test this idea, we have quantified the effect of rearing density in terms of the resulting behavior, color, and morphology in two non-swarming Schistocerca species native to Florida. When reared in both isolated and crowded conditions, the two non-swarming species, Schistocerca americana (Drury) and Schistocerca serialis cubense (Saussure) clearly exhibited plastic reaction norms in all traits measured, which were reminiscent of the desert locust. Specifically, we found that both species were more active and more attracted to each other when reared in a crowded condition than in isolation. They were mainly bright green in color when isolated, but developed strong black patterns and conspicuous background colors when crowded. We found a strong effect of rearing density in terms of size. There were also more mechanoreceptor hairs on the outer face of the hind femora in the crowded nymphs in both species. Although both species responded similarly, there were some clear species-specific differences in terms of color and behavior. Furthermore, we compare and contrast our findings with

  15. Negative density dependence of seed dispersal and seedling recruitment in a neotropical palm.

    Science.gov (United States)

    Jansen, Patrick A; Visser, Marco D; Joseph Wright, S; Rutten, Gemma; Muller-Landau, Helene C

    2014-09-01

    Negative density dependence (NDD) of recruitment is pervasive in tropical tree species. We tested the hypotheses that seed dispersal is NDD, due to intraspecific competition for dispersers, and that this contributes to NDD of recruitment. We compared dispersal in the palm Attalea butyracea across a wide range of population density on Barro Colorado Island in Panama and assessed its consequences for seed distributions. We found that frugivore visitation, seed removal and dispersal distance all declined with population density of A. butyracea, demonstrating NDD of seed dispersal due to competition for dispersers. Furthermore, as population density increased, the distances of seeds from the nearest adult decreased, conspecific seed crowding increased and seedling recruitment success decreased, all patterns expected under poorer dispersal. Unexpectedly, however, our analyses showed that NDD of dispersal did not contribute substantially to these changes in the quality of the seed distribution; patterns with population density were dominated by effects due solely to increasing adult and seed density.

  16. Rotochemical heating of millisecond and classical pulsars with anisotropic and density-dependent superfluid gap models

    CERN Document Server

    González-Jiménez, Nicolás; Reisenegger, Andreas

    2014-01-01

    When a rotating neutron star loses angular momentum, the progressive reduction of the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium, inducing reactions that release heat (rotochemical heating). This effect has previously been studied by Fern\\'andez & Reisenegger (2005) for non-superfluid neutron stars and by Petrovich & Reisenegger (2010) for superfluid millisecond pulsars. Both studies found that pulsars reach a quasi-steady state in which the compression driving the matter out of beta equilibrium is balanced by the reactions trying to restore the equilibrium. We extend previous studies by considering the effect of density-dependence and anisotropy of the superfluid energy gaps, for the case in which the dominant reactions are the modified Urca processes, the protons are non-superconducting, and the neutron superfluidity is parametrized by models proposed in the literature. By comparing our prediction...

  17. Asymmetry energy of nuclear matter: Temperature and density dependence, and validity of semi-empirical formula

    CERN Document Server

    Bordbar, G H; Taghizade, M

    2015-01-01

    In this work, we have done a completely microscopic calculation using a many-body variational method based on the cluster expansion of energy to compute the asymmetry energy of nuclear matter. In our calculations, we have employed the $AV_{18}$ nuclear potential. We have also investigated the temperature and density dependence of asymmetry energy. Our results show that the asymmetry energy of nuclear matter depends on both density and temperature. We have also studied the effects of different terms in the asymmetry energy of nuclear matter. These investigations indicate that at different densities and temperatures, the contribution of parabolic term is very substantial with respect to the other terms. Therefore, we can conclude that the parabolic approximation is a relatively good estimation, and our calculated binding energy of asymmetric nuclear matter is in a relatively good agreement with that of semi-empirical mass formula. However, for the accurate calculations, it is better to consider the effects of o...

  18. On the density dependent hadron field theory at finite temperature and its thermodynamical consistency

    CERN Document Server

    Avancini, S S; Chiapparini, M; Peres-Menezes, D

    2004-01-01

    In this work we study in a formal way the density dependent hadron field theory at finite temperature for nuclear matter. The thermodynamical potential and related quantities, as energy density and pressure are derived in two different ways. We first obtain the thermodynamical potential from the grand partition function, where the Hamiltonian depends on the density operator and is truncated at first order. We then reobtain the thermodynamical potential by calculating explicitly the energy density in a Thomas-Fermi approximation and considering the entropy of a fermi gas. The distribution functions for particles and antiparticles are the output of the minimization of the thermodynamical potential. It is shown that in the mean field theory the thermodynamical consistency is achieved. The connection with effective chiral lagrangians with Brown-Rho scaling is discussed.

  19. Isospin effects and the density dependence of the nuclear symmetry energy

    CERN Document Server

    Souza, S R; Carlson, B V; Donangelo, R; Lynch, W G; Steiner, A W

    2009-01-01

    The density dependence of the nuclear symmetry energy is inspected using the Statistical Multifragmentation Model with Skyrme effective interactions. The model consistently considers the expansion of the fragments' volumes at finite temperature at the freeze-out stage. By selecting parameterizations of the Skyrme force that lead to very different equations of state for the symmetry energy, we investigate the sensitivity of different observables to the properties of the effective forces. Our results suggest that, in spite of being sensitive to the thermal dilation of the fragments' volumes, it is difficult to distinguish among the Skyrme forces from the isoscaling analysis. On the other hand, the isotopic distribution of the emitted fragments turns out to be very sensitive to the force employed in the calculation.

  20. Half-Lives of Proton Emitters With a Deformed Density-Dependent Model

    Institute of Scientific and Technical Information of China (English)

    QIAN Yi-Bin; REN Zhong-Zhou; NI Dong-Dong; SHENG Zong-Qiang

    2010-01-01

    @@ Half-lives of proton radioactivity are investigated with a deformed density-dependent model. The single folding potential which is dependent on deformation and orientation is employed to calculate the proton decay width through the deformed potential barrier. In addition, the spectroscopic factor is taken into account in the calcu-lation, which is obtained in the relativistic mean field theory with NL3. The calculated results of semi-spherical nuclei are found to be in good agreement with the experimental data, and the results of well-deformed nuclei are also satisfactory. Moreover, a formula for the spherical proton emission half-life based on the Gamow quantum tunneling theory is presented.

  1. Turing bifurcation in a reaction-diffusion system with density-dependent dispersal

    Science.gov (United States)

    Kumar, Niraj; Horsthemke, Werner

    2010-05-01

    Motivated by the recent finding [N. Kumar, G.M. Viswanathan, V.M. Kenkre, Physica A 388 (2009) 3687] that the dynamics of particles undergoing density-dependent nonlinear diffusion shows sub-diffusive behaviour, we study the Turing bifurcation in a two-variable system with this kind of dispersal. We perform a linear stability analysis of the uniform steady state to find the conditions for the Turing bifurcation and compare it with the standard Turing condition in a reaction-diffusion system, where dispersal is described by simple Fickian diffusion. While activator-inhibitor kinetics are a necessary condition for the Turing instability as in standard two-variable systems, the instability can occur even if the diffusion constant of the inhibitor is equal to or smaller than that of the activator. We apply these results to two model systems, the Brusselator and the Gierer-Meinhardt model.

  2. Density-dependent changes in effective area occupied for sea-bottom-associated marine fishes.

    Science.gov (United States)

    Thorson, James T; Rindorf, Anna; Gao, Jin; Hanselman, Dana H; Winker, Henning

    2016-10-12

    The spatial distribution of marine fishes can change for many reasons, including density-dependent distributional shifts. Previous studies show mixed support for either the proportional-density model (PDM; no relationship between abundance and area occupied, supported by ideal-free distribution theory) or the basin model (BM; positive abundance-area relationship, supported by density-dependent habitat selection theory). The BM implies that fishes move towards preferred habitat as the population declines. We estimate the average relationship using bottom trawl data for 92 fish species from six marine regions, to determine whether the BM or PDM provides a better description for sea-bottom-associated fishes. We fit a spatio-temporal model and estimate changes in effective area occupied and abundance, and combine results to estimate the average abundance-area relationship as well as variability among taxa and regions. The average relationship is weak but significant (0.6% increase in area for a 10% increase in abundance), whereas only a small proportion of species-region combinations show a negative relationship (i.e. shrinking area when abundance increases). Approximately one-third of combinations (34.6%) are predicted to increase in area more than 1% for every 10% increase in abundance. We therefore infer that population density generally changes faster than effective area occupied during abundance changes. Gadiformes have the strongest estimated relationship (average 1.0% area increase for every 10% abundance increase) followed by Pleuronectiformes and Scorpaeniformes, and the Eastern Bering Sea shows a strong relationship between abundance and area occupied relative to other regions. We conclude that the BM explains a small but important portion of spatial dynamics for sea-bottom-associated fishes, and that many individual populations merit cautious management during population declines, because a compressed range may increase the efficiency of harvest.

  3. Survival kinetics of starving bacteria is biphasic and density-dependent.

    Directory of Open Access Journals (Sweden)

    Andy Phaiboun

    2015-04-01

    Full Text Available In the lifecycle of microorganisms, prolonged starvation is prevalent and sustaining life during starvation periods is a vital task. In the literature, it is commonly assumed that survival kinetics of starving microbes follows exponential decay. This assumption, however, has not been rigorously tested. Currently, it is not clear under what circumstances this assumption is true. Also, it is not known when such survival kinetics deviates from exponential decay and if it deviates, what underlying mechanisms for the deviation are. Here, to address these issues, we quantitatively characterized dynamics of survival and death of starving E. coli cells. The results show that the assumption--starving cells die exponentially--is true only at high cell density. At low density, starving cells persevere for extended periods of time, before dying rapidly exponentially. Detailed analyses show intriguing quantitative characteristics of the density-dependent and biphasic survival kinetics, including that the period of the perseverance is inversely proportional to cell density. These characteristics further lead us to identification of key underlying processes relevant for the perseverance of starving cells. Then, using mathematical modeling, we show how these processes contribute to the density-dependent and biphasic survival kinetics observed. Importantly, our model reveals a thrifty strategy employed by bacteria, by which upon sensing impending depletion of a substrate, the limiting substrate is conserved and utilized later during starvation to delay cell death. These findings advance quantitative understanding of survival of microbes in oligotrophic environments and facilitate quantitative analysis and prediction of microbial dynamics in nature. Furthermore, they prompt revision of previous models used to analyze and predict population dynamics of microbes.

  4. Resampling method for applying density-dependent habitat selection theory to wildlife surveys.

    Directory of Open Access Journals (Sweden)

    Olivia Tardy

    Full Text Available Isodar theory can be used to evaluate fitness consequences of density-dependent habitat selection by animals. A typical habitat isodar is a regression curve plotting competitor densities in two adjacent habitats when individual fitness is equal. Despite the increasing use of habitat isodars, their application remains largely limited to areas composed of pairs of adjacent habitats that are defined a priori. We developed a resampling method that uses data from wildlife surveys to build isodars in heterogeneous landscapes without having to predefine habitat types. The method consists in randomly placing blocks over the survey area and dividing those blocks in two adjacent sub-blocks of the same size. Animal abundance is then estimated within the two sub-blocks. This process is done 100 times. Different functional forms of isodars can be investigated by relating animal abundance and differences in habitat features between sub-blocks. We applied this method to abundance data of raccoons and striped skunks, two of the main hosts of rabies virus in North America. Habitat selection by raccoons and striped skunks depended on both conspecific abundance and the difference in landscape composition and structure between sub-blocks. When conspecific abundance was low, raccoons and striped skunks favored areas with relatively high proportions of forests and anthropogenic features, respectively. Under high conspecific abundance, however, both species preferred areas with rather large corn-forest edge densities and corn field proportions. Based on random sampling techniques, we provide a robust method that is applicable to a broad range of species, including medium- to large-sized mammals with high mobility. The method is sufficiently flexible to incorporate multiple environmental covariates that can reflect key requirements of the focal species. We thus illustrate how isodar theory can be used with wildlife surveys to assess density-dependent habitat selection

  5. Effect of minimum strength of mirror magnetic field (B sub m sub i sub n) on production of highly charged heavy ions from RIKEN liquid-He-free super conducting electron-cyclotron resonance ion source (RAMSES)

    CERN Document Server

    Arai, H; Lee, S M; Higurashi, Y; Nakagawa, T; Kidera, M; Kageyama, T; Kase, M; Yano, Y; Aihara, T

    2002-01-01

    We measured the beam intensity of highly charged heavy ions (O, Ar and Kr ions) as a function of the minimum strength of mirror magnetic field (B sub m sub i sub n) of the RIKEN liquid-He-free super conducting electron-cyclotron resonance ion source. In this experiment, we found that the optimum value of B sub m sub i sub n exists to maximize the beam intensity of highly charged heavy ions and the value was almost the same (approx 0.49 T) for various charge state heavy ions.

  6. Density-dependent role of an invasive marsh grass, Phragmites australis, on ecosystem service provision

    Science.gov (United States)

    Puckett, Brandon J.; Theuerkauf, Kathrynlynn W.; Theuerkauf, Ethan J.; Eggleston, David B.

    2017-01-01

    Invasive species can positively, neutrally, or negatively affect the provision of ecosystem services. The direction and magnitude of this effect can be a function of the invaders’ density and the service(s) of interest. We assessed the density-dependent effect of an invasive marsh grass, Phragmites australis, on three ecosystem services (plant diversity and community structure, shoreline stabilization, and carbon storage) in two oligohaline marshes within the North Carolina Coastal Reserve and National Estuarine Research Reserve System (NCNERR), USA. Plant species richness was equivalent among low, medium and high Phragmites density plots, and overall plant community composition did not vary significantly by Phragmites density. Shoreline change was most negative (landward retreat) where Phragmites density was highest (-0.40 ± 0.19 m yr-1 vs. -0.31 ± 0.10 for low density Phragmites) in the high energy marsh of Kitty Hawk Woods Reserve and most positive (soundward advance) where Phragmites density was highest (0.19 ± 0.05 m yr-1 vs. 0.12 ± 0.07 for low density Phragmites) in the lower energy marsh of Currituck Banks Reserve, although there was no significant effect of Phragmites density on shoreline change. In Currituck Banks, mean soil carbon content was approximately equivalent in cores extracted from low and high Phragmites density plots (23.23 ± 2.0 kg C m-3 vs. 22.81 ± 3.8). In Kitty Hawk Woods, mean soil carbon content was greater in low Phragmites density plots (36.63 ± 10.22 kg C m-3) than those with medium (13.99 ± 1.23 kg C m-3) or high density (21.61 ± 4.53 kg C m-3), but differences were not significant. These findings suggest an overall neutral density-dependent effect of Phragmites on three ecosystem services within two oligohaline marshes in different environmental settings within a protected reserve system. Moreover, the conceptual framework of this study can broadly inform an ecosystem services-based approach to invasive species management

  7. Density-dependent role of an invasive marsh grass, Phragmites australis, on ecosystem service provision.

    Science.gov (United States)

    Theuerkauf, Seth J; Puckett, Brandon J; Theuerkauf, Kathrynlynn W; Theuerkauf, Ethan J; Eggleston, David B

    2017-01-01

    Invasive species can positively, neutrally, or negatively affect the provision of ecosystem services. The direction and magnitude of this effect can be a function of the invaders' density and the service(s) of interest. We assessed the density-dependent effect of an invasive marsh grass, Phragmites australis, on three ecosystem services (plant diversity and community structure, shoreline stabilization, and carbon storage) in two oligohaline marshes within the North Carolina Coastal Reserve and National Estuarine Research Reserve System (NCNERR), USA. Plant species richness was equivalent among low, medium and high Phragmites density plots, and overall plant community composition did not vary significantly by Phragmites density. Shoreline change was most negative (landward retreat) where Phragmites density was highest (-0.40 ± 0.19 m yr-1 vs. -0.31 ± 0.10 for low density Phragmites) in the high energy marsh of Kitty Hawk Woods Reserve and most positive (soundward advance) where Phragmites density was highest (0.19 ± 0.05 m yr-1 vs. 0.12 ± 0.07 for low density Phragmites) in the lower energy marsh of Currituck Banks Reserve, although there was no significant effect of Phragmites density on shoreline change. In Currituck Banks, mean soil carbon content was approximately equivalent in cores extracted from low and high Phragmites density plots (23.23 ± 2.0 kg C m-3 vs. 22.81 ± 3.8). In Kitty Hawk Woods, mean soil carbon content was greater in low Phragmites density plots (36.63 ± 10.22 kg C m-3) than those with medium (13.99 ± 1.23 kg C m-3) or high density (21.61 ± 4.53 kg C m-3), but differences were not significant. These findings suggest an overall neutral density-dependent effect of Phragmites on three ecosystem services within two oligohaline marshes in different environmental settings within a protected reserve system. Moreover, the conceptual framework of this study can broadly inform an ecosystem services-based approach to invasive species management.

  8. Delineating effects of tensor force on the density dependence of nuclear symmetry energy

    CERN Document Server

    Xu, Chang; Li, Bao-An

    2012-01-01

    In this talk, we report results of our recent studies to delineate effects of the tensor force on the density dependence of nuclear symmetry energy within phenomenological models. The tensor force active in the isosinglet neutron-proton interaction channel leads to appreciable depletion/population of nucleons below/above the Fermi surface in the single-nucleon momentum distribution in cold symmetric nuclear matter (SNM). We found that as a consequence of the high momentum tail in SNM the kinetic part of the symmetry energy $E^{kin}_{sym}(\\rho)$ is significantly below the well-known Fermi gas model prediction of approximately $12.5 (\\rho/\\rho_0)^{2/3}$. With about 15% nucleons in the high momentum tail as indicated by the recent experiments at J-Lab by the CLAS Collaboration, the $E^{kin}_{sym}(\\rho)$ is negligibly small. It even becomes negative when more nucleons are in the high momentum tail in SNM. These features have recently been confirmed by three independent studies based on the state-of-the-art micros...

  9. Tri-trophic interactions affect density dependence of seed fate in a tropical forest palm.

    Science.gov (United States)

    Visser, Marco D; Muller-Landau, Helene C; Wright, S Joseph; Rutten, Gemma; Jansen, Patrick A

    2011-11-01

    Natural enemies, especially host-specific enemies, are hypothesised to facilitate the coexistence of plant species by disproportionately inflicting more damage at increasing host abundance. However, few studies have assessed such Janzen-Connell mechanisms on a scale relevant for coexistence and no study has evaluated potential top-down influences on the specialized pests. We quantified seed predation by specialist invertebrates and generalist vertebrates, as well as larval predation on these invertebrates, for the Neotropical palm Attalea butyracea across ten 4-ha plots spanning 20-fold variation in palm density. As palm density increased, seed attack by bruchid beetles increased, whereas seed predation by rodents held constant. But because rodent predation on bruchid larvae increased disproportionately with increasing palm density, bruchid emergence rates and total seed predation by rodents and bruchids combined were both density-independent. Our results demonstrate that top-down effects can limit the potential of host-specific insects to induce negative-density dependence in plant populations.

  10. Strange matter equation of state in the quark mass-density-dependent model

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, O.G. (Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La Plata (Argentina)); Lugones, G. (Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900 La Plata (Argentina))

    1995-02-15

    We study the properties and stability of strange matter at [ital T]=0 in the quark mass-density-dependent model for noninteracting quarks. We found a wide stability window'' for the values of the parameters ([ital C],[ital M][sub [ital s]0]) and the resulting equation of state at low densities is stiffer than that of the MIT bag model. At high densities it tends to the ultrarelativistic behavior expected because of the asymptotic freedom of quarks. The density of zero pressure is near the one predicted by the bag model and [ital not] shifted away as stated before; nevertheless, at these densities the velocity of sound is [approx]50% larger in this model than in the bag model. We have integrated the equations of stellar structure for strange stars with the present equation of state. We found that the mass-radius relation is very much the same as in the bag model, although it extends to more massive objects, due to the stiffening of the equation of state at low densities.

  11. Density-dependent productivity depression in Pyrenean Bearded Vultures: implications for conservation.

    Science.gov (United States)

    Carrete, Martina; Donázar, José A; Margalida, Antoni

    2006-10-01

    The main objective of many conservation programs is to increase population size by improving a species' survival and reproduction. However, density dependence of demographic parameters may confound this approach. In this study we used a 25-year data set on Bearded Vultures (Gypaetus barbatus) in Spain to evaluate the consequences of population growth on reproductive performance. Unlike its coefficient of variation (cv), mean annual productivity decreased with increasing population size. After controlling for territorial heterogeneity, productivity also was negatively related to the distance to the nearest conspecific breeding pair and to supplementary feeding points where floaters congregate. These results suggest that vulture populations are regulated as posited by the site-dependency hypothesis: as the population increases, average productivity decreases because progressively poorer territories are used. The combined effects of the shrinkage of territories and the presence of floaters around supplementary feeding points seem to be the main causes of productivity decline and are therefore the main determinants of territory quality. This has conservation implications, especially concerning the role of supplementary feeding points. Supplementary feeding should be reviewed given that its usefulness in reducing preadult mortality has not yet been proved and its effect on productivity, as our results suggest, is negative.

  12. Quark Matter at High Density based on Extended Confined-isospin-density-dependent-mass Model

    CERN Document Server

    Qauli, A I

    2016-01-01

    We investigate the effect of the inclusion of relativistic Coulomb terms in a confined-isospin-density-dependent-mass (CIDDM) model of strange quark matter (SQM). We found that if we include Coulomb term in scalar density form, SQM equation of state (EOS) at high densities is stiffer but if we include Coulomb term in vector density form is softer than that of standard CIDDM model. We also investigate systematically the role of each term of the extended CIDDM model. Compared with what was reported in Ref.~\\cite {ref:isospin}, we found the stiffness of SQM EOS is controlled by the interplay among the the oscillator harmonic, isospin asymmetry and Coulomb contributions depending on the parameter's range of these terms. We have found that the absolute stable condition of SQM and the mass of 2 $M_\\odot$ pulsars can constrain the parameter of oscillator harmonic $\\kappa_1$ $\\approx 0.53$ in the case Coulomb term excluded. If the Coulomb term is included, for the models with their parameters are consistent with SQM ...

  13. Modeling Changing Morphology and Density Dependent Groundwater Flow in a Dynamic Environment: case study

    Science.gov (United States)

    Huizer, Sebastian; Bierkens, Marc; Oude Essink, Gualbert

    2015-04-01

    The prospect of sea level rise and increase in extreme weather conditions has led to a new focus on coastal defense in the Netherlands. As an innovative solution for coastal erosion a mega-nourishment named the Sand Motor (or Sand Engine) has been constructed at the Dutch coast. This body of sand will be distributed slowly along the coastline by wind, waves and currents; keeping the coastal defense structures in place and creating a unique, dynamic environment with changing morphology over time. The large size and position of the Sand Motor might lead to a substantial increase of fresh ground water resources. This creates an opportunity to combine coastal protection with an increase of fresh water resources in coastal regions. With a three dimensional, density dependent, groundwater model the effects of changing morphology over time and the potential increase in fresh water availability have been studied. The preliminary model calculations show that in a period of 20 years volume of fresh water gradually increases to ca. 12 Mm3. In the nearby dune area 7-8 Mm3 is abstracted yearly, therefore the first results are promising in increasing fresh groundwater resources. More model calculations will be performed to investigate the sensitivity of the change in the fresh, brackish and salt water distribution.

  14. Density-dependent effective baryon-baryon interaction from chiral three-baryon forces

    Science.gov (United States)

    Petschauer, Stefan; Haidenbauer, Johann; Kaiser, Norbert; Meißner, Ulf-G.; Weise, Wolfram

    2017-01-01

    A density-dependent effective potential for the baryon-baryon interaction in the presence of the (hyper)nuclear medium is constructed, based on the leading (irreducible) three-baryon forces derived within SU(3) chiral effective field theory. We evaluate the contributions from three classes: contact terms, one-pion exchange and two-pion exchange. In the strangeness-zero sector we recover the known result for the in-medium nucleon-nucleon interaction. Explicit expressions for the ΛN in-medium potential in (asymmetric) nuclear matter are presented. Our results are suitable for implementation into calculations of (hyper)nuclear matter. In order to estimate the low-energy constants of the leading three-baryon forces we introduce the decuplet baryons as explicit degrees of freedom and construct the relevant terms in the minimal non-relativistic Lagrangian. With these, the constants are estimated through decuplet saturation. Utilizing this approximation we provide numerical results for the effect of the three-body force in symmetric nuclear matter and pure neutron matter on the ΛN interaction. A moderate repulsion that increases with density is found in comparison to the free ΛN interaction.

  15. Density-dependent predation influences the evolution and behavior of masquerading prey.

    Science.gov (United States)

    Skelhorn, John; Rowland, Hannah M; Delf, Jon; Speed, Michael P; Ruxton, Graeme D

    2011-04-19

    Predation is a fundamental process in the interaction between species, and exerts strong selection pressure. Hence, anti-predatory traits have been intensively studied. Although it has long been speculated that individuals of some species gain protection from predators by sometimes almost-uncanny resemblances to uninteresting objects in the local environment (such as twigs or stones), demonstration of antipredatory benefits to such "masquerade" have only very recently been demonstrated, and the fundamental workings of this defensive strategy remain unclear. Here we use laboratory experiments with avian predators and twig-mimicking caterpillars as masqueraders to investigate (i) the evolutionary dynamics of masquerade; and (ii) the behavioral adaptations associated with masquerade. We show that the benefit of masquerade declines as the local density of masqueraders relative to their models (twigs, in our system) increases. This occurs through two separate mechanisms: increasing model density both decreased predators' motivation to search for masqueraders, and made masqueraders more difficult to detect. We further demonstrated that masquerading organisms have evolved complex microhabitat selection strategies that allow them to best exploit the density-dependent properties of masquerade. Our results strongly suggest the existence of opportunity costs associated with masquerade. Careful evaluation of such costs will be vital to the development of a fuller understanding of both the distribution of masquerade across taxa and ecosystems, and the evolution of the life history strategies of masquerading prey.

  16. Reversal of density dependence of juvenile Littorina littorea (Gastropoda) growth in response to periphyton nutrient status

    Science.gov (United States)

    Sommer, Ulrich

    2001-05-01

    Experimental periphyton communities were grown in aquaria receiving media of differently enriched seawater (fully enriched, without Si enrichment, without N and P enrichment) and supplied differently with medium (batch and weekly replacement). Periphyton was subject to grazing by 1-6 individuals of juvenile Littorina littorea. Periphyton biomass was higher in the replacement aquaria than in the batch aquaria and higher in the full and the -Si medium than in the -NP medium. The N:C ratio of the periphyton increased with Littorina number in the batch aquaria and was unaffected by Littorina number in the replacement aquaria. Diatoms were most dominant in the -NP treatments and rarest in the -Si treatments. Chlorophytes were dominant in the -Si and the fully enriched treatments, but also Cyanobacteria contributed significantly to periphyton biomass in those treatments under nutrient replacement. Somatic growth of Littorina was negatively correlated to Littorina density in the replacement aquaria and positively density dependent in the batch aquaria. The latter is explained by improved food quality under stronger grazing pressure.

  17. Δ (1232 ) effects in density-dependent relativistic Hartree-Fock theory and neutron stars

    Science.gov (United States)

    Zhu, Zhen-Yu; Li, Ang; Hu, Jin-Niu; Sagawa, Hiroyuki

    2016-10-01

    The density-dependent relativistic Hartree-Fock (DDRHF) theory is extended to include Δ isobars for the study of dense nuclear matter and neutron stars. To this end, we solve the Rarita-Schwinger equation for spin-3/2 particle. Both the direct and exchange terms of the Δ isobars' self-energies are evaluated in detail. In comparison with the relativistic mean field theory (Hartree approximation), a weaker parameter dependence is found for DDRHF. An early appearance of Δ isobars is recognized at ρB˜0.28 fm-3, comparable with that of hyperons. Also, we find that the Δ isobars' softening of the equation of state is mainly due to the reduced Fock contributions from the coupling of the isoscalar mesons, while the pion contributions are negligibly small. We finally conclude that with typical parameter sets, neutron stars with Δ isobars in their interiors could be as heavy as the two massive pulsars whose masses are precisely measured, with slightly smaller radii than normal neutron stars.

  18. $\\Delta$ (1232) effects in density-dependent relativistic Hartree-Fock theory and neutron stars

    CERN Document Server

    Zhu, Zhen-Yu; Hu, Jin-Niu; Sagawa, Hiroyuki

    2016-01-01

    The density-dependent relativistic Hartree-Fock (DDRHF) theory is extended to include $\\Delta$-isobars for the study of dense nuclear matter and neutron stars. To this end, we solve the Rarita-Schwinger equation for spin-3/2 particle. Both the direct and exchange terms of the $\\Delta$-isobars' self-energies are evaluated in details. In comparison with the relativistic mean field theory (Hartree approximation), a weaker parameter dependence is found for DDRHF. An early appearance of $\\Delta$-isobars is recognized at $\\rho_B\\sim0.27$fm$^{-3}$, comparable with that of hyperons. Also, we find that the $\\Delta$-isobars' softening of the equation of state is found to be mainly due to the reduced Fock contributions from the coupling of the isoscalar mesons, while the pion contributions are found negligibly small. We finally conclude that with typical parameter sets, neutron stars with $\\Delta$-isobars in their interiors could be as heavy as the two massive pulsars whose masses are precisely measured, with slightly s...

  19. Negative density dependence regulates two tree species at later life stage in a temperate forest.

    Directory of Open Access Journals (Sweden)

    Tiefeng Piao

    Full Text Available Numerous studies have demonstrated that tree survival is influenced by negative density dependence (NDD and differences among species in shade tolerance could enhance coexistence via resource partitioning, but it is still unclear how NDD affects tree species with different shade-tolerance guilds at later life stages. In this study, we analyzed the spatial patterns for trees with dbh (diameter at breast height ≥2 cm using the pair-correlation g(r function to test for NDD in a temperate forest in South Korea after removing the effects of habitat heterogeneity. The analyses were implemented for the most abundant shade-tolerant (Chamaecyparis obtusa and shade-intolerant (Quercus serrata species. We found NDD existed for both species at later life stages. We also found Quercus serrata experienced greater NDD compared with Chamaecyparis obtusa. This study indicates that NDD regulates the two abundant tree species at later life stages and it is important to consider variation in species' shade tolerance in NDD study.

  20. Negative density dependence regulates two tree species at later life stage in a temperate forest.

    Science.gov (United States)

    Piao, Tiefeng; Chun, Jung Hwa; Yang, Hee Moon; Cheon, Kwangil

    2014-01-01

    Numerous studies have demonstrated that tree survival is influenced by negative density dependence (NDD) and differences among species in shade tolerance could enhance coexistence via resource partitioning, but it is still unclear how NDD affects tree species with different shade-tolerance guilds at later life stages. In this study, we analyzed the spatial patterns for trees with dbh (diameter at breast height) ≥2 cm using the pair-correlation g(r) function to test for NDD in a temperate forest in South Korea after removing the effects of habitat heterogeneity. The analyses were implemented for the most abundant shade-tolerant (Chamaecyparis obtusa) and shade-intolerant (Quercus serrata) species. We found NDD existed for both species at later life stages. We also found Quercus serrata experienced greater NDD compared with Chamaecyparis obtusa. This study indicates that NDD regulates the two abundant tree species at later life stages and it is important to consider variation in species' shade tolerance in NDD study.

  1. 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.

  2. Hippo signaling regulates microprocessor and links cell-density-dependent miRNA biogenesis to cancer.

    Science.gov (United States)

    Mori, Masaki; Triboulet, Robinson; Mohseni, Morvarid; Schlegelmilch, Karin; Shrestha, Kriti; Camargo, Fernando D; Gregory, Richard I

    2014-02-27

    Global downregulation of microRNAs (miRNAs) is commonly observed in human cancers and can have a causative role in tumorigenesis. The mechanisms responsible for this phenomenon remain poorly understood. Here, we show that YAP, the downstream target of the tumor-suppressive Hippo-signaling pathway regulates miRNA biogenesis in a cell-density-dependent manner. At low cell density, nuclear YAP binds and sequesters p72 (DDX17), a regulatory component of the miRNA-processing machinery. At high cell density, Hippo-mediated cytoplasmic retention of YAP facilitates p72 association with Microprocessor and binding to a specific sequence motif in pri-miRNAs. Inactivation of the Hippo pathway or expression of constitutively active YAP causes widespread miRNA suppression in cells and tumors and a corresponding posttranscriptional induction of MYC expression. Thus, the Hippo pathway links contact-inhibition regulation to miRNA biogenesis and may be responsible for the widespread miRNA repression observed in cancer.

  3. A density-dependent matrix model and its applications in optimizing harvest schemes

    Institute of Scientific and Technical Information of China (English)

    Guofan Shao; WANG Fei; DAI Limin; BAI Jianwei; LI Yingshan

    2006-01-01

    Based on temporal data collected from 36 re-measured plots, transition probabilities of trees from a diameter class to a higher class were analyzed for the broadleaved-Korean pine forest in the Changbai Mountains. It was found that the transition probabilities were related not only to diameter size but also to the total basal area of trees with the diameter class. This paper demonstrates the development of a density-dependent matrix model, DM2, and a series of simulations with it for forest stands with different conditions under different harvest schemes. After validations with independent field data, this model proved a suitable tool for optimization analysis of harvest schemes on computers. The optimum harvest scheme(s) can be determined by referring to stand growth, total timbers harvested, and size diversity changes over time. Three user-friendly interfaces were built with a forest management decision support system FORESTAR(R) for easy operations of DM2 by forest managers. This paper also summarizes the advantages and disadvantages of DM2.

  4. Density-dependent effective baryon-baryon interaction from chiral three-baryon forces

    CERN Document Server

    Petschauer, Stefan; Kaiser, Norbert; Meißner, Ulf-G; Weise, Wolfram

    2016-01-01

    A density-dependent effective potential for the baryon-baryon interaction in the presence of the (hyper)nuclear medium is constructed, based on the leading (irreducible) three-baryon forces derived within SU(3) chiral effective field theory. We evaluate the contributions from three classes: contact terms, one-pion exchange and two-pion exchange. In the strangeness-zero sector we recover the known result for the in-medium nucleon-nucleon interaction. Explicit expressions for the Lambda-nucleon in-medium potential in (asymmetric) nuclear matter are presented. Our results are suitable for implementation into calculations of (hyper)nuclear matter. In order to estimate the low-energy constants of the leading three-baryon forces we introduce the decuplet baryons as explicit degrees of freedom and construct the relevant terms in the minimal non-relativistic Lagrangian. With these, the constants are estimated through decuplet saturation. Utilizing this approximation we provide numerical results for the effect of the ...

  5. Kinetic modeling of rhamnolipid production by Pseudomonas aeruginosa PAO1 including cell density-dependent regulation.

    Science.gov (United States)

    Henkel, Marius; Schmidberger, Anke; Vogelbacher, Markus; Kühnert, Christian; Beuker, Janina; Bernard, Thomas; Schwartz, Thomas; Syldatk, Christoph; Hausmann, Rudolf

    2014-08-01

    The production of rhamnolipid biosurfactants by Pseudomonas aeruginosa is under complex control of a quorum sensing-dependent regulatory network. Due to a lack of understanding of the kinetics applicable to the process and relevant interrelations of variables, current processes for rhamnolipid production are based on heuristic approaches. To systematically establish a knowledge-based process for rhamnolipid production, a deeper understanding of the time-course and coupling of process variables is required. By combining reaction kinetics, stoichiometry, and experimental data, a process model for rhamnolipid production with P. aeruginosa PAO1 on sunflower oil was developed as a system of coupled ordinary differential equations (ODEs). In addition, cell density-based quorum sensing dynamics were included in the model. The model comprises a total of 36 parameters, 14 of which are yield coefficients and 7 of which are substrate affinity and inhibition constants. Of all 36 parameters, 30 were derived from dedicated experimental results, literature, and databases and 6 of them were used as fitting parameters. The model is able to describe data on biomass growth, substrates, and products obtained from a reference batch process and other validation scenarios. The model presented describes the time-course and interrelation of biomass, relevant substrates, and products on a process level while including a kinetic representation of cell density-dependent regulatory mechanisms.

  6. Determining the functional form of density dependence: deductive approaches for consumer-resource systems having a single resource.

    Science.gov (United States)

    Abrams, Peter A

    2009-09-01

    Consumer-resource models are used to deduce the functional form of density dependence in the consumer population. A general approach to determining the form of consumer density dependence is proposed; this involves determining the equilibrium (or average) population size for a series of different harvest rates. The relationship between a consumer's mortality and its equilibrium population size is explored for several one-consumer/one-resource models. The shape of density dependence in the resource and the shape of the numerical and functional responses all tend to be "inherited" by the consumer's density dependence. Consumer-resource models suggest that density dependence will very often have both concave and convex segments, something that is impossible under the commonly used theta-logistic model. A range of consumer-resource models predicts that consumer population size often declines at a decelerating rate with mortality at low mortality rates, is insensitive to or increases with mortality over a wide range of intermediate mortalities, and declines at a rapidly accelerating rate with increased mortality when mortality is high. This has important implications for management and conservation of natural populations.

  7. Parents benefit from eating offspring: density-dependent egg survivorship compensates for filial cannibalism.

    Science.gov (United States)

    Klug, Hope; Lindström, Kai; St Mary, Colette M

    2006-10-01

    Why should animals knowingly consume their own young? It is difficult to imagine many circumstances in which eating one's own young (i.e., filial cannibalism) actually increases an individual's fitness; however, filial cannibalism commonly co-occurs with parental care in fishes. The evolutionary significance of filial cannibalism remains unclear. The most commonly accepted explanation is that filial cannibalism is a mechanism by which caring males gain energy or nutrients that they reinvest into future reproduction, thereby increasing net reproductive success. There is mixed support for this hypothesis and, at best, it can only explain filial cannibalism in some species. A recent alternative hypothesis suggests that filial cannibalism improves the survivorship of remaining eggs by increasing oxygen availability, and thus increases current reproductive success. This theory has received little attention as of yet. We evaluated the hypothesis of oxygen-mediated filial cannibalism in the sand goby by examining the effect of oxygen and egg density on the occurrence of filial cannibalism, evaluating the effects of partial clutch cannibalism on the survivorship of remaining eggs, and comparing potential costs and benefits of filial cannibalism related to the net number of eggs surviving. Indeed, we found that oxygen level and egg density affected the occurrence of cannibalism and that simulated partial clutch cannibalism improved survivorship of the remaining eggs. Additionally, because increased egg survivorship, stemming from partial egg removal, compensated for the cost of cannibalism (i.e., number of eggs removed) at a range of cannibalism levels, filial cannibalism potentially results in no net losses in reproductive success. However, oxygen did not affect egg survivorship. Thus, we suggest a more general hypothesis of filial cannibalism mediated by density-dependent egg survivorship.

  8. Density-dependent reduction and induction of milkweed cardenolides by a sucking insect herbivore.

    Science.gov (United States)

    Martel, John W; Malcolm, Stephen B

    2004-03-01

    The effect of aphid population size on host-plant chemical defense expression and the effect of plant defense on aphid population dynamics were investigated in a milkweed-specialist herbivore system. Density effects of the aposematic oleander aphid, Aphis nerii, on cardenolide expression were measured in two milkweed species, Asclepias curassavica and A. incarnata. These plants vary in constitutive chemical investment with high mean cardenolide concentration in A. curassavica and low to zero in A. incarnata. The second objective was to determine whether cardenolide expression in these two host plants impacts mean A. nerii colony biomass (mg) and density. Cardenolide concentration (microgram/g) of A. curassavica in both aphid-treated leaves and opposite, herbivore-free leaves decreased initially in comparison with aphid-free controls, and then increased significantly with A. nerii density. Thus, A. curassavica responds to aphid herbivory initially with density-dependent phytochemical reduction, followed by induction of cardenolides to concentrations above aphid-free controls. In addition, mean cardenolide concentration of aphid-treated leaves was significantly higher than that of opposite, herbivore-free leaves. Therefore, A. curassavica induction is strongest in herbivore-damage tissue. Conversely, A. incarnata exhibited no such chemical response to aphid herbivory. Furthermore, neither host plant responded chemically to herbivore feeding duration time (days) or to the interaction between herbivore initial density and feeding duration time. There were also no significant differences in mean colony biomass or population density of A. nerii reared on high cardenolide (A. curassavica) and low cardenolide (A. incarnata) hosts.

  9. Counterintuitive density-dependent growth in a long-lived vertebrate after removal of nest predators.

    Science.gov (United States)

    Spencer, Ricky-John; Janzen, Fredric J; Thompson, Michael B

    2006-12-01

    Examining the phenotypic and genetic underpinnings of life-history variation in long-lived organisms is central to the study of life-history evolution. Juvenile growth and survival are often density dependent in reptiles, and theory predicts the evolution of slow growth in response to low resources (resource-limiting hypothesis), such as under densely populated conditions. However, rapid growth is predicted when exceeding some critical body size reduces the risk of mortality (mortality hypothesis). Here we present results of paired, large-scale, five-year field experiments to identify causes of variation in individual growth and survival rates of an Australian turtle (Emydura macquarii) prior to maturity. To distinguish between these competing hypotheses, we reduced nest predators in two populations and retained a control population to create variation in juvenile density by altering recruitment levels. We also conducted a complementary split-clutch field-transplant experiment to explore the impact of incubation temperature (25 degrees or 30 degrees C), nest predator level (low or high), and clutch size on juvenile growth and survival. Juveniles in high-recruitment (predator removal) populations were not resource limited, growing more rapidly than young turtles in the control populations. Our experiments also revealed a remarkably long-term impact of the thermal conditions experienced during embryonic development on growth of turtles prior to maturity. Moreover, this thermal effect was manifested in turtles approaching maturity, rather than in turtles closer to hatching, and was dependent on population density in the post-hatching rearing environment. This apparent phenotypic plasticity in growth complements our observation of a strong, positive genetic correlation between individual body size in the experimental and control populations over the first five years of life (rG - +0.77). Thus, these Australian pleurodiran turtles have the impressive capacity to

  10. Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus).

    Science.gov (United States)

    Vas, Judit; Andersen, Inger Lise

    2015-01-01

    Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus) in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e., distance travelled, nearest and furthest neighbour distance) and activity budgets (e.g., resting, feeding, social activities) were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period). The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation.

  11. Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus.

    Directory of Open Access Journals (Sweden)

    Judit Vas

    Full Text Available Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e., distance travelled, nearest and furthest neighbour distance and activity budgets (e.g., resting, feeding, social activities were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period. The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation.

  12. Quark matter at high density based on an extended confined isospin-density-dependent mass model

    Science.gov (United States)

    Qauli, A. I.; Sulaksono, A.

    2016-01-01

    We investigate the effect of the inclusion of relativistic Coulomb terms in a confined-isospin-density-dependent-mass (CIDDM) model of strange quark matter (SQM). We found that if we include the Coulomb term in scalar density form, the SQM equation of state (EOS) at high densities is stiffer but if we include the Coulomb term in vector density form it is softer than that of the standard CIDDM model. We also investigate systematically the role of each term of the extended CIDDM model. Compared with what was reported by Chu and Chen [Astrophys. J. 780, 135 (2014)], we found the stiffness of SQM EOS is controlled by the interplay among the oscillator harmonic, isospin asymmetry and Coulomb contributions depending on the parameter's range of these terms. We have found that the absolute stable condition of SQM and the mass of 2 M⊙ pulsars can constrain the parameter of oscillator harmonic κ1≈0.53 in the case the Coulomb term is excluded. If the Coulomb term is included, for the models with their parameters are consistent with SQM absolute stability condition, the 2.0 M⊙ constraint more prefers the maximum mass prediction of the model with the scalar Coulomb term than that of the model with the vector Coulomb term. On the contrary, the high densities EOS predicted by the model with the vector Coulomb is more compatible with the recent perturbative quantum chromodynamics result [1] than that predicted by the model with the scalar Coulomb. Furthermore, we also observed the quark composition in a very high density region depends quite sensitively on the kind of Coulomb term used.

  13. Time-dep endent Calculations for Two-proton Decay Width with Schematic Density-dependent Contact Pairing Interaction

    Institute of Scientific and Technical Information of China (English)

    Oishi Tomohiro

    2016-01-01

    We calculate the two-proton decay width of the 6 Be nucleus employing the schematic density-dependent contact potential for the proton-proton pairing interaction. The decay width is calculated with a time-dependent method, in which the two-proton emission is described as a time-evolution of a three-body meta-stable state. Model-dependence of the two-proton decay width has been shown by comparing the results obtained with the two different pairing models, schematic density-dependent contact and Minnesota interactions, which have zero and finite ranges, respectively.

  14. Surface density dependence of PCR amplicon hybridization on PNA/DNA probe layers

    DEFF Research Database (Denmark)

    Yao, Danfeng; Kim, Junyoung; Yu, Fang

    2005-01-01

    at an intermediate sodium concentration (approximately 100 mM). These effects were mainly ascribed to the electrostatic cross talk among the hybridized DNA molecules and the secondary structure of PCR amplicons. For the negatively charged DNA probes, the hybridization reaction was subjected additionally to the DNA...

  15. Behavioral signature of intraspecific competition and density dependence in colony-breeding marine predators.

    Science.gov (United States)

    Breed, Greg A; Don Bowen, W; Leonard, Marty L

    2013-10-01

    In populations of colony-breeding marine animals, foraging around colonies can lead to intraspecific competition. This competition affects individual foraging behavior and can cause density-dependent population growth. Where behavioral data are available, it may be possible to infer the mechanism of intraspecific competition. If these mechanics are understood, they can be used to predict the population-level functional response resulting from the competition. Using satellite relocation and dive data, we studied the use of space and foraging behavior of juvenile and adult gray seals (Halichoerus grypus) from a large (over 200,000) and growing population breeding at Sable Island, Nova Scotia (44.0 (o)N 60.0 (o)W). These data were first analyzed using a behaviorally switching state-space model to infer foraging areas followed by randomization analysis of foraging region overlap of competing age classes. Patterns of habitat use and behavioral time budgets indicate that young-of-year juveniles (YOY) were likely displaced from foraging areas near (less capable divers than adults and this limits the habitat available to them. However, other segregating mechanisms cannot be ruled out, and we discuss several alternate hypotheses. Mark-resight data indicate juveniles born between 1998 and 2002 have much reduced survivorship compared with cohorts born in the late 1980s, while adult survivorship has remained steady. Combined with behavioral observations, our data suggest YOY are losing an intraspecific competition between adults and juveniles, resulting in the currently observed decelerating logistic population growth. Competition theory predicts that intraspecific competition resulting in a clear losing competitor should cause compensatory population regulation. This functional response produces a smooth logistic growth curve as carrying capacity is approached, and is consistent with census data collected from this population over the past 50 years. The competitive mechanism

  16. Understanding spatial distributions : Negative density-dependence in prey causes predators to trade-off prey quantity with quality

    NARCIS (Netherlands)

    Bijleveld, Allert I; MacCurdy, Robert B; Chan, Ying-Chi; Penning, Emma; Gabrielson, Rich M; Cluderay, John; Spaulding, Eric L; Dekinga, Anne; Holthuijsen, Sander; ten Horn, Job; Brugge, Maarten; van Gils, Jan A; Winkler, David W; Piersma, Theunis

    2016-01-01

    Negative density-dependence is generally studied within a single trophic level, thereby neglecting its effect on higher trophic levels. The 'functional response' couples a predator's intake rate to prey density. Most widespread is a type II functional response, where intake rate increases asymptotic

  17. Understanding spatial distributions: negative density-dependence in prey causes predators to trade-off prey quantity with quality

    NARCIS (Netherlands)

    Bijleveld, A.I.; MacCurdy, R.B.; Chan, Y.-C; Penning, E.; Gabrielson, R.M.; Cluderay, J.; Spaulding, E.L.; Dekinga, A.; Holthuijsen, S.; Ten Horn, J.; Brugge, M.; van Gils, J.A.; Winkler, D.W.; Piersma, T.

    2016-01-01

    Negative density-dependence is generally studied within a single trophic level, thereby neglecting its effect on higher trophic levels. The ‘functional response’ couples a predator's intake rate to prey density. Most widespread is a type II functional response, where intake rate increases asymptotic

  18. Density dependence drives habitat production and survivorship of Acropora cervicornis used for restoration on a Caribbean coral reef

    Directory of Open Access Journals (Sweden)

    Mark C Ladd

    2016-12-01

    Full Text Available AbstractCoral restoration is gaining traction as a viable strategy to help restore degraded reefs. While the nascent field of coral restoration has rapidly progressed in the past decade, significant knowledge gaps remain regarding the drivers of restoration success that may impede our ability to effectively restore coral reef communities. Here, we conducted a field experiment to investigate the influence of coral density on the growth, habitat production, and survival of corals outplanted for restoration. We used nursery-raised colonies of Acropora cervicornis to experimentally establish populations of corals with either 3, 6, 12, or 24 corals within 4m2 plots, generating a gradient of coral densities ranging from 0.75 corals m-2 to 12 corals m-2. After 13 months we found that density had a significant effect on the growth, habitat production, and survivorship of restored corals. We found that coral survivorship increased as colony density decreased. Importantly, the signal of density dependent effects was context dependent. Our data suggest that positive density dependent effects influenced habitat production at densities of 3 corals m-2, but further increases in density resulted in negative density dependent effects with decreasing growth and survivorship of corals. These findings highlight the importance of density dependence for coral restoration planning and demonstrate the need to evaluate the influence of density for other coral species used for restoration. Further work focused on the mechanisms causing density dependence such as increased herbivory, rapid disease transmission, or altered predation rates are important next steps to advance our ability to effectively restore coral reefs.

  19. Atomistic simulation on charge mobility of amorphous tris(8-hydroxyquinoline) aluminum (Alq3): origin of Poole-Frenkel-type behavior.

    Science.gov (United States)

    Nagata, Yuki; Lennartz, Christian

    2008-07-21

    The atomistic simulation of charge transfer process for an amorphous Alq(3) system is reported. By employing electrostatic potential charges, we calculate site energies and find that the standard deviation of site energy distribution is about twice as large as predicted in previous research. The charge mobility is calculated via the Miller-Abrahams formalism and the master equation approach. We find that the wide site energy distribution governs Poole-Frenkel-type behavior of charge mobility against electric field, while the spatially correlated site energy is not a dominant mechanism of Poole-Frenkel behavior in the range from 2x10(5) to 1.4x10(6) V/cm. Also we reveal that randomly meshed connectivities are, in principle, required to account for the Poole-Frenkel mechanism. Charge carriers find a zigzag pathway at low electric field, while they find a straight pathway along electric field when a high electric field is applied. In the space-charge-limited current scheme, the charge-carrier density increases with electric field strength so that the nonlinear behavior of charge mobility is enhanced through the strong charge-carrier density dependence of charge mobility.

  20. Competing effects of nuclear deformation and density dependence of the Λ N interaction in BΛ values of hypernuclei

    Science.gov (United States)

    Isaka, M.; Yamamoto, Y.; Rijken, Th. A.

    2016-10-01

    Competitive effects of nuclear deformation and density dependence of Λ N interaction in Λ binding energies BΛ of hypernuclei are studied systematically on the basis of the baryon-baryon interaction model ESC (extended soft core) including many-body effects. By using the Λ N G -matrix interaction derived from ESC, we perform microscopic calculations of BΛ in Λ hypernuclei within the framework of the antisymmetrized molecular dynamics under the averaged-density approximation. The calculated values of BΛ reproduce experimental data within a few hundred keV in the wide mass regions from 9 to 51. It is found that competitive effects of nuclear deformation and density dependence of Λ N interaction work decisively for fine-tuning of BΛ values.

  1. Age-specific, density-dependent and environment-based mortality of a short-lived perennial herb

    OpenAIRE

    Picó, F Xavier; Retana, Javier

    2008-01-01

    Density-independent and density-dependent processes affect plant mortality. Although less well understood, age-specific mortality can also play an important role in plant mortality. The goal of this study was to analyse sev- eral factors accounting for mortality in the Mediterranean short-lived peren- nial herb Lobularia maritima. We followed three cohorts of plants (from emergence to death) during 4 years in field conditions. We collected data on plant mortality ...

  2. Global well-posedness for the incompressible MHD equations with density-dependent viscosity and resistivity coefficients

    Science.gov (United States)

    Si, Xin; Ye, Xia

    2016-10-01

    This paper concerns an initial-boundary value problem of the inhomogeneous incompressible MHD equations in a smooth bounded domain. The viscosity and resistivity coefficients are density-dependent. The global well-posedness of strong solutions is established, provided the initial norms of velocity and magnetic field are suitably small in some sense, or the lower bound of the transport coefficients are large enough. More importantly, there is not any smallness condition on the density and its gradient.

  3. Approximate particle number projection with density dependent forces Superdeformed bands in the A=150 and A=190 regions

    CERN Document Server

    Valor, A; Robledo, L M

    2000-01-01

    We derive the equations for approximate particle number projection based on mean field wave functions with finite range density dependent forces. As an application ground bands of even-A superdeformed nuclei in the A=150 and A=190 regions are calculated with the Gogny force. We discuss nuclear properties such as quadrupole moments, moments of inertia and quasiparticle spectra, among others, as a function of the angular momentum. We obtain a good overall description.

  4. Survival of diurnally sub periodic Wuchereria bancrofti in Downsiomyia nivea (Diptera: Culicidae: a density dependent factor from Andaman & Nicobar Islands

    Directory of Open Access Journals (Sweden)

    A N Shriram

    2014-01-01

    Full Text Available Background & objectives: In India, diurnally sub periodic Wuchereria bancrofti transmitted by Downsiomyia nivea is prevalent only in the Nicobar district of Andaman and Nicobar Islands. The ongoing LF elimination programme aims at transmission interruption by bringing down the microfilarie (mf load in the community, which has implication on the parasite load in mosquito vector. Therefore, understanding density dependent constraints on transmission assumes significance from control perspective. The present study was undertaken in Teressa Island to understand the density dependent parasite mortality and survival probability of the parasite Do. nivea. Methods: The entomological data collected from Teressa Island, endemic for the diurnally sub periodic form of W. bancrofti were used to examine the parasite loss and its survival up to infectivity. Patterns of parasite distribution in Do. nivea were examined. Results: Distribution patterns of microfilariae were found to be over dispersed in Do. nivea. The later stages of the parasite in the vector were randomly distributed. Distribution pattern of various filarial larval stages suggested that the loss of parasites occurred as development progressed and was maximal between the first and second stages. Further, both the prevalence of infection and the degree of parasite aggregation in the vector population have fallen significantly with development of parasite stage. Interpretation & conclusions: Results indicate the operation of parasite density dependent mortality of vectors or parasite loss or combination of both. The present study with Aedes transmitted filariasis conducted before launching LF elimination programme in the study area indicates a comparable level of parasite regulation in the vector which has similar implications on the transmission threshold. Thus, the consideration of Aedes with Culex in deriving the critical level of antigen positive for making decisions on cessation of mass drug

  5. Traveling wave solutions of density-dependent nonlinear reaction-diffusion equation via the extended generalized Riccati equation mapping method

    Science.gov (United States)

    Kengne, Emmanuel; Saydé, Michel; Ben Hamouda, Fathi; Lakhssassi, Ahmed

    2013-11-01

    Analytical entire traveling wave solutions to the 1+1 density-dependent nonlinear reaction-diffusion equation via the extended generalized Riccati equation mapping method are presented in this paper. This equation can be regarded as an extension case of the Fisher-Kolmogoroff equation, which is used for studying insect and animal dispersal with growth dynamics. The analytical solutions are then used to investigate the effect of equation parameters on the population distribution.

  6. Global strong solution to compressible Navier-Stokes equations with density dependent viscosity and temperature dependent heat conductivity

    Science.gov (United States)

    Duan, Ran; Guo, Ai; Zhu, Changjiang

    2017-04-01

    We obtain existence and uniqueness of global strong solution to one-dimensional compressible Navier-Stokes equations for ideal polytropic gas flow, with density dependent viscosity and temperature dependent heat conductivity under stress-free and thermally insulated boundary conditions. Here we assume viscosity coefficient μ (ρ) = 1 +ρα and heat conductivity coefficient κ (θ) =θβ for all α ∈ [ 0 , ∞) and β ∈ (0 , + ∞).

  7. High-resolution study of the Gamow-Teller strength distribution in the light nuclei {sup 9}B and {sup 13}N using the ({sup 3}He,t) charge-exchange reaction at 420 MeV beam energy

    Energy Technology Data Exchange (ETDEWEB)

    Scholl, Clemens

    2010-07-07

    Excited states in the light nuclei {sup 9}B and {sup 13}C were studied using the ({sup 3}He,t) charge-exchange reaction on {sup 9}Be and {sup 13}C targets. The measurements were performed at the research center for nuclear physics (RCNP) in Osaka, Japan, using the magnetic spectrometer Grand Raiden and the dispersive WS course. The {sup 3}He beam with an energy of 420 MeV was accelerated by the RCNP Ring Cyclotron. The Grand Raiden spectrometer and the WS course allow to study the ({sup 3}He,t) charge-exchange reaction with an energy resolution of around 30 keV, which is one order of magnitude better than measurements with the (p,n) charge-exchange reaction. The high resolution allows to better separate individual states and to determine weak excitation strengths because of low background in the spectra. A total of 19 states in {sup 13}N were studied, and a total of 20 states were observed in {sup 9}B. Of these, 9 states in {sup 13}C and 10 states in {sup 9}B were identified as being excited by a Gamow-Teller transition. Charge-exchange reactions are related to beta-decay, and at zero momentum transfer a simple proportionality exists between the cross-section of the charge-exchange experiment and the Fermi (F) or Gamow-Teller (GT) beta-decay strength. While the Fermi strength B(F) is concentrated in the transition to the isobaric analog state, the Gamow-Teller strength B(GT) is scattered among the excited states. The main aim of the present study is to determine the B(GT) strengths in the nuclei {sup 9}B and {sup 13}N. The only charge-exchange study of {sup 9}B was made 30 years ago with the (p,n) reaction and a resolution of around 300-400 keV. Many states, especially at high excitation energy, could not be resolved by that study. The present work was able to separate many weakly excited states with small decay width at high excitation energies (12-19 MeV) in {sup 9}B and determine the B(GT) strength distribution by using recent high-precision beta-decay data. The

  8. An evaluation of density-dependent and density-independent influences on population growth rates in Weddell seals

    Science.gov (United States)

    Rotella, J.J.; Link, W.A.; Nichols, J.D.; Hadley, G.L.; Garrott, R.A.; Proffitt, K.M.

    2009-01-01

    Much of the existing literature that evaluates the roles of density-dependent and density-independent factors on population dynamics has been called into question in recent years because measurement errors were not properly dealt with in analyses. Using state-space models to account for measurement errors, we evaluated a set of competing models for a 22-year time series of mark-resight estimates of abundance for a breeding population of female Weddell seals (Leptonychotes weddellii) studied in Erebus Bay, Antarctica. We tested for evidence of direct density dependence in growth rates and evaluated whether equilibrium population size was related to seasonal sea-ice extent and the Southern Oscillation Index (SOI). We found strong evidence of negative density dependence in annual growth rates for a population whose estimated size ranged from 438 to 623 females during the study. Based on Bayes factors, a density-dependence-only model was favored over models that also included en! vironmental covariates. According to the favored model, the population had a stationary distribution with a mean of 497 females (SD = 60.5), an expected growth rate of 1.10 (95% credible interval 1.08-1.15) when population size was 441 females, and a rate of 0.90 (95% credible interval 0.87-0.93) for a population of 553 females. A model including effects of SOI did receive some support and indicated a positive relationship between SOI and population size. However, effects of SOI were not large, and including the effect did not greatly reduce our estimate of process variation. We speculate that direct density dependence occurred because rates of adult survival, breeding, and temporary emigration were affected by limitations on per capita food resources and space for parturition and pup-rearing. To improve understanding of the relative roles of various demographic components and their associated vital rates to population growth rate, mark-recapture methods can be applied that incorporate both

  9. Density dependence of electron mobility in the accumulation mode for fully depleted SOI films

    Energy Technology Data Exchange (ETDEWEB)

    Naumova, O. V., E-mail: naumova@isp.nsc.ru; Zaitseva, E. G.; Fomin, B. I.; Ilnitsky, M. A.; Popov, V. P. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2015-10-15

    The electron mobility µ{sub eff} in the accumulation mode is investigated for undepleted and fully depleted double-gate n{sup +}–n–n{sup +} silicon-on-insulator (SOI) metal–oxide–semiconductor field-effect transistors (MOSFET). To determine the range of possible values of the mobility and the dominant scattering mechanisms in thin-film structures, it is proposed that the field dependence of the mobility µ{sub eff} be replaced with the dependence on the density N{sub e} of induced charge carriers. It is shown that the dependences µ{sub eff}(N{sub e}) can be approximated by the power functions µ{sub eff}(N{sub e}) ∝ N{sub e}{sup -n}, where the exponent n is determined by the chargecarrier scattering mechanism as in the mobility field dependence. The values of the exponent n in the dependences µ{sub eff}(N{sub e}) are determined when the SOI-film mode near one of its surfaces varies from inversion to accumulation. The obtained results are explained from the viewpoint of the electron-density redistribution over the SOI-film thickness and changes in the scattering mechanisms.

  10. Orbital-occupancy versus charge ordering and the strength of electron correlations in electron-doped CaMnO3.

    Science.gov (United States)

    Luo, Weidong; Franceschetti, Alberto; Varela, Maria; Tao, Jing; Pennycook, Stephen J; Pantelides, Sokrates T

    2007-07-20

    The structural, electronic, and magnetic properties of mixed-valence compounds are believed to be governed by strong electron correlations. Here we report benchmark density-functional calculations in the spin-polarized generalized-gradient approximation (GGA) for the ground-state properties of doped CaMnO(3). We find excellent agreement with all available data, while inclusion of strong correlations in the GGA+U scheme impairs this agreement. We demonstrate that formal oxidation states reflect only orbital occupancies, not charge transfer, and resolve outstanding controversies about charge ordering.

  11. Brief Discussion on the Electric field Strength of the Regular Charged Polygon Ring, Dish, Cylindrical Surface, and Cylinder%浅论正多边形带电环盘简柱的场强

    Institute of Scientific and Technical Information of China (English)

    万嵩林; 范双菲; 傅芸; 李秉钊; 滕保华

    2012-01-01

    Based on the superposition principle, the charge distribution on the axis of regular charged polygon ring,dish, cylindrical surface,and cylinder are calculated systematically. The results show that the algebraic property of electric field strength of different charged body is closely related to its charge distribution, i. e. , the ring's is better than the plane's, and the cylindrical surfaee's is superior to the cylinder's.%根据文献[3]提供的公式,基于场强叠加原理,系统解析计算了正多边形带电环、盘、筒、柱中轴线上的电场分布,结果表明不同带电体的电场强度的代数性质与其电荷分布密切相关.从所做的几项计算中显示,环优于盘,筒优于柱.

  12. The effects of density-dependent form factors for (e, e'p) reaction in quasi-elastic region

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.S. [Korea Aerospace University, School of Liberal Arts and Science, Goyang (Korea, Republic of); Cheoun, Myung-Ki [Soongsil University, Department of Physics, Seoul (Korea, Republic of); Kim, Hungchong [Kookmin University, Department of General Education, Seoul (Korea, Republic of); So, W.Y. [Kangwon National University at Dogye, Department of Radiological Science, Samcheok (Korea, Republic of)

    2016-04-15

    Within the framework of a relativistic single particle model, the effects of density-dependent electromagnetic form factors on the exclusive (e, e'p) reaction are investigated in the quasi-elastic region. The density-dependent electromagnetic form factors are generated from a quark-meson coupling model and used to calculate the cross sections in two different densities, either at the normal density of ρ{sub 0} ∝ 0.15 fm{sup -3} or at the lower density, 0.5ρ{sub 0}. Then these cross sections are analyzed in the two different kinematics: One is that the momentum of the outgoing nucleon is along the momentum transfer. The other is that the angle between the momentum of the outgoing nucleon and the momentum transfer is varied at fixed magnitude of the momentum of the outgoing nucleon. Our theoretical differential reduced cross sections are compared with the NIKHEF data for the {sup 208}Pb(e, e'p) reaction, which is related to the probability that a bound nucleon from a given orbit can be knocked-out of the nucleus. The effects of the density-dependent form factors increase the differential cross sections for both knocked-out proton and neutron by an amount of a few percent. Moreover they are shown to be almost the same within only a few percent, i.e., nearly independent of the shell location of knockout nucleons. These results are quite consistent with the characteristics of double magic nuclei which have relatively sharp smearing in the density distribution. (orig.)

  13. Effect of measurement error on tests of density dependence of catchability for walleyes in northern Wisconsin angling and spearing fisheries

    Science.gov (United States)

    Hansen, M.J.; Beard, T.D.; Hewett, S.W.

    2005-01-01

    We sought to determine how much measurement errors affected tests of density dependence of spearing and angling catchability for walleye Sander vitreus by quantifying relationships between spearing and angling catch rates (catch/h) and walleye population density (number/acre) in northern Wisconsin lakes. The mean measurement error of spearing catch rates was 43.5 times greater than the mean measurement error of adult walleye population densities, whereas the mean measurement error of angling catch rates was only 5.6 times greater than the mean measurement error of adult walleye population densities. The bias-corrected estimate of the relationship between spearing catch rate and adult walleye population density was similar to the ordinary-least-squares regression estimate but differed significantly from the geometric mean (GM) functional regression estimate. In contrast, the bias-corrected estimate of the relationship between angling catch rate and total walleye population density was intermediate between ordinary-least-squares and GM functional regression estimates. Catch rates of walleyes in both spearing and angling fisheries were not linearly related to walleye population density, which indicated that catch rates in both fisheries were hyperstable in relation to walleye population density. For both fisheries, GM functional regression overestimated the degree of hyperdepletion in catch rates and ordinary-least-squares regression overestimated the degree of hyperstability in catch rates. However, ordinary-least-squares regression induced significantly less bias in tests of density dependence than GM functional regression, so it may be suitable for testing the degree of density dependence in fisheries for which fish population density is estimated with mark-recapture methods similar to those used in our study. ?? Copyright by the American Fisheries Society 2005.

  14. The role of landscape features and density dependence in growth andfledging rates of Piping Plovers in North Dakota, USA

    Science.gov (United States)

    Anteau, Michael J.; Wiltermuth, Mark T.; Sherfy, Mark H.; Shaffer, Terry L.; Pearse, Aaron T.

    2014-01-01

    For species with precocial young, survival from hatching to fledging is a key factor influencing recruitment. Furthermore, growth rates of precocial chicks are an indicator of forage quality and habitat suitability of brood-rearing areas. We examined how growth and fledging rates of Piping Plover (Charadrius melodus) chicks were influenced by landscape features, such as hatchling density (hatchlings per hectare of remotely sensed habitat [H ha-1]), island vs. mainland, and wind fetch (exposure to waves) at 2-km segments (n ¼ 15) of Lake Sakakawea, North Dakota, during 2007–2008. Hatchling growth was comparable with published estimates for other habitats. Models for fledging rate (fledged young per segment) assuming density dependence had more support (wi ¼ 96%) than those assuming density independence (wi ¼ 4%). Density-dependent processes appeared to influence fledging rate only at densities .5 H ha-1, which occurred in 19% of the segments we sampled. When areas with densities .5 H ha-1 were excluded, density-dependence and density-independence models were equally supported (wi ¼ 52% and 48%, respectively). Fledging rate declined as the wind fetch of a segment increased. Fledging rate on mainland shorelines was 4.3 times greater than that on islands. Previous work has indicated that plovers prefer islands for nesting, but our results suggest that this preference is not optimal and could lead to an ecological trap for chicks. While other researchers have found nesting-habitat requirements to be gravelly areas on exposed beaches without fine-grain substrates, our results suggest that chicks fledge at lower rates in these habitats. Thus, breeding plovers likely require complexes of these nesting habitats along with protected areas with fine, nutrient-rich substrate for foraging by hatchlings.

  15. Carrier-Density-Dependent Electron Spin Relaxation in GaAs/AlGaAs Multi Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    SHOU Qian; WU Yu; LIU Lu-Ning; WEN Jin-Hui; LAI Tian-Shu; LIN Wei-Zhu

    2005-01-01

    @@ The carrier-density-dependent electron spin relaxation processes in GaAs/AlGaAs multi quantum wells are investigated by a femtosecond pump probe experiment. The spin relaxation time presents two distinguishable trends with the increasing excitation density. It increases from 60ps to 70ps with carrier densities from 1 × 1017 cm-3to 5 × 1017 cm-3 and gradually saturates up to ~80ps at 4 × 1018 cm-3. The experimental results are attributed to the combined competition between collision intensification and scattering potential screening and provide a good experimental confirmation for the theoretical D'yakonov-Perel' mechanism descriptions.

  16. Dispersal-mediated effect of microhabitat availability and density dependence determine population dynamics of a forest floor web spider.

    Science.gov (United States)

    Takada, Mayura B; Miyashita, Tadashi

    2014-09-01

    Landscapes in nature can be viewed as a continuum of small total habitable area with high fragmentation to widely spreading habitats. The dispersal-mediated rescue effect predominates in the former landscapes, while classical density-dependent processes generally prevail in widely spread habitats. A similar principle should be applied to populations of organisms utilizing microhabitats in limited supply. To test this hypothesis, we examined the population dynamics of a web spider, Neriene brongersmai, in 16 populations with varying degrees of microhabitat availability, and we explored whether: (i) high microhabitat availability improves survival rate during density-independent movement, while the resultant high density reduces survival rate in a density-dependent manner; and (ii) temporal population stability increases with microhabitat availability at the population level. Furthermore, we conducted two types of field experiments to verify whether high microhabitat availability actually reduces mortality associated with web-site movement. Field observations revealed that demographic change in N. brongersmai populations was affected by three factors at different stages, namely the microhabitat limitation from the early to late juvenile stages, the density dependence from the late juvenile to adult stages and the food limitation from the adult to the next early juvenile stages. In addition, there was a tendency for a positive association between population stability and microhabitat availability at the population level. A small-scale experiment, where the frequency of spider web relocation was equalized artificially, revealed that high microhabitat availability elevated the survival rate during a movement event between web-sites. The larger spatiotemporal scale experiment also revealed an improved spider survival rate following treatment with high microhabitat availability, even though spider density was kept at a relatively low level. The population dynamics of N

  17. Remarks on the use of projected densities in the density-dependent part of Skyrme or Gogny functionals

    Science.gov (United States)

    Robledo, L. M.

    2010-06-01

    I discuss the inadequacy of the 'projected density' prescription to be used in density-dependent forces/functionals when calculations beyond mean field are pursued. The case of calculations aimed at the symmetry restoration of mean fields obtained with effective realistic forces of the Skyrme or Gogny type is considered in detail. It is shown that, at least for the restoration of spatial symmetries like rotations, translations or parity, the above prescription yields catastrophic results for the energy that drive the intrinsic wave-function to configurations with infinite deformation, thereby preventing its use both in projection after and before variation.

  18. Remarks on the use of projected densities in the density dependent part of Skyrme or Gogny functionals

    CERN Document Server

    Robledo, L M

    2010-01-01

    I discuss the inadequacy of the "projected density" prescription to be used in density dependent forces/functionals when calculations beyond mean field are pursued. The case of calculations aimed at the symmetry restoration of mean fields obtained with effective realistic forces of the Skyrme or Gogny type is considered in detail. It is shown that at least for the restoration of spatial symmetries like rotations, translations or parity the above prescription yields catastrophic results for the energy that drive the intrinsic wave function to configurations with infinite deformation, preventing thereby its use both in projection after and before variation.

  19. Vacuum states on compressible Navier-Stokes equations with general density-dependent viscosity and general pressure law

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper,we study the one-dimensional motion of viscous gas with a general pres- sure law and a general density-dependent viscosity coefficient when the initial density connects to the vacuum state with a jump.We prove the global existence and the uniqueness of weak solutions to the compressible Navier-Stokes equations by using the line method.For this,some new a priori estimates are obtained to take care of the general viscosity coefficientμ(ρ)instead ofρ~θ.

  20. Vacuum states on compressible Navier-Stokes equations with general density-dependent viscosity and general pressure law

    Institute of Scientific and Technical Information of China (English)

    Mei-man SUN; Chang-jiang ZHU

    2007-01-01

    In this paper, we study the one-dimensional motion of viscous gas with a general pressure law and a general density-dependent viscosity coefficient when the initial density connects to the vacuum state with a jump. We prove the global existence and the uniqueness of weak solutions to the compressible Navier-Stokes equations by using the line method. For this, some new a priori estimates are obtained to take care of the general viscosity coefficient μ(ρ) instead of ρθ.

  1. Amplified spontaneous emission of phonons as a likely mechanism for density-dependent velocity saturation in GaN transistors

    Science.gov (United States)

    Khurgin, Jacob B.; Bajaj, Sanyam; Rajan, Siddharth

    2016-09-01

    We show that density-dependent velocity saturation in a GaN high electron mobility transistor (HEMT) can be related to the stimulated emission of longitudinal optical (LO) phonons. As the drift velocity of electrons increases, the drift of the Fermi distribution in reciprocal space results in population inversion and gain for the LO phonons. Once this gain reaches a threshold value, the avalanche-like increase in LO phonon emission causes a rapid loss of electron energy and momentum and leads to drift velocity saturation. Our simple model correctly predicts both the general trend of decreasing saturation velocity with increasing electron density, and the measured experimental values of saturation.

  2. Why continuum electrostatics theories cannot explain biological structure, polyelectrolytes or ionic strength effects in ion-protein interactions.

    Science.gov (United States)

    Collins, Kim D

    2012-06-01

    Continuum electrostatics models for ions in water provide apparent long range electrostatic explanations for the forces on ions. However the electro-chemical free energy of solvation of ions resides largely in the first two water layers, which control the interfacial behavior of the ions and require explicit modeling to capture their distinctive behaviors. The resulting short range forces produce such surprising charge density-dependent behaviors as ion adsorption onto nonpolar surfaces, like charge aggregation of ions, and substantial ion pairing preferences, which arise largely from the affinity of specific ions for individual water molecules. Specific ion effects controlled by the local water affinity of the ion show a diagnostic change of sign between strongly hydrated Na(+) and weakly hydrated K(+) and between strongly hydrated F(-) and weakly hydrated Cl(-), in both cases marking the strength of water-water interactions in bulk solution, a critical benchmark missing from continuum electrostatics models.

  3. Quantifying Correlations Between Isovector Observables and the Density Dependence of Nuclear Symmetry Energy away from Saturation Density

    CERN Document Server

    Fattoyev, F J; Li, Bao-An

    2014-01-01

    According to the Hugenholtz-Van Hove theorem, the nuclear symmetry energy $S(\\rho)$ and its slope $L(\\rho)$ at arbitrary densities can be decomposed in terms of the density and momentum dependence of the single-nucleon potentials in isospin-asymmetric nuclear matter which are potentially accessible to experiment. We quantify the correlations between several well-known isovector observables and $L(\\rho)$ to locate the density range in which each isovector observable is most sensitive to the density dependence of the $S(\\rho)$. We then study the correlation coefficients between those isovector observables and all the components of the $L(\\rho)$. The neutron skin thickness of $^{208}$Pb is found to be strongly correlated with the $L(\\rho)$ at a subsaturation density of $\\rho = 0.59 \\rho_0$ through the density dependence of the first-order symmetry potential. Neutron star radii are found to be strongly correlated with the $L(\\rho)$ over a wide range of supra-saturation densities mainly through both the density an...

  4. Predicting population survival under future climate change: density dependence, drought and extraction in an insular bighorn sheep.

    Science.gov (United States)

    Colchero, Fernando; Medellin, Rodrigo A; Clark, James S; Lee, Raymond; Katul, Gabriel G

    2009-05-01

    1. Our understanding of the interplay between density dependence, climatic perturbations, and conservation practices on the dynamics of small populations is still limited. This can result in uninformed strategies that put endangered populations at risk. Moreover, the data available for a large number of populations in such circumstances are sparse and mined with missing data. Under the current climate change scenarios, it is essential to develop appropriate inferential methods that can make use of such data sets. 2. We studied a population of desert bighorn sheep introduced to Tiburon Island, Mexico in 1975 and subjected to irregular extractions for the last 10 years. The unique attributes of this population are absence of predation and disease, thereby permitting us to explore the combined effect of density dependence, environmental variability and extraction in a 'controlled setting.' Using a combination of nonlinear discrete models with long-term field data, we constructed three basic Bayesian state space models with increasing density dependence (DD), and the same three models with the addition of summer drought effects. 3. We subsequently used Monte Carlo simulations to evaluate the combined effect of drought, DD, and increasing extractions on the probability of population survival under two climate change scenarios (based on the Intergovernmental Panel on Climate Change predictions): (i) increase in drought variability; and (ii) increase in mean drought severity. 4. The population grew from 16 individuals introduced in 1975 to close to 700 by 1993. Our results show that the population's growth was dominated by DD, with drought having a secondary but still relevant effect on its dynamics. 5. Our predictions suggest that under climate change scenario (i), extraction dominates the fate of the population, while for scenario (ii), an increase in mean drought affects the population's probability of survival in an equivalent magnitude as extractions. Thus, for the

  5. Loss of density-dependence and incomplete control by dominant breeders in a territorial species with density outbreaks

    Directory of Open Access Journals (Sweden)

    Ylönen Hannu

    2011-07-01

    Full Text Available Abstract Background A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression. Results We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density. Conclusions At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point, the dominance of breeders could not be sustained (incomplete control. In our experiment, this point

  6. Density dependent neurodynamics.

    Science.gov (United States)

    Halnes, Geir; Liljenström, Hans; Arhem, Peter

    2007-01-01

    The dynamics of a neural network depends on density parameters at (at least) two different levels: the subcellular density of ion channels in single neurons, and the density of cells and synapses at a network level. For the Frankenhaeuser-Huxley (FH) neural model, the density of sodium (Na) and potassium (K) channels determines the behaviour of a single neuron when exposed to an external stimulus. The features of the onset of single neuron oscillations vary qualitatively among different regions in the channel density plane. At a network level, the density of neurons is reflected in the global connectivity. We study the relation between the two density levels in a network of oscillatory FH neurons, by qualitatively distinguishing between three regions, where the mean network activity is (1) spiking, (2) oscillating with enveloped frequencies, and (3) bursting, respectively. We demonstrate that the global activity can be shifted between regions by changing either the density of ion channels at the subcellular level, or the connectivity at the network level, suggesting that different underlying mechanisms can explain similar global phenomena. Finally, we model a possible effect of anaesthesia by blocking specific inhibitory ion channels.

  7. Nonlinear coupling of acoustic and shear mode in a strongly coupled dusty plasma with a density dependent viscosity

    Science.gov (United States)

    Garai, S.; Janaki, M. S.; Chakrabarti, N.

    2016-09-01

    The nonlinear propagation of low frequency waves, in a collisionless, strongly coupled dusty plasma (SCDP) with a density dependent viscosity, has been studied with a proper Galilean invariant generalized hydrodynamic (GH) model. The well known reductive perturbation technique (RPT) has been employed in obtaining the solutions of the longitudinal and transverse perturbations. It has been found that the nonlinear propagation of the acoustic perturbations govern with the modified Korteweg-de Vries (KdV) equation and are decoupled from the sheared fluctuations. In the regions, where transversal gradients of the flow exists, coupling between the longitudinal and transverse perturbations occurs due to convective nonlinearity which is true for the homogeneous case also. The results, obtained here, can have relative significance to astrophysical context as well as in laboratory plasmas.

  8. 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.

  9. Size- and density-dependent elution of normal and pathological red blood cells by gravitational field-flow fractionation.

    Science.gov (United States)

    Cardot, P J; Elgéa, C; Guernet, M; Godet, D; Andreux, J P

    1994-04-01

    Elution of normal and pathological human red blood cells (RBCs) was performed by gravitational field-flow fractionation (GFFF). The reproducibility of the retention factor was lower than 10% and elution at high and low flow-rates confirmed the existence of "lifting forces". No direct correlation between size and retention was observed for normal RBCs in the absence of density information. Elution of pathological human RBCs, known to be modified in shape, density and rigidity, was performed. The elution parameters confirmed that the retention mechanism of RBCs is at least density dependent but that other factors can be involved, such as shape or deformity. Moreover, peak profile description parameters (standard deviation and asymmetry) can be qualitatively related to some biophysical parameters. Numerous elution characteristics can be linked to cell properties described in the literature and although GFFF appeared to have limited capabilities in terms of size analysis it appeared to be a versatile tool for studying cell biophysical characteristics.

  10. Density-dependent interference of aphids with caterpillar-induced defenses in Arabidopsis: involvement of phytohormones and transcription factors.

    Science.gov (United States)

    Kroes, Anneke; van Loon, Joop J A; Dicke, Marcel

    2015-01-01

    In nature, plants are exposed to attacks by multiple herbivore species at the same time. To cope with these attacks, plants regulate defenses with the production of hormones such as salicylic acid (SA) and jasmonic acid (JA). Because herbivore densities are dynamic in time, this may affect plant-mediated interactions between different herbivores attacking at the same time. In Arabidopsis thaliana, feeding by Brevicoryne brassicae aphids interferes with induced defenses against Plutella xylostella caterpillars. This is density dependent: at a low aphid density, the growth rate of P. xylostella was increased, whereas caterpillars feeding on plants colonized by aphids at a high density have a reduced growth rate. Growth of P. xylostella larvae was unaffected on sid2-1 or on dde2-2 mutant plants when feeding simultaneously with a low or high aphid density. This shows that aphid interference with caterpillar-induced defenses requires both SA and JA signal transduction pathways. Transcriptional analysis revealed that simultaneous feeding by caterpillars and aphids at a low density induced the expression of the SA transcription factor gene WRKY70 whereas expression of WRKY70 was lower in plants induced with both caterpillars and a high aphid density. Interestingly, the expression of the JA transcription factor gene MYC2 was significantly higher in plants simultaneously attacked by aphids at a high density and caterpillars. These results indicate that a lower expression level of WRKY70 leads to significantly higher MYC2 expression through SA-JA cross-talk. Thus, plant-mediated interactions between aphids and caterpillars are density dependent and involve phytohormonal cross-talk and differential activation of transcription factors.

  11. Cell density-dependent stimulation of PAI-1 and hyaluronan synthesis by TGF-β in orbital fibroblasts.

    Science.gov (United States)

    Galgoczi, Erika; Jeney, Florence; Gazdag, Annamaria; Erdei, Annamaria; Katko, Monika; Nagy, Domonkos M; Ujhelyi, Bernadett; Steiber, Zita; Gyory, Ferenc; Berta, Eszter; Nagy, Endre V

    2016-05-01

    During the course of Graves' orbitopathy (GO), orbital fibroblasts are exposed to factors that lead to proliferation and extracellular matrix (ECM) overproduction. Increased levels of tissue plasminogen activator inhibitor type 1 (PAI-1 (SERPINE1)) might promote the accumulation of ECM components. PAI-1 expression is regulated by cell density and various cytokines and growth factors including transforming growth factorβ(TGF-β). We examined the effects of increasing cell densities and TGF-β on orbital fibroblasts obtained from GO patients and controls. Responses were evaluated by the measurement of proliferation, PAI-1 expression, and ECM production. There was an inverse correlation between cell density and the per cell production of PAI-1. GO orbital, normal orbital, and dermal fibroblasts behaved similarly in this respect. Proliferation rate also declined with increasing cell densities. Hyaluronan (HA) production was constant throughout the cell densities tested in all cell lines. In both GO and normal orbital fibroblasts, but not in dermal fibroblasts, TGF-β stimulated PAI-1 production in a cell density-dependent manner, reaching up to a five-fold increase above baseline. This has been accompanied by increased HA secretion and pericellular HA levels at high cell densities. Increasing cell density is a negative regulator of proliferation and PAI-1 secretion both in normal and GO orbital fibroblasts; these negative regulatory effects are partially reversed in the presence of TGF-β. Cell density-dependent regulation of PAI-1 expression in the orbit, together with the local cytokine environment, may have a regulatory role in the turnover of the orbital ECM and may contribute to the expansion of orbital soft tissue in GO.

  12. Impact of numerical artifact of the forward model in the inverse solution of density-dependent flow problem

    Science.gov (United States)

    Nassar, Mohamed K.; Ginn, Timothy R.

    2014-08-01

    We investigate the effect of computational error on the inversion of a density-dependent flow and transport model, using SEAWAT and UCODE-2005 in an inverse identification of hydraulic conductivity and dispersivity using head and concentration data from a 2-D laboratory experiment. We investigated inversions using three different solution schemes including variation of number of particles and time step length, in terms of the three aspects: the shape and smoothness of the objective function surface, the consequent impacts to the optimization, and the resulting Pareto analyses. This study demonstrates that the inversion is very sensitive to the choice of the forward model solution scheme. In particular, standard finite difference methods provide the smoothest objective function surface; however, this is obtained at the cost of numerical artifacts that can lead to erroneous warping of the objective function surface. Total variation diminishing (TVD) schemes limit these impacts at the cost of more computation time, while the hybrid method of characteristics (HMOC) approach with increased particle numbers and/or reduced time step gives both smoothed and accurate objective function surface. Use of the most accurate methods (TVD and HMOC) did lead to successful inversion of the two parameters; however, with distinct results for Pareto analyses. These results illuminate the sensitivity of the inversion to a number of aspects of the forward solution of the density-driven flow problem and reveal that parameter values may result that are erroneous but that counteract numerical errors in the solution.

  13. Cell Density-Dependent Upregulation of PDCD4 in Keratinocytes and Its Implications for Epidermal Homeostasis and Repair

    Directory of Open Access Journals (Sweden)

    Tao Wang

    2015-12-01

    Full Text Available Programmed cell death 4 (PDCD4 is one multi-functional tumor suppressor inhibiting neoplastic transformation and tumor invasion. The role of PDCD4 in tumorigenesis has attracted more attention and has been systematically elucidated in cutaneous tumors. However, the normal biological function of PDCD4 in skin is still unclear. In this study, for the first time, we find that tumor suppressor PDCD4 is uniquely induced in a cell density-dependent manner in keratinocytes. To determine the potential role of PDCD4 in keratinocyte cell biology, we show that knockdown of PDCD4 by siRNAs can promote cell proliferation in lower cell density and partially impair contact inhibition in confluent HaCaT cells, indicating that PDCD4 serves as an important regulator of keratinocytes proliferation and contact inhibition in vitro. Further, knockdown of PDCD4 can induce upregulation of cyclin D1, one key regulator of the cell cycle. Furthermore, the expression patterns of PDCD4 in normal skin, different hair cycles and the process of wound healing are described in detail in vivo, which suggest a steady-state regulatory role of PDCD4 in epidermal homeostasis and wound healing. These findings provide a novel molecular mechanism for keratinocytes’ biology and indicate that PDCD4 plays a role in epidermal homeostasis.

  14. Linear-In-The-Parameters Oblique Least Squares (LOLS) Provides More Accurate Estimates of Density-Dependent Survival

    Science.gov (United States)

    Vieira, Vasco M. N. C. S.; Engelen, Aschwin H.; Huanel, Oscar R.; Guillemin, Marie-Laure

    2016-01-01

    Survival is a fundamental demographic component and the importance of its accurate estimation goes beyond the traditional estimation of life expectancy. The evolutionary stability of isomorphic biphasic life-cycles and the occurrence of its different ploidy phases at uneven abundances are hypothesized to be driven by differences in survival rates between haploids and diploids. We monitored Gracilaria chilensis, a commercially exploited red alga with an isomorphic biphasic life-cycle, having found density-dependent survival with competition and Allee effects. While estimating the linear-in-the-parameters survival function, all model I regression methods (i.e, vertical least squares) provided biased line-fits rendering them inappropriate for studies about ecology, evolution or population management. Hence, we developed an iterative two-step non-linear model II regression (i.e, oblique least squares), which provided improved line-fits and estimates of survival function parameters, while robust to the data aspects that usually turn the regression methods numerically unstable. PMID:27936048

  15. Nonlinear Asymptotic Stability of the Lane-Emden Solutions for the Viscous Gaseous Star Problem with Degenerate Density Dependent Viscosities

    Science.gov (United States)

    Luo, Tao; Xin, Zhouping; Zeng, Huihui

    2016-11-01

    The nonlinear asymptotic stability of Lane-Emden solutions is proved in this paper for spherically symmetric motions of viscous gaseous stars with the density dependent shear and bulk viscosities which vanish at the vacuum, when the adiabatic exponent {γ} lies in the stability regime {(4/3, 2)}, by establishing the global-in-time regularity uniformly up to the vacuum boundary for the vacuum free boundary problem of the compressible Navier-Stokes-Poisson systems with spherical symmetry, which ensures the global existence of strong solutions capturing the precise physical behavior that the sound speed is {C^{{1}/{2}}}-Hölder continuous across the vacuum boundary, the large time asymptotic uniform convergence of the evolving vacuum boundary, density and velocity to those of Lane-Emden solutions with detailed convergence rates, and the detailed large time behavior of solutions near the vacuum boundary. Those uniform convergence are of fundamental importance in the study of vacuum free boundary problems which are missing in the previous results for global weak solutions. Moreover, the results obtained in this paper apply to much broader cases of viscosities than those in Fang and Zhang (Arch Ration Mech Anal 191:195-243, 2009) for the theory of weak solutions when the adiabatic exponent {γ} lies in the most physically relevant range. Finally, this paper extends the previous local-in-time theory for strong solutions to a global-in-time one.

  16. Coulomb correlation effects and density dependence of radiative recombination rates in polar AlGaN quantum wells

    Science.gov (United States)

    Rupper, Greg; Rudin, Sergey; Bertazzi, Francesco; Garrett, Gregory; Wraback, Michael

    2013-03-01

    AlGaN narrow quantum wells are important elements of deep-ultraviolet light emitting devices. The electron-hole radiative recombination rates are important characteristics of these nanostructures. In this work we evaluated their dependence on carrier density and lattice temperature and compared our theoretical results with the experimentally determined radiative lifetimes in the c-plane grown AlGaN quantum wells. The bands were determined in the k .p approximation for a strained c-plane wurtzite quantum well and polarization fields were included in the model. In order to account for Coulomb correlations at relatively high densities of photo-excited electron-hole plasma and arbitrary temperature, we employed real-time Green's function formalism with self-energies evaluated in the self-consistent T-matrix approximation. The luminescence spectrum was obtained from the susceptibility by summing over scattering in-plane directions and polarization states. The recombination coefficient was obtained from the integrated photo-luminescence. The density dependence of the radiative recombination rate shows effects of strong screening of the polarization electric field at high photo-excitation density.

  17. Impact of the aspects of forward model solution schemes in the inverse solution of density dependent flow problem

    Science.gov (United States)

    Nassar, M.; Ginn, T.

    2012-12-01

    The purpose of this study is to investigate the effect of the computational error on the solution of the inverse problem connecting with density-dependent flow problem. This effect will be addressed by evaluating the uniqueness of the inverse via monitoring objective function surface behavior in two dimensions parameter space, hydraulic conductivity and longitudinal dispersivity. In addition, the Pareto surface will be generated to evaluate the trade-offs between two calibration objectives based on head and concentration measurement errors. This is conducted by changing the aspects of forward model solution scheme, Eulerian and Lagrangian methods with associated variables. The data used for this study is based on the lab study of Nassar et al (2008). The seepage tank is essentially 2D (in an x-z vertical plane) with relatively homogenous coarse sand media with assigned flux in the upstream and constant head or assigned flux boundary condition at the downstream. The forward model solution is conducted with SEAWAT and it is utilized jointly with the inverse code UCODE-2005. This study demonstrates that the choice of the different numerical scheme with associated aspects of the forward problem is a vital step in the solution of the inverse problem in indirect manner. The method of characteristics gives good results by increasing the initial particles numbers and/ or reducing the time step. The advantage of using more particles concept over decreasing the time step is in smoothing the objective function surface that enable the gradient based search technique works in efficient way. Also, the selected points on the Pareto surface is collapsed to two points on the objective function space. Most likely they are not collapsed to a single point in objective function space with one best parameter set because the problem is advection dominating problem.

  18. Density dependence of hydrogen bonding and the translational-orientational structural order in supercritical water: a molecular dynamics study.

    Science.gov (United States)

    Ma, Haibo; Ma, Jing

    2011-08-07

    Molecular dynamics simulation have been performed with a wide range of densities along a near critical isotherm of supercritical water (SCW) in order to study the density dependence of the structure order and hydrogen bonding (HB). It is revealed that the translational structure order is nearly invariant while the orientational tetrahedral structure order is very sensitive to the bulk density under supercritical conditions. Meanwhile, some energetically unfavorable intermediate water dimer structures are found to appear under supercritical conditions due to the reduced energy difference and the enhanced energy fluctuation. As a consequence, a general geometrical criterion or the inclusion of a energy-based criterion instead of currently widely adopted pure r(OH)-based geometric criterion is suggested to be used in the HB statistics under supercritical conditions. It is found that the average HB number per H(2)O molecule (n(HB)) reduces with the decreasing SCW bulk density although a given pair of H(2)O molecules are shown to have a stronger ability to form a hydrogen bond under lower SCW bulk densities. Accordingly, the orientational tetrahedral structure order q decreases with the reducing bulk density under supercritical conditions. However, when the fluid is dilute with ρ ≤ 0.19ρ(c) (ρ(c) = 0.322 g/cm(3)), the energy fluctuation increases sharply and the short-range order is destroyed, signifying the supercritical fluid (SCF)-gas state transition. Accordingly, the orientational tetrahedral structure order q gets reversal around ρ = 0.19ρ(c) and approaches zero under very dilute conditions. The sensitivity of the orientational order to the density implies the microscopic origin of the significant dependence of SCF's physicochemical properties on the pressure.

  19. Plant density-dependent variations in bioactive markers and root yield in Australian-grown Salvia miltiorrhiza Bunge.

    Science.gov (United States)

    Li, Chun Guang; Sheng, Shu Jun; Pang, Edwin C K; May, Brian; Xue, Charlie Chang Li

    2011-04-01

    The plant density-dependent variations in the root yield and content, and the yield of biomarkers in Australian grown Salvia miltiorrhiza Bunge, a commonly used Chinese medicinal herb for the treatment of cardiovascular diseases, were investigated in a field trial involving six different plant densities. The key biomarker compounds cryptotanshinone, tanshinone I, tanshinone IIA, and salvianolic acid B were quantified by a validated RP-HPLC method, and the root yields were determined per plant pair or unit area. There were significant variations (pplant densities. Positive linear correlations were observed between the contents of the three tanshinones, whereas negative linear correlations were revealed between the contents of the tanshinones and salvianolic acid B. The highest root yield per plant pair was achieved when the plants were grown at 45×30 cm or 45×40 cm, whereas the highest root production par unit area was obtained for a plant density of 30×30 cm. The highest contents of the three tanshinones and the most abundant production of these tanshinones per unit area were achieved when the plants were grown at 30×30 cm. However, the highest content of salvianolic acid B was found for a density of 45×40 cm, while its highest yield per unit area was obtained for densities of 30×40 cm or 45×30 cm. The findings suggest that the plant density distinctly affects the root yield and content and the yield of tanshinones and salvianolic acid B in Australian grown S. miltiorrhiza, which may be used as a guide for developing optimal agricultural procedures for cultivating this herb.

  20. Diet and density dependent competition affect larval performance and oviposition site selection in the mosquito species Aedes albopictus (Diptera: Culicidae

    Directory of Open Access Journals (Sweden)

    Yoshioka Miho

    2012-10-01

    Full Text Available Abstract Background Oviposition-site choice is an essential component of the life history of all mosquito species. According to the oviposition-preference offspring-performance (P-P hypothesis, if optimizing offspring performance and fitness ensures high overall reproductive fitness for a given species, the female should accurately assess details of the heterogeneous environment and lay her eggs preferentially in sites with conditions more suitable to offspring. Methods We empirically tested the P-P hypothesis using the mosquito species Aedes albopictus by artificially manipulating two habitat conditions: diet (measured as mg of food added to a container and conspecific density (CD; number of pre-existing larvae of the same species. Immature development (larval mortality, development time to pupation and time to emergence and fitness (measured as wing length were monitored from first instar through adult emergence using a factorial experimental design over two ascending gradients of diet (2.0, 3.6, 7.2 and 20 mg food/300 ml water and CD (0, 20, 40 and 80 larvae/300 ml water. Treatments that exerted the most contrasting values of larval performance were recreated in a second experiment consisting of single-female oviposition site selection assay. Results Development time decreased as food concentration increased, except from 7.2 mg to 20.0 mg (Two-Way CR ANOVA Post-Hoc test, P > 0.1. Development time decreased also as conspecific density increased from zero to 80 larvae (Two-Way CR ANOVA Post-Hoc test, P . Combined, these results support the role of density-dependent competition for resources as a limiting factor for mosquito larval performance. Oviposition assays indicated that female mosquitoes select for larval habitats with conspecifics and that larval density was more important than diet in driving selection for oviposition sites. Conclusions This study supports predictions of the P-P hypothesis and provides a mechanistic understanding

  1. A Peak in Density Dependence of Electron Spin Relaxation Time in n-Type Bulk GaAs in the Metallic Regime

    Institute of Scientific and Technical Information of China (English)

    SHEN Ka

    2009-01-01

    We demonstrate that the peak in the density dependence of electron spin relaxation time in n-type bulk GaAs in the metallic regime predicted by Jiang and Wu[Phys.Rev.B 79 (2009) 125206]has been realized experimentally in the latest work[arXiv:0902.0270]by Krauβ et al.

  2. Influence of chemical bond length changes on the crystal field strength and “ligand metal” charge transfer transitions in Cs2GeF6 doped with Mn4+ and Os4+ ions

    Science.gov (United States)

    Brik, M. G.

    2007-07-01

    Detailed study of dependence of the crystal field strength 10Dq and lowest charge transfer (CT) energies for different interionic distances in Cs2GeF6:Mn4+ and Cs2GeF6:Os4+crystals is presented. The calculations were performed using the first-principles discrete-variational Dirac Slater (DV-DS) method. As a result, the functional dependencies of 10Dq and lowest CT energy on the metal ligand distance R were obtained without any fitting or semiempirical parameters. It was shown that 10Dq depends on R as 1/Rn, with n=4.0612 and 4.3874 for Cs2GeF6:Mn4+ and Cs2GeF6:Os4+, respectively. Two approximations (linear and quadratic) are obtained for the dependence of the lowest CT energy on R; CT energy decreases when R increases with dE(CT)/dR=-638 and -1080 cm-1/pm for Cs2GeF6:Mn4+ and Cs2GeF6:Os4+, respectively, if the linear approximation is used. These values can be used for estimations of the lowest CT energies for Mn4+ and Os4+ ions in other hosts with fluorine ligands. Estimations of the electron-vibrational interaction (EVI) constants, Huang Rhys parameters, and Stokes shifts for all the above-mentioned crystals were performed using the obtained 10Dq and E(CT) functions.

  3. Resonance strengths in the {sup 17,18}O(p, α){sup 14,15}N reactions and background suppression underground. Commissioning of a new setup for charged-particle detection at LUNA

    Energy Technology Data Exchange (ETDEWEB)

    Bruno, C.G.; Scott, D.A.; Aliotta, M.; Davinson, T.; Griffin, C.J. [University of Edinburgh, SUPA, School of Physics and Astronomy, Edinburgh (United Kingdom); Formicola, A.; Best, A.; Junker, M. [Laboratori Nazionali del Gran Sasso, INFN, Assergi (Italy); Anders, M.; Bemmerer, D.; Szuecs, T. [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden (Germany); Broggini, C.; Menegazzo, R. [INFN, Padova (Italy); Caciolli, A.; Depalo, R. [INFN, Padova (Italy); Universita di Padova, Dipartimento di Fisica e Astronomia, Padova (Italy); Cavanna, F.; Corvisiero, P.; Prati, P. [INFN, Genova (Italy); Dipartimento di Fisica, Universita di Genova, Genova (Italy); Di Leva, A.; Imbriani, G. [Universita di Napoli ' ' Federico II' ' , Dipartimento di Scienze Fisiche, Napoli (Italy); Elekes, Z.; Fueloep, Zs.; Gyuerky, Gy.; Somorjai, E. [MTA Atomki, Institute of Nuclear Research, Debrecen (Hungary); Gervino, G. [Universita degli Studi di Torino, Dipartimento di Fisica Sperimentale, Torino (Italy); Guglielmetti, A.; Trezzi, D. [Universita degli Studi di Milano (Italy); INFN, Milano (Italy); Gustavino, C. [INFN, Roma (Italy); Napolitani, E. [Universita di Padova, Dipartimento di Fisica e Astronomia, Padova (Italy); Straniero, O. [Laboratori Nazionali del Gran Sasso, INFN, Assergi (Italy); Osservatorio Astronomico di Collurania, Teramo (Italy); Strieder, F. [South Dakota School of Mines and Technology, Rapid City, SD (United States); Collaboration: LUNA Collaboration

    2015-08-15

    We report on measurements of resonance strengths and energies for the E{sub p} = 151 and 193 keV resonances in the {sup 18}O(p, α){sup 15}N and {sup 17}O(p, α){sup 14}N reactions, respectively, obtained during commissioning of a new setup for alpha-particle detection studies at the LUNA underground laboratory. Our values, ωγ(151) = 164.2 ± 0.9{sub stat-11.7}{sup +12.1}{sub syst} meV and ωγ (193) = 1.68 ± 0.03{sub stat} ± 0.12{sub syst} meV, are in excellent agreement with those reported in the literature. New values of resonance energies are E{sub p} = 151.2 ± 0.3 keV and E{sub p} = 194.8 ± 0.3 keV, respectively, this latter with the highest precision to date. Comparative background measurements in silicon detectors overground and underground were also carried out, yielding up to a factor of 15 in background suppression at LUNA at energies around 200 keV. This clearly demonstrates the usefulness of underground measurements in charged-particles experiments, especially at low detection energies. (orig.)

  4. Density Dependence of the Mass and Decay Constant of Pion in Nuclear Matter in the Dyson-Schwinger Equation Approach of QCD

    Institute of Scientific and Technical Information of China (English)

    LIU Yu-Xin; CHAO Jing-Yi; CHANG Lei; YUAN Wei

    2005-01-01

    @@ With the Dyson-Schwinger equation formalism at finite chemical potential, we study the density dependence of the mass and decay constant of pion in nuclear matter. The calculated results indicate that both the mass and the decay constant remain almost constant at small chemical potential. As the chemical potential gets quite large, the decay constant increases and the mass decreases with the increasing of the chemical potential, and both of them vanish suddenly as a critical value is reached.

  5. You can't run but you can hide: refuge use in frog tadpoles elicits density-dependent predation by dragonfly larvae.

    Science.gov (United States)

    Hossie, Thomas John; Murray, Dennis L

    2010-06-01

    The potential role of prey refuges in stabilizing predator-prey interactions is of longstanding interest to ecologists, but mechanisms underlying a sigmoidal predator functional response remain to be fully elucidated. Authors have disagreed on whether the stabilizing effect of prey refuges is driven by prey- versus predator-centric mechanisms, but to date few studies have married predator and prey behavioural observations to distinguish between these possibilities. We used a dragonfly nymph-tadpole system to study the effect of a structural refuge (leaf litter) on the predator's functional response, and paired this with behavioural observations of both predator and prey. Our study confirmed that hyperbolic (type II) functional responses were characteristic of foraging predators when structural cover was low or absent, whereas the functional response was sigmoidal (type III) when prey were provided with sufficient refuge. Prey activity and refuge use were density independent across cover treatments, thereby eliminating a prey-centric mechanism as being the genesis for density-dependent predation. In contrast, the predator's pursuit length, capture success, and handling time were altered by the amount of structure implying that observed shifts in density-dependent predation likely were related to predator hunting efficiency. Our study advances current theory by revealing that despite fixed-proportion refuge use by prey, presence of a prey refuge can induce density-dependent predation through its effect on predator hunting strategy. Ultimately, responses of predator foraging decisions in response to changes in prey availability and search efficiency may be more important in producing density-dependent predation than the form of prey refuge use.

  6. Stability and Hopf Bifurcation of a Delayed Density-Dependent Predator-Prey System with Beddington-DeAngelis Functional Response

    Science.gov (United States)

    Li, Haiyin; Meng, Gang; She, Zhikun

    In this paper, we investigate the stability and Hopf bifurcation of a delayed density-dependent predator-prey system with Beddington-DeAngelis functional response, where not only the prey density dependence but also the predator density dependence are considered such that the studied predator-prey system conforms to the realistically biological environment. We start with the geometric criterion introduced by Beretta and Kuang [2002] and then investigate the stability of the positive equilibrium and the stability switches of the system with respect to the delay parameter τ. Especially, we generalize the geometric criterion in [Beretta & Kuang, 2002] by introducing the condition (i‧) which can be assured by the condition (H2‧), and adopting the technique of lifting to define the function S˜n(τ) for alternatively determining stability switches at the zeroes of S˜n(τ)s. Afterwards, by the Poincaré normal form for Hopf bifurcation in [Kuznetsov, 1998] and the bifurcation formulae in [Hassard et al., 1981], we qualitatively analyze the properties for the occurring Hopf bifurcations of the system (3). Finally, an example with numerical simulations is given to illustrate the obtained results.

  7. Perturbatively charged holographic disorder

    CERN Document Server

    O'Keeffe, Daniel K

    2015-01-01

    Within the framework of holography applied to condensed matter physics, we study a model of perturbatively charged disorder in D=4 dimensions. Starting from initially uncharged AdS_4, a randomly fluctuating boundary chemical potential is introduced by turning on a bulk gauge field parameterized by a disorder strength and a characteristic scale k_0. Accounting for gravitational backreaction, we construct an asymptotically AdS solution perturbatively in the disorder strength. The disorder averaged geometry displays unphysical divergences in the deep interior. We explain how to remove these divergences and arrive at a well behaved solution. The disorder averaged DC conductivity is calculated and is found to contain a correction to the AdS result. The correction appears at second order in the disorder strength and scales inversely with k_0. We discuss the extension to a system with a finite initial charge density. The disorder averaged DC conductivity may be calculated by adopting a technique developed for hologr...

  8. Strength Training

    Science.gov (United States)

    ... en español Entrenamiento de la fuerza muscular Strength training is a vital part of a balanced exercise routine that includes aerobic activity and flexibility exercises. Regular aerobic exercise, such as running or ...

  9. Strength Training

    Science.gov (United States)

    ... strengthens your heart and lungs. When you strength train with weights, you're using your muscles to ... see there are lots of different ways to train with weights. Try a few good basic routines ...

  10. Density dependence of the entropy and the solvation shell structure in supercritical water via molecular dynamics simulation.

    Science.gov (United States)

    Ma, Haibo

    2012-06-07

    We perform molecular dynamics simulations of supercritical water (SCW) with a wide range of densities along a near critical isotherm using the simple point charge extended (SPC/E) pair potential in order to study the entropy and the solvation shell structure around a central water molecule. It is shown that both the translational and orientational two-particle correlation entropy terms can serve as the metrics of the translational-orientational structural orders in water and it is revealed that the translational structural order is very sensitive to the density variation in the gas-like and liquid-like region, while the orientational structural order is much more dependent upon compression in the medium-density SCW region. The comparison of the magnitudes of the full thermodynamic excess entropy and two-particle correlation entropy confirms the recent findings that the many-body terms other than two-body ones also present significant and non-neglectable contributions to the full excess entropy for the highly anomalous fluids like water. The analysis of entropy terms as a function of intermolecular distance and the orientational distribution functions as well as the three-dimensional spatial distribution functions indicate that the structural order occurs only in a much more diffused first solvation shell due to the elongated hydrogen bonds under supercritical conditions. It is revealed that no obvious second or higher neighbor shells occur in SCW, in contrast with the feature of normal liquid water that the anomalous decrease of translational order upon compression occurs mainly in the second shell.

  11. Dry Dog Food Integrity and Mite Strain Influence the Density-Dependent Growth of the Stored-Product Mite Tyrophagus putrescentiae (Acari: Acaridida).

    Science.gov (United States)

    Rybanska, Dagmar; Hubert, Jan; Markovic, Martin; Erban, Tomas

    2016-02-01

    The infestation of foodstuffs by mites is connected to health risks and economic losses. The cosmopolitan stored-product mite Tyrophagus putrescentiae (Schrank, 1781) is an emerging and predominant pest of dry dog food. In this study, the influences on mite population growth of 1) the different dry dog food kernels present in the package; 2) the integrity of the dry dog food kernel, whether intact or crushed; 3) the initial population density of 10 or 100 specimens; and 4) the four mite strains used were investigated under laboratory conditions. The population growth tests were performed for 28 d at 85% relative humidity and 25°C. The intrinsic growth rates of the mites were compared. The population growth was higher on the brown and green kernels than on the red and white kernels. The kernel integrity affected the population growth, and the integrity effect was highly influenced by the initial mite population density. The mites showed density-dependent growth in three of the four mite strains tested. The initial population density changed the population growth ranking among the mite strains, thereby indicating strain-specific density-dependent growth. The results of this study have important implications for predictive models of stored-product mite populations in dry dog food. One practical recommendation is that the growth of mites should be considered with regard to the mite strains and according to the strain-specific density dependent growth. Next, the integrity of the kernels should be maintained because disrupted or crushed kernels promote increases in mite populations.

  12. Density-dependence in space and time: opposite synchronous variations in population distribution and body condition in the Baltic Sea sprat (Sprattus sprattus over three decades.

    Directory of Open Access Journals (Sweden)

    Michele Casini

    Full Text Available Spatio-temporal density-dependent processes are crucial regulatory factors for natural populations. However, there is a lack of studies addressing spatial density-dependence in fish growth. A previous investigation has suggested spatio-temporal density-dependence in body condition of Baltic sprat. Here, we used different techniques, such as centre of gravity, distance, and homogeneity indices, to better characterize the spatial and temporal variations in sprat density and body condition in the Baltic Proper. Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition. In the 1980s-early 1990s both centres were located in the middle of the Baltic Proper. From the mid 1990s the centres progressively separated in space, as the sprat population moved towards the north-eastern Baltic Proper, and the centre of maximum condition towards the south-western areas. Moreover, at low abundances, sprat density and condition were homogeneously distributed in space, whereas at high abundances both density and condition showed pronounced geographical gradients. The ecological processes potentially explaining the observed patterns were discussed in the light of the Ideal Free Distribution theory. We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years. The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

  13. Density-dependence in space and time: opposite synchronous variations in population distribution and body condition in the Baltic Sea sprat (Sprattus sprattus) over three decades.

    Science.gov (United States)

    Casini, Michele; Rouyer, Tristan; Bartolino, Valerio; Larson, Niklas; Grygiel, Włodzimierz

    2014-01-01

    Spatio-temporal density-dependent processes are crucial regulatory factors for natural populations. However, there is a lack of studies addressing spatial density-dependence in fish growth. A previous investigation has suggested spatio-temporal density-dependence in body condition of Baltic sprat. Here, we used different techniques, such as centre of gravity, distance, and homogeneity indices, to better characterize the spatial and temporal variations in sprat density and body condition in the Baltic Proper. Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition. In the 1980s-early 1990s both centres were located in the middle of the Baltic Proper. From the mid 1990s the centres progressively separated in space, as the sprat population moved towards the north-eastern Baltic Proper, and the centre of maximum condition towards the south-western areas. Moreover, at low abundances, sprat density and condition were homogeneously distributed in space, whereas at high abundances both density and condition showed pronounced geographical gradients. The ecological processes potentially explaining the observed patterns were discussed in the light of the Ideal Free Distribution theory. We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years. The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

  14. The potential impact of density dependent fecundity on the use of the faecal egg count reduction test for detecting drug resistance in human hookworms.

    Directory of Open Access Journals (Sweden)

    Andrew C Kotze

    Full Text Available Current efforts to control human soil-transmitted helminth (STH infections involve the periodic mass treatment of people, particularly children, in all endemic areas, using benzimidazole and imidothiazole drugs. Given the fact that high levels of resistance have developed to these same drugs in roundworms of livestock, there is a need to monitor drug efficacy in human STHs. The faecal egg count reduction test (FECRT, in which faecal egg output is measured pre- and post-drug treatment, is presently under examination by WHO as a means of detecting the emergence of resistance. We have examined the potential impact of density dependent fecundity on FECRT data. Recent evidence with the canine hookworm indicates that the density dependent egg production phenomenon shows dynamic properties in response to drug treatment. This will impact on measurements of drug efficacy, and hence drug resistance. It is likely that the female worms that survive a FECRT drug treatment in some human cases will respond to the relaxation of density dependent constraints on egg production by increasing their egg output significantly compared to their pre-treatment levels. These cases will therefore underestimate drug efficacy in the FECRT. The degree of underestimation will depend on the ability of the worms within particular hosts to increase their egg output, which will in turn depend on the extent to which their egg output is constrained prior to the drug treatment. As worms within different human cases will likely be present at quite different densities prior to a proposed FECRT, there is potential for the effects of this phenomenon on drug efficacy measurements to vary considerably within any group of potential FECRT candidates. Measurement of relative drug efficacy may be improved by attempting to ensure a consistent degree of underestimation in groups of people involved in separate FECRTs. This may be partly achieved by omission of cases with the heaviest infections

  15. COMPRESSIBLE NAVIER-STOKES EQUATIONS WITH DENSITY-DEPENDENT VISCOSITY,VACUUM AND GRAVITATIONAL FORCE IN THE CASE OF GENERAL PRESSURE

    Institute of Scientific and Technical Information of China (English)

    Yao Lei; Wang Wenjun

    2008-01-01

    This is a continuation of the article (Comm. Partial Differential Equations 26 (2001) 965). In this article, the authors consider the one-dimensional compressible isentropic Navier-Stokes equations with gravitational force, fixed boundary condition, a general pressure and the density-dependent viscosity coefficient when the viscous gas con-nects to vacuum state with a jump in density. Precisely, the viscosity coefficient u is proportional to pθ and 0 < θ < 1/2, where p is the density, and the pressure P =P(p) is a general pressure. The global existence and the uniqueness of weak solution are proved.

  16. Space Charge Modulated Electrical Breakdown

    Science.gov (United States)

    Li, Shengtao; Zhu, Yuanwei; Min, Daomin; Chen, George

    2016-09-01

    Electrical breakdown is one of the most important physical phenomena in electrical and electronic engineering. Since the early 20th century, many theories and models of electrical breakdown have been proposed, but the origin of one key issue, that the explanation for dc breakdown strength being twice or higher than ac breakdown strength in insulating materials, remains unclear. Here, by employing a bipolar charge transport model, we investigate the space charge dynamics in both dc and ac breakdown processes. We demonstrate the differences in charge accumulations under both dc and ac stresses and estimate the breakdown strength, which is modulated by the electric field distortion induced by space charge. It is concluded that dc breakdown initializes in the bulk whereas ac breakdown initializes in the vicinity of the sample-electrode interface. Compared with dc breakdown, the lower breakdown strength under ac stress and the decreasing breakdown strength with an increase in applied frequency, are both attributed to the electric field distortion induced by space charges located in the vicinity of the electrodes.

  17. 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.

  18. Density-dependent benefits in ant-hemipteran mutualism? The case of the ghost ant Tapinoma melanocephalum (Hymenoptera: Formicidae) and the invasive mealybug Phenacoccus solenopsis (Hemiptera: Pseudococcidae).

    Science.gov (United States)

    Zhou, Aiming; Kuang, Beiqing; Gao, Yingrui; Liang, Guangwen

    2015-01-01

    Although density-dependent benefits to hemipterans from ant tending have been measured many times, few studies have focused on integrated effects such as interactions between ant tending, natural enemy density, and hemipteran density. In this study, we tested whether the invasive mealybug Phenacoccus solenopsis is affected by tending by ghost ants (Tapinoma melanocephalum), the presence of parasitoids, mealybug density, parasitoid density and interactions among these factors. Our results showed that mealybug colony growth rate and percentage parasitism were significantly affected by ant tending, parasitoid presence, and initial mealybug density separately. However, there were no interactions among the independent factors. There were also no significant interactions between ant tending and parasitoid density on either mealybug colony growth rate or percentage parasitism. Mealybug colony growth rate showed a negative linear relationship with initial mealybug density but a positive linear relationship with the level of ant tending. These results suggest that benefits to mealybugs are density-independent and are affected by ant tending level.

  19. Non-coalescence of oppositely charged drops

    CERN Document Server

    Ristenpart, W D; Belmonte, A; Dollar, F; Stone, H A

    2009-01-01

    Oppositely charged drops have long been assumed to experience an attractive force that favors their coalescence. In this fluid dynamics video we demonstrate the existence of a critical field strength above which oppositely charged drops do not coalesce. We observe that appropriately positioned and oppositely charged drops migrate towards one another in an applied electric field; but whereas the drops coalesce as expected at low field strengths, they are repelled from one another after contact at higher field strengths. Qualitatively, the drops appear to `bounce' off one another. We directly image the transient formation of a meniscus bridge between the bouncing drops.

  20. CHARGE syndrome

    Directory of Open Access Journals (Sweden)

    Prasad Chitra

    2006-09-01

    Full Text Available Abstract CHARGE syndrome was initially defined as a non-random association of anomalies (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies/deafness. In 1998, an expert group defined the major (the classical 4C's: Choanal atresia, Coloboma, Characteristic ears and Cranial nerve anomalies and minor criteria of CHARGE syndrome. Individuals with all four major characteristics or three major and three minor characteristics are highly likely to have CHARGE syndrome. However, there have been individuals genetically identified with CHARGE syndrome without the classical choanal atresia and coloboma. The reported incidence of CHARGE syndrome ranges from 0.1–1.2/10,000 and depends on professional recognition. Coloboma mainly affects the retina. Major and minor congenital heart defects (the commonest cyanotic heart defect is tetralogy of Fallot occur in 75–80% of patients. Choanal atresia may be membranous or bony; bilateral or unilateral. Mental retardation is variable with intelligence quotients (IQ ranging from normal to profound retardation. Under-development of the external genitalia is a common finding in males but it is less apparent in females. Ear abnormalities include a classical finding of unusually shaped ears and hearing loss (conductive and/or nerve deafness that ranges from mild to severe deafness. Multiple cranial nerve dysfunctions are common. A behavioral phenotype for CHARGE syndrome is emerging. Mutations in the CHD7 gene (member of the chromodomain helicase DNA protein family are detected in over 75% of patients with CHARGE syndrome. Children with CHARGE syndrome require intensive medical management as well as numerous surgical interventions. They also need multidisciplinary follow up. Some of the hidden issues of CHARGE syndrome are often forgotten, one being the feeding adaptation of these children, which needs an early aggressive approach from a feeding team. As the child

  1. Assessment and validation of a suite of reverse transcription-quantitative PCR reference genes for analyses of density-dependent behavioural plasticity in the Australian plague locust

    Directory of Open Access Journals (Sweden)

    Blondin Laurence

    2011-02-01

    Full Text Available Abstract Background The Australian plague locust, Chortoicetes terminifera, is among the most promising species to unravel the suites of genes underling the density-dependent shift from shy and cryptic solitarious behaviour to the highly active and aggregating gregarious behaviour that is characteristic of locusts. This is because it lacks many of the major phenotypic changes in colour and morphology that accompany phase change in other locust species. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR is the most sensitive method available for determining changes in gene expression. However, to accurately monitor the expression of target genes, it is essential to select an appropriate normalization strategy to control for non-specific variation between samples. Here we identify eight potential reference genes and examine their expression stability at different rearing density treatments in neural tissue of the Australian plague locust. Results Taking advantage of the new orthologous DNA sequences available in locusts, we developed primers for genes encoding 18SrRNA, ribosomal protein L32 (RpL32, armadillo (Arm, actin 5C (Actin, succinate dehydrogenase (SDHa, glyceraldehyde-3P-dehydrogenase (GAPDH, elongation factor 1 alpha (EF1a and annexin IX (AnnIX. The relative transcription levels of these eight genes were then analyzed in three treatment groups differing in rearing density (isolated, short- and long-term crowded, each made up of five pools of four neural tissue samples from 5th instar nymphs. SDHa and GAPDH, which are both involved in metabolic pathways, were identified as the least stable in expression levels, challenging their usefulness in normalization. Based on calculations performed with the geNorm and NormFinder programs, the best combination of two genes for normalization of gene expression data following crowding in the Australian plague locust was EF1a and Arm. We applied their use to studying a target gene

  2. Patterns and causes of demographic variation in a harvested moose population: evidence for the effects of climate and density-dependent drivers.

    Science.gov (United States)

    Brown, Glen S

    2011-11-01

    1. Better understanding of the mechanisms affecting demographic variation in ungulate populations is needed to support sustainable management of harvested populations. While studies of moose Alces alces L. populations have previously explored temporal variation in demographic processes, managers responsible for populations that span large heterogeneous landscapes would benefit from an understanding of how demography varies across biogeographical gradients in climate and other population drivers. Evidence of thresholds in population response to manageable and un-manageable drivers could aid resource managers in identifying limits to the magnitude of sustainable change. 2. Generalized additive models (GAMs) were used to evaluate the relative importance of population density, habitat abundance, summer and winter climatic conditions, primary production, and harvest intensity in explaining spatial variation in moose vital rates in Ontario, Canada. Tree regression was used to test for thresholds in the magnitudes of environmental predictor variables that significantly affected population vital rates. 3. Moose population growth rate was negatively related to moose density and positively related to the abundance of mixed deciduous habitat abundant in forage. Calf recruitment was negatively related to a later start of the growing season and calf harvest. The ratio of bulls to cows was related to male harvest and hunter access, and thresholds were evident in predictor variables for all vital rate models. 4. Findings indicate that the contributions of density-dependent and independent factors can vary depending on the scale of population process. The importance of density dependence and habitat supply to low-density ungulate populations was evident, and management strategies for ungulates may be improved by explicitly linking forest management and harvest. Findings emphasize the importance of considering summer climatic influences to ungulate populations, as

  3. Charged Leptons

    CERN Document Server

    Albrecht, J; Babu, K; Bernstein, R H; Blum, T; Brown, D N; Casey, B C K; Cheng, C -h; Cirigliano, V; Cohen, A; Deshpande, A; Dukes, E C; Echenard, B; Gaponenko, A; Glenzinski, D; Gonzalez-Alonso, M; Grancagnolo, F; Grossman, Y; Harnik, R; Hitlin, D G; Kiburg, B; Knoepfe, K; Kumar, K; Lim, G; Lu, Z -T; McKeen, D; Miller, J P; Ramsey-Musolf, M; Ray, R; Roberts, B L; Rominsky, M; Semertzidis, Y; Stoeckinger, D; Talman, R; Van De Water, R; Winter, P

    2013-01-01

    This is the report of the Intensity Frontier Charged Lepton Working Group of the 2013 Community Summer Study "Snowmass on the Mississippi", summarizing the current status and future experimental opportunities in muon and tau lepton studies and their sensitivity to new physics. These include searches for charged lepton flavor violation, measurements of magnetic and electric dipole moments, and precision measurements of the decay spectrum and parity-violating asymmetries.

  4. Density-dependent benefits in ant-hemipteran mutualism? The case of the ghost ant Tapinoma melanocephalum (Hymenoptera: Formicidae and the invasive mealybug Phenacoccus solenopsis (Hemiptera: Pseudococcidae.

    Directory of Open Access Journals (Sweden)

    Aiming Zhou

    Full Text Available Although density-dependent benefits to hemipterans from ant tending have been measured many times, few studies have focused on integrated effects such as interactions between ant tending, natural enemy density, and hemipteran density. In this study, we tested whether the invasive mealybug Phenacoccus solenopsis is affected by tending by ghost ants (Tapinoma melanocephalum, the presence of parasitoids, mealybug density, parasitoid density and interactions among these factors. Our results showed that mealybug colony growth rate and percentage parasitism were significantly affected by ant tending, parasitoid presence, and initial mealybug density separately. However, there were no interactions among the independent factors. There were also no significant interactions between ant tending and parasitoid density on either mealybug colony growth rate or percentage parasitism. Mealybug colony growth rate showed a negative linear relationship with initial mealybug density but a positive linear relationship with the level of ant tending. These results suggest that benefits to mealybugs are density-independent and are affected by ant tending level.

  5. Modeling and analysis of a density-dependent stochastic integral projection model for a disturbance specialist plant and its seed bank.

    Science.gov (United States)

    Eager, Eric Alan; Rebarber, Richard; Tenhumberg, Brigitte

    2014-07-01

    In many plant species dormant seeds can persist in the soil for one to several years. The formation of these seed banks is especially important for disturbance specialist plants, as seeds of these species germinate only in disturbed soil. Seed movement caused by disturbances affects the survival and germination probability of seeds in the seed bank, which subsequently affect population dynamics. In this paper, we develop a stochastic integral projection model for a general disturbance specialist plant-seed bank population that takes into account both the frequency and intensity of random disturbances, as well as vertical seed movement and density-dependent seedling establishment. We show that the probability measures associated with the plant-seed bank population converge weakly to a unique measure, independent of initial population. We also show that the population either persists with probability one or goes extinct with probability one, and provides a sharp criteria for this dichotomy. We apply our results to an example motivated by wild sunflower (Helianthus annuus) populations, and explore how the presence or absence of a "storage effect" impacts how a population responds to different disturbance scenarios.

  6. Non-density dependent pollen dispersal of Shorea maxwelliana (Dipterocarpaceae revealed by a Bayesian mating model based on paternity analysis in two synchronized flowering seasons.

    Directory of Open Access Journals (Sweden)

    Shinsuke Masuda

    Full Text Available Pollinator syndrome is one of the most important determinants regulating pollen dispersal in tropical tree species. It has been widely accepted that the reproduction of tropical forest species, especially dipterocarps that rely on insects with weak flight for their pollination, is positively density-dependent. However differences in pollinator syndrome should affect pollen dispersal patterns and, consequently, influence genetic diversity via the mating process. We examined the pollen dispersal pattern and mating system of Shorea maxwelliana, the flowers of which are larger than those of Shorea species belonging to section Mutica which are thought to be pollinated by thrips (weak flyers. A Bayesian mating model based on the paternity of seeds collected from mother trees during sporadic and mass flowering events revealed that the estimated pollen dispersal kernel and average pollen dispersal distance were similar for both flowering events. This evidence suggests that the putative pollinators - small beetles and weevils - effectively contribute to pollen dispersal and help to maintain a high outcrossing rate even during sporadic flowering events. However, the reduction in pollen donors during a sporadic event results in a reduction in effective pollen donors, which should lead to lower genetic diversity in the next generation derived from seeds produced during such an event. Although sporadic flowering has been considered less effective for outcrossing in Shorea species that depend on thrips for their pollination, effective pollen dispersal by the small beetles and weevils ensures outcrossing during periods of low flowering tree density, as occurs in a sporadic flowering event.

  7. Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages.

    Science.gov (United States)

    Caughlin, T Trevor; Ferguson, Jake M; Lichstein, Jeremy W; Zuidema, Pieter A; Bunyavejchewin, Sarayudh; Levey, Douglas J

    2015-01-07

    Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now.

  8. 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.

  9. Colominic acid inhibits the proliferation of cultured bovine aortic endothelial cells and injures their monolayers: cell density-dependent effects prevented by sulfation.

    Science.gov (United States)

    Yamamoto, Chika; Morita, Yuki; Yamaguchi, Shinya; Hayashi, Toshimitsu; Kaji, Toshiyuki

    2006-01-18

    Colominic acid (CA), produced by Escherichia coli K1, is a polymer of sialic acid linked through alpha (2-->8) glycosidic linkages. Although there are several studies on the biological activities of chemically sulfated CA, the activity of CA has been incompletely understood. In the present study, we investigated the effects of CA, prepared as an alpha2,8-linked homopolymer of N-acetylneuraminic acid, on the proliferation and monolayer maintenance of bovine aortic endothelial cells in culture. The results indicate that CA potently inhibits the proliferation of sparse endothelial cells without nonspecific cell damage. The inhibitory effect of CA was markedly stronger than those of sodium spirulan and calcium spirulan, known polysaccharides that inhibit endothelial cell proliferation. On the other hand, in dense endothelial cells, CA induced nonspecific cell damage and markedly injured the monolayer. These results indicate that CA has two distinct effects on vascular endothelial cells: one is the inhibition of proliferation when the cell density is low, and the other is the nonspecific cytotoxicity when the cell density is high. Interestingly, these cell density-dependent effects of CA could be prevented by sulfation of the CA chains. Therefore, it is concluded that CA not only inhibits the proliferation of sparse endothelial cells without nonspecific cell damage but also injures dense cells in a monolayer by nonspecific cytotoxicity, which can be prevented by sulfation of the polysaccharide.

  10. Electrically charged curvaton

    CERN Document Server

    D'Onofrio, Michela; Rajantie, Arttu

    2012-01-01

    We consider the possibility that the primordial curvature perturbation was generated through the curvaton mechanism from a scalar field with an electric charge, or precisely the Standard Model U(1) weak hypercharge. This links the dynamics of the very early universe concretely to the Standard Model of particle physics, and because the coupling strength is known, it reduces the number of free parameters in the curvaton model. We show that the model is compatible with CMB observations for Hubble rate $H_* > 10^8 GeV$ and curvaton mass $m > 10^{-2}H_*$. Charge fluctuations generated during inflation are screened by electron-positron pairs, and therefore do not violate observational constraints. The interaction with the gauge field leads to interesting dynamics after inflation, including resonant preheating, with potentially highly non-trivial observational consequences, which should be studied more carefully using numerical field theory simulations.

  11. Significant enhancement of the charging efficiency in the cavities of ferroelectrets through gas exchange during charging

    Science.gov (United States)

    Qiu, Xunlin

    2016-11-01

    Ferroelectrets are non-polar polymer foams or polymer systems with internally charged cavities. They are charged through a series of dielectric barrier discharges (DBDs) that are caused by the electrical breakdown of the gas inside the cavities. Thus, the breakdown strength of the gas strongly influences the charging process of ferroelectrets. A gas with a lower breakdown strength has a lower threshold voltage, thus decreasing the onset voltage for DBD charging. However, a lower threshold voltage also leads to a lower value for the remanent polarization, as back discharges that are caused by the electric field of the internally deposited charges can take place already at lower charge levels. On this basis, a charging strategy is proposed where the DBDs start in a gas with a lower breakdown strength (in the present example, helium) and are completed at a higher breakdown strength (e.g., nitrogen or atmospheric air). Thus, the exchange of the gas in the cavities during charging can significantly enhance the charging efficiency, i.e., yield much higher piezoelectric coefficients in ferroelectrets at significantly lower charging voltages.

  12. Controlling charge quantization with quantum fluctuations

    Science.gov (United States)

    Jezouin, S.; Iftikhar, Z.; Anthore, A.; Parmentier, F. D.; Gennser, U.; Cavanna, A.; Ouerghi, A.; Levkivskyi, I. P.; Idrisov, E.; Sukhorukov, E. V.; Glazman, L. I.; Pierre, F.

    2016-08-01

    In 1909, Millikan showed that the charge of electrically isolated systems is quantized in units of the elementary electron charge e. Today, the persistence of charge quantization in small, weakly connected conductors allows for circuits in which single electrons are manipulated, with applications in, for example, metrology, detectors and thermometry. However, as the connection strength is increased, the discreteness of charge is progressively reduced by quantum fluctuations. Here we report the full quantum control and characterization of charge quantization. By using semiconductor-based tunable elemental conduction channels to connect a micrometre-scale metallic island to a circuit, we explore the complete evolution of charge quantization while scanning the entire range of connection strengths, from a very weak (tunnel) to a perfect (ballistic) contact. We observe, when approaching the ballistic limit, that charge quantization is destroyed by quantum fluctuations, and scales as the square root of the residual probability for an electron to be reflected across the quantum channel; this scaling also applies beyond the different regimes of connection strength currently accessible to theory. At increased temperatures, the thermal fluctuations result in an exponential suppression of charge quantization and in a universal square-root scaling, valid for all connection strengths, in agreement with expectations. Besides being pertinent for the improvement of single-electron circuits and their applications, and for the metal-semiconductor hybrids relevant to topological quantum computing, knowledge of the quantum laws of electricity will be essential for the quantum engineering of future nanoelectronic devices.

  13. Space charge fields in DC cables

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C; Pedersen, Aage

    1996-01-01

    The space charge that accumulates in DC cables can, mathematically, be resolved into two components. One is related to the temperature and the other to the magnitude of the electric field strength. Analytical expressions for the electric fields arising from each of these space charge components...

  14. 密度制约决定的植物生物量分配格局%Density dependence-determined plant biomass allocation pattern

    Institute of Scientific and Technical Information of China (English)

    黎磊; 周道玮; 盛连喜

    2011-01-01

    基于自然环境下红葱(Allium cepa var.proliferum)个体各器官生物量积累动态、生物量分配比例动态、生物量比率动态和形态性状对不同种群密度(36、49、64、121和225株·m-2)响应的模拟实验,分析了密度制约对其生物量分配格局的影响.结果表明:红葱地上部分、叶和鞘的生物量分配比例均随密度的增加而增加,地下部分和鳞茎的分配比例随密度的增加而下降,而根的分配比例未随密度发生显著变化.除根:叶、根:地上比在密度处理间无显著差异外,各器官间生物量比率均表现出明显的密度依赖性.随着个体的生长,根:鞘、根:叶、根:地上比逐渐减小,鳞茎:叶、鳞茎:鞘、鳞茎:地上比先减小后增加,而地上:地下比先增加后减小.比叶面积与密度呈显著正相关(P0. 05 ). All the results suggested that intraspecific competition exerted great influence on the resource allocation inside plant bodies. In response to different plant densities, the biomass allocation patterns displayed plasticity. With the increase of plant density, the photosynthates allocated more to above-ground vegetative organs, with the cost of decreasing the photosynthates allocation to below-ground asexsual reproductive organ. It was appeared that the “optimal partitioning theory” was only applicable at the absence of plant competition between individual plants. When the competition between plants was present, the population density and density-dependent regulation were the important factors determining plant biomass allocation pattern.

  15. Density dependence and climate effects in Rocky Mountain elk: an application of regression with instrumental variables for population time series with sampling error.

    Science.gov (United States)

    Creel, Scott; Creel, Michael

    2009-11-01

    1. Sampling error in annual estimates of population size creates two widely recognized problems for the analysis of population growth. First, if sampling error is mistakenly treated as process error, one obtains inflated estimates of the variation in true population trajectories (Staples, Taper & Dennis 2004). Second, treating sampling error as process error is thought to overestimate the importance of density dependence in population growth (Viljugrein et al. 2005; Dennis et al. 2006). 2. In ecology, state-space models are used to account for sampling error when estimating the effects of density and other variables on population growth (Staples et al. 2004; Dennis et al. 2006). In econometrics, regression with instrumental variables is a well-established method that addresses the problem of correlation between regressors and the error term, but requires fewer assumptions than state-space models (Davidson & MacKinnon 1993; Cameron & Trivedi 2005). 3. We used instrumental variables to account for sampling error and fit a generalized linear model to 472 annual observations of population size for 35 Elk Management Units in Montana, from 1928 to 2004. We compared this model with state-space models fit with the likelihood function of Dennis et al. (2006). We discuss the general advantages and disadvantages of each method. Briefly, regression with instrumental variables is valid with fewer distributional assumptions, but state-space models are more efficient when their distributional assumptions are met. 4. Both methods found that population growth was negatively related to population density and winter snow accumulation. Summer rainfall and wolf (Canis lupus) presence had much weaker effects on elk (Cervus elaphus) dynamics [though limitation by wolves is strong in some elk populations with well-established wolf populations (Creel et al. 2007; Creel & Christianson 2008)]. 5. Coupled with predictions for Montana from global and regional climate models, our results

  16. Microsparks Generated by Charged Particles in Dielectric Liquids

    Science.gov (United States)

    Geiger, Robert

    2012-10-01

    The electrodynamics of charged particles in dielectric liquids have been described by several authors [1,2]. As a charged particle approaches an electrode of opposite charge the local electric field eventually exceeds the dielectric strength of the liquid and a microspark is generated. These plasmas can be very small, about Angew. Chem., Int. Ed. 47, 8020.

  17. FATIGUE STRENGTH OF HIGH-STRENGTH STEEL,

    Science.gov (United States)

    coldhardened by deforming to 83%. It was found that it has low static notch sensitivity (lower than that of heat-treated steels), that static strength ...is raised appreciably by increased cold plastic deformation, and that its fatigue strength is raised substantially by mechanical polishing. (Author)

  18. Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites

    Science.gov (United States)

    Christidis, G.E.; Blum, A.E.; Eberl, D.D.

    2006-01-01

    The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis, G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644-655.]. The rheological properties were determined, after sodium exchange using the optimum amount of Na2CO3, from free swelling tests. Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges of - 0.425 to - 0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength, yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this classification scheme the term smectites with intermediate layer charge is proposed. ?? 2006 Elsevier B.V. All rights reserved.

  19. Natural recruitment, density-dependent juvenile survival, and the potential for additive effects of stock enhancement: an experimental evaluation of stocking northern pike (Esox lucius) fry

    DEFF Research Database (Denmark)

    Hühn, Daniel; Lübke, Kay; Skov, Christian;

    2014-01-01

    in self-sustaining stocks. However, limited data based on replicated and controlled experiments are available to support this prediction. We performed a pond experiment (N = 4 per treatment) to compare the stock enhancing outcome of stocking hatchery-reared northern pike (Esox lucius) fry and the natural...... production of young in self-recruiting pike populations. We also added a treatment where pike fry were stocked into ponds that otherwise did not have pike to mimic the absence of natural recruitment. Fry stocking into self-reproducing stocks did not elevate year class strength over unstocked controls......, the partial replacement of natural recruits by hatchery-reared fry, and the lack of additive effects of stock enhancement in naturally reproducing stocks. A stock-enhancing effect of pike fry stocking may only be expected in the absence of natural recruitment....

  20. CHARGE Association

    Directory of Open Access Journals (Sweden)

    Semanti Chakraborty

    2012-01-01

    Full Text Available We present here a case of 17-year-old boy from Kolkata presenting with obesity, bilateral gynecomastia, mental retardation, and hypogonadotrophic hypogonadism. The patient weighed 70 kg and was of 153 cm height. Facial asymmetry (unilateral facial palsy, gynecomastia, decreased pubic and axillary hair, small penis, decreased right testicular volume, non-palpable left testis, and right-sided congenital inguinal hernia was present. The patient also had disc coloboma, convergent squint, microcornea, microphthalmia, pseudohypertelorism, low set ears, short neck, and choanalatresia. He had h/o VSD repaired with patch. Laboratory examination revealed haemoglobin 9.9 mg/dl, urea 24 mg/dl, creatinine 0.68 mg/dl. IGF1 77.80 ng/ml (decreased for age, GH <0.05 ng/ml, testosterone 0.25 ng/ml, FSH-0.95 ΅IU/ml, LH 0.60 ΅IU/ml. ACTH, 8:00 A.M cortisol, FT3, FT4, TSH, estradiol, DHEA-S, lipid profile, and LFT was within normal limits. Prolactin was elevated at 38.50 ng/ml. The patient′s karyotype was 46XY. Echocardiography revealed ventricularseptal defect closed with patch, grade 1 aortic regurgitation, and ejection fraction 67%. Ultrasound testis showed small right testis within scrotal sac and undescended left testis within left inguinal canal. CT scan paranasal sinuses revealed choanalatresia and deviation of nasal septum to the right. Sonomammography revealed bilateral proliferation of fibroglandular elements predominantly in subareoalar region of breasts. MRI of brain and pituitary region revealed markedly atrophic pituitary gland parenchyma with preserved infundibulum and hypothalamus and widened suprasellar cistern. The CHARGE association is an increasingly recognized non-random pattern of congenital anomalies comprising of coloboma, heart defect, choanal atresia, retarded growth and development, genital hypoplasia, ear abnormalities, and/or deafness. [1] These anomalies have a higher probability of occurring together. In this report, we have

  1. Electron impact excitation of highly charged sodium-like ions

    Science.gov (United States)

    Blaha, M.; Davis, J.

    1978-01-01

    Optical transition probabilities and electron collision strengths for Ca X, Fe XVI, Zn XX, Kr XXVI and Mo XXXII are calculated for transitions between n equal to 3 and n equal to 4 levels. The calculations neglect relativistic effects on the radial functions. A semi-empirical approach provides wave functions of the excited states; a distorted wave function without exchange is employed to obtain the excitation cross sections. The density dependence of the relative intensities of certain emission lines in the sodium isoelectronic sequence is also discussed.

  2. Self-Consistent Description of Multipole Strength in Exotic Nuclei I: Method

    CERN Document Server

    Terasaki, J; Bender, M; Dobaczewski, J; Nazarewicz, W; Stoitsov, M V

    2004-01-01

    We use the canonical Hartree-Fock-Bogoliubov basis to implement a completely self-consistent quasiparticle-random-phase approximation with arbitrary Skyrme energy density functionals and density-dependent pairing functionals. The point of the approach is to accurately describe multipole strength functions in spherical even-even nuclei, including weakly-bound drip-line systems. We describe the method and carefully test its accuracy, particularly in handling spurious modes. To illustrate our approach, we calculate isoscalar and isovector monopole, dipole, and quadrupole strength functions in several Sn isotopes, both in the stable region and at the drip lines.

  3. Delayed density-dependent effects and population fluctuations in the prairie vole Microtus ochrogaster%橙腹田鼠中延缓性密度依赖效应和种群波动

    Institute of Scientific and Technical Information of China (English)

    Lowell L. GETZ; Laura E. SIMMS; Joyce E. HOFMANN; Betty McGUIRE

    2004-01-01

    We tested for delayed density-dependent effects on survival and reproduction in a fluctuating population of the prairie vole Microtus ochrogaster monitored at 3.5-day intervals for 63 months. The population underwent four fluctuations in density during the study; all peaked November-January, with winter declines. Survival and reproduction displayed negative density-dependent effects, with an approximate 2-month lag time for maximum effects. There was a 2-month lag for maximum positive effects of increased survival on population density and a 3-month lag in respect to increased reproduction. Extrinsic factors, winter, may have been involved in the delayed density-dependent effects on reproduction, but we could not test for role of intrinsic factors. Seasonal effects did not appear to be responsible for the delayed density-dependent effects on survival. The net effect of the negative delayed density-dependent effects on survival and reproduction are suggested to moderate amplitudes, but not prevent, population fluctuations of M. Ochrogaster.%检验了延迟的密度依赖对橙腹田鼠(Microtus ochrogaster)一个波动种群的生存和生殖的影响,研究持续了63个月,取样间隔为3.5天.在研究期间,该种群的密度经历了4次波动,每次波动的高峰都在11月至次年1月,种群数量在冬季下降.生存和生殖都有负面的密度依赖效应,最大效应具有2个月的时滞.种群存活率增长对种群密度最大的正面效应具有2个月的时滞,而对与增加生殖则有3个月的时滞.内部因素和冬季都可能推延对生殖的密度依赖效应,但是本文未能检验这些内部因素的影响.季节性影响看来与对生存的延缓性密度依赖效应无关.负面的延缓性密度依赖效应对生存和生殖的净作用可能在于减少、而不是阻止橙腹田鼠种群波动的幅度.

  4. Strength and Balance Exercises

    Science.gov (United States)

    ... Peripheral Artery Disease Venous Thromboembolism Aortic Aneurysm More Strength and Balance Exercises Updated:Sep 8,2016 If ... Be Safe While Being Active - Stretching & Flexibility Exercises - Strength & Balance Exercises - Problems & Solutions for Being Active - FAQs ...

  5. Charged impurity-induced scatterings in chemical vapor deposited graphene

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ming-Yang; Tang, Chiu-Chun [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Ling, D. C. [Department of Physics, Tamkang University, Tamsui Dist., New Taipei 25137, Taiwan (China); Li, L. J. [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 11529, Taiwan (China); Chi, C. C.; Chen, Jeng-Chung [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2013-12-21

    We investigate the effects of defect scatterings on the electric transport properties of chemical vapor deposited (CVD) graphene by measuring the carrier density dependence of the magneto-conductivity. To clarify the dominant scattering mechanism, we perform extensive measurements on large-area samples with different mobility to exclude the edge effect. We analyze our data with the major scattering mechanisms such as short-range static scatters, short-range screened Coulomb disorders, and weak-localization (WL). We establish that the charged impurities are the predominant scatters because there is a strong correlation between the mobility and the charge impurity density. Near the charge neutral point (CNP), the electron-hole puddles that are induced by the charged impurities enhance the inter-valley scattering, which is favorable for WL observations. Away from the CNP, the charged-impurity-induced scattering is weak because of the effective screening by the charge carriers. As a result, the local static structural defects govern the charge transport. Our findings provide compelling evidence for understanding the scattering mechanisms in graphene and pave the way for the improvement of fabrication techniques to achieve high-quality CVD graphene.

  6. Strength Training for Girls.

    Science.gov (United States)

    Connaughton, Daniel; Connaughton, Angela; Poor, Linda

    2001-01-01

    Strength training can be fun, safe, and appropriate for young girls and women and is an important component of any fitness program when combined with appropriate cardiovascular and flexibility activities. Concerns and misconceptions regarding girls' strength training are discussed, presenting general principles of strength training for children…

  7. Table of charged particle energies versus magnetic field strength x orbit radius (B{rho}) for A = 1 to 7 (100< (B{rho}) < 1200 kG.cm); Table des energies des particules chargees en fonction de la rigidite magnetique (B{rho}) pour A = 1 a 7 (100< (B{rho}) < 1200 kG.cm)

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, L. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    A table of charged particle energies versus magnetic field strength x orbit radius (B{sub {rho}}) is presented. Particles p, d, t, {sup 3}He{sup ++}, {sup 4}He{sup +}, {sup 4}He{sup ++}, {sup 6}Li{sup +}, {sup 6}Li{sup ++}, {sup 6}Li{sup +++}, {sup 7}Li{sup +}, {sup 7}Li{sup ++}, {sup 7}Li{sup +++}. Values of B{sub {rho}}: 100 to 1200 kG.cm by steps of 0.5 kG.cm. Values of energies are given in keV. (author) [French] Nous presentons une table des energies de protons, deutons, tritons, {sup 3}He{sup ++}, {sup 4}He{sup +}, {sup 4}He{sup ++}, {sup 6}Li{sup +}, {sup 6}Li{sup ++}, {sup 6}Li{sup +++}, {sup 7}Li{sup +}, {sup 7}Li{sup ++}, {sup 7}Li{sup +++} en fonction de leur rigidite magnetique (B{sub {rho}}). Les valeurs de B{sub {rho}} sont comprises entre 100 et 1200 kG.cm par pas de 0.5 kG.cm. Les valeurs des energies sont donnees en keV. (auteur)

  8. Workplace Charging. Charging Up University Campuses

    Energy Technology Data Exchange (ETDEWEB)

    Giles, Carrie [ICF International, Fairfax, VA (United States); Ryder, Carrie [ICF International, Fairfax, VA (United States); Lommele, Stephen [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-03-01

    This case study features the experiences of university partners in the U.S. Department of Energy's (DOE) Workplace Charging Challenge with the installation and management of plug-in electric vehicle (PEV) charging stations.

  9. The strength compass

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    Individual paper presentation: The ‘Strength Compass’. The results of a PhDresearch project among schoolchildren (age 6-16) identifying VIAstrengths concerning age, gender, mother-tongue-langue and possible child psychiatric diagnosis. Strengths-based interventions in schools have a theoretical...... foundation in research in VIA-strengths by Seligman & Peterson (2004) and in research on strengths by Linley (2008). Based on this research the VIA-test was created for adults and later for children and youths from the age of 10. For children younger than 10 years of age Peterson & Park (2011) have made...... interviews with the parents. For younger children there has been no possibility to test for strengths. In a Danish PhD project a tool to map children’s strengths was needed for children aged 6-16 and with permission from the VIA-institute ‘The Strength Compass’ was made in cooperation with The Danish...

  10. Strength Modeling Report

    Science.gov (United States)

    Badler, N. I.; Lee, P.; Wong, S.

    1985-01-01

    Strength modeling is a complex and multi-dimensional issue. There are numerous parameters to the problem of characterizing human strength, most notably: (1) position and orientation of body joints; (2) isometric versus dynamic strength; (3) effector force versus joint torque; (4) instantaneous versus steady force; (5) active force versus reactive force; (6) presence or absence of gravity; (7) body somatotype and composition; (8) body (segment) masses; (9) muscle group envolvement; (10) muscle size; (11) fatigue; and (12) practice (training) or familiarity. In surveying the available literature on strength measurement and modeling an attempt was made to examine as many of these parameters as possible. The conclusions reached at this point toward the feasibility of implementing computationally reasonable human strength models. The assessment of accuracy of any model against a specific individual, however, will probably not be possible on any realistic scale. Taken statistically, strength modeling may be an effective tool for general questions of task feasibility and strength requirements.

  11. Electric Charge in Interaction with Magnetically Charged Black Holes

    CERN Document Server

    Kim, J H

    2007-01-01

    We examine the angular momentum of an electric charge e placed at rest outside a dilaton black hole with magnetic charge Q. The electromagnetic angular momentum which is stored in the electromagnetic field outside the black hole shows several common features regardless of the dilaton coupling strength, though the dilaton black holes are drastically different in their spacetime structure depending on it. First, the electromagnetic angular momentum depends on the separation distance between the two objects and changes monotonically from eQ to 0 as the charge goes down from infinity to the horizon, if rotational effects of the black hole are discarded. Next, as the black hole approaches extremality, however, the electromagnetic angular momentum tends to be independent of the distance between the two objects. It is then precisely $eQ$ as in the electric charge and monopole system in flat spacetime. We discuss why these effects are exhibited and argue that the above features are to hold in widely generic settings ...

  12. Strength of Plastics,

    Science.gov (United States)

    evaluating the strength of structural elements is examined. The book is intended for design engineers, factory laboratory personnel, scientific research workers, and the design institutes. (Author-PL)

  13. Make Dark Matter Charged Again

    CERN Document Server

    Agrawal, Prateek; Randall, Lisa; Scholtz, Jakub

    2016-01-01

    We revisit constraints on dark matter that is charged under a $U(1)$ gauge group in the dark sector, decoupled from Standard Model forces. We find that the strongest constraints in the literature are subject to a number of mitigating factors. For instance, the naive dark matter thermalization timescale in halos is corrected by saturation effects that slow down isotropization for modest ellipticities. The weakened bounds uncover interesting parameter space, making models with weak-scale charged dark matter viable, even with electromagnetic strength interaction. This also leads to the intriguing possibility that dark matter self-interactions within small dwarf galaxies are extremely large, a relatively unexplored regime in current simulations. Such strong interactions suppress heat transfer over scales larger than the dark matter mean free path, inducing a dynamical cutoff length scale above which the system appears to have only feeble interactions. These effects must be taken into account to assess the viabili...

  14. Strength Training and Your Child

    Science.gov (United States)

    ... Old Feeding Your 1- to 2-Year-Old Strength Training and Your Child KidsHealth > For Parents > Strength ... help prevent injuries and speed up recovery. About Strength Training Strength training is the practice of using ...

  15. Strength Training and Your Child

    Science.gov (United States)

    ... Feeding Your 1- to 2-Year-Old Strength Training and Your Child KidsHealth > For Parents > Strength Training ... prevent injuries and speed up recovery. About Strength Training Strength training is the practice of using free ...

  16. Battery charging system

    Energy Technology Data Exchange (ETDEWEB)

    Carollo, J.A.; Kalinsky, W.A.

    1984-02-21

    A battery charger utilizes three basic modes of operation that includes a maintenance mode, a rapid charge mode and time controlled limited charging mode. The device utilizes feedback from the battery being charged of voltage, current and temperature to determine the mode of operation and the time period during which the battery is being charged.

  17. Building on Our Strengths.

    Science.gov (United States)

    Hill, Robert

    1978-01-01

    Comments on the feeling that the American family is disintegrating, and that many criticisms traditionally made about Black families are now made about White families. Suggests that people need to stress family strengths. As an example, five major strengths of Black families are described: flexibility, work and achievement ethics, religiosity, and…

  18. Strengths of Remarried Families.

    Science.gov (United States)

    Knaub, Patricia Kain; And Others

    1984-01-01

    Focuses on remarried families' (N=80) perceptions of family strengths, marital satisfaction, and adjustment to the remarried situation. Results indicated that although most would like to make some changes, scores on the measurements used were high. A supportive environment was the most important predictor of family strength and success. (JAC)

  19. Charge accumulation in DC cables: a macroscopic approach

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C; Pedersen, Aage

    1994-01-01

    The accumulation of space charge in solid dielectrics is examined from the macroscopic point of view using electromagnetic field theory. For practical dielectrics, it is shown that the occurrence of such charges is an inherent consequence of a non-uniform conductivity. The influence of both tempe...... temperature and electric field strength upon this space charge formation is elucidated. Thereafter the theory is applied to DC cables...

  20. Magnetic charge quantisation and fractionally charged quarks

    NARCIS (Netherlands)

    Hooft, G. 't

    1976-01-01

    If magnetic monopoles with Schwinger's value of the magnetic charge would exist then that would pose serious restrictions on theories with fractionally charged quarks, even if they are confined. Weak and electromagnetic interactions must be unified with color, leading to a Weinberg angle w close to

  1. Denied density-dependent seedling recruitment in a fragmented forest does not decrease seedling diversity El denegado reclutamiento denso-dependiente de plántulas en un bosque fragmentado no disminuye la diversidad de plántulas

    Directory of Open Access Journals (Sweden)

    CARLOS E VALDIVIA

    2011-06-01

    Full Text Available Negative density-dependent relationships in plant communities are currently claimed as an important mechanism for the maintenance of plant diversity. However, anthropogenic perturbations such as forest fragmentation might modify such relationships. We evaluated density-dependent relationships between seed and seedling abundance of a tree assemblage in a fragmented forest for estimating seed-to-seedling transitions and their effects on seedling richness. In continuous forest, two out of four and one out of four species presented significant or a tendency to exhibit negative seedling recruitment which is in agreement with other temperate and tropical forests. In forest fragments (1-6 ha, however, this relationship was uncoupled. Seedling richness and diversity, assessed through Shannon-Wiener Index, did not differ between both types of sites. Therefore, forest fragmentation negatively affected seedling recruitment by uncoupling seed-to-seedling transitions, but not by diminishing seedling diversity. This leads to considering the role of density-dependent relationships for the maintenance of plant diversity in communities and claims for including forest fragments into conservation programmes.Las relaciones denso-dependientes negativas en las comunidades vegetales son actualmente señaladas como un importante mecanismo para la mantención de la diversidad de plantas. Sin embargo, las perturbaciones antropogénicas como la fragmentación del bosque podrían modificar este tipo de relaciones. Evaluamos las relaciones denso-dependientes entre las abundancias de semillas y plántulas en un ensamble de árboles en un bosque fragmentado para estimar las transiciones de semillas a plántulas y sus efectos sobre la riqueza de plántulas. En el bosque continuo tres de cuatro especies presentaron reclutamientos de plántulas negativos, lo cual se condice con otros bosques templados y tropicales. En los fragmentos de bosque (1-6 ha, no obstante, estas

  2. Strength of Hard Alloys,

    Science.gov (United States)

    Partial replacement of titanium carbide by tantalum carbide in three-phase WC-TiC-Co alloys tends to have a favorable effect on mechanical properties such as fatigue strength under bending and impact durability.

  3. Density dependent catchability in bottom trawl surveys

    OpenAIRE

    Aglen, Asgeir; Engås, Arill; Godø, Olav Rune; McCallum, Barry R.; Stansbury, Don; Walsh, Stephen J.

    1997-01-01

    Fish form schools, layer or patches in which the individual fish's behaviour is not independent of its neighbours movements. On the other hand, at low densities fish may have the freedom to act as single individuals independently of what other fish are doing. Potentially, if these contrasts occur in nature, they may give rise to behavioural differences of fish in front of the trawl at high and low densities with successive effects on catchability and bottom trawl indices of stock ...

  4. Density dependence in Caenorhabditis larval starvation

    Science.gov (United States)

    Artyukhin, Alexander B.; Schroeder, Frank C.; Avery, Leon

    2013-01-01

    Availability of food is often a limiting factor in nature. Periods of food abundance are followed by times of famine, often in unpredictable patterns. Reliable information about the environment is a critical ingredient of successful survival strategy. One way to improve accuracy is to integrate information communicated by other organisms. To test whether such exchange of information may play a role in determining starvation survival strategies, we studied starvation of L1 larvae in C. elegans and other Caenorhabditis species. We found that some species in genus Caenorhabditis, including C. elegans, survive longer when starved at higher densities, while for others survival is independent of the density. The density effect is mediated by chemical signal(s) that worms release during starvation. This starvation survival signal is independent of ascarosides, a class of small molecules widely used in chemical communication of C. elegans and other nematodes. PMID:24071624

  5. Dynamics of a Nicholson's Model with a Nonlinear Density-dependent Mortality Term%一类具有非线性物种密度制约死亡率的Nicholson模型解的性态

    Institute of Scientific and Technical Information of China (English)

    郝平平; 冯春华

    2012-01-01

    本文利用分析不等式方法来研究Berezansky等人在2010年提出的公开问题之一:一类具有非线性物种密度制约死亡率的Nicholson模型的解的有界性、稳定性和振动性.通过这个方法证明了这个模型解的有界性、振动性,并部分解决了解的稳定性.%By using the method of analysis inequality ,this paper mainly deals with the open problem provided by Berezansky et al. The boundedness and oscillations of the solutions for this Nicholson's model with a nonlinear density-dependent mortality term are investigated,and the stability of the solutions for this model is solved partially.

  6. Charge Distribution Dependency on Gap Thickness of CMS Endcap RPC

    CERN Document Server

    Park, Sung K; Lee, Kyongsei

    2016-01-01

    We report a systematic study of charge distribution dependency of CMS Resistive Plate Chamber (RPC) on gap thickness. Prototypes of double-gap RPCs with six different gap thickness ranging from from 1.0 to 2.0 mm in 0.2-mm steps have been built with 2-mm-thick phenolic high-pressure-laminated plates. The efficiencies of the six gaps are measured as a function of the effective high voltages. We report that the strength of the electric fields of the gap is decreased as the gap thickness is increased. The distributions of charges in six gaps are measured. The space charge effect is seen in the charge distribution at the higher voltages. The logistic function is used to fit the charge distribution data. Smaller charges can be produced within smaller gas gap. But the digitization threshold should be also lowered to utilize these smaller charges.

  7. Complexation behavior of oppositely charged polyelectrolytes: Effect of charge distribution

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Mingtian; Li, Baohui, E-mail: dliang@pku.edu.cn, E-mail: baohui@nankai.edu.cn [School of Physics and Key Laboratory of Functional Polymer Materials of Ministry of Education, Nankai University, Tianjin 300071 (China); Zhou, Jihan; Su, Cuicui; Niu, Lin; Liang, Dehai, E-mail: dliang@pku.edu.cn, E-mail: baohui@nankai.edu.cn [Beijing National Laboratory for Molecular Sciences and the Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

    2015-05-28

    Complexation behavior of oppositely charged polyelectrolytes in a solution is investigated using a combination of computer simulations and experiments, focusing on the influence of polyelectrolyte charge distributions along the chains on the structure of the polyelectrolyte complexes. The simulations are performed using Monte Carlo with the replica-exchange algorithm for three model systems where each system is composed of a mixture of two types of oppositely charged model polyelectrolyte chains (EGEG){sub 5}/(KGKG){sub 5}, (EEGG){sub 5}/(KKGG){sub 5}, and (EEGG){sub 5}/(KGKG){sub 5}, in a solution including explicit solvent molecules. Among the three model systems, only the charge distributions along the chains are not identical. Thermodynamic quantities are calculated as a function of temperature (or ionic strength), and the microscopic structures of complexes are examined. It is found that the three systems have different transition temperatures, and form complexes with different sizes, structures, and densities at a given temperature. Complex microscopic structures with an alternating arrangement of one monolayer of E/K monomers and one monolayer of G monomers, with one bilayer of E and K monomers and one bilayer of G monomers, and with a mixture of monolayer and bilayer of E/K monomers in a box shape and a trilayer of G monomers inside the box are obtained for the three mixture systems, respectively. The experiments are carried out for three systems where each is composed of a mixture of two types of oppositely charged peptide chains. Each peptide chain is composed of Lysine (K) and glycine (G) or glutamate (E) and G, in solution, and the chain length and amino acid sequences, and hence the charge distribution, are precisely controlled, and all of them are identical with those for the corresponding model chain. The complexation behavior and complex structures are characterized through laser light scattering and atomic force microscopy measurements. The order

  8. Charging Graphene for Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jun

    2014-10-06

    Since 2004, graphene, including single atomic layer graphite sheet, and chemically derived graphene sheets, has captured the imagination of researchers for energy storage because of the extremely high surface area (2630 m2/g) compared to traditional activated carbon (typically below 1500 m2/g), excellent electrical conductivity, high mechanical strength, and potential for low cost manufacturing. These properties are very desirable for achieving high activity, high capacity and energy density, and fast charge and discharge. Chemically derived graphene sheets are prepared by oxidation and reduction of graphite1 and are more suitable for energy storage because they can be made in large quantities. They still contain multiply stacked graphene sheets, structural defects such as vacancies, and oxygen containing functional groups. In the literature they are also called reduced graphene oxide, or functionalized graphene sheets, but in this article they are all referred to as graphene for easy of discussion. Two important applications, batteries and electrochemical capacitors, have been widely investigated. In a battery material, the redox reaction occurs at a constant potential (voltage) and the energy is stored in the bulk. Therefore, the energy density is high (more than 100 Wh/kg), but it is difficult to rapidly charge or discharge (low power, less than 1 kW/kg)2. In an electrochemical capacitor (also called supercapacitors or ultracapacitor in the literature), the energy is stored as absorbed ionic species at the interface between the high surface area carbon and the electrolyte, and the potential is a continuous function of the state-of-charge. The charge and discharge can happen rapidly (high power, up to 10 kW/kg) but the energy density is low, less than 10 Wh/kg2. A device that can have both high energy and high power would be ideal.

  9. Electrodynamics of Radiating Charges

    Directory of Open Access Journals (Sweden)

    Øyvind Grøn

    2012-01-01

    Full Text Available The theory of electrodynamics of radiating charges is reviewed with special emphasis on the role of the Schott energy for the conservation of energy for a charge and its electromagnetic field. It is made clear that the existence of radiation from a charge is not invariant against a transformation between two reference frames that has an accelerated motion relative to each other. The questions whether the existence of radiation from a uniformly accelerated charge with vanishing radiation reaction force is in conflict with the principle of equivalence and whether a freely falling charge radiates are reviewed. It is shown that the resolution of an electromagnetic “perpetuum mobile paradox” associated with a charge moving geodetically along a circular path in the Schwarzschild spacetime requires the so-called tail terms in the equation of motion of a charged particle.

  10. High strength alloys

    Energy Technology Data Exchange (ETDEWEB)

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  11. Spin Resonance Strength Calculations

    Science.gov (United States)

    Courant, E. D.

    2009-08-01

    In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.

  12. Spin resonance strength calculations

    Energy Technology Data Exchange (ETDEWEB)

    Courant,E.D.

    2008-10-06

    In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.

  13. High strength alloys

    Science.gov (United States)

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  14. Hand grip strength

    DEFF Research Database (Denmark)

    Frederiksen, Henrik; Gaist, David; Petersen, Hans Christian

    2002-01-01

    in life is a major problem in terms of prevalence, morbidity, functional limitations, and quality of life. It is therefore of interest to find a phenotype reflecting physical functioning which has a relatively high heritability and which can be measured in large samples. Hand grip strength is known......-55%). A powerful design to detect genes associated with a phenotype is obtained using the extreme discordant and concordant sib pairs, of whom 28 and 77 dizygotic twin pairs, respectively, were found in this study. Hence grip strength is a suitable phenotype for identifying genetic variants of importance to mid...

  15. Effect of Charge Patterning on the Phase Behavior of Polymer Coacervates for Charge Driven Self Assembly

    Science.gov (United States)

    Radhakrishna, Mithun; Sing, Charles E.

    Oppositely charged polymers can undergo associative liquid-liquid phase separation when mixed under suitable conditions of ionic strength, temperature and pH to form what are known as `polymeric complex coacervates'. Polymer coacervates find use in diverse array of applications like microencapsulation, drug delivery, membrane filtration and underwater adhesives. The similarity between complex coacervate environments and those in biological systems has also found relevance in areas of bio-mimicry. Our previous works have demonstrated how local charge correlations and molecular connectivity can drastically affect the phase behavior of coacervates. The precise location of charges along the chain therefore dramatically influences the local charge correlations, which consequently influences the phase behavior of coacervates. We investigate the effect of charge patterning along the polymer chain on the phase behavior of coacervates in the framework of the Restricted Primitive Model using Gibbs Ensemble Monte Carlo simulations. Our results show that charge patterning dramatically changes the phase behavior of polymer coacervates, which contrasts with the predictions of the classical Voorn-Overbeek theory. This provides the basis for designing new materials through charge driven self assembly by controlling the positioning of the charged monomers along the chain.

  16. Surface charge mapping with a nanopipette.

    Science.gov (United States)

    McKelvey, Kim; Kinnear, Sophie L; Perry, David; Momotenko, Dmitry; Unwin, Patrick R

    2014-10-01

    Nanopipettes are emerging as simple but powerful tools for probing chemistry at the nanoscale. In this contribution the use of nanopipettes for simultaneous surface charge mapping and topographical imaging is demonstrated, using a scanning ion conductance microscopy (SICM) format. When a nanopipette is positioned close to a surface in electrolyte solution, the direct ion current (DC), driven by an applied bias between a quasi-reference counter electrode (QRCE) in the nanopipette and a second QRCE in the bulk solution, is sensitive to surface charge. The charge sensitivity arises because the diffuse double layers at the nanopipette and the surface interact, creating a perm-selective region which becomes increasingly significant at low ionic strengths (10 mM 1:1 aqueous electrolyte herein). This leads to a polarity-dependent ion current and surface-induced rectification as the bias is varied. Using distance-modulated SICM, which induces an alternating ion current component (AC) by periodically modulating the distance between the nanopipette and the surface, the effect of surface charge on the DC and AC is explored and rationalized. The impact of surface charge on the AC phase (with respect to the driving sinusoidal signal) is highlighted in particular; this quantity shows a shift that is highly sensitive to interfacial charge and provides the basis for visualizing charge simultaneously with topography. The studies herein highlight the use of nanopipettes for functional imaging with applications from cell biology to materials characterization where understanding surface charge is of key importance. They also provide a framework for the design of SICM experiments, which may be convoluted by topographical and surface charge effects, especially for small nanopipettes.

  17. The Strength of Varying Tie Strength

    CERN Document Server

    Bruggeman, Jeroen

    2012-01-01

    "The Strength of Weak Ties" argument (Granovetter 1973) says that the most valuable information is best collected through bridging ties with other social circles than one's own, and that those ties tend to be weak. Aral and Van Alstyne (2011) added that to access complex information, actors need strong ties ("high bandwidth") instead. These insights I generalize by pointing at actors' interest to avoid spending large resources on low value information. Weak ties are well-suited for relatively simple information at low transmission and tie maintenance costs, whereas for complex information, the best outcomes are expected for those actors who vary their bandwidths along with the value of information accessed. To support my claim I use all patents in the USA (two million) over the period 1975-1999. I also show that in rationalized fields, such as technology, bandwidth correlates highly with the value of information, which provides support for using this proxy if value can't be measured directly. Finally, I show ...

  18. Notch strength of composites

    Science.gov (United States)

    Whitney, J. M.

    1983-01-01

    The notch strength of composites is discussed. The point stress and average stress criteria relate the notched strength of a laminate to the average strength of a relatively long tensile coupon. Tests of notched specimens in which microstrain gages have been placed at or near the edges of the holes have measured strains much larger that those measured in an unnotched tensile coupon. Orthotropic stress concentration analyses of failed notched laminates have also indicated that failure occurred at strains much larger than those experienced on tensile coupons with normal gage lengths. This suggests that the high strains at the edge of a hole can be related to the very short length of fiber subjected to these strains. Lockheed has attempted to correlate a series of tests of several laminates with holes ranging from 0.19 to 0.50 in. Although the average stress criterion correlated well with test results for hole sizes equal to or greater than 0.50 in., it over-estimated the laminate strength in the range of hole sizes from 0.19 to 0.38 in. It thus appears that a theory is needed that is based on the mechanics of failure and is more generally applicable to the range of hole sizes and the varieties of laminates found in aircraft construction.

  19. Ion and water transport in charge-modified graphene nanopores

    CERN Document Server

    Qiu, Yinghua; Chen, Weiyu; Si, Wei; Tan, Qiyan; Chen, Yunfei

    2016-01-01

    Porous graphene has high mechanical strength and atomic layer thickness, which make it a promising material for material separation and biomolecule sensing. Electrostatic interactions between charges in aqueous solution are a kind of strong long-range interaction which may have great influence on the fluid transport through nanopores. Here, molecular dynamics simulations were conducted to investigate ion and water transport through a 1.05-nm-in-diameter monolayer graphene nanopore with its edge charge-modified. From the results, it is found that the nanopores are selective to counterions when they are charged. As the charge amount increases, the total ionic currents show an increase-decrease profile while the co-ion currents monotonously decrease. The co-ions rejection can reach 75% and 90% when the nanopores are negatively and positively charged, respectively. Cl ions current increases and reaches a plateau, and Na+ current decreases with the charge amount in the systems where they act as counterions. Beside...

  20. Permanence for a Delayed Nicholson' s Blowflies Model with a Nonlinear Density-dependent Mortality Term%一类具有非线性死亡率的时滞Nicholson 飞蝇方程的持久性

    Institute of Scientific and Technical Information of China (English)

    黄祖达

    2012-01-01

    In this paper, we study a generalized Nicholson' s blowflies model with a nonlinear density-dependent mortality term. Under the admissible initial conditions, by using continuous dependence theorem, some criteria to guarantee the positivity and global existence of solutions are obtained. Then, by applying differential inequality techniques, we give the positive lower bound and upper bound of solutions, and get the permanence of this model. Moreover, we present an example to illustrate our main results.%研究了一类具有非线性死亡率的广义时滞Nicholson飞蝇方程.在容许初值的条件下,利用解的延拓定理,首先证明了该方程的所有解是正的并且是整体存在的,然后利用微分不等式的技巧,证明了该方程所有解具有正的上下确界,获得了该方程所有解具有持久性的充分条件.由于所考虑的模型比同类文献中的模型更加广泛,从而改进和推广了已有文献中的相关结果,并给出了一个具体的例子.

  1. Variable Charge Soils: Mineralogy and Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Nik; Van Ranst, Eric; Noble, Andrew; Baert, Geert

    2003-11-01

    ferromagnesian-rich parent materials) the surfaces of phyllosilicates are coated to a lesser or greater extent by amorphous or crystalline, oppositely charged nanoparticles of Fe and Al oxides. These coatings exhibit a high reactive surface area and help cementing larger particles with one another. As a result of these electrostatic interactions, stable microaggregates that are difficult to disperse are formed in variable charge soils. Most of highly weathered soils have reached the “advanced stage” of Jackson-Sherman weathering sequence that is characterized by the removal of Na, K, Ca, Mg, and Fe(II), the presence of Fe and Al polymers, and very dilute soil solutions with an ionic strength (IS) of less than 1 mmol L-1. The inter-penetration or overlapping of the diffuse double layers on oppositely charged surfaces may occur in these dilute systems. These diffuse layer interactions may affect the magnitude of the effective charge, i.e., the counter-ion charge (4). In addition, salt adsorption, which is defined as the simultaneous adsorption in equivalent amounts of the cation and anion of an electrolyte with no net release of other ions into the soil solution, appears to be a common phenomenon in these soils. They act as cation- and anion-exchangers and as salt-sorbers. The magnitude of salt adsorption depends strongly on initial IS in the soil solution and the presence in appreciable amounts of oppositely charged surfaces. Among the authors that have made illustrious contributions towards a better understanding of these fascinating soil systems are S. Matson, R.K. Schofield, van Olphen, M.E. Sumner, G.W. Thomas, G.P. Gillman, G. Uehara, B.K.G. Theng, K. Wada, N.J. Barrow, J.W. Bowden, R.J. Hunter and G. Sposito. This entry is mainly based on publications by these authors.

  2. Strength Pada Amalgam

    OpenAIRE

    Sri Handayani

    2008-01-01

    Amalgam didefinisikan sebagai campuran dari dua atau beberapa logam (alloy) yang salah satunya adalali merkuri. Dental amalgam sendiri merupakan campuran dari merkuri (Hg), perak (Ag), timah (Sn), tembaga (Cu) dan bahan-bahan lain yang memiliki fungsinya masing-masing, dimana sebagian diantaranya akan saling mengatasi kekurangan yang ditimbulkan logam lain, jika logam tersebut dikombinasikan dengan perbandingan yang tepat. Amalgam mempunyai strength (kekuatan) yang cukup besar sehingga dap...

  3. Character strengths and virtues

    OpenAIRE

    2015-01-01

    The target of this work is to carry out a critical analysis about some of the underlying epistemological assumptions in Peterson and Seligman’s book Character Strengths and Virtues. A handbook and classifications (2004). This is a theoretical investigation that belongs to the epistemology of psychology field. According to the theory proposed by Serroni Copello (2003), a critic progress rational criterion is methodologically applied. The analysis points out some epistemological weakness that l...

  4. Surface Charging and Points of Zero Charge

    CERN Document Server

    Kosmulski, Marek

    2009-01-01

    Presents Points of Zero Charge data on well-defined specimen of materials sorted by trademark, manufacturer, and location. This text emphasizes the comparison between particular results obtained for different portions of the same or very similar material and synthesizes the information published in research reports over the past few decades

  5. Charge transport in organic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ortmann, Frank

    2009-07-01

    The understanding of charge transport is one of the central goals in the research on semiconducting crystals. For organic crystals this is particularly complicated due to the strength of the electron-phonon interaction which requires the description of a seamless transition between the limiting cases of a coherent band-transport mechanism and incoherent hopping. In this thesis, charge transport phenomena in organic crystals are studied by theoretical means. A theory for charge transport in organic crystals is developed which covers the whole temperature range from low T, where it reproduces an expression from the Boltzmann equation for band transport, via elevated T, where it generalizes Holstein's small-polaron theory to finite bandwidths, up to high T, for which a temperature dependence equal to Marcus' electron-transfer theory is obtained. Thereby, coherent band transport and thermally induced hopping are treated on equal footing while simultaneously treating the electron-phonon interaction non-perturbatively. By avoiding the approximation of narrow polaron bands the theory allows for the description of large and small polarons and serves as a starting point for computational studies. The theoretical description is completed by using ab initio material parameters for the selected crystals under study. These material parameters are taken from density functional theory calculations for durene, naphthalene, and guanine crystals. Besides the analysis of the transport mechanism, special focus is put on the study of the relationship between mobility anisotropy and structure of the crystals. This study is supported by a 3D-visualization method for the transport channels in such crystals which has been derived in this thesis. (orig.)

  6. Rain Drop Charge Sensor

    Science.gov (United States)

    S, Sreekanth T.

    begin{center} Large Large Rain Drop Charge Sensor Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , S. Murali Das (2) *Atmospheric Sciences Division, Centre for Earth Science Studies, Thiruvananthapuram 695011 (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) Kavyam, Manacaud, Thiruvananthapuram 695009 begin{center} ABSTRACT To study the inter-relations with precipitation electricity and precipitation microphysical parameters a rain drop charge sensor was designed and developed at CESS Electronics & Instrumentation Laboratory. Simultaneous measurement of electric charge and fall speed of rain drops could be done using this charge sensor. A cylindrical metal tube (sensor tube) of 30 cm length is placed inside another thick metal cover opened at top and bottom for electromagnetic shielding. Mouth of the sensor tube is exposed and bottom part is covered with metal net in the shielding cover. The instrument is designed in such a way that rain drops can pass only through unhindered inside the sensor tube. When electrically charged rain drops pass through the sensor tube, it is charged to the same magnitude of drop charge but with opposite polarity. The sensor tube is electrically connected the inverted input of a current to voltage converter operational amplifier using op-amp AD549. Since the sensor is electrically connected to the virtual ground of the op-amp, the charge flows to the ground and the generated current is converted to amplified voltage. This output voltage is recorded using a high frequency (1kHz) voltage recorder. From the recorded pulse, charge magnitude, polarity and fall speed of rain drop are calculated. From the fall speed drop diameter also can be calculated. The prototype is now under test running at CESS campus. As the magnitude of charge in rain drops is an indication of accumulated charge in clouds in lightning, this instrument has potential application in the field of risk and disaster management. By knowing the charge

  7. Induced Charge Capacitive Deionization

    CERN Document Server

    Rubin, S; Biesheuvel, P M; Bercovici, M

    2016-01-01

    We demonstrate the phenomenon of induced-charge capacitive deionization (ICCDI) that occurs around a porous and conducting particle immersed in an electrolyte, under the action of an external electrostatic field. The external electric field induces an electric dipole in the porous particle, leading to capacitive charging of its volume by both cations and anions at opposite poles. This regime is characterized both by a large RC charging time and a small electrochemical charge relaxation time, which leads to rapid and significant deionization of ionic species from a volume which is on the scale of the particle. We show by theory and experiment that the transient response around a cylindrical particle results in spatially non-uniform charging and non-steady growth of depletion regions which emerge around the particle's poles. Potentially, ICCDI can be useful in applications where fast concentration changes of ionic species are required over large volumes.

  8. Space-Charge Compensation Options for the LHC Injector Complex

    CERN Document Server

    Aiba, M; Dorda, U; Franchetti, G; Garoby, R; Koutchouk, Jean-Pierre; Martini, M; Métral, E; Papaphilippou, Y; Scandale, Walter; Shiltsev, V; Zimmermann, F

    2007-01-01

    Space-charge effects have been identified as the most serious intensity limitation in the CERN PS and PS Booster, on the way towards ultimate LHC performance and beyond. We here explore the application of several previously proposed space-charge compensation methods to the two LHC pre-injector rings, and the challenges which need to be overcome. The methods considered include the reduction of tune shift and resonance strengths via octupoles, pole-face windings, electron lenses, or neutralisation.

  9. Strength Properties of Aalborg Clay

    DEFF Research Database (Denmark)

    Iversen, Kirsten Malte; Nielsen, Benjaminn Nordahl; Augustesen, Anders Hust

    resulted in many damaged buildings in Aalborg. To provide sufficient bearing capacity it is therefore necessary either to remove the fill or to construct the building on piles. Both methods imply that the strength of Aalborg Clay is important for the construction. This paper evaluates the strength...... of Aalborg Clay by use of triaxial tests from four different locations. Both the drained strength (c and ϕ) and the undrained strength (cu) are assessed through two different methods: one where the strength is assumed to vary with the effective stress and another where the strength is found to be constant....

  10. Colloids with continuously tunable surface charge.

    Science.gov (United States)

    van Ravensteijn, Bas G P; Kegel, Willem K

    2014-09-09

    In this paper, we present a robust way to tune the surface potential of polystyrene colloids without changing the pH, ionic strength, etc. The colloids are composed of a cross-linked polystyrene core and a cross-linked vinylbenzyl chloride layer. Besides the chlorine groups, the particle surface contains sulfate/sulfonate groups (arising from the polymerization initiators) that provide a negative surface potential. Performing a Menschutkin reaction on the surface chlorine groups with tertiary amines allows us to introduce quaternary, positively charged amines. The overall charge on the particles is then determined by the ratio between the sulfate/sulfonate moieties and the quaternary amines. Using this process, we were able to invert the charge in a continuous manner without losing colloidal stability upon passing the isoelectric point. The straightforward reaction mechanism together with the fact that the reaction could be quenched rapidly resulted in a colloidal system in which the ζ potential can be tuned between -80 and 45 mV. As proof of principle, the positively charged particles were used in heterocoagulation experiments with nanometer- and micrometer-sized negatively charged silica particles to create geometrically well-defined colloidal (nano) clusters.

  11. Charged Water Droplets can Melt Metallic Electrodes

    Science.gov (United States)

    Elton, Eric; Rosenberg, Ethan; Ristenpart, William

    2016-11-01

    A water drop, when immersed in an insulating fluid, acquires charge when it contacts an energized electrode. Provided the electric field is strong enough, the drop will move away to the opposite electrode, acquire the opposite charge, and repeat the process, effectively 'bouncing' back and forth between the electrodes. A key implicit assumption, dating back to Maxwell, has been that the electrode remains unaltered by the charging process. Here we demonstrate that the electrode is physically deformed during each charge transfer event with an individual water droplet or other conducting object. We used optical, electron, and atomic force microscopy to characterize a variety of different metallic electrodes before and after drops were electrically bounced on them. Although the electrodes appear unchanged to the naked eye, the microscopy reveals that each charge transfer event yielded a crater approximately 1 micron wide and 50 nm deep, with the exact dimensions proportional to the applied field strength. We present evidence that the craters are formed by localized melting of the electrodes via Joule heating in the metal and concurrent dielectric breakdown of the surrounding fluid, suggesting that the electrode locally achieves temperatures exceeding 3400°C. Present address: Dept. Materials Sci. Engineering, MIT.

  12. Weather, cultivar and density-dependent processes influence on aphid in alfalfa Influência do clima, da cultivar e de processos dependentes da densidade sobre afídeos em alfafa

    Directory of Open Access Journals (Sweden)

    Alexandre de Almeida e Silva

    2007-01-01

    Full Text Available It is important to understand the effects of weather, insect density and plant cultivar on insect abundance to predict and prevent crop production loss. The present work investigated the influence of such factors on aphid in alfalfa during one year (short term. Data was collected from September/1997 to August/1998 at Canchin Farm (CCPSE-EMBRAPA, São Carlos, State of São Paulo, Brazil. Weather conditions had, in general, little effect on the variation of aphid populations, but Therioaphis maculata abundance was negatively correlated to humidity. Moreover, high maximum temperatures and low levels of rainfall possible favored T. maculata high abundance on Crioula and P3 cultivars. Therefore, appropriate management of this species is required during hot and dry periods. Population variation of Acyrthosiphon spp., T. maculata and Aphis craccivora seems to be regulated by density dependent processes. Resistant cultivar CUF 101 had a lower abundance of T. maculata and A. craccivora and a narrower population variation than the other cultivars and may reduce their abundance on field. Long-term studies on population dynamics including the effect of climatic conditions and density-dependent factors on plant quality will contribute to pest management in alfalfa fields.É importante entender os efeitos do clima, da densidade dos insetos e da cultivar sobre a abundância de insetos para se predizer e prevenir perdas na produção das culturas. O objetivo do presente trabalho foi analisar a influência desses fatores sobre afídeos em alfafa no período de um ano. Os dados foram coletados de setembro/1997 a agosto/1998 na Fazenda Canchin (CPPSE-EMBRAPA, São Carlos, São Paulo, Brasil. As condições climáticas, em geral, tiveram pequeno efeito sobre a variação populacional dos afídeos, mas a abundância de Therioaphis maculata esteve negativamente correlacionada à umidade. Além disso, as altas temperaturas máximas e os baixos níveis de precipita

  13. Study on the Planting Density Dependence of Pliant Growth of Catalpa ovata G. Don Leaves%梓树叶片可塑生长的密度依赖性研究

    Institute of Scientific and Technical Information of China (English)

    胡满平; 赵秋玲; 戴秀芳; 冯小芹

    2013-01-01

      对梓树进行不同密度的移栽,研究其叶片可塑生长的密度依赖性以及主要叶片性状因子之间的关系。结果表明,随种植密度增加,叶面积、叶干物质含量、生物量呈减少趋势;比叶面积呈先增大后减小趋势。比叶面积与叶片厚度、叶干物质含量之间均呈极显著的负相关,与相对叶绿素含量之间相关性不显著。叶片厚度和叶干物质含量与其它叶性因子的关系较为复杂,在不同种植密度下两者既表现出正相关关系,又表现出负相关关系。%  Catalpa ovata G. Don was transplanted in different planting desity, and the density dependence of leave pliant growth and the relationship between the traits factor of leaves were studied. The results showed that the differences of the leaf area, biomass, specific leaf area, leaf dry matter content were significant with the density increasing . There was a negative correlation between the specific leaf area and leaf thickness, leaf dry matter content, and there was no significant correlation between specific leaf area and chlorophyll content . The analysis on traits factor of leaves showed that the correlation of Leaf thickness and leaf dry matter content and other leaf traits were more complex relationship, and a positive correlation between both, but also exhibits a negative correlation under the different planting density.

  14. Electric vehicle battery charging controller

    DEFF Research Database (Denmark)

    2016-01-01

    The present invention provides an electric vehicle charging controller. The charging controller comprises a first interface connectable to an electric vehicle charge source for receiving a charging current, a second interface connectable to an electric vehicle for providing the charging current...... to a battery management system in the electric vehicle to charge a battery therein, a first communication unit for receiving a charging message via a communication network, and a control unit for controlling a charging current provided from the charge source to the electric vehicle, the controlling at least...

  15. FIELD STRENGTH MEASUREMENTS, PHASE I.

    Science.gov (United States)

    The program included the testing and evaluation of commercial and military field- strength meters. It also included a study of the interpretation of...field- strength measurement data taken under multipath conditions. As part of the field- strength meter evaluation, five instruments, the AN/TRM-7, NF...interpretation of the measured data is the variability of field- strength values obtained over an area. Such variability is caused by the presence of multipath

  16. Strength of Rewelded Inconel 718

    Science.gov (United States)

    Bayless, E.; Lovoy, C. V.; Mcllwain, M. C.; Munafo, P.

    1982-01-01

    Inconel 718, nickel-based alloy used extensively for high-temperature structural service, welded repeatedly without detriment to its strength. According to NASA report, tests show 12 repairs on same weld joint do not adversely affect ultimate tensile strenth, yield strength, fatigue strength, metallurgical grain structures, or ability of weld joint to respond to post weld heat treatments.

  17. Strength Training and Children's Health.

    Science.gov (United States)

    Faigenbaum, Avery D.

    2001-01-01

    Provides an overview of the potential health benefits of strength training for children, discussing the role of strength training in preventing sports-related injuries and highlighting design considerations for such programs. The focus is on musculoskeletal adaptations to strength training that are observable in healthy children. Guidelines for…

  18. Microchip electrophoresis at elevated temperatures and high separation field strengths.

    Science.gov (United States)

    Mitra, Indranil; Marczak, Steven P; Jacobson, Stephen C

    2014-02-01

    We report free-solution microchip electrophoresis performed at elevated temperatures and high separation field strengths. We used microfluidic devices with 11 cm long separation channels to conduct separations at temperatures between 22 (ambient) and 45°C and field strengths from 100 to 1000 V/cm. To evaluate separation performance, N-glycans were used as a model system and labeled with 8-aminopyrene-1,3,6-trisulfonic acid to impart charge for electrophoresis and render them fluorescent. Typically, increased diffusivity at higher temperatures leads to increased axial dispersion and poor separation performance; however, we demonstrate that sufficiently high separation field strengths offset the impact of increased diffusivity in order to maintain separation efficiency. Efficiencies for these free-solution separations are the same at temperatures of 25, 35, and 45°C with separation field strengths ≥ 500 V/cm.

  19. An improved charge pump with suppressed charge sharing effect

    Directory of Open Access Journals (Sweden)

    Na Bai

    2013-09-01

    Full Text Available A differential charge pump with reduced charge sharing effect is presented. The current-steering topology is adopted for fast switching. A replica charge pump is added to provide a current path for the complementary branch of the master charge pump in the current switching. Through the replica charge pump, the voltage at the complementary node of the master charge pump keeps stable during switching, and the dynamic charge sharing effect is avoided. Apply the charge pump to a 4.8 GHz band integer-N PLL, the measured reference spur is -49.7dBc with a 4-MHz reference frequency.

  20. Space-Charge Effect

    CERN Document Server

    Chauvin, N

    2013-01-01

    First, this chapter introduces the expressions for the electric and magnetic space-charge internal fields and forces induced by high-intensity beams. Then, the root-mean-square equation with space charge is derived and discussed. In the third section, the one-dimensional Child-Langmuir law, which gives the maximum current density that can be extracted from an ion source, is exposed. Space-charge compensation can occur in the low-energy beam transport lines (located after the ion source). This phenomenon, which counteracts the spacecharge defocusing effect, is explained and its main parameters are presented. The fifth section presents an overview of the principal methods to perform beam dynamics numerical simulations. An example of a particles-in-cells code, SolMaxP, which takes into account space-charge compensation, is given. Finally, beam dynamics simulation results obtained with this code in the case of the IFMIF injector are presented.

  1. Primitive Virtual Negative Charge

    CERN Document Server

    Kim, Kiyoung

    2008-01-01

    Physical fields, such as gravity and electromagnetic field, are interpreted as results from rearrangement of vacuum particles to get the equilibrium of net charge density and net mass density in 4-dimensional complex space. Then, both fields should interact to each other in that physical interaction is considered as a field-to-field interaction. Hence, Mass-Charge interaction is introduced with primitive-virtual negative charge defined for the mass. With the concept of Mass-Charge interaction electric equilibrium of the earth is discussed, especially about the electric field and magnetic field of the earth. For unsettled phenomena related with the earth's gravity, such as antigravity phenomenon, gravity anomalies during the solar eclipses, the connection between geomagnetic storms and earthquakes, etc., possible explanations are discussed.

  2. Water Quality Protection Charges

    Data.gov (United States)

    Montgomery County of Maryland — The Water Quality Protection Charge (WQPC) is a line item on your property tax bill. WQPC funds many of the County's clean water initiatives including: • Restoration...

  3. Overcoming charge noise decoherence by photon-assisted pair-breaking in a charge qubit

    Science.gov (United States)

    de Graaf, Sebastian; Leppäkangas, Juha; Adamyan, Astghik; Danilov, Andrey; Lindström, Tobias; Fogelström, Mikael; Johansson, Göran; Kubatkin, Sergey

    2014-03-01

    We report on recent measurements of a charge qubit, a Cooper-pair box, coupled to a high-Q microwave cavity in the strong driving regime. This we model using a dressed state formalism, and we find evidence for a process that involves energy transfer corresponding to a large number (~14) of photons. This energy is sufficient to break a Cooper-pair on the island, and it results in a new relaxation channel for the qubit. Specifically, this relaxation resets the qubit into a charge state determined by the static bias conditions, resulting in a sudden population inversion around each dressed state degeneracy point. At low driving strengths, decoherence is governed by charge noise in the environment, while in the discovered strong driving regime the relaxation rate due to pair-breaking can overcome the environmental charge relaxation rate. This results in a regime that is especially attractive for charge sensing since the qubit response becomes immune to non-equilibrium quasiparticle poisoning and less susceptible to its charge noise environment.

  4. Electric Vehicle Charging Modeling

    OpenAIRE

    Grahn, Pia

    2014-01-01

    With an electrified passenger transportation fleet, carbon dioxide emissions could be reduced significantly depending on the electric power production mix. Increased electric power consumption due to electric vehicle charging demands of electric vehicle fleets may be met by increased amount of renewable power production in the electrical systems. With electric vehicle fleets in the transportation system there is a need for establishing an electric vehicle charging infrastructure that distribu...

  5. Electrically charged targets

    Science.gov (United States)

    Goodman, Ronald K.; Hunt, Angus L.

    1984-01-01

    Electrically chargeable laser targets and method for forming such charged targets in order to improve their guidance along a predetermined desired trajectory. This is accomplished by the incorporation of a small amount of an additive to the target material which will increase the electrical conductivity thereof, and thereby enhance the charge placed upon the target material for guidance thereof by electrostatic or magnetic steering mechanisms, without adversely affecting the target when illuminated by laser energy.

  6. Charge-sensitive amplifier

    Directory of Open Access Journals (Sweden)

    Startsev V. I.

    2008-02-01

    Full Text Available The authors consider design and circuit design techniques of reduction of the influence of the pyroelectric effect on operation of the charge sensitive amplifiers. The presented experimental results confirm the validity of the measures taken to reduce the impact of pyroelectric currents. Pyroelectric currents are caused by the influence of the temperature gradient on the piezoelectric sensor and on the output voltage of charge sensitive amplifiers.

  7. Numerical simulation of the effect of wind removing the corona space charge over grounded structures under thunderstorm conditions

    DEFF Research Database (Denmark)

    Vogel, Stephan; Lopez, Javier; Holbøll, Joachim;

    2015-01-01

    that the effectof the removal of the corona space charge by the wind leadsto a higher field strength at the grounded object and, therefore,it becomes easier for it to initiate an upward connecting leadercompared to a situation where the space charge is present. Inthis work, a simplified space charge drift model...

  8. Natural Limits for Currents in Charge Separated Pulsar Magnetospheres

    CERN Document Server

    Jessner, A; Kunzl, T A

    2002-01-01

    Rough estimates and upper limits on current and particle densities form the basis of most of the canonical pulsar models. Whereas the surface of the rotating neutron star is capable of supplying sufficient charges to provide a current that, given the polar cap potential, could easily fuel the observed energy loss processes, observational and theoretical constraints provide strict upper limits to the charge densities. The space charge of a current consisting solely of particles having only one sign creates a compensating potential that will make the maximum current dependent on potential and distance. In the non-relativistic case this fact is expressed in the familiar Child-Langmuir law. Its relativistic generalization and subsequent application to the inner pulsar magnetosphere provides clear limits on the strength and radial extension of charged currents originating on the polar cap. Violent Pierce-type oscillations set in, if one attempts to inject more current than the space charge limit into a given volum...

  9. Effect of exciton oscillator strength on upconversion photoluminescence in GaAs/AlAs multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Osamu, E-mail: kojima@phoenix.kobe-u.ac.jp; Okumura, Shouhei; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan); Akahane, Kouichi [National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2014-11-03

    We report upconversion photoluminescence (UCPL) in GaAs/AlAs multiple quantum wells. UCPL from the AlAs barrier is caused by the resonant excitation of the excitons in the GaAs well. When the quantum well has sufficient miniband width, UCPL is hardly observed because of the small exciton oscillator strength. The excitation-energy and excitation-density dependences of UCPL intensity show the exciton resonant profile and a linear increase, respectively. These results demonstrate that the observed UCPL caused by the saturated two-step excitation process requires a large number of excitons.

  10. On strength of porous material

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1999-01-01

    The question of non-destructive testing of porous materials has always been of interest for the engineering profession. A number of empirically based MOE-MOR relations between stiffness (Modulus Of Elasticity) and strength (Modulus OF Rupture) of materials have been established in order to control...... to the theoretical research on non-destructive testing of such materials relating strength to stiffness and pore geometry.It is demonstrated that solutions for stiffness, tensile strength, and pore strength (damaging pore pressure, frost, fire) for some ideal porous materials can be determined theoretically only...... from knowing about pore geometry, solid phase stiffness, and zero-porosity strength. Pore geometry is the very important common denominator which controls both both stiffness and strength.The accurate results obtained are finally used to suggest generalizations with respect to strength in general...

  11. On-line charge breeding using ECRIS and EBIS

    Science.gov (United States)

    Vondrasek, Richard

    2016-06-01

    The efficient and rapid production of a high-quality, pure beam of highly charged ions is at the heart of any radioactive ion beam facility. Whether an electron cyclotron resonance (ECR) ion source or an electron beam ion source (EBIS) is used to produce these highly charged ions, their operating characteristics will set the boundaries on the range of experiments which can be performed. In addition, time structure and duty cycle have to be considered when defining the operating parameters of the accelerator system as a whole. At Argonne National Laboratory (ANL), an ECR charge breeder was developed as part of the Californium Rare Ion Breeder Upgrade (CARIBU) program. The charge breeding efficiency and high charge state production of the source is at the forefront of ECR charge breeders, but its overall performance as part of the accelerator system is limited by pervasive background and relatively long breeding times. As such, an EBIS charge breeder has been developed and is running in an off-line configuration. It has already demonstrated good breeding efficiencies, shorter residence times, and reduced background and is scheduled to replace the ECR charge breeder in late 2015. The resultant change in duty cycle and time structure necessitates changes to the overall operation of the facility. The experiences with these breeders, as well as from several other facilities which already utilize an ECR or EBIS for charge breeding, help to define the operational characteristics of each technology - their strengths, their weaknesses, and the possible paths to improvement.

  12. Ion and water transport in charge-modified graphene nanopores

    Institute of Scientific and Technical Information of China (English)

    裘英华; 李堃; 陈伟宇; 司伟; 谭启檐; 陈云飞

    2015-01-01

    Porous graphene has a high mechanical strength and an atomic-layer thickness that makes it a promising material for material separation and biomolecule sensing. Electrostatic interactions between charges in aqueous solutions are a type of strong long-range interaction that may greatly infl uence fl uid transport through nanopores. In this study, molecular dynamic simulations were conducted to investigate ion and water transport through 1.05-nm diameter monolayer graphene nanopores, with their edges charge-modified. Our results indicated that these nanopores are selective to counterions when they are charged. As the charge amount increases, the total ionic currents show an increase–decrease profile while the co-ion currents monotonically decrease. The co-ion rejection can reach 76.5%and 90.2%when the nanopores are negatively and positively charged, respectively. The Cl−ion current increases and reaches a plateau, and the Na+current decreases as the charge amount increases in systems in which Na+ions act as counterions. In addition, charge modification can enhance water transport through nanopores. This is mainly due to the ion selectivity of the nanopores. Notably, positive charges on the pore edges facilitate water transport much more strongly than negative charges.

  13. Evaluation of concrete mechanical strength through porosity

    Directory of Open Access Journals (Sweden)

    Olivares, M.

    2004-03-01

    Full Text Available The increasing on voids or pores in any material - if the rest of characteristics remains equal -always causes a decrease in their mechanical strength since the ratio volume/resistant mass is lower Following all these fact a well known conclusion rises: there is a relationship between compacity/porosity and mechanical strengths. The purpose of this research is to establish a new possible correlation between both concrete properties with independence of the proportions, type of cement, size of grain, age, use. etc. So it can be concluded that the results of this research allow the engineer or architect in charge of a restoration or reparation to determine the compression strength of a concrete element. A first step is to determine the porosity through a rather short number of tests. Subsequently, compression strength will be obtained applying just a mathematical formula.

    El aumento de huecos o poros de cualquier material, lo mismo que en otras circunstancias, redunda siempre en una merma de sus resistencias mecánicas, al haber menor volumen-masa resistente. En consecuencia, puede deducirse, que hay una relación entre la compacidad/porosidad y las resistencias mecánicas. En el presente trabajo se estudia una posible correlación entre ambas propiedades del hormigón con independencia de su dosificación, tipo de cemento, granulometría, edad, uso, etc. Las conclusiones obtenidas en la presente investigación permiten al técnico, encargado de una restauración o rehabilitación, determinar la resistencia a compresión de un elemento de hormigón, una vez hallada, de una forma sencilla, la porosidad de una muestra no muy voluminosa, mediante la aplicación de una simple fórmula matemática.

  14. Photoconductivity and Charge-Carrier Photogeneration in Photorefractive Polymers

    NARCIS (Netherlands)

    Däubler, Thomas K.; Kulikovsky, Lazar; Neher, Dieter; Cimrová, Vera; Hummelen, J.C.; Mecher, Erwin; Bittner, Reinhard; Meerholz, Klaus; Lawson, M.; Meerholz, Klaus

    2002-01-01

    We have studied photogeneration, transport, trapping and recombination as the governing mechanisms for the saturation field strength and the time response of the photorefractive (PR) effect in PVK-based PR materials, utilizing xerographic discharge and photoconductivity experiments. Both the charge

  15. Effective dynamics of a classical point charges

    CERN Document Server

    Polonyi, Janos

    2013-01-01

    The effective Lagrangian of a point charge is derived by eliminating the electromagnetic field within the framework of the classical closed time path formalism. The short distance singularity of the electromagnetic field is regulated by an UV cutoff. The Abraham-Lorentz force is recovered and its similarity to anomalies is underlined. The full cutoff-dependent linearized equation of motion is obtained, no runaway trajectories are found but the effective dynamics shows acausality if the cutoff is beyond the classical charge radius. The strength of the radiation reaction force displays a pole in its cutoff-dependence in a manner reminiscent of the Landau-pole of perturbative QED. Similarity between the dynamical breakdown of the time reversal invariance and dynamical symmetry breaking is pointed out.

  16. Phase equilibria in a model of low-salt suspensions of charged colloids

    Science.gov (United States)

    van Roij, René; Evans, Robert

    1999-12-01

    We calculate phase diagrams of low-salt suspensions of charged colloidal particles using a recently proposed effective one-component Hamiltonian for the colloids (van Roij R, Dijkstra M and Hansen J-P 1999 Phys. Rev. E 59 2010). This Hamiltonian consists of the purely repulsive pairwise Derjaguin, Landau, Verwey, and Overbeek (DLVO) potential and density-dependent volume terms. The latter play a crucial role in driving phase transitions at salt concentrations of the order of 10 µM or lower. We find phase diagrams that exhibit gas-liquid coexistence with upper and lower critical points, and, for sufficiently large surface charge densities, upper and lower gas-liquid-solid triple points. A connection between the Debye-Hückel theory for simple electrolytes and the DLVO theory for colloidal suspensions is made.

  17. Nuclear fragmentation and charge-exchange reactions induced by pions in the $\\Delta$-resonance region

    CERN Document Server

    Feng, Zhao-Qing

    2016-01-01

    Dynamics of the nuclear fragmentations and the charge exchange reactions in pion-nucleus collisions near the $\\Delta$(1232) resonance energies has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport model. An isospin, momentum and density-dependent pion-nucleon potential is implemented in the model, which influences the pion dynamics, in particular the kinetic energy spectra, but weakly impacts the fragmentation mechanism. The absorption process in pion-nucleon collisions to form the $\\Delta$(1232) resonance dominates the heating mechanism of target nucleus. The excitation energy transferred to the target nucleus increases with the pion kinetic energy and is similar for both $\\pi^{-}$ and $\\pi^{+}$ induced reactions. The magnitude of fragmentation of target nucleus weakly depends on the pion energy. The isospin ratio in the pion double charge exchange is influenced by the isospin ingredient of target nucleus.

  18. Investigation of the charging characteristics of micrometer sized droplets based on parallel plate capacitor model.

    Science.gov (United States)

    Zhang, Yanzhen; Liu, Yonghong; Wang, Xiaolong; Shen, Yang; Ji, Renjie; Cai, Baoping

    2013-02-01

    The charging characteristics of micrometer sized aqueous droplets have attracted more and more attentions due to the development of the microfluidics technology since the electrophoretic motion of a charged droplet can be used as the droplet actuation method. This work proposed a novel method of investigating the charging characteristics of micrometer sized aqueous droplets based on parallel plate capacitor model. With this method, the effects of the electric field strength, electrolyte concentration, and ion species on the charging characteristics of the aqueous droplets was investigated. Experimental results showed that the charging characteristics of micrometer sized droplets can be investigated by this method.

  19. Charge filling factors in clean and disordered arrays of tunnel junctions.

    Science.gov (United States)

    Walker, Kelly A; Vogt, Nicolas; Cole, Jared H

    2015-12-02

    We simulate one-dimensional arrays of tunnel junctions using the kinetic Monte Carlo method to study charge filling behaviour in the large charging energy limit. By applying a small fixed voltage bias and varying the offset voltage, we investigate this behaviour in clean and disordered arrays (both weak and strong disorder effects). The offset voltage dependent modulation of the current is highly sensitive to background charge disorder and exhibits substantial variation depending on the strength of the disorder. We show that while small fractional charge filling factors are likely to be washed out in experimental devices due to strong background charge disorder, larger factors may be observable.

  20. Character strengths and virtues

    Directory of Open Access Journals (Sweden)

    Mariana Gancedo

    2015-09-01

    Full Text Available The target of this work is to carry out a critical analysis about some of the underlying epistemological assumptions in Peterson and Seligman’s book Character Strengths and Virtues. A handbook and classifications (2004. This is a theoretical investigation that belongs to the epistemology of psychology field. According to the theory proposed by Serroni Copello (2003, a critic progress rational criterion is methodologically applied. The analysis points out some epistemological weakness that leads to incongruences in the statements and conclusions of the investigations, such as: the absence of a unified theory, a candid search of objectivity, and the superposition of implicit paradigms. It also takes notice of a causal and elementary logic -which goes against today’s scientific paradigm-, and the strong American culture zeitgeist present in the principles of Positive Psychology. Finally, some ethic problems are displayed, in particular the step taken from a descriptive attitude –characteristic of science- toward a prescriptive attitude –characteristic of moral codes-. 

  1. Magnetically-charged black branes and viscosity/entropy ratios

    Science.gov (United States)

    Liu, Hai-Shan; Lü, H.; Pope, C. N.

    2016-12-01

    We consider asymptotically-AdS n-dimensional black brane solutions in a theory of gravity coupled to a set of N p-form field strengths, in which the field strengths carry magnetic charges. For appropriately chosen charges, the metrics are isotropic in the ( n - 2) transverse directions. However, in general the field strength configurations break the full Euclidean symmetry of the ( n - 2)-dimensional transverse space, and the shear viscosity tensor in the dual theory is no longer isotropic. We study the linearised equations for transverse traceless metric perturbations in these backgrounds, and by employing the Kubo formula we obtain expressions for the ratios η/S of the shear viscosity components divided by the entropy density. We find that the KSS bound on the ratios η/S is generally violated in these solutions. We also extend the discussion by including a dilatonic scalar field in the theory, leading to solutions that are asymptotically Lifshitz with hyperscaling violation.

  2. FIELD STRENGTH MEASUREMENTS, PHASE II.

    Science.gov (United States)

    The measurement of the strength of radio frequency fields at high frequency and above has followed practices which are standard for the measurement...of field strength at medium and low frequencies. Variability of measurements made in practical situations and a lack of reproducibility of...measurements made under apparently identical conditions has prompted an investigation of equipment and methods used in the determinations. The field strength

  3. Commitee III.1 Ultimate Strength

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher

    1997-01-01

    This report addresses the subject of ductile collapse of ships and offshore structures and their components due to buckling and excessive yielding under overload conditions. Consideration is given to load-deflection predictions for components with fabrication imperfections and in-service damage a...... and to the ultimate strength and post-ultimate behaviour of structural systems in order to identify the reserve strength. The effect of uncertainties in the modelling on the strength predictions is highlighted in two design examples....

  4. Holographic charge density waves

    CERN Document Server

    Donos, Aristomenis

    2013-01-01

    We show that strongly coupled holographic matter at finite charge density can exhibit charge density wave phases which spontaneously break translation invariance while preserving time-reversal and parity invariance. We show that such phases are possible within Einstein-Maxwell-dilaton theory in general spacetime dimensions. We also discuss related spatially modulated phases when there is an additional coupling to a second vector field, possibly with non-zero mass. We discuss how these constructions, and others, should be associated with novel spatially modulated ground states.

  5. Holographic charge density waves

    Science.gov (United States)

    Donos, Aristomenis; Gauntlett, Jerome P.

    2013-06-01

    We show that strongly coupled holographic matter at finite charge density can exhibit charge density wave phases which spontaneously break translation invariance while preserving time-reversal and parity invariance. We show that such phases are possible within Einstein-Maxwell-dilaton theory in general spacetime dimensions. We also discuss related spatially modulated phases when there is an additional coupling to a second vector field, possibly with nonzero mass. We discuss how these constructions, and others, should be associated with novel spatially modulated ground states.

  6. Charges for linearized gravity

    CERN Document Server

    Aksteiner, Steffen

    2013-01-01

    Maxwell test fields as well as solutions of linearized gravity on the Kerr exterior admit non-radiating modes, i.e. non-trivial time-independent solutions. These are closely related to conserved charges. In this paper we discuss the non-radiating modes for linearized gravity, which may be seen to correspond to the Poincare Lie-algebra. The 2-dimensional isometry group of Kerr corresponds to a 2-parameter family of gauge-invariant non-radiating modes representing infinitesimal perturbations of mass and azimuthal angular momentum. We calculate the linearized mass charge in terms of linearized Newman-Penrose scalars.

  7. Small amplitude variable charge dust Bernstein-Greene-Kruskal double layers

    Energy Technology Data Exchange (ETDEWEB)

    Amour, Rabia [Plasma Physics Group, Theoretical Physics Laboratory, Faculty of Sciences - Physics, U.S.T.H.B, Bab-Ezzouar, B.P. 32, El Alia, Algiers 16111 (Algeria); Tribeche, Mouloud [Plasma Physics Group, Theoretical Physics Laboratory, Faculty of Sciences - Physics, U.S.T.H.B, Bab-Ezzouar, B.P. 32, El Alia, Algiers 16111 (Algeria)], E-mail: mouloud-tribeche@lycos.com

    2009-05-11

    A first theoretical attempt is made to investigate small amplitude, variable charge dust Bernstein-Greene-Kruskal (BGK) double layers (DLs). The nature of the dust BGK-DLs (compressive or rarefactive), their strength and thickness depend sensitively on the net negative charge residing on the grain surface, the dust grain dynamics and, more interestingly, on the ion-to-electron temperatures ratio.

  8. Physiological Effects of Strength Training and Various Strength Training Devices.

    Science.gov (United States)

    Wilmore, Jack H.

    Current knowledge in the area of muscle physiology is a basis for a discussion on strength training programs. It is now recognized that the expression of strength is related to, but not dependent upon, the size of the muscle and is probably more related to the ability to recruit more muscle fibers in the contraction, or to better synchronize their…

  9. Overview to Strength Development and Strength Trainings in Children

    Directory of Open Access Journals (Sweden)

    Mesut Hekim

    2015-08-01

    Full Text Available There are some important phases within psychomotor development process in children. Periods of movements related to sport appear in this phases. In this phase which contains 7-12 age period in children, a significant increment occurs in the physical and motoric development levels of children. Physical and motoric developments are supported by directing children in this age group to sport. In a plenty of studies, it was stated that participating to sports in children supports motoric features and physical development. Strength is one of the most important motoric features which develop via participating to sports. Children strength development is effected at positive direction by adaptation exercise made to support strength development. Psychomotor development basis are considered to obtain the best efficiency from workouts aimed strength development in children and to remove risks to be generate any injury/disability. In this research, strength development, contributions of participating in sports to strength development, strength training in children and children responses to strength training were all emphasized.

  10. Airborne field strength monitoring

    Directory of Open Access Journals (Sweden)

    J. Bredemeyer

    2007-06-01

    Full Text Available In civil and military aviation, ground based navigation aids (NAVAIDS are still crucial for flight guidance even though the acceptance of satellite based systems (GNSS increases. Part of the calibration process for NAVAIDS (ILS, DME, VOR is to perform a flight inspection according to specified methods as stated in a document (DOC8071, 2000 by the International Civil Aviation Organization (ICAO. One major task is to determine the coverage, or, in other words, the true signal-in-space field strength of a ground transmitter. This has always been a challenge to flight inspection up to now, since, especially in the L-band (DME, 1GHz, the antenna installed performance was known with an uncertainty of 10 dB or even more. In order to meet ICAO's required accuracy of ±3 dB it is necessary to have a precise 3-D antenna factor of the receiving antenna operating on the airborne platform including all losses and impedance mismatching. Introducing precise, effective antenna factors to flight inspection to achieve the required accuracy is new and not published in relevant papers yet. The authors try to establish a new balanced procedure between simulation and validation by airborne and ground measurements. This involves the interpretation of measured scattering parameters gained both on the ground and airborne in comparison with numerical results obtained by the multilevel fast multipole algorithm (MLFMA accelerated method of moments (MoM using a complex geometric model of the aircraft. First results will be presented in this paper.

  11. Mortality Risk of Manufacturing Companies in Guangzhou based on Density Dependence Model%基于密度依赖模型的广州制造业企业死亡风险研究

    Institute of Scientific and Technical Information of China (English)

    王婵; 彭璧玉; 陈有华

    2014-01-01

    分析在同一个产业环境中不同组织形式的演化特征,概括其竞争和协作关系,判断这些关系对制造业中组织演化的影响,在此基础上提出有利于广州制造业持续发展的调控对策和建议。利用种群密度依赖原理、时变变量Cox模型分析广州制造业企业死亡风险,结果表明:(1)2000-2012年期间,广州制造业的种群密度与组织死亡风险呈正向的关系;(2)组织年龄与组织死亡风险呈负向的关系,且组织年龄可以抑制种群密度对组织死亡的影响;(3)在相同的组织年龄水平下多元化企业面临的死亡风险大于专一型企业的死亡风险,并且随着组织年龄的增大,两者的死亡风险差距逐渐扩大;(4)种群密度对外资企业死亡风险的影响大于对内资企业死亡风险的影响。但外资企业一旦存活,随之组织年龄的增大,其死亡风险跟内资企业面临的死亡风险基本相同;(5)种群密度对非劳动密集型企业死亡风险的影响大于对劳动密集型企业的死亡风险。%This paper analyzes the evolution characteristics of different forms in the same industry environment , summarizes the competition and collaboration relationships between them , and determines the impact of these rela-tionships on organizational evolution in manufacturing .Then we propose countermeasures and suggestions which are conducive to the sustainable development of Guangzhou's manufacturing industry .By using the population density dependency theory of organizational ecology and time-varying variables Cox model , the basic conclusions are a-chieved:( 1 ) From 2000 to 2012 , population density of Guangzhou manufacturing industry was positively related to the risk of the population's death.(2) Organization's age has negative relationship with the risk of the population's death and inhibits the effect of the population density on tissue death .(3) In the same age

  12. Associated single photons and doubly-charged scalars at linear - - colliders

    Indian Academy of Sciences (India)

    Biswarup Mukhopadhyaya; Santosh Kumar Rai

    2007-11-01

    Doubly-charged scalars, predicted in many models having exotic Higgs representations, can in general have lepton-number violating (LFV) couplings. We show that by using an associated monoenergetic final state photon seen at a future linear - - collider, we can have a clear and distinct signature for a doubly-charged resonance. The strength of the = 2 coupling can also be probed quite effectively as a function of the recoil mass of the doubly-charged scalar.

  13. Response of Charged Particles in a Storage Ring to Gravitational Waves

    Institute of Scientific and Technical Information of China (English)

    DONGDong; HUANGChao-Guang

    2003-01-01

    The influence of gravitational waves on the charged particles in a storage ring is studied. It shows that the gravitational waves might be directly detected by monitoring the motion of charged particles in a storage ring. The angular velocity of the charged particles is continually adjustable by changing the initial energy of particles and the strength of the magnetic field. This feature is very useful for finding the gravitational waves with different frequencies.

  14. Charged particle beams

    CERN Document Server

    Humphries, Stanley

    2013-01-01

    Detailed enough for a text and sufficiently comprehensive for a reference, this volume addresses topics vital to understanding high-power accelerators and high-brightness-charged particle beams. Subjects include stochastic cooling, high-brightness injectors, and the free electron laser. Humphries provides students with the critical skills necessary for the problem-solving insights unique to collective physics problems. 1990 edition.

  15. Threshold Stress Intensity of Hydrogen-Induced Cracking and Stress Corrosion Cracking of High Strength Steel

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The threshold stress intensity of stress corrosion cracking (SCC) for 40CrMo steel in 3.5 % NaCl solution decreased exponentially with the increase of yield strength. The threshold stress intensity of hydrogen-induced cracking during dynamical charging for 40CrMo steel decreased linearly with the logarithm of the concentration of diffusible hydrogen. This equation was also applicable to SCC of high strength steel in aqueous solution. The critical hydrogen enrichment concentration necessary for SCC of high strength steel in water decreased exponentially with the increase of yield strength. Based on the results, the relationship between KISCC and σys could be deduced.

  16. Simulations of charge transport in organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Vehoff, Thorsten

    2010-05-05

    features: first, the shifted cofacial alignment of its molecules, and second, the high center of mass vibrational frequency. In comparsion to SCD, only KMC based on Marcus rates is capable of describing neighbors with low coupling and of taking static disorder into account three-dimensionally. SCD, despite its one-dimensionality, is valuable for crystals with strong coupling and little disorder. It also allows correct treatment of dynamical effects, such as intermolecular vibrations of the molecules. Rate equations are incapable of this, because simulations are performed on static snapshots. We have thus shown strengths and weaknesses of two state of the art models used to study charge transport in organic compounds, partially developed a program to compute and visualize transfer integral distributions and other charge transport properties, and found structure-mobility relations for several promising organic semiconductors. (orig.)

  17. Role of the momentum transfer in the quenching of the Gamow-Teller strength

    Energy Technology Data Exchange (ETDEWEB)

    Marketin, Tomislav [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Physics Department, Faculty of Science, University of Zagreb (Croatia); Martinez-Pinedo, Gabriel [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Paar, Nils; Vretenar, Dario [Physics Department, Faculty of Science, University of Zagreb (Croatia)

    2012-07-01

    A fully consistent calculation of the Gamow-Teller strength is presented, based on a microscopic theoretical framework. Nuclear ground state is determined using the relativistic Hartree-Bogolyubov (RHB) model with density dependent meson-nucleon coupling constants, and transition rates are calculated via proton-neutron relativistic quasiparticle RPA using the same interaction as in the RHB equations. The (p,n) probe has a similar spin-isospin operator structure to the Gamow-Teller (GT) operator. However, they become comparable only if the GT cross section is measured at a very small momentum transfer q. At higher momentum transfer the isovector spin monopole (IVSM) mode occurs, with the r{sup 2}{sigma}{tau} transition operator. Unlike the Gamow-Teller operator which excites only the 0{Dirac_h}{omega} transitions, the isovector spin monopole operator can also excite 2{Dirac_h}{omega} transitions and can change the strength distribution at high excitation energies. We explore the strength beyond the resonance, examine the effect of momentum transfer on the total strength and compare the results with recent measurements.

  18. Ultimate Strength, Committee III.1

    DEFF Research Database (Denmark)

    Simonsen, Bo Cerup; Estefan, S.; Fasano, E.;

    2003-01-01

    Concern for the ductile of ships and offshore structures and their structural components under ultimate conditions. Attention shall be given to the influence of fabrication imperfections and inservice damage and degradation on reserve strength. Uncertainties in strength models for design shall...

  19. Loading Conditions and Longitudinal Strength

    DEFF Research Database (Denmark)

    Sørensen, Herman

    1995-01-01

    Methods for the calculation of the lightweight of the ship.Loading conditions satisfying draught, trim and intact stability requirements and analysis of the corresponding stillwater longitudinal strength.......Methods for the calculation of the lightweight of the ship.Loading conditions satisfying draught, trim and intact stability requirements and analysis of the corresponding stillwater longitudinal strength....

  20. The Charge State of Polycyclic Aromatic Hydrocarbons Across Reflection Nebulae: PAH Charge Balance and Calibration

    Science.gov (United States)

    Boersma, C.; Bregman, J.; Allamandola, L. J.

    2016-11-01

    Low-resolution Spitzer spectral map data (>1700 spectra) of ten reflection nebulae (RNe) fields are analyzed using the data and tools available through the NASA Ames PAH IR Spectroscopic Database. The PAH emission is broken down into PAH charge state using a database fitting approach. Here, the physics of the PAH emission process is taken into account and uses target appropriate parameters, e.g., a stellar radiation model for the exciting star. The breakdown results are combined with results derived using the traditional PAH band strength approach, which interprets particular PAH band strength ratios as proxies for the PAH charge state, e.g., the 6.2/11.2 μm PAH band strength ratio. These are successfully calibrated against their database equivalent; the PAH ionized fraction (f i ). The PAH ionized fraction is converted into the PAH ionization parameter, which relates the PAH ionized fraction to the strength of the radiation field, gas temperature and electron density. The behavior of the 12.7 μm PAH band is evaluated as a tracer for PAH ionization and erosion. The plot of the 8.6 versus 11.2 μm PAH band strength for the northwest photo-dominated region (PDR) in NGC 7023 is shown to be a robust diagnostic template for the PAH ionized fraction. Remarkably, most of the other RNe fall within the limits set by NGC 7023. Finally, PAH spectroscopic templates are constructed and verified as principal components. Template spectra derived from NGC 7023 and NGC 2023 compare extremely well with each other, with those derived for NGC 7023 successfully reproducing the PAH emission observed from NGC 2023.

  1. Remolded Undrained Strength of Soils

    Institute of Scientific and Technical Information of China (English)

    HONG Zhen-shun(洪振舜); LIU Han-long(刘汉龙); NEGAMI Takehito

    2003-01-01

    Extensive data of undrained shear strength for various remolded soils are compiled to normalize the remolded undrained strength. Remolded soils have a wide spectrum of liquid limits ranging from 25% to 412%. It is found that the remolded undrained strength is a function of water content and liquid limit. Furthermore, a simple index designated as normalized water content w* is introduced for normalizing remolded undrained strength for various soils. The normalized water content w* is the ratio of water content to liquid limit. The relationship between the remolded undrained strength and the normalized water content can be expressed by a simple equation. The new simple equation is not only valuable theoretically for helping in assessing the in-situ mechanical behavior, but also useful to ocean engineering practice.

  2. STRENGTH OF NANOMODIFIED HIGH-STRENGTH LIGHTWEIGHT CONCRETES

    Directory of Open Access Journals (Sweden)

    NOZEMTСEV Alexandr Sergeevich

    2013-02-01

    Full Text Available The paper presents the results of research aimed at development of nanomodified high-strength lightweight concrete for construction. The developed concretes are of low average density and high ultimate compressive strength. It is shown that to produce this type of concrete one need to use hollow glass and aluminosilicate microspheres. To increase the durability of adhesion between cement stone and fine filler the authors offer to use complex nanodimensinal modifier based on iron hydroxide sol and silica sol as a surface nanomodifier for hollow microspheres. It is hypothesized that the proposed modifier has complex effect on the activity of the cement hydration and, at the same time increases bond strength between filler and cement-mineral matrix. The compositions for energy-efficient nanomodified high-strength lightweight concrete which density is 1300…1500 kg/m³ and compressive strength is 40…65 MPa have been developed. The approaches to the design of high-strength lightweight concrete with density of less than 2000 kg/m³ are formulated. It is noted that the proposed concretes possess dense homogeneous structure and moderate mobility. Thus, they allow processing by vibration during production. The economic and practical implications for realization of high-strength lightweight concrete in industrial production have been justified.

  3. Optimization of BEV Charging Strategy

    Science.gov (United States)

    Ji, Wei

    This paper presents different approaches to optimize fast charging and workplace charging strategy of battery electric vehicle (BEV) drivers. For the fast charging analysis, a rule-based model was built to simulate BEV charging behavior. Monte Carlo analysis was performed to explore to the potential range of congestion at fast charging stations which could be more than four hours at the most crowded stations. Genetic algorithm was performed to explore the theoretical minimum waiting time at fast charging stations, and it can decrease the waiting time at the most crowded stations to be shorter than one hour. A deterministic approach was proposed as a feasible suggestion that people should consider to take fast charging when the state of charge is approaching 40 miles. This suggestion is hoped to help to minimize potential congestion at fast charging stations. For the workplace charging analysis, scenario analysis was performed to simulate temporal distribution of charging demand under different workplace charging strategies. It was found that if BEV drivers charge as much as possible and as late as possible at workplace, it could increase the utility of solar-generated electricity while relieve grid stress of extra intensive electricity demand at night caused by charging electric vehicles at home.

  4. Extended Holstein polaron model for charge transfer in dry DNA

    Institute of Scientific and Technical Information of China (English)

    Liu Tao; Wang Yi; Wang Ke-Lin

    2007-01-01

    The variational method is applied to the study of charge transfer in dry DNA by using an extended Holstein small polaron model in two cases: the site-dependent finite-chain discrete case and the site-independent continuous one. The treatments in the two cases are proven to be consistent in theory and calculation. Discrete and continuous treatments of Holstein model both can yield a nonlinear equation to describe the charge migration in an actual long-range DNA chain.Our theoretical results of binding energy Eb, probability amplitude of charge carrier φ and the relation between energy and charge-lattice coupling strength are in accordance with the available experimental results and recent theoretical calculations.

  5. Sample Preconcentration in Nanochannels with Tunable Surface Charge

    Science.gov (United States)

    Eden, Alexander; McCallum, Christopher; Storey, Brian; Meinhart, Carl; Pennathur, Sumita

    2016-11-01

    We present a novel method for field amplified sample stacking (FASS) and focusing in nanochannels by taking advantage of the nonuniform ion distributions produced by thick electric double layers (EDLs) in channels with heterogeneous surface charge. This is accomplished by applying a voltage bias to a gate electrode embedded within the channel wall, tuning the surface charge in a region of the channel and significantly altering the charge density and ionic strength in that region relative to the rest of the channel. The resulting nonuniform electromigration fluxes in the different regions serve to stack charged sample ions at an interface where a step change in zeta potential occurs, providing enhancement ratios superior to those exhibited in traditional microchannel FASS. Numerical simulations are performed to demonstrate the phenomenon, and resulting velocity and salt concentration profiles show good agreement with analytical results.

  6. Coacervation in Symmetric Mixtures of Oppositely Charged Rodlike Polyelectrolytes

    Science.gov (United States)

    Kumar, Rajeev; Fredrickson, Glenn

    2010-03-01

    Phase separation in the salt-free symmetric mixtures of oppositely charged rodlike polyelectrolytes is studied using quasi-analytical calculations. Stability analyses for the isotropic-isotropic and the isotropic-nematic phase transitions in the symmetric mixtures are carried out. It is shown that electrostatics favor nematic ordering. Also, the coexistence curves for the symmetric mixtures are computed, and the effects of the linear charge density and the electrostatic interaction strength on the phase boundaries are studied. It is found that the counterions are uniformly distributed in the coexisting phases for low electrostatic interaction strengths characterized by the linear charge density of the polyelectrolytes and the Bjerrum's length. However, the counterions also phase separate along with the rodlike polyelectrolytes with an increase in the electrostatic interaction strength. It is shown that the number density of the counterions is higher in the concentrated (or coacervate) phase than in the dilute (or supernatant) phase. In contrast to the rodlike mixtures, flexible polyelectrolyte mixtures can undergo only isotropic-isotropic phase separation. A comparison of the coexistence curves for the weakly charged rodlike with the flexible polyelectrolyte mixtures reveals that the electrostatic driving force for the isotropic-isotropic phase separation is stronger in the flexible mixtures.

  7. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.

    2014-10-09

    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  8. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field.

    Science.gov (United States)

    Forbes, Thomas P; Degertekin, F Levent; Fedorov, Andrei G

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

  9. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

    Science.gov (United States)

    Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing. PMID:21301636

  10. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

    Science.gov (United States)

    Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

  11. Existence of magnetic charge

    Science.gov (United States)

    Akers, David

    1990-10-01

    A status report is presented on the existence of quarks carrying the Dirac unit of magnetic charge g = (137/2) e. The Paschen-Back effect in dyonium is discussed. From the dyonium model, Akers predicted the existence of a new η meson at 1814 MeV with I G(JPC) = 0+(0-+). Experimental evidence now confirms the existence of the meson resonance.

  12. Extremally charged line

    CERN Document Server

    Ryzner, Jiří

    2016-01-01

    We investigate the properties of a static, cylindrically symmetric Majumdar-Papapetrou-type solution of Einstein-Maxwell equations. We locate its singularities, establish its algebraic type, find its asymptotic properties and weak-field limit, study the structure of electrogeodesics, and determine the mass and charge of its sources. We provide an interpretation of the spacetime and discuss the parameter appearing in the metric.

  13. Charged Lifshitz Black Holes

    OpenAIRE

    Dehghani, M. H.; Pourhasan, R.; Mann, R. B.

    2011-01-01

    We investigate modifications of the Lifshitz black hole solutions due to the presence of Maxwell charge in higher dimensions for arbitrary $z$ and any topology. We find that the behaviour of large black holes is insensitive to the topology of the solutions, whereas for small black holes significant differences emerge. We generalize a relation previously obtained for neutral Lifshitz black branes, and study more generally the thermodynamic relationship between energy, entropy, and chemical pot...

  14. Freezing of charged colloids in slit pores.

    Science.gov (United States)

    Grandner, Stefan; Klapp, Sabine H L

    2008-12-28

    Using Monte Carlo simulations in the grand canonical and isobaric ensembles we investigate freezing phenomena in a charged colloidal suspension confined to narrow slit pores. Our model involves only the macroions which interact via a Derjaguin-Landau-Verwey-Overbeek (DLVO) potential supplemented by a soft-sphere potential. We focus on DLVO parameters typical for moderately charged silica particles (with charges Z approximately 35) in solvents of low ionic strengths. The corresponding DLVO interactions are too weak to drive a (bulk) freezing transition. Nevertheless, for sufficiently small surface separations L(z) the confined systems display not only layering but also significant in-plane crystalline order at chemical potentials where the bulk system is a globally stable fluid (capillary freezing). At confinement conditions related to two-layer systems the observed in-plane structures are consistent with those detected in ground state calculations for perfect Yukawa bilayers [R. Messina and H. Lowen, Phys. Rev. Lett. 91, 146101 (2003)]. Here we additionally observe (at fixed L(z)) a compression-induced first-order phase transition from a two-layer to a three-layer system with different in-plane structure, in agreement with previous findings for pure hard spheres.

  15. Induced-Charge Electro-Osmosis

    CERN Document Server

    Squires, T M; Squires, Todd M.; Bazant, Martin Z.

    2003-01-01

    The general phenomenon of `induced-charge electro-osmosis' (ICEO) is described -- the nonlinear electro-osmotic slip caused by an applied field acting on induced ionic charge in the vicinity of a polarizable surface. A simple physical picture of the basic phenomenon is presented, and the ICEO flow around conducting cylinders and spheres in steady (DC), oscillitory (AC), and suddenly-applied electric fields is calculated, providing perhaps the simplest and clearest example of a non-equilibrium electrokinetic phenomenon. It is shown that ICEO slip velocities generally vary like $u_s \\propto E_0^2 a$ in uniform fields, where $E_0$ is the applied field strength and $a$ is a geometrical length scale, and are set up on a time scale $\\tau_c = \\lambda_D a/D$, where $\\lambda_D$ is the screening length and $D$ the diffusion constant of the electrolytic ions. A variety of microfludic flows results for conducting objects of either fixed total charge or fixed potential. The effect of a dielectric coating upon ICEO flows i...

  16. Distributed charging of electrical assets

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Soumyadip; Phan, Dung; Sharma, Mayank; Wu, Chai Wah; Xiong, Jinjun

    2016-02-16

    The present disclosure relates generally to the field of distributed charging of electrical assets. In various examples, distributed charging of electrical assets may be implemented in the form of systems, methods and/or algorithms.

  17. Modular Battery Charge Controller

    Science.gov (United States)

    Button, Robert; Gonzalez, Marcelo

    2009-01-01

    A new approach to masterless, distributed, digital-charge control for batteries requiring charge control has been developed and implemented. This approach is required in battery chemistries that need cell-level charge control for safety and is characterized by the use of one controller per cell, resulting in redundant sensors for critical components, such as voltage, temperature, and current. The charge controllers in a given battery interact in a masterless fashion for the purpose of cell balancing, charge control, and state-of-charge estimation. This makes the battery system invariably fault-tolerant. The solution to the single-fault failure, due to the use of a single charge controller (CC), was solved by implementing one CC per cell and linking them via an isolated communication bus [e.g., controller area network (CAN)] in a masterless fashion so that the failure of one or more CCs will not impact the remaining functional CCs. Each micro-controller-based CC digitizes the cell voltage (V(sub cell)), two cell temperatures, and the voltage across the switch (V); the latter variable is used in conjunction with V(sub cell) to estimate the bypass current for a given bypass resistor. Furthermore, CC1 digitizes the battery current (I1) and battery voltage (V(sub batt) and CC5 digitizes a second battery current (I2). As a result, redundant readings are taken for temperature, battery current, and battery voltage through the summation of the individual cell voltages given that each CC knows the voltage of the other cells. For the purpose of cell balancing, each CC periodically and independently transmits its cell voltage and stores the received cell voltage of the other cells in an array. The position in the array depends on the identifier (ID) of the transmitting CC. After eight cell voltage receptions, the array is checked to see if one or more cells did not transmit. If one or more transmissions are missing, the missing cell(s) is (are) eliminated from cell

  18. Human fibrinogen adsorption on positively charged latex particles.

    Science.gov (United States)

    Zeliszewska, Paulina; Bratek-Skicki, Anna; Adamczyk, Zbigniew; Cieśla, Michał

    2014-09-23

    Fibrinogen (Fb) adsorption on positively charged latex particles (average diameter of 800 nm) was studied using the microelectrophoretic and the concentration depletion methods based on AFM imaging. Monolayers on latex were adsorbed from diluted bulk solutions at pH 7.4 and an ionic strength in the range of 10(-3) to 0.15 M where fibrinogen molecules exhibited an average negative charge. The electrophoretic mobility of the latex after controlled fibrinogen adsorption was systematically measured. A monotonic decrease in the electrophoretic mobility of fibrinogen-covered latex was observed for all ionic strengths. The results of these experiments were interpreted according to the three-dimensional electrokinetic model. It was also determined using the concentration depletion method that fibrinogen adsorption was irreversible and the maximum coverage was equal to 0.6 mg m(-2) for ionic strength 10(-3) M and 1.3 mg m(-2) for ionic strength 0.15 M. The increase of the maximum coverage was confirmed by theoretical modeling based on the random sequential adsorption approach. Paradoxically, the maximum coverage of fibrinogen on positively charged latex particles was more than two times lower than the maximum coverage obtained for negative latex particles (3.2 mg m(-2)) at pH 7.4 and ionic strength of 0.15 M. This was interpreted as a result of the side-on adsorption of fibrinogen molecules with their negatively charged core attached to the positively charged latex surface. The stability and acid base properties of fibrinogen monolayers on latex were also determined in pH cycling experiments where it was observed that there were no irreversible conformational changes in the fibrinogen monolayers. Additionally, the zeta potential of monolayers was more positive than the zeta potential of fibrinogen in the bulk, which proves a heterogeneous charge distribution. These experimental data reveal a new, side-on adsorption mechanism of fibrinogen on positively charged surfaces and

  19. Banking Bank Charge Debates Continue

    Institute of Scientific and Technical Information of China (English)

    WANG PEI

    2006-01-01

    @@ The saying, "There's no such thing as a free lunch" is one that can be applied to the charges increasingly being imposed on savers by Chinese banks.Ranging from managementfees for small deposit accounts to charges for withdrawals of large amounts of cash, from ATM cross-bank withdrawal charges to annual fees for bank payment cards, charges by banks are becoming a unstoppable trend. But it is not a trend the general public is so keen to accept.

  20. Notch Charge-Coupled Devices

    Science.gov (United States)

    Janesick, James

    1992-01-01

    Notch charge-coupled devices are imaging arrays of photodetectors designed to exhibit high charge-transfer efficiencies necessary for operation in ultra-large array, and less vulnerable to degradation by energetic protons, neutrons, and electrons. Main channel of horizontal register includes deep narrow inner channel (notch). Small packets of charge remain confined to notch. Larger packets spill into rest of channel; transferred in usual way. Degradation of charge-transfer efficiency by energetic particles reduced.

  1. Muscle Strength and Poststroke Hemiplegia

    DEFF Research Database (Denmark)

    Kristensen, Otto H; Stenager, Egon; Dalgas, Ulrik

    2017-01-01

    OBJECTIVES: To systematically review (1) psychometric properties of criterion isokinetic dynamometry testing of muscle strength in persons with poststroke hemiplegia (PPSH); and (2) literature that compares muscle strength in patients poststroke with that in healthy controls assessed by criterion...... isokinetic dynamometry. DATA SOURCES: A systematic literature search of 7 databases was performed. STUDY SELECTION: Included studies (1) enrolled participants with definite poststroke hemiplegia according to defined criteria; (2) assessed muscle strength or power by criterion isokinetic dynamometry; (3) had...... undergone peer review; and (4) were available in English or Danish. DATA EXTRACTION: The psychometric properties of isokinetic dynamometry were reviewed with respect to reliability, validity, and responsiveness. Furthermore, comparisons of strength between paretic, nonparetic, and comparable healthy muscles...

  2. Predictions of nuclear charge radii

    Science.gov (United States)

    Bao, M.; Lu, Y.; Zhao, Y. M.; Arima, A.

    2016-12-01

    The nuclear charge radius is a fundamental property of an atomic nucleus. In this article we study the predictive power of empirical relations for experimental nuclear charge radii of neighboring nuclei and predict the unknown charge radii of 1085 nuclei based on the experimental CR2013 database within an uncertainty of 0.03 fm.

  3. Tools for charged Higgs bosons

    Energy Technology Data Exchange (ETDEWEB)

    Staal, Oscar

    2010-12-15

    We review the status of publicly available software tools applicable to charged Higgs physics. A selection of codes are highlighted in more detail, focusing on new developments that have taken place since the previous charged Higgs workshop in 2008. We conclude that phenomenologists now have the tools ready to face the LHC data. A new web page collecting charged Higgs resources is presented. (orig.)

  4. Improving Charging-Breeding Simulations with Space-Charge Effects

    Science.gov (United States)

    Bilek, Ryan; Kwiatkowski, Ania; Steinbrügge, René

    2016-09-01

    Rare-isotope-beam facilities use Highly Charged Ions (HCI) for accelerators accelerating heavy ions and to improve measurement precision and resolving power of certain experiments. An Electron Beam Ion Trap (EBIT) is able to create HCI through successive electron impact, charge breeding trapped ions into higher charge states. CBSIM was created to calculate successive charge breeding with an EBIT. It was augmented by transferring it into an object-oriented programming language, including additional elements, improving ion-ion collision factors, and exploring the overlap of the electron beam with the ions. The calculation is enhanced with the effects of residual background gas by computing the space charge due to charge breeding. The program assimilates background species, ionizes and charge breeds them alongside the element being studied, and allows them to interact with the desired species through charge exchange, giving fairer overview of realistic charge breeding. Calculations of charge breeding will be shown for realistic experimental conditions. We reexamined the implementation of ionization energies, cross sections, and ion-ion interactions when charge breeding.

  5. Charge dynamic characteristics in corona-charged polytetrafluoroethylene film electrets

    Institute of Scientific and Technical Information of China (English)

    陈钢进; 肖慧明; 朱春凤

    2004-01-01

    In this work, the charge dynamics characteristics of injection, transport and decay in porous and non-porous polytetrafluoroethylene (PTFE) film electrets were investigated by means of corona charging, isothermal and thermal stimulating surface-potential decay measurements. The results showed that the initial surface potential, whether positively or negatively charging, is much higher in non-porous PTFE than in porous PTFE. For porous film the value of initial sur-face potentials increases with increase of film thickness. Higher charging temperature can remarkably improve charge stability. The charge dynamics are correlated to materials microstructure according to their scanning electron micrographs.For non-porous PTFE films, polarizability change of C-F bonds is the main origin of electret charges; but for porous PTFE film a large number of bulk and interface type traps are expected because of the greater area of interface and higher crys-tallinity.

  6. Charge dynamic characteristics in corona-charged polytetrafluoroethylene film electrets

    Institute of Scientific and Technical Information of China (English)

    陈钢进; 肖慧明; 朱春凤

    2004-01-01

    In this work, the charge dynamics characteristics of injection, transport and decay in porous and non-porous polytetrafluoroethylene (PTFE) film electrets were investigated by means of corona charging, isothermal and thermal stimulating surface-potential decay measurements. The results showed that the initial surface potential, whether positively or negatively charging, is much higher in non-porous PTFE than in porous PTFE. For porous film the value of initial surface potentials increases with increase of film thickness. Higher charging temperature can remarkably improve charge stability. The charge dynamics are correlated to materials microstructure according to their scanning electron micrographs.For non-porous PTFE films, polarizability change of C-F bonds is the main origin of electret charges; but for porous PTFE film a large number of bulk and interface type traps are expected because of the greater area of interface and higher crystallinity.

  7. Neutrality point of graphene with coplanar charged impurities.

    Science.gov (United States)

    Fogler, Michael M

    2009-12-04

    The ground state and the transport properties of graphene subject to the potential of in-plane charged impurities are studied. The screening of the impurity potential is shown to be nonlinear, producing a fractal structure of electron and hole puddles. Statistical properties of this density distribution as well as the charge compressibility of the system are calculated in the leading-log approximation. The conductivity depends logarithmically on alpha, the dimensionless strength of the Coulomb interaction. The theory is asymptotically exact when alpha is small, which is the case for graphene on a substrate with a high dielectric constant.

  8. Charge transport in single crystal organic semiconductors

    Science.gov (United States)

    Xie, Wei

    high-quality single crystals and exhibit large ambipolar mobilities. Nevertheless, a gap remains between the theory-predicted properties and this preliminary result, which itself is another fundamental challenge. This is further addressed by appropriate device optimization, and in particular, contact engineering approach to improve the charge injection efficiencies. The outcome is not only the achievement of new record ambipolar mobilities in one of the derivatives, namely, 4.8 cm2V-1s-1 for holes and 4.2 cm2V-1s-1 for electrons, but also provides a comprehensive and rational pathway towards the realization of high-performance organic semiconductors. Efforts to achieve high mobility in other organic single crystals are also presented. The second challenge is tuning the transition of electronic ground states, i.e., semiconducting, metallic and superconducting, in organic single crystals. Despite an active research area since four decades ago, we aim to employ the electrostatic approach instead of chemical doping for reversible and systematic control of charge densities within the same crystal. The key material in this study is the high-capacitance electrolyte, such as ionic liquids (ILs), whose specific capacitance reaches ~ μF/cm2, thus allowing accumulation of charge carrier above 1013 cm-2 when novel transport phenomena, such as insulator-metal transition and superconductivity, are likely to occur. This thesis addresses the electrical characterization, device physics and transport physics in electrolyte-gated single crystals, in the device architecture known as the electrical double layer transistor (EDLT). A detailed characterization scheme is first demonstrated for accurate determination of several key parameters, e.g., carrier mobility and charge density, in organic EDLTs. Further studies, combining both experiments and theories, are devoted to understanding the unusual charge density dependent channel conductivity and gate-to-channel capacitance behaviors. In

  9. Charge sniffer for electrostatics demonstrations

    Science.gov (United States)

    Dinca, Mihai P.

    2011-02-01

    An electronic electroscope with a special design for demonstrations and experiments on static electricity is described. It operates as an electric charge sniffer by detecting slightly charged objects when they are brought to the front of its sensing electrode. The sniffer has the advantage of combining high directional sensitivity with a logarithmic bar display. It allows for the identification of electric charge polarity during charge separation by friction, peeling, electrostatic induction, batteries, or secondary coils of power transformers. Other experiments in electrostatics, such as observing the electric field of an oscillating dipole and the distance dependence of the electric field generated by simple charge configurations, are also described.

  10. Antiproton charge radius

    Science.gov (United States)

    Crivelli, P.; Cooke, D.; Heiss, M. W.

    2016-09-01

    The upcoming operation of the extra low energy antiprotons ring at CERN, the upgrade of the antiproton decelerator (AD), and the installation in the AD hall of an intense slow positron beam with an expected flux of 1 08 e+ /s will open the possibility for new experiments with antihydrogen (H ¯). Here we propose a scheme to measure the Lamb shift of H ¯. For four months of data taking, we anticipate an uncertainty of 100 ppm. This will provide a test of C P T and the first determination of the antiproton charge radius at the level of 10%.

  11. Infrared study of charge injection in organic field-effect transistors

    Science.gov (United States)

    Li, Zhiqiang

    2008-03-01

    We present a systematic infrared (IR) spectroscopic study of charge injection in organic field-effect transistors (FET). These experiments have revealed new unexpected aspects of both polymers and molecular crystals. IR spectromicroscopy was employed to image the charges in poly(3-hexylthiophene) (P3HT) FETs. The charge density profile in the conducting channel uncovers a density-dependent mobility in P3HT due to disorder effects. Our IR studies of single crystal rubrene based FETs show that charge transport in these devices at room temperature is governed by light quasiparticles in molecular orbital bands. This result is at variance with the common beliefs of polaron formation in molecular solids. The above experiments have demonstrated the unique potential of IR spectroscopy for investigating physical phenomena at the nanoscale occurring at the semiconductor-insulator interface in FET devices. This work is in collaboration with G. M. Wang, D. Moses, A. J. Heeger (UCSB), V. Podzorov, M.E. Gershenson (Rutgers), Z. Hao, M. C. Martin (ALS), N. Sai, A. D. Meyertholen, M. M. Fogler, M. Di Ventra and D. N. Basov (UCSD).

  12. Price Based Electric Vehicle Charging

    DEFF Research Database (Denmark)

    Mahat, Pukar; Handl, Martin; Kanstrup, Kenneth

    2012-01-01

    It is expected that a lot of the new light vehicles in the future will be electrical vehicles (EV). The storage capacity of these EVs has the potential to complement renewable energy resources and mitigate its intermittency. However, EV charging may have negative impact on the power grid. This pa......It is expected that a lot of the new light vehicles in the future will be electrical vehicles (EV). The storage capacity of these EVs has the potential to complement renewable energy resources and mitigate its intermittency. However, EV charging may have negative impact on the power grid....... This paper investigates the impact on a Danish distribution system when the EV charging aims to reduce the charging cost by charging at the cheapest hours. Results show that the charging based on the price signal only will have adverse effect on the grid. The paper also proposes an alternate EV charging...

  13. Charged Galileon black holes

    Science.gov (United States)

    Babichev, Eugeny; Charmousis, Christos; Hassaine, Mokhtar

    2015-05-01

    We consider an Abelian gauge field coupled to a particular truncation of Horndeski theory. The Galileon field has translation symmetry and couples non minimally both to the metric and the gauge field. When the gauge-scalar coupling is zero the gauge field reduces to a standard Maxwell field. By taking into account the symmetries of the action, we construct charged black hole solutions. Allowing the scalar field to softly break symmetries of spacetime we construct black holes where the scalar field is regular on the black hole event horizon. Some of these solutions can be interpreted as the equivalent of Reissner-Nordstrom black holes of scalar tensor theories with a non trivial scalar field. A self tuning black hole solution found previously is extended to the presence of dyonic charge without affecting whatsoever the self tuning of a large positive cosmological constant. Finally, for a general shift invariant scalar tensor theory we demonstrate that the scalar field Ansatz and method we employ are mathematically compatible with the field equations. This opens up the possibility for novel searches of hairy black holes in a far more general setting of Horndeski theory.

  14. Charged Dust Aggregate Interactions

    Science.gov (United States)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  15. Charged Galileon black holes

    CERN Document Server

    Babichev, Eugeny; Hassaine, Mokhtar

    2015-01-01

    We consider an Abelian gauge field coupled to a particular truncation of Horndeski theory. The Galileon field has translation symmetry and couples non minimally both to the metric and the gauge field. When the gauge-scalar coupling is zero the gauge field reduces to a standard Maxwell field. By taking into account the symmetries of the action, we construct charged black hole solutions. Allowing the scalar field to softly break symmetries of spacetime we construct black holes where the scalar field is regular on the black hole event horizon. Some of these solutions can be interpreted as the equivalent of Reissner-Nordstrom black holes of scalar tensor theories with a non trivial scalar field. A self tuning black hole solution found previously is extended to the presence of dyonic charge without affecting whatsoever the self tuning of a large positive cosmological constant. Finally, for a general shift invariant scalar tensor theory we demonstrate that the scalar field Ansatz and method we employ are mathematic...

  16. Lifting strength in two-person teamwork.

    Science.gov (United States)

    Lee, Tzu-Hsien

    2016-01-01

    This study examined the effects of lifting range, hand-to-toe distance, and lifting direction on single-person lifting strengths and two-person teamwork lifting strengths. Six healthy males and seven healthy females participated in this study. Two-person teamwork lifting strengths were examined in both strength-matched and strength-unmatched groups. Our results showed that lifting strength significantly decreased with increasing lifting range or hand-to-toe distance. However, lifting strengths were not affected by lifting direction. Teamwork lifting strength did not conform to the law of additivity for both strength-matched and strength-unmatched groups. In general, teamwork lifting strength was dictated by the weaker of the two members, implying that weaker members might be exposed to a higher potential danger in teamwork exertions. To avoid such overexertion in teamwork, members with significantly different strength ability should not be assigned to the same team.

  17. Intramolecular resonance-assisted hydrogen bonds: A theoretical description by means of atomic charges and charge fluxes

    Science.gov (United States)

    Baranović, Goran

    2014-01-01

    The characterization of intramolecular H-bonds in terms of atomic charges and charge fluxes (at the B3LYP/cc-pVTZ level of theory) has been extended to the case of the so called resonance-assisted (RA) H-bonds. A quadratic correlation between the charge fluxes ϕH and the molecular IR absorption coefficients E that includes the entire family of the studied systems (31 of them) containing both intra- and intermolecular hydrogen bonds (O-H⋯O/N) confirmed the critical importance of the charge fluxes on the IR intensity enhancements. Since they reflect changing of the atomic charge distribution during the normal modes of vibrations, the dynamic nature of hydrogen bonding properties has been re-emphasized. The changes of the charge flux of the hydroxyl hydrogen in an RA intramolecular H-bond are between those for “free” OH bonds and the values calculated for intermolecular H-bonds. The transition “free” → intramolecular → intermolecular is gradual and therefore the hydrogen charge flux can be considered as practically sufficient to give quantitative measure to the intuitively obvious statement that “intramolecular H-bonding is somehow in between no H-bonding situation and intermolecular H-bonding” and thus provide a quantitative and yet simple parameterization of H-bond strength. In strictly planar molecules, the difference of the sums of charges of atoms participating in the 6-membered H-bond ring ΔΣ can serve as a measure of the charge delocalization after the H-bond is formed. The electronic charge is withdrawn from the group of six atoms when the H-bond is formed in nitrophenol (ΔΣ = -0.07), while the opposite is true (ΔΣ = +0.03) for 2-hydroxy benzylidene amine. The corresponding values of the geometrical resonance parameter Δ are 0.39 and 0.37, respectively, similar to those found for 2-hydroxy acetophenone and 2-hydroxy benzaldehyde. The extent of the π-electron delocalization as measured by the resonance parameter Δ does not follow

  18. Singularity in Gravitational Collapse of Plane Symmetric Charged Vaidya Spacetime

    CERN Document Server

    Sharif, M

    2010-01-01

    We study the final outcome of gravitational collapse resulting from the plane symmetric charged Vaidya spacetime. Using the field equations, we show that the weak energy condition is always satisfied by collapsing fluid. It is found that the singularity formed is naked. The strength of singularity is also investigated by using Nolan's method. This turns out to be a strong curvature singularity in Tipler's sense and hence provides a counter example to the cosmic censorship hypothesis.

  19. Charge Breeding of Radioactive Ions

    CERN Document Server

    Wenander, F J C

    2013-01-01

    Charge breeding is a technique to increase the charge state of ions, in many cases radioactive ions. The singly charged radioactive ions, produced in an isotope separator on-line facility, and extracted with a low kinetic energy of some tens of keV, are injected into a charge breeder, where the charge state is increased to Q. The transformed ions are either directed towards a dedicated experiment requiring highly charged ions, or post-accelerated to higher beam energies. In this paper the physics processes involved in the production of highly charged ions will be introduced, and the injection and extraction beam parameters of the charge breeder defined. A description of the three main charge-breeding methods is given, namely: electron stripping in gas jet or foil; external ion injection into an electron-beam ion source/trap (EBIS/T); and external ion injection into an electron cyclotron resonance ion source (ECRIS). In addition, some preparatory devices for charge breeding and practical beam delivery aspects ...

  20. Muscle strength in myasthenia gravis

    DEFF Research Database (Denmark)

    Cejvanovic, S; Vissing, J

    2014-01-01

    is related to disease duration or gender. The aim of this study was to quantify the strength of patients with MG and investigate whether it is related to disease duration. METHODS: Eight muscle groups were tested by manual muscle testing and with a hand-held dynamometer in 38 patients with generalized MG...... and 37 healthy age- and gender-matched controls. The disease duration was recorded and compared with strength measures. RESULTS: On average, muscle strength was decreased by 28% compared with controls (Pstrength measures in individual patients did not differ, suggesting that the muscle...... force reported was not subject to fatigue, but reflected fixed weakness. The male patients showed a greater reduction in muscle force in all eight muscle groups than women with MG (60% vs 77% of normal, Pstrength in shoulder abductors was most affected (51% vs 62...

  1. Strengths, weaknesses, opportunities and threats

    DEFF Research Database (Denmark)

    Bull, J. W.; Jobstvogt, N.; Böhnke-Henrichs, A.;

    2016-01-01

    environmental awareness. Threats include resistance to change, and difficulty with interdisciplinary collaboration. Consideration of SWOT themes suggested five strategic areas for developing and implementing ES.The ES concept could improve decision-making related to natural resource use, and interpretation...... facilitate interdisciplinary research, ensuring decision-making that supports sustainable development........ Such an assessment could form the basis for improving ES thinking, further embedding it into environmental decisions and management.The Young Ecosystem Services Specialists (YESS) completed a Strengths-Weaknesses-Opportunities-Threats (SWOT) analysis of ES through YESS member surveys. Strengths include the approach...

  2. Strength of Materials and Structures

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@ All engineering structures designed according to modern principles have to be strong and sufficiently rigid. Scientists and engineers have long recognized the importance of the strength of materials and structures, and dedicated much their efforts to both fundamental and industrial research into the theory for vast engineering materials and various structures. A lot of engineers need to be familiar with the fundamental principles of strength in materials and structures in order to design structures to resist failures. This book is a very good one to provide them with these principles.

  3. Topological strength of magnetic skyrmions

    Science.gov (United States)

    Bazeia, D.; Ramos, J. G. G. S.; Rodrigues, E. I. B.

    2017-02-01

    This work deals with magnetic structures that attain integer and half-integer skyrmion numbers. We model and solve the problem analytically, and show how the solutions appear in materials that engender distinct, very specific physical properties, and use them to describe their topological features. In particular, we found a way to model skyrmion with a large transition region correlated with the presence of a two-peak skyrmion number density. Moreover, we run into the issue concerning the topological strength of a vortex-like structure and suggest an experimental realization, important to decide how to modify and measure the topological strength of the magnetic structure.

  4. Fractional lattice charge transport

    Science.gov (United States)

    Flach, Sergej; Khomeriki, Ramaz

    2017-01-01

    We consider the dynamics of noninteracting quantum particles on a square lattice in the presence of a magnetic flux α and a dc electric field E oriented along the lattice diagonal. In general, the adiabatic dynamics will be characterized by Bloch oscillations in the electrical field direction and dispersive ballistic transport in the perpendicular direction. For rational values of α and a corresponding discrete set of values of E(α) vanishing gaps in the spectrum induce a fractionalization of the charge in the perpendicular direction - while left movers are still performing dispersive ballistic transport, the complementary fraction of right movers is propagating in a dispersionless relativistic manner in the opposite direction. Generalizations and the possible probing of the effect with atomic Bose-Einstein condensates and photonic networks are discussed. Zak phase of respective band associated with gap closing regime has been computed and it is found converging to π/2 value. PMID:28102302

  5. Battery charging stations

    Energy Technology Data Exchange (ETDEWEB)

    Bergey, M.

    1997-12-01

    This paper discusses the concept of battery charging stations (BCSs), designed to service rural owners of battery power sources. Many such power sources now are transported to urban areas for recharging. A BCS provides the opportunity to locate these facilities closer to the user, is often powered by renewable sources, or hybrid systems, takes advantage of economies of scale, and has the potential to provide lower cost of service, better service, and better cost recovery than other rural electrification programs. Typical systems discussed can service 200 to 1200 people, and consist of stations powered by photovoltaics, wind/PV, wind/diesel, or diesel only. Examples of installed systems are presented, followed by cost figures, economic analysis, and typical system design and performance numbers.

  6. Explosive bulk charge

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Jacob Lee

    2015-04-21

    An explosive bulk charge, including: a first contact surface configured to be selectively disposed substantially adjacent to a structure or material; a second end surface configured to selectively receive a detonator; and a curvilinear side surface joining the first contact surface and the second end surface. The first contact surface, the second end surface, and the curvilinear side surface form a bi-truncated hemispherical structure. The first contact surface, the second end surface, and the curvilinear side surface are formed from an explosive material. Optionally, the first contact surface and the second end surface each have a substantially circular shape. Optionally, the first contact surface and the second end surface consist of planar structures that are aligned substantially parallel or slightly tilted with respect to one another. The curvilinear side surface has one of a smooth curved geometry, an elliptical geometry, and a parabolic geometry.

  7. High dynamic range charge measurements

    Energy Technology Data Exchange (ETDEWEB)

    De Geronimo, Gianluigi

    2012-09-04

    A charge amplifier for use in radiation sensing includes an amplifier, at least one switch, and at least one capacitor. The switch selectively couples the input of the switch to one of at least two voltages. The capacitor is electrically coupled in series between the input of the amplifier and the input of the switch. The capacitor is electrically coupled to the input of the amplifier without a switch coupled therebetween. A method of measuring charge in radiation sensing includes selectively diverting charge from an input of an amplifier to an input of at least one capacitor by selectively coupling an output of the at least one capacitor to one of at least two voltages. The input of the at least one capacitor is operatively coupled to the input of the amplifier without a switch coupled therebetween. The method also includes calculating a total charge based on a sum of the amplified charge and the diverted charge.

  8. Self-consistent theory of charged current neutrino-nucleus reactions

    Energy Technology Data Exchange (ETDEWEB)

    Paar, Nils; Marketin, Tomislav; Vretenar, Dario [Physics Department, Faculty of Science, University Zagreb (Croatia); Ring, Peter [Physik-Department, Technischen Universitaet Muenchen, D-85748 Muenchen (Germany)

    2009-07-01

    A novel theoretical framework has been introduced for description of neutrino induced reactions with nuclei. The properties of target nuclei are determined in a self-consistent way using relativistic mean-field framework based on effective Lagrangians with density dependent meson-nucleon vertex functions. The weak lepton-hadron interaction is expressed in the standard current-current form, the nuclear ground state is described in the relativistic Hartree-Bogolyubov model, and the relevant transitions to excited nuclear states are calculated in the proton-neutron relativistic quasiparticle random phase approximation. This framework has been employed in studies of charged-current neutrino reactions involving nuclei of relevance for neutrino detectors, r-process nuclei, and neutrino-nucleus cross sections averaged over measured neutrino fluxes and supernova neutrino distributions.

  9. 12 CFR 226.4 - Finance charge.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 3 2010-01-01 2010-01-01 false Finance charge. 226.4 Section 226.4 Banks and... LENDING (REGULATION Z) General § 226.4 Finance charge. (a) Definition. The finance charge is the cost of...) Charges by third parties. The finance charge includes fees and amounts charged by someone other than...

  10. Proton Dissociation from Surfaces of Variable Charge Soil and Minerals

    Institute of Scientific and Technical Information of China (English)

    LUYA-HAI; HUANGCHANG-YONG; 等

    1994-01-01

    Experiments on proton dissociation from the surfaces of goethite,amorphous Al oxide.kaolinite and latosol were carried out,showing amphoteric behavior with reacions of proton dissociation-association on the surfaces and buffering capacity in such a sequence as amorphous Al oxide>latosol>kaolinite>goethite.Dissociation constants of surface proton,pKsa are significantly correlated with surface charge density,which has been proved with an elecrochemical model.The intrinsic constants of proton dissociation,Ksa(int),gained by eptrapolation to zero charge conditions of plots of pKsa against σ0,could be used to estimate the acidity strength of variable charge surfaces,The value of pKsa(int) is 8.08 for goethite,1.2 for a morphous Al oxide,6.62 for kaolinite and 5.32 for latosol.

  11. Nonextensive dust acoustic waves in a charge varying dusty plasma

    Science.gov (United States)

    Bacha, Mustapha; Tribeche, Mouloud

    2012-01-01

    Our recent analysis on nonlinear nonextensive dust-acoustic waves (DA) [Amour and Tribeche in Phys. Plasmas 17:063702, 2010] is extended to include self-consistent nonadiabatic grain charge fluctuation. The appropriate nonextensive electron charging current is rederived based on the orbit-limited motion theory. Our results reveal that the amplitude, strength and nature of the nonlinear DA waves (solitons and shocks) are extremely sensitive to the degree of ion nonextensivity. Stronger is the electron correlation, more important is the charge variation induced nonlinear wave damping. The anomalous dissipation effects may prevail over that dispersion as the electrons evolve far away from their Maxwellian equilibrium. Our investigation may be of wide relevance to astronomers and space scientists working on interstellar dusty plasmas where nonthermal distributions are turning out to be a very common and characteristic feature.

  12. Hydrogen influence on the mechanical behaviour of high strength steel

    Energy Technology Data Exchange (ETDEWEB)

    Herenu, Silvina [National Technology Univ. of San Nicolas (Argentina).; National Council of Scientific Research and Technology (Argentina); Armas, Alberto [National Univ. of Rosario (Argentina); Brandaleze, Elena [National Technology Univ. of San Nicolas (Argentina). Metallurgical Dept.; Mansilla, Graciela [National Technology Univ. of San Nicolas (Argentina).

    2010-07-01

    Though numerous studies have been devoted to hydrogen embrittlement in steels, up to date there is not a general agreement about the effect of hydrogen on the mechanical behaviour. The purpose of this paper is to analyze the influence of hydrogen on the mechanical response of high strength steels. Samples were cathodically charged with hydrogen, previous to low cyclic fatigue and tensile tests at room temperature. The presence of hydrogen produces softening effects on the cyclic behaviour and improvements in the fatigue life for low hydrogen contents. The stress-strain curves of tensile tests on pre-charged samples depend on the strain rate imposed. Both tensile and fatigue response could be explained by the hydrogen enhancement of dislocation mobility mechanism. (orig.)

  13. Butterflies with rotation and charge

    Science.gov (United States)

    Reynolds, Alan P.; Ross, Simon F.

    2016-11-01

    We explore the butterfly effect for black holes with rotation or charge. We perturb rotating BTZ and charged black holes in 2 + 1 dimensions by adding a small perturbation on one asymptotic region, described by a shock wave in the spacetime, and explore the effect of this shock wave on the length of geodesics through the wormhole and hence on correlation functions. We find the effect of the perturbation grows exponentially at a rate controlled by the temperature; dependence on the angular momentum or charge does not appear explicitly. We comment on issues affecting the extension to higher-dimensional charged black holes.

  14. Butterflies with rotation and charge

    CERN Document Server

    Reynolds, Alan P

    2016-01-01

    We explore the butterfly effect for black holes with rotation or charge. We perturb rotating BTZ and charged black holes in 2+1 dimensions by adding a small perturbation on one asymptotic region, described by a shock wave in the spacetime, and explore the effect of this shock wave on the length of geodesics through the wormhole and hence on correlation functions. We find the effect of the perturbation grows exponentially at a rate controlled by the temperature; dependence on the angular momentum or charge does not appear explicitly. We comment on issues affecting the extension to higher-dimensional charged black holes.

  15. Charge transport in polymeric transistors

    Directory of Open Access Journals (Sweden)

    Alberto Salleo

    2007-03-01

    Full Text Available Polymeric semiconductors have attracted much attention because of their possible use as active materials in printed electronics. Thin-film transistors (TFTs are a convenient tool for studying charge-transport physics in conjugated polymers. Two families of materials are reviewed here: fluorene copolymers and polythiophenes. Because charge transport is highly anisotropic in molecular conductors, the electrical properties of conjugated polymers are strongly dependent on microstructure. Molecular weight, polydispersity, and regioregularity all affect morphology and charge-transport in these materials. Charge transport models based on microstructure are instrumental in identifying the electrical bottlenecks in these materials.

  16. Charged Polaritons with Spin 1

    Directory of Open Access Journals (Sweden)

    Samoilov V.

    2011-04-01

    Full Text Available We present a new model for metal which is based on the stimulated vibration of independent charged Fermi-ions, representing as independent harmonic oscillators with natural frequencies, under action of longitudinal and transverse elastic waves. Due to application of the elastic wave-particle principle and ion-wave dualities, we predict the existence of two types of charged Polaritons with spin 1 which are induced by longitudinal and transverse elastic fields. As result of presented theory, at small wavenumbers, these charged polaritons represent charged phonons.

  17. Low-charge-state linac

    Energy Technology Data Exchange (ETDEWEB)

    Shepard, K.W.; Kim, J.W.

    1995-08-01

    A design is being developed for a low-charge-state linac suitable for injecting ATLAS with a low-charge-state, radioactive beam. Initial work indicates that the existing ATLAS interdigital superconducting accelerating structures, together with the superconducting quadrupole transverse focussing element discussed above, provides a basis for a high-performance low-charge-state linac. The initial 2 or 3 MV of such a linac could be based on a normally-conducting, low-frequency RFQ, possibly combined with 24-MHz superconducting interdigital structures. Beam dynamics studies of the whole low-charge-state post-accelerator section were carried out in early FY 1995.

  18. Modeling of Sylgard Adhesive Strength

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, Ralph Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-02-03

    Sylgard is the name of a silicone elastomeric potting material manufactured by Dow Corning Corporation.1 Although the manufacturer cites its low adhesive strength as a feature of this product, thin layers of Sylgard do in fact have a non-negligible strength, which has been measured in recent tensile and shear debonding tests. The adhesive strength of thin layers of Sylgard potting material can be important in applications in which components having signi cantly di erent thermal expansion properties are potted together, and the potted assembly is subjected to temperature changes. The tensile and shear tractions developed on the potted surfaces of the components can cause signi cant internal stresses, particularly for components made of low-strength materials with a high area-to-volume ratio. This report is organized as follows: recent Sylgard debonding tests are rst brie y summarized, with particular attention to the adhesion between Sylgard and PBX 9501, and also between Sylgard and aluminum. Next, the type of numerical model that will be used to simulate the debonding behavior exhibited in these tests is described. Then the calibration of the debonding model will be illustrated. Finally, the method by which the model parameters are adjusted (scaled) to be applicable to other, non- tested bond thicknesses is summarized, and all parameters of the model (scaled and unscaled) are presented so that other investigators can reproduce all of the simulations described in this report as well as simulations of the application of interest.

  19. Fast electromagnetic field strength probes

    NARCIS (Netherlands)

    Leferink, Frank; Serra, Ramiro

    2013-01-01

    Diode detectors and thermocouple detectors are conventionally used to measure electromagnetic field strength. Both detectors have some disadvantages for applications where a fast response and a high dynamic range is required. The diode detector is limited in dynamic range. The dynamic range is impor

  20. Iron free permanent magnet systems for charged particle beam optics

    Energy Technology Data Exchange (ETDEWEB)

    Lund, S.M.; Halbach, K.

    1995-09-03

    The strength and astounding simplicity of certain permanent magnet materials allow a wide variety of simple, compact configurations of high field strength and quality multipole magnets. Here we analyze the important class of iron-free permanent magnet systems for charged particle beam optics. The theory of conventional segmented multipole magnets formed from uniformly magnetized block magnets placed in regular arrays about a circular magnet aperture is reviewed. Practical multipole configurations resulting are presented that are capable of high and intermediate aperture field strengths. A new class of elliptical aperture magnets is presented within a model with continuously varying magnetization angle. Segmented versions of these magnets promise practical high field dipole and quadrupole magnets with an increased range of applicability.

  1. Surface physicochemistry and ionic strength affects eDNA's role in bacterial adhesion to abiotic surfaces

    DEFF Research Database (Denmark)

    Regina, Viduthalai R.; Lokanathan, Arcot R.; Modrzynski, Jakub Jan;

    2014-01-01

    DNA-mediated adhesion depends on the physicochemical properties of the surface and surrounding liquid. We investigated eDNA alteration of cell surface hydrophobicity and zeta potential, and subsequently quantified the effect of eDNA on the adhesion of Staphylococcus xylosus to glass surfaces functionalised...... ionic strengths. No effect was seen on glass surfaces and carboxyl-functionalised surfaces at high ionic strength, and a reverse effect occurred on amine-functionalised surfaces at low ionic strength. However, eDNA promoted adhesion of cells to hydrophobic surfaces irrespective of the ionic strength...... with different chemistries resulting in variable hydrophobicity and charge. Cell adhesion experiments were carried out at three different ionic strengths. Removal of eDNA from S. xylosus cells by DNase treatment did not alter the zeta potential, but rendered the cells more hydrophilic. DNase treatment impaired...

  2. Nucleon tensor charges and electric dipole moments

    Science.gov (United States)

    Pitschmann, Mario; Seng, Chien-Yeah; Roberts, Craig D.; Schmidt, Sebastian M.

    2015-04-01

    A symmetry-preserving Dyson-Schwinger equation treatment of a vector-vector contact interaction is used to compute dressed-quark-core contributions to the nucleon σ -term and tensor charges. The latter enable one to directly determine the effect of dressed-quark electric dipole moments (EDMs) on neutron and proton EDMs. The presence of strong scalar and axial-vector diquark correlations within ground-state baryons is a prediction of this approach. These correlations are active participants in all scattering events and thereby modify the contribution of the singly represented valence quark relative to that of the doubly represented quark. Regarding the proton σ -term and that part of the proton mass which owes to explicit chiral symmetry breaking, with a realistic d -u mass splitting, the singly represented d quark contributes 37% more than the doubly represented u quark; and in connection with the proton's tensor charges, δTu , δTd , the ratio δTd /δTu is 18% larger than anticipated from simple quark models. Of particular note, the size of δTu is a sensitive measure of the strength of dynamical chiral symmetry breaking; and δTd measures the amount of axial-vector diquark correlation within the proton, vanishing if such correlations are absent.

  3. Charge transfer in multicomponent oxides

    Science.gov (United States)

    Kohan, A. F.; Ceder, G.

    1998-02-01

    The transfer of charge between different ions in an oxide plays an essential role in the stability of these compounds. Since small variations in charge can introduce large changes in the total energy, a correct description of this phenomenon is critical. In this work, we show that the ionic charge in oxides can strongly depend on its atomic environment. A model to assign point charges to atoms as a function of their atomic environment has recently been proposed for binary alloys [C. Wolverton, A. Zunger, S. Froyen, and S.-H. Wei, Phys. Rev. B 54, 7843 (1996)] and proven to be very successful in screened solids such as semiconductors and metals. Here, we extend this formalism to multicomponent oxides and we assess its applicability. The simple point-charge model predicts a linear relation between the charge on an atom and the number of unlike neighbors, and between the net value of the charge and the Coulomb field at a given site. The applicability of this approach is tested in a large-supercell self-consistent tight-binding calculation for a random Zr-Ca-O alloy. The observed fluctuations of the ionic charge about the average linear behavior (as a function of the number of unlike neighbors) was larger than 0.25 electrons even when many shells of atomic neighbors were considered in the fit. This variation is significant since it can introduce large errors in the electrostatic energy. On the other hand, for small absolute values of the charge, the ionic charge varied linearly with the Coulomb field, in agreement with previous findings. However, for large Coulomb fields, this function saturates at the formal chemical charge.

  4. Quantum charged rigid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Cordero, Ruben [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del I.P.N., Unidad Adolfo Lopez Mateos, Edificio 9, 07738 Mexico, D.F. (Mexico); Molgado, Alberto [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Zacatecas Zac. (Mexico); Rojas, Efrain, E-mail: cordero@esfm.ipn.mx, E-mail: amolgado@fisica.uaz.edu.mx, E-mail: efrojas@uv.mx [Departamento de Fisica, Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico)

    2011-03-21

    The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski-Hamiltonian approach, we observed that the theory comprises the management of both first- and second-class constraints. We thus show that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits us to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.

  5. Quantum charged rigid membrane

    CERN Document Server

    Cordero, Ruben; Rojas, Efrain

    2010-01-01

    The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski-Hamiltonian approach we observed that the theory comprises the management of both first- and second-class constraints. We show thus that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.

  6. The electronic mechanism of the gamma/gamma' interface strength of Ir-based alloys

    CERN Document Server

    Chen, K; Tse, J S

    2002-01-01

    The electronic structures of the gamma/gamma' interface for two-phase Ir-based alloys (Ir/Ir sub 3 Ta and Ir/Ir sub 3 Ti) have been investigated by performing first-principles quantum mechanics DMol3 (a type of density functional theory for molecules) calculations. The Mayer bond order (MBO) is used to represent the shear and cohesion strengths of the interface by a local sum of the horizontal and vertical MBOs. By comparison with those for single-crystal Ir, the results show that both the cohesive and shear strengths of the gamma/gamma' interface for the Ir/Ir sub 3 Ta alloy increase. The cohesive strength of the interface for the Ir/Ir sub 3 Ti alloy increases, whereas the shear strength of the interface for Ir/Ir sub 3 Ti decreases. The electron charge density, the Hirshfeld charge, and orbital charge transfers are also calculated and analysed. An electronic mechanism for the gamma/gamma' interface strength of Ir-based alloys is then suggested.

  7. Metallic charge stripes in cuprates

    OpenAIRE

    Tranquada, J. M.

    2003-01-01

    Some recent evidence for the existence of dynamic, metallic stripes in the 214-family of cuprates is reviewed. The mechanism of stripe pinning is considered, and changes in the charge density within stripes between the pinned and dynamic phases is discussed. From a purely experimental perspective, dynamic charge stripes are fully compatible with nodal ``quasiparticles'' and other electronic properties common to all superconducting cuprates.

  8. Filling of charged cylindrical capillaries

    NARCIS (Netherlands)

    Das, Siddhartha; Chanda, Sourayon; Eijkel, J.C.T.; Tas, N.R.; Chakraborty, Suman; Mitra, Sushanta K.

    2014-01-01

    We provide an analytical model to describe the filling dynamics of horizontal cylindrical capillaries having charged walls. The presence of surface charge leads to two distinct effects: It leads to a retarding electrical force on the liquid column and also causes a reduced viscous drag force because

  9. Charge transport in amorphous oligothiophenes

    Energy Technology Data Exchange (ETDEWEB)

    Schrader, Manuel; Baumeier, Bjoern; Andrienko, Denis [Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany); Elschner, Chris; Riede, Moritz; Leo, Karl [TU Dresden, Institute of Applied Photophysics, Mommsenstr. 13, 01062 Dresden (Germany)

    2011-07-01

    Organic semiconducting materials are needed for emerging devices such as photovoltaic solar cells. In this work we combine first principle calculations, molecular dynamics and kinetic Monte Carlo simulations to study charge transport in dicyanovinyl oligothiophenes of different lengths. Poole-Frenkel behavior of the charge carrier mobility is rationalized based on electrostatic and conformational disorder.

  10. Electrostatic charging of jumping droplets

    Science.gov (United States)

    Miljkovic, Nenad; Preston, Daniel J.; Enright, Ryan; Wang, Evelyn N.

    2013-09-01

    With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

  11. Grain charging in protoplanetary discs

    CERN Document Server

    Ilgner, Martin

    2011-01-01

    Recent work identified a growth barrier for dust coagulation that originates in the electric repulsion between colliding particles. Depending on its charge state, dust material may have the potential to control key processes towards planet formation such as MHD (magnetohydrodynamic) turbulence and grain growth which are coupled in a two-way process. We quantify the grain charging at different stages of disc evolution and differentiate between two very extreme cases: compact spherical grains and aggregates with fractal dimension D_f = 2. Applying a simple chemical network that accounts for collisional charging of grains, we provide a semi-analytical solution. This allowed us to calculate the equilibrium population of grain charges and the ionisation fraction efficiently. The grain charging was evaluated for different dynamical environments ranging from static to non-stationary disc configurations. The results show that the adsorption/desorption of neutral gas-phase heavy metals, such as magnesium, effects the ...

  12. Piston-assisted charge pumping

    CERN Document Server

    Kaur, D; Mourokh, L

    2015-01-01

    We examine charge transport through a system of three sites connected in series in the situation when an oscillating charged piston modulates the energy of the middle site. We show that with an appropriate set of parameters, charge can be transferred against an applied voltage. In this scenario, when the oscillating piston shifts away from the middle site, the energy of the site decreases and it is populated by a charge transferred from the lower energy site. On the other hand, when the piston returns to close proximity, the energy of the middle site increases and it is depopulated by the higher energy site. Thus through this process, the charge is pumped against the potential gradient. Our results can explain the process of proton pumping in one of the mitochondrial enzymes, Complex I. Moreover, this mechanism can be used for electron pumping in semiconductor nanostructures.

  13. Holography, charge and baryon asymmetry

    CERN Document Server

    Mongan, T R

    2009-01-01

    The holographic principle indicates the finite number of bits of information available on the particle horizon describes all physics within the horizon. Linking information on the horizon with Standard Model particles requires a holographic model describing constituents (preons) of Standard Model particles in terms of bits of information on the horizon. Standard Model particles have charges 0, 1/3, 2/3 or 1 in units of the electron charge e, so bits in a preon model must be identified with fractional charge. Energy must be transferred to change the state of a bit, and labeling the low energy state of a bit e/3n and the high energy state -e/3n amounts to defining electric charge. Any such charged preon model will produce more protons than anti-protons at the time of baryogenesis and require baryon asymmetry. It will also produce more positrons than electrons, as suggested by astrophysical measurements.

  14. Collaborative Mobile Charging and Coverage

    Institute of Scientific and Technical Information of China (English)

    吴杰

    2014-01-01

    Wireless energy charging using mobile vehicles has been a viable research topic recently in the area of wireless networks and mobile computing. This paper gives a short survey of recent research conducted in our research group in the area of collaborative mobile charging. In collaborative mobile charging, multiple mobile chargers work together to accomplish a given set of ob jectives. These ob jectives include charging sensors at different frequencies with a minimum number of mobile chargers and reaching the farthest sensor for a given set of mobile chargers, subject to various constraints, including speed and energy limits of mobile chargers. Through the process of problem formulation, solution construction, and future work extension for problems related to collaborative mobile charging and coverage, we present three principles for good practice in conducting research. These principles can potentially be used for assisting graduate students in selecting a research problem for a term project, which can eventually be expanded to a thesis/dissertation topic.

  15. Charge generation associated with liquid spraying in tank cleaning and comparable processes - preliminary experiments

    Science.gov (United States)

    Blum, Carsten; Losert, Oswald F. J.

    2015-10-01

    The BG RCI has initiated investigations in order to improve the data basis for assessing the ignition hazard by electrostatic charging processes associated with the spraying of liquids. On the base of preliminary experiments, we established procedures for measurements of electric field strength and charging current in the presence of aerosol particles. Results obtained with three different nozzle types, variation of pressure and with built-in deflecting plate are presented.

  16. Influence of mechanochemical activation of a charge on properties of mullite-tialite materials

    Directory of Open Access Journals (Sweden)

    Antsiferov V.N.

    2004-01-01

    Full Text Available The influence of mechanochemical activation (MCA of a kaolin-containing charge on the strength of mullite-tialite materials (obtained using methods of semidry molding and polymeric matrix duplication was studied. It is shown that spectral and X-ray indexes of crystallinity of kaolin activated under similar conditions could be used as criteria of MCA efficiency. Parameters of mullite-tialite charge (containing kaolin, alumina and anatase activation were optimized. .

  17. Interaction of a point charge with the surface of a uniaxial dielectric

    CERN Document Server

    Ribič, Primož Rebernik

    2013-01-01

    We analyze the force on a point charge moving at relativistic speeds parallel to the surface of a uniaxial dielectric. Two cases are examined: a lossless dielectric with no dispersion and a dielectric with a plasma type response. The treatment focuses on the peculiarities of the strength and direction of the interaction force as compared to the isotropic case. We show that a plasma type dielectric can, under specific conditions, repel the point charge.

  18. Electronic Correlation Strength of Pu

    DEFF Research Database (Denmark)

    Svane, A.; C. Albers, R.; E. Christensen, N.

    2013-01-01

    A new electronic quantity, the correlation strength, is defined as a necessary step for understanding the properties and trends in strongly correlated electronic materials. As a test case, this is applied to the different phases of elemental Pu. Within the GW approximation we have surprisingly...... found a "universal" scaling relationship, where the f-electron bandwidth reduction due to correlation effects is shown to depend only upon the local density approximation (LDA) bandwidth and is otherwise independent of crystal structure and lattice constant....

  19. Simulation for signal charge transfer of charge coupled devices

    Institute of Scientific and Technical Information of China (English)

    Wang Zujun; Liu Yinong; Chen Wei; Tang Benqi; Xiao Zhigang; Huang Shaoyan; Liu Minbo; Zhang Yong

    2009-01-01

    Physical device models and numerical processing methods are presented to simulate a linear buried channel charge coupled devices (CCDs). The dynamic transfer process of CCD is carried out by a three-phase clock pulse driver. By using the semiconductor device simulation software MEDICI, dynamic transfer pictures of signal charges cells, electron concentration and electrostatic potential are presented. The key parameters of CCD such as charge transfer efficiency (CTE) and dark electrons are numerically simulated. The simulation results agree with the theoretic and experimental results.

  20. Binding Energies of a Positively Charged Exciton in a Quantum Disc

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The binding energies of the lowest singlet and triplet states of positively charged excitons confined to a quantum disc are studied using exact diagonalization techniques. We investigate the dependence of the binding energies on the confinement strength and on the effective electron-to-hole mass ratio. The results we have obtained show that the binding energies are closely correlated to the strength of the confinement potential and the effective electron-to-hole mass ratio.

  1. Polyelectrolyte decomplexation via addition of salt: charge correlation driven zipper.

    Science.gov (United States)

    Antila, Hanne S; Sammalkorpi, Maria

    2014-03-20

    We report the first atomic scale studies of polyelectrolyte decomplexation. The complex between DNA and polylysine is shown to destabilize and spontaneously open in a gradual, reversible zipper-like mechanism driven by an increase in solution salt concentration. Divalent CaCl2 is significantly more effective than monovalent NaCl in destabilizing the complex due to charge correlations and water binding capability. The dissociation occurs accompanied by charge reversal in which charge correlations and ion binding chemistry play a key role. Our results are in agreement with experimental work on complex dissociation but in addition show the underlying microstructural correlations driving the behavior. Comparison of our full atomic level detail and dynamics results with theoretical works describing the PEs as charged, rigid rods reveals that although charge correlation involved theories provide qualitatively similar responses, considering also specific molecular chemistry and molecular level water contributions provides a more complete understanding of PE complex stability and dynamics. The findings may facilitate controlled release in gene delivery and more in general tuning of PE membrane permeability and mechanical characteristics through ionic strength.

  2. Search for Doubly-Charged Higgs Boson Production at HERA

    CERN Document Server

    Aktas, A.; Anthonis, T.; Antunovic, B.; Aplin, S.; Asmone, A.; Astvatsatourov, A.; Babaev, A.; Backovic, S.; Baghdasaryan, A.; Baranov, P.; Barrelet, E.; Bartel, W.; Baudrand, S.; Baumgartner, S.; Becker, J.; Beckingham, M.; Behnke, O.; Behrendt, O.; Belousov, A.; Berger, N.; Bizot, J.C.; Boenig, M.-O.; Boudry, V.; Bracinik, J.; Brandt, G.; Brisson, V.; Bruncko, D.; Busser, F.W.; Bunyatyan, A.; Buschhorn, G.; Bystritskaya, L.; Campbell, A.J.; Cassol-Brunner, F.; Cerny, K.; Cerny, V.; Chekelian, V.; Contreras, J.G.; Coughlan, J.A.; Cox, B.E.; Cozzika, G.; Cvach, J.; Dainton, J.B.; Dau, W.D.; Daum, K.; de Boer, Y.; Delcourt, B.; Del Degan, M.; De Roeck, A.; De Wolf, E.A.; Diaconu, C.; Dodonov, V.; Dubak, A.; Eckerlin, Guenter; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eliseev, A.; Elsen, E.; Essenov, S.; Falkewicz, A.; Faulkner, P.J.W.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Finke, L.; Fleischer, M.; Flucke, G.; Fomenko, A.; Franke, G.; Frisson, T.; Gabathuler, E.; Garutti, E.; Gayler, J.; Gerlich, C.; Ghazaryan, Samvel; Ginzburgskaya, S.; Glazov, A.; Glushkov, I.; Goerlich, L.; Goettlich, M.; Gogitidze, N.; Gorbounov, S.; Grab, C.; Greenshaw, T.; Gregori, M.; Grell, B.R.; Grindhammer, G.; Gwilliam, C.; Haidt, D.; Hajduk, L.; Hansson, M.; Heinzelmann, G.; Henderson, R.C.W.; Henschel, H.; Herrera, G.; Hildebrandt, M.; Hiller, K.H.; Hoffmann, D.; Horisberger, R.; Hovhannisyan, A.; Hreus, T.; Hussain, S.; Ibbotson, M.; Ismail, M.; Jacquet, M.; Janauschek, L.; Janssen, X.; Jemanov, V.; Jonsson, L.; Johnson, D.P.; Jung, Andreas Werner; Jung, H.; Kapichine, M.; Katzy, J.; Kenyon, I.R.; Kiesling, Christian M.; Klein, M.; Kleinwort, C.; Klimkovich, T.; Kluge, T.; Knies, G.; Knutsson, A.; Korbel, V.; Kostka, P.; Krastev, K.; Kretzschmar, J.; Kropivnitskaya, A.; Kruger, K.; Landon, M.P.J.; Lange, W.; Lastovicka-Medin, G.; Laycock, P.; Lebedev, A.; Leibenguth, G.; Lendermann, V.; Levonian, S.; Lindfeld, L.; Lipka, K.; Liptaj, A.; List, B.; List, J.; Lobodzinska, E.; Loktionova, N.; Lopez-Fernandez, R.; Lubimov, V.; Lucaci-Timoce, A.-I.; Lueders, H.; Luke, D.; Lux, T.; Lytkin, L.; Makankine, A.; Malden, N.; Malinovski, E.; Mangano, S.; Marage, P.; Marshall, R.; Marti, L.; Martisikova, M.; Martyn, H.-U.; Maxfield, S.J.; Mehta, A.; Meier, K.; Meyer, A.B.; Meyer, H.; Meyer, J.; Michels, V.; Mikocki, S.; Milcewicz-Mika, I.; Milstead, D.; Mladenov, D.; Mohamed, A.; Moreau, F.; Morozov, A.; Morris, J.V.; Mozer, Matthias Ulrich; Muller, K.; Murin, P.; Nankov, K.; Naroska, B.; Naumann, Th.; Newman, Paul R.; Niebuhr, C.; Nikiforov, A.; Nowak, G.; Nowak, K.; Nozicka, M.; Oganezov, R.; Olivier, B.; Olsson, J.E.; Osman, S.; Ozerov, D.; Palichik, V.; Panagoulias, I.; Papadopoulou, T.; Pascaud, C.; Patel, G.D.; Peng, H.; Perez, E.; Perez-Astudillo, D.; Perieanu, A.; Petrukhin, A.; Pitzl, D.; Placakyte, R.; Portheault, B.; Povh, B.; Prideaux, P.; Rahmat, A.J.; Raicevic, N.; Reimer, P.; Rimmer, A.; Risler, C.; Rizvi, E.; Robmann, P.; Roland, B.; Roosen, R.; Rostovtsev, A.; Rurikova, Z.; Rusakov, S.; Salvaire, F.; Sankey, D.P.C.; Sauvan, E.; Schatzel, S.; Schmidt, S.; Schmitt, S.; Schmitz, C.; Schoeffel, L.; Schoning, A.; Schultz-Coulon, H.-C.; Sefkow, F.; Shaw-West, R.N.; Sheviakov, I.; Shtarkov, L.N.; Sirois, Y.; Sloan, T.; Smirnov, P.; Soloviev, Y.; South, D.; Spaskov, V.; Specka, Arnd E.; Steder, M.; Stella, B.; Stiewe, J.; Stoilov, A.; Straumann, U.; Sunar, D.; Tchoulakov, V.; Thompson, Graham; Thompson, P.D.; Toll, T.; Tomasz, F.; Traynor, D.; Truol, P.; Tsakov, I.; Tsipolitis, G.; Tsurin, I.; Turnau, J.; Tzamariudaki, E.; Urban, K.; Urban, Marcel; Usik, A.; Utkin, D.; Valkarova, A.; Vallee, C.; Van Mechelen, P.; Trevino, A.Vargas; Vazdik, Y.; Veelken, C.; Vinokurova, S.; Volchinski, V.; Wacker, K.; Weber, G.; Weber, R.; Wegener, D.; Werner, C.; Wessels, M.; Wessling, B.; Wissing, Ch.; Wolf, R.; Wunsch, E.; Xella, S.; Yan, W.; Yeganov, V.; Zacek, J.; Zalesak, J.; Zhang, Z.; Zhelezov, A.; Zhokin, A.; Zhu, Y.C.; Zimmermann, J.; Zimmermann, T.; Zohrabyan, H.; Zomer, F.

    2006-01-01

    A search for the single production of doubly-charged Higgs bosons H^{\\pm \\pm} in ep collisions is presented. The signal is searched for via the Higgs decays into a high mass pair of same charge leptons, one of them being an electron. The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment at HERA. No evidence for doubly-charged Higgs production is observed and mass dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only decays into an electron and a muon via a coupling of electromagnetic strength h_{e \\mu} = \\sqrt{4 \\pi \\alpha_{em}} = 0.3, a lower limit of 141 GeV on the H^{\\pm\\pm} mass is obtained at the 95% confidence level. For a doubly-charged Higgs decaying only into an electron and a tau and a coupling h_{e\\tau} = 0.3, masses below 112 GeV are ruled out.

  3. Cation charge dependence of the forces driving DNA assembly.

    Science.gov (United States)

    DeRouchey, Jason; Parsegian, V Adrian; Rau, Donald C

    2010-10-20

    Understanding the strength and specificity of interactions among biologically important macromolecules that control cellular functions requires quantitative knowledge of intermolecular forces. Controlled DNA condensation and assembly are particularly critical for biology, with separate repulsive and attractive intermolecular forces determining the extent of DNA compaction. How these forces depend on the charge of the condensing ion has not been determined, but such knowledge is fundamental for understanding the basis of DNA-DNA interactions. Here, we measure DNA force-distance curves for a homologous set of arginine peptides. All forces are well fit as the sum of two exponentials with 2.4- and 4.8-Å decay lengths. The shorter-decay-length force is always repulsive, with an amplitude that varies slightly with length or charge. The longer-decay-length force varies strongly with cation charge, changing from repulsion with Arg¹ to attraction with Arg². Force curves for a series of homologous polyamines and the heterogeneous protein protamine are quite similar, demonstrating the universality of these forces for DNA assembly. Repulsive amplitudes of the shorter-decay-length force are species-dependent but nearly independent of charge within each species. A striking observation was that the attractive force amplitudes for all samples collapse to a single curve, varying linearly with the inverse of the cation charge.

  4. When Charged Black Holes Merge

    Science.gov (United States)

    Kohler, Susanna

    2016-08-01

    Most theoretical models assume that black holes arent charged. But a new study shows that mergers of charged black holes could explain a variety of astrophysical phenomena, from fast radio bursts to gamma-ray bursts.No HairThe black hole no hair theorem states that all black holes can be described by just three things: their mass, their spin, and their charge. Masses and spins have been observed and measured, but weve never measured the charge of a black hole and its widely believed that real black holes dont actually have any charge.That said, weve also never shown that black holes dont have charge, or set any upper limits on the charge that they might have. So lets suppose, for a moment, that its possible for a black hole to be charged. How might that affect what we know about the merger of two black holes? A recent theoretical study by Bing Zhang (University of Nevada, Las Vegas) examines this question.Intensity profile of a fast radio burst, a sudden burst of radio emission that lasts only a few milliseconds. [Swinburne Astronomy Productions]Driving TransientsZhangs work envisions a pair of black holes in a binary system. He argues that if just one of the black holes carries charge possibly retained by a rotating magnetosphere then it may be possible for the system to produce an electromagnetic signal that could accompany gravitational waves, such as a fast radio burst or a gamma-ray burst!In Zhangs model, the inspiral of the two black holes generates a global magnetic dipole thats perpendicular to the plane of the binarys orbit. The magnetic flux increases rapidly as the separation between the black holes decreases, generating an increasingly powerful magnetic wind. This wind, in turn, can give rise to a fast radio burst or a gamma-ray burst, depending on the value of the black holes charge.Artists illustration of a short gamma-ray burst, thought to be caused by the merger of two compact objects. [ESO/A. Roquette]Zhang calculates lower limits on the charge

  5. Charge-pump voltage converter

    Science.gov (United States)

    Brainard, John P.; Christenson, Todd R.

    2009-11-03

    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  6. Big break for charge symmetry

    CERN Document Server

    Miller, G A

    2003-01-01

    Two new experiments have detected charge-symmetry breaking, the mechanism responsible for protons and neutrons having different masses. Symmetry is a crucial concept in the theories that describe the subatomic world because it has an intimate connection with the laws of conservation. The theory of the strong interaction between quarks - quantum chromodynamics - is approximately invariant under what is called charge symmetry. In other words, if we swap an up quark for a down quark, then the strong interaction will look almost the same. This symmetry is related to the concept of sup i sospin sup , and is not the same as charge conjugation (in which a particle is replaced by its antiparticle). Charge symmetry is broken by the competition between two different effects. The first is the small difference in mass between up and down quarks, which is about 200 times less than the mass of the proton. The second is their different electric charges. The up quark has a charge of +2/3 in units of the proton charge, while ...

  7. Analyzing Affect of Image Charge in Space Charge Effect

    Institute of Scientific and Technical Information of China (English)

    ZhangXueying; XuHushan; JiaFei; LiWenfei

    2003-01-01

    There is an increasing requirement of high injection current and highly charged ion beams for accelerators at many laboratories, such as CERN, GSI, GANIL and IMP, with the development of super-conducting ECR source in recent.years. In this case, the space charge effect becomes a major concern when the beam current is as high as tens of mA. In fact, the faradic field induced by the image charges will be come into the metallic surfaces while the beams are transported in a vacuum tube or in between two plates. In order to ensure studying the space charge effect in reason, it is necessary to investigate the effect from such a field.

  8. Charge density waves in solids

    CERN Document Server

    Gor'kov, LP

    2012-01-01

    The latest addition to this series covers a field which is commonly referred to as charge density wave dynamics.The most thoroughly investigated materials are inorganic linear chain compounds with highly anisotropic electronic properties. The volume opens with an examination of their structural properties and the essential features which allow charge density waves to develop.The behaviour of the charge density waves, where interesting phenomena are observed, is treated both from a theoretical and an experimental standpoint. The role of impurities in statics and dynamics is considered and an

  9. Rewritable artificial magnetic charge ice

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y. -L.; Xiao, Z. -L.; Snezhko, A.; Xu, J.; Ocola, L. E.; Divan, R.; Pearson, J. E.; Crabtree, G. W.; Kwok, W. -K.

    2016-05-19

    Artificial ices enable the study of geometrical frustration by design and through direct observation. However, it has proven difficult to achieve tailored long-range ordering of their diverse configurations, limiting both fundamental and applied research directions. We designed an artificial spin structure that produces a magnetic charge ice with tunable long-range ordering of eight different configurations. We also developed a technique to precisely manipulate the local magnetic charge states and demonstrate write-read-erase multifunctionality at room temperature. This globally reconfigurable and locally writable magnetic charge ice could provide a setting for designing magnetic monopole defects, tailoring magnonics, and controlling the properties of other two-dimensional materials.

  10. Effect of Zn Adsorption on Charge of Variable Charge Soils

    Institute of Scientific and Technical Information of China (English)

    SUNHAN-YUAN

    1993-01-01

    The variation in appa rent carge of two typical variable charge soils resulting from Zn adsorption were studied by KCl saturation and NH4NO3 replacement methods.Results showed that zinc were adsorbed specifically to those sites with negative charge.As in different pH ranges,the percantages of specific and electrostatic adsorptions of zine and the mechanisms of specific adsorption were different,the effects of Zn adsorption on apparent charge were varied and could be characterized as:when 1 mmol Zn2+ was adsorbed,a change about 1 mmol in the apparent charge was observed in the low pH range(1),1.4 to 1.5mmol in the moderate pH range(II) and 0.55 to 0.6mmol in the high pH range (III).These experimental data,in terms of soil charge,proved once more author's conclusion in the preceding paper(Sun,1993) that in accordance with the behaviors of Zn adsorption by the variable charge soils in relation to pH,three pH ranges with different adsorption mechanisms were delineated;that is,in Range I,specific adsorption was the predominant mechanism,in Ranges II and III,specific and electrostatic adsorptions co-existed,but their specific adsorption mechanisms were not identical.

  11. Comparison of Remolded Shear Strength with Intrinsic Strength Line for Dredged Deposits

    Institute of Scientific and Technical Information of China (English)

    DENG Dong-sheng

    2007-01-01

    Chandler proposed the intrinsic strength line to correlate the undrained shear strength of samples one-dimensionally consolidated from slurry with the void index proposed by Burland. The undrained shear strength on the intrinsic strength line is different from the remolded undrained shear strength that is an important parameter for design and construction of land reclamation. The void index is used in this study for normalizing the remolded strength behavior of dredged deposits. A quantitative relationship between remolded undrained shear strength and void index is established based on extensive data of dredged deposits available from sources of literature. Furthermore, the normalized remolded undrained shear strength is compared with intrinsic strength line. The comparison result indicates that the ratio of undrained shear strength on the intrinsic strength line over remolded undrained shear strength increases with an increase in applied consolidated stress.

  12. Bose-Einstein Correlations of Charged and Neutral Kaons in Deep Inelastic Scattering at HERA

    CERN Document Server

    Chekanov, S; Magill, S; Musgrave, B; Nicholass, D; Repond, J; Yoshida, R; Mattingly, M C K; Jechow, M; Pavel, N; Yagues-Molina, A G; Antonelli, S; Antonioli, P; Bari, G; Basile, M; Bellagamba, L; Bindi, M; Boscherini, D; Bruni, A; Bruni, G; Cifarelli, L; Cindolo, F; Contin, A; Corradi, M; De Pasquale, S; Iacobucci, G; Margotti, A; Nania, R; Polini, A; Sartorelli, G; Zichichi, A; Bartsch, D; Brock, I; Goers, S; Hartmann, H; Hilger, E; Jakob, H P; Jüngst, M; Kind, O M; Nuncio-Quiroz, A E; Paul, E; Renner, R; Samson, U; Schonberg, V; Shehzadi, R; Wlasenko, M; Brook, N H; Heath, G P; Morris, J D; Namsoo, T; Capua, M; Fazio, S; Mastroberardino, A; Schioppa, M; Susinno, G; Tassi, E; Kim, J Y; Ma, K J; Ibrahim, Z A; Kamaluddin, B; Wan-Abdullah, W A T; Ning, Y; Ren, Z; Sciulli, F; Chwastowski, J; Eskreys, A; Figiel, J; Galas, A; Gil, M; Olkiewicz, K; Stopa, P; Zawiejski, L; Adamczyk, L; Bold, T; Grabowska-Bold, I; Kisielewska, D; Lukasik, J; Przybycien, M; Suszycki, L; Kotanski, A; Slominski, W; Adler, V; Behrens, U; Bloch, I; Blohm, C; Bonato, A; Borras, K; Ciesielski, R; Coppola, N; Dossanov, A; Drugakov, V; Fourletova, J; Geiser, A; Gladkov, D; Göttlicher, P; Grebenyuk, J; Gregor, I; Haas, T; Hain, W; Horn, C; Huttmann, A; Kahle, B; Katkov, I I; Klein, U; Kötz, U; Kowalski, H; Lobodzinska, E; Löhr, B; Mankel, R; Melzer-Pellmann, I A; Miglioranzi, S; Montanari, A; Notz, D; Rinaldi, L; Roloff, P; Rubinsky, I; Santamarta, R; Schneekloth, U; Spiridonov, A; Stadie, H; Szuba, D; Szuba, J; Theedt, T; Wolf, G; Wrona, K; Youngman, C; Zeuner, W; Lohmann, W; Schlenstedt, S; Barbagli, G; Gallo, E; Pelfer, P G; Bamberger, A; Dobur, D; Karstens, F; Vlasov, N N; Bussey, P J; Doyle, A T; Dunne, W; Ferrando, J; Forrest, M; Saxon, D H; Skillicorn, I O; Gialas, I; Papageorgiu, K; Gosau, T; Holm, U; Klanner, R; Lohrmann, E; Salehi, H; Schleper, P; Schörner-Sadenius, T; Sztuk, J; Wichmann, K; Wick, K; Foudas, C; Fry, C; Long, K R; Tapper, A D; Kataoka, M; Matsumoto, T; Nagano, K; Tokushuku, K; Yamada, S; Yamazaki, Y; Barakbaev, A N; Boos, E G; Pokrovskiy, N S; Zhautykov, B O; Aushev, V; Son, D; De Favereau, J; Piotrzkowski, K; Barreiro, F; Glasman, C; Jiménez, M; Labarga, L; Del Peso, J; Ron, E; Soares, M; Terron, J; Zambrana, M; Corriveau, F; Liu, C; Walsh, R; Zhou, C; Tsurugai, T; Antonov, A; Dolgoshein, B A; Sosnovtsev, V; Stifutkin, A; Suchkov, S; Dementiev, R K; Ermolov, P F; Gladilin, L K; Khein, L A; Korzhavina, I A; Kuzmin, V A; Levchenko, B B; Lukina, O Yu; Proskuryakov, A S; Shcheglova, L M; Zotkin, D S; Zotkin, S A; Abt, I; Büttner, C; Caldwell, A; Kollar, D; Schmidke, W B; Sutiak, J; Grigorescu, G; Keramidas, A; Koffeman, E; Kooijman, P; Pellegrino, A; Tiecke, H; Vázquez, M; Wiggers, L; Brümmer, N; Bylsma, B; Durkin, L S; Lee, A; Ling, T Y; Allfrey, P D; Bell, M A; Cooper-Sarkar, A M; Cottrell, A; Devenish, R C E; Foster, B; Korcsak-Gorzo, K; Patel, S; Roberfroid, V; Robertson, A; Straub, P B; Uribe-Estrada, C; Walczak, R; Bellan, P; Bertolin, A; Brugnera, R; Carlin, R; Dal Corso, F; Dusini, S; Garfagnini, A; Limentani, S; Longhin, A; Stanco, L; Turcato, M; Oh, B Y; Raval, A; Ukleja, J; Whitmore, J J; Iga, Y; D'Agostini, G; Marini, G; Nigro, A; Cole, J E; Hart, J C; Abramowicz, H; Gabareen, A; Ingbir, R; Kananov, S; Levy, A; Kuze, M; Maeda, J; Hori, R; Kagawa, S; Okazaki, N; Shimizu, S; Tawara, T; Hamatsu, R; Kaji, H; Kitamura, S; Ota, O; Ri, Y D; Ferrero, M I; Monaco, V; Sacchi, R; Solano, A; Arneodo, M; Ruspa, M; Fourletov, S; Martin, J F; Boutle, S K; Butterworth, J M; Gwenlan, C; Jones, T W; Loizides, J H; Sutton, M R; Wing, M; Brzozowska, B; Ciborowski, J; Grzelak, G; Kulinski, P; Luzniak, P; Malka, J; Nowak, R J; Pawlak, J M; Tymieniecka, T; Ukleja, A; Zarnecki, A F; Adamus, M; Plucinsky, P P; Eisenberg, Y; Giller, I; Hochman, D; Karshon, U; Rosin, M; Brownson, E; Danielson, T; Everett, A; Kcira, D; Reeder, D D; Ryan, P; Savin, A A; Smith, W H; Wolfe, H; Bhadra, S; Catterall, C D; Cui, Y; Hartner, G; Menary, S; Noor, U; Standage, J; Whyte, J

    2007-01-01

    Bose-Einstein correlations of charged and neutral kaons have been measured in e+-p deep inelastic scattering with an integrated luminosity of 121 pb-1 using the ZEUS detector at HERA. The two-particle correlation function was studied as a function of the four-momentum difference of the kaon pairs, Q_12=sqrt{-(p_1-p_2)^2}, assuming a Gaussian shape for the particle source. The values of the radius of the production volume, r, and of the correlation strength, lambda, were obtained for both neutral and charged kaons. The radii for charged and neutral kaons are similar and are consistent with those obtained at LEP.

  13. Self-Deflection of Dark Screening Spatial Solitons Based on Higher-Order Space Charge Field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guang-Yong; LIU Jin-Song; LIU Shi-Xiong; WANG Cheng; ZHANG Hui-Lan

    2007-01-01

    The effects of higher-order space charge field on the self-deflection of dark screening spatial solitons in biased photorefractive crystals are numerically investigated under steady-state conditions. The expression for an induced space-charge electric field including higher-order space-charge field terms is obtained. Numerical results indicate that dark solitons possess a self-deflection process during propagation, and the solitons always bend in the direction of the c axis of the crystal The self-deflection of dark solitons can experience considerable increase especially in the regime of high bias field strengths.

  14. Adsorption of insulin peptide on charged single-walled carbon nanotubes: significant role of ordered water molecules.

    Science.gov (United States)

    Shen, Jia-Wei; Wu, Tao; Wang, Qi; Kang, Yu; Chen, Xin

    2009-06-02

    Ordered hydration shells: The more ordered hydration shells outside the charged CNT surfaces prevent more compact adsorption of the peptide in the charged CNT systems [picture: see text], but peptide binding strengths on the charged CNT surfaces are stronger due to the electrostatic interaction.Studies of adsorption dynamics and stability for peptides/proteins on single-walled carbon nanotubes (SWNTs) are of great importance for a better understanding of the properties and nature of nanotube-based biosystems. Herein, the dynamics and mechanism of the adsorption of the insulin chain B peptide on different charged SWNTs are investigated by explicit solvent molecular dynamics simulations. The results show that all types of surfaces effectively attract the model peptide. Water molecules play a significant role in peptide adsorption on the surfaces of charged carbon nanotubes (CNTs). Compared to peptide adsorption on neutral CNT surfaces, the more ordered hydration shells outside the tube prevent more compact adsorption of the peptide in charged CNT systems. This shield effect leads to a smaller conformational change and van der Waals interaction between the peptide and surfaces, but peptide binding strengths on charged CNT surfaces are stronger than those on the neutral CNT surface due to the strong electrostatic interaction. The result of these simulations implies the possibility of improving the binding strength of peptides/proteins on CNT surfaces, as well as keeping the integrity of the peptide/protein conformation in peptide/protein-CNT complexes by charging the CNTs.

  15. Lijiang: From Brand to Strength

    Institute of Scientific and Technical Information of China (English)

    Gao Wentian; Bai Yifeng

    2009-01-01

    @@ The tourism industry is facing unprecedented challenges after the financial crisis.During this "financial winter",how much influence has Lijiang's tourism,the one that has been the pillar industry of Lijiang and important economic growth point received? And how does the government of Lijiang deal with this? How to transform it from "Brand Lijiang" to "Strength Lijiang"? Member of National People's Congress,Lijiang's deputy secretary of municipal party committee,and Mayor Wang Junzheng accepted an exclusive interview with our reporter.

  16. Prediction of underwater target strength

    Institute of Scientific and Technical Information of China (English)

    WANG TongQing; Mohammad Amjad

    2001-01-01

    A model as well as its numerical method to calculate target strength of rigid body using Lighthill's acoustic analogy approach which developed from the propeller aircraft sound field study have been presented. The cases of ellipsoid target has been used to demonstrate the approach. The comparison of the numerical results with that of analytical formulation provides a satisfactory check for the validity of the approach. Some reasonable results have been discussed. The advantage of the present model is that it is suitable for any arbitrarily shaped rigid body moving with small Mach number.

  17. High strength, tough alloy steel

    Science.gov (United States)

    Thomas, Gareth; Rao, Bangaru V. N.

    1979-01-01

    A high strength, tough alloy steel is formed by heating the steel to a temperature in the austenite range (1000.degree.-1100.degree. C.) to form a homogeneous austenite phase and then cooling the steel to form a microstructure of uniformly dispersed dislocated martensite separated by continuous thin boundary films of stabilized retained austenite. The steel includes 0.2-0.35 weight % carbon, at least 1% and preferably 3-4.5% chromium, and at least one other substitutional alloying element, preferably manganese or nickel. The austenite film is stable to subsequent heat treatment as by tempering (below 300.degree. C.) and reforms to a stable film after austenite grain refinement.

  18. Screening Effect in Charge Qubit

    Institute of Scientific and Technical Information of China (English)

    HUA Ming; XIAO Xiao; GAO Yi-Bo

    2011-01-01

    We study the influence of screening effect on quantum decoherence for charge qubit and the process of quantum information storage. When the flux produced by the circulating current in SQUID loop is considered, screening effect is formally characterized by a LC resonator. Using large-detuning condition and Fr(o)hlich transformation in the qubit-cavity-resonator system, we calculate the decoherence factor for charge qubit and the effective qubit-cavity Hamiltonian. The decoherence factor owns a factorized structure, it shows that screening effect is a resource of decoherence for charge qubit. The effective Hamiltonian shows that the screening effect results in a frequency shift for charge qubit and a modified qubit-cavity coupling constant induced by a LC resonator.

  19. Measurements of W Charge Asymmetry

    Energy Technology Data Exchange (ETDEWEB)

    Holzbauer, J. L. [Mississippi U.

    2015-10-06

    We discuss W boson and lepton charge asymmetry measurements from W decays in the electron channel, which were made using 9.7 fb$^{-1}$ of RunII data collected by the D0 detector at the Fermilab Tevatron Collider. The electron charge asymmetry is presented as a function of pseudo-rapidity out to |$\\eta$| $\\le$ 3.2, in five symmetric and asymmetric kinematic bins of electron transverse momentum and the missing transverse energy of the event. We also give the W charge asymmetry as a function of W boson rapidity. The asymmetries are compared with next-to-leading order perturbative quantum chromodynamics calculations. These charge asymmetry measurements will allow more accurate determinations of the proton parton distribution functions and are the most precise to date.

  20. Induced-charge Electrokinetic Phenomena

    CERN Document Server

    Bazant, M Z; Bazant, Martin Z.; Squires, Todd M.

    2003-01-01

    Motivated by the recent discovery of AC electro-osmosis near micro-electrodes, we predict a broad class of nonlinear electrokinetic phenomena involving induced interfacial charge. By considering various polarizable objects (metals or dielectrics) in DC and AC applied fields, we develop a simple physical picture of `induced-charge electro-osmosis' (ICEO), the fluid slip at a surface due to an electric field acting on the diffuse charge it induces. We also discuss `induced-charge electrophoresis' (ICEP), the analogous motion of a freely-suspended polarizable particle. Both differ significantly from their classical linear counterparts. We present a mathematical theory of ICEO flows in the weakly nonlinear limit of thin double layers. As an example, we calculate the time-dependent ICEO slip around a metallic sphere with a thin dielectric coating in a suddenly-applied DC field. We briefly discuss possible applications of ICEO to microfluidics and of ICEP to colloidal manipulation.

  1. BRST charge for nonlinear algebras

    CERN Document Server

    Buchbinder, I L

    2007-01-01

    We study the construction of the classical nilpotent canonical BRST charge for the nonlinear gauge algebras where a commutator (in terms of Poisson brackets) of the constraints is a finite order polynomial of the constraints.

  2. Organic Text Authors Charge Plagiarism.

    Science.gov (United States)

    Chemical and Engineering News, 1979

    1979-01-01

    Reports on the recent controversy involving two organic chemistry textbooks. The charge of plagiarism and the court litigations are the object of interest in the chemical community since many prominant scientists are planned as witnesses. (SA)

  3. Charge Transport in one dimension

    CERN Document Server

    Holcombe, S R

    2010-01-01

    We consider charge transport in nanopores where the dielectric constant inside the nanopore is much greater than in the surrounding material, so that the flux of the electric fields due to the charges is almost entirely confined to the nanopore. That means that we may model the electric fields due to charge densities in the nanopore in terms of average properties across the nanopore as solutions of one dimensional Poisson equations. We develop basic equations for an M component system using equations of continuity to relate concentrations to currents, and flux equations relating currents to concentration gradients and conductivities. We then derive simplified scaled versions of the equations. We develop exact solutions for the one component case in a variety of boundary conditions using a Hopf-Cole transformation, Fourier series, and periodic solutions of the Burgers equation. These are compared with a simpler model in which the scaled diffusivity is zero so that all charge motion is driven by the electric fi...

  4. Quantum physics: Destruction of discrete charge

    Science.gov (United States)

    Nazarov, Yuli V.

    2016-08-01

    Electric charge is quantized in units of the electron's charge. An experiment explores the suppression of charge quantization caused by quantum fluctuations and supports a long-standing theory that explains this behaviour. See Letter p.58

  5. Multizone Artillery Propelling Charge Studies

    Science.gov (United States)

    1983-05-01

    PROJECT, TASK AREA 4 WORK UNIT NUMBERS IL162618AH80 11. CONTROLLING OFFICE NAME AND ADDRESS US Army Armament Research & Development Command...are affected by the many interrelated components comprising the charge. We have identified areas of concern for bagged multizone charges; studies...B. Brodman DRDAP-LCB-I, D. Spring DRDAR-LCE, R. Walker DRDAR-LCU-CT E. Barrleres R. Davitt DRDAR-CLU-CV C.Mandala E. Moore DRDAR-LCM-E S

  6. Metallic charge stripes in cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, J.M

    2004-08-01

    Some recent evidence for the existence of dynamic, metallic stripes in the 214 family of cuprates is reviewed. The mechanism of stripe pinning is considered, and changes in the charge density within stripes between the pinned and dynamic phases is discussed. From a purely experimental perspective, dynamic charge stripes are fully compatible with nodal 'quasiparticles' and other electronic properties common to all superconducting cuprates.

  7. Metallic charge stripes in cuprates

    Science.gov (United States)

    Tranquada, J. M.

    2004-08-01

    Some recent evidence for the existence of dynamic, metallic stripes in the 214 family of cuprates is reviewed. The mechanism of stripe pinning is considered, and changes in the charge density within stripes between the pinned and dynamic phases is discussed. From a purely experimental perspective, dynamic charge stripes are fully compatible with nodal “quasiparticles” and other electronic properties common to all superconducting cuprates.

  8. Charged-lepton flavour physics

    Indian Academy of Sciences (India)

    Andreas Hoecker

    2012-11-01

    This write-up on a talk at the 2011 Lepton–Photon symposium in Mumbai, India, summarizes recent results in the charged-lepton flavour sector. Searches for charged-lepton flavour violation, lepton electric dipole moments and flavour-conserving CP violation are reviewed here. Recent progress in -lepton physics and in the Standard Model prediction of the muon anomalous magnetic moment is also discussed.

  9. A note on charged interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Luo Huaqiang [Courant Institute of Mathematical Sciences, New York University, New York, NY 10012 (United States); Yu, M Y [Institute for Theoretical Physics I, Ruhr-University, D-44780 Bochum (Germany)

    2006-12-15

    A condition associated with the plasma boundary or other charged interface is reviewed. It is pointed out that in comparing theories and simulations of such interfaces, in order to avoid conflicting results it should be ascertained that the systems under consideration are thermodynamically equivalent. For the plasma-wall interface in equilibrium, the rate of change of the surface-charge density with respect to the surface potential must be positive.

  10. Thermophoresis of charged colloidal particles.

    Science.gov (United States)

    Fayolle, Sébastien; Bickel, Thomas; Würger, Alois

    2008-04-01

    Thermally induced particle flow in a charged colloidal suspension is studied in a fluid-mechanical approach. The force density acting on the charged boundary layer is derived in detail. From Stokes' equation with no-slip boundary conditions at the particle surface, we obtain the particle drift velocity and the thermophoretic transport coefficients. The results are discussed in view of previous work and available experimental data.

  11. Thermophoresis of charged colloidal particles

    OpenAIRE

    Fayolle, Sébastien; Bickel, Thomas; Würger, Alois

    2008-01-01

    International audience; Thermally induced particle flow in a charged colloidal suspension is studied in a fluid-mechanical approach. The force density acting on the charged boundary layer is derived in detail. From Stokes' equation with no-slip boundary conditions at the particle surface, we obtain the particle drift velocity and the thermophoretic transport coefficients. The results are discussed in view of previous work and available experimental data.

  12. Three Important Advances in Engineering Strength Theories

    Institute of Scientific and Technical Information of China (English)

    YuMaohong; FanWen; MitustoshiYoshimine

    2003-01-01

    There are there great advances in the research on engineering strength theories in the latter half of the 20th Century. The first advance was the devel-opment of strength theory from the single-shear strength theory including the Tresca yield criterion and Mohr-Coulomb failure criterion to theoctahe-dral-shear strength theory; the second one was that from the octahedral-shear strength theory to the twin-shear strength theory; and the third wasthe theories from the single criteria to the unifiedstrength theory. These three advances are summa-rized in this paper. It is interesting and useful for re-searchers to choose an appropriate failure criterion in studying the strength of materials and struc-tures, for engineers to correctly use it and for stu-dents to understand strength theory.

  13. The sarcomeric protein nebulin: another multifunctional giant in charge of muscle strength optimization

    Directory of Open Access Journals (Sweden)

    Coen eOttenheijm

    2012-02-01

    Full Text Available The sliding filament model of the sarcomere was developed more than half a century ago. This model, consisting only of thin and thick filaments, has been successful in explaining many, but not all, features of skeletal muscle. Work during the 1980s revealed the existence of two additional filaments: the giant filamentous proteins titin and nebulin. Whereas the role of titin rapidly progressed, nebulin’s role in muscle structure and function remained long nebulous. An important feature of muscle structure and function that has remained relatively obscure concerns the mechanisms that are involved in regulating thin filament length. Filament length is an important aspect of muscle function as force production is proportional to the amount of overlap between thick and thin filaments. Recent advances, due in part to the generation of nebulin KO models, reveal that nebulin plays an important role in the regulation of thin filament length, most likely by stabilizing F-actin assemblies. Another structural feature of skeletal muscle that has been incompletely understood concerns the mechanisms involved in maintaining Z-disk structure and the regular lateral alignment of adjacent sarcomeres during contraction. Recent studies indicate that nebulin is part of a protein complex that mechanically links adjacent myofibrils. In addition to these structural roles in support of myofibrillar force generation, nebulin has been also shown to regulate directly muscle contraction at the level of individual cross bridges: cycling kinetics and the calcium sensitivity of force producing cross-bridges is enhanced in the presence of nebulin. Thus, these recent data all point to nebulin being important for muscle force optimization. Consequently, muscle weakness as the lead symptom develops in the case of patients with nemaline myopathy that have mutations in the nebulin gene. Here, we discuss these important novel insights into the role of nebulin in skeletal muscle function.

  14. The sarcomeric protein nebulin: another multifunctional giant in charge of muscle strength optimization.

    Science.gov (United States)

    Ottenheijm, Coen A C; Granzier, Henk; Labeit, Siegfried

    2012-01-01

    The sliding filament model of the sarcomere was developed more than half a century ago. This model, consisting only of thin and thick filaments, has been successful in explaining many, but not all, features of skeletal muscle. Work during the 1980s revealed the existence of two additional filaments: the giant filamentous proteins titin and nebulin. Whereas the role of titin rapidly progressed, nebulin's role in muscle structure and function remained long nebulous. An important feature of muscle structure and function that has remained relatively obscure concerns the mechanisms that are involved in regulating thin filament length. Filament length is an important aspect of muscle function as force production is proportional to the amount of overlap between thick and thin filaments. Recent advances, due in part to the generation of nebulin KO models, reveal that nebulin plays an important role in the regulation of thin filament length, most likely by stabilizing F-actin assemblies. Another structural feature of skeletal muscle that has been incompletely understood concerns the mechanisms involved in maintaining Z-disk structure and the regular lateral alignment of adjacent sarcomeres during contraction. Recent studies indicate that nebulin is part of a protein complex that mechanically links adjacent myofibrils. In addition to these structural roles in support of myofibrillar force generation, nebulin has been also shown to regulate directly muscle contraction at the level of individual crossbridges: cycling kinetics and the calcium sensitivity of force producing crossbridges is enhanced in the presence of nebulin. Thus, these recent data all point to nebulin being important for muscle force optimization. Consequently, muscle weakness as the lead symptom develops in the case of patients with nemaline myopathy that have mutations in the nebulin gene. Here, we discuss these important novel insights into the role of nebulin in skeletal muscle function.

  15. Spin dipole nuclear matrix elements for double beta decay nuclei by charge-exchange reactions

    CERN Document Server

    Ejiri, H

    2016-01-01

    Spin dipole (SD) strengths for double beta-decay (DBD) nuclei were studied experimentally for the first time by using measured cross sections of (3He,t) charge exchange reactions (CERs). Then SD nuclear matrix elements (NMEs) for low-lying 2- states were derived from the experimental SD strengths by referring to the experimental GT (Gamow-Teller) and F (Fermi) strengths. They are consistent with the empirical SD NMEs based on the quasi-particle model with the empirical effective SD coupling constant. The CERs are used to evaluate the SD NME, which is associated with one of the major components of the neutrino-less DBD NME.

  16. Solar Charged Stand Alone Inverter

    Directory of Open Access Journals (Sweden)

    M.Vasugi

    2014-07-01

    Full Text Available This paper deals with solar powered stand alone inverter which converts the variable dc output of a photovoltaic solar panel into ac that can be fed to loads. Stand alone inverters are used in systems where the inverter get its energy from batteries charged by photo voltaic arrays. A charge controller limits the rate at which electric current is added to or drawn from electric batteries. This charge discharge controller is needed to prevent the battery from being overcharged or discharged thus prolonging its life. The charge/discharge control is necessary in order to achieve safety and increase the capacity of the battery. The project has been tested according its operational purposes. Maximum power rating of the experimented solar charge controller is 100W according battery capacities. Cost effective solar charge controller has been designed and implemented to have efficient system and much longer battery lifetime. The dc output is given to inverter and then it is supplied to loads. This method is very cheap and cost effective.

  17. Electroelasticity of Charged Black Branes

    CERN Document Server

    Armas, Jay; Obers, Niels A

    2013-01-01

    We present the first order corrected dynamics of fluid branes carrying higher-form charge by obtaining the general form of their equations of motion to pole-dipole order. Assuming linear response theory, we characterize the corresponding effective theory of stationary bent charged (an)isotropic fluid branes in terms of two sets of response coefficients, the Young modulus and the piezoelectric moduli. We subsequently find large classes of examples in gravity of this effective theory, by constructing stationary strained charged black brane solutions to first order in a derivative expansion. Using solution generating techniques and bent neutral black branes as a seed solution, we obtain a class of charged black brane geometries carrying smeared Maxwell charge in Einstein-Maxwell-dilaton gravity. In the specific case of ten-dimensional space-time we furthermore use T-duality to generate bent black branes with higher-form charge, including smeared D-branes of type II string theory. By subsequently measuring the be...

  18. Jet charge at the LHC.

    Science.gov (United States)

    Krohn, David; Schwartz, Matthew D; Lin, Tongyan; Waalewijn, Wouter J

    2013-05-24

    Knowing the charge of the parton initiating a light-quark jet could be extremely useful both for testing aspects of the standard model and for characterizing potential beyond-the-standard-model signals. We show that despite the complications of hadronization and out-of-jet radiation such as pileup, a weighted sum of the charges of a jet's constituents can be used at the LHC to distinguish among jets with different charges. Potential applications include measuring electroweak quantum numbers of hadronically decaying resonances or supersymmetric particles, as well as standard model tests, such as jet charge in dijet events or in hadronically decaying W bosons in tt[over ¯] events. We develop a systematically improvable method to calculate moments of these charge distributions by combining multihadron fragmentation functions with perturbative jet functions and pertubative evolution equations. We show that the dependence on energy and jet size for the average and width of the jet charge can be calculated despite the large experimental uncertainty on fragmentation functions. These calculations can provide a validation tool for data independent of Monte Carlo fragmentation models.

  19. Crystal growth of new charge-transfer salts based on π-conjugated donor molecules

    Science.gov (United States)

    Morherr, Antonia; Witt, Sebastian; Chernenkaya, Alisa; Bäcker, Jan-Peter; Schönhense, Gerd; Bolte, Michael; Krellner, Cornelius

    2016-09-01

    New charge transfer crystals of π-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure are reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-Fx, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with π-conjugated donor molecules.

  20. Crystal growth of new charge-transfer salts based on π-conjugated donor molecules

    Energy Technology Data Exchange (ETDEWEB)

    Morherr, Antonia, E-mail: morherr@stud.uni-frankfurt.de [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Witt, Sebastian [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Chernenkaya, Alisa [Graduate School Materials Science in Mainz, 55128 Mainz (Germany); Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz (Germany); Bäcker, Jan-Peter [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Schönhense, Gerd [Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz (Germany); Bolte, Michael [Institut für anorganische Chemie, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany); Krellner, Cornelius [Physikalisches Institut, Goethe-Universität Frankfurt am Main, 60438 Frankfurt am Main (Germany)

    2016-09-01

    New charge transfer crystals of π-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure are reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-F{sub x}, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with π-conjugated donor molecules.

  1. Crystal Growth of new charge-transfer salts based on $\\pi$-conjugated molecules

    CERN Document Server

    Morherr, Antonia; Chernenkaya, Alisa; Bäcker, Jan-Peter; Schönhense, Gerd; Bolte, Michael; Krellner, Cornelius

    2016-01-01

    New charge transfer crystals of $\\pi$-conjugated, aromatic molecules (phenanthrene and picene) as donors were obtained by physical vapor transport. The melting behavior, optimization of crystal growth and the crystal structure is reported for charge transfer salts with (fluorinated) tetracyanoquinodimethane (TCNQ-F$_x$, x=0, 2, 4), which was used as acceptor material. The crystal structures were determined by single-crystal X-ray diffraction. Growth conditions for different vapor pressures in closed ampules were applied and the effect of these starting conditions for crystal size and quality is reported. The process of charge transfer was investigated by geometrical analysis of the crystal structure and by infrared spectroscopy on single crystals. With these three different acceptor strengths and the two sets of donor materials, it is possible to investigate the distribution of the charge transfer systematically. This helps to understand the charge transfer process in this class of materials with $\\pi$-conjug...

  2. Asteroid airburst altitude vs. strength

    Science.gov (United States)

    Robertson, Darrel; Wheeler, Lorien; Mathias, Donovan

    2016-10-01

    Small NEO asteroids (<Ø140m) may not be a threat on a national or global level but can still cause a significant amount of local damage as demonstrated by the Chelyabinsk event where there was over $33 million worth of damage (1 billion roubles) and 1500 were injured, mostly due to broken glass. The ground damage from a small asteroid depends strongly on the altitude at which they "burst" where most of the energy is deposited in the atmosphere. The ability to accurately predict ground damage is useful in determining appropriate evacuation or shelter plans and emergency management.Strong asteroids, such as a monolithic boulder, fail and create peak energy deposition close to the altitude at which ram dynamic pressure exceeds the material cohesive strength. Weaker asteroids, such as a rubble pile, structurally fail at higher altitude, but it requires the increased aerodynamic pressure at lower altitude to disrupt and disperse the rubble. Consequently the resulting airbursts have a peak energy deposition at similar altitudes.In this study hydrocode simulations of the entry and break-up of small asteroids were performed to examine the effect of strength, size, composition, entry angle, and speed on the resulting airburst. This presentation will show movies of the simulations, the results of peak burst height, and the comparison to semi-analytical models.

  3. Muscle strength in patients with chronic pain

    NARCIS (Netherlands)

    van Wilgen, C.P.; Akkerman, L.; Wieringa, J.; Dijkstra, P.U.

    2003-01-01

    Objective: To analyse the influence of chronic pain on muscle strength. Design: Muscle strength of patients with unilateral nonspecific chronic pain, in an upper or lower limb, were measured according to a standardized protocol using a hand-held dynamometer. Before and after muscle strength measurem

  4. Strengths and Satisfaction across the Adult Lifespan

    Science.gov (United States)

    Isaacowitz, Derek M.; Vaillant, George E.; Seligman, Martin E. P.

    2003-01-01

    Positive psychology has recently developed a classification of human strengths (Peterson & Seligman, in press). We aimed to evaluate these strengths by investigating the strengths and life satisfaction in three adult samples recruited from the community (young adult, middle-aged, and older adult), as well as in the surviving men of the Grant study…

  5. 14 CFR 31.27 - Strength.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Strength. 31.27 Section 31.27 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Strength Requirements § 31.27 Strength. (a) The structure must be able...

  6. Improving the toughness of ultrahigh strength steel

    Energy Technology Data Exchange (ETDEWEB)

    Soto, Koji

    2002-08-15

    The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the toughening mechanism of the Fe/Co/Ni/Cr/Mo/C steel, AerMet 100, which has the highest toughness/strength combination among all commercial ultrahigh strength steels. The possibility of improving the toughness of this steel was examined by considering several relevant factors.

  7. Tentative study of nuclear charge radii for neutron-deficient nuclei around the Z = 82 shell from experimental α decay data

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Yibin, E-mail: qyibin@njust.edu.cn [Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094 (China); Department of Physics and Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China); Ren, Zhongzhou [Department of Physics and Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy-Ion Accelerator, Lanzhou 730000 (China); Kavli Institute for Theoretical Physics China, Beijing 100190 (China)

    2016-01-15

    We tentatively investigate the root-mean-square (rms) nuclear charge radii of odd-A Po and Pb isotopes plus Tl isotopes, particularly concerning these difficultly-detected nuclei along with short lifetimes, via various data on α decay. Within the density-dependent cluster model, the density distributions of studied daughter nuclei are determined by exactly reproducing the corresponding experimental α decay half-lives, which leads the final results of nuclear charge radii. In addition, our recently proposed formula deducing the charge radii is extended to this study for comparison. Whether it concerns the ground or isomeric state of target nuclei, the extracted nuclear charge radii are found to be in good agreement with the measured values. Sequential predictions on the rms charge radii are subsequently made for these neutron-deficient nuclei and especially for the rarely detected Bi isotopic chain, which are expected to be useful for future measurements. Moreover, the variety of α-preformation factors is analyzed in the scheme of valence nucleon number to pursue the further improvement of the model. This may be considered as an effective effort to obtain the charge radii of ground and even low-lying excited states for exotic nuclei near the proton-dripline.

  8. Density-dependent photoabsorption cross sections of atomic Xe

    Institute of Scientific and Technical Information of China (English)

    Ma Xiao-Guang

    2009-01-01

    The evolution of the photoabsorption cross sections of atomic xenon with number densities varying from ideal gas to condensed matter has been studied by an alternative view in the present work. The alternative expressions of the photoabsorption cross sections presented by Sun et al recently were used with the local field models that has proven to be generalized easily to multiatomic systems including molecules and condensed phase systems. The present results show that the variation of the photoabsorption cross sections of atomic xenon in the giant resonance region from the isolated to the condensed conditions is very small, which agrees well with the variation law of the solid and gas experiments.

  9. 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.

  10. Density-dependent vulnerability of forest ecosystems to drought

    Science.gov (United States)

    Bottero, Alessandra; D'Amato, Anthony W.; Palik, Brian J.; Bradford, John B.; Fraver, Shawn; Battaglia, Mike A.; Asherin, Lance A.

    2017-01-01

    1. Climate models predict increasing drought intensity and frequency for many regions, which may have negative consequences for tree recruitment, growth and mortality, as well as forest ecosystem services. Furthermore, practical strategies for minimizing vulnerability to drought are limited. Tree population density, a metric of tree abundance in a given area, is a primary driver of competitive intensity among trees, which influences tree growth and mortality. Manipulating tree population density may be a mechanism for moderating drought-induced stress and growth reductions, although the relationship between tree population density and tree drought vulnerability remains poorly quantified, especially across climatic gradients.2. In this study, we examined three long-term forest ecosystem experiments in two widely distributed North American pine species, ponderosa pine Pinus ponderosa (Lawson & C. Lawson) and red pine Pinus resinosa (Aiton), to better elucidate the relationship between tree population density, growth and drought. These experiments span a broad latitude and aridity range and include tree population density treatments that have been purposefully maintained for several decades. We investigated how tree population density influenced resistance (growth during drought) and resilience (growth after drought compared to pre-drought growth) of stand-level growth during and after documented drought events.3. Our results show that relative tree population density was negatively related to drought resistance and resilience, indicating that trees growing at lower densities were less vulnerable to drought. This result was apparent in all three forest ecosystems, and was consistent across species, stand age and drought intensity.4. Synthesis and applications. Our results highlighted that managing pine forest ecosystems at low tree population density represents a promising adaptive strategy for reducing the adverse impacts of drought on forest growth in coming decades. Nonetheless, the broader applicability of our findings to other types of forest ecosystems merits additional investigation.

  11. Density dependence, whitebark pine, and vital rates of grizzly bears

    Science.gov (United States)

    van Manen, Frank T.; Haroldson, Mark A.; Bjornlie, Daniel D; Ebinger, Michael R.; Thompson, Daniel J.; Costello, Cecily M; White, Gary C.

    2016-01-01

    Understanding factors influencing changes in population trajectory is important for effective wildlife management, particularly for populations of conservation concern. Annual population growth of the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem, USA has slowed from 4.2–7.6% during 1983–2001 to 0.3–2.2% during 2002–2011. Substantial changes in availability of a key food source and bear population density have occurred. Whitebark pine (Pinus albicaulis), the seeds of which are a valuable but variable fall food for grizzly bears, has experienced substantial mortality primarily due to a mountain pine beetle (Dendroctonus ponderosae) outbreak that started in the early 2000s. Positive growth rates of grizzly bears have resulted in populations reaching high densities in some areas and have contributed to continued range expansion. We tested research hypotheses to examine if changes in vital rates detected during the past decade were more associated with whitebark pine decline or, alternatively, increasing grizzly bear density. We focused our assessment on known-fate data to estimate survival of cubs-of-the-year (cubs), yearlings, and independent bears (≥2 yrs), and reproductive transition of females from having no offspring to having cubs. We used spatially and temporally explicit indices for grizzly bear density and whitebark pine mortality as individual covariates. Models indicated moderate support for an increase in survival of independent male bears over 1983–2012, whereas independent female survival did not change. Cub survival, yearling survival, and reproductive transition from no offspring to cubs all changed during the 30-year study period, with lower rates evident during the last 10–15 years. Cub survival and reproductive transition were negatively associated with an index of grizzly bear density, indicating greater declines where bear densities were higher. Our analyses did not support a similar relationship for the index of whitebark pine mortality. The results of our study support the interpretation that slowing of population growth during the last decade was associated more with increasing grizzly bear density than the decline in whitebark pine. Grizzly bear density and its potential effect on vital rates and population trajectory warrant consideration for management of the grizzly bear population in the Greater Yellowstone Ecosystem.

  12. A Schematic Model For Density-Dependent Vector Meson Masses

    CERN Document Server

    Kim, Y; Brown, G E; Rho, M; Kim, Youngman; Rho, Mannque

    1999-01-01

    A schematic two-level model consisting of a "collective" bosonic state and an "elementary" meson is constructed that provides interpolation from a hadronic description (a la Rapp/Wambach) to B/R scaling for the description of properties of vector mesons in dense medium. The development is based on a close analogy to the degenerate schematic model of Brown for giant resonances in nuclei.

  13. Ionic strength dependent vesicle adsorption and phase behavior of anionic phospholipids on a gold substrate.

    Science.gov (United States)

    Pramanik, Sumit Kumar; Seneca, Senne; Ethirajan, Anitha; Neupane, Shova; Renner, Frank Uwe; Losada-Pérez, Patricia

    2016-03-08

    The authors report on the effect of ionic strength on the formation of supported vesicle layers of anionic phospholipids 1,2-dimyristoyl-sn-glycero-3-phospho-rac-glycerol (DMPG) and dimyristoylphosphatidylserine (DMPS) onto gold. Using quartz crystal microbalance with dissipation monitoring the authors show that vesicle adsorption is mainly governed by NaCl concentration, reflecting the importance of electrostatic interactions in anionic lipids, as compared to zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine. At low ionic strength, low or no adsorption is observed as a result of vesicle-vesicle electrostatic repulsion. At medium ionic strength, the negative charges of DMPG and DMPS are screened resulting in larger adsorption and a highly dissipative intact vesicle layer. In addition, DMPS exhibits a peculiar behavior at high ionic strength that depends on the temperature of the process.

  14. Numeric description of space charge in polyethylene under ac electric fields

    Science.gov (United States)

    Zhao, J.; Xu, Z.; Chen, G.; Lewin, P. L.

    2010-12-01

    Space charge in polyethylene-based insulation materials and its effect on the local electric field under a dc environment have been extensively examined over the last few decades while the behavior of space charge under ac stress has received less attention. Space charge phenomenon under ac electric fields becomes an important issue with increased operating field strength in many applications, such as next generation high voltage cables. In this paper, a bipolar charge transport model has been developed to simulate space charge in polymers under ac electric fields. Obtained simulation results show that there is a small quantity of phase-dependent bipolar charge accumulation in the vicinity of the electrodes that does not move into the bulk under ac stress. This causes a slight distortion of the local field in the bulk. However, at lower frequencies less than 1 Hz, there is increased charge accumulation and penetration. Comparison with available experimental data suggests that the model is capable of describing the underlying physics of charge behavior when a dielectric material is subjected to ac electric fields. Due to the weak charge movement in the bulk, the conduction current density is small and hence the displacement component dominates the total current density and this increases linearly with ac frequency.

  15. Magnetically Induced "Dry" Water Like Structure of Charged Fluid at the Core of a Magnetar

    CERN Document Server

    Ghosh, S; Ghosh, Sutapa; Chakrabarty, Somenath

    2001-01-01

    It is shown that charged fluid, e.g., electron gas or proton matter at the core of a magnetar exhibit super-fluid (frictionless) like property if the magnetic field strength is high enough to populate only the zeroth Landau levels.

  16. On Landau damping of dipole modes by non-linear space charge and octupoles

    CERN Document Server

    Möhl, D

    1995-01-01

    The joint effect of space-charge non-linearities and octupole lenses is important for Landau damping of coherent instabilities. The octupole strength required for stabilisation can depend strongly on the sign of the excitation current of the lenses. This note tries to extend results, previously obtained for coasting beams and rigid bunches, to more general head--tail modes.

  17. Epoxy Based Nanodielectrics for High Voltage DC Applications: Synthesis, Dielectric Properties and Space Charge Dynamics

    NARCIS (Netherlands)

    Andritsch, T.M.

    2010-01-01

    Main goal of the research described in this PhD thesis was to determine the influences of filler size, material and distribution on the DC breakdown strength, permittivity and space charge behaviour of nanocomposites. This should lay the groundwork for tailored insulation materials for HVDC applicat

  18. Colloidal Charge Determination in Concentrated Liquid Dispersions Using Torsional Resonance Oscillation

    NARCIS (Netherlands)

    Bergenholtz, J.; Willenbacher, N.; Wagner, N.J.; Morrison, B.; Ende, van den D.; Mellema, J.

    1998-01-01

    The high-frequency rheology of concentrated liquid charge-stabilized dispersions has been measured using a surface-loaded torsional resonator. The high-frequency shear moduli are extracted from the measurement as a function of ionic strength and surface acid content. A theory which enables the deter

  19. Strength dynamics of weighted evolving networks

    Institute of Scientific and Technical Information of China (English)

    Wu Jian-Jun; Gao Zi-You; Sun Hui-Jun

    2007-01-01

    In this paper, a simple model for the strength dynamics of weighted evolving networks is proposed to characterize the weighted networks. By considering the congestion effects, this approach can yield power law strength distribution appeared on the many real weighted networks, such as traffic networks, internet networks. Besides, the relationship between strength and degree is given. Numerical simulations indicate that the strength distribution is strongly related to the strength dynamics decline. The model also provides us with a better description of the real weighted networks.

  20. Cobalt: for strength and color

    Science.gov (United States)

    Boland, Maeve A.; Kropschot, S.J.

    2011-01-01

    Cobalt is a shiny, gray, brittle metal that is best known for creating an intense blue color in glass and paints. It is frequently used in the manufacture of rechargeable batteries and to create alloys that maintain their strength at high temperatures. It is also one of the essential trace elements (or "micronutrients") that humans and many other living creatures require for good health. Cobalt is an important component in many aerospace, defense, and medical applications and is a key element in many clean energy technologies. The name cobalt comes from the German word kobold, meaning goblin. It was given this name by medieval miners who believed that troublesome goblins replaced the valuable metals in their ore with a substance that emitted poisonous fumes when smelted. The Swedish chemist Georg Brandt isolated metallic cobalt-the first new metal to be discovered since ancient times-in about 1735 and identified some of its valuable properties.

  1. Space charges can significantly affect the dynamics of accelerator maps

    Science.gov (United States)

    Bountis, Tassos; Skokos, Charalampos

    2006-10-01

    Space charge effects can be very important for the dynamics of intense particle beams, as they repeatedly pass through nonlinear focusing elements, aiming to maximize the beam's luminosity properties in the storage rings of a high energy accelerator. In the case of hadron beams, whose charge distribution can be considered as “frozen” within a cylindrical core of small radius compared to the beam's dynamical aperture, analytical formulas have been recently derived [C. Benedetti, G. Turchetti, Phys. Lett. A 340 (2005) 461] for the contribution of space charges within first order Hamiltonian perturbation theory. These formulas involve distribution functions which, in general, do not lead to expressions that can be evaluated in closed form. In this Letter, we apply this theory to an example of a charge distribution, whose effect on the dynamics can be derived explicitly and in closed form, both in the case of 2-dimensional as well as 4-dimensional mapping models of hadron beams. We find that, even for very small values of the “perveance” (strength of the space charge effect) the long term stability of the dynamics changes considerably. In the flat beam case, the outer invariant “tori” surrounding the origin disappear, decreasing the size of the beam's dynamical aperture, while beyond a certain threshold the beam is almost entirely lost. Analogous results in mapping models of beams with 2-dimensional cross section demonstrate that in that case also, even for weak tune depressions, orbital diffusion is enhanced and many particles whose motion was bounded now escape to infinity, indicating that space charges can impose significant limitations on the beam's luminosity.

  2. Space charges can significantly affect the dynamics of accelerator maps

    Energy Technology Data Exchange (ETDEWEB)

    Bountis, Tassos [Department of Mathematics, University of Patras, GR-26500 Patras (Greece) and Center for Research and Applications of Nonlinear Systems (CRANS), University of Patras, GR-26500 Patras (Greece)]. E-mail: tassos50@otenet.gr; Skokos, Charalampos [Center for Research and Applications of Nonlinear Systems (CRANS), University of Patras, GR-26500 Patras (Greece)

    2006-10-09

    Space charge effects can be very important for the dynamics of intense particle beams, as they repeatedly pass through nonlinear focusing elements, aiming to maximize the beam's luminosity properties in the storage rings of a high energy accelerator. In the case of hadron beams, whose charge distribution can be considered as 'frozen' within a cylindrical core of small radius compared to the beam's dynamical aperture, analytical formulas have been recently derived [C. Benedetti, G. Turchetti, Phys. Lett. A 340 (2005) 461] for the contribution of space charges within first order Hamiltonian perturbation theory. These formulas involve distribution functions which, in general, do not lead to expressions that can be evaluated in closed form. In this Letter, we apply this theory to an example of a charge distribution, whose effect on the dynamics can be derived explicitly and in closed form, both in the case of 2-dimensional as well as 4-dimensional mapping models of hadron beams. We find that, even for very small values of the 'perveance' (strength of the space charge effect) the long term stability of the dynamics changes considerably. In the flat beam case, the outer invariant 'tori' surrounding the origin disappear, decreasing the size of the beam's dynamical aperture, while beyond a certain threshold the beam is almost entirely lost. Analogous results in mapping models of beams with 2-dimensional cross section demonstrate that in that case also, even for weak tune depressions, orbital diffusion is enhanced and many particles whose motion was bounded now escape to infinity, indicating that space charges can impose significant limitations on the beam's luminosity.

  3. Strength Distribution Analysis of Typical Staple Fibers

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The strength of staple fiber is an important property for yarns and fabrics. Usually there are variations in individual fiber strength, and this will affect the final strength of yarns and fabrics. In this study, Weibull distribution function is used to analyze the strength distribution of various staplefibers. The strengths of wool, silk, cotton, flax, acrylic, polyester, glass, aramid and carbon fiber are tested. It isfound that the strengths of cotton, polyester, glass, aramid and carbon fiber fit well with the two-factor Weibulldistribution, while those of wool and silk with the threefactir Weibull distribution. However, the strength distributionof flax cannot be expressed by either two- or three-factor Weibull distribution convincingly.

  4. Molecular Weight and Charge Density Asymmetry in Polyelectrolyte Complexation

    Science.gov (United States)

    Audus, Debra; Fredrickson, Glenn; Duechs, Dominik

    2009-03-01

    We investigate the phase diagram of oppositely charged polymers in a good solvent using a field-theoretic model. Mean-field solutions fail to predict the experimentally observed macroscopic phase separation into a solvent-rich phase and a dense liquid aggregate of polymers - a ``complex coacervate.'' We therefore study the model within a one-loop approximation, which accounts for Gaussian fluctuations in electrostatic and chemical potentials. Our particular focus is the effect of molecular weight, ionic strength, and charge asymmetry on the phase envelope. A set of dimensionless parameters is identified that dictate the size and shape of the two-phase region. Our results should be helpful in guiding experimental studies of coacervation.

  5. Neutral and positively charged excitons in narrow quantum ring

    Energy Technology Data Exchange (ETDEWEB)

    Porras Monroy, L. C.; Rodríguez-Prada, F. A.; Mikhailov, I. D. [Escuela de Física, Universidad Industrial de Santander, A. A. 678, Bucaramanga (Colombia)

    2014-05-15

    We study theoretically quantized states of a neutral and a positively charged exciton (trion X{sup +}) confined in a heterostructure with the ring-like geometry. In order to assess the experimentally relevant domain of parameters, we adopt a simple model of a narrow ring when 3D wave equations for the neutral and positively charged excitons can be separated. By using the Fourier series method, we have calculated the energy spectra of excitons complexes in a quantum ring as a function of the electron-to-hole mass ratio, the ring radius, and the magnetic field strength. The quantum-size effect and the size-dependent magnetic oscillations of energy levels of excitons' complexes spectra have been revealed.

  6. Problems in point charge electrodynamics

    CERN Document Server

    Ferris, Michael R

    2013-01-01

    (Shortened due to character limit) This thesis consists of two parts. In part I we consider a discrepancy in the derivation of the electromagnetic self force for a point charge. In the point charge framework the self force can be defined as an integral of the Lienard-Wiechert stress 3-forms over a suitably defined worldtube. We show the Schott term may be obtained using a null displacement vector to define the worldtube providing certain conditions are realized. Part II comprises an investigation into a problem in accelerator physics. In a high energy accelerator the cross-section of the beampipe is not continuous and there exist geometric discontinuities such as collimators and cavities. When a relativistic bunch of particles passes such a discontinuity the field generated by a leading charge can interact with the wall and consequently affect the motion of trailing charges. The fields acting on the trailing charges are known as (geometric) wakefields. We model a bunch of particles as a one dimensional contin...

  7. The Distribution of Subjective Memory Strength: List Strength and Response Bias

    Science.gov (United States)

    Criss, Amy H.

    2009-01-01

    Models of recognition memory assume that memory decisions are based partially on the subjective strength of the test item. Models agree that the subjective strength of targets increases with additional time for encoding however the origin of the subjective strength of foils remains disputed. Under the fixed strength assumption the distribution of…

  8. The Mean Remaining Strength Of Systems In A Stress-Strength Model

    OpenAIRE

    Gürler, Selma

    2014-01-01

    In this paper, we study the mean remaining strength of a component inthe stress-strength setup. We present the models for the mean remaining strength for systems consisting of n independent components underthe k-out-of-n:F , parallel and series configurations. We assume thatthe strengths of the components are nonidentically distributed randomvariables and components are designed under the common stress.

  9. Correlation between the strength of glass ionomer cements and their bond strength to bovine teeth.

    Science.gov (United States)

    Hibino, Yasushi; Kuramochi, Ken-ichi; Harashima, Atsushi; Honda, Muneaki; Yamazaki, Atsushi; Nagasawa, Yuko; Yamaga, Taniichiro; Nakajima, Hiroshi

    2004-12-01

    This study examined the possible correlation between the strength of glass ionomers and their adhesive strength to bovine teeth. The shear bond strengths of three different brands of glass ionomer mixed at four different P/L ratios to bovine teeth were measured 24 hours after the cement specimens were prepared. The correlation between shear bond strength and mechanical strength reported in our previous study was also examined. No significant (p > 0.05) increases in the bond strength to bovine teeth were found in any of the cements when the mixing ratio increased. The present study showed no significant (p > 0.05) correlation between mechanical strength of cement and its bond strength to bovine teeth. Rather than trying to increase the strength of the cement, it would be more effective to enhance the adhesive bond strength through procedures such as surface conditioning or cleaning of the tooth structure when glass ionomers are used as luting agents.

  10. Coaxial charged particle energy analyzer

    Science.gov (United States)

    Kelly, Michael A. (Inventor); Bryson, III, Charles E. (Inventor); Wu, Warren (Inventor)

    2011-01-01

    A non-dispersive electrostatic energy analyzer for electrons and other charged particles having a generally coaxial structure of a sequentially arranged sections of an electrostatic lens to focus the beam through an iris and preferably including an ellipsoidally shaped input grid for collimating a wide acceptance beam from a charged-particle source, an electrostatic high-pass filter including a planar exit grid, and an electrostatic low-pass filter. The low-pass filter is configured to reflect low-energy particles back towards a charged particle detector located within the low-pass filter. Each section comprises multiple tubular or conical electrodes arranged about the central axis. The voltages on the lens are scanned to place a selected energy band of the accepted beam at a selected energy at the iris. Voltages on the high-pass and low-pass filters remain substantially fixed during the scan.

  11. Charged Higgs Analysis in CMS

    CERN Document Server

    Eysermans, Jan

    2016-01-01

    In this talk an overview is given of the possible searches of the Charged Higgs Boson during run 2 of the LHC data taking period. The Charged Higgs boson emerges in several (minimal) Standard Model (SM) extensions such as the 2 Doublet Higgs Model, which predicts 5 physical Higgs bosons, consistent with the SM Higgs boson. Based on the main production and decay modes, the possible intermediate and final state particles are predicted for a Charged Higgs mass higher than the top quark mass ($m_{H^{\\pm}} > m_t$). In particular, the dominant H to tau nu and H to tb channels are discussed in more detail together with their associated background.

  12. Charging transient in polyvinyl formal

    Indian Academy of Sciences (India)

    P K Khare; P L Jain; R K Pandey

    2001-08-01

    In the present paper charging and discharging transient currents in polyvinyl formal (PVF) were measured as a function of temperatures (40–80°C), poling fields (9.0 × 103–9.0 × 104 V/cm) and electrode combinations (Al–Al, Au–Al, Zn–Al, Bi–Al, Cu–Al and Ag–Al). The current–time characteristics have different values of slope lying between 0.42–0.56 and 1.42–1.63. The polarization is considered to be due to dipolar reorientation associated with structural motions and space charge relaxations due to trapping of injected charge carriers in energetically distributed traps.

  13. 47 CFR 69.124 - Interconnection charge.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Interconnection charge. 69.124 Section 69.124... Computation of Charges § 69.124 Interconnection charge. (a) Until December 31, 2001, local exchange carriers not subject to price cap regulation shall assess an interconnection charge expressed in dollars...

  14. 75 FR 7411 - Schedule of Water Charges

    Science.gov (United States)

    2010-02-19

    ... COMMISSION 18 CFR Part 410 Schedule of Water Charges AGENCY: Delaware River Basin Commission. ACTION: Notice... Regulations--Water Supply Charges to revise the schedule of water charges. DATES: The Commission will hold a... the subject line ``Schedule of Water Charges.'' FOR FURTHER INFORMATION, CONTACT: Please contact...

  15. 76 FR 10233 - Schedule of Water Charges

    Science.gov (United States)

    2011-02-24

    ... COMMISSION 18 CFR Part 420 Schedule of Water Charges AGENCY: Delaware River Basin Commission. ACTION: Final...--Water Supply Charges. Accordingly, the Commission's water charging rates for consumptive use and non.... FOR FURTHER INFORMATION CONTACT: For questions about the water charging program, please contact...

  16. Structural control of metamaterial oscillator strength and electric field enhancement at terahertz frequencies

    DEFF Research Database (Denmark)

    Keiser, G. R.; Seren, H. R.; Strikwerda, Andrew C.;

    2014-01-01

    The design of artificial nonlinear materials requires control over internal resonant charge densities and local electric field distributions. We present a MM design with a structurally controllable oscillator strength and local electric field enhancement at terahertz frequencies. The MM consists...... of a split ring resonator (SRR) array stacked above an array of closed conducting rings. An in-plane, lateral shift of a half unit cell between the SRR and closed ring arrays results in an increase of the MM oscillator strength by a factor of 4 and a 40% change in the amplitude of the resonant electric field...

  17. Coulomb field strength measurement by electro-optic spectral decoding system at the CALIFES beam line

    CERN Document Server

    Pan, R; Lefevre, T; Gillepsie, WA; CERN. Geneva. ATS Department

    2015-01-01

    Electro-optic (EO) techniques are increasingly used for longitudinal bunch profile measurements. A bunch profile monitor, based on electro-optic spectral decoding(EOSD), has been developed and demonstrated on the CALIFES beam line at CERN. The EO response is analysed using a frequency domain description, and two methods for extraction of absolute Coulomb field strengths from the electron bunch are demonstrated. Measurements at field strengths up to 1.3 MV/m agree with the expectation based on independent charge measurements.

  18. Nanotribology of charged polymer brushes

    Science.gov (United States)

    Klein, Jacob

    Polymers at surfaces, whose modern understanding may be traced back to early work by Sam Edwards1, have become a paradigm for modification of surface properties, both as steric stabilizers and as remarkable boundary lubricants2. Charged polymer brushes are of particular interest, with both technological implications and especially biological relevance where most macromolecules are charged. In the context of biolubrication, relevant in areas from dry eye syndrome to osteoarthritis, charged polymer surface phases and their complexes with other macromolecules may play a central role. The hydration lubrication paradigm, where tenaciously-held yet fluid hydration shells surrounding ions or zwitterions serve as highly-efficient friction-reducing elements, has been invoked to understand the excellent lubrication provided both by ionized3 and by zwitterionic4 brushes. In this talk we describe recent advances in our understanding of the nanotribology of such charged brush systems. We consider interactions between charged end-grafted polymers, and how one may disentangle the steric from the electrostatic surface forces5. We examine the limits of lubrication by ionized brushes, both synthetic and of biological origins, and how highly-hydrated zwitterionic chains may provide extremely effective boundary lubrication6. Finally we describe how the lubrication of articular cartilage in the major joints, a tribosystem presenting some of the greatest challenges and opportunities, may be understood in terms of a supramolecular synergy between charged surface-attached polymers and zwitterionic groups7. Work supported by European Research Council (HydrationLube), Israel Science Foundation (ISF), Petroleum Research Fund of the American Chemical Society, ISF-NSF China Joint Program.

  19. Charge Qubit-Atom Hybrid

    CERN Document Server

    Yu, Deshui; Hufnagel, C; Kwek, L C; Amico, Luigi; Dumke, R

    2016-01-01

    We investigate a novel hybrid system of a superconducting charge qubit interacting directly with a single neutral atom via electric dipole coupling. Interfacing of the macroscopic superconducting circuit with the microscopic atomic system is accomplished by varying the gate capacitance of the charge qubit. To achieve strong interaction, we employ two Rydberg states with an electric-dipole-allowed transition, which alters the polarizability of the dielectric medium of the gate capacitor. Sweeping the gate voltage with different rates leads to a precise control of hybrid quantum states. Furthermore, we show a possible implementation of a universal two-qubit gate.

  20. Static Charge Development on Explosives .

    Directory of Open Access Journals (Sweden)

    K. Raha

    1991-01-01

    Full Text Available Static charge development character of some of the important explosive crystals have been predicted on the basis of their crystal class and symmetry. Among the important mechanism of charge development, the piezoelectric and pyroelectric characters have been considered. Ammonium trinitrate, ammonium nitrate, m-dinitro-benzene, trinitro-toluene, styphnic acid, beeta-lead styphnate, 4,4'dinitro-dipheny1, a-hexamethylenetetranitramine, nitroguanidine, picric acid, dimethylnitramine, a-lead azide and beeta-lead azide are pyroelectric in nature, whereas pentaerythritol tetranitrate, picryliodide, hexamethylenetranitramine, tetranitromethane and trinitroethane are piezoelectric in nature.