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Sample records for chemical signal gradients

  1. Gradient Bundle Analysis: A Full Topological Approach to Chemical Bonding

    CERN Document Server

    Morgenstern, Amanda

    2016-01-01

    The "chemical bond" is a central concept in molecular sciences, but there is no consensus as to what a bond actually is. Therefore, a variety of bonding models have been developed, each defining the structure of molecules in a different manner with the goal of explaining and predicting chemical properties. This thesis describes the initial development of gradient bundle analysis (GBA), a chemical bonding model that creates a high resolution picture of chemical interactions within the charge density framework. GBA is based on concepts from the quantum theory of atoms in molecules (QTAIM), but uses a more complete picture of the topology and geometry of the electron charge density to understand and predict bonding interactions. Gradient bundles are defined as volumes bounded by zero-flux surfaces (ZFSs) in the gradient of the charge density with well-defined energies. The structure of gradient bundles provides an avenue for detecting the locations of valence electrons, which correspond to reactive regions in a ...

  2. Combinatorial MAPLE gradient thin film assemblies signalling to human osteoblasts

    International Nuclear Information System (INIS)

    There is increased interest in smart bioactive materials to control tissue regeneration for the engineering of cell instructive scaffolds. We introduced combinatorial matrix-assisted pulsed laser evaporation (C-MAPLE) as a new method for the fabrication of organic thin films with a compositional gradient. Synchronized C-MAPLE of levan and oxidized levan was employed to assemble a two-compound biopolymer film structure. The gradient of the film composition was validated by fluorescence microscopy. In this study, we investigated the cell response induced by the compositional gradient using imaging of early osteoblast attachment and analysis of signalling phosphoprotein expression. Cells attached along the gradient in direct proportion to oxidized levan concentration. During this process distinct areas of the binary gradient have been shown to modulate the osteoblasts’ extracellular signal-regulated kinase signalling with different propensity. The proposed fabrication method results in the preparation of a new bioactive material, which could control the cell signalling response. This approach can be extended to screen new bioactive interfaces for tissue regeneration. (papers)

  3. Combinatorial MAPLE gradient thin film assemblies signalling to human osteoblasts.

    Science.gov (United States)

    Axente, Emanuel; Sima, Felix; Elena Sima, Livia; Erginer, Merve; Eroglu, Mehmet S; Serban, Natalia; Ristoscu, Carmen; Petrescu, Stefana M; Toksoy Oner, Ebru; Mihailescu, Ion N

    2014-09-01

    There is increased interest in smart bioactive materials to control tissue regeneration for the engineering of cell instructive scaffolds. We introduced combinatorial matrix-assisted pulsed laser evaporation (C-MAPLE) as a new method for the fabrication of organic thin films with a compositional gradient. Synchronized C-MAPLE of levan and oxidized levan was employed to assemble a two-compound biopolymer film structure. The gradient of the film composition was validated by fluorescence microscopy. In this study, we investigated the cell response induced by the compositional gradient using imaging of early osteoblast attachment and analysis of signalling phosphoprotein expression. Cells attached along the gradient in direct proportion to oxidized levan concentration. During this process distinct areas of the binary gradient have been shown to modulate the osteoblasts' extracellular signal-regulated kinase signalling with different propensity. The proposed fabrication method results in the preparation of a new bioactive material, which could control the cell signalling response. This approach can be extended to screen new bioactive interfaces for tissue regeneration. PMID:24867882

  4. A thermodynamic force generated by chemical gradient and adsorption reaction

    CERN Document Server

    Sugawara, Takeshi

    2009-01-01

    Biological units such as macromolecules, organelles, and cells are directed to a proper location under gradients of relevant chemicals. By considering a macroscopic element that has binding sites for a chemical adsorption reaction to occur on its surface, we show the existence of a thermodynamic force that is generated by the gradient and exerted on the element. By assuming local equilibrium and adopting the grand potential from thermodynamics, we derive a formula for such a thermodynamic force, which depends on the chemical potential gradient and Langmuir isotherm. The conditions under which the formula can be applied are demonstrated to hold in intracellular reactions. The role of the force in the partitioning of bacterial chromosome/plasmid during cell division is discussed.

  5. Revisiting the involvement of signaling gradients in somitogenesis.

    Science.gov (United States)

    Mallo, Moisés

    2016-04-01

    During embryonic development, formation of individual vertebrae requires that the paraxial mesoderm becomes divided into regular segmental units known as somites. Somites are sequentially formed at the anterior end of the presomitic mesoderm (PSM) resulting from functional interactions between the oscillatory activity of signals promoting segmentation and a moving wavefront of tissue competence to those signals, eventually generating a constant flow of new somites at regular intervals. According to the current model for somitogenesis, the wavefront results from the combined activity of two opposing functional gradients in the PSM involving the Fgf, Wnt and retinoic acid (RA) signaling pathways. Here, I use published data to evaluate the wavefront model. A critical analysis of those studies seems to support a role for Wnt signaling, but raise doubts regarding the extent to which Fgf and RA signaling contribute to this process. PMID:26662366

  6. Chemical Abundance Gradients in the Star-forming Ring Galaxies

    Science.gov (United States)

    Korchagin, Vladimir; Vorobyov, Eduard; Mayya, Y. D.

    1999-09-01

    Ring waves of star formation, propagating outward in the galactic disks, leave chemical abundance gradients in their wakes. We show that the relative [Fe/O] abundance gradients in ring galaxies can be used as a tool for determining the role of the SN Ia explosions in their chemical enrichment. We consider two mechanisms--a self-induced wave and a density wave--that can create outwardly propagating star-forming rings in a purely gaseous disk and demonstrate that the radial distribution of the relative [Fe/O] abundance gradients depends neither on the particular mechanism of the wave formation anor on the parameters of the star-forming process. We show that the [Fe/O] profile is determined by the velocity of the wave, the initial mass function, and the initial chemical composition of the star-forming gas. If the role of SN Ia explosions is negligible in the chemical enrichment, the ratio [Fe/O] remains constant throughout the galactic disk with a steep gradient at the wave front. If SN Ia stars are important in the production of cosmic iron, the [Fe/O] ratio has a gradient in the wake of the star-forming wave with the value depending on the frequency of SN Ia explosions.

  7. Tracking the effects of crusher gradients on gradient-echo BOLD signal in space and time during rat sensory stimulation

    OpenAIRE

    Goelman, Gadi; Pelled, Galit; Dodd, Steve; Koretsky, Alan

    2008-01-01

    A unique method to map the effect of crusher gradients in space and time on the gradient echo BOLD signal is introduced. Using the Radial Correlation Contrast (RCC) analysis method, amplitude-RCC maps at different time segments and different gradient strengths were obtained. The ratio of amplitude-RCC cluster volumes, with and without crusher gradients, showed a temporal dependency with stronger volume reduction for stimulation-onset versus stimulation-decline. Aside from SNR reduction in dif...

  8. Three-Dimensional Gradients of Cytokine Signaling between T Cells.

    Directory of Open Access Journals (Sweden)

    Kevin Thurley

    2015-04-01

    Full Text Available Immune responses are regulated by diffusible mediators, the cytokines, which act at sub-nanomolar concentrations. The spatial range of cytokine communication is a crucial, yet poorly understood, functional property. Both containment of cytokine action in narrow junctions between immune cells (immunological synapses and global signaling throughout entire lymph nodes have been proposed, but the conditions under which they might occur are not clear. Here we analyze spatially three-dimensional reaction-diffusion models for the dynamics of cytokine signaling at two successive scales: in immunological synapses and in dense multicellular environments. For realistic parameter values, we observe local spatial gradients, with the cytokine concentration around secreting cells decaying sharply across only a few cell diameters. Focusing on the well-characterized T-cell cytokine interleukin-2, we show how cytokine secretion and competitive uptake determine this signaling range. Uptake is shaped locally by the geometry of the immunological synapse. However, even for narrow synapses, which favor intrasynaptic cytokine consumption, escape fluxes into the extrasynaptic space are expected to be substantial (≥20% of secretion. Hence paracrine signaling will generally extend beyond the synapse but can be limited to cellular microenvironments through uptake by target cells or strong competitors, such as regulatory T cells. By contrast, long-range cytokine signaling requires a high density of cytokine producers or weak consumption (e.g., by sparsely distributed target cells. Thus in a physiological setting, cytokine gradients between cells, and not bulk-phase concentrations, are crucial for cell-to-cell communication, emphasizing the need for spatially resolved data on cytokine signaling.

  9. Chemical gradients and progressive veining in a partly serpentinized harzburgite

    Science.gov (United States)

    Schwarzenbach, Esther; Caddick, Mark; Beard, James; Bodnar, Robert

    2016-04-01

    Serpentinized ultramafic rocks constitute a major part of the oceanic lithosphere. They form when water interacts with olivine and pyroxene to produce a dense network of veins comprised of secondary minerals: Serpentine + brucite ± magnetite veins occur in olivine, Al-rich serpentine + talc veins occur in orthopyroxene, and Al-rich serpentine ± talc ± brucite veins occur at the boundary between orthopyroxene and olivine. Here, we present a detailed study on a harzburgite from the Santa Elena Ophiolite in Costa Rica that is ~30% serpentinized in order to provide new constraints on the effect of variable water (H2O) and silica (SiO2) activities on vein formation in peridotites. The studied sample records 1) mineralogical and chemical zonations in olivine-hosted veins that show a distinct pattern with increasing width of the veins (consumption of olivine), 2) varying brucite composition depending on whether or not it is associated with magnetite, and 3) chemical gradients in Si, Al, Cr, and Ca at the boundary between orthopyroxene- and olivine-hosted veins. These observed chemical variations suggest fluid mediated mass transport within and between orthopyroxene- and olivine-hosted veins. We use thermodynamic models to show that an increase in vein width and progressive evolution of olivine-hosted veins is accompanied by an increase in water-rock ratios. This is associated with the development of chemical gradients (e.g. gradients in water and silica activity) between the fluid-rich center of serpentine veins and the olivine grain boundaries as typically expressed by the abundance of brucite in the vein center and a dominance of serpentine at the boundary with olivine. The increase in water-rock ratios within the vein center also leads to the formation of magnetite from Fe-rich brucite ± Fe-rich serpentine. Mass transfer between vein core and vein rim may exist on the submicron-scale along grain boundaries of the finely intergrown serpentine-brucite mixture. We

  10. Interpretation of magnetic anomalies using the horizontal gradient analytic signal

    Directory of Open Access Journals (Sweden)

    H. A. Bake

    2001-06-01

    Full Text Available In recent years the analytic signal method has been of great utility in the interpretation of potential field data. The amplitude of the 3D analytic signal of magnetic data yields information on the location of the edges of the sources in both the horizontal and vertical dimensions, with the main advantage that the magnetic field and magnetic source parameters need not be known or assumed. Accurate detection of source body coordinates is becoming the main goal for interpreters and therefore enhanced techniques are acquiring an increasing revival in data interpretation. This paper presents a high-resolution approach for detecting source boundaries. These boundaries can be determined from the maxima of the analytic signal computed from the horizontal gradient of the field, defined here as a vector, the components of which are the analytic signals of x- and y-horizontal derivatives, respectively. Synthetic examples have shown the high resolving power of the proposed technique. This approach has also given very good results when applied to real data.

  11. Signal Processing in Periodically Forced Gradient Frequency Neural Networks

    Science.gov (United States)

    Kim, Ji Chul; Large, Edward W.

    2015-01-01

    Oscillatory instability at the Hopf bifurcation is a dynamical phenomenon that has been suggested to characterize active non-linear processes observed in the auditory system. Networks of oscillators poised near Hopf bifurcation points and tuned to tonotopically distributed frequencies have been used as models of auditory processing at various levels, but systematic investigation of the dynamical properties of such oscillatory networks is still lacking. Here we provide a dynamical systems analysis of a canonical model for gradient frequency neural networks driven by a periodic signal. We use linear stability analysis to identify various driven behaviors of canonical oscillators for all possible ranges of model and forcing parameters. The analysis shows that canonical oscillators exhibit qualitatively different sets of driven states and transitions for different regimes of model parameters. We classify the parameter regimes into four main categories based on their distinct signal processing capabilities. This analysis will lead to deeper understanding of the diverse behaviors of neural systems under periodic forcing and can inform the design of oscillatory network models of auditory signal processing. PMID:26733858

  12. On detonation initiation by a temperature gradient for a detailed chemical reaction models

    International Nuclear Information System (INIS)

    The evolution from a temperature gradient to a detonation is investigated for combustion mixture whose chemistry is governed by a detailed chemical kinetics. We show that a detailed chemical reaction model has a profound effect on the spontaneous wave concept for detonation initiation by a gradient of reactivity. The evolution to detonation due to a temperature gradient is considered for hydrogen-oxygen and hydrogen-air mixtures at different initial pressures. It is shown that the minimal length of the temperature gradient for which a detonation can be ignited is much larger than that predicted from a one-step chemical model. - Highlights: → We study detonation initiation by temperature gradient for detailed chemical models. → Detailed chemical models have a profound effect on the spontaneous wave concept. → Initiating detonation by temperature gradient differs from one-step model. → In real fuels DDT can not be initiated by temperature gradient.

  13. Research and Simulation of FECG Signal Blind Separation Algorithm Based on Gradient Method

    Directory of Open Access Journals (Sweden)

    Yu Chen

    2012-08-01

    Full Text Available Independent Component Analysis (ICA is a new developed signal separation and digital analysis technology in recent years. ICA has widely used because it does not need to know the signal prior information, which has became the hot spot in signal processing field research. In this study, we firstly introduce the principle, meaning and blind source separation algorithm based on the gradient. By using the traditional natural gradient algorithm and Equi-variant Adaptive Source Separation via Independent (EASI blind separation algorithm, mixing ECG signals with noises had been separated effectively into the Maternal Electrocardiograph (MECG signal, Fetal Electrocardiograph (FECG signal and noise signal. The algorithm separation test showed that EASI algorithm can better separate the fetal ECG signal and because the gradient algorithm is a kind of online algorithm, which can be used for clinical fetal ECG signal of the real-time detection with important practical value and research significance.

  14. Chemical and mechanical signaling in epithelial spreading

    International Nuclear Information System (INIS)

    We propose a minimal mathematical model to explain long-range coordination of dynamics of multiple cells in epithelial spreading, which may be induced, under different conditions, by a chemical signal, or mechanically induced strain, or both. The model is based on chemo-mechanical interactions including a chemical effect of strain, chemically induced polarization and active traction, and interaction between polarized cells. The results, showing kinase concentration distribution and cell displacement, velocity, and stress fields, allow us to reproduce qualitatively available experimental data and distinguish between distinct dynamical patterns observed under conditions of injury or unconstraining. (paper)

  15. Systematics in Metallicity Gradient Measurements I : Angular Resolution, Signal-to-Noise and Annuli Binning

    CERN Document Server

    Yuan, T -T; Rich, J

    2013-01-01

    With the rapid progress in metallicity gradient studies at high-redshift, it is imperative that we thoroughly understand the systematics in these measurements. This work investigates how the [NII]/Halpha ratio based metallicity gradients change with angular resolution, signal-to-noise (S/N), and annular binning parameters. Two approaches are used: 1. We downgrade the high angular resolution integral-field data of a gravitationally lensed galaxy and re-derive the metallicity gradients at different angular resolution; 2. We simulate high-redshift integral field spectroscopy (IFS) observations under different angular resolution and S/N conditions using a local galaxy with a known gradient. We find that the measured metallicity gradient changes systematically with angular resolution and annular binning. Seeing-limited observations produce significantly flatter gradients than higher angular resolution observations. There is a critical angular resolution limit beyond which the measured metallicity gradient is subst...

  16. Distinguishing between cystic teratomas and endometriomas of the ovary using chemical shift gradient echo magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Ishijima Hideyuki; Ishizaka Hiroshi; Inoue Tomio [Gunma University Hospital, Gunma (Japan). Depts. of Diagnostic Radiaology and Nuclear Medicine

    1996-02-01

    The purpose of this study was to evaluate the efficacy of chemical shift gradient echo magnetic resonance imaging (MRI) in distinguishing between cystic teratomas and endometriomas of the ovary, using a 1.5 T magnet. The study included 22 patients with 31 ovarian lesions (15 cystic teratomas and 16 endometriomas), which showed high signal intensity on T1-weighted spin echo images. Chemical shift gradient echo images with three different echo times (TE = 2.5, 4.5 and 6.5 ms) were obtained in all cases. Indices were calculated on the basis of the signal intensities of lesions on the chemical shift gradient echo images. All endometriomas had signal intensity indices of less than 2.1, while all cystic teratomas had signal intensity indices of 18.1 or greater. It was concluded that the method used in this study presents the following advantages: the acquisition time is short; it needs no special software; and it does not depend on magnetic field homogeneity. 11 refs., 4 figs.

  17. Interpretation of magnetic anomalies using the horizontal gradient analytic signal

    OpenAIRE

    H. A. Bake; N. Bournas

    2001-01-01

    In recent years the analytic signal method has been of great utility in the interpretation of potential field data. The amplitude of the 3D analytic signal of magnetic data yields information on the location of the edges of the sources in both the horizontal and vertical dimensions, with the main advantage that the magnetic field and magnetic source parameters need not be known or assumed. Accurate detection of source body coordinates is becoming the main goal for interpreters and therefore e...

  18. Mechanical and Chemical Signaling in Angiogenesis

    CERN Document Server

    2013-01-01

    This volume of Studies in Mechanobiology, Tissue Engineering and Biomaterials describes the most recent advances in angiogenesis research at all biological length scales: molecular, cellular and tissue, in both in vivo and in vitro settings.  Angiogenesis experts from diverse fields including engineering, cell and developmental biology, and chemistry have contributed chapters which focus on the mechanical and chemical signals which affect and promote blood vessel growth. Specific emphasis is given to novel methodologies and biomaterials that have been developed and applied to angiogenesis research. 

  19. Gradient sensing by a bistable regulatory motif enhances signal amplification but decreases accuracy in individual cells

    Science.gov (United States)

    Sharma, Rati; Roberts, Elijah

    2016-06-01

    Many vital eukaryotic cellular functions require the cell to respond to a directional gradient of a signaling molecule. The first two steps in any eukaryotic chemotactic/chemotropic pathway are gradient detection and cell polarization. Like many processes, such chemotactic and chemotropic decisions are made using a relatively small number of molecules and are thus susceptible to internal and external fluctuations during signal transduction. Large cell-to-cell variations in the magnitude and direction of a response are therefore possible and do, in fact, occur in natural systems. In this work we use three-dimensional probabilistic modeling of a simple gradient sensing pathway to study the capacity for individual cells to accurately determine the direction of a gradient, despite fluctuations. We include a stochastic external gradient in our simulations using a novel gradient boundary condition modeling a point emitter a short distance away. We compare and contrast three different variants of the pathway, one monostable and two bistable. The simulation data show that an architecture combining bistability with spatial positive feedback permits the cell to both accurately detect and internally amplify an external gradient. We observe strong polarization in all individual cells, but in a distribution of directions centered on the gradient. Polarization accuracy in our study was strongly dependent upon a spatial positive feedback term that allows the pathway to trade accuracy for polarization strength. Finally, we show that additional feedback links providing information about the gradient to multiple levels in the pathway can help the cell to refine initial inaccuracy in the polarization direction.

  20. Magnetic resonance imaging with nonlinear gradient fields signal encoding and image reconstruction

    CERN Document Server

    Schultz, Gerrit

    2013-01-01

    Within the past few decades magnetic resonance imaging has become one of the most important imaging modalities in medicine. For a reliable diagnosis of pathologies further technological improvements are of primary importance. This text deals with a radically new approach of image encoding: The fundamental principle of gradient linearity is challenged by investigating the possibilities of acquiring anatomical images with the help of nonlinear gradient fields. Besides a thorough theoretical analysis with a focus on signal encoding and image reconstruction, initial hardware implementations are tested using phantom as well as in-vivo measurements. Several applications are presented that give an impression about the implications that this technological advancement may have for future medical diagnostics.   Contents n  Image Reconstruction in MRI n  Nonlinear Gradient Encoding: PatLoc Imaging n  Presentation of Initial Hardware Designs n  Basics of Signal Encoding and Image Reconstruction in PatLoc Imaging n ...

  1. Communication: Control of chemical reactions using electric field gradients.

    Science.gov (United States)

    Deshmukh, Shivaraj D; Tsori, Yoav

    2016-05-21

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts. PMID:27208928

  2. Communication: Control of chemical reactions using electric field gradients

    Science.gov (United States)

    Deshmukh, Shivaraj D.; Tsori, Yoav

    2016-05-01

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts.

  3. Inter-kingdom signaling: chemical language between bacteria and host

    OpenAIRE

    Pacheco, Alline R.; Sperandio, Vanessa

    2009-01-01

    Chemical communication between cells ensures coordination of behavior. In prokaryotes, this chemical communication is usually referred to as quorum sensing, while eukaryotic cells signal through hormones. In the past years, a growing number of reports have shown that bacterial quorum sensing signals, called autoinducers, signal to eukaryotic cells, mimicking hormones. Conversely, host hormones can signal to bacterial cells through converging pathways to autoinducer signaling. This inter-kingd...

  4. Biofilm responses to smooth flow fields and chemical gradients in novel microfluidic flow cells

    OpenAIRE

    Song, Jisun L.; Au, Kelly H.; Huynh, Kimberly T.; Packman, Aaron I.

    2013-01-01

    We present two novel microfluidic flow cells developed to provide reliable control of flow distributions and chemical gradients in biofilm studies. We developed a single-inlet microfluidic flow cell to support biofilm growth under a uniform velocity field, and a double-inlet flow cell to provide a very smooth transverse concentration gradient. Both flow cells consist of a layer of polydimethylsiloxane (PDMS) bonded to glass cover slips and were fabricated using the replica molding technique. ...

  5. A paradoxical signal intensity increase in fatty livers using opposed-phase gradient echo imaging with fat-suppression pulses

    International Nuclear Information System (INIS)

    With the increase in obese and overweight children, nonalcoholic fatty liver disease has become more prevalent in the pediatric population. Appreciating subtleties of magnetic resonance (MR) signal intensity behavior from fatty livers under different imaging conditions thus becomes important to pediatric radiologists. We report an initially confusing signal behavior - increased signal from fatty livers when fat-suppression pulses are applied in an opposed-phase gradient echo imaging sequence - and seek to explain the physical mechanisms for this paradoxical signal intensity behavior. Abdominal MR imaging at 3 T with a 3-D volumetric interpolated breath-hold (VIBE) sequence in the opposed-phase condition (TR/TE 3.3/1.3 ms) was performed in five obese boys (14±2 years of age, body mass index >95th percentile for age and sex) with spectroscopically confirmed fatty livers. Two VIBE acquisitions were performed, one with and one without the use of chemical shift selective (CHESS) pulse fat suppression. The ratios of fat-suppressed over non-fat-suppressed signal intensities were assessed in regions-of-interest (ROIs) in five tissues: subcutaneous fat, liver, vertebral marrow, muscle and spleen. The boys had spectroscopically estimated hepatic fat levels between 17% and 48%. CHESS pulse fat suppression decreased subcutaneous fat signals dramatically, by more than 85% within regions of optimal fat suppression. Fatty liver signals, in contrast, were elevated by an average of 87% with CHESS pulse fat suppression. Vertebral marrow signal was also significantly elevated with CHESS pulse fat suppression, while spleen and muscle signals demonstrated only small signal increases on the order of 10%. We demonstrated that CHESS pulse fat suppression actually increases the signal intensity from fatty livers in opposed-phase gradient echo imaging conditions. The increase can be attributed to suppression of one partner of the opposed-phase pair that normally contributes to the

  6. Cell cycle arrest by a gradient of Dpp signaling during Drosophila eye development

    Directory of Open Access Journals (Sweden)

    Bhattacharya Abhishek

    2010-03-01

    Full Text Available Abstract Background The secreted morphogen Dpp plays important roles in spatial regulation of gene expression and cell cycle progression in the developing Drosophila eye. Dpp signaling is required for timely cell cycle arrest ahead of the morphogenetic furrow as a prelude to differentiation, and is also important for eye disc growth. The dpp gene is expressed at multiple locations in the eye imaginal disc, including the morphogenetic furrow that sweeps across the eye disc as differentiation initiates. Results Studies of Brinker and Dad expression, and of Mad phosphorylation, establish that there is a gradient of Dpp signaling in the eye imaginal disc anterior to the morphogenetic furrow, predominantly in the anterior-posterior axis, and also Dpp signaling at the margins of the disc epithelium and in the dorsal peripodial membrane. Almost all signaling activity seems to spread through the plane of the epithelia, although peripodial epithelium cells can also respond to underlying disc cells. There is a graded requirement for Dpp signaling components for G1 arrest in the eye disc, with more stringent requirements further anteriorly where signaling is lower. The signaling level defines the cell cycle response, because elevated signaling through expression of an activated Thickveins receptor molecule arrested cells at more anterior locations. Very anterior regions of the eye disc were not arrested in response to activated receptor, however, and evidence is presented that expression of the Homothorax protein may contribute to this protection. By contrast to activated Thickveins, ectopic expression of processed Dpp leads to very high levels of Mad phosphorylation which appear to have non-physiological consequences. Conclusions G1 arrest occurs at a threshold level of Dpp signaling within a morphogen gradient in the anterior eye. G1 arrest is specific for one competent domain in the eye disc, allowing Dpp signaling to promote growth at earlier

  7. Research on n-γ discrimination method based on spectrum gradient analysis of signals

    International Nuclear Information System (INIS)

    Having discovered that there are distinct differences between the spectrum gradient of the output neutron and γ-ray signal from liquid scintillator detectors, this paper presented a n-γ discrimination method called spectrum gradient analysis (SGA) based on frequency-domain features of the pulse signals. The basic principle and feasibility of SGA method were discussed and the validity of n-γ discrimination results of SGA was verified by the associated particle neutron flight experiment. The discrimination performance of SGA was evaluated under different conditions of sampling rates ranging from 5 G/s to 250 M/s. The results show that SGA method exhibits insensitivity to noise, strong anti-interference ability, stable discrimination performance and lower amount of calculation in contrast with time-domain n-γ discrimination methods. (authors)

  8. Chemically active colloids near osmotic-responsive walls with surface-chemistry gradients

    CERN Document Server

    Popescu, M N; Dietrich, S

    2016-01-01

    Chemically active colloids move by creating gradients in the composition of the surrounding solution and by exploiting the differences in their interactions with the various molecular species in solution. If such particles move near boundaries, e.g., the walls of the container confining the suspension, gradients in the composition of the solution are also created along the wall. This give rise to chemi-osmosis (via the interactions of the wall with the molecular species forming the solution), which drives flows coupling back to the colloid and thus influences its motility. Employing an approximate "point-particle" analysis, we show analytically that -- owing to this kind of induced active response (chemi-osmosis) of the wall -- such chemically active colloids can align with, and follow, gradients in the surface chemistry of the wall. In this sense, these artificial "swimmers" exhibit a primitive form of thigmotaxis with the meaning of sensing the proximity of a (not necessarily discontinuous) physical change ...

  9. New insights into the mechanisms of signal formation in RF-spoiled gradient echo sequences.

    OpenAIRE

    Azizieh, Céline; Denolin, Vincent; Metens, Thierry

    2005-01-01

    RF spoiling is a well established method to produce T1-weighted images with short repetition time gradient-echo sequences, by eliminating coherent transverse magnetization with appropriate RF phase modulation. This paper presents two novel approaches to describe signal formation in such sequences. Both methods rely on the formulation of RF spoiling as a linear increase of the precession angle between RF pulses, which is an alternative to the commonly used quadratic pulse phase scheme. The fir...

  10. Chemical gradients in the Milky Way from the RAVE data. I. Dwarf stars

    CERN Document Server

    Boeche, C; Piffl, T; Just, A; Steinmetz, M; Sharma, S; Kordopatis, G; Gilmore, G; Chiappini, C; Williams, M; Grebel, E K; Bland-Hawthorn, J; Gibson, B K; Munari, U; Siviero, A; Bienaymé, O; Navarro, J F; Parker, Q A; Reid, W; Seabroke, G M; Watson, F G; Wyse, R F G; Zwitter, T

    2013-01-01

    Aim: We aim at measuring the chemical gradients of the elements Mg, Al, Si, and Fe along the Galactic radius to provide new constraints on the chemical evolution models of the Galaxy and Galaxy models such as the Besancon model. Methods: We analysed three different samples selected from three independent datasets: a sample of 19,962 dwarf stars selected from the RAVE database, a sample of 10,616 dwarf stars selected from the Geneva-Copenhagen Survey (GCS) dataset, and a mock sample (equivalent to the RAVE sample) created by using the GALAXIA code, which is based on the Besancon model. We measured the chemical gradients as functions of the guiding radius (Rg) at different distances from the Galactic plane reached by the stars along their orbit (Zmax). Results: The chemical gradients of the RAVE and GCS samples are negative and show consistent trends, although they are not equal: at Zmax<0.4 kpc and 4.5gradient for the RAVE sample is d[Fe/H]/dRg=-0.065 dex kpc^{-1}, whereas for t...

  11. Moment-flux models for bacterial chemotaxis in large signal gradients.

    Science.gov (United States)

    Xue, Chuan; Yang, Xige

    2016-10-01

    Chemotaxis is a fundamental process in the life of many prokaryotic and eukaryotic cells. Chemotaxis of bacterial populations has been modeled by both individual-based stochastic models that take into account the biochemistry of intracellular signaling, and continuum PDE models that track the evolution of the cell density in space and time. Continuum models have been derived from individual-based models that describe intracellular signaling by a system of ODEs. The derivations rely on quasi-steady state approximations of the internal ODE system. While this assumption is valid if cell movement is subject to slowly changing signals, it is often violated if cells are exposed to rapidly changing signals. In the latter case current continuum models break down and do not match the underlying individual-based model quantitatively. In this paper, we derive new PDE models for bacterial chemotaxis in large signal gradients that involve not only the cell density and flux, but also moments of the intracellular signals as a measure of the deviation of cell's internal state from its steady state. The derivation is based on a new moment closure method without calling the quasi-steady state assumption of intracellular signaling. Numerical simulations suggest that the resulting model matches the population dynamics quantitatively for a much larger range of signals. PMID:26922437

  12. Molecular Dynamics Study of Thermally Augmented Nanodroplet Motion on Chemical Energy Induced Wettability Gradient Surfaces.

    Science.gov (United States)

    Chakraborty, Monojit; Chowdhury, Anamika; Bhusan, Richa; DasGupta, Sunando

    2015-10-20

    Droplet motion on a surface with chemical energy induced wettability gradient has been simulated using molecular dynamics (MD) simulation to highlight the underlying physics of molecular movement near the solid-liquid interface including the contact line friction. The simulations mimic experiments in a comprehensive manner wherein microsized droplets are propelled by the surface wettability gradient against forces opposed to motion. The liquid-wall Lennard-Jones interaction parameter and the substrate temperature are varied to explore their effects on the three-phase contact line friction coefficient. The contact line friction is observed to be a strong function of temperature at atomistic scales, confirming their experimentally observed inverse functionality. Additionally, the MD simulation results are successfully compared with those from an analytical model for self-propelled droplet motion on gradient surfaces. PMID:26381847

  13. Effects of reversible chemical reaction on Li diffusion and stresses in spherical composition-gradient electrodes

    International Nuclear Information System (INIS)

    Composition-gradient electrode materials have been proven to be one of the most promising materials in lithium-ion battery. To study the mechanism of mechanical degradation in spherical composition-gradient electrodes, the finite deformation theory and reversible chemical theory are adopted. In homogeneous electrodes, reversible electrochemical reaction may increase the magnitudes of stresses. However, reversible electrochemical reaction has different influences on stresses in composition-gradient electrodes, resulting from three main inhomogeneous factors—forward reaction rate, backward reaction rate, and reaction partial molar volume. The decreasing transition form of forward reaction rate, increasing transition form of backward reaction rate, and increasing transition form of reaction partial molar volume can reduce the magnitudes of stresses. As a result, capacity fading and mechanical degradation are reduced by taking advantage of the effects of inhomogeneous factors

  14. Energy dissipation drives the gradient signal amplification through an incoherent type-1 feed-forward loop

    Science.gov (United States)

    Lan, Ganhui

    2015-09-01

    We present here the analytical relation between the gain of eukaryotic gradient sensing network and the associated thermodynamic cost. By analyzing a general incoherent type-1 feed-forward loop, we derive the gain function (G ) through the reaction network and explicitly show that G depends on the nonequilibrium factor (0 ≤γ ≤1 with γ =0 and 1 representing irreversible and equilibrium reaction systems, respectively), the Michaelis constant (KM), and the turnover ratio (rcat) of the participating enzymes. We further find the maximum possible gain is intrinsically determined by KM/Gmax=(1 /KM+2 ) /4 . Our model also indicates that the dissipated energy (measured by -lnγ ), from the intracellular energy-bearing bioparticles (e.g., ATP), is used to generate a force field Fγ∝(1 -√{γ }) that reshapes and disables the effective potential around the zero gain region, which leads to the ultrasensitive response to external chemical gradients.

  15. Chemical abundance gradients from open clusters in the Milky Way disk: results from the APOGEE survey

    CERN Document Server

    Cunha, Katia; Souto, Diogo; Thompson, Benjamin; Zasowski, Gail; Prieto, Carlos Allende; Carrera, Ricardo; Chiappini, Cristina; Donor, John; Garcia-Hernandez, Anibal; Perez, Ana Elia Garcia; Hayden, Michael R; Holtzman, Jon; Jackson, Kelly M; Johnson, Jennifer A; Majewski, Steven R; Meszaros, Szabolcs; Meyer, Brianne; Nidever, David L; O'Connell, Julia; Schiavon, Ricardo P; Schultheis, Mathias; Shetrone, Matthew; Simmons, Audrey; Smith, Verne V; Zamora, Olga

    2016-01-01

    Metallicity gradients provide strong constraints for understanding the chemical evolution of the Galaxy. We report on radial abundance gradients of Fe, Ni, Ca, Si, and Mg obtained from a sample of 304 red-giant members of 29 disk open clusters, mostly concentrated at galactocentric distances between ~8 - 15 kpc, but including two open clusters in the outer disk. The observations are from the APOGEE survey. The chemical abundances were derived automatically by the ASPCAP pipeline and these are part of the SDSS III Data Release 12. The gradients, obtained from least squares fits to the data, are relatively flat, with slopes ranging from -0.026 to -0.033 dex/kpc for the alpha-elements [O/H], [Ca/H], [Si/H] and [Mg/H] and -0.035 dex/kpc and -0.040 dex/kpc for [Fe/H] and [Ni/H], respectively. Our results are not at odds with the possibility that metallicity ([Fe/H]) gradients are steeper in the inner disk (R_GC ~7 - 12 kpc) and flatter towards the outer disk. The open cluster sample studied spans a significant ran...

  16. Chemical gradients in the Milky Way from the RAVE data. II. Giant stars

    CERN Document Server

    Boeche, C; Piffl, T; Just, A; Steinmetz, M; Grebel, E K; Sharma, S; Kordopatis, G; Gilmore, G; Chiappini, C; Freeman, K; Gibson, B K; Munari, U; Siviero, A; Bienaymé, O; Navarro, J F; Parker, Q A; Reid, W; Seabroke, G M; Watson, F G; Wyse, R F G; Zwitter, T

    2014-01-01

    We provide new constraints on the chemo-dynamical models of the Milky Way by measuring the radial and vertical chemical gradients for the elements Mg, Al, Si, Ti, and Fe in the Galactic disc and the gradient variations as a function of the distance from the Galactic plane ($Z$). We selected a sample of giant stars from the RAVE database using the gravity criterium 1.7$<$log g$<$2.8. We created a RAVE mock sample with the Galaxia code based on the Besan\\c con model and selected a corresponding mock sample to compare the model with the observed data. We measured the radial gradients and the vertical gradients as a function of the distance from the Galactic plane $Z$ to study their variation across the Galactic disc. The RAVE sample exhibits a negative radial gradient of $d[Fe/H]/dR=-0.054$ dex kpc$^{-1}$ close to the Galactic plane ($|Z|<0.4$ kpc) that becomes flatter for larger $|Z|$. Other elements follow the same trend although with some variations from element to element. The mock sample has radial...

  17. Fabrication and characterization of a microfluidic module for chemical gradient generation utilizing passive pumping.

    Science.gov (United States)

    Kuo, Jonathan T W; Li, Connie; Meng, Ellis

    2014-01-01

    We introduce a micro-biochemical administration module (μBAM) for generating chemical gradients for use in axonal guidance studies. The device is designed to be simple to use, require minimal packaging, and be operated using only a pipette. A passive pumping mechanism is utilized to pump liquid through a SU-8 microchannel and then the micropore on the Parylene cap of the microchannel. The achievable flow rate delivery through the micropore was characterized and manipulated by varying the drop volumes used to passively drive fluid flow into the device. Biochemicals controllably delivered using this module can be combined with neuronal cell cultures to form chemical gradients for axonal guidance studies. PMID:25570971

  18. Bacteria are not too small for spatial sensing of chemical gradients: An experimental evidence

    DEFF Research Database (Denmark)

    Thar, Roland; Kühl, Michael

    2003-01-01

    By analyzing the chemotactic behavior of a recently described marine bacterial species, we provide experimental evidence that bacteria are not too small for sensing chemical gradients spatially. The bipolar flagellated vibrioid bacteria (typical size 2 × 6 µm) exhibit a unique motility pattern as...... oxygen concentration is rotating faster than the other bundle. A mathematical model based on these assumptions reproduces the observed swimming behavior of the bacteria....

  19. Quantitative Analysis of Diffusion Weighted MR Images of Brain Tumor Using Signal Intensity Gradient Technique

    Directory of Open Access Journals (Sweden)

    S. S. Shanbhag

    2014-01-01

    Full Text Available The purpose of this study was to evaluate the role of diffusion weighted-magnetic resonance imaging (DW-MRI in the examination and classification of brain tumors, namely, glioma and meningioma. Our hypothesis was that as signal intensity variations on diffusion weighted (DW images depend on histology and cellularity of the tumor, analysing the signal intensity characteristics on DW images may allow differentiating between the tumor types. Towards this end the signal intensity variations on DW images of the entire tumor volume data of 20 subjects with glioma and 12 subjects with meningioma were investigated and quantified using signal intensity gradient (SIG parameter. The relative increase in the SIG values (RSIG for the subjects with glioma and meningioma was in the range of 10.08–28.36 times and 5.60–9.86 times, respectively, compared to their corresponding SIG values on the contralateral hemisphere. The RSIG values were significantly different between the subjects with glioma and meningioma (P<0.01, with no overlap between RSIG values across the two tumors. The results indicate that the quantitative changes in the RSIG values could be applied in the differential diagnosis of glioma and meningioma, and their adoption in clinical diagnosis and treatment could be helpful and informative.

  20. Cytoplasmic fat detection utilizing chemical shift gradient. Echo MR imaging in cases of clear cell renal cell carcinoma

    International Nuclear Information System (INIS)

    We investigated whether cytoplasmic fat in clear cell renal cell carcinoma (CCC) can be identified by chemical shift gradient-echo magnetic resonance imaging (CSI). CSI was performed for 22 cases of CCC and 30 cases of other renal tumors (including 16 cases of non-CCC), all of which were surgically proven. Signal reduction in out-of-phase images of these tumors was retrospectively evaluated and compared. The signal loss ratio (SLR) was defined and calculated. Fat staining of specimens from 16 tumors was performed and correlated with SLR. SLR was found to be significantly higher in CCC than in non-CCC (p<0.002). There was a significant correlation between the degree of fat staining positively of the specimens and SLR (p<0.01). When signal reduction in out-of-phase images suggested a diagnosis of CCC, a correct diagnosis of this entity was made in the resected renal tumors with a sensitivity, specificity, and accuracy of 82%, 93%, and 88%, respectively. CSI can demonstrate cytoplasmic fat in CCC, which helps to differentiate this entity from other renal tumors. (author)

  1. Exact algebraization of the signal equation of spoiled gradient echo MRI

    Energy Technology Data Exchange (ETDEWEB)

    Dathe, Henning [Department of Orthodontics, Biomechanics Group, University Medical Centre, Goettingen (Germany); Helms, Gunther, E-mail: ghelms@gwdg.d [MR-Research in Neurology and Psychiatry, University Medical Centre, Goettingen (Germany)

    2010-08-07

    The Ernst equation for Fourier transform nuclear magnetic resonance (MR) describes the spoiled steady-state signal created by periodic partial excitation. In MR imaging (MRI), it is commonly applied to spoiled gradient-echo acquisition in the steady state, created by a small flip angle {alpha} at a repetition time TR much shorter than the longitudinal relaxation time T{sub 1}. We describe two parameter transformations of {alpha} and TR/T{sub 1}, which render the Ernst equation as a low-order rational function. Computer algebra can be readily applied for analytically solving protocol optimization, as shown for the dual flip angle experiment. These transformations are based on the half-angle tangent substitution and its hyperbolic analogue. They are monotonic and approach identity for small {alpha} and small TR/T{sub 1} with a third-order error. Thus, the exact algebraization can be readily applied to fast gradient echo MRI to yield a rational approximation in {alpha} and TR/T{sub 1}. This reveals a fundamental relationship between the square of the flip angle and TR/T{sub 1} which characterizes the Ernst angle, constant degree of T{sub 1}-weighting and the influence of the local radio-frequency field.

  2. Fabrication of Isotropic Pyrocarbon at 1400℃ by Thermal Gradient Chemical Vapor Deposition Apparatus

    Institute of Scientific and Technical Information of China (English)

    GUO Lingjun; ZHANG Dongsheng; LI Kezhi; LI Hejun

    2009-01-01

    An experiment was designed to prepare isotropic pyrocarbon by thermal gradient chemical vapor deposition apparatus.The deposition was performed under ambient atmosphere at 1400℃,with natural gas volume flow of 3.5 m~3/h for 80 h.The results show that the thickness and the bulk density of the deposit are about 1.95 g/cm~3 and 10 mm,respectively.The microstructure of the deposit was examined by polarized light microscopy and scanning electron microscopy,which shows that the deposit is constituted of sphere isotropic pyrocarbon,pebble pyrocarbon and laminar pyrocarbon.

  3. The metallicity gradient of M 33: chemical abundances of HII regions

    OpenAIRE

    Magrini, L.; Vilchez, J. M.; A. Mampaso; Corradi, R. L. M.; Leisy, P.

    2007-01-01

    We present spectroscopic observations of a sample of 72 emission-line objects, including mainly HII regions, in the spiral galaxy M 33. Spectra were obtained with the multi-object, wide field spectrograph AF2/WYFFOS at the 4.2m WHT telescope. Line intensities, extinction, and electron density were determined for the whole sample of objects. The aim of the present work was to derive chemical and physical parameters of a set of HII regions, and from them the metallicity gradient. Electron tempe...

  4. Biomimetic catalysts responsive to specific chemical signals

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yan [Iowa State Univ., Ames, IA (United States)

    2015-03-04

    amphiphilic principles used in the foldamer catalysts were extended to a few other systems, particularly to interfacially cross-linked reverse micelles and micelles. These features enabled unusual catalytic features such as basic/nucleophilic catalysis under acidic conditions. We were able to create highly active metal nanoclusters catalysts whose local environment could be tuned by the organic framework. We were even able to create a “catalytic nanomachine” that grabs the substrate to the encapsulated Au clusters, which efficiently convert the substrate to the product that is rapidly ejected due to its different binding properties. Our research has important impacts on fundamental and applied energy-related sciences. On the fundamental level, it tests important biocatalytic principles on relatively simple synthetic systems and is expected to afford deeper understanding of biological catalysis. On the practical level, the research is anticipated to lead to “smart” catalysts and open up exiting applications in chemical analysis, reaction control, and materials synthesis. Part 2. Electrochemical Reduction of CO₂ The primary objective of our research involving the electrochemical reduction of carbon dioxide is to apply a multidisciplinary approach toward developing a greater understanding of the problem of efficiently converting CO₂ to hydrocarbons through electrochemical routes. Our goal is to provide a better understanding of the principles that underlie the electrocatalytic reduction of CO₂ at electrode surfaces and the molecular pathways that lead to desired compounds. This understanding is essential for the design and development of new catalytic materials for the selective production of renewable feedstocks. The electrochemical reduction of CO₂ involves the formation of various reaction products and adsorbed intermediates whose distribution depends upon the nature of the electrode material and the electrochemical conditions, including applied potential

  5. Cellular-signaling pathways unveil the carcinogenic potential of chemicals.

    Science.gov (United States)

    Hendriks, Giel; van de Water, Bob; Schoonen, Willem; Vrieling, Harry

    2013-06-01

    Most of the current in vitro carcinogenicity assays assess the potential carcinogenic properties of chemicals through the detection of inflicted DNA damage or subsequent chromosome damage and gene mutations. Unfortunately, these assays generally do not provide mechanistic insight into the reactive properties of a chemical. Upon chemical-induced damage of biomolecules, molecular sensors will activate general and damage-specific cellular response pathways that provide protection against the (geno)toxic and potential carcinogenic properties of chemicals. These cellular defense mechanisms include activation of cell-cycle checkpoints, DNA repair systems and induction of apoptosis or necrosis. Visualization of activated cellular-signaling pathways forms a powerful means to readily detect the genotoxic potential of chemical compounds and simultaneously gain insight into their reactive properties. Over the past years, various in vitro reporter assays have been developed that monitor activation of general and more specific cellular-signaling pathways, including the GreenScreen HC and ToxTracker assays. In this review we provide a perspective on how we can exploit activation of cellular signaling pathways to shed light on the mode of action of the chemical exposure and to develop sophisticated mechanism-based in vitro assays for cancer risk assessment. PMID:23339022

  6. Influence of NMR measuring sequences and gradient variationon signals from flowing systems. Magnetic resonance tomography on experimental models

    International Nuclear Information System (INIS)

    The influence of flow on MR tomography images and signal intensities has been studied using experimental model tubes and an aqueous NiCl2 solution having the same relaxation time as human blood. We applied the inversion recovery (IR) and the spin-echo (SE) sequence on a .15 T MR tomography system. The influence of RF pulse distance (tau) in the IR and SE experiment as well as the influence of magnetic z-gradient strength on the flow images has been investigated. IR images revealed that signals from flowing systems recover more rapidly due to influx of non-inverted longitudinal magnetization into the scan slice. SE images in presence of flow are characterized by signal intensity loss with increasing time caused by the outflow and dephasing of transverse magnetization. With increasing strength of the z-gradient, the MR signals of flowing fluids decrease drastically. Thus for detection of flow, all the above mentioned parameters are of importance. (orig.)

  7. Chemical composition of vegetation along urbanisation gradients in two European cities

    International Nuclear Information System (INIS)

    Accumulation of particulate matter (PM) and metals on leaves of three deciduous woody species was studied along urbanisation gradients in Stavanger and Warsaw. Differences between rural and urban sites explained most of the observed variation in leaf chemistry, followed by differences between regions. Highest leaf accumulation of elements was found in Warsaw, but also composition of elements differed between the cities. Overall, species showed similar patterns of element accumulation, but differed in accumulation of specific elements. These differences could in part be explained by differences in epicuticular waxes and PM accumulation. Expected source of elements and their chemical characteristics did not explain the observed accumulation patterns. A better differentiation between elements taken up from soil and air would be required for his. Species specific accumulation of elements has to be taken into consideration using leaf samples for biomonitoring. - Highlights: • Rural to urban gradient explained much of the observed variation in leaf chemistry. • PM deposition correlated with metal accumulation in two of three species. • Plant species differed in accumulation of specific elements. - Leaf accumulation of pollutants depends on pollution concentration and is affected by plant species

  8. Probing cellular dynamics with a chemical signal generator.

    Directory of Open Access Journals (Sweden)

    Brandon Kuczenski

    Full Text Available Observations of material and cellular systems in response to time-varying chemical stimuli can aid the analysis of dynamic processes. We describe a microfluidic "chemical signal generator," a technique to apply continuously varying chemical concentration waveforms to arbitrary locations in a microfluidic channel through feedback control of the interface between parallel laminar (co-flowing streams. As the flow rates of the streams are adjusted, the channel walls are exposed to a chemical environment that shifts between the individual streams. This approach can be used to probe the dynamic behavior of objects or substances adherent to the interior of the channel. To demonstrate the technique, we exposed live fibroblast cells to ionomycin, a membrane-permeable calcium ionophore, while assaying cytosolic calcium concentration. Through the manipulation of the laminar flow interface, we exposed the cells' endogenous calcium handling machinery to spatially-contained discrete and oscillatory intracellular disturbances, which were observed to elicit a regulatory response. The spatiotemporal precision of the generated signals opens avenues to previously unapproachable areas for potential investigation of cell signaling and material behavior.

  9. Exclusion of cosmic rays in protoplanetary disks. II. Chemical gradients and observational signatures

    Energy Technology Data Exchange (ETDEWEB)

    Cleeves, L. Ilsedore; Bergin, Edwin A.; Adams, Fred C. [Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109 (United States)

    2014-10-20

    The chemical properties of protoplanetary disks are especially sensitive to their ionization environment. Sources of molecular gas ionization include cosmic rays (CRs), stellar X-rays, and short-lived radionuclides, each of which varies with location in the disk. This behavior leads to a significant amount of chemical structure, especially in molecular ion abundances, which is imprinted in their submillimeter rotational line emission. Using an observationally motivated disk model, we make predictions for the dependence of chemical abundances on the assumed properties of the ionizing field. We calculate the emergent line intensity for abundant molecular ions and simulate sensitive observations with the Atacama Large Millimeter/Sub-millimeter Array (ALMA) for a disk at D = 100 pc. The models readily distinguish between high ionization rates (ζ ≳ 10{sup –17} s{sup –1} per H{sub 2}) and below, but it becomes difficult to distinguish between low ionization models when ζ ≲ 10{sup –19} s{sup –1}. We find that H{sub 2}D{sup +} emission is not detectable for sub-interstellar CR rates with ALMA (6h integration), and that N{sub 2}D{sup +} emission may be a more sensitive tracer of midplane ionization. HCO{sup +} traces X-rays and high CR rates (ζ{sub CR} ≳ 10{sup –17} s{sup –1}), and provides a handle on the warm molecular ionization properties where CO is present in the gas. Furthermore, species like HCO{sup +}, which emits from a wide radial region and samples a large gradient in temperature, can exhibit ring-like emission as a consequence of low-lying rotational level de-excitation near the star. This finding highlights a scenario where rings are not necessarily structural or chemical in nature, but simply a result of the underlying line excitation properties.

  10. Exclusion of cosmic rays in protoplanetary disks. II. Chemical gradients and observational signatures

    International Nuclear Information System (INIS)

    The chemical properties of protoplanetary disks are especially sensitive to their ionization environment. Sources of molecular gas ionization include cosmic rays (CRs), stellar X-rays, and short-lived radionuclides, each of which varies with location in the disk. This behavior leads to a significant amount of chemical structure, especially in molecular ion abundances, which is imprinted in their submillimeter rotational line emission. Using an observationally motivated disk model, we make predictions for the dependence of chemical abundances on the assumed properties of the ionizing field. We calculate the emergent line intensity for abundant molecular ions and simulate sensitive observations with the Atacama Large Millimeter/Sub-millimeter Array (ALMA) for a disk at D = 100 pc. The models readily distinguish between high ionization rates (ζ ≳ 10–17 s–1 per H2) and below, but it becomes difficult to distinguish between low ionization models when ζ ≲ 10–19 s–1. We find that H2D+ emission is not detectable for sub-interstellar CR rates with ALMA (6h integration), and that N2D+ emission may be a more sensitive tracer of midplane ionization. HCO+ traces X-rays and high CR rates (ζCR ≳ 10–17 s–1), and provides a handle on the warm molecular ionization properties where CO is present in the gas. Furthermore, species like HCO+, which emits from a wide radial region and samples a large gradient in temperature, can exhibit ring-like emission as a consequence of low-lying rotational level de-excitation near the star. This finding highlights a scenario where rings are not necessarily structural or chemical in nature, but simply a result of the underlying line excitation properties.

  11. Categorization of biologically relevant chemical signals in the medial amygdala

    OpenAIRE

    Samuelsen, Chad L.; Meredith, Michael

    2009-01-01

    Many species employ chemical signals to convey messages between members of the same species (conspecific), but chemosignals may also provide information to another species (heterospecific). Here, we found that conspecific chemosignals (male, female mouse urine) increased immediate early gene-protein (IEG) expression in both anterior and posterior medial amygdala of male mice, whereas most heterospecific chemosignals (e.g.: hamster vaginal fluid, steer urine) increased expression only in anter...

  12. Physico-chemical gradients within the hydrothermal chimney Roane define sharp boundaries for microbial community ecology

    Science.gov (United States)

    Frank, K. L.; Kelley, D. S.; Girguis, P. R.

    2011-12-01

    The unique physico-chemical gradients characteristic of hydrothermal vents provide diverse niches for prokaryotic communities. To date, our knowledge of environmental constraints on microbial colonization and metabolic activity within active sulfide structures has been limited by the lack of co-registered in situ chemistry and appropriate, taxonomic and metabolic genetic markers. Here we characterize de novo endolithic microbial colonization using a sulfide microbial incubator within the hydrothermal vent Roane during a one-year deployment, with co-registered temperature, fluid chemistry and mineralogy. Taxanomic assessment of phylogenetic diversity via 16S rDNA extracted from the outer (40-70°C) and middle (150-240°C) chambers of the incubator revealed patterns of distribution comparable to previously published observations. However, quantitative and statistical analyses of 16S rDNA sequences from two chambers revealed very distinct communities, with less than 5% of the identified operational taxonomic units common to both chambers. Analyses of metagenomic data suggest an elevated potential for motility and select biosynthetic pathways in the outer chamber community. In contrast, the middle chamber community exhibits a greater potential for quorum sensing, biofilm formation and archaeal lipid biosynthesis. Striking differences in metabolic potential were also apparent. These data suggest that the distribution, abundance and physiological capacity of these communities is strongly governed by chemical and physical variability of the environment.

  13. Measurement of residual stress in plasma-sprayed TBC with a gradient of porosity and chemical composition

    Directory of Open Access Journals (Sweden)

    G. Moskal

    2007-08-01

    Full Text Available Purpose: The purpose of the research was identification of the residual stress in the top coat of different type of thermal barrier coating with gradient of chemical composition and gradient of porosity.Design/methodology/approach: The APS technique was used to deposition of gradient coating. As a bond coat the NiCrAlY overlay coating was applied. Top-coat consist in the case of gradient of porosity - YSZ with different thickness and porosity and in the case of chemical composition gradient YSZ with AMDRY 365-2 powder. The research allowed the identification of qualitative and quantitative phase constitution of top coat and residual stress measurement by sin2ψ method form surface of coatings.Findings: It was found that the dominant phase in all the top coats was tetragonal zirconia with minor addition of monoclinic type of ZrO2 and in the case of residual stress the tensile conditions was observed in the case of gradient porosity and compressive stresses in the case of chemical gradient.Research limitations/implications: Characterization of stress level in gradient TBC`s give possibility description of degradation mechanism of barrier coating.Practical implications: The results obtained allow the determination of the degree of life-time lost of the TBC system used as protection for creep resistant alloys.Originality/value: The results obtained are valuable contribution to the development of new typ of TBC. They enable the identification of the degradation mechanisms in YSZ / MCrAlY / substrate system.

  14. Active targeting in a random porous medium by chemical swarm robots with secondary chemical signaling

    Science.gov (United States)

    Grančič, Peter; Štěpánek, František

    2011-08-01

    The multibody dynamics of a system of chemical swarm robots in a porous environment is investigated. The chemical swarm robots are modeled as Brownian particles capable of delivering an encapsulated chemical payload toward a given target location and releasing it in response to an external stimulus. The presence of chemical signals (chemo-attractant) in the system plays a crucial role in coordinating the collective movement of the particles via chemotaxis. For a number of applications, such as distributed chemical processing and targeted drug delivery, the understanding of factors that govern the collective behavior of the particles, especially their ability to localize a given target, is of immense importance. A hybrid modeling methodology based on the combination of the Brownian dynamics method and diffusion problem coupled through the chemotaxis phenomena is used to analyze the impact of a varying signaling threshold and the strength of chemotaxis on the ability of the chemical robots to fulfill their target localization mission. The results demonstrate that the selected performance criteria (the localization half time and the success rate) can be improved when an appropriate signaling process is chosen. Furthermore, for an optimum target localization strategy, the topological complexity of the porous environment needs to be reflected.

  15. Raman spectroscopic insights into the chemical gradients within the wound plug of the green alga Caulerpa taxifolia.

    Science.gov (United States)

    Weissflog, Ina A; Grosser, Katharina; Bräutigam, Maximilian; Dietzek, Benjamin; Pohnert, Georg; Popp, Juergen

    2013-04-15

    The invasive unicellular green macroalga Caulerpa taxifolia has spread dramatically in the Mediterranean Sea over the last decades. Its success is based on rapid plug formation after wounding, to prevent the loss of cell content. This quick and efficient process involves the rapid transformation of the secondary metabolite caulerpenyne to the reactive 1,4-dialdehyde oxytoxin 2, which acts as a protein crosslinker. The main metabolites of the wound plug were identified as proteins, caulerpenyne derivatives, and sulfated polysaccharides. Because of a methodological deficit, however, the detailed distribution of the compounds within the wound plug of C. taxifolia was unknown. This study demonstrates the suitability of FT-Raman spectroscopy for the noninvasive in vivo determination of caulerpenyne and its derivatives, as well as β-carotene, from signals with special spectral features within the wound plug and the adjacent intact alga tissue, with a resolution of 100 μm. FT-Raman spectra allowed four different zones with distinct chemical compositions around the region of wounds to be characterized. Gradients of the investigated metabolites within the wound plug and the alga could be determined. Moreover, various caulerpenyne derivatives could be identified spectroscopically, and this has led to a mechanistic proposal for the internal and the external wound plug formation. PMID:23526760

  16. THE OPEN CLUSTER CHEMICAL ANALYSIS AND MAPPING SURVEY: LOCAL GALACTIC METALLICITY GRADIENT WITH APOGEE USING SDSS DR10

    International Nuclear Information System (INIS)

    The Open Cluster Chemical Analysis and Mapping (OCCAM) survey aims to produce a comprehensive, uniform, infrared-based data set for hundreds of open clusters, and constrain key Galactic dynamical and chemical parameters from this sample. This first contribution from the OCCAM survey presents analysis of 141 members stars in 28 open clusters with high-resolution metallicities derived from a large uniform sample collected as part of the Sloan Digital Sky Survey III/Apache Point Observatory Galactic Evolution Experiment. This sample includes the first high-resolution metallicity measurements for 22 open clusters. With this largest ever uniformly observed sample of open cluster stars we investigate the Galactic disk gradients of both [M/H] and [α/M]. We find basically no gradient in [α/M] across 7.9 kpc ≤ R GC ≤ 14.5 kpc, but [M/H] does show a gradient for R GC GC = 10 kpc. In particular, whereas fitting a single linear trend yields an [M/H] gradient of –0.09 ± 0.03 dex kpc–1—similar to previously measure gradients inside 13 kpc—by independently fitting inside and outside 10 kpc separately we find a significantly steeper gradient near the Sun (7.9 ≤ R GC ≤ 10) than previously found (–0.20 ± 0.08 dex kpc–1) and a nearly flat trend beyond 10 kpc (–0.02 ± 0.09 dex kpc–1)

  17. Chemical Signaling and Functional Activation in Colloidosome-Based Protocells.

    Science.gov (United States)

    Sun, Shiyong; Li, Mei; Dong, Faqin; Wang, Shengjie; Tian, Liangfei; Mann, Stephen

    2016-04-01

    An aqueous-based microcompartmentalized model involving the integration of partially hydrophobic Fe(III)-rich montmorillonite (FeM) clay particles as structural and catalytic building blocks for colloidosome membrane assembly, self-directed membrane remodeling, and signal-induced protocell communication is described. The clay colloidosomes exhibit size- and charge-selective permeability, and show dual catalytic functions involving spatially confined enzyme-mediated dephosphorylation and peroxidase-like membrane activity. The latter is used for the colloidosome-mediated synthesis and assembly of a temperature-responsive poly(N-isopropylacrylamide)(PNIPAM)/clay-integrated hybrid membrane. In situ PNIPAM elaboration of the membrane is coupled to a glucose oxidase (GOx)-mediated signaling pathway to establish a primitive model of chemical communication and functional activation within a synthetic "protocell community" comprising a mixed population of GOx-containing silica colloidosomes and alkaline phosphatase (ALP)-containing FeM-clay colloidosomes. Triggering the enzyme reaction in the silica colloidosomes gives a hydrogen peroxide signal that induces polymer wall formation in a coexistent population of the FeM-clay colloidosomes, which in turn generates self-regulated membrane-gated ALP-activity within the clay microcompartments. The emergence of new functionalities in inorganic colloidosomes via chemical communication between different protocell populations provides a first step toward the realization of interacting communities of synthetic functional microcompartments. PMID:26923794

  18. The Application of High–Gradient Magnetic Separation to Water Treatment by Means of Chemically Precipitated Magnetite

    OpenAIRE

    Hencl, V.; Mucha, P.

    1994-01-01

    Conditions of high–gradient magnetic separation (HGMS) of chemically precipitated magnetite, prepared from a waste material of the titanium white production were studied. The magnetite was used as a sorption material for the treatment of water from the Vltava River. Detailed experimental research resulted in a proposal for a technology of water treatment, schematic description of which is presented. The results of HGMS of chemically precipitated magnetite together with those of water treatmen...

  19. Quantification of signal modulation of erythrogenetic bone marrow in gradient echo sequences. Results from phantoms and patients with simultaneous determination of T2* relaxation times

    International Nuclear Information System (INIS)

    The signals from spongy bone on gradient echo sequences depend on the fat and water proton content as well as the differences in magnetic susceptibility at the border between the trabeculae and the bone marrow. From the signal intensities for different echo times, signal modulation was quantified by a special algorithm and at the same time the T2* relaxation time was calculated. Using a fat-water phantom, it was shown that the product of the initial fat and water signal intensity (modulation coefficient) is applicable to indicate the extent of signal modulation and thereby the chemical shift and, moreover, to indicate changes in the fat/water ratio sensitively. In 16 individuals of different ages (23 to 64 years, average 42.4 years) there was a tendency for the T2* relaxation time from the spongiosa of lumbar vertebrae to increase with age; this can be explained by a reduction in the trabecular content, causing reduction in the magnetic inhomogeneity of the bone marrow. The results indicate the usefulness of the sequence and the mathematical model for evaluating the spongy bone in cases of osteoporosis and of malignant haematological disorders. (orig.)

  20. Chemicals and chemoreceptors: ecologically relevant signals driving behavior in Drosophila.

    Directory of Open Access Journals (Sweden)

    Ana eDepetris-Chauvin

    2015-04-01

    Full Text Available Insects encounter a vast repertoire of chemicals in their natural environment, which can signal positive stimuli like the presence of a food source, a potential mate, or a suitable oviposition site as well as negative stimuli such as competitors, predators, or toxic substances reflecting danger. The presence of specialized chemoreceptors like taste and olfactory receptors allow animals to detect chemicals at short and long distances and accordingly, trigger proper behaviors towards these stimuli. Since the first description of olfactory and taste receptors in Drosophila fifteen years ago, our knowledge on the identity, properties, and function of specific chemoreceptors has increased exponentially. In the last years, multidisciplinary approaches combining genetic tools with electrophysiological techniques, behavioral recording, evolutionary analysis, and chemical ecology studies are shedding light on our understanding on the ecological relevance of specific chemoreceptors for the survival of Drosophila in their natural environment. In this review we discuss the current knowledge on chemoreceptors of both the olfactory and taste systems of the fruitfly. We focus on the relevance of particular receptors for the detection of ecologically relevant cues such as pheromones, food sources, and toxic compounds, and we comment on the behavioral changes that the detection of these chemicals induce in the fly. In particular, we give an updated outlook of the chemical communication displayed during one of the most important behaviors for fly survival, the courtship behavior. Finally, the ecological relevance of specific chemicals can vary depending on the niche occupied by the individual. In that regard, in this review we also highlight the contrast between adult and larval systems and we propose that these differences could reflect distinctive requirements depending on the change of ecological niche occupied by Drosophila along its life cycle.

  1. Effects of population density and chemical environment on the behavior of Escherichia coli in shallow temperature gradients

    International Nuclear Information System (INIS)

    In shallow temperature gradients, changes in temperature that bacteria experience occur over long time scales. Therefore, slow processes such as adaptation, metabolism, chemical secretion and even gene expression become important. Since these are cellular processes, the cell density is an important parameter that affects the bacteria's response. We find that there are four density regimes with distinct behaviors. At low cell density, bacteria do not cause changes in their chemical environment; however, their response to the temperature gradient is strongly influenced by it. In the intermediate cell-density regime, the consumption of nutrients becomes significant and induces a gradient of nutrients opposing the temperature gradient due to higher consumption rate at the high temperature. This causes the bacteria to drift toward low temperature. In the high cell-density regime, interactions among bacteria due to secretion of an attractant lead to a strong local accumulation of bacteria. This together with the gradient of nutrients, resulted from the differential consumption rate, creates a fast propagating pulse of bacterial density. These observations are a result of classical nonlinear population dynamics. At extremely high cell density, a change in the physiological state of the bacteria is observed. The bacteria, at the individual level, become cold seeking. This appears initially as a result of a change in the methylation level of the two most abundant sensing receptors, Tsr and Tar. It is further enforced at an even higher cell density by a change in the expression level of these receptors. (perspective)

  2. To signal or not to signal? Chemical communication by urine-borne signals mirrors sexual conflict in crayfish

    Directory of Open Access Journals (Sweden)

    Breithaupt Thomas

    2010-03-01

    Full Text Available Abstract Background Sexual selection theory predicts that females, being the limiting sex, invest less in courtship signals than males. However, when chemical signals are involved it is often the female that initiates mating by producing stimuli that inform about sex and/or receptivity. This apparent contradiction has been discussed in the literature as 'the female pheromone fallacy'. Because the release of chemical stimuli may not have evolved to elicit the male's courtship response, whether these female stimuli represent signals remains an open question. Using techniques to visualise and block release of urine, we studied the role of urine signals during fighting and mating interactions of crayfish (Pacifastacus leniusculus. Test individuals were blindfolded to exclude visual disturbance from dye release and artificial urine introduction. Results Staged female-male pairings during the reproductive season often resulted in male mating attempts. Blocking female urine release in such pairings prevented any male courtship behaviour. Artificial introduction of female urine re-established male mating attempts. Urine visualisation showed that female urine release coincides with aggressive behaviours but not with female submissive behaviour in reproductive interactions as well as in intersexual and intrasexual fights. In reproductive interactions, females predominately released urine during precopulatory aggression; males subsequently released significantly less urine during mating than in fights. Conclusions Urine-blocking experiments demonstrate that female urine contains sex-specific components that elicit male mating behaviour. The coincidence of chemical signalling and aggressive behaviour in both females and males suggests that urine release has evolved as an aggressive signal in both sexes of crayfish. By limiting urine release to aggressive behaviours in reproductive interactions females challenge their potential mating partners at the same

  3. Signal changes in gradient echo images of human brain induced by hypo- and hyperoxia

    DEFF Research Database (Denmark)

    Rostrup, Egill; Larsson, H B; Toft, P B; Garde, K; Henriksen, O

    1995-01-01

    The effect of hypoxia (inspired oxygen fraction, FiO2 of 10% and 16%) and hyperoxia (FiO2) of 100%) on gradient echo images of the brain using long echo times was investigated in six healthy volunteers (age 24-28 years). Different flip angles were used with an FiO2 of 10% to assess the importance...

  4. Relationship Between Root Chemical Signals and Grain Quality of Rice

    Institute of Scientific and Technical Information of China (English)

    YANG Jian-chang; CHANG Er-hua; ZHANG Wen-jie; WANG Zhi-qin; LIU Li-jun

    2007-01-01

    This study was designed to elucidate the relationship between root chemical signals and the quality of rice. Various rice genotypes were used. Zeatin (Z) + zeatin riboside (ZR), abscisic acid (ABA), 1-aminocylopropane -1-carboxylic acid (ACC), and organic acids in roots during grain filling and the appearance quality, cooking/eating quality were investigated. The correlations among them were analyzed. The results showed that Z + ZR concentrations in the roots at mid- and lategrain-filling stages were significantly and positively correlated with the gel consistency and alkali spreading value (r = 0.72* - 0.90**), whereas negatively correlated with the amylose content (r = -0.68* - -0.78**). ABA concentrations in roots at mid- grain-filling stage were significantly and negatively correlated with the gel consistency and alkali spreading value (r = -0.90** - -0.91**), and positively correlated with the amylose content (r = 0.87**). ACC concentrations in root exudates at mid-grain-filling stage were very significantly correlated with the percentage of chalky grains and chalkiness (r = 0.97** -0.98**), and those at late-grain-filling stage Were significantly correlated with chalkiness and chalky size (r = 0.69*-0.96**). The more the malic acid and succinic acid exuded from roots for a cultivar, the greater the breakdown values and the smaller the setback values in the starch profile, and the results were reversed for a cultivar with more tartaric acid and citric acid exuded from roots during the grain-filling period. The cultivar with more lactic acid in exudates had smaller gel consistency and alkali spreading values, but had greater amylose content. When roots were treated with exogenous ZR, ABA, and ACC during grain filling, effects of the chemicals on the rice quality were consistent with the relationships of the endogenous hormones (Z + ZR, ABA, and ACC) with the quality indexes. Using rape cake as organic fertilizer can increase the concentrations of malic acid and

  5. The Open Cluster Chemical Analysis and Mapping Survey: Local Galactic Metallicity Gradient with APOGEE using SDSS DR10

    CERN Document Server

    Frinchaboy, Peter M; Jackson, Kelly M; O'Connell, Julia; Meyer, Brianne; Zasowski, Gail; Majewski, Steven R; Chojnowksi, S Drew; Johnson, Jennifer A; Prieto, Carlos Allende; Beers, Timothy C; Bizyaev, Dmitry; Brewington, Howard; Cunha, Katia; Ebelke, Garrett; Perez, Ana Elia Garcia; Hearty, Frederick R; Holtzman, Jon; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Marchante, Moses; Meszaros, Szabolcs; Muna, Demitri; Nidever, David L; Oravetz, Daniel; Pan, Kaike; Schiavon, Ricardo P; Schneider, Donald P; Shetrone, Matthew; Simmons, Audrey; Snedden, Stephanie; Smith, Verne V; Wilson, John C

    2013-01-01

    The Open Cluster Chemical Analysis and Mapping (OCCAM) Survey aims to produce a comprehensive, uniform, infrared-based dataset for hundreds of open clusters, and constrain key Galactic dynamical and chemical parameters from this sample. This first contribution from the OCCAM survey presents analysis of 141 members stars in 28 open clusters with high-resolution metallicities derived from a large uniform sample collected as part of the SDSS-III/Apache Point Observatory Galactic Evolution Experiment (APOGEE). This sample includes the first high-resolution metallicity measurements for 22 open clusters. With this largest ever uniformly observed sample of open cluster stars we investigate the Galactic disk gradients of both [M/H] and [alpha/M]. We find basically no gradient across this range in [alpha/M], but [M/H] does show a gradient for R_{GC} < 10 kpc and a significant flattening beyond R_{GC} = 10 kpc. In particular, whereas fitting a single linear trend yields an [M/H] gradient of -0.09 +/- 0.03$ dex/kpc -...

  6. Commercial scale fabrication method for fabricating a gradient refractive-index rod: Overcoming volume shrinkage and chemical restrictions.

    Science.gov (United States)

    Cho, Hansol; Son, Young Mok; Kim, Mu Gyeom; Ra, Byoung Joo; Park, Joon-Yong; Lee, Seung Hui; Choi, Jin Sung; Song, Min Young; Park, O Ok; Kim, Youn Cheol; Hwang, Jin Taek

    2006-10-01

    We report a fabrication method for a gradient refractive-index polymeric object from a binary comonomer system, regardless of the monomers' reactivity ratio and the molar volume criteria of gradient refractive-index development. To fabricate a large gradient refractive-index rod consisting of a methyl methacrylate and 2,2,3,3-tetrafluoropropyl methacrylate comonomer pair that has not been used for fabrication of a copolymer gradient refractive-index rod by previous conventional methods because of chemical restrictions in molar volume and reactivity ratio difference, we use the so-called successive UV polymerization in a controlled radial volume in conjunction with an automatic refill reactor. Simultaneously and automatically, the volume shrinkage problem, an inevitable shortcoming for the fabrication of a large polymeric object in a commercial production scale, is overcome and exploited. The theoretical features of the refractive-index profile generation of this method are also compared with those of conventional methods for which the chemical restrictions of monomers are crucial for the shape of a refractive-index profile. PMID:16983409

  7. Chemical signals associated with life inhibit necrophoresis in Argentine ants.

    Science.gov (United States)

    Choe, Dong-Hwan; Millar, Jocelyn G; Rust, Michael K

    2009-05-19

    One of the most conspicuous and stereotyped activities of social insects such as ants and honey bees is necrophoresis, the removal of dead colony members from the nest. Previous researchers suggested that decomposition products such as fatty acids trigger necrophoric behavior by ant workers. However, fatty acids elicit both foraging and necrophoric responses, depending on the current nest activities (e.g., feeding or nest maintenance). Furthermore, workers often carry even freshly killed workers (dead for disappear from the cuticle within about 1 h after death. We demonstrate how this phenomenon supports an alternative mechanism of ant necrophoresis in which the precise recognition and rapid removal of dead nestmates are elicited by the disappearance of these chemical signals associated with life. PMID:19416815

  8. Radial metallicity gradients in spiral galaxies from H II regions and planetary nebulae: probing galactic chemical evolution

    Science.gov (United States)

    Stanghellini, Letizia

    2015-08-01

    Radial metallicity gradients, typically observed in spiral galaxies, are excellent constraints for chemical evolution models. The contemporary studies of the two stellar populations, whose progenitors have formed at different times, yield to the chemical and time constraining of the models. In this context, planetary nebula and HII region analysis proved to be ideal two-epochs test populations. We present an assortment of galaxies whose oxygen abundances have been determined both with weak- and strong-line methods, and whose radial metallicity gradients and their evolution in time have disclosed very interesting correlations with the galaxy characteristics. New results from our Gemini/GMOS observations, and a review of the best literature data, set the stage for a better understanding of spiral galaxy evolution.

  9. Synthesis and Characterization of Biomimetic Hydroxyapatite Nanoconstruct Using Chemical Gradient across Lipid Bilayer.

    Science.gov (United States)

    Koirala, Mukund Bahadur; Nguyen, Tuyen Duong Thanh; Pitchaimani, Arunkumar; Choi, Seong-O; Aryal, Santosh

    2015-12-16

    In this study, we synthesized biomimetic hydroxyapatite nanoconstruct (nanosized hydroxyapatite, NHAp) using a double emulsion technique combined with a chemical gradient across a lipid bilayer for surface modification of a titanium (Ti) implant. The synthesized NHAp was characterized by dynamic light scattering, X-ray diffraction, transmission electron microscopy, and Fourier transform infrared (FTIR) spectroscopy, and it was further tested for its biocompatibility and in vitro proliferation efficacy using normal human osteoblasts (NHOst). The results showed that the synthesized NHAp had a hydrodynamic diameter of ∼200 nm with high aqueous stability. The chemistry of the NHAp was confirmed by FTIR spectroscopic analysis. Typical FTIR vibrational bands corresponding to the phosphate group (PO4(3-)) present in hydroxyapatite (HAp) were observed at 670, 960, and 1000 cm(-1). A broad band at 3500 cm(-1) confirmed the presence of a structural -OH group in the NHAp. Powder X-ray crystallographic diffraction further confirmed the formation of NHAp with characteristic reflections in (002), (211), (130), and (213) planes at respective 2θ degrees. These reflection planes are similar to those of typical HAp crystallized toward (002) and (211) crystallographic planes. The mechanism of the formation of NHAp was studied using the fluorescence resonance energy transfer (FRET) technique. The FRET study showed the fluorescent recovery of a donor fluorophore and the mechanism of the insertion of lipids into nanodroplets obtained from the first water-in-oil (w/o) emulsion during the formation of the second oil-in-water (o/w) emulsion. With these confirmations, we further studied NHOst cell proliferation on a Ti surface. When NHOst were cultured on the Ti surface coated with the NHAp, a distinct proliferation pattern and cell-cell communication via cytoplasmic extension on the substrate surface were observed. In contrast, a bare Ti surface showed diminished cell size with minimal

  10. The radial metallicity gradients in the Milky Way thick disk as fossil signatures of a primordial chemical distribution

    CERN Document Server

    Curir, A; Spagna, A; Lattanzi, M G; Fiorentin, P Re; Diaferio, A

    2014-01-01

    In this letter we examine the evolution of the radial metallicity gradient induced by secular processes, in the disk of an $N$-body Milky Way-like galaxy. We assign a [Fe/H] value to each particle of the simulation according to an initial, cosmologically motivated, radial chemical distribution and let the disk dynamically evolve for 6 Gyr. This direct approach allows us to take into account only the effects of dynamical evolution and to gauge how and to what extent they affect the initial chemical conditions. The initial [Fe/H] distribution increases with R in the inner disk up to R ~ 10 kpc and decreases for larger R. We find that the initial chemical profile does not undergo major transformations after 6 Gyr of dynamical evolution. The final radial chemical gradients predicted by the model in the solar neighborhood are positive and of the same order of those recently observed in the Milky Way thick disk. We conclude that: 1) the spatial chemical imprint at the time of disk formation is not washed out by sec...

  11. Dielectrophoretic characterization of cells in a stationary nanoliter droplet array with generated chemical gradients.

    Science.gov (United States)

    Ben-Arye, Tom; Park, Sinwook; Shemesh, Jonathan; Peer, Dan; Levenberg, Shulamit; Yossifon, Gilad

    2015-10-01

    A novel design of reusable microfluidic platform that generates a stationary nanoliter droplet array (SNDA) for cell incubation and analysis, equipped with a complementary array of individually addressable electrodes for each microwell is studied. Various solute concentration gradients were generated between the wells where dielectrophoresis (DEP) was used to characterize the effect of the gradients on the cell's response. The feasibility of generating concentration gradients and observation of DEP responses was demonstrated using a gradient of salts in combination with microparticles and viable cells. L1210 Lymphoma cells were used as the model cells in these experiments. Lymphoma cells' cross-over frequency (COF) decreased with increasing stress conditions. Specifically, a linear decrease in the cell COF was measured as a function of solution tonicity and blebbistatin dose. Lymphoma cells were incubated under a gradient of the chemotherapeutic agent doxorubicin (DOX), which led to saturation in the cell-COF response at 30 nM DOX, demonstrating the potential of the platform in screening of label-free drugs. PMID:26286862

  12. Chemical signals and their interactions change transpiration processes in tomato wild-type and flacca mutant

    DEFF Research Database (Denmark)

    Prokic, Ljiljana; Wollenweber, Bernd; Stikic, Radmila

    2011-01-01

    effects of chemicalsignals on the mechanism of transpiration of isolated leaves of L. esculentum Mill. cv. Ailsa Craig (WT) and mutant flacca. In bioassays, exogenic activity of different ABA concentrations and pH were tested in both genotype of tomato in order to stimulate chemical signals occurring...... drought conditions xylem sap pH was higher in leaves extract than in extracts of roots, indicating that an apoplastic pH gradient exists in WT, but not in flacca plants. So, reactions of flacca could not be only the result of lower ABA concentration, but also the result of an altered sensitivity to...

  13. Design of parallel microfluidic gradient-generating networks for studying cellular response to chemical stimuli

    Institute of Scientific and Technical Information of China (English)

    Lihui WANG; Dayu LIU; Bo WANG; Jie SUN; Lianhong LI

    2008-01-01

    A microfluidic chip featuring laminar flow-based parallel gradient-generating networks was designed and fabricated. The microchip contains 5 gradient genera-tors and 30 cell chambers where the resulting concentra-tion gradients of drugs are delivered to stimulate on-chip cultured cells. The microfluidics exploits the advantage of lab-on-a-chip technology by integrating the generation of drug concentration gradients and a series of cell opera-tions including seeding, culture, stimulation and staining into a chip. The microfluidic network was patterned on a glass wafer, which was further bonded to a PDMS film. A series of weir structures were fabricated on the cell culture reservoir to facilitate cell positioning and seeding. Cell injection and fluid delivery were controlled by a syringe pump. Steady parallel concentration gradients were gen-erated by flowing two fluids in each network. Over time observation shows that the microchip was suitable for cell seeding and culture. The microchip described above was applied in studying the role of reduced glutathione (GSH) in mediating chemotherapy sensitivity of MCF-7 cells. MCF-7 cells were treated with concentration gradients of As2O3 and N-acetyl cysteine (NAC) for GSH modu-lation, followed by exposure to adriamycin. GSH levels were down-regulated upon As203 treatment and up-regu-lated upon NAC treatment. Suppression of intracellular GSH by treatment with As2O3 has been shown to increase sensitivity to adriamycin. Conversely, elevation of intra-cellular GSH by treatment with NAC leads to increased drug resistance. The integrated microfluidic chip is able to perform multiparametric pharmacological profiling with easy operation, and thus holds great potential for extra-polation to the cell based high-content drug screening.

  14. Interpopulational Variations in Sexual Chemical Signals of Iberian Wall Lizards May Allow Maximizing Signal Efficiency under Different Climatic Conditions.

    Directory of Open Access Journals (Sweden)

    José Martín

    Full Text Available Sexual signals used in intraspecific communication are expected to evolve to maximize efficacy under a given climatic condition. Thus, chemical secretions of lizards might evolve in the evolutionary time to ensure that signals are perfectly tuned to local humidity and temperature conditions affecting their volatility and therefore their persistence and transmission through the environment. We tested experimentally whether interpopulational altitudinal differences in chemical composition of femoral gland secretions of male Iberian wall lizards (Podarcis hispanicus have evolved to maximize efficacy of chemical signals in different environmental conditions. Chemical analyses first showed that the characteristics of chemical signals of male lizards differed between two populations inhabiting environments with different climatic conditions in spite of the fact that these two populations are closely related genetically. We also examined experimentally whether the temporal attenuation of the chemical stimuli depended on simulated climatic conditions. Thus, we used tongue-flick essays to test whether female lizards were able to detect male scent marks maintained under different conditions of temperature and humidity by chemosensory cues alone. Chemosensory tests showed that chemical signals of males had a lower efficacy (i.e. detectability and persistence when temperature and dryness increase, but that these effects were more detrimental for signals of the highest elevation population, which occupies naturally colder and more humid environments. We suggest that the abiotic environment may cause a selective pressure on the form and expression of sexual chemical signals. Therefore, interpopulational differences in chemical profiles of femoral secretions of male P. hispanicus lizards may reflect adaptation to maximize the efficacy of the chemical signal in different climates.

  15. Generation of tunable and pulsatile concentration gradients via microfluidic network

    KAUST Repository

    Zhou, Bingpu

    2014-06-04

    We demonstrate a compact Polydimethylsiloxane microfluidic chip which can quickly generate ten different chemical concentrations simultaneously. The concentration magnitude of each branch can be flexibly regulated based on the flow rate ratios of the two injecting streams. The temporal/pulsatile concentration gradients are achieved by integrating on-chip pneumatic actuated valves controlled by the external signals. The temporal concentration gradients can also be tuned precisely by varying applied frequency and duty cycle of the trigger signal. It is believed that such microdevice will be potentially used for some application areas of producing stable chemical gradients as well as allowing fast, pulsatile gradient transformation in seconds.

  16. Species-specific Variation in the Importance of the Spectral Quality Gradient in Canopies as a Signal for Photosynthetic Resource Partitioning

    OpenAIRE

    Pons, Thijs L.; de JONG-VAN BERKEL, YVONNE E. M.

    2004-01-01

    • Background and Aims Plants adjust the distribution of photosynthetic capacity and chlorophyll to canopy density. The importance of the gradient in the red : far-red ratio (R : FR) relative to the irradiance gradient was studied for its perception with respect to this partitioning of photosynthetic resources. Whether the relative importance of these two signals varied between six species of different growth habit (Phaseolus vulgaris, Lysimachia vulgaris, Hedera helix, Ficus benjamina, Carex ...

  17. Diffusion-weighted imaging of the liver at 3 T using section-selection gradient reversal: emphasis on chemical shift artefacts and lesion conspicuity

    International Nuclear Information System (INIS)

    Aim: To assess the value of section-selection gradient reversal (SSGR) in liver diffusion-weighted imaging (DWI) by comparing it to conventional DWI with an emphasis on chemical shift artefacts and lesion conspicuity. Materials and methods: Forty-eight patients (29 men and 19 women; age range 33–80 years) with 48 liver lesions underwent two DWI examinations using spectral presaturation with inversion recovery fat suppression with and without SSGR at 3 T. Two reviewers evaluated each DWI (b = 100 and b = 800 image) with respect to chemical shift artefacts and liver lesion conspicuity using five-point scales and performed pairwise comparisons between the two DWIs. The signal-to-noise ratio (SNR) of the liver and the lesion and the lesion–liver contrast-to-noise ratio (CNR) were also calculated. Results: SSGR-DWI was significantly better than conventional DWI with respect to chemical shift artefacts and lesion conspicuity in both separate reviews and pairwise comparisons (p < 0.05). There were significant differences in the SNR of the liver (b = 100 and b = 800 images) and lesion (b = 800) between SSGR-DWI and conventional DWI (p < 0.05). Conclusion: Applying the SSGR method to DWI using SPIR fat suppression at 3 T could significantly reduce chemical shift artefacts without incurring additional acquisition time or SNR penalties, which leads to increased conspicuity of focal liver lesions. - Highlights: • Chemical shift artefact in liver DWI is markedly decreased by applying SSGR. • Liver lesion conspicuity is improved by applying SSGR to DWI. • In SNR of the liver, SSGR-DWI is better than conventional DWI

  18. Elimination of surface signals by a surface-spoiling magnetic field gradient. Theoretical optimization and application to human in vivo NMR spectroscopy

    Science.gov (United States)

    Jehenson, P.; Bloch, G.

    W. Chen and J. J. H. Ackerman ( J. Magn. Reson.82, 655, 1989; NMR Biomed.2, 267, 1989) used a superficial magnetic field gradient to eliminate surface signals when observing rat liver in vivo. We have developed a method for computing the optimal gradient coil for a given in vivo application. An analytical solution for the magnetic field created by a planar array of antiparallel current elements was derived for the calculations. The surface-signal suppression obtained by gradient coils of various sizes is presented in a synthetic plot which directly provides the electrical and geometrical parameters of the optimal coil as well as the residual signal in the deep-lying region of interest. This approach was applied to in vivo31P and 31C spectroscopy of the human liver. Hepatic glycogen was detected by natural-abundance 13C NMR without contamination from muscle glycogen, and physiological variation during starvation could be observed.

  19. The effect of temperature gradients on endocrine signaling and antioxidant gene expression during Chironomus riparius development.

    Science.gov (United States)

    Park, Kiyun; Kwak, Ihn-Sil

    2014-02-01

    Temperature is one of the most important environmental factors affecting the biological processes of aquatic species. To investigate the potential effects of temperature on the developmental processes of aquatic invertebrates, we analyzed biological and molecular transcriptional responses during Chironomus riparius development, including five stages spanning from embryo to adult stages. We assessed the temperature change-induced reduction of survival rate, changes in biological development including the male:female ratio in emerged adults, the success rates of pupation and emergence, and the developmental timing of pupation and emergence. The increased temperature induced expression of endocrine signaling genes, such as the ecdysone receptor, ultraspiracle (ortholog of the RXR), and the estrogen-related receptor in the fourth-instar larval and pupal stages of C. riparius development. Altered temperature also affected the activity of antioxidant genes, including catalase, peroxidase, glutathione peroxidase, and superoxide dismutase during the fourth-instar larval to adult stages of C. riparius development, as a result of altered development. Increased temperature during the fourth-instar larval stage increased oxidative stress in pupae and adults. Responses of antioxidant genes to increased temperature occurred in a developmental stage-dependent manner. However, reduced temperature did not induce the expression of antioxidant genes in a developmental stage-dependent manner, although it did induce oxidative stress during C. riparius development. Increased temperature also caused greater toxicity of di-ethylhexyl phthalate (DEHP) in fourth-instar larvae. Our findings suggest that altered temperatures may disturb the invertebrate hormone system and developmental processes by inducing oxidative stress in aquatic environments. PMID:24239821

  20. Do chemical gradients within soil aggregates reflect plant/soil interactions?

    Science.gov (United States)

    Krüger, Jaane; Hallas, Till; Kinsch, Lena; Stahr, Simon; Prietzel, Jörg; Lang, Friederike

    2016-04-01

    As roots and hyphae often accumulate at the surface of soil aggregates, their formation and turnover might be related to the bioavailability especially of immobile nutrients like phosphorus. Several methods have been developed to obtain specific samples from aggregate surfaces and aggregate cores and thus to investigate differences between aggregate shell and core. However, these methods are often complex and time-consuming; therefore most common methods of soil analysis neglect the distribution of nutrients within aggregates and yield bulk soil concentrations. We developed a new sequential aggregate peeling method to analyze the distribution of different nutrients within soil aggregates (4-20 mm) from four forest sites (Germany) differing in concentrations of easily available mineral P. Aggregates from three soil depths (Ah, BwAh, Bw) were isolated, air-dried, and peeled with a sieving machine performing four sieving levels with increasing sieving intensity. This procedure was repeated in quadruplicate, and fractions of the same sample and sieving level were pooled. Carbon and N concentration, citric acid-extractable PO4 and P, as well as total element concentrations (P, K, Mg, Ca, Al, Fe) were analyzed. Additionally, synchrotron-based P K-edge XANES spectroscopy was applied on selected samples to detect P speciation changes within the aggregates. The results reveal for most samples a significantly higher C and N concentration at the surface compared to the interior of the aggregates. Carbon and N gradients get more pronounced with increasing soil depth and decreasing P status of study sites. This might be explained by lower aggregate turnover rates of subsoil horizons and intense bioturbation on P-rich sites. This assumption is also confirmed by concentrations of citric acid-extractable PO4 and P: gradients within aggregates are getting more pronounced with increasing soil depth and decreasing P status. However, the direction of these gradients is site

  1. Transport of a liquid water and methanol mixture through carbon nanotubes under a chemical potential gradient

    Science.gov (United States)

    Zheng, Jie; Lennon, Erin M.; Tsao, Heng-Kwong; Sheng, Yu-Jane; Jiang, Shaoyi

    2005-06-01

    In this work, we report a dual-control-volume grand canonical molecular dynamics simulation study of the transport of a water and methanol mixture under a fixed concentration gradient through nanotubes of various diameters and surface chemistries. Methanol and water are selected as fluid molecules since water represents a strongly polar molecule while methanol is intermediate between nonpolar and strongly polar molecules. Carboxyl acid (-COOH) groups are anchored onto the inner wall of a carbon nanotube to alter the hydrophobic surface into a hydrophilic one. Results show that the transport of the mixture through hydrophilic tubes is faster than through hydrophobic nanotubes although the diffusion of the mixture is slower inside hydrophilic than hydrophobic pores due to a hydrogen network. Thus, the transport of the liquid mixture through the nanotubes is controlled by the pore entrance effect for which hydrogen bonding plays an important role.

  2. Efficient inclusion body processing using chemical extraction and high gradient magnetic fishing

    DEFF Research Database (Denmark)

    Heebøll-Nielsen, Anders; Choe, W.S.; Middelberg, A.P.J.; Thomas, Owen R. T.

    2003-01-01

    In this study we introduce a radical new approach for the recovery of proteins expressed in the form of inclusion bodies, involving W chemical extraction from the host cells, (ii) adsorptive capture of the target protein onto small magnetic adsorbents, and (iii) subsequent rapid collection of the...

  3. Chemical reactions accompanying fluid flow through granite held in a temperature gradient

    Science.gov (United States)

    Moore, Diane E.; Morrow, C.A.; Byerlee, J.D.

    1983-01-01

    Distilled water was passed at a low rate down a temperature gradient through cylinders of Barre and Westerly Granite. Temperatures ranged from 80-100??C at the outer edges of the cylinders to 250-300??C in central, drilled holes which housed the heating coils. The measured permeabilities of the granite cylinders decreased by as much as two orders of magnitude in experiments of 1-3 weeks' duration. The amount of permeability decrease varied directly with temperature and inversely with the rate of fluid flow. The compositions of the fluids discharged from the granites were functions of temperature and flow rate as well as mineral composition, with dissolved silica concentrations showing trends different from those of the other analyzed species. Fluids from experiments run at higher temperatures but at much lower initial rates of fluid flow had higher concentrations of most ions but substantially lower dissolved silica contents. In contrast, an increase in temperature at similar rates of fluid flow resulted in higher silica concentrations. In the experiments, the distilled water acquired enough dissolved materials at high temperatures to become supersaturated with respect to several minerals at the low-temperature edges of the cylinders. Some of this material, particularly silica, was deposited along grain boundaries and microfractures, causing the observed permeability decreases. The very low rates of fluid flow in some high-temperature experiments significantly increased the rates of SiO2 precipitation and reduced dissolved silica concentrations relative to other species in the discharged fluids. ?? 1983.

  4. Chemical bond as a test of density-gradient expansions for kinetic and exchange energies

    International Nuclear Information System (INIS)

    Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al. and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N2 and F2, which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules

  5. The Migration of Cancer Cells in Gradually Varying Chemical Gradients and Mechanical Constraints

    Directory of Open Access Journals (Sweden)

    Smitha M. N. Rao

    2014-01-01

    Full Text Available We report a novel approach to study cell migration under physical stresses by utilizing established growth factor chemotaxis. This was achieved by studying cell migration in response to epidermal growth factor (EGF chemoattraction in a gradually tapered space, imposing mechanical stresses. The device consisted of two 5-mm-diameter chambers connected by ten 600 µm-long and 10 µm-high tapered microchannels. The taper region gradually changes the width of the channel. The channels tapered from 20 µm to 5 µm over a transition length of 50 µm at a distance of 250 µm from one of the chambers. The chemoattractant drove cell migration into the narrow confines of the tapered channels, while the mechanical gradient clearly altered the migration of cells. Cells traversing the channels from the wider to narrow-end and vice versa were observed using time-lapsed imaging. Our results indicated that the impact of physical stress on cell migration patterns may be cell type specific.

  6. Uranium geochemistry on the Amazon shelf: Chemical phase partitioning and cycling across a salinity gradient

    International Nuclear Information System (INIS)

    The size distribution of U was examined in surface waters of the Amazon shelf. Water samples were collected during a low discharge river stage across a broad salinity gradient (0.3-35.4%) and fractionated by planar filtration and tangential-flow ultrafiltration into (1) solution (Us, c, 10,000 MW-0.4 μm), (3) dissolved (Ud p >0.4 μm) phases. Concentrations of colloidal U comprise up to 92% of the dissolved U fraction at the river mouth and attain highest values (∼0.45 μg/L) in the productive, biogenic region of the Amazon shelf (salinities above ∼20%). Ud and Uc distributions are highly nonconservative relative to ideal dilution of river water and seawater, indicating extensive removal at salinities below ∼10%. The distribution of Us also shows some nonconservative behavior, yet removal, if any, is minimal. Saltwater-induced precipitation and aggregation of riverine colloidal material is most likely the dominant mechanism of U removal in the low salinity, terrigenous region of the Amazon shelf. There is evident of a substantial colloidal U input (∼245% of the riverine Uc flux) into surface waters above 5%. Such Uc enrichment most likely is the result of colloidal U-rich porewater diffusion/advection from the seabed and fluid muds or shelf-wide particle-colloid disaggregation. Removal of solution and dissolved phase U via a colloidal intermediate and Uc aggregation in terms of coagulation phase U via a colloidal intermediate and Uc aggregation was examined in terms of coagulation theory. The high reactive nature of all U phases on the Amazon shelf suggests that remobilization and fractionation of U may also occur in other river-influenced coastal environments

  7. Gradients in dust chemical composition in protoplanetary disks: analogies with the Solar System

    Science.gov (United States)

    Riaz, Basmah; Kelley, M.; Campins, H.

    2014-11-01

    Clues to planet-forming processes are provided by the properties of the dust grains in protoplanetary disks and in cometary nuclei in our own Solar System. We present a compositional analysis of the 10µm and 20µm silicate emission features for young protoplanetary disks around FGKM stars. We find an increase in the crystallinity levels towards larger radii, such that the median crystalline mass fraction is higher in the outer cold disk region compared to the inner warm parts of the disk. For nearly 80% of the disks, the mass fraction of small ISM-like dust grains is negligible (analogy to comets. In this context, we will discuss the applicability of the various mechanisms that have been proposed for comets on the formation and the outward transport of high-temperature material. A (weak) anti-correlation between the X-ray emission strength and the extent of crystallinity in the disk is observed, suggesting X-rays to be an important dust amorphization agent in these disks. This work has highlighted the ubiquity of Solar System like chemical signatures in young protoplanetary disks, and suggests that protoplanets that form closer to a low-mass star can have a different chemical composition from those that formed farther away.

  8. Roughing Up Smoothened: Chemical Modulators of Hedgehog Signaling

    OpenAIRE

    King, Randall Wharton

    2002-01-01

    Small-molecule antagonists of Hedgehog-pathway signaling, such as cyclopamine, have been known for some time. Now, small-molecule agonists of the Hedgehog pathway have also been identified. The finding that both antagonists and agonists target the protein Smoothened supports the emerging hypothesis that Smoothened may be regulated by endogenous small molecules.

  9. Tree rings provide early warning signals of jack pine mortality across a moisture gradient in the southern boreal forest

    Science.gov (United States)

    Mamet, S. D.; Chun, K. P.; Metsaranta, J. M.; Barr, A. G.; Johnstone, J. F.

    2015-08-01

    Recent declines in productivity and tree survival have been widely observed in boreal forests. We used early warning signals (EWS) in tree ring data to anticipate premature mortality in jack pine (Pinus banksiana)—an extensive and dominant species occurring across the moisture-limited southern boreal forest in North America. We sampled tree rings from 113 living and 84 dead trees in three soil moisture regimes (subxeric, submesic, subhygric) in central Saskatchewan, Canada. We reconstructed annual increments of tree basal area to investigate (1) whether we could detect EWS related to mortality of individual trees, and (2) how water availability and tree growth history may explain the mortality warning signs. EWS were evident as punctuated changes in growth patterns prior to transition to an alternative state of reduced growth before dying. This transition was likely triggered by a combination of severe drought and insect outbreak. Higher moisture availability associated with a soil moisture gradient did not appear to reduce tree sensitivity to stress-induced mortality. Our results suggest tree rings offer considerable potential for detecting critical transitions in tree growth, which are linked to premature mortality.

  10. Target sites for chemical regulation of strigolactone signaling

    Directory of Open Access Journals (Sweden)

    Hidemitsu eNakamura

    2014-11-01

    Full Text Available Demands for plant growth regulators (chemicals that control plant growth are increasing globally, especially in developing countries. Both positive and negative plant growth regulators are widely used to enhance crop production and to suppress unwanted shoot growth, respectively. Strigolactones (SLs are multifunctional molecules that function as phytohormones, inhibiting shoot branching and also functioning in the rhizospheric communication with symbiotic fungi and parasitic weeds. Therefore, it is anticipated that chemicals that regulate the functions of SLs will be widely used in agricultural applications. Although the SL biosynthetic pathway is not fully understood, it has been demonstrated that beta-carotene isomerases, carotenoid cleavage dioxygenases (CCDs, and a cytochrome P450 monooxygenase are involved in strigolactone biosynthesis. A CCD inhibitor, abamine, which is also an inhibitor of abscisic acid biosynthesis, reduces the levels of SL in several plant species and reduces the germination rate of Orobanche minor seeds grown with tobacco. On the basis of the structure of abamine, several chemicals have been designed to specifically inhibit CCDs during SL synthesis. Cytochrome P450 monooxygenase is another target enzyme in the development of SL biosynthesis inhibitors, and the triazole-derived TIS series of chemicals is known to include SL biosynthesis inhibitors, although their target enzyme has not been identified. Recently, DWARF14 (D14 has been shown to be a receptor for SLs, and the D-ring moiety of SL is essential for its recognition by D14. A variety of SL agonists are currently under development and most agonists commonly contain the D-ring or a D-ring-like moiety. Several research groups have also resolved the crystal structure of D14 in the last two years. It is expected that this information on the D14 structure will be invaluable not only for developing SL agonists with novel structures but also in the design of inhibitors

  11. Does chemical aposematic (warning) signaling occur between host plants and their potential parasitic plants?

    OpenAIRE

    Lev-Yadun, Simcha

    2013-01-01

    Aposematism (warning) signaling is a common defensive mechanism toward predatory or herbivorous animals, i.e., interactions between different trophic levels. I propose that it should be considered at least as a working hypothesis that chemical aposematism operates between certain host plants and their plant predators, parasitic plants, and that although they are also plants, they belong to a higher trophic level. Specific host plant genotypes emit known repelling chemical signals toward paras...

  12. Oxytocin antagonist disrupts male mouse medial amygdala response to chemical-communication signals

    OpenAIRE

    Samuelsen, Chad L.; Meredith, Michael

    2011-01-01

    The male mouse medial amygdala is an important site for integration of main and accessory olfactory information. Exposure to biologically relevant chemical signals from the same species (conspecific) results in a general pattern of immediate early gene (IEG) expression in medial amygdala different from that elicited by chemical signals from other species (heterospecific), of no demonstrable biological relevance. The neuropeptide oxytocin (OT) in the medial amygdala has been shown to be necess...

  13. Facile multi-dimensional profiling of chemical gradients at the millimetre scale.

    Science.gov (United States)

    Chen, Chih-Lin; Hsieh, Kai-Ta; Hsu, Ching-Fong; Urban, Pawel L

    2016-01-01

    A vast number of conventional physicochemical methods are suitable for the analysis of homogeneous samples. However, in various cases, the samples exhibit intrinsic heterogeneity. Tomography allows one to record approximate distributions of chemical species in the three-dimensional space. Here we develop a simple optical tomography system which enables performing scans of non-homogeneous samples at different wavelengths. It takes advantage of inexpensive open-source electronics and simple algorithms. The analysed samples are illuminated by a miniature LCD/LED screen which emits light at three wavelengths (598, 547 and 455 nm, corresponding to the R, G, and B channels, respectively). On presentation of every wavelength, the sample vial is rotated by ∼180°, and videoed at 30 frames per s. The RGB values of pixels in the obtained digital snapshots are subsequently collated, and processed to produce sinograms. Following the inverse Radon transform, approximate quasi-three-dimensional images are reconstructed for each wavelength. Sample components with distinct visible light absorption spectra (myoglobin, methylene blue) can be resolved. The system was used to follow dynamic changes in non-homogeneous samples in real time, to visualize binary mixtures, to reconstruct reaction-diffusion fronts formed during the reduction of 2,6-dichlorophenolindophenol by ascorbic acid, and to visualize the distribution of fungal mycelium grown in a semi-solid medium. PMID:26541202

  14. The Role of Sexual Selection in the Evolution of Chemical Signals in Insects

    OpenAIRE

    Sandra Steiger; Johannes Stökl

    2014-01-01

    Chemical communication is the most ancient and widespread form of communication. Yet we are only beginning to grasp the complexity of chemical signals and the role they play in sexual selection. Focusing on insects, we review here the recent progress in the field of olfactory-based sexual selection. We will show that there is mounting empirical evidence that sexual selection affects the evolution of chemical traits, but form and strength of selection differ between species. Studies indicate t...

  15. Double-echo gradient chemical shift MR imaging fails to differentiate minimal fat renal angiomyolipomas from other homogeneous solid renal tumors

    International Nuclear Information System (INIS)

    Highlights: •Diagnosis of AMLs with minimal fat (mfAMLs) is still challenging with MRI. •Drop of signal on opposed-phase MR imaging is not specific of mfAMLs. •Double-echo gradient-echo sequences cannot accurately differentiate renal mfAMLs from other renal tumors. -- Abstract: Objectives: The purpose of this retrospective study was to evaluate the diagnostic performance of double-echo gradient chemical shift (GRE) magnetic resonance (MR) imaging for the differentiation of angiomyolipomas with minimal fat (mfAML) from other homogeneous solid renal tumors. Methods: Between 2005 and 2010 in two institutions, all histologically proven homogenous solid renal tumors imaged with computed tomography and MR imaging, including GRE sequences, have been retrospectively selected. A total of 118 patients (mean age: 61 years; range: 20–87) with 119 tumors were included. Two readers measured independently the signal intensity (SI) on GRE images and calculated SI index (SII) and tumor-to-spleen ratio (TSR) on in-phase and opposed-phase images. Intra- and interreader agreement was obtained. Cut-off values were derived from the receiver operating characteristic (ROC) curve analysis. Results: Twelve mfAMLs in 11 patients were identified (mean size: 2.8 cm; range: 1.2–3.5), and 107 non-AML tumors (3.2 cm; 1–7.8) in 107 patients. The intraobserver reproducibility of SII and TSR was excellent with an intraclass correlation coefficient equal to 0.99 [0.98–0.99]. The coefficient of correlation between the readers was 0.99. The mean values of TSR for mfAMLs and non-mfAMLs were −7.0 ± 22.8 versus −8.2 ± 21.2 for reader 1 and −6.7 ± 22.8 versus −8.4 ± 20.9 for reader 2 respectively. No significant difference was noticed between the two groups for SII (p = 0.98) and TSR (p = 0.86). Only 1 out of 12 mfAMLs and 11 of 107 non-AML tumors presented with a TSR inferior to −30% (p = 0.83). Conclusion: In a routine practice, GRE sequences cannot be a confident tool to

  16. Double-echo gradient chemical shift MR imaging fails to differentiate minimal fat renal angiomyolipomas from other homogeneous solid renal tumors

    Energy Technology Data Exchange (ETDEWEB)

    Ferré, R., E-mail: kn638@yahoo.fr [Department of Radiology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France); Cornelis, F. [Department of Radiology, Pellegrin Hospital, Place Amélie Raba Léon, 33076 Bordeaux (France); Verkarre, V. [Department of Pathology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France); Eiss, D.; Correas, J.M. [Department of Radiology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France); Grenier, N. [Department of Radiology, Pellegrin Hospital, Place Amélie Raba Léon, 33076 Bordeaux (France); Hélénon, O. [Department of Radiology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France)

    2015-03-15

    Highlights: •Diagnosis of AMLs with minimal fat (mfAMLs) is still challenging with MRI. •Drop of signal on opposed-phase MR imaging is not specific of mfAMLs. •Double-echo gradient-echo sequences cannot accurately differentiate renal mfAMLs from other renal tumors. -- Abstract: Objectives: The purpose of this retrospective study was to evaluate the diagnostic performance of double-echo gradient chemical shift (GRE) magnetic resonance (MR) imaging for the differentiation of angiomyolipomas with minimal fat (mfAML) from other homogeneous solid renal tumors. Methods: Between 2005 and 2010 in two institutions, all histologically proven homogenous solid renal tumors imaged with computed tomography and MR imaging, including GRE sequences, have been retrospectively selected. A total of 118 patients (mean age: 61 years; range: 20–87) with 119 tumors were included. Two readers measured independently the signal intensity (SI) on GRE images and calculated SI index (SII) and tumor-to-spleen ratio (TSR) on in-phase and opposed-phase images. Intra- and interreader agreement was obtained. Cut-off values were derived from the receiver operating characteristic (ROC) curve analysis. Results: Twelve mfAMLs in 11 patients were identified (mean size: 2.8 cm; range: 1.2–3.5), and 107 non-AML tumors (3.2 cm; 1–7.8) in 107 patients. The intraobserver reproducibility of SII and TSR was excellent with an intraclass correlation coefficient equal to 0.99 [0.98–0.99]. The coefficient of correlation between the readers was 0.99. The mean values of TSR for mfAMLs and non-mfAMLs were −7.0 ± 22.8 versus −8.2 ± 21.2 for reader 1 and −6.7 ± 22.8 versus −8.4 ± 20.9 for reader 2 respectively. No significant difference was noticed between the two groups for SII (p = 0.98) and TSR (p = 0.86). Only 1 out of 12 mfAMLs and 11 of 107 non-AML tumors presented with a TSR inferior to −30% (p = 0.83). Conclusion: In a routine practice, GRE sequences cannot be a confident tool to

  17. Precise Measurement of Magnetic Field Gradients from Free Spin Precession Signals of $^{3}$He and $^{129}$Xe Magnetometers

    CERN Document Server

    Allmendinger, F; Doll, M; Grasdijk, O; Heil, W; Jungmann, K; Karpuk, S; Krause, H -J; Offenhäusser, A; Repetto, M; Schmidt, U; Sobolev, Yu; Tullney, K; Willmann, L; Zimmer, S

    2016-01-01

    We report on precise measurements of magnetic field gradients extracted from transverse relaxation rates of precessing spin samples. The experimental approach is based on the free precession of gaseous, nuclear spin polarized $^3$He and $^{129}$Xe atoms in a spherical cell inside a magnetic guiding field of about 400 nT using LT$_C$ SQUIDs as low-noise magnetic flux detectors. The transverse relaxation rates of both spin species are simultaneously monitored as magnetic field gradients are varied. For transverse relaxation times reaching 100 h, the residual longitudinal field gradient across the spin sample could be deduced to be$|\\vec{\

  18. Spatial Distribution of Oxygen Chemical Potential under Potential Gradients and Theoretical Maximum Power Density with 8YSZ Electrolyte

    Science.gov (United States)

    Lim, Dae-Kwang; Im, Ha-Ni; Song, Sun-Ju

    2016-01-01

    The maximum power density of SOFC with 8YSZ electrolyte as the function of thickness was calculated by integrating partial conductivities of charge carriers under various DC bias conditions at a fixed oxygen chemical potential gradient at both sides of the electrolyte. The partial conductivities were successfully taken using the Hebb-Wagner polarization method as a function of temperature and oxygen partial pressure, and the spatial distribution of oxygen partial pressure across the electrolyte was calculated based on Choudhury and Patterson’s model by considering zero electrode polarization. At positive voltage conditions corresponding to SOFC and SOEC, the high conductivity region was expanded, but at negative cell voltage condition, the low conductivity region near n-type to p-type transition was expanded. In addition, the maximum power density calculated from the current-voltage characteristic showed approximately 5.76 W/cm2 at 700 oC with 10 μm thick-8YSZ, while the oxygen partial pressure of the cathode and anode sides maintained ≈0.21 and 10-22 atm.

  19. Flat lizard female mimics use sexual deception in visual but not chemical signals.

    Science.gov (United States)

    Whiting, Martin J; Webb, Jonathan K; Keogh, J Scott

    2009-05-01

    Understanding what constrains signalling and maintains signal honesty is a central theme in animal communication. Clear cases of dishonest signalling, and the conditions under which they are used, represent an important avenue for improved understanding of animal communication systems. Female mimicry, when certain males take on the appearance of females, is most commonly a male alternative reproductive tactic that is condition-dependent. A number of adaptive explanations for female mimicry have been proposed including avoiding the costs of aggression, gaining an advantage in combat, sneaking copulations with females on the territories of other males, gaining physiological benefits and minimizing the risk of predation. Previous studies of female mimicry have focused on a single mode of communication, although most animals communicate using multiple signals. Male Augrabies flat lizards adopt alternative reproductive tactics in which some males (she-males) mimic the visual appearance of females. We experimentally tested in a wild population whether she-males are able to mimic females using both visual and chemical signals. We tested chemical recognition in the field by removing scent and relabelling females and she-males with either male or female scent. At a distance, typical males (he-males) could not distinguish she-males from females using visual signals, but during close encounters, he-males correctly determined the gender of she-males using chemical signals. She-males are therefore able to deceive he-males using visual but not chemical signals. To effectively deceive he-males, she-males avoid close contact with he-males during which chemical cues would reveal their deceit. This strategy is probably adaptive, because he-males are aggressive and territorial; by mimicking females, she-males are able to move about freely and gain access to females on the territories of resident males. PMID:19324828

  20. Amplifying the SERS signal of DNA bases via the chemical resonance

    Science.gov (United States)

    Freeman, Lindsay M.; Pang, Lin; Fainman, Yeshaiahu

    2015-03-01

    Label-free detection methods of DNA bases using surface-enhanced Raman spectroscopy (SERS) have yet to be successfully utilized due to inconsistent signal readouts. We have identified the primary reason for the discrepancies in the SERS signals of nucleic acids as being caused by the charge-transfer chemical resonance of the base silver system which is dependent on excitation wavelength. Time-dependent density functional theory (TD-DFT) methods to calculate the electronic transitions and resonance Raman spectra of base silver complexes are performed, and the optimal excitation wavelength for the charge-transfer electronic transition is found for each base silver complex. The enhancement caused by the chemical resonance is then experimentally measured for adenine, cytosine, guanine and thymine at multiple excitation wavelengths. The dependence of the Raman intensity on excitation wavelength shows good agreement with the TD-DFT calculations. In order to fully achieve the maximum Raman intensity, both the electromagnetic and chemical resonance must be enhanced by the appropriate wavelength selection. Based on the optimal chemical resonance Raman wavelength, we design a SERS substrate which has an electromagnetic maximum wavelength that matches the chemical resonance wavelength. By aligning both resonances, the highest Raman intensity can be found for each base silver system. We have proven that the variance in DNA bases' Raman intensities are caused by chemical enhancement. By incorporating the chemical resonance and optimizing both the chemical and electromagnetic resonance, we believe a label-free DNA SERS based detection method can be realized.

  1. Experimental study of the hydrothermal alteration of a chemical analogue of the French nuclear glass in a thermal gradient: characterization of newly formed phases and of matter transfers

    International Nuclear Information System (INIS)

    As the most dangerous radioactive wastes are to be stored in deep geological layers after having been packaged in barrels made of borosilicate glasses, this research report addresses the study of the alteration of such glasses through the study of a chemical analogue. In order to experimentally model phenomena involved within a storage, the studied glass has been submitted to different thermal gradients between 320 and 150 C and during 3 to 5 months. These gradients comply with those met about the parcels, and allows the spatial evolution of the waste parcel at a given moment, as well as the evolution in time (progressive cooling of wastes) to be simultaneously simulated. The different phases formed within the gradient have been studied and characterized by scanning electronic microscopy, semi-quantitative microanalysis, and X-ray micro-diffraction

  2. Chemical vs. Physical Contributions to Grainsize Distributions in Hillslope Soils along a Denudation Gradient in the Sierra Nevada, California

    Science.gov (United States)

    Weinman, B. A.; Yoo, K.; Mudd, S. M.; Attal, M.; Hurst, M. D.; Maher, K.; Kouba, C. M.; Bern, C.; Singhvi, A. K.

    2011-12-01

    An important part of understanding how soil forms consists of understanding grainsize evolution. How much of a soil's grainsize distribution comes from physical (i.e., fracturing or treethrow) and/or chemical (i.e., secondary mineral production) weathering remains poorly understood. In order to evaluate the effect and magnitude of physical and chemical weathering on soil-grainsize, we used a geochemical mass balance and grainsize approach on soils from the Feather River basin in the Sierra Nevada. Three hillslopes in the basin were chosen to reflect 3 different degrees of channel erosion at their bases-a hillslope with active channel incision (60% slope, below the knickpoint), a hillslope reflecting the transition between the relict and modern-day incising areas (50% slope, at the knickpoint), and a 30% hillslope in the relict landscape (an area that has not yet "felt" the 5Mya increase in erosion). Our results show that soil particle sizes increase with both hillslope slope gradient and soil-depth, following a soil grainsize increase (μm/cm) = 0.036e^{6×Slope} (R^2 = 0.9995). The Zr from the tonalite (100 ppm) up to the saprolite (100-250ppm) and into the soil (soil approx saprolite) along the 3 slopes indicate that the basin's soil geochemistry is set at depths below the soil-saprolite boundary. The mean grainsize of particles at the soil-saprolite boundary increases with slope from 78 to 181 to 275μm. Thus, in terms of elemental compositions, colluvial soils appear virtually identical to the underlying saprolite, and soil grainsize differentiation within the colluvium is mostly a physical process. However, colluvial soils do show significantly finer size distributions in the hillslopes with lower erosion rates (which also have saprolites with a greater degree of weathering loss). Therefore, the degree of chemical denudation in the saprolite appears to dictate the susceptibility of the materials to physical breakdown to finer particle sizes in the overlying

  3. Roles of chemical signals in regulation of the adaptive responses to iron deficiency.

    Science.gov (United States)

    Liu, Xing Xing; He, Xiao Lin; Jin, Chong Wei

    2016-05-01

    Iron is an essential micronutrient for plants but is not readily accessible in most calcareous soils. Although the adaptive responses of plants to iron deficiency have been well documented, the signals involved in the regulatory cascade leading to their activation are not well understood to date. Recent studies revealed that chemical compounds, including sucrose, auxin, ethylene and nitric oxide, positively regulated the Fe-deficiency-induced Fe uptake processes in a cooperative manner. Nevertheless, cytokinins, jasmonate and abscisic acid were shown to act as negative signals in transmitting the iron deficiency information. The present mini review is to briefly address the roles of chemical signals in regulation of the adaptive responses to iron deficiency based on the literatures published in recent years. PMID:27110729

  4. Diversity of Ammonia-Oxidizing Archaea and Bacteria Across Physical-Chemical Gradients in San Francisco Bay Estuary Sediments

    Science.gov (United States)

    Mosier, A. C.; Francis, C. A.

    2006-12-01

    A combination of recent metagenomic analyses and the cultivation of a novel, ammonia-oxidizing, marine crenarchaeota revealed the first evidence for nitrification within the Archaeal domain. Further genetic and metagenomic studies demonstrated the presence of ammonia-oxidizing crenarchaea in diverse marine and terrestrial environments. These discoveries challenge the currently accepted view of the global nitrogen cycle and validate the need for further research on microbial diversity and function. In particular, it is imperative to reexamine the microbial communities involved in ammonia oxidation in marine and estuarine sediments, where this process plays a pivotal role in the cycling and removal of nitrogen. Using phylogenetic analyses of ammonia monooxygenase subunit A (amoA) gene sequences, we examined the distribution and diversity of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in San Francisco Bay, the largest estuary on the West coast of the United States. The highly impacted bay, encompassing nearly 178,000 km2, effectively connects two estuaries with varying physical-chemical characteristics to the Pacific Ocean. We recovered archaeal and bacterial amoA genes from 11 sites distributed throughout the bay, spanning the northern and southern estuaries and the central region where they connect to the ocean. Richness estimates varied considerably across all sites examined, with archaeal amoA estimates being generally higher than bacterial amoA. Several of the bacterial amoA libraries were represented by fewer than 3 genotypes. Archaeal amoA sequences were phylogenetically diverse and grouped within previously described sediment and soil/sediment clusters. Several sequences were closely related to the only cultivated AOA, Nitrosopumilus maritimus. Both the archaeal and bacterial amoA sequences showed significant regional specificity. Distinct populations exist in the northern and southern estuaries and sequences from the northernmost and southernmost sites

  5. Correlation analyses between volatiles and glucosinolates show no evidence for chemical defense signaling in Brassica rapa

    Directory of Open Access Journals (Sweden)

    Florian Paul Schiestl

    2014-04-01

    Full Text Available Positive correlations between volatile organic compounds (VOCs and defense chemicals indicate signaling of defense status. Such aposematic signaling has been hypothesized to be widespread in plants, however, it has up to now only been shown for visual signals. Correlations between identical compounds in different plant tissues, on the other hand, can be informative about the (co-regulation of their biosynthesis or emission. Here I use Brassica rapa to investigate 1 correlations between identical metabolites (volatiles, glucosinolates in leaf and flower tissue, and 2 correlations between volatiles and glucosinolates in the same plant organs (flowers and leaves. Whereas the amounts of many glucosinolates were positively correlated in leaves and flower tissue, identical leaf and floral VOCs showed no such correlations, indicating independent regulation of emission. None of the leaf or flower volatiles showed positive correlations with the two major glucosinolates (gluconapin, glucobrassicanapin or the sum of all glucosinolates in either leaves or flowers. Some VOCs, however, showed positive correlations with minor glucosinolates which, however, represented less than one percent of the total amounts of glucosinolates. Some leaf monoterpenes showed negative associations with gluconapin. The lack of consistent positive correlations between VOCs and major defense compounds suggests that plants do not chemically signal their defense status. This could be adaptive as it may avoid eavesdropping by specialist herbivores to locate their host plants. Negative correlations likely indicate chemical trade-offs in the synthesis of secondary metabolites.

  6. Modeling of the chemical interactions between concrete and Febex bentonite subjected to hydration and a thermal gradient

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Concrete can be used in a radioactive waste repository to support either the bentonite barriers in disposal tunnels or the access galleries. Concrete degradation generates an alkaline plume that can affect the swelling and transport properties of the bentonite barriers and the clayey host rock in contact with concrete. Various studies have been performed in order to study the influence of alkaline solutions on the FEBEX bentonite. For instance, Cuevas et al. carried out a set of batch and column experiments on the system alkaline-water/mortar/bentonite in the temperature range 25-120 deg. C. The main phases identified during these experiments were tobermorite or C-S-H gels, Mg-clays and zeolites (analcime, phillipsite). Precipitation of a smectitic tri-octahedral phase was confirmed, as well. In the framework of the NF-Pro Project, a series of complementary tests were designed to study the interactions between concrete (CEM-I cement) and the FEBEX bentonite under more relevant repository conditions. The tests were carried out in hermetic cylindrical cells in which a concrete slab was placed on the top of a compacted bentonite block. Hydration was performed with a synthetic solution by applying a hydraulic pressure of 12 bars at the concrete slab. The solution mimicked a Na-Cl-SO4 pore water found in Spanish argillaceous formations. A constant thermal gradient was also established in the cells, ranging from 25 deg. C on the top of the concrete slab to 100 deg. C at the bottom of the bentonite block. Three of the cells were dismantled after 6, 12 and 18 months of operation. The chemical and mineralogical evolutions of the concrete slab and the bentonite block were modeled with the reactive transport code HYTEC, taking into account hydration and a temperature gradient. The thermal and suction properties of the materials were correctly considered in the calculations but not the important process of vapor transport (i

  7. The population of planetary nebulae and H II regions in M 81. A study of radial metallicity gradients and chemical evolution

    Science.gov (United States)

    Stanghellini, L.; Magrini, L.; Villaver, E.; Galli, D.

    2010-10-01

    Context. M 81 is an ideal laboratory to investigate the galactic chemical and dynamical evolution through the study of its young and old stellar populations. Aims: We analyze the chemical abundances of planetary nebulae and H ii regions in the M 81 disk for insight on galactic evolution, and compare it with that of other galaxies, including the Milky Way. Methods: We acquired Hectospec/MMT spectra of 39 PNe and 20 H ii regions, with 33 spectra viable for temperature and abundance analysis. Our PN observations represent the first PN spectra in M 81 ever published, while several H ii region spectra have been published before, although without a direct electron temperature determination. We determine elemental abundances of helium, nitrogen, oxygen, neon, sulfur, and argon in PNe and H ii regions, and determine their averages and radial gradients. Results: The average O/H ratio of PNe compared to that of the H ii regions indicates a general oxygen enrichment in M 81 in the last ~10 Gyr. The PN metallicity gradient in the disk of M 81 is Δlog(O/H)/ΔRG = -0.055 ± 0.02 dex/kpc. Neon and sulfur in PNe have a radial distribution similar to that of oxygen, with similar gradient slopes. If we combine our H ii sample with the one in the literature we find a possible mild evolution of the gradient slope, with results consistent with gradient steepening with time. Additional spectroscopy is needed to confirm this trend. There are no type I PNe in our M 81 sample, consistently with the observation of only the brightest bins of the PNLF, the galaxy metallicity, and the evolution of post-AGB shells. Conclusions: Both the young and the old populations of M 81 disclose shallow but detectable negative radial metallicity gradient, which could be slightly steeper for the young population, thus not excluding a mild gradients steepening with the time since galaxy formation. During its evolution M 81 has been producing oxygen; its total oxygen enrichment exceeds that of other nearby

  8. Free-field calibration of a pressure gradient receiver in a reflecting water tank using a linear frequency-modulated signal

    Science.gov (United States)

    Isaev, A. E.; Matveev, A. N.; Nekrich, G. S.; Polikarpov, A. M.

    2013-11-01

    This work continues a study of the method for constructing the frequency dependence for a projector-receiver pair in a free field by complex moving weighted averaging of the frequency dependence for a pair measured in the field of a reflecting water tank. The method is applied to the free-field calibration of a pressure gradient receiver using a reference hydrophone when radiating a complex linear frequency-modulated (LFM) signal. To improve the estimates of this method, we edited the initial frequency dependences using functions in the form of the product of the complex LFM projector current multiplied by the powerlaw function of the LFM signal frequency. We consider ways to use a priori information both to improve the results obtained by complex moving weighted averaging and to estimate the distortions introduced by this method are considered.

  9. Optimal control of the signal-to-noise ratio per unit time of a spin 1/2 particle: The crusher gradient and the radiation damping cases

    International Nuclear Information System (INIS)

    We show to which extent the signal to noise ratio per unit time of a spin 1/2 particle can be maximized. We consider a cyclic repetition of experiments made of a measurement followed by a radio-frequency magnetic field excitation of the system, in the case of unbounded amplitude. In the periodic regime, the objective of the control problem is to design the initial state of the system and the pulse sequence which leads to the best signal to noise performance. We focus on two specific issues relevant in nuclear magnetic resonance, the crusher gradient and the radiation damping cases. Optimal control techniques are used to solve this non-standard control problem. We discuss the optimality of the Ernst angle solution, which is commonly applied in spectroscopic and medical imaging applications. In the radiation damping situation, we show that in some cases, the optimal solution differs from the Ernst one

  10. Chemical origin of the native ESR signals in thermally treated enamel and dentin

    International Nuclear Information System (INIS)

    Heating, crushing and exposure of dental enamel to sunlight and UV radiation can introduce paramagnetic signals similar to those following exposure to ionizing radiation. The objective of this work is to use infrared and electron spin resonance (ESR) spectra to study thermally treated enamel and dentin, and identify the chemical radical or mechanisms that produce these ambiguous ESR signals. Non-irradiated bovine teeth were used. ESR spectroscopy was performed in the X band and the infrared spectroscopy was performed on a FTIR spectrometer operating between 4000 cm-1 and 400 cm-1. The results show ESR signals in dentin heated at temperatures between 100 deg. C and 1000 deg. C and in enamel heated at temperatures ranging from 250 deg. C to 1000 deg. C. The ESR signal formed after heat treatment below 400 deg. C could be assigned to degradation products of the organic material, while the ESR signals that predominate in tissues heated between 500 deg. C and 900 deg. C show a maximum amplitude at 750 deg. C and could be assigned to the cyanate ion (NCO-)

  11. Response to the Dorsal Anterior Gradient of EGFR Signaling in Drosophila Oogenesis Is Prepatterned by Earlier Posterior EGFR Activation

    Directory of Open Access Journals (Sweden)

    Mariana Fregoso Lomas

    2013-08-01

    Full Text Available Spatially restricted epidermal growth factor receptor (EGFR activity plays a central role in patterning the follicular epithelium of the Drosophila ovary. In midoogenesis, localized EGFR activation is achieved by the graded dorsal anterior localization of its ligand, Gurken. Graded EGFR activity determines multiple dorsal anterior fates along the dorsal-ventral axis but cannot explain the sharp posterior limit of this domain. Here, we show that posterior follicle cells express the T-box transcription factors Midline and H15, which render cells unable to adopt a dorsal anterior fate in response to EGFR activation. The posterior expression of Midline and H15 is itself induced in early oogenesis by posteriorly localized EGFR signaling, defining a feedback loop in which early induction of Mid and H15 confers a molecular memory that fundamentally alters the outcome of later EGFR signaling. Spatial regulation of the EGFR pathway thus occurs both through localization of the ligand and through localized regulation of the cellular response.

  12. Chemical evolution of the inner 2 degrees of the Milky Way bulge: [alpha/Fe] trends and metallicity gradients

    CERN Document Server

    Ryde, N; Grieco, V; Matteucci, F; Rich, R M; Uttenthaler, S

    2015-01-01

    The structure, formation, and evolution of the Milky Way bulge is a matter of debate. Important diagnostics for discriminating between bulge models include alpha-abundance trends with metallicity, and spatial abundance and metallicity gradients. Due to the severe optical extinction in the inner Bulge region, only a few detailed investigations have been performed of this region. Here we aim at investigating the inner 2 degrees by observing the [alpha/Fe] element trends versus metallicity, and by trying to derive the metallicity gradient. [alpha/Fe] and metallicities have been determined by spectral synthesis of 2 micron spectra observed with VLT/CRIRES of 28 M-giants, lying along the Southern minor axis at (l,b)=(0,0), (0,-1), and (0,-2). VLT/ISAAC spectra are used to determine the effective temperature of the stars. We present the first connection between the Galactic Center and the Bulge using similar stars, high spectral resolution, and analysis techniques. The [alpha/Fe] trends in all our 3 fields show a l...

  13. Chemical Signals of Synthetic Disaccharide Derivatives Dominate Rhamnolipids at Controlling Multiple Bacterial Activities.

    Science.gov (United States)

    Singh, Nischal; Shetye, Gauri S; Zheng, Hewen; Sun, Jiayue; Luk, Yan-Yeung

    2016-01-01

    Microbes secrete molecules that modify their environment. Here, we demonstrate a class of synthetic disaccharide derivatives (DSDs) that mimics and dominates the activity of naturally secreted rhamnolipids by Pseudomonas aeruginosa. The DSDs exhibit the dual function of activating and inhibiting the swarming motility through a concentration-dependent activity reversal that is characteristic of signaling molecules. Whereas DSDs tethered with a saturated farnesyl group exhibit inhibition of both biofilm formation and swarming motility, with higher activities than rhamnolipids, a saturated farnesyl tethered with a sulfonate group only inhibits swarming motility but promote biofilm formation. These results identified important structural elements for controlling swarming motility, biofilm formation, and bacterial adhesion and suggest an effective chemical approach to control intertwined signaling processes that are important for biofilm formation and motilities. PMID:26511780

  14. Environmental signaling: from environmental estrogens to endocrine-disrupting chemicals and beyond.

    Science.gov (United States)

    McLachlan, J A

    2016-07-01

    The landmark report (Herbst et al. 1971) linking prenatal treatment with a synthetic estrogen, diethylstilbestrol (DES), to cancer at puberty in women whose mothers took the drug while pregnant ushered in an era of research on delayed effects of such exposures on functional outcomes in offspring. An animal model developed in our laboratory at the National Institute of Environmental Health Sciences confirmed that DES was the carcinogen and exposure to DES caused, as well, functional alterations in the reproductive, endocrine, and immune systems of male and female mice treated in utero. DES was also being used in agriculture and we discovered, at the first meeting on Estrogens in the Environment in 1979 (Estrogens in the Environment, 1980), that many environmental contaminants were also estrogenic. Many laboratories sought to discern the basis for estrogenicity in environmental chemicals and to discover other hormonally active xenobiotics. Our laboratory elucidated how DES and other estrogenic compounds worked by altering differentiation through epigenetic gene imprinting, helping explain the transgenerational effects found in mice and humans. At the Wingspread Conference on the Human-Wildlife Connection in 1991 (Advances in Modern Environmental Toxicology, 1992), we learned that environmental disruption of the endocrine system occurred in many species and phyla, and the term endocrine disruption was introduced. Further findings of transgenerational effects of environmental agents that mimicked or blocked various reproductive hormones and the ubiquity of environmental signals, such as bisphenol A increased concern for human and ecological health. Scientists began to look at other endocrine system aspects, such as cardiovascular and immune function, and other nuclear receptors, with important observations regarding obesity and metabolism. Laboratories, such as ours, are now using stem cells to try to understand the mechanisms by which various environmental signals

  15. Database proton NMR chemical shifts for RNA signal assignment and validation

    International Nuclear Information System (INIS)

    The Biological Magnetic Resonance Data Bank contains NMR chemical shift depositions for 132 RNAs and RNA-containing complexes. We have analyzed the 1H NMR chemical shifts reported for non-exchangeable protons of residues that reside within A-form helical regions of these RNAs. The analysis focused on the central base pair within a stretch of three adjacent base pairs (BP triplets), and included both Watson–Crick (WC; G:C, A:U) and G:U wobble pairs. Chemical shift values were included for all 43 possible WC-BP triplets, as well as 137 additional triplets that contain one or more G:U wobbles. Sequence-dependent chemical shift correlations were identified, including correlations involving terminating base pairs within the triplets and canonical and non-canonical structures adjacent to the BP triplets (i.e. bulges, loops, WC and non-WC BPs), despite the fact that the NMR data were obtained under different conditions of pH, buffer, ionic strength, and temperature. A computer program (RNAShifts) was developed that enables convenient comparison of RNA 1H NMR assignments with database predictions, which should facilitate future signal assignment/validation efforts and enable rapid identification of non-canonical RNA structures and RNA-ligand/protein interaction sites.

  16. Chemical signals in the stingless bee, Frieseomelitta varia, indicate caste, gender, age, and reproductive status.

    Science.gov (United States)

    Nunes, Túlio M; Turatti, Izabel C C; Lopes, Norberto P; Zucchi, Ronaldo

    2009-10-01

    Chemical compounds on the cuticle are a rich source of information used during interactions among social insects. Despite the multitude of studies on these substances and their function in ants, wasps, and honeybees, little is known about this subject in stingless bees (Hymenoptera: Apidae, Meliponini). We studied the chemical composition of the cuticle of the stingless bee, Frieseomelitta varia, by gas chromatography-mass spectrometry (GC-MS), to investigate potential chemical variation among castes, gender, age, and reproductive status. We found differences in the cuticular hydrocarbon composition among workers, males, and queens, recording both qualitative and quantitative differences among individuals of different ages and gender. The cuticle of physogastric queens presented a chemical profile that was distinct from all other groups in the analysis, with high relative abundances of alkenes and alkadienes with 27, 29, and 31 carbon atoms. We discuss the possibility that these compounds signal a queen's presence to the colony, thereby initiating all vital worker-queen interactions. PMID:19813058

  17. Rethinking data collection and signal processing. 1. Real-time oversampling filter for chemical measurements.

    Science.gov (United States)

    Laude, Nicholas D; Atcherley, Christopher W; Heien, Michael L

    2012-10-01

    Minimizing noise in chemical measurements is critical to achieve low limits of detection and accurate measurements. We describe a real-time oversampling filter that offers a method to reduce stochastic noise in a time-dependent chemical measurement. The power of this technique is demonstrated in its application to the separation of dopamine and serotonin by micellar electrokinetic chromatography with amperometric detection. Signal-to-noise ratios were increased by almost an order of magnitude, allowing for limits of detection of 100 and 120 amol, respectively. Real-time oversampling filters can be implemented using simple software algorithms and require no change to existing experimental apparatus. The application is not limited to analytical separations, and this technique can be used to improve the signal-to-noise ratio in any experiment where the necessary sampling rate is less than the maximum sampling rate of the analog-to-digital converter. Theory, implementation, and the performance of this filter are described. We propose that this technique should be the default mode of operation for an analog-to-digital converter. PMID:22978644

  18. Sources and Radiation Patterns of Volcano-Acoustic Signals Investigated with Field-Scale Chemical Explosions

    Science.gov (United States)

    Bowman, D. C.; Lees, J. M.; Taddeucci, J.; Graettinger, A. H.; Sonder, I.; Valentine, G.

    2014-12-01

    We investigate the processes that give rise to complex acoustic signals during volcanic blasts by monitoring buried chemical explosions with infrasound and audio range microphones, strong motion sensors, and high speed imagery. Acoustic waveforms vary with scaled depth of burial (SDOB, units in meters per cube root of joules), ranging from high amplitude, impulsive, gas expansion dominated signals at low SDOB to low amplitude, longer duration, ground motion dominated signals at high SDOB. Typically, the sudden upward acceleration of the substrate above the blast produces the first acoustic arrival, followed by a second pulse due to the eruption of pressurized gas at the surface. Occasionally, a third overpressure occurs when displaced material decelerates upon impact with the ground. The transition between ground motion dominated and gas release dominated acoustics ranges between 0.0038-0.0018 SDOB, respectively. For example, one explosion registering an SDOB=0.0031 produced two overpressure pulses of approximately equal amplitude, one due to ground motion, the other to gas release. Recorded volcano infrasound has also identified distinct ground motion and gas release components during explosions at Sakurajima, Santiaguito, and Karymsky volcanoes. Our results indicate that infrasound records may provide a proxy for the depth and energy of these explosions. Furthermore, while magma fragmentation models indicate the possibility of several explosions during a single vulcanian eruption (Alidibirov, Bull Volc., 1994), our results suggest that a single explosion can also produce complex acoustic signals. Thus acoustic records alone cannot be used to distinguish between single explosions and multiple closely-spaced blasts at volcanoes. Results from a series of lateral blasts during the 2014 field experiment further indicates whether vent geometry can produce directional acoustic radiation patterns like those observed at Tungarahua volcano (Kim et al., GJI, 2012). Beside

  19. Gradient-echo in-phase and opposed-phase chemical shift imaging: Role in evaluating bone marrow

    International Nuclear Information System (INIS)

    Chemical shift imaging (CSI) provides valuable information for assessing the bone marrow, while adding little to total examination time. In this article, we review the uses of CSI for evaluating bone marrow abnormalities. CSI can be used for differentiating marrow-replacing lesions from a range of non-marrow-replacing processes, although the sequence is associated with technical limitations and pitfalls. Particularly at 3 T, susceptibility artefacts are prevalent, and optimal technical parameters must be implemented with appropriate choices for echo times

  20. Laser textured surface gradients

    Science.gov (United States)

    Ta, Van Duong; Dunn, Andrew; Wasley, Thomas J.; Li, Ji; Kay, Robert W.; Stringer, Jonathan; Smith, Patrick J.; Esenturk, Emre; Connaughton, Colm; Shephard, Jonathan D.

    2016-05-01

    This work demonstrates a novel technique for fabricating surfaces with roughness and wettability gradients and their subsequent applications for chemical sensors. Surface roughness gradients on brass sheets are obtained directly by nanosecond laser texturing. When these structured surfaces are exposed to air, their wettability decreases with time (up to 20 days) achieving both spatial and temporal wettability gradients. The surfaces are responsive to organic solvents. Contact angles of a series of dilute isopropanol solutions decay exponentially with concentration. In particular, a fall of 132° in contact angle is observed on a surface gradient, one order of magnitude higher than the 14° observed for the unprocessed surface, when the isopropanol concentration increased from 0 to 15.6 wt%. As the wettability changes gradually over the surface, contact angle also changes correspondingly. This effect offers multi-sensitivity at different zones on the surface and is useful for accurate measurement of chemical concentration.

  1. Vertical physico-chemical gradients with distinct microbial communities in the hypersaline and heliothermal Lake Ursu (Sovata, Romania).

    Science.gov (United States)

    Máthé, István; Borsodi, Andrea K; Tóth, Erika M; Felföldi, Tamás; Jurecska, Laura; Krett, Gergely; Kelemen, Zsolt; Elekes, Erzsébet; Barkács, Katalin; Márialigeti, Károly

    2014-05-01

    The effect of vertical physico-chemical stratification on the planktonic microbial community composition of the deep, hypersaline and heliothermal Lake Ursu (Sovata, Romania) was examined in this study. On site and laboratory measurements were performed to determine the physical and chemical variables of the lake water, and culture-based and cultivation-independent techniques were applied to identify the members of microbial communities. The surface of the lake was characterized by a low salinity water layer while the deepest region was extremely saline (up to 300 g/L salinity). Many parameters (e.g. photosynthetically active radiation, dissolved oxygen concentration, pH, redox potential) changed dramatically from 2 to 4 m below the water surface in conjunction with the increasing salinity values. The water temperature reached a maximum at this depth. At around 3 m depth, there was a water layer with high (bacterio) chlorophyll content dominated by Prosthecochloris vibrioformis, a phototrophic green sulfur bacterium. Characteristic microbial communities with various prokaryotic taxa were identified along the different environmental parameters present in the different water layers. Some of these bacteria were known to be heterotrophic and therefore may be involved in the decomposition of lake organic material (e.g. Halomonas, Idiomarina and Pseudoalteromonas) while others in the transformation of sulfur compounds (e.g. Prosthecochloris). Eukaryotic microorganisms identified by molecular methods in the lake water belonged to genera of green algae (Mantionella and Picochlorum), and were restricted mainly to the upper layers. PMID:24531691

  2. Age and isolation influence steroids release and chemical signaling in male mice.

    Science.gov (United States)

    Mucignat-Caretta, Carla; Cavaggioni, Andrea; Redaelli, Marco; Da Dalt, Laura; Zagotto, Giuseppe; Gabai, Gianfranco

    2014-05-01

    Social interactions in mice involve olfactory signals, which convey information about the emitter. In turn, the mouse social and physiological status may modify the release of chemical cues. In this study, the influences of age and social isolation on the endocrine response and the release of chemical signals were investigated in male CD1 mice, allocated into four groups: Young Isolated (from weaning till 60days; N=6), Adult Isolated (till 180days; N=6), Young Grouped (6 mice/cage; till 60days; N=18), Adult Grouped (6 mice/cage; till 180days; N=18). Mice were transferred in a clean cage to observe the micturition pattern and then sacrificed. Body and organs weights, serum testosterone, dehydroepiandrosterone, corticosterone and the ratio Major Urinary Protein/creatinine were measured. Urinary volatile molecules potentially involved in pheromonal communication were identified. Androgen secretion was greater in isolated mice (P<0.05), suggesting a greater reactivity of the Hypothalamic-Pituitary-Gonadal axis. Grouped mice presented a higher degree of adrenal activity, and young mice showed a higher serum corticosterone (P<0.05) suggesting a greater stimulation of the Hypothalamic-Pituitary-Adrenal axis. The micturition pattern typical of dominant male, consisting in voiding numerous droplets, was observed in Young Isolated mice only, which showed a higher protein/creatinine ratio (P<0.05). Urinary 2-s-butyl-thiazoline was higher in both Young and Adult Isolated mice (P<0.005). Young Isolated mice showed the most prominent difference in both micturition pattern and potentially active substance emission, while long term isolation resulted in a less extreme phenotype; therefore social isolation had a higher impact on young mice hormone and pheromone release. PMID:24525008

  3. Artificial intelligence/fuzzy logic method for analysis of combined signals from heavy metal chemical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Turek, M. [Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Campus Juelich, Juelich (Germany); Institute of Bio- and Nanosystems (IBN), Research Centre Juelich GmbH, Juelich (Germany); Heiden, W.; Riesen, A. [Bonn-Rhein-Sieg University of Applied Sciences, Sankt Augustin (Germany); Chhabda, T.A. [Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Campus Juelich, Juelich (Germany); Schubert, J.; Zander, W. [Institute of Bio- and Nanosystems (IBN), Research Centre Juelich GmbH, Juelich (Germany); Krueger, P. [Institute of Biochemistry and Molecular Biology, RWTH Aachen, Aachen (Germany); Keusgen, M. [Institute for Pharmaceutical Chemistry, Philipps-University Marburg, Marburg (Germany); Schoening, M.J. [Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Campus Juelich, Juelich (Germany); Institute of Bio- and Nanosystems (IBN), Research Centre Juelich GmbH, Juelich (Germany)], E-mail: m.j.schoening@fz-juelich.de

    2009-10-30

    The cross-sensitivity of chemical sensors for several metal ions resembles in a way the overlapping sensitivity of some biological sensors, like the optical colour receptors of human retinal cone cells. While it is difficult to assign crisp classification values to measurands based on complex overlapping sensory signals, fuzzy logic offers a possibility to mathematically model such systems. Current work goes into the direction of mixed heavy metal solutions and the combination of fuzzy logic with heavy metal-sensitive, silicon-based chemical sensors for training scenarios of arbitrary sensor/probe combinations in terms of an electronic tongue. Heavy metals play an important role in environmental analysis. As trace elements as well as water impurities released from industrial processes they occur in the environment. In this work, the development of a new fuzzy logic method based on potentiometric measurements performed with three different miniaturised chalcogenide glass sensors in different heavy metal solutions will be presented. The critical validation of the developed fuzzy logic program will be demonstrated by means of measurements in unknown single- and multi-component heavy metal solutions. Limitations of this program and a comparison between calculated and expected values in terms of analyte composition and heavy metal ion concentration will be shown and discussed.

  4. Artificial intelligence/fuzzy logic method for analysis of combined signals from heavy metal chemical sensors

    International Nuclear Information System (INIS)

    The cross-sensitivity of chemical sensors for several metal ions resembles in a way the overlapping sensitivity of some biological sensors, like the optical colour receptors of human retinal cone cells. While it is difficult to assign crisp classification values to measurands based on complex overlapping sensory signals, fuzzy logic offers a possibility to mathematically model such systems. Current work goes into the direction of mixed heavy metal solutions and the combination of fuzzy logic with heavy metal-sensitive, silicon-based chemical sensors for training scenarios of arbitrary sensor/probe combinations in terms of an electronic tongue. Heavy metals play an important role in environmental analysis. As trace elements as well as water impurities released from industrial processes they occur in the environment. In this work, the development of a new fuzzy logic method based on potentiometric measurements performed with three different miniaturised chalcogenide glass sensors in different heavy metal solutions will be presented. The critical validation of the developed fuzzy logic program will be demonstrated by means of measurements in unknown single- and multi-component heavy metal solutions. Limitations of this program and a comparison between calculated and expected values in terms of analyte composition and heavy metal ion concentration will be shown and discussed.

  5. Aerodynamic gradient measurements of the NH3-HNO3-NH4NO3 triad using a wet chemical instrument: an analysis of precision requirements and flux errors

    Directory of Open Access Journals (Sweden)

    F. X. Meixner

    2009-10-01

    Full Text Available The aerodynamic gradient method is widely used for flux measurements of ammonia, nitric acid, particulate ammonium nitrate (the NH3-HNO3-NH4NO3 triad and other water-soluble reactive trace compounds. The surface exchange flux is derived from a measured concentration difference and micrometeorological quantities (turbulent exchange coefficient. The significance of the measured concentration difference is crucial for the significant determination of surface exchange fluxes. Additionally, measurements of surface exchange fluxes of ammonia, nitric acid and ammonium nitrate are often strongly affected by phase changes between gaseous and particulate compounds of the triad, which make measurements of the four individual species (NH3, HNO3, NH4+, NO3– necessary for a correct interpretation of the measured concentration differences. We present here a rigorous analysis of results obtained with a multi-component, wet-chemical instrument, able to simultaneously measure gradients of both gaseous and particulate trace substances. Basis for our analysis are two field experiments, conducted above contrasting ecosystems (grassland, forest. Precision requirements of the instrument as well as errors of concentration differences and micrometeorological exchange parameters have been estimated, which, in turn, allows the establishment of thorough error estimates of the derived fluxes of NH3, HNO3, NH4+, and NO3–. Derived median flux errors for the grassland and forest field experiments were: 39 and 50% (NH3, 31 and 38% (HNO3, 62 and 57% (NH4+, and 47 and 68% (NO3–, respectively. Additionally, we provide the basis for using field data to characterize the instrument performance, as well as subsequent quantification of surface exchange fluxes and underlying mechanistic processes under realistic ambient measurement conditions.

  6. Profiling 976 ToxCast chemicals across 331 enzymatic and receptor signaling assays (Communities of Practice)

    Science.gov (United States)

    Understanding potential health risks is a significant challenge for large numbers of diverse chemicals with poorly characterized exposures and mechanisms of toxicities. The present study analyzes chemical-target activity profiles of 976 chemicals (including failed pharmaceuticals...

  7. The vomeronasal organ is required for the male mouse medial amygdala response to chemical-communication signals, as assessed by immediate early gene expression

    OpenAIRE

    Samuelsen, Chad L.; Meredith, Michael

    2009-01-01

    Many species use chemical signals to convey information relevant to social and reproductive status between members of the same species (conspecific), but some chemical signals may also provide information to another species (heterospecific). Both of these types of complex chemical signals may be detected by the vomeronasal organ, which sends projections to the accessory olfactory bulb and on to the medial amygdala. Previous reports in hamster and mouse suggest that the medial amygdala sorts t...

  8. A hypothetico-deductive approach to assessing the social function of chemical signalling in a non-territorial solitary carnivore.

    Directory of Open Access Journals (Sweden)

    Melanie Clapham

    Full Text Available The function of chemical signalling in non-territorial solitary carnivores is still relatively unclear. Studies on territorial solitary and social carnivores have highlighted odour capability and utility, however the social function of chemical signalling in wild carnivore populations operating dominance hierarchy social systems has received little attention. We monitored scent marking and investigatory behaviour of wild brown bears Ursus arctos, to test multiple hypotheses relating to the social function of chemical signalling. Camera traps were stationed facing bear 'marking trees' to document behaviour by different age sex classes in different seasons. We found evidence to support the hypothesis that adult males utilise chemical signalling to communicate dominance to other males throughout the non-denning period. Adult females did not appear to utilise marking trees to advertise oestrous state during the breeding season. The function of marking by subadult bears is somewhat unclear, but may be related to the behaviour of adult males. Subadults investigated trees more often than they scent marked during the breeding season, which could be a result of an increased risk from adult males. Females with young showed an increase in marking and investigation of trees outside of the breeding season. We propose the hypothesis that females engage their dependent young with marking trees from a young age, at a relatively 'safe' time of year. Memory, experience, and learning at a young age, may all contribute towards odour capabilities in adult bears.

  9. Effect of the Temperature-Emissivity Contrast on the Chemical Signal for Gas Plume Detection Using Thermal Image Data

    Science.gov (United States)

    Walsh, Stephen; Chilton, Larry; Tardiff, Mark; Metoyer, Candace

    2008-01-01

    Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temperature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on chemical signal are described. This analysis shows that the plume's physical state, emission or absorption, is directly dependent on the background emissivity and plume/ground temperatures. It then describes what conditions on the background emissivity and plume/ground temperatures have inhibiting or amplifying effects on the chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the adaptive matched filter using two chemicals and three distinct background emissivities.

  10. Effect of the Temperature-Emissivity Contrast on the Chemical Signal for Gas Plume Detection Using Thermal Image Data

    Directory of Open Access Journals (Sweden)

    Candace Metoyer

    2008-10-01

    Full Text Available Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temperature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on chemical signal are described. This analysis shows that the plume’s physical state, emission or absorption, is directly dependent on the background emissivity and plume/ground temperatures. It then describes what conditions on the background emissivity and plume/ground temperatures have inhibiting or amplifying effects on the chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the adaptive matched filter using two chemicals and three distinct background emissivities.

  11. Effect of the Temperature-Emissivity Contrast on the Chemical Signal for Gas Plume Detection Using Thermal Image Data

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, Stephen; Chilton, Lawrence; Tardiff, Mark F.; Metoyer, Candace N.

    2008-10-21

    Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temperature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on net chemical signal are described. This analysis shows that the plume’s physical state, emission or absorption, is directly dependent on that background emissivity. It then describes what conditions on the background emissivity have inhibiting effects on the net chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the Adaptive Matched Filter using two chemicals and three distinct background emissivities.

  12. Gradient Echo Plural Contrast Imaging – signal model and derived contrasts: T2*, T1, Phase, SWI, T1f, FST2*and T2*-SWI

    OpenAIRE

    Luo, Jie; Jagadeesan, Bharathi D.; Cross, Anne H.; Yablonskiy, Dmitriy A.

    2012-01-01

    Gradient Echo Plural Contrast Imaging (GEPCI) is a post processing technique that, based on a widely available multiple gradient echo sequence, allows simultaneous generation of naturally co-registered images with various contrasts: T1 weighted, R2* = 1/T2* maps and frequency (f) maps. Herein, we present results demonstrating the capability of GEPCI technique to generate image sets with additional contrast characteristics obtained by combing the information from these three basic contrast map...

  13. Generation and precise control of dynamic biochemical gradients for cellular assays

    CERN Document Server

    Saka, Yasushi; Giuraniuc, Claudiu V

    2016-01-01

    Spatial gradients of diffusible signalling molecules play crucial roles in controlling diverse cellular behaviour such as cell differentiation, tissue patterning and chemotaxis. Here we present a microfluidic platform for cellular assays that can generate and control diffusion-based gradients dynamically. A unique design of the device eliminates cross-flow between the source and sink channels, thereby stabilising gradients by passive diffusion. The platform also enables quick and flexible control of chemical concentration that makes highly dynamic gradients in diffusion chambers. Budding yeast cells cultured in a gradient of a chemical inducer expressed a reporter fluorescence protein in a concentration-dependent manner. This microfluidic platform serves as a versatile prototype applicable to a broad range of biomedical investigations.

  14. Flat lizard female mimics use sexual deception in visual but not chemical signals

    OpenAIRE

    Martin J Whiting; Webb, Jonathan K.; Keogh, J. Scott

    2009-01-01

    Understanding what constrains signalling and maintains signal honesty is a central theme in animal communication. Clear cases of dishonest signalling, and the conditions under which they are used, represent an important avenue for improved understanding of animal communication systems. Female mimicry, when certain males take on the appearance of females, is most commonly a male alternative reproductive tactic that is condition-dependent. A number of adaptive explanations for female mimicry ha...

  15. Allied-Signal's Mary Good Analyzes New Threats to Chemical Profession.

    Science.gov (United States)

    Chemical and Engineering News, 1986

    1986-01-01

    Recounts an interview with chemist, educator, and executive Mary Good. Opinions are expressed about the status of basic research in chemistry, the relationship of chemical research to several federal agencies, the value of education in chemistry, and the perceptions of the public regarding the chemical community, particularly the health risks. (TW)

  16. Evolution of stalk/spore ratio in a social amoeba: cell-to-cell interaction via a signaling chemical shaped by cheating risk.

    Science.gov (United States)

    Uchinomiya, Kouki; Iwasa, Yoh

    2013-11-01

    The social amoeba (or cellular slime mold) is a model system for cell cooperation. When food is depleted in the environment, cells aggregate together. Some of these cells become stalks, raising spores to aid in their dispersal. Differentiation-inducing factor-1 (DIF-1) is a signaling chemical produced by prespore cells and decomposed by prestalk cells. It affects the rate of switching between prestalk and prespore cells, thereby achieving a stable stalk/spore ratio. In this study we analyzed the evolution of the stalk/spore ratio. Strains may differ in the production and decomposition rates of the signaling chemical, and in the sensitivity of cells to switch in response to the signaling chemical exposure. When two strains with the same stalk/spore ratio within their own fruiting body are combined into a single fruiting body, one strain may develop into prespores to a greater degree than the other. Direct evolutionary simulations and quantitative genetic dynamics demonstrate that if a fruiting body is always formed by a single strain, the cells evolve to produce less signaling chemical and become more sensitive to the signaling chemical due to the cost of producing the chemical. In contrast, if a fruiting body is formed by multiple strains, the cells evolve to become less sensitive to the signaling chemical and produce more signaling chemical in order to reduce the risk of being exploited. In contrast, the stalk-spore ratio is less likely to be affected by small cheating risk. PMID:23911583

  17. A cleaning method to minimize contaminant luminescence signal of empty sample carriers using off-the-shelf chemical agents

    International Nuclear Information System (INIS)

    Signals acquired during thermoluminescence or optically stimulated luminescence measurements must be completely free of any spurious and/or contamination signals to assure the credibility of the results, especially during exploratory research investigating the luminescence behavior of new materials. Experiments indicate that such unwanted signals may also stem from new (unused) and used empty sample carriers, namely cups and discs, which are widely used for such measurements, probably due to contamination from a fluorite and/or silica-related source. Fluorite and/or silicone oil appear to be the most likely sources of contamination, thus, their removal, along with any other possible source that exhibits undesirable luminescence behavior, is necessary. Conventional cleaning methods fail to eliminate such contaminants from empty cups and discs. In this work a new cleaning method is proposed incorporating off-the-shelf chemical agents. Results of thermoluminescence measurements highlight the efficiency of the new cleaning process, since it can completely remove any observed contaminants from both new and used sample carriers, of various shapes and/or materials. Consequently their signal is minimized even at relatively high beta-doses, where it is prominent, resulting in a clean and only sample-attributed signal. - Highlights: • New and used empty sample carriers suffer from contamination from a fluorite and silica-related source. • A new cleaning method for empty sample carriers is proposed using off-the-shelf chemical agents. • The new method can eliminate any contamination from empty sample holders of various shapes and/or materials. • Contamination signals are reduced to the background level even at relatively high doses (100 Gy)

  18. Mixed convective MHD flow of a micropolar fluid with ohmic heating, radiation and viscous dissipation over a chemically reacting porous plate subjected to a constant heat flux and concentration gradient

    OpenAIRE

    Kumar Hitesh

    2014-01-01

    In the present paper analysis of a chemically reacting mixed convection MHD micropolar flow, heat and mass transfer in porous medium with the effects of ohmic heating, radiation and viscous dissipation past an infinite vertical plate which is subjected to a constant heat flux and the concentration gradient. The non-linear coupled partial differential equations are solved numerically using an implicit finite difference scheme known as Keller-box method. The ...

  19. Raman signal enhancement by multiple beam excitation and its application for the detection of chemicals

    International Nuclear Information System (INIS)

    In a typical Raman based sensor, a single laser beam is used for exciting the sample and the backscattered or forward scattered light is collected using collection optics and is analyzed by a spectrometer. We have investigated that by means of exciting the sample with multiple beams, i.e., by dividing the same input power of the single beam into two or three or more beams and exciting the sample from different angles, the Raman signal enhances significantly. Due to the presence of multiple beams passing through the same volume of the sample, an interference pattern is formed and the volume of interaction of excitation beams with the sample increases. By means of this geometry, the enhancement in the Raman signal is observed and it was found that the signal strength increases linearly with the increase in number of excitation beams. Experimental results of this scheme for excitation of the samples are reported for explosive detection at a standoff distance

  20. The roles of mechanical compression and chemical irritation in regulating spinal neuronal signaling in painful cervical nerve root injury.

    Science.gov (United States)

    Zhang, Sijia; Nicholson, Kristen J; Smith, Jenell R; Gilliland, Taylor M; Syré, Peter P; Winkelstein, Beth A

    2013-11-01

    Both traumatic and slow-onset disc herniation can directly compress and/or chemically irritate cervical nerve roots, and both types of root injury elicit pain in animal models of radiculopathy. This study investigated the relative contributions of mechanical compression and chemical irritation of the nerve root to spinal regulation of neuronal activity using several outcomes. Modifications of two proteins known to regulate neurotransmission in the spinal cord, the neuropeptide calcitonin gene-related peptide (CGRP) and glutamate transporter 1 (GLT-1), were assessed in a rat model after painful cervical nerve root injuries using a mechanical compression, chemical irritation or their combination of injury. Only injuries with compression induced sustained behavioral hypersensitivity (p≤0.05) for two weeks and significant decreases (pspinal CGRP and GLT-1 is associated with enhanced excitatory signaling in the spinal cord, a second study evaluated the electrophysiological properties of neurons in the superficial and deeper dorsal horn at day 7 after a painful root compression. The evoked firing rate was significantly increased (p=0.045) after compression and only in the deeper lamina. The painful compression also induced a significant (p=0.002) shift in the percentage of neurons in the superficial lamina classified as low- threshold mechanoreceptive (sham 38%; compression 10%) to those classified as wide dynamic range neurons (sham 43%; compression 74%). Together, these studies highlight mechanical compression as a key modulator of spinal neuronal signaling in the context of radicular injury and pain. PMID:24435733

  1. Measurement of small-signal gain on COIL with chemically generated molecular iodine

    Czech Academy of Sciences Publication Activity Database

    Jirásek, Vít; Špalek, Otomar; Čenský, Miroslav; Kodymová, Jarmila

    2010-01-01

    Roč. 46, č. 9 (2010), s. 1350-1353. ISSN 0018-9197 Institutional research plan: CEZ:AV0Z10100523 Keywords : chemical laser s * iodine * gain measurement Subject RIV: BH - Optics, Masers, Laser s Impact factor: 2.477, year: 2010

  2. Regulation of Stem Cell Proliferation and Cell Fate Specification by Wingless/Wnt Signaling Gradients Enriched at Adult Intestinal Compartment Boundaries.

    OpenAIRE

    Ai Tian; Hassina Benchabane; Zhenghan Wang; Yashi Ahmed

    2016-01-01

    Intestinal stem cell (ISC) self-renewal and proliferation are directed by Wnt/β-catenin signaling in mammals, whereas aberrant Wnt pathway activation in ISCs triggers the development of human colorectal carcinoma. Herein, we have utilized the Drosophila midgut, a powerful model for ISC regulation, to elucidate the mechanisms by which Wingless (Wg)/Wnt regulates intestinal homeostasis and development. We provide evidence that the Wg signaling pathway, activation of which peaks at each of the m...

  3. On gradient field theories: gradient magnetostatics and gradient elasticity

    OpenAIRE

    Lazar, Markus

    2014-01-01

    In this work the fundamentals of gradient field theories are presented and reviewed. In particular, the theories of gradient magnetostatics and gradient elasticity are investigated and compared. For gradient magnetostatics, non-singular expressions for the magnetic vector gauge potential, the Biot-Savart law, the Lorentz force and the mutual interaction energy of two electric current loops are derived and discussed. For gradient elasticity, non-singular forms of all dislocation key-formulas (...

  4. The nature of alarm communication in Constrictotermes cyphergaster (Blattodea: Termitoidea: Termitidae: the integration of chemical and vibroacoustic signals

    Directory of Open Access Journals (Sweden)

    Paulo F. Cristaldo

    2015-12-01

    Full Text Available Alarm signalling is of paramount importance to communication in all social insects. In termites, vibroacoustic and chemical alarm signalling are bound to operate synergistically but have never been studied simultaneously in a single species. Here, we inspected the functional significance of both communication channels in Constrictotermes cyphergaster (Termitidae: Nasutitermitinae, confirming the hypothesis that these are not exclusive, but rather complementary processes. In natural situations, the alarm predominantly attracts soldiers, which actively search for the source of a disturbance. Laboratory testing revealed that the frontal gland of soldiers produces a rich mixture of terpenoid compounds including an alarm pheromone. Extensive testing led to identification of the alarm pheromone being composed of abundant monoterpene hydrocarbons (1S-α-pinene and myrcene, along with a minor component, (E-β-ocimene. The vibratory alarm signalling consists of vibratory movements evidenced as bursts; a series of beats produced predominantly by soldiers. Exposing termite groups to various mixtures containing the alarm pheromone (crushed soldier heads, frontal gland extracts, mixture of all monoterpenes, and the alarm pheromone mixture made of standards resulted in significantly higher activity in the tested groups and also increased intensity of the vibratory alarm communication, with the responses clearly dose-dependent. Lower doses of the pheromone provoked higher numbers of vibratory signals compared to higher doses. Higher doses induced long-term running of all termites without stops necessary to perform vibratory behaviour. Surprisingly, even crushed worker heads led to low (but significant increases in the alarm responses, suggesting that other unknown compound in the worker's head is perceived and answered by termites. Our results demonstrate the existence of different alarm levels in termites, with lower levels being communicated through

  5. Signal of New Physics and Chemical Composition of Matter in Core Crossing Neutrinos

    OpenAIRE

    Liao, Wei(Institute of Modern Physics, School of Science, East China University of Science and Technology, Shanghai, China)

    2008-01-01

    We consider non-standard matter effect in flavor conversion of neutrinos crossing the core of the Earth. We show that oscillation of core crossing neutrinos with $E \\gsim 0.5$ GeV can be well described by a first order perturbation theory. We show that due to non-standard matter effect varying chemical composition in the Earth can modify the neutrino flavor conversion by 100%. Effects of CP violating phases in non-standard Neutral Current interactions are emphasized in particular.

  6. Volatile codes: Correlation of olfactory signals and reception in Drosophila-yeast chemical communication.

    Science.gov (United States)

    Scheidler, Nicole H; Liu, Cheng; Hamby, Kelly A; Zalom, Frank G; Syed, Zainulabeuddin

    2015-01-01

    Drosophila have evolved strong mutualistic associations with yeast communities that best support their growth and survival, resulting in the development of novel niches. It has been suggested that flies recognize their cognate yeasts primarily based on the rich repertoire of volatile organic compounds (VOCs) derived from the yeasts. Thus, it remained an exciting avenue to study whether fly spp. detect and discriminate yeast strains based on odor alone, and if so, how such resolution is achieved by the olfactory system in flies. We used two fly species known to exploit different niches and harboring different yeasts, D. suzukii (a pest of fresh fruit) and D. melanogaster (a saprophytic fly and a neurogenetic model organism). We initially established the behavioral preference of both fly species to six Drosophila-associated yeasts; then chemically analyzed the VOC profile of each yeast which revealed quantitative and qualitative differences; and finally isolated and identified the physiologically active constituents from yeast VOCs for each drosophilid that potentially define attraction. By employing chemical, behavioral, and electrophysiological analyses, we provide a comprehensive portrait of the olfactory neuroethological correlates underlying fly-yeast coadaptation in two drosophilids with distinct habitats. PMID:26391997

  7. Mixed convective MHD flow of a micropolar fluid with ohmic heating, radiation and viscous dissipation over a chemically reacting porous plate subjected to a constant heat flux and concentration gradient

    Directory of Open Access Journals (Sweden)

    Kumar Hitesh

    2014-01-01

    Full Text Available In the present paper analysis of a chemically reacting mixed convection MHD micropolar flow, heat and mass transfer in porous medium with the effects of ohmic heating, radiation and viscous dissipation past an infinite vertical plate which is subjected to a constant heat flux and the concentration gradient. The non-linear coupled partial differential equations are solved numerically using an implicit finite difference scheme known as Keller-box method. The results for concentration, transverse velocity, angular velocity and temperature are obtained and illustrated graphically to observe the effects of various parameters, and the numerical discussion is presented with physical interpretations.

  8. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  9. Chemical Composition and Disruption of Quorum Sensing Signaling in Geographically Diverse United States Propolis

    Directory of Open Access Journals (Sweden)

    Michael A. Savka

    2015-01-01

    Full Text Available Propolis or bee glue has been used for centuries for various purposes and is especially important in human health due to many of its biological and pharmacological properties. In this work we showed quorum sensing inhibitory (QSI activity of ten geographically distinct propolis samples from the United States using the acyl-homoserine lactone- (AHL- dependent Chromobacterium violaceum strain CV026. Based on GC-MS chemical profiling the propolis samples can be classified into several groups that are as follows: (1 rich in cinnamic acid derivatives, (2 rich in flavonoids, and (3 rich in triterpenes. An in-depth analysis of the propolis from North Carolina led to the isolation and identification of a triterpenic acid that was recently isolated from Hondurian propolis (Central America and ethyl ether of p-coumaric alcohol not previously identified in bee propolis. QSI activity was also observed in the second group US propolis samples which contained the flavonoid pinocembrin in addition to other flavonoid compounds. The discovery of compounds that are involved in QSI activity has the potential to facilitate studies that may lead to the development of antivirulence therapies that can be complementary and/or alternative treatments against antibiotic resistant bacterial pathogens and/or emerging pathogens that have yet to be identified.

  10. Developments of segregation process and chemical analysis for virus receptor recognizing environmental signal substance by affinity binding assaying

    International Nuclear Information System (INIS)

    Virus receptors recognizing environmental signal were segregated and analyzed chemically by affinity binding assaying using radio-isotope marked compound. Pathogenic protein in rice stem virus was indicated possibility of a protein which participates in transfer process between the virus cells. An enzyme, Chitobiose was separated from a bacteria, actinomycete. It was cleared by 3H chitobiose affinity binding assaying that two kinds of chitobiose binding protein existed in cell membrane of the actinomycete. A different kind of protein was founded in the cell membrane which was raised in existence of chitobiose. Observation showed that the protein was different from a protein in the cell membrane which was raised in non-existence of chitobiose. These two kinds of protein might be formed a complex compound on the surface of cell membrane. (M. Suetake)

  11. Determination of the desertification processes by means of the some soil physico-chemical properties analysis along a climate gradient. (South of Spain).

    Science.gov (United States)

    Ruiz Sinoga, J. D.; Martinez Murillo, J. F.; Romero Diaz, A.

    2009-04-01

    The pluviometric gradient located in the South of Spain shows one of the European areas affected by desertification processes. In most of the cases, desertification processes are related directly with the hydrological erosion processes, when from the functional point of view could be the consequence. The erosional dynamic along a hillslopes with these soil particles movements generated processes lead to important changes of some properties. Such changes can modify the soil hydrological behaviour with a soil productivity loss and consequently a vegetation cover reduction, favouring the soil erosion processes what have been termed feedback processes, which final will be the appear of non-return situations. Mainly, such soil properties are aggregate stability, porosity, gravels, clay, organic matter, soluble salt, carbonate content, soil organic carbon, cationic exchange capacity and saturated hydraulic conductivity. Also the soil erodibility was calculate through the K factor of USLE. The investigation boards the study of the mentioned processes through the methodology of the analogue situations reproduction in the South of Spain (Bethics Chain) and along a climatic gradient. They are areas with metamorphic rocks (schists anf filithes), high slope gradient and very shallow soils due to a historical management in the most of the cases. Has been defined a climatic gradient at this area, which fluctuates from 1100 mm/y-1 at Gaucin, 750 mm/y-1 al Marbella, 590 mm/y-1 at Almogia, 330 mm/y-1 at Berja and 240 mm/y-1. at Gergal. The soils samples were collected in the south facing slopes, of each field site, and the amount of soil were 60 in each field site, with one total amount of 300 soils samples. We have selected a representative hillslopes with a similar exposition and length in every one of each area. The final results shown modifications in the soil and hydrological properties studied with the increasing of the aridity, and the protector role of vegetation cover

  12. The Sexual Behaviour of Chagas' Disease Vectors: Chemical Signals Mediating Communication between Male and Female Triatomine Bugs

    Directory of Open Access Journals (Sweden)

    Gabriel Manrique

    2012-01-01

    Full Text Available Chemical communication mechanisms that mediate sexual behaviour in triatomine bugs are reviewed with regard to source, identity, and function of sex pheromones. Males attempt to copulate but may be rejected, depending on female age and nutritional status. Triatomine males locate partners through sex pheromones emitted by the metasternal glands (MGs of females. These activate males, inducing them to leave their refuges and initiate flight. Wandering males display anemotactic orientation modulated by chemical signals emitted from female MGs. Analyses of the MG secretions of several species resulted in the identification of numerous ketones, acetals, and alcohols. Occlusion experiments showed that Brindley’s gland products were not required for mating. Metasternal gland volatiles are emitted by virgin male and female bugs, with detection over females occurring more consistently, especially during the early scotophase, suggesting female calling behaviour. Mating triatomine females have been reported to attract males that tend to copulate successively with them. Mating males prolong mating and postcopulatory mate guarding in the presence of other males. This is indicative of a polyandrous mating system in several triatomine species. Its potential advantages remain unknown, and comparative studies are required to increase our understanding of triatomine reproductive strategies.

  13. Comparison of multi-echo dixon methods with volume interpolated breath-hold gradient magnetic resonance imaging in fat-signal fraction quantification of paravaertebral muscle

    International Nuclear Information System (INIS)

    To assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2* estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2*-corrected two-echo Dixon or T2*-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard. Sixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2*-corrected Dixon technique with two (non-T2*-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences. A total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 ± 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods. T2*-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification

  14. Sensory Drive Mediated by Climatic Gradients Partially Explains Divergence in Acoustic Signals in Two Horseshoe Bat Species, Rhinolophus swinnyi and Rhinolophus simulator.

    Science.gov (United States)

    Mutumi, Gregory L; Jacobs, David S; Winker, Henning

    2016-01-01

    Geographic variation can be an indicator of still poorly understood evolutionary processes such as adaptation and drift. Sensory systems used in communication play a key role in mate choice and species recognition. Habitat-mediated (i.e. adaptive) differences in communication signals may therefore lead to diversification. We investigated geographic variation in echolocation calls of African horseshoe bats, Rhinolophus simulator and R. swinnyi in the context of two adaptive hypotheses: 1) James' Rule and 2) the Sensory Drive Hypothesis. According to James' Rule body-size should vary in response to relative humidity and temperature so that divergence in call frequency may therefore be the result of climate-mediated variation in body size because of the correlation between body size and call frequency. The Sensory Drive Hypothesis proposes that call frequency is a response to climate-induced differences in atmospheric attenuation and predicts that increases in atmospheric attenuation selects for calls of lower frequency. We measured the morphology and resting call frequency (RF) of 111 R. simulator and 126 R. swinnyi individuals across their distributional range to test the above hypotheses. Contrary to the prediction of James' Rule, divergence in body size could not explain the variation in RF. Instead, acoustic divergence in RF was best predicted by latitude, geography and climate-induced differences in atmospheric attenuation, as predicted by the Sensory Drive Hypothesis. Although variation in RF was strongly influenced by temperature and humidity, other climatic variables (associated with latitude and altitude) as well as drift (as suggested by a positive correlation between call variation and geographic distance, especially in R. simulator) may also play an important role. PMID:26815436

  15. Comparison of multi-echo dixon methods with volume interpolated breath-hold gradient magnetic resonance imaging in fat-signal fraction quantification of paravaertebral muscle

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Yeon Hwa; Kim, Hak Sun; Lee, Young Han [Dept. of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of); and others

    2015-10-15

    To assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2{sup *} estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2{sup *}-corrected two-echo Dixon or T2{sup *}-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard. Sixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2{sup *}-corrected Dixon technique with two (non-T2{sup *}-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences. A total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 ± 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods. T2{sup *}-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification.

  16. IN-SITU IONIC CHEMICAL ANALYSIS OF FRESH WATER VIA A NOVEL COMBINED MULTI-SENSOR / SIGNAL PROCESSING ARCHITECTURE

    Science.gov (United States)

    Mueller, A. V.; Hemond, H.

    2009-12-01

    The capability for comprehensive, real-time, in-situ characterization of the chemical constituents of natural waters is a powerful tool for the advancement of the ecological and geochemical sciences, e.g. by facilitating rapid high-resolution adaptive sampling campaigns and avoiding the potential errors and high costs related to traditional grab sample collection, transportation and analysis. Portable field-ready instrumentation also promotes the goals of large-scale monitoring networks, such as CUASHI and WATERS, without the financial and human resources overhead required for traditional sampling at this scale. Problems of environmental remediation and monitoring of industrial waste waters would additionally benefit from such instrumental capacity. In-situ measurement of all major ions contributing to the charge makeup of natural fresh water is thus pursued via a combined multi-sensor/multivariate signal processing architecture. The instrument is based primarily on commercial electrochemical sensors, e.g. ion selective electrodes (ISEs) and ion selective field-effect transistors (ISFETs), to promote low cost as well as easy maintenance and reproduction,. The system employs a novel architecture of multivariate signal processing to extract accurate information from in-situ data streams via an "unmixing" process that accounts for sensor non-linearities at low concentrations, as well as sensor cross-reactivities. Conductivity, charge neutrality and temperature are applied as additional mathematical constraints on the chemical state of the system. Including such non-ionic information assists in obtaining accurate and useful calibrations even in the non-linear portion of the sensor response curves, and measurements can be made without the traditionally-required standard additions or ionic strength adjustment. Initial work demonstrates the effectiveness of this methodology at predicting inorganic cations (Na+, NH4+, H+, Ca2+, and K+) in a simplified system containing

  17. Mathematics of Experimentally Generated Chemoattractant Gradients

    NARCIS (Netherlands)

    M. Postma; P.J.M. van Haastert

    2016-01-01

    Many eukaryotic cells move in the direction of a chemical gradient. Several assays have been developed to measure this chemotactic response, but no complete mathematical models of the spatial and temporal gradients are available to describe the fundamental principles of chemotaxis. Here we provide a

  18. A post-modification approach to independent component analysis for resolution of overlapping GC/MS signals: from independent components to chemical components

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; CAI WenSheng; SHAO XueGuang

    2007-01-01

    Independent component analysis (ICA) has demonstrated its power to extract mass spectra from overlapping GC/MS signal. However, there is still a problem that mass spectra with negative peaks at some m/z will be obtained in the resolved results when there are overlapping peaks in the mass spectra of a mixture. Based on a detail theoretical analysis of the preconditions for ICA and the non-negative property of GC/MS signals, a post-modification based on chemical knowledge (PMBK) strategy is proposed to solve this problem. By both simulated and experimental GC/MS signals, it was proved that the PMBK strategy can improve the resolution effectively.

  19. Additive effects on the androgen signaling pathway by chemicals with different modes of action-COW2015

    Science.gov (United States)

    Risk assessments have traditionally been developed on a chemical-by-chemical basis. However, regulatory agencies recently have been considering cumulative effects of chemicals that act via a common mechanism of toxicity. Here we present data on several mixture studies of chemic...

  20. Workshop on Key Issues in Major Research Plan "Study on the Signal Conduction Process Based on Chemical Small Molecular Probe" Held

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The workshop on key analysis method and largescale facilities application in the project of Major Research Plan "Study on the Signal Conduction Process Based on Chemical Small Molecular Probe" was held in the National Synchrotron Radiation Laboratory, Anhui on January 5th, 2008.

  1. Characterization of Leached Phosphorus from Soil, Manure, and Manure-Amended Soil by Physical and Chemical Fractionation and Diffusive Gradients in Thin Films (DGT)

    DEFF Research Database (Denmark)

    Glæsner, Nadia; Donner, Erica; Magid, Jakob;

    2012-01-01

    We are challenged to date to fully understand mechanisms controlling phosphorus (P) mobilization in soil. In this study we evaluated physical properties, chemical reactivity, and potential bioavailability of P mobilized in soil during a leaching event and examined how the amounts and properties of...... leached P were influenced by surface application of cattle manure. Leaching experiments on manure itself, and on intact soil columns (14.1 cm inner dia., 25 cm height) before and after manure application, were carried out at an irrigation rate of 1 mm h−1 for 48 h. High concentrations of dissolved...... reactive P (DRP) were found in manure leachates (up to 32 mg L−1), whereas concentrations of P in soil leachates were low both before and after manure application (around 0.04 mg L−1 before application and up to 0.4 mg L−1 afterward). This result indicates that the soil retained most of the P added with...

  2. Optimization of nuclear magnetic resonance refocusing pulses to enhance signal intensity in gradient B0 field∗%优化重聚脉冲提高梯度场核磁共振信号强度*

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

      缩短射频脉冲宽度,有助于解决脉冲电力消耗大、样品吸收率高、信噪比低等极端条件核磁共振探测的关键问题。本文首先分析射频脉冲角度对核磁共振自旋回波信号强度的影响机理,基于Bloch方程推导了回波信号幅度与扳转角、重聚角的关系。在特制核磁共振分析仪上采用变脉冲角度技术,分别在均匀磁场和梯度磁场条件下实现对扳转角和重聚角与回波信号强度关系的数值模拟和实验测量。结果表明,梯度场中,扳转角为90◦、重聚角为140◦的射频脉冲组合获得最大首波信号强度,比180◦脉冲对应的回波幅值提高13%,能耗降低至78%。选用该重聚角(140◦)优化设计饱和恢复脉冲序列探测流体的纵向弛豫时间T1特性,准确获得T1分布。该结果对于低电力供应、且对信噪比有较高要求的核磁共振测量,如随钻核磁共振测井和在线核磁共振快速检测等,具有重要意义。%It is an efficient protocol to use the refocusing flip angle pulse optimization technique to solve special engineering technical problems in nuclear magnetic resonance (NMR) measurements. By reducing RF pulse duration, the low refocusing flip angle pulses can consume lower power, satisfy specific absorption rate of samples, and improve signal-to-noise ratio as well. To further analyze the function mechanism of pulse angles, the dependence of signal intensity on RF pulse is studied in homogenous magnetic field and constant gradient magnetic field respectively. Afterwards, echo amplitudes with various tip angles and flip angles ranging from 0◦ to 180◦ are compared with conventional sequence of 90◦ pulse followed by 180◦ pulses theoretically and experimentally. For the constant gradient field, the refocusing pulse of flip angle can be as low as 140◦, defined as the optimum herein, to obtain the strongest signal intensity, enhanced by 13%compared with that

  3. Differentiation between focal malignant marrow-replacing lesions and benign red marrow deposition of the spine with T2{sup *}-corrected fat-signal fraction map using a three -echo volume interpolated breath-hold gradient echo dixon sequence

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Pyo; Kim, Sung Jun; Chung, Tae Sub; Yoo, Yeon Hwa; Yoon, Choon Sik [Dept. of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of); Kanneengiesser, Stephan [MR Applications Development, Siemens AG, Healthcare Sector, Erlangen (Germany); Paek, Moon Young [Siemens Ltd., Seoul (Korea, Republic of); Song, Ho Taek; Lee, Young Han; Suh, Jin Suck [Dept. of Radiology, Severance Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2014-12-15

    To assess the feasibility of T2{sup *}-corrected fat-signal fraction (FF) map by using the three-echo volume interpolated breath-hold gradient echo (VIBE) Dixon sequence to differentiate between malignant marrow-replacing lesions and benign red marrow deposition of vertebrae. We assessed 32 lesions from 32 patients who underwent magnetic resonance imaging after being referred for assessment of a known or possible vertebral marrow abnormality. The lesions were divided into 21 malignant marrow-replacing lesions and 11 benign red marrow depositions. Three sequences for the parameter measurements were obtained by using a 1.5-T MR imaging scanner as follows: three-echo VIBE Dixon sequence for FF; conventional T1-weighted imaging for the lesion-disc ratio (LDR); pre- and post-gadolinium enhanced fat-suppressed T1-weighted images for the contrast-enhancement ratio (CER). A region of interest was drawn for each lesion for parameter measurements. The areas under the curve (AUC) of the parameters and their sensitivities and specificities at the most ideal cutoff values from receiver operating characteristic curve analysis were obtained. AUC, sensitivity, and specificity were respectively compared between FF and CER. The AUCs of FF, LDR, and CER were 0.96, 0.80, and 0.72, respectively. In the comparison of diagnostic performance between the FF and CER, the FF showed a significantly larger AUC as compared to the CER (p = 0.030), although the difference of sensitivity (p = 0.157) and specificity (p = 0.157) were not significant. Fat-signal fraction measurement using T2{sup *}-corrected three-echo VIBE Dixon sequence is feasible and has a more accurate diagnostic performance, than the CER, in distinguishing benign red marrow deposition from malignant bone marrow-replacing lesions.

  4. Mathematics of Experimentally Generated Chemoattractant Gradients.

    Science.gov (United States)

    Postma, Marten; van Haastert, Peter J M

    2016-01-01

    Many eukaryotic cells move in the direction of a chemical gradient. Several assays have been developed to measure this chemotactic response, but no complete mathematical models of the spatial and temporal gradients are available to describe the fundamental principles of chemotaxis. Here we provide analytical solutions for the gradients formed by release of chemoattractant from a point source by passive diffusion or forced flow (micropipettes) and gradients formed by laminar diffusion in a Zigmond chamber. The results show that gradients delivered with a micropipette are formed nearly instantaneously, are very steep close to the pipette, and have a steepness that is strongly dependent on the distance from the pipette. In contrast, gradients in a Zigmond chamber are formed more slowly, are nearly independent of the distance from the source, and resemble the temporal and spatial properties of the natural cAMP wave that Dictyostelium cells experience during cell aggregation. PMID:27271915

  5. Injuries to Scots pine mycorrhizas and chemical gradients in forest soil in the environment of a pulp mill in Central Finland

    International Nuclear Information System (INIS)

    The occurrence and condition of Scots pine mycorrhizas were studied at different distances from a pulp mill in Central Finland. The chemical analyses of the soil humus layer in the vicinity of the mill revealed increased levels of ammonium-nitrogen, sulphur and calcium but unaltered concentrations of phosphorus and magnesium. Higher nitrate levels and nitrification were clearly detected at some sites which had recently been limed. Significant decreases in root ramification index and number of living mycorrhizas were found in a 0-0.6 km zone surrounding the factory but these parameters increased with increasing distance. Within a 2 km zone around the mill there were abundant Cenococcum geophilus and Paxilus involutus-type mycorrhizas while lowered frequencies of several other mycorrhizal types were detected. An ultrastructural study revealed changes in several types of mycorrhizas, the clearest of which were increased tannin deposition in cortical cells, intracellular growth of hyphae in cortical cells and the appearance of electron dense accumulations in the vacuoles of the funal cells. The ultrastructural changes observed were distributed at least to a distance of 3 km from the mill and occurred in the roots of trees that had only a slight loss of needle mass. Nitrogen deposition is suspected to be the primary cause of root decline but atmospheric SO2 through the tree crown is also likely to be a contributing factor. 37 refs., 10 figs., 7 tabs

  6. A Standardized Chemically Modified Curcuma longa Extract Modulates IRAK-MAPK Signaling in Inflammation and Potentiates Cytotoxicity.

    Science.gov (United States)

    Rana, Minakshi; Maurya, Preeti; Reddy, Sukka S; Singh, Vishal; Ahmad, Hafsa; Dwivedi, Anil K; Dikshit, Madhu; Barthwal, Manoj K

    2016-01-01

    The TLR/IL-1R pathway is a critical signaling module that is misregulated in pathologies like inflammation and cancer. Extracts from turmeric (Curcuma longa L.) enriched in curcumin and carbonyls like turmerones have been shown to exert potent anti-inflammatory effects. The present study evaluated the anti-inflammatory activity, cytotoxic effect and the underlying mechanism of a novel chemically modified, non-carbonyl compound enriched Curcuma longa L. (C. longa) extract (CMCE). CMCE (1 or 10 μg/mL; 14 h) significantly decreased LPS (50-100 ng/mL) induced TNF-α and IL-1β production in THP-1 cells, human, and mouse whole blood as measured by ELISA. LPS-induced IRAK1, MAPK activation, TLR4 expression, TLR4-MyD88 interaction, and IκBα degradation were significantly reduced in CMCE pre-treated THP-1 cells as assessed by Western blotting. CMCE (30, 100, and 300 mg/kg; 10 days p.o.) pre-treated and LPS (10 mg/kg) challenged Swiss mice exhibited attenuated plasma TNF-α, IL-1β, nitrite, aortic iNOS expression, and vascular dysfunction. In a PI permeability assay, cell lines derived from acute myeloid leukemia were most sensitive to the cytotoxic effects of CMCE. Analysis of Sub-G1 phase, Annexin V-PI positivity, loss of mitochondrial membrane potential, increased caspase-3, and PARP-1 activation confirmed CMCE induced apoptosis in HL-60 cells. IRAK inhibition also sensitized HL-60 cells to CMCE induced cytotoxicity. The present study defines the mechanism underlying the action of CMCE and suggests a therapeutic potential for its use in sepsis and leukemia. PMID:27504095

  7. Sintered composite gradient tool materials

    OpenAIRE

    J. Mikuła; G. Matula; K. Gołombek; L.A. Dobrzański

    2008-01-01

    Purpose: Development of a new generation of the composite gradient tool materials with the core sintered withthe matrix obtained using the powder metallurgy of the chemical composition corresponding to the HS6-5-2 highspeedsteel reinforced with the WC and TiC type hard carbide phases with the growing portions of these phases inthe outward direction from the core to the surface.Design/methodology/approach: Powder Metallurgy, SEM, X-Ray Microanalysis.Findings: Powder metallurgy processes were u...

  8. Small Molecule DFPM Derivative-Activated Plant Resistance Protein Signaling in Roots Is Unaffected by EDS1 Subcellular Targeting Signal and Chemical Genetic Isolation of victr R-Protein Mutants.

    Directory of Open Access Journals (Sweden)

    Hans-Henning Kunz

    Full Text Available The small molecule DFPM ([5-(3,4-dichlorophenylfuran-2-yl]-piperidine-1-ylmethanethione was recently shown to trigger signal transduction via early effector-triggered immunity signaling genes including EDS1 and PAD4 in Arabidopsis thaliana accession Col-0. Chemical genetic analyses of A. thaliana natural variants identified the plant Resistance protein-like Toll/Interleukin1 Receptor (TIR-Nucleotide Binding (NB-Leucine-Rich Repeat (LRR protein VICTR as required for DFPM-mediated root growth arrest. Here a chemical genetic screen for mutants which disrupt DFPM-mediated root growth arrest in the Col-0 accession identified new mutant alleles of the TIR-NB-LRR gene VICTR. One allele, victr-6, carries a Gly216-to-Asp mutation in the Walker A domain supporting an important function of the VICTR nucleotide binding domain in DFPM responses consistent with VICTR acting as a canonical Resistance protein. The essential nucleo-cytoplasmic regulator of TIR-NB-LRR-mediated effector-triggered immunity, EDS1, was reported to have both nuclear and cytoplasmic actions in pathogen resistance. DFPM was used to investigate the requirements for subcellular EDS1 localization in DFPM-mediated root growth arrest. EDS1-YFP fusions engineered to localize mainly in the cytoplasm or the nucleus by tagging with a nuclear export signal (NES or a nuclear localization signal (NLS, respectively, were tested. We found that wild-type EDS1-YFP and both the NES and NLS-tagged EDS1 variants were induced by DFPM treatments and fully complemented eds1 mutant plants in root responses to DFPM, suggesting that enrichment of EDS1 in either compartment could confer DFPM-mediated root growth arrest. We further found that a light and O2-dependent modification of DFPM is necessary to mediate DFPM signaling in roots. Chemical analyses including Liquid Chromatography-Mass Spectrometry and High-Resolution Atmospheric Pressure Chemical Ionization Mass Spectrometry identified a DFPM modification

  9. A post-modification approach to independent compo-nent analysis for resolution of overlapping GC/MS signals:from independent components to chemical components

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Independent component analysis (ICA) has demonstrated its power to extract mass spectra from over-lapping GC/MS signal. However, there is still a problem that mass spectra with negative peaks at some m/z will be obtained in the resolved results when there are overlapping peaks in the mass spectra of a mixture. Based on a detail theoretical analysis of the preconditions for ICA and the non-negative property of GC/MS signals, a post-modification based on chemical knowledge (PMBK) strategy is pro-posed to solve this problem. By both simulated and experimental GC/MS signals, it was proved that the PMBK strategy can improve the resolution effectively.

  10. Spatially resolved electrochemical sensing of chemical gradients

    Czech Academy of Sciences Publication Activity Database

    Mensack, N.M.; Wydallis, J.B.; Lynn, Nicholas Scott; Dandy, D.S.; Henry, C.S.

    2013-01-01

    Roč. 13, č. 2 (2013), s. 208-2013. ISSN 1473-0197 Institutional support: RVO:67985882 Keywords : CARBON * CHEMOTAXIS * ELECTRODES Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 5.748, year: 2013

  11. Elimination of the background signal in tooth enamel samples for EPR-dosimetry by means of physical-chemical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ivannikov, A.I. E-mail: ivann@mail.ru; Tikunov, D.D.; Skvortsov, V.G.; Stepanenko, V.F.; Khomichyonok, V.V.; Khamidova, L.G.; Skripnik, D.D.; Bozadjiev, L.L.; Hoshi, M

    2001-11-01

    A method of elimination of the background EPR signal in tooth enamel is proposed. This method implies treatment of enamel powder by highly active reduction reagent hydrazine with subsequent washing out by ethanol-water solution. Such treatment results in reducing both the native background signal (which is assumed to be originated by the organic component) and the mechanical induced EPR signal in enamel. Testing of the efficiency of hydrazine treatment is made for different sizes of enamel powder. It is shown that the optimal results are obtained for a powder fraction of about 100-200 {mu}m. The radiation-induced EPR signal in enamel is practically not changed after treatment by hydrazine.

  12. The stellar metallicity gradients in galaxy discs in a cosmological scenario

    Science.gov (United States)

    Tissera, Patricia B.; Machado, Rubens E. G.; Sanchez-Blazquez, Patricia; Pedrosa, Susana E.; Sánchez, Sebastián F.; Snaith, Owain; Vilchez, Jose

    2016-08-01

    Context. The stellar metallicity gradients of disc galaxies provide information on disc assembly, star formation processes, and chemical evolution. They also might store information on dynamical processes that could affect the distribution of chemical elements in the gas phase and the stellar components. Understanding their joint effects within a hierarchical clustering scenario is of paramount importance. Aims: We studied the stellar metallicity gradients of simulated discs in a cosmological simulation. We explored the dependence of the stellar metallicity gradients on stellar age and on the size and mass of the stellar discs. Methods: We used a catalogue of galaxies with disc components selected from a cosmological hydrodynamical simulation performed including a physically motivated supernova feedback and chemical evolution. Disc components were defined based on angular momentum and binding energy criteria. The metallicity profiles were estimated for stars with different ages. We confront our numerical findings with results from the Calar Alto Legacy Integral Field Area (CALIFA) Survey. Results: The simulated stellar discs are found to have metallicity profiles with slopes in global agreement with observations. Low stellar mass galaxies tend to have a larger variety of metallicity slopes. When normalized by the half-mass radius, the stellar metallicity gradients do not show any dependence and the dispersion increases significantly, regardless of the galaxy mass. Galaxies with stellar masses o f around 1010M⊙ show steeper negative metallicity gradients. The stellar metallicity gradients correlate with the half-mass radius. However, the correlation signal is not present when they are normalized by the half-mass radius. Stellar discs with positive age gradients are detected to have negative and positive metallicity gradients, depending on the relative importance of recent star formation activity in the central regions. Conclusions: Our results suggest that inside

  13. Gradient-enhanced FAWSETS perfusion measurements

    Science.gov (United States)

    Marro, Kenneth I.; Lee, Donghoon; Hyyti, Outi M.

    2005-08-01

    This work describes the use of custom-built gradients to enhance skeletal muscle perfusion measurements acquired with a previously described arterial spin labeling technique known as FAWSETS (flow-driven arterial water stimulation with elimination of tissue signal). Custom-built gradients provide active control of the static magnetic field gradient on which FAWSETS relies for labeling. This allows selective, 180° modulations of the phase of the perfusion component of the signal. Phase cycling can then be implemented to eliminate all extraneous components leaving a signal that exclusively reflects capillary-level perfusion. Gradient-enhancement substantially reduces acquisition time and eliminates the need to acquire an ischemic signal to quantify perfusion. This removes critical obstacles to application of FAWSETS in organs other than skeletal muscle and makes the measurements more desirable for clinical environments. The basic physical principles of gradient-enhancement are demonstrated in flow phantom experiments and in vivo utility is demonstrated in rat hind limb during stimulated exercise.

  14. Collective chemotaxis through noisy multicellular gradient sensing

    CERN Document Server

    Varennes, Julien; Mugler, Andrew

    2016-01-01

    Collective cell migration in response to a chemical cue occurs in many biological processes such as morphogenesis and cancer metastasis. Clusters of migratory cells in these systems are capable of responding to gradients of less than 1% difference in chemical concentration across a cell length. Multicellular systems are extremely sensitive to their environment and while the limits to multicellular sensing are becoming known, how this information leads to coherent migration remains poorly understood. We develop a computational model of multicellular sensing and migration in which groups of cells collectively measure noisy chemical gradients. The output of the sensing process is coupled to individual cells polarization to model migratory behavior. Through the use of numerical simulations, we find that larger clusters of cells detect the gradient direction with higher precision and thus achieve stronger polarization bias, but larger clusters also induce more drag on collective motion. The trade-off between these...

  15. Electrical and chemical signals involved in short-term systemic photosynthetic responses of tobacco plants to local burning

    Czech Academy of Sciences Publication Activity Database

    Hlaváčková, V.; Krchňák, P.; Nauš, J.; Novák, Ondřej; Špundová, M.; Strnad, Miroslav

    2006-01-01

    Roč. 225, č. 1 (2006), s. 235-244. ISSN 0032-0935 R&D Projects: GA ČR GA206/05/0894 Institutional research plan: CEZ:AV0Z50380511 Keywords : Abscisic acid * Electrical signals * Gas exchange Subject RIV: CE - Biochemistry Impact factor: 2.963, year: 2006

  16. Profiling Environmental Chemicals for Activity in the Antioxidant Response Element Signaling Pathway Using a High-Throughput Screening Approach

    Science.gov (United States)

    1 ABSTRACT 2 3 BACKGROUND: Oxidative stress has been implicated in the pathogenesis of a variety 4 of diseases ranging from cancer to neurodegeneration, highlighti.ng the need to identify 5 chemicals that can induce this effect. The antioxidant response element (ARE)...

  17. Integrated CMOS photodetectors and signal processing for very low-level chemical sensing with the bioluminescent bioreporter integrated circuit

    Science.gov (United States)

    Bolton, Eric K.; Sayler, Gary S.; Nivens, David E.; Rochelle, James M.; Ripp, Steven; Simpson, Michael L.

    2002-01-01

    We report an integrated CMOS microluminometer optimized for the detection of low-level bioluminescence as part of the bioluminescent bioreporter integrated circuit (BBIC). This microluminometer improves on previous devices through careful management of the sub-femtoampere currents, both signal and leakage, that flow in the front-end processing circuitry. In particular, the photodiode is operated with a reverse bias of only a few mV, requiring special attention to the reset circuitry of the current-to-frequency converter (CFC) that forms the front-end circuit. We report a sub-femtoampere leakage current and a minimum detectable signal (MDS) of 0.15 fA (1510 s integration time) using a room temperature 1.47 mm2 CMOS photodiode. This microluminometer can detect luminescence from as few as 5000 fully induced Pseudomonas fluorescens 5RL bacterial cells. c2002 Elsevier Science B.V. All rights reserved.

  18. Gradient Coils Temperature Controller in a Gradient System for MR Tomography

    Czech Academy of Sciences Publication Activity Database

    Bartušek, Karel; Dokoupil, Zdeněk; Gescheidtová, E.; Smékal, Z.

    Los Alamitos : IEEE Computer Society, 2007, P8:1-4. ISBN 0-7695-2807-4. [ICONS 2007 - International Conference on Systems /2./. Sainte-Luce, Martinique (FR), 22.04.2007-28.04.2007] R&D Projects: GA ČR(CZ) GA102/07/1086 Institutional research plan: CEZ:AV0Z20650511 Keywords : MR tomography * temperature controller * gradients * gradient coils * digital signal processor Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  19. Lipid phosphate phosphatases regulate lysophosphatidic acid production and signaling in platelets: studies using chemical inhibitors of lipid phosphate phosphatase activity.

    Science.gov (United States)

    Smyth, Susan S; Sciorra, Vicki A; Sigal, Yury J; Pamuklar, Zehra; Wang, Zuncai; Xu, Yong; Prestwich, Glenn D; Morris, Andrew J

    2003-10-31

    Blood platelets play an essential role in ischemic heart disease and stroke contributing to acute thrombotic events by release of potent inflammatory agents within the vasculature. Lysophosphatidic acid (LPA) is a bioactive lipid mediator produced by platelets and found in the blood and atherosclerotic plaques. LPA receptors on platelets, leukocytes, endothelial cells, and smooth muscle cells regulate growth, differentiation, survival, motility, and contractile activity. Definition of the opposing pathways of synthesis and degradation that control extracellular LPA levels is critical to understanding how LPA bioactivity is regulated. We show that intact platelets and platelet membranes actively dephosphorylate LPA and identify the major enzyme responsible as lipid phosphate phosphatase 1 (LPP1). Localization of LPP1 to the platelet surface is increased by exposure to LPA. A novel receptor-inactive sn-3-substituted difluoromethylenephosphonate analog of phosphatidic acid that is a potent competitive inhibitor of LPP1 activity potentiates platelet aggregation and shape change responses to LPA and amplifies LPA production by agonist-stimulated platelets. Our results identify LPP1 as a pivotal regulator of LPA signaling in the cardiovascular system. These findings are consistent with genetic and cell biological evidence implicating LPPs as negative regulators of lysophospholipid signaling and suggest that the mechanisms involve both attenuation of lysophospholipid actions at cell surface receptors and opposition of lysophospholipid production. PMID:12909631

  20. Quaternion Gradient and Hessian

    OpenAIRE

    Xu, Dongpo; Mandic, Danilo P.

    2014-01-01

    The optimization of real scalar functions of quaternion variables, such as the mean square error or array output power, underpins many practical applications. Solutions often require the calculation of the gradient and Hessian, however, real functions of quaternion variables are essentially non-analytic. To address this issue, we propose new definitions of quaternion gradient and Hessian, based on the novel generalized HR (GHR) calculus, thus making possible efficient derivation of optimizati...

  1. Gradient Particle Magnetohydrodynamics

    OpenAIRE

    Maron, Jason L.; Howes, Gregory G.

    2001-01-01

    We introduce Gradient Particle Magnetohydrodynamics (GPM), a new Lagrangian method for magnetohydrodynamics based on gradients corrected for the locally disordered particle distribution. The development of a numerical code for MHD simulation using the GPM algorithm is outlined. Validation tests simulating linear and nonlinear sound waves, linear MHD waves, advection of magnetic fields in a magnetized vortex, hydrodynamical shocks, and three-dimensional collapse are presented, demonstrating th...

  2. Comprehensive signal assignment of 13C-labeled lignocellulose using multidimensional solution NMR and 13C chemical shift comparison with solid-state NMR.

    Science.gov (United States)

    Komatsu, Takanori; Kikuchi, Jun

    2013-09-17

    A multidimensional solution NMR method has been developed using various pulse programs including HCCH-COSY and (13)C-HSQC-NOESY for the structural characterization of commercially available (13)C labeled lignocellulose from potatoes (Solanum tuberosum L.), chicory (Cichorium intybus), and corn (Zea mays). This new method allowed for 119 of the signals in the (13)C-HSQC spectrum of lignocelluloses to be assigned and was successfully used to characterize the structures of lignocellulose samples from three plants in terms of their xylan and xyloglucan structures, which are the major hemicelluloses in angiosperm. Furthermore, this new method provided greater insight into fine structures of lignin by providing a high resolution to the aromatic signals of the β-aryl ether and resinol moieties, as well as the diastereomeric signals of the β-aryl ether. Finally, the (13)C chemical shifts assigned in this study were compared with those from solid-state NMR and indicated the presence of heterogeneous dynamics in the polysaccharides where rigid cellulose and mobile hemicelluloses moieties existed together. PMID:24010724

  3. High Gradient Accelerator Research

    Energy Technology Data Exchange (ETDEWEB)

    Temkin, Richard [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Physics. Plasma Science and Fusion Center

    2016-07-12

    The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.

  4. Measurement of gradient magnetic field temporal characteristics

    International Nuclear Information System (INIS)

    We describe a technique of measuring the time dependence and field distortions of magnetic fields due to eddy currents (EC) produced by time-dependent magnetic field gradients. The EC measuring technique makes use of a large volume sample and selective RF excitation pulses and free induction decay (FID) (or a spin or gradient echo) to measure the out-of-phase component of the FID, which is proportional to γδB, i.e. the amount the signal is off resonance. The measuring technique is sensitive, easy to implement and interpret, and used for determining pre-emphasis compensation parameters

  5. Turning-Off Signaling by Siglecs, Selectins, and Galectins: Chemical Inhibition of Glycan-Dependent Interactions in Cancer

    Science.gov (United States)

    Cagnoni, Alejandro J.; Pérez Sáez, Juan M.; Rabinovich, Gabriel A.; Mariño, Karina V.

    2016-01-01

    Aberrant glycosylation, a common feature associated with malignancy, has been implicated in important events during cancer progression. Our understanding of the role of glycans in cancer has grown exponentially in the last few years, concurrent with important advances in glycomics and glycoproteomic technologies, paving the way for the validation of a number of glycan structures as potential glycobiomarkers. However, the molecular bases underlying cancer-associated glycan modifications are still far from understood. Glycans exhibit a natural heterogeneity, crucial for their diverse functional roles as specific carriers of biologically relevant information. This information is decoded by families of proteins named lectins, including sialic acid-binding immunoglobulin (Ig)-like lectins (siglecs), C-type lectin receptors (CLRs), and galectins. Siglecs are primarily expressed on the surface of immune cells and differentially control innate and adaptive immune responses. Among CLRs, selectins are a family of cell adhesion molecules that mediate interactions between cancer cells and platelets, leukocytes, and endothelial cells, thus facilitating tumor cell invasion and metastasis. Galectins, a family of soluble proteins that bind β-galactoside-containing glycans, have been implicated in diverse events associated with cancer biology such as apoptosis, homotypic cell aggregation, angiogenesis, cell migration, and tumor-immune escape. Consequently, individual members of these lectin families have become promising targets for the design of novel anticancer therapies. During the past decade, a number of inhibitors of lectin–glycan interactions have been developed including small-molecule inhibitors, multivalent saccharide ligands, and more recently peptides and peptidomimetics have offered alternatives for tackling tumor progression. In this article, we review the current status of the discovery and development of chemical lectin inhibitors and discuss novel strategies to

  6. Sintered composite gradient tool materials

    Directory of Open Access Journals (Sweden)

    J. Mikuła

    2008-07-01

    Full Text Available Purpose: Development of a new generation of the composite gradient tool materials with the core sintered withthe matrix obtained using the powder metallurgy of the chemical composition corresponding to the HS6-5-2 highspeedsteel reinforced with the WC and TiC type hard carbide phases with the growing portions of these phases inthe outward direction from the core to the surface.Design/methodology/approach: Powder Metallurgy, SEM, X-Ray Microanalysis.Findings: Powder metallurgy processes were used to fabricate the proposed gradient materials, i.e., compacting inthe closed die and sintering. The method of sequential pouring of the successive portions of the powder mixes intothe die was used to ensure a high ductility of the fabricated material core with the HS6-5-2 steel matrix reinforcedwith the hard WC and TiC carbides phases, so that portions of powder with the high percentage of the hard carbidesphases would form the outer layers of the prepreg.Practical implications: Employment of powder metallurgy for fabricating the steel based tool materials givesthe possibility to preserve properties characteristic of the traditional cemented carbides and with the high ductilitycharacteristic of steel, yet better than the traditional sintered high-speed steels obtained with the ASP method.Originality/value: Providing of high properties characteristic of cemented carbides with the high ductilitycharacteristic of steel can be mostly because of the possibility of ensuring the gradients of the chemicalcomposition and properties, cutting simultaneously fabrication costs thanks to savings made on the hard carbidephase, used in the tool surface layer only.

  7. Gradient tabu search.

    Science.gov (United States)

    Stepanenko, Svetlana; Engels, Bernd

    2007-01-30

    This paper presents a modification of the tabu search called gradient tabu search (GTS). It uses analytical gradients for a fast minimization to the next local minimum and analytical diagonal elements of the Hessian to escape local minima. For an efficient blocking of already visited areas tabu regions and tabu directions are introduced into the tabu list (TL). Trials with various well-known test functions indicate that the GTS is a very promising approach to determine local and global minima of differentiable functions. Possible application areas could be optimization routines for force field parameters or conformational searches for large molecules. PMID:17186482

  8. High gradient superconducting quadrupoles

    International Nuclear Information System (INIS)

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed

  9. A substrate independent approach for generation of surface gradients

    International Nuclear Information System (INIS)

    Recently, surface gradients have attracted significant interest for various research and technological applications. In this paper, we report a facile and versatile method for generating surface gradients of immobilized nanoparticles, nanotopography and ligands that is independent from the substrate material. The method consists of first depositing a functional polymer layer on a substrate and subsequent time controlled immersion of this functionalized substrate in solution gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) or poly (styrenesulfonate) (PSS). Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and morphological analysis by Atomic Force Microscopy (AFM) show that the density of nanoparticles and the concentration of PSS across the surface increases in a gradient manner. As expected, time of immersion determines the concentration of surface bound species. We also demonstrate the generation of surface gradients of pure nanotopography. This is achieved by depositing a 5 nm thick plasma polymer layer on top of the number density gradient of nanoparticles to achieve a homogeneous surface chemistry. The surface independent approach for generation of surface gradients presented in this paper may open opportunities for a wider use of surface gradient in research and in various technologies. - Highlights: ► We present a substrate independent approach for generation of surface gradients. ► We demonstrate well-defined density gradients of gold and silver nanoparticles. ► We provide an example of pure surface nanotopography gradients. ► We demonstrate concentration gradients of bound ligands

  10. A substrate independent approach for generation of surface gradients

    Energy Technology Data Exchange (ETDEWEB)

    Goreham, Renee V. [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia); Mierczynska, Agnieszka; Pierce, Madelene [Ian Wark Research Institute, University of South Australia, Mawson Lakes 5095 (Australia); Short, Robert D.; Taheri, Shima; Bachhuka, Akash; Cavallaro, Alex; Smith, Louise E. [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia); Vasilev, Krasimir, E-mail: krasimir.vasilev@unisa.edu.au [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia)

    2013-01-01

    Recently, surface gradients have attracted significant interest for various research and technological applications. In this paper, we report a facile and versatile method for generating surface gradients of immobilized nanoparticles, nanotopography and ligands that is independent from the substrate material. The method consists of first depositing a functional polymer layer on a substrate and subsequent time controlled immersion of this functionalized substrate in solution gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) or poly (styrenesulfonate) (PSS). Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and morphological analysis by Atomic Force Microscopy (AFM) show that the density of nanoparticles and the concentration of PSS across the surface increases in a gradient manner. As expected, time of immersion determines the concentration of surface bound species. We also demonstrate the generation of surface gradients of pure nanotopography. This is achieved by depositing a 5 nm thick plasma polymer layer on top of the number density gradient of nanoparticles to achieve a homogeneous surface chemistry. The surface independent approach for generation of surface gradients presented in this paper may open opportunities for a wider use of surface gradient in research and in various technologies. - Highlights: ► We present a substrate independent approach for generation of surface gradients. ► We demonstrate well-defined density gradients of gold and silver nanoparticles. ► We provide an example of pure surface nanotopography gradients. ► We demonstrate concentration gradients of bound ligands.

  11. Bi-layer functionally gradient thick film semiconducting methane sensors

    Indian Academy of Sciences (India)

    A Banerjee; A K Haldar; J Mondal; A Sen; H S Maiti

    2002-11-01

    Gas sensors based on metal oxide semiconductors like tin dioxide are widely used for the detection of toxic and combustible gases like carbon monoxide, methane and LPG. One of the problems of such sensors is their lack of sensitivity, which to some extent, can be circumvented by using different catalysts. However, highly reactive volatile organic compounds (VOC) coming from different industrial and domestic products (e.g. paints, lacquers, varnishes etc) can play havoc on such sensors and can give rise to false alarms. Any attempt to adsorb such VOCs (e.g. by using activated charcoal) results in sorption of the detecting gases (e.g. methane) too. To get round the problem, bi-layer sensors have been developed. Such tin oxide based functionally gradient bi-layer sensors have different compositions at the top and bottom layers. Here, instead of adsorbing the VOCs, they are allowed to interact and are consumed on the top layer of the sensors and a combustible gas like methane being less reactive, penetrates the top layer and interacts with the bottom layer. By modifying the chemical compositions of the top and bottom layers and by designing the electrode-lead wire arrangement properly, the top layer can be kept electrically shunted from the bottom layer and the electrical signal generated at the bottom layer from the combustible gas is collected. Such functionally gradient sensors, being very reliable, can find applications in domestic, industrial and strategic sectors.

  12. Manipulating the Gradient

    Science.gov (United States)

    Gaze, Eric C.

    2005-01-01

    We introduce a cooperative learning, group lab for a Calculus III course to facilitate comprehension of the gradient vector and directional derivative concepts. The lab is a hands-on experience allowing students to manipulate a tangent plane and empirically measure the effect of partial derivatives on the direction of optimal ascent. (Contains 7…

  13. The biophysical model for accuracy of cellular sensing spatial gradients of multiple chemoattractants

    International Nuclear Information System (INIS)

    Spatial gradients of surrounding chemoattractants are the key factors in determining the directionality of eukaryotic cell movement. Thus, it is important for cells to accurately measure the spatial gradients of surrounding chemoattractants. Here, we study the precision of sensing the spatial gradients of multiple chemoattractants using cooperative receptor clusters. Cooperative receptors on cells are modeled as an Ising chain of Monod–Wyman–Changeux clusters subject to multiple chemical-gradient fields to study the physical limits of multiple chemoattractants spatial gradients sensing. We found that eukaryotic cells cannot sense each chemoattractant gradient individually. Instead, cells can only sense a weighted sum of surrounding chemical gradients. Moreover, the precision of sensing one chemical gradient is signicantly affected by coexisting chemoattractant concentrations. These findings can provide a further insight into the role of chemoattractants in immune response and help develop novel treatments for inflammatory diseases. (paper)

  14. Aerodynamic gradient measurements of the NH3-HNO3-NH4NO3 triad using a wet chemical instrument: an analysis of precision requirements and flux errors

    OpenAIRE

    V. Wolff; Trebs, I.; Ammann, C.; Meixner, F. X.

    2010-01-01

    The aerodynamic gradient method is widely used for flux measurements of ammonia, nitric acid, particulate ammonium nitrate (the NH3-HNO3-NH4NO3 triad) and other water-soluble reactive trace compounds. The surface exchange flux is derived from a measured concentration difference and micrometeorological quantities (turbulent exchange coefficient). The significance of the measured concentration difference is crucial for the significant determination of surface exchange fluxes. Additionally,...

  15. Metallicity Gradients in Disks: Do Galaxies Form Inside-Out?

    CERN Document Server

    Pilkington, K; Gibson, B K; Calura, F; Michel-Dansac, L; Thacker, R J; Molla, M; Matteucci, F; Rahimi, A; Kawata, D; Kobayashi, C; Brook, C B; Stinson, G S; Couchman, H M P; Bailin, J; Wadsley, J

    2012-01-01

    We examine radial and vertical metallicity gradients using a suite of disk galaxy simulations, supplemented with two classic chemical evolution approaches. We determine the rate of change of gradient and reconcile differences between extant models and observations within the `inside-out' disk growth paradigm. A sample of 25 disks is used, consisting of 19 from our RaDES (Ramses Disk Environment Study) sample, realised with the adaptive mesh refinement code RAMSES. Four disks are selected from the MUGS (McMaster Unbiased Galaxy Simulations) sample, generated with the smoothed particle hydrodynamics (SPH) code GASOLINE, alongside disks from Rahimi et al. (GCD+) and Kobayashi & Nakasato (GRAPE-SPH). Two chemical evolution models of inside-out disk growth were employed to contrast the temporal evolution of their radial gradients with those of the simulations. We find that systematic differences exist between the predicted evolution of radial abundance gradients in the RaDES and chemical evolution models, comp...

  16. Online Gradient Boosting

    OpenAIRE

    Beygelzimer, Alina; Hazan, Elad; Kale, Satyen; Luo, Haipeng

    2015-01-01

    We extend the theory of boosting for regression problems to the online learning setting. Generalizing from the batch setting for boosting, the notion of a weak learning algorithm is modeled as an online learning algorithm with linear loss functions that competes with a base class of regression functions, while a strong learning algorithm is an online learning algorithm with convex loss functions that competes with a larger class of regression functions. Our main result is an online gradient b...

  17. Gradient structures in hardmetals

    International Nuclear Information System (INIS)

    Functionally graded materials enable combinations of properties like hardness and toughness that can not be achieved with homogeneous materials. The formation of gradients in tungsten carbides correlates with the migration of binder which is caused by differences in the composition of the green body, gas-phase treatment during sintering or the mean particle size and particle-size distribution of the hard phase. In order to examine the gradient formation fracture bars were made of differently fine-grained WC powders and variable additions of Co and carbon black. Beside homogeneous samples two-layer samples were manufactured by step-wise pressing of powders with different composition and/or grain size. The densification behavior of the green bodies and the magnetic and mechanical properties of the sintered compacts were measured. On two-layer samples with full density the concentration profiles of Co, C and W was determined parallel to the pressing direction over the entire sample height (≤ 10 mm) by ESMA. Additionally, hardness and fracture toughness were measured along this line. Differences in cobalt contents are rapidly homogenized in liquid-phase sintering. But large Co gradients can be generated by differences in particle sizes of the hard phase, the non-metal content (carbon, oxygen) and impurities in the ppm range (influence of the wetting and solubility conditions). After sintering the binder content of the finer grained layer is generally higher than in the coarser layer independent of the starting composition. In two-layer samples Co gradients up to 10 mm in thickness and hardness differences to 500 units (HV10) could be produced. (author)

  18. Fixed field alternating gradient

    OpenAIRE

    Machida, Shinji

    2013-01-01

    The concept of a fixed field alternating gradient (FFAG) accelerator was invented in the 1950s. Although many studies were carried out up to the late 1960s, there has been relatively little progress until recently, when it received widespread attention as a type of accelerator suitable for very fast acceleration and for generating high-power beams. In this paper, we describe the principles and design procedure of a FFAG accelerator.

  19. Energy in density gradient

    OpenAIRE

    Vranjes, J.; Kono, M

    2015-01-01

    Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindric configuration. This is of practical importance for drift wave instability in various plasmas, and in partic...

  20. Conjugate gradient method

    Czech Academy of Sciences Publication Activity Database

    Segeth, Karel

    Liberec : Technická univerzita v Liberci, 2006, s. 335-341. ISBN 80-7372-055-8. [International Conference Presentation of Mathematics ICPM ´05. Liberec (CZ), 20.09.2005-23.09.2005] R&D Projects: GA ČR(CZ) GA201/04/1503 Institutional research plan: CEZ:AV0Z10190503 Keywords : linear algebraic system * conjugate gradient method * preconditioning Subject RIV: BA - General Mathematics

  1. Chemical signals of bumble bees

    Czech Academy of Sciences Publication Activity Database

    Urbanová, Klára; Valterová, Irena

    Praha : UOCHB AVČR, 1998. s. 17-18. ISBN 80-902130-8-1. [Conference on Organic Chemistry and Biochemistry of Young Scientists /10./. 15.06.1998-20.06.1998, Liblice] Keywords : biochemistry * organic chemistry Subject RIV: CC - Organic Chemistry

  2. Substrate-Bound Protein Gradients to Study Haptotaxis

    Directory of Open Access Journals (Sweden)

    Sebastien G. Ricoult

    2015-03-01

    Full Text Available Cells navigate in response to inhomogeneous distributions of extracellular guidance cues. The cellular and molecular mechanisms underlying migration in response to gradients of chemical cues have been investigated for over a century. Following the introduction of micropipettes and more recently microfluidics for gradient generation, much attention and effort was devoted to study cellular chemotaxis, which is defined as guidance by gradients of chemical cues in solution. Haptotaxis, directional migration in response to gradients of substrate-bound cues, has received comparatively less attention; however it is increasingly clear that in vivo many physiologically relevant guidance proteins – including many secreted cues – are bound to cellular surfaces or incorporated into extracellular matrix and likely function via a haptotactic mechanism. Here, we review the history of haptotaxis. We examine the importance of the reference surface, the surface in contact with the cell that is not covered by the cue, which forms a gradient opposing the gradient of the protein cue and must be considered in experimental designs and interpretation of results. We review and compare microfluidics, contact-printing, light patterning and 3D fabrication to pattern substrate-bound protein gradients in vitro, and focus on their application to study axon guidance. The range of methods to create substrate-bound gradients discussed herein make possible systematic analyses of haptotactic mechanisms. Furthermore, understanding the fundamental mechanisms underlying cell motility will inform bioengineering approaches to program cell navigation and recover lost function.

  3. Generalized quasi Yamabe gradient solitons

    OpenAIRE

    Neto, Benedito Leandro; de Oliveira, Hudson Pina

    2016-01-01

    We prove that a nontrivial complete generalized quasi Yamabe gradient soliton (M; g) must be a quasi Yamabe gradient soliton on each connected component of M and that a nontrivial complete locally conformally at generalized quasi Yamabe gradient soliton has a special warped product structure.

  4. Chemical shift MR imaging of the skin

    International Nuclear Information System (INIS)

    MR imaging with conventional spin-echo pulse sequences has not found wide application in the evaluation of skin pathology. This paper reports that this study was designed to determine the value of chemical shift imaging (CSI) compared with conventional pulse sequences for the noninvasive evaluation of connective tissue and neoplastic disease of the skin and underlying fascia. The studies were acquired in patients and volunteers on a whole-body system at 1.5 T and small surface coils. Comparisons were made between T1- and T2-weighted gradient-echo, spin-echo, and hybrid lipid and water-suppressed CSI series (Chopper-Dixon combined with frequency-selective pulse). CSI improves detail in the hypodermis by eliminating unwanted (lipid) signal and chemical shift misregistration artifact. The detail of water-based signal is improved in the deeper layers of the skin by improved tissue contrast and elimination of the disturbing adjacent dominant fat-based signal. MR imaging has the potential to provide information that can complement skin biopsy. A more optimal choice of pulse sequences can improve the sensitivity of MR imaging to water-based pathology and allow noninvasive visualization of deep layers. The CSI sequences may be useful in the evaluation of infiltrative and neoplastic disease of the skin, particularly as they are adapted into microimaging methods with local gradient coils

  5. Nonlinear Conjugate Gradient Methods

    Czech Academy of Sciences Publication Activity Database

    Lukšan, Ladislav; Vlček, Jan

    Praha: Matematický ústav AV ČR, v.v.i, 2015 - (Chleboun, J.; Přikryl, P.; Segeth, K.; Šístek, J.; Vejchodský, T.), s. 130-135 ISBN 978-80-85823-64-6. [Programs and Algorithms of Numerical Mathematics /17./. Dolní Maxov (CZ), 08.06.2014-13.06.2014] Institutional support: RVO:67985807 Keywords : minimization * nonlinear conjugate gradient methods * comparison of methods * efficiency of methods Subject RIV: BA - General Mathematics http://dml.cz/handle/10338.dmlcz/702674

  6. Signaling and sensory adaptation in Escherichia coli chemoreceptors: 2015 update.

    Science.gov (United States)

    Parkinson, John S; Hazelbauer, Gerald L; Falke, Joseph J

    2015-05-01

    Motile Escherichia coli cells track gradients of attractant and repellent chemicals in their environment with transmembrane chemoreceptor proteins. These receptors operate in cooperative arrays to produce large changes in the activity of a signaling kinase, CheA, in response to small changes in chemoeffector concentration. Recent research has provided a much deeper understanding of the structure and function of core receptor signaling complexes and the architecture of higher-order receptor arrays, which, in turn, has led to new insights into the molecular signaling mechanisms of chemoreceptor networks. Current evidence supports a new view of receptor signaling in which stimulus information travels within receptor molecules through shifts in the dynamic properties of adjoining structural elements rather than through a few discrete conformational states. PMID:25834953

  7. Formation of actin networks in microfluidic concentration gradients

    Science.gov (United States)

    Strelnikova, Natalja; Herren, Florian; Schoenenberger, Cora-Ann; Pfohl, Thomas

    2016-05-01

    The physical properties of cytoskeletal networks are contributors in a number of mechanical responses of cells including cellular deformation and locomotion, and are crucial for the proper action of living cells. Local chemical gradients modulate cytoskeletal functionality including the interactions of the cytoskeleton with other cellular components. Actin is a major constituent of the cytoskeleton. Introducing a microfluidic-based platform, we explored the impact of concentration gradients on the formation and structural properties of actin networks. Microfluidics-controlled flow-free steady state experimental conditions allow for the generation of chemical gradients of different profiles, such as linear or step-like. We discovered specific features of actin networks emerging in defined gradients. In particular, we analyzed the effects of spatial conditions on network properties, bending rigidities of network links, and the network elasticity.

  8. Dual-rail optical gradient echo memory

    CERN Document Server

    Higginbottom, Daniel B; Campbell, Geoff T; Hosseini, Mahdi; Cao, Ming Tao; Sparkes, Ben M; Bernu, Julian; Robins, Nick P; Lam, Ping Koy; Buchler, Ben C

    2016-01-01

    We introduce a scheme for the parallel storage of frequency separated signals in an optical memory and demonstrate that this dual-rail storage is a suitable memory for high fidelity frequency qubits. The two signals are stored simultaneously in the Zeeman-split Raman absorption lines of a cold atom ensemble using gradient echo memory techniques. Analysis of the split-Zeeman storage shows that the memory can be configured to preserve the relative amplitude and phase of the frequency separated signals. In an experimental demonstration dual-frequency pulses are recalled with 35% efficiency, 82% interference fringe visibility, and 6 degrees phase stability. The fidelity of the frequency-qubit memory is limited by frequency-dependent polarisation rotation and ambient magnetic field fluctuations, our analysis describes how these can be addressed in an alternative configuration.

  9. Diphenylarsinic acid, a chemical warfare-related neurotoxicant, promotes liver carcinogenesis via activation of aryl hydrocarbon receptor signaling and consequent induction of oxidative DAN damage in rats

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Min; Yamada, Takanori; Yamano, Shotaro; Kato, Minoru; Kakehashi, Anna; Fujioka, Masaki; Tago, Yoshiyuki; Kitano, Mistuaki; Wanibuchi, Hideki, E-mail: wani@med.osaka-cu.ac.jp

    2013-11-15

    Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. Inorganic arsenic is carcinogenic in humans and its organic arsenic metabolites are carcinogenic in animal studies, raising serious concerns about the carcinogenicity of DPAA. However, the carcinogenic potential of DPAA has not yet been evaluated. In the present study we found that DPAA significantly enhanced the development of diethylnitrosamine-induced preneoplastic lesions in the liver in a medium-term rat liver carcinogenesis assay. Evaluation of the expression of cytochrome P450 (CYP) enzymes in the liver revealed that DPAA induced the expression of CYP1B1, but not any other CYP1, CYP2, or CYP3 enzymes, suggesting that CYP1B1 might be the enzyme responsible for the metabolic activation of DPAA. We also found increased oxidative DNA damage, possibly due to elevated CYP1B1 expression. Induction of CYP1B1 has generally been linked with the activation of AhR, and we found that DPAA activates the aryl hydrocarbon receptor (AhR). Importantly, the promotion effect of DPAA was observed only at a dose that activated the AhR, suggesting that activation of AhR and consequent induction of AhR target genes and oxidative DNA damage plays a vital role in the promotion effects of DPAA. The present study provides, for the first time, evidence regarding the carcinogenicity of DPAA and indicates the necessity of comprehensive evaluation of its carcinogenic potential using long-term carcinogenicity studies. - Highlights: • DPAA, an environmental neurotoxicant, promotes liver carcinogenesis in rats. • DPAA is an activator of AhR signaling pathway. • DPAA promoted oxidative DNA damage in rat livers. • AhR target gene CYP 1B1 might be involved in the metabolism of DPAA.

  10. Diphenylarsinic acid, a chemical warfare-related neurotoxicant, promotes liver carcinogenesis via activation of aryl hydrocarbon receptor signaling and consequent induction of oxidative DAN damage in rats

    International Nuclear Information System (INIS)

    Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. Inorganic arsenic is carcinogenic in humans and its organic arsenic metabolites are carcinogenic in animal studies, raising serious concerns about the carcinogenicity of DPAA. However, the carcinogenic potential of DPAA has not yet been evaluated. In the present study we found that DPAA significantly enhanced the development of diethylnitrosamine-induced preneoplastic lesions in the liver in a medium-term rat liver carcinogenesis assay. Evaluation of the expression of cytochrome P450 (CYP) enzymes in the liver revealed that DPAA induced the expression of CYP1B1, but not any other CYP1, CYP2, or CYP3 enzymes, suggesting that CYP1B1 might be the enzyme responsible for the metabolic activation of DPAA. We also found increased oxidative DNA damage, possibly due to elevated CYP1B1 expression. Induction of CYP1B1 has generally been linked with the activation of AhR, and we found that DPAA activates the aryl hydrocarbon receptor (AhR). Importantly, the promotion effect of DPAA was observed only at a dose that activated the AhR, suggesting that activation of AhR and consequent induction of AhR target genes and oxidative DNA damage plays a vital role in the promotion effects of DPAA. The present study provides, for the first time, evidence regarding the carcinogenicity of DPAA and indicates the necessity of comprehensive evaluation of its carcinogenic potential using long-term carcinogenicity studies. - Highlights: • DPAA, an environmental neurotoxicant, promotes liver carcinogenesis in rats. • DPAA is an activator of AhR signaling pathway. • DPAA promoted oxidative DNA damage in rat livers. • AhR target gene CYP 1B1 might be involved in the metabolism of DPAA

  11. Rainbow refractometry on particles with radial refractive index gradients

    Energy Technology Data Exchange (ETDEWEB)

    Saengkaew, Sawitree [CNRS/Universite et INSA de Rouen, UMR 6614/CORIA, BP12, 76 800, Saint Etienne du Rouvray CEDEX (France); Chulalongkorn University, Center of Excellence in Particle Technology, Faculty of Engineering, Bangkok (Thailand); Charinpanitkul, Tawatchai; Vanisri, Hathaichanok; Tanthapanichakoon, Wiwut [Chulalongkorn University, Center of Excellence in Particle Technology, Faculty of Engineering, Bangkok (Thailand); Biscos, Yves; Garcia, Nicolas; Lavergne, Gerard [ONERA/DMAE, Toulouse (France); Mees, Loic; Gouesbet, Gerard; Grehan, Gerard [CNRS/Universite et INSA de Rouen, UMR 6614/CORIA, BP12, 76 800, Saint Etienne du Rouvray CEDEX (France)

    2007-10-15

    The rainbow refractrometry, under its different configurations (classical and global), is an attractive technique to extract information from droplets in evaporation such as diameter and temperature. Recently a new processing strategy has been developed which increases dramatically the size and refractive index measurements accuracy for homogeneous droplets. Nevertheless, for mono component as well as for multicomponent droplets, the presence of temperature and/or of concentration gradients induce the presence of a gradient of refractive index which affects the interpretation of the recorded signals. In this publication, the effect of radial gradient on rainbow measurements with a high accuracy never reached previously is quantified. (orig.)

  12. Generalized conjugate gradient squared

    Energy Technology Data Exchange (ETDEWEB)

    Fokkema, D.R.; Sleijpen, G.L.G. [Utrecht Univ. (Netherlands)

    1994-12-31

    In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.

  13. Automated apparatus for producing gradient gels

    Science.gov (United States)

    Anderson, N.L.

    1983-11-10

    Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

  14. Gradient sensing in defined chemotactic fields.

    Science.gov (United States)

    Skoge, Monica; Adler, Micha; Groisman, Alex; Levine, Herbert; Loomis, William F; Rappel, Wouter-Jan

    2010-11-01

    Cells respond to a variety of secreted molecules by modifying their physiology, growth patterns, and behavior. Motile bacteria and eukaryotic cells can sense extracellular chemoattractants and chemorepellents and alter their movement. In this way fibroblasts and leukocytes can find their way to sites of injury and cancer cells can home in on sites that are releasing growth factors. Social amoebae such as Dictyostelium are chemotactic to cAMP which they secrete several hours after they have initiated development. These eukaryotic cells are known to be able to sense extremely shallow gradients but the processes underlying their exquisite sensitivity are still largely unknown. In this study we determine the responses of developed cells of Dictyostelium discoideum to stable linear gradients of cAMP of varying steepness generated in 2 μm deep gradient chambers of microfluidic devices. The gradients are generated by molecular diffusion between two 80 μm deep flow-through channels, one of which is perfused with a solution of cAMP and the other with buffer, serving as continuously replenished source and sink. These low ceiling gradient chambers constrained the cells in the vertical dimension, facilitating confocal imaging, such that subcellular localization of fluorescently tagged proteins could be followed for up to 30 min without noticeable phototoxicity. Chemotactic cells enter these low ceiling chambers by flattening and elongating and then move almost as rapidly as unconstrained cells. By following the localization of activated Ras (RasGTP) using a Ras Binding Domain fused to Green Fluorescent Protein (RBD-GFP), we observed the rapid appearance of membrane associated patches at the tips of pseudopods. These patches remained associated with pseudopods while they continued to extend but were rapidly disassembled when pseudopods stalled and the cell moved past them. Likewise, fluorescence associated with localized RasGTP rapidly disappeared when the gradient was turned

  15. Rigidity of gradient Ricci Solitons

    OpenAIRE

    Petersen, Peter; Wylie, William

    2007-01-01

    We define a gradient Ricci soliton to be rigid if it is a flat bundle $% N\\times_{\\Gamma}\\mathbb{R}^{k}$ where $N$ is Einstein. It is known that not all gradient solitons are rigid. Here we offer several natural conditions on the curvature that characterize rigid gradient solitons. Other related results on rigidity of Ricci solitons are also explained in the last section.

  16. Gradient boosting machines, a tutorial.

    Science.gov (United States)

    Natekin, Alexey; Knoll, Alois

    2013-01-01

    Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods with a strong focus on machine learning aspects of modeling. A theoretical information is complemented with descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. Three practical examples of gradient boosting applications are presented and comprehensively analyzed. PMID:24409142

  17. Gradient Boosting Machines, A Tutorial

    Directory of Open Access Journals (Sweden)

    Alexey eNatekin

    2013-12-01

    Full Text Available Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods. A theoretical information is complemented with many descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. A set of practical examples of gradient boosting applications are presented and comprehensively analyzed.

  18. Galactic abundance gradients from Cepheids : On the iron abundance gradient around 10-12 kpc

    OpenAIRE

    Lemasle, B.; Francois, P.; Piersimoni, A.; Pedicelli, S.; Bono, G.; Laney, C. D.; Primas, F.; Romaniello, M.

    2008-01-01

    Context: Classical Cepheids can be adopted to trace the chemical evolution of the Galactic disk since their distances can be estimated with very high accuracy. Aims: Homogeneous iron abundance measurements for 33 Galactic Cepheids located in the outer disk together with accurate distance determinations based on near-infrared photometry are adopted to constrain the Galactic iron gradient beyond 10 kpc. Methods: Iron abundances were determined using high resolution Cepheid spectra collected wit...

  19. Denaturing gradient gel electrophoresis

    International Nuclear Information System (INIS)

    It is worthwhile considering that only some 30 species make up the bulk of the bacterial population in human faeces at any one time based on the classical cultivation-based approach. The situation in the rumen is similar. Thus, it is practical to focus on specific groups of interest within the complex community. These may be the predominant or the most active species, specific physiological groups or readily identifiable (genetic) clusters of phylogenetically related organisms. Several 16S rDNA fingerprinting techniques can be invaluable for selecting and monitoring sequences or phylogenetic groups of interest and are described below. Over the past few decades, considerable attention was focussed on the identification of pure cultures of microbes on the basis of genetic polymorphisms of DNA encoding rRNA such as ribotyping, amplified fragment length polymorphism and randomly amplified polymorphic DNA. However, many of these methods require prior cultivation and are less suitable for use in analysis of complex mixed populations although important in describing cultivated microbial diversity in molecular terms. Much less attention was given to molecular characterization of complex communities. In particular, research into diversity and community structure over time has been revolutionized by the advent of molecular fingerprinting techniques for complex communities. Denaturing or temperature gradient gel electrophoresis (DGGE/TGGE) methods have been successfully applied to the analysis of human, pig, cattle, dog and rodent intestinal populations

  20. Direct visualization of chemical and thermo-remanent magnetization of pseudo-single-domain magnetite grains and the implications for reliable paleomagentic signal acquisition

    Science.gov (United States)

    Almeida, T.; Muxworthy, A. R.; Kasama, T.; Williams, W.; Kovács, A.; Dunin-Borkowski, R.; Hansen, T. W.

    2015-12-01

    In order to reliably interpret paleomagnetic measurements, the mechanisms of chemical remanent magnetization (CRM) and thermoremanent magnetization (TRM) must be fully understood. Currently, most models of CRM and TRM processes only exist for the smallest, uniformly magnetized grains, termed single domain (SD). However, the magnetic signal from rocks is often dominated by slightly larger grains containing non-uniform magnetization states, termed pseudo-SD (PSD) grains. Magnetite (Fe3O4) is the most magnetic naturally occurring mineral on Earth, carrying the dominant magnetic signature in rocks and providing a critical tool in paleomagnetism. The oxidation of Fe3O4 to other iron oxides, such as maghemite (γ-Fe2O3) and hematite (α-Fe2O3), is of particular interest as it influences the preservation of remanence of the Earth's magnetic field by Fe3O4. Further, TRM in Fe3O4 grains is acquired in the direction of the ambient geomagnetic field as they cool below their Curie temperature (TC) of ~ 580 ˚C. The latest transmission electron microscopy (TEM) techniques like electron holography and environmental TEM (ETEM) allows for the imaging of magnetization in nano-scale minerals during in situ heating under vacuum and controlled atmospheres. In the present study, synthetic Fe3O4 particles in the PSD size range (CRM was visualized using electron holography, in the form of reconstructed magnetic induction maps, where the oxidized grains exhibited a loss of overall remanence and change in remanent direction. The thermomagnetic behavior of Fe3O4 particles in the PSD size range is also investigated using off-axis electron holography. Magnetic induction maps, which are recorded during in situ heating up to above the TC, reveal the PSD nature of several Fe3O4 grains by visualizing their vortex domain states. The vortex states in small Fe3O4 grains (Fig. 1a & b) are shown to rotate or collapse into a single-domain state close to its unblocking temperature (Fig. 1c), rather than

  1. Electric field gradients in metals

    International Nuclear Information System (INIS)

    A review of the recent works on electric field gradient in metals is given. The main emphasis is put on the temperature dependence of the electric field gradient in nonmagnetic metals. Some methods of investigation of this effect using nuclear probes are described. One of them is nuclear accoustic resonance method. (S.B.)

  2. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...

  3. Effect of Crustal Density Structures on GOCE Gravity Gradient Observables

    Directory of Open Access Journals (Sweden)

    Robert Tenzer and Pavel Novák

    2013-01-01

    Full Text Available We investigate the gravity gradient components corrected for major known anomalous density structures within the _ crust. Heterogeneous mantle density structures are disregarded. The gravimetric forward modeling technique is utilized to compute the gravity gradients based on methods for a spherical harmonic analysis and synthesis of a gravity field. The _ gravity gradient components are generated using the global geopotential model GOCO-03s. The topographic and stripping gravity corrections due to the density contrasts of the ocean and ice are computed from the global topographic/bathymetric model DTM2006.0 (which also includes the ice-thickness dataset. The discrete data of sediments and crust layers taken from the CRUST2.0 global crustal model are then used to apply the additional stripping corrections for sediments and remaining anomalous crustal density structures. All computations are realized globally on a one arc-deg geographical grid at a mean satellite elevation of 255 km. The global map of the consolidated crust-stripped gravity gradients reveals distinctive features which are attributed to global tectonics, lithospheric plate configuration, lithosphere structure and mantle dynamics (e.g., glacial isostatic adjustment, mantle convection. The Moho signature, which is the most pronounced signal in these refined gravity gradients, is superimposed over a weaker gravity signal of the lithospheric mantle. An interpretational quality of the computed (refined gravity gradient components is mainly limited by a low accuracy and resolution of the CRUST2.0 sediment and crustal layer data and unmodeled mantle structures.

  4. Extracellular interactions and ligand degradation shape the nodal morphogen gradient

    Science.gov (United States)

    Wang, Yin; Wang, Xi; Wohland, Thorsten; Sampath, Karuna

    2016-01-01

    The correct distribution and activity of secreted signaling proteins called morphogens is required for many developmental processes. Nodal morphogens play critical roles in embryonic axis formation in many organisms. Models proposed to generate the Nodal gradient include diffusivity, ligand processing, and a temporal activation window. But how the Nodal morphogen gradient forms in vivo remains unclear. Here, we have measured in vivo for the first time, the binding affinity of Nodal ligands to their major cell surface receptor, Acvr2b, and to the Nodal inhibitor, Lefty, by fluorescence cross-correlation spectroscopy. We examined the diffusion coefficient of Nodal ligands and Lefty inhibitors in live zebrafish embryos by fluorescence correlation spectroscopy. We also investigated the contribution of ligand degradation to the Nodal gradient. We show that ligand clearance via degradation shapes the Nodal gradient and correlates with its signaling range. By computational simulations of gradient formation, we demonstrate that diffusivity, extra-cellular interactions, and selective ligand destruction collectively shape the Nodal morphogen gradient. DOI: http://dx.doi.org/10.7554/eLife.13879.001 PMID:27101364

  5. Current progress in eco-physiology of root-sourced chemical signal in plant under drought stress%干旱胁迫下植物根源化学信号研究进展

    Institute of Scientific and Technical Information of China (English)

    李冀南; 李朴芳; 孔海燕; 熊俊兰; 王绍明; 熊友才

    2011-01-01

    土壤干旱胁迫诱导植物根系产生根源化学信号,经运输系统长距离传输到地上部分,降低气孔导度,抑制蒸腾作用,从而提高植物的水分利用效率.根源化学信号包括脱落酸(ABA)、细胞分裂素(CTK)、生长素、木质部pH 值和钙离子(Ca2+ )等,其中以ABA 为主的植物根源信号通路研究得最为广泛和深入.总结了几种主要的化学根源信号物质的基本性质、主要功能和调节机制,重点对这些信号参与气孔行为、差别基因表达和生长发育方面的研究进展进行了综述.由于干旱条件下植物根源信号反应涉及到从分子到群体的一系列复杂过程,各种信号的生理效应呈现交互作用、耦合发生的特点,今后的热点领域将集中在研究交互网络中合成的的关键物质和揭示这些物质在分子及生理水平上的作用机理上.根源化学信号研究正朝向"以分子和生理研究为基础、不同尺度的结构和功能耦合"的方向发展.%Since Blackman and Davies found root-sourced chemical signals formed when soil was drying, many subsequent experiments have elucidated how root-shoot communication might operate. Chemical root-sourced signals are transmitted long-distance to aboveground parts via the transpiration stream, lowering the stomatal conductance, and inhibiting the transpiration rate so as to improve the water use efficiency of plants. It has been shown that the chemical signals act as an "early-warning" response to soil drying in plants. These root-sourced chemical signals include abscisic acid (ABA) ,cytokinins (CTK) , auxin, xylem pH , Ca2+ , of which the ABA-based root signal pathway has been the most extensively and thoroughly studied in plants. This paper summarizes the basic properties, main functions and regulatory mechanisms of several major root-sourced chemical agents. Most content is focused on current research progress on stomatal behavior regulation, differential gene

  6. Current progress in eco-physiology of root-sourced chemical signal in plant under drought stress%干旱胁迫下植物根源化学信号研究进展

    Institute of Scientific and Technical Information of China (English)

    李冀南; 李朴芳; 孔海燕; 熊俊兰; 王绍明; 熊友才

    2011-01-01

    土壤干旱胁迫诱导植物根系产生根源化学信号,经运输系统长距离传输到地上部分,降低气孔导度,抑制蒸腾作用,从而提高植物的水分利用效率.根源化学信号包括脱落酸(ABA)、细胞分裂素(CTK)、生长素、木质部pH 值和钙离子(Ca2+ )等,其中以ABA 为主的植物根源信号通路研究得最为广泛和深入.总结了几种主要的化学根源信号物质的基本性质、主要功能和调节机制,重点对这些信号参与气孔行为、差别基因表达和生长发育方面的研究进展进行了综述.由于干旱条件下植物根源信号反应涉及到从分子到群体的一系列复杂过程,各种信号的生理效应呈现交互作用、耦合发生的特点,今后的热点领域将集中在研究交互网络中合成的的关键物质和揭示这些物质在分子及生理水平上的作用机理上.根源化学信号研究正朝向"以分子和生理研究为基础、不同尺度的结构和功能耦合"的方向发展.%Since Blackman and Davies found root-sourced chemical signals formed when soil was drying, many subsequent experiments have elucidated how root-shoot communication might operate. Chemical root-sourced signals are transmitted long-distance to aboveground parts via the transpiration stream, lowering the stomatal conductance, and inhibiting the transpiration rate so as to improve the water use efficiency of plants. It has been shown that the chemical signals act as an "early-warning" response to soil drying in plants. These root-sourced chemical signals include abscisic acid (ABA) ,cytokinins (CTK) , auxin, xylem pH , Ca2+ , of which the ABA-based root signal pathway has been the most extensively and thoroughly studied in plants. This paper summarizes the basic properties, main functions and regulatory mechanisms of several major root-sourced chemical agents. Most content is focused on current research progress on stomatal behavior regulation, differential gene

  7. Generalized gradient approximation made simple

    International Nuclear Information System (INIS)

    Generalized gradient approximations Exc = ∫ d3 r f(n↑, n↓, triangledown n↑, triangledown n↓) for the exchange-correlation energy typically surpass the accuracy of the local spin density approximation and compete with standard quantum-chemical methods in electronic-structure calculations. But the derivation and analytic expression for the integrand f tend to be complicated and over-parametrized. We present a simple derivation of a simple but accurate expression for f, involving no parameter other than fundamental-constants. The derivation invoices only general ideas (not details) of the real-space cutoff construction, and agrees closely with the result of this construction. Besides its greater simplicity, this PBE96 functional has other advantages over PW91: (1) The correct behavior of the correlation energy is recovered under uniform scaling to the high-density limit. (2) The linear response of the uniform electron gas agrees with the accurate local spin density prediction. 96:006128*1 Paper TuI 6 Many-body effects are hidden in the universal density functional. The interaction of degenerate states via two-body operators, such as the electron-electron repulsion (for describing multiplets or the interaction of molecular fragments at large separations) are thus not explicitly considered in the Kohn-Sham scheme. In practice the density functionals have to be approximated, and there is a fundamental difficulty which arises in the case of degeneracy. While density functionals should be universal, the effect of degeneracy is linked to the potential characteristic to the atom, molecule, or crystal. There are, however, several possibilities to treat degeneracy effects within density functional theory, a few of which will be discussed. These take profit of the use of two-body operators, which can be, but must not be, the physical electron-electron interaction

  8. High-throughput Screening of ToxCast" Phase I Chemicals in an Embryonic Stem Cell Assay Reveals Potential Disruption of a Critical Developmental Signaling Pathway

    Science.gov (United States)

    Little is known about the developmental toxicity of the expansive chemical landscape in existence today. Significant efforts are being made to apply novel methods to predict developmental activity of chemicals utilizing high-throughput screening (HTS) and high-content screening (...

  9. Some practical aspects of B(0) gradient pulses.

    Science.gov (United States)

    Czisch, M; Ross, A; Cieslar, C; Holak, T A

    1996-03-01

    Pulsed field gradients used together with trim pulses may cause artifacts in NMR spectra that originate from partial refocusing of dephased magnetization. These effects can reduce the efficiency of solvent suppression. The duration of the trim and PFG pulses should be in the range in which refocusing is negligible. Background gradients due to bad shimming also interfere with the B(0) field gradient pulses, producing gradient-recalled echoes that reduce the receiver gain for NMR experiments. The shim settings can be optimized using simple experiments, as described in this paper. Eddy currents that cannot be completely compensated by adjustments of preemphasis induce phase shifts in NMR signals. The decay constants for a given spectrometer setup can easily be measured. If the experiment does not allow for proper compensation delays, the phase of the pulses must be adjusted to compensate for these phase shifts. PMID:22911007

  10. Combining Step Gradients and Linear Gradients in Density.

    Science.gov (United States)

    Kumar, Ashok A; Walz, Jenna A; Gonidec, Mathieu; Mace, Charles R; Whitesides, George M

    2015-06-16

    Combining aqueous multiphase systems (AMPS) and magnetic levitation (MagLev) provides a method to produce hybrid gradients in apparent density. AMPS—solutions of different polymers, salts, or surfactants that spontaneously separate into immiscible but predominantly aqueous phases—offer thermodynamically stable steps in density that can be tuned by the concentration of solutes. MagLev—the levitation of diamagnetic objects in a paramagnetic fluid within a magnetic field gradient—can be arranged to provide a near-linear gradient in effective density where the height of a levitating object above the surface of the magnet corresponds to its density; the strength of the gradient in effective density can be tuned by the choice of paramagnetic salt and its concentrations and by the strength and gradient in the magnetic field. Including paramagnetic salts (e.g., MnSO4 or MnCl2) in AMPS, and placing them in a magnetic field gradient, enables their use as media for MagLev. The potential to create large steps in density with AMPS allows separations of objects across a range of densities. The gradients produced by MagLev provide resolution over a continuous range of densities. By combining these approaches, mixtures of objects with large differences in density can be separated and analyzed simultaneously. Using MagLev to add an effective gradient in density also enables tuning the range of densities captured at an interface of an AMPS by simply changing the position of the container in the magnetic field. Further, by creating AMPS in which phases have different concentrations of paramagnetic ions, the phases can provide different resolutions in density. These results suggest that combining steps in density with gradients in density can enable new classes of separations based on density. PMID:25978093

  11. Mass Transfer Along a Temperature Gradient

    International Nuclear Information System (INIS)

    This paper reviews the fundamental understanding of the processes of mass transfer in solids subjected to a temperature gradient. The phenomenological description of these processes depends upon a knowledge of parameters called ''heats of transport'' as well as (chemical) diffusion coefficients. The description of the Soret effect and the influence of a temperature gradient upon chemical diffusion are discussed in these terms. Although there is good knowledge of diffusion coefficients and, in many examples, also a clear understanding of these in terms of underlying atomic processes, this is not true of heats of transport. Simple kinetic arguments have often led people to suppose that heats of transport will be largely independent of temperature and equal to or less than the heats of activation for the relevant atomic displacement jump. Recent experimental results on (i) heats of transport of interstitial solutes in metals and (ii) intrinsic heats of transport in pure metals and ionic crystals are reviewed here and show that these expectations are wrong. Heats of transport in these systems show an unexpected temperature dependence and their magnitude may be greater than the corresponding heats of activation. The theoretical problem of describing these results in terms of crystal lattice dynamics has, so far, eluded solution. (author)

  12. Abundance gradients in low surface brightness spirals: clues on the origin of common gradients in galactic discs

    CERN Document Server

    Bresolin, Fabio

    2015-01-01

    We acquired spectra of 141 HII regions in ten late-type low surface brightness galaxies (LSBGs). The analysis of the chemical abundances obtained from the nebular emission lines shows that metallicity gradients are a common feature of LSBGs, contrary to previous claims concerning the absence of such gradients in this class of galaxies. The average slope, when expressed in units of the isophotal radius, is found to be significantly shallower in comparison to galaxies of high surface brightness. This result can be attributed to the reduced surface brightness range measured across their discs, when combined with a universal surface mass density-metallicity relation. With a similar argument we explain the common abundance gradient observed in high surface brightness galaxy (HSBG) discs and its approximate dispersion. This conclusion is reinforced by our result that LSBGs share the same common abundance gradient with HSBGs, when the slope is expressed in terms of the exponential disc scale length.

  13. Spatial gradient tuning in metamaterials

    Science.gov (United States)

    Driscoll, Tom; Goldflam, Michael; Jokerst, Nan; Basov, Dimitri; Smith, David

    2011-03-01

    Gradient Index (GRIN) metamaterials have been used to create devices inspired by, but often surpassing the potential of, conventional GRIN optics. The unit-cell nature of metamaterials presents the opportunity to exert much greater control over spatial gradients than is possible in natural materials. This is true not only during the design phase but also offers the potential for real-time reconfiguration of the metamaterial gradient. This ability fits nicely into the picture of transformation-optics, in which spatial gradients can enable an impressive suite of innovative devices. We discuss methods to exert control over metamaterial response, focusing on our recent demonstrations using Vanadium Dioxide. We give special attention to role of memristance and mem-capacitance observed in Vanadium Dioxide, which simplify the demands of stimuli and addressing, as well as intersecting metamaterials with the field of memory-materials.

  14. Flame Propagation Through Concentration Gradient

    Institute of Scientific and Technical Information of China (English)

    JunyaIINO; MitsuakiTANABE; 等

    2000-01-01

    The experiment was carried out in homogeneous propane-air mixture and in several concentration gradient of mixture.Igniter is put on the upper side of the combustion chamber,In concentration gradient experiment.ixture was ignited from lean side.An experimental study was conducted in a combustion chamber.The combustion chamber has glass windows for optical measurements at any side.For the measurement of distribution of fuel concentration,infraed absorption method using 3.39μm He-Ne laser was used,and for the observation of proagating flams,Schlieren method was employed.As a measurment result of flame propagation velocity and flammable limit,for a mixture of an identical local equivalence ratio.flame propagation velocity in concentration gradient is faster than that in homogeneous mixture,and rich flammable limit in concentration gradient shows a tendency to be higher than that in homogeneous mixture.

  15. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, John William

    1997-01-01

    A Sobolev gradient of a real-valued functional is a gradient of that functional taken relative to the underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. Equal emphasis is placed on numerical and theoretical matters. Several concrete applications are made to illustrate the method. These applications include (1) Ginzburg-Landau functionals of superconductivity, (2) problems of transonic flow in which type depends locally on nonlinearities, and (3) minimal surface problems. Sobolev gradient constructions rely on a study of orthogonal projections onto graphs of closed densely defined linear transformations from one Hilbert space to another. These developments use work of Weyl, von Neumann and Beurling.

  16. Depth-Related Gradients of Viral Activity in Lake Pavin

    OpenAIRE

    Colombet, J.; T. Sime-Ngando; Cauchie, H. M.; Fonty, G; L. Hoffmann; Demeure, G.

    2006-01-01

    High-resolution vertical sampling and determination of viral and prokaryotic parameters in a deep volcanic lake shows that in the absence of thermal stratification but within light, oxygen, and chlorophyll gradients, host availability empirically is prevalent over the physical and chemical environments and favors lytic over lysogenic “viral life cycles.”

  17. On the metallicity gradient of the Galactic disk

    NARCIS (Netherlands)

    Pedicelli, S.; Bono, G.; Lemasle, B.; Francois, P.; Groenewegen, M.; Lub, J.; Pel, J. W.; Laney, D.; Piersimoni, A.; Romaniello, M.; Buonanno, R.; Caputo, F.; Cassisi, S.; Castelli, F.; Leurini, S.; Pietrinferni, A.; Primas, F.; Pritchard, J.

    2009-01-01

    Aims. The iron abundance gradient in the Galactic stellar disk provides fundamental constraints on the chemical evolution of this important Galaxy component, however the spread around the mean slope is, at fixed Galactocentric distance, more than the estimated uncertainties. Methods. To provide quan

  18. Gradient boosting machines, a tutorial

    OpenAIRE

    Natekin, Alexey; Knoll, Alois

    2013-01-01

    Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods with a strong focus on machine learning aspects of modeling. A theoretical information is complemented with de...

  19. Gradient Boosting Machines, A Tutorial

    OpenAIRE

    Alexey Natekin; Alois Knoll

    2013-01-01

    Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods. A theoretical information is complemented with many descriptive examples and illustrations which cover all th...

  20. Morin ameliorates chemically induced liver fibrosis in vivo and inhibits stellate cell proliferation in vitro by suppressing Wnt/β-catenin signaling

    Energy Technology Data Exchange (ETDEWEB)

    MadanKumar, Perumal; NaveenKumar, Perumal; Manikandan, Samidurai [Department of Biochemistry, University of Madras, Guindy Campus, Chennai 600 025, Tamil Nadu (India); Devaraj, Halagowder [Department of Zoology, University of Madras, Guindy Campus, Chennai 600 025, Tamil Nadu (India); NiranjaliDevaraj, Sivasithamparam, E-mail: niranjali@yahoo.com [Department of Biochemistry, University of Madras, Guindy Campus, Chennai 600 025, Tamil Nadu (India)

    2014-06-01

    The anti-fibrotic effect of morin was examined in LX-2 cells (culture-activated human hepatic stellate cells) and in diethylnitrosamine induced rat model of liver fibrosis. The in vitro study was designed to determine whether morin affects the survival of cultured LX-2 cells, while the in vivo study was designed to evaluate the antioxidant and anti-fibrotic efficacy of morin on diethylnitrosamine induced liver fibrosis in male albino Wistar rat. The activities of liver function enzymes in serum, liver lipid peroxide levels, activities of serum antioxidant enzymes and liver architecture were monitored to cast light on the antioxidant and hepatoprotective nature of morin. To establish the anti-fibrotic effects of morin, the levels of key Wnt signaling molecules which are strongly associated with the signal transduction pathway of HSC activation were measured. Overall, from the in vitro results, it was observed that morin at 50 μM concentration inhibited the proliferation of cultured LX-2 cells, inhibited Wnt signaling and induced G1 cell cycle arrest. The in vivo results further confirmed that morin by downregulating the expressions of GSK-3β, β-catenin and cyclin D1 ameliorated DEN-induced liver fibrosis. Hence morin could be employed as a promising chemopreventive natural supplement for liver fibrosis. - Highlights: • In vivo and in vitro results revealed the active participation of Wnt signaling. • Morin at 50 μM inhibited LX-2 cell proliferation by suppressing Wnt signaling. • Morin exhibited hepatoprotective effects against DEN induced liver fibrosis. • Morin inhibited HSC activation in vivo by downregulating Wnt/β-catenin signaling.

  1. Morin ameliorates chemically induced liver fibrosis in vivo and inhibits stellate cell proliferation in vitro by suppressing Wnt/β-catenin signaling

    International Nuclear Information System (INIS)

    The anti-fibrotic effect of morin was examined in LX-2 cells (culture-activated human hepatic stellate cells) and in diethylnitrosamine induced rat model of liver fibrosis. The in vitro study was designed to determine whether morin affects the survival of cultured LX-2 cells, while the in vivo study was designed to evaluate the antioxidant and anti-fibrotic efficacy of morin on diethylnitrosamine induced liver fibrosis in male albino Wistar rat. The activities of liver function enzymes in serum, liver lipid peroxide levels, activities of serum antioxidant enzymes and liver architecture were monitored to cast light on the antioxidant and hepatoprotective nature of morin. To establish the anti-fibrotic effects of morin, the levels of key Wnt signaling molecules which are strongly associated with the signal transduction pathway of HSC activation were measured. Overall, from the in vitro results, it was observed that morin at 50 μM concentration inhibited the proliferation of cultured LX-2 cells, inhibited Wnt signaling and induced G1 cell cycle arrest. The in vivo results further confirmed that morin by downregulating the expressions of GSK-3β, β-catenin and cyclin D1 ameliorated DEN-induced liver fibrosis. Hence morin could be employed as a promising chemopreventive natural supplement for liver fibrosis. - Highlights: • In vivo and in vitro results revealed the active participation of Wnt signaling. • Morin at 50 μM inhibited LX-2 cell proliferation by suppressing Wnt signaling. • Morin exhibited hepatoprotective effects against DEN induced liver fibrosis. • Morin inhibited HSC activation in vivo by downregulating Wnt/β-catenin signaling

  2. Some applications of CALPHAD techniques to diffusion reactions in gradient materials

    OpenAIRE

    Helander, Thomas

    1999-01-01

    In gradient materials, i.e. materials that have varyingproperties due to an inhomogeneous chemical composition, thereis usually a strong driving force for diffusion reactions inthe gradient zone. Such reactions may have a strong influenceon the properties of the material. In this doctoral thesisCALPHAD techniques are applied to some problems which arerelevant for diffusion reactions in gradient materials. It isshown that these techniques can give information which isindustrially highly releva...

  3. Microfabricated refractive index gradient based detector for reversed-phase liquid chromatography with mobile phase gradient elution.

    Science.gov (United States)

    McBrady, Adam D; Synovec, Robert E

    2006-02-10

    Typical refractive index (RI) detectors for liquid chromatography (LC) are not well suited to application with mobile phase gradient elution, due to the difficulty in correcting for the detected baseline shift during the gradient. We report a sensitive, highly reproducible, microfabricated refractive index gradient (micro-RIG) detector that performs well with mobile phase gradient elution LC. Since the micro-RIG signal remains on-scale throughout the mobile phase gradient, one can apply a baseline correction procedure. We demonstrate that by collecting two mobile phase gradient blanks and subtracting one of them from the other, a reproducible, flat baseline is achieved. Therefore, subtracting a blank from a separation provides a baseline corrected chromatogram with reasonably high signal-to-noise ratio for eluting analytes. The micro-RIG detector uses a collimated diode laser beam to optically probe a RIG formed perpendicular to the laminar flow direction within a microfabricated borosilicate glass chip. The chip-based design of the detector is suitable for either traditional bench-top or LC-on-a-chip technologies. We report reversed phase high performance liquid chromatography (RP-HPLC) separations of proteins and polymers, over mobile phase gradient conditions of 67% A:33% B to 3% A:97% B by volume, where A is 96% methanol:3.9% water:0.1% trifluoroacetic acid (TFA), and B is 3.9% methanol:96% water:0.1% TFA. The separations were performed on a Jupiter 5 mu C4 300 A 150 mm x 1.0 mm Phenomenex column at a flow rate of 20 microl/min. Viscosity changes during the mobile phase gradient separation are found to shift the on-chip merge position of the detected concentration gradient (i.e., RIG), in a reproducible fashion. However, this viscosity effect makes detection sensitivity vary throughout the mobile phase gradient, due to moving the optimized position of the probe beam in relation to the analyte concentration gradient being probed. None-the-less, consistent limits

  4. Signal transduction profile of chemical sensitisers in dendritic cells: An endpoint to be included in a cell-based in vitro alternative approach to hazard identification?

    International Nuclear Information System (INIS)

    The development of non-animal testing methods for the assessment of skin sensitisation potential is an urgent challenge within the framework of existing and forthcoming legislation. Efforts have been made to replace current animal tests, but so far no alternative methods have been developed. It is widely recognised that alternatives to animal testing cannot be accomplished with a single approach, but rather will require the integration of results obtained from different in vitro and in silico assays. The argument subjacent to the development of in vitro dendritic cell (DC)-based assays is that sensitiser-induced changes in the DC phenotype can be differentiated from those induced by irritants. This assumption is derived from the unique capacity of DC to convert environmental signals encountered at the skin into a receptor expression pattern (MHC class II molecules, co-stimulatory molecules, chemokine receptors) and a soluble mediator release profile that will stimulate T lymphocytes. Since signal transduction cascades precede changes in surface marker expression and cytokine/chemokine secretion, these phenotypic modifications are a consequence of a signal transduction profile that is specifically triggered by sensitisers and not by irritants. A limited number of studies have addressed this subject and the present review attempts to summarise and highlight all of the signalling pathways modulated by skin sensitisers and irritants. Furthermore, we conclude this review by focusing on the most promising strategies suitable for inclusion into a cell-based in vitro alternative approach to hazard identification.

  5. Diverse in- and output polarities and high complexity of local synaptic and nonsynaptic signalling within a chemically defined class of peptidergic Drosophila neurons

    Science.gov (United States)

    Peptidergic neurons are not easily integrated into current connectomics concepts, since their peptide messages can be distributed via non-synaptic paracrine signaling or even via volume transmission. Moreover, and especially in insects, the polarity of peptidergic interneurons in terms of in- and o...

  6. Theoretical analysis of degradation mechanisms in the formation of morphogen gradients

    CERN Document Server

    Bozorgui, Behnaz; Kolomeisky, Anatoly B

    2015-01-01

    The fundamental biological processes of development of tissues and organs in multicellular organisms is governed by various signaling molecules, which are called morphogens. It is known that spatial and temporal variations in concentration profiles of signaling molecules, which are frequently referred as morphogen gradients, lead to cell differentiation via activating specific genes in a concentration-dependent manner. It is widely accepted that the establishment of the morphogen gradients involves multiple biochemical reactions and diffusion processes. One of the critical elements in the formation of morphogen gradients is a degradation of signaling molecules. We develop a new theoretical approach that provides a comprehensive description of the degradation mechanisms. It is based on the idea that the degradation works as an effective potential that drives the signaling molecules away from the source region. Utilizing the method of first-passage processes, the dynamics of the formation of morphogen gradients...

  7. Direct Measurements of Colloidal Solvophoresis under Imposed Solvent and Solute Gradients.

    Science.gov (United States)

    Paustian, Joel S; Angulo, Craig D; Nery-Azevedo, Rodrigo; Shi, Nan; Abdel-Fattah, Amr I; Squires, Todd M

    2015-04-21

    We describe a microfluidic system that enables direct visualization and measurement of diffusiophoretic migration of colloids in response to imposed solution gradients. Such measurements have proven difficult or impossible in macroscopic systems due to difficulties in establishing solution gradients that are sufficiently strong yet hydrodynamically stable. We validate the system with measurements of the concentration-dependent diffusiophoretic mobility of polystyrene colloids in NaCl gradients, confirming that diffusiophoretic migration velocities are proportional to gradients in the logarithm of electrolyte concentration. We then perform the first direct measurement of the concentration-dependent "solvophoretic" mobility of colloids in ethanol-water gradients, whose dependence on concentration and gradient strength was not known either theoretically or experimentally, but which our measurements reveal to be proportional to the gradient in the logarithm of ethanol mole fraction. Finally, we examine solvophoretic migration under a variety of qualitatively distinct chemical gradients, including solvents that are miscible or have finite solubility with water, an electrolyte for which diffusiophoresis proceeds down concentration gradients (unlike for most electrolytes), and a nonelectrolyte (sugar). Our technique enables the direct characterization of diffusiophoretic mobilities of various colloids under various solvent and solute gradients, analogous to the electrophoretic ζ-potential measurements that are routinely used to characterize suspensions. We anticipate that such measurements will provide the feedback required to test and develop theories for solvophoretic and diffusiophoretic migration and ultimately to the conceptual design and engineering of particles that respond in a desired way to their chemical environments. PMID:25821916

  8. Cerebral microhemorrhage : assessment with gradient-echo Mr

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eung Yeop; Na, Dong Gyu; Byun, Hong Sik; Shin, Myung Hee [Samsung Medical Center, Seoul (Korea, Republic of)

    1998-05-01

    The purpose of this study is to assess the relationship between low signal intensity lesions, as seen on gradient-echo MR, and clinical factors. In 269 patients with cerebral ischemic symptoms, we analysed the results of gradient-echo MR. One hundred and thirty-nine of the patients were male and 130 were female; their ages ranged from 40 to 88 (mean, 64) years. Low signal intensity lesions were analyzed according to the dominant location ; superficial (cortex and subcortical white matter) or deep (basal ganglia, thalamus, periventricular white matter, and cerebellum). We analyzed the relationship between low signal intensity lesions and clinical factors including hypertension, diabetes mellitus (DM), and spontaneous intracerebral hemorrhage (ICH). Low signal intensity lesions were found in 66 of 269 patients (25%); hypertension was present in 57 of the 66 (86%, p< 0.05), DM in nine (14%, p>0.05), and spontaneous ICH in 26 (39 %, p<0.05). The dominant location of these lesions was superficial (n=19), deep (n=45), or both (n=2). Hypertension was deep. Hypertension was not present in nine of 66 patients (14%) with low signal intensity lesions; in six of these (66%), low signal intensity lesions were present mainly in the subcortical white matter or cortex. Cerebral low signal intensity lesions, as seen on gradient-echo MR imaging were associated with clinical factors such as hypertension and spontaneous ICH, and hypertension was more frequently found in patients in whom the location of low signal intensity lesions was deep. (author). 19 refs., 1 tab., 3 figs.

  9. The influence of ALN-Al gradient material gradient index on ballistic performance

    International Nuclear Information System (INIS)

    Ballistic performance of the gradient material is superior to laminated material, and gradient materials have different gradient types. Using ls-dyna to simulate the ballistic performance of ALN-AL gradient target plates which contain three gradient index (b = 1, b = 0.5, b = 2). Through Hopkinson bar numerical simulation to the target plate materials, we obtained the reflection stress wave and transmission stress wave state of gradient material to get the best gradient index. The internal stress state of gradient material is simulated by amplification processing of the target plate model. When the gradient index b is equal to 1, the gradient target plate is best of all.

  10. The influence of ALN-Al gradient material gradient index on ballistic performance

    Science.gov (United States)

    Wang, Youcong; Liu, Qiwen; Li, Yao; Shen, Qiang

    2013-03-01

    Ballistic performance of the gradient material is superior to laminated material, and gradient materials have different gradient types. Using ls-dyna to simulate the ballistic performance of ALN-AL gradient target plates which contain three gradient index (b = 1, b = 0.5, b = 2). Through Hopkinson bar numerical simulation to the target plate materials, we obtained the reflection stress wave and transmission stress wave state of gradient material to get the best gradient index. The internal stress state of gradient material is simulated by amplification processing of the target plate model. When the gradient index b is equal to 1, the gradient target plate is best of all.

  11. Gradient expansion for anisotropic hydrodynamics

    CERN Document Server

    Florkowski, Wojciech; Spaliński, Michał

    2016-01-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of non-hydrodynamic modes.

  12. Seismic waves travel-time curve, basing on the results of signal detection from chemical explosions detonated at Semipalatinsk Test Site

    International Nuclear Information System (INIS)

    A large amount of digital seismic data from the permanent and temporary seismic stations was acquired in the result of detonation of large chemical explosions at Semipalatinsk Test Site. All the records were collected, systematized and processed, and databases were created. Travel-time curves for regional Pn, Pg, Sn and Lg waves were created and compared with the ones used in routine earthquake processing practice. (author)

  13. High Gradient Wakefields in Dielectric Loaded Structures

    International Nuclear Information System (INIS)

    Dielectric loaded wakefield structures have potential to be used as high gradient accelerator components. Using the high current drive beam at the Argonne Wakefield Accelerator Facility, we employed cylindrical dielectric loaded wakefield structures to generate accelerating fields of up to 86 MV/m, at 10 GHz. Short electron bunches of up to 86 nC are used to drive these fields, either as single bunches or as bunch trains. The structures consist of cylindrical ceramic tubes (cordierite) with a dielectric constant of 4.76, inserted into cylindrical copper waveguides. These standing-wave structures have a field probe near the outer diameter of the dielectric, in order to sample the RF fields generated by the electron bunches. Monitoring the field probe signal serves to verify the absence of electric breakdown in the structures. MAFIA simulations are used to calculate the amplitude of the fields generated by the traversing electrons bunches

  14. Gravity Gradient Tensor Eigendecomposition for Spacecraft Positioning

    CERN Document Server

    Chen, Pei; Han, Chao

    2016-01-01

    In this Note, a new approach to spacecraft positioning based on GGT inversion is presented. The gravity gradient tensor is initially measured in the gradiometer reference frame (GRF) and then transformed to the Earth-Centered Earth-Fixed (ECEF) frame via attitude information as well as Earth rotation parameters. Matrix Eigen-Decomposition is introduced to directly translate GGT into position based on the fact that the eigenvalues and eigenvectors of GGT are simplespecific functions of spherical coordinates of the observation position. without the need of an initial position. Unlike the strategy of inertial navigation aiding, no prediction or first guess of the spacecraft position is needed. The method makes use of the J2 gravity model, and is suitable for space navigation where higher frequency terrain contributions to the GGT signals can be neglected.

  15. A fast, preconditioned conjugate gradient Toeplitz solver

    Science.gov (United States)

    Pan, Victor; Schrieber, Robert

    1989-01-01

    A simple factorization is given of an arbitrary hermitian, positive definite matrix in which the factors are well-conditioned, hermitian, and positive definite. In fact, given knowledge of the extreme eigenvalues of the original matrix A, an optimal improvement can be achieved, making the condition numbers of each of the two factors equal to the square root of the condition number of A. This technique is to applied to the solution of hermitian, positive definite Toeplitz systems. Large linear systems with hermitian, positive definite Toeplitz matrices arise in some signal processing applications. A stable fast algorithm is given for solving these systems that is based on the preconditioned conjugate gradient method. The algorithm exploits Toeplitz structure to reduce the cost of an iteration to O(n log n) by applying the fast Fourier Transform to compute matrix-vector products. Matrix factorization is used as a preconditioner.

  16. Spatial temperature gradients guide axonal outgrowth

    Science.gov (United States)

    Black, Bryan; Vishwakarma, Vivek; Dhakal, Kamal; Bhattarai, Samik; Pradhan, Prabhakar; Jain, Ankur; Kim, Young-Tae; Mohanty, Samarendra

    2016-07-01

    Formation of neural networks during development and regeneration after injury depends on accuracy of axonal pathfinding, which is primarily believed to be influenced by chemical cues. Recently, there is growing evidence that physical cues can play crucial role in axonal guidance. However, detailed mechanism involved in such guidance cues is lacking. By using weakly-focused near-infrared continuous wave (CW) laser microbeam in the path of an advancing axon, we discovered that the beam acts as a repulsive guidance cue. Here, we report that this highly-effective at-a-distance guidance is the result of a temperature field produced by the near-infrared laser light absorption. Since light absorption by extracellular medium increases when the laser wavelength was red shifted, the threshold laser power for reliable guidance was significantly lower in the near-infrared as compared to the visible spectrum. The spatial temperature gradient caused by the near-infrared laser beam at-a-distance was found to activate temperature-sensitive membrane receptors, resulting in an influx of calcium. The repulsive guidance effect was significantly reduced when extracellular calcium was depleted or in the presence of TRPV1-antagonist. Further, direct heating using micro-heater confirmed that the axonal guidance is caused by shallow temperature-gradient, eliminating the role of any non-photothermal effects.

  17. Feature Extraction of ECG Signal Using HHT Algorithm

    OpenAIRE

    Neha Soorma; Jaikaran Singh; Mukesh Tiwari

    2014-01-01

    This paper describe the features extraction algorithm for electrocardiogram (ECG) signal using Huang Hilbert Transform and Wavelet Transform. ECG signal for an individual human being is different due to unique heart structure. The purpose of feature extraction of ECG signal would allow successful abnormality detection and efficient prognosis due to heart disorder. Some major important features will be extracted from ECG signals such as amplitude, duration, pre-gradient, post-gradient and so o...

  18. Fano resonances from gradient-index metamaterials

    Science.gov (United States)

    Xu, Yadong; Li, Sucheng; Hou, Bo; Chen, Huanyang

    2016-01-01

    Fano resonances - resonant scattering features with a characteristic asymmetric profile - have generated much interest, due to their extensive and valuable applications in chemical or biological sensors, new types of optical switches, lasers and nonlinear optics. They have been observed in a wide variety of resonant optical systems, including photonic crystals, metamaterials, metallic gratings and nanostructures. In this work, a waveguide structure is designed by employing gradient-index metamaterials, supporting strong Fano resonances with extremely sharp spectra. As the changes in the transmission spectrum originate from the interaction of guided modes from different channels, instead of resonance structures or metamolecules, the Fano resonances can be observed for both transverse electric and transverse magnetic polarizations. These findings are verified by fine agreement with analytical calculations and experimental results at microwave, as well as simulated results at near infrared frequencies.

  19. Near-infrared spectra of Penicillium camemberti strains separated by extended multiplicative signal correction improved prediction of physical and chemical variations

    DEFF Research Database (Denmark)

    Decker, Marianne; Nielsen, Per Væggemose; Martens, Harald

    2005-01-01

    signal correction (TWEMSC) preprocessing, whereby three patterns of variation in near-infrared (NIR) log(1/R) spectra of fungal colonies could be separated mathematically: (1) physical light scattering and its wavelength dependency, (2) differences in light absorption of water due to varying sample...... temperature, etc., and (3) differences in light absorption between different fungal isolates. With this preprocessing, discriminant partial least squares (PLS) regression yielded 100% correct classification of three isolates, both within the cross-validated calibration set and in two independent test sets of...

  20. On gradient Ricci solitons with Symmetry

    OpenAIRE

    Petersen, Peter; Wylie, William

    2007-01-01

    We study gradient Ricci solitons with maximal symmetry. First we show that there are no non-trivial homogeneous gradient Ricci solitons. Thus the most symmetry one can expect is an isometric cohomogeneity one group action. Many examples of cohomogeneity one gradient solitons have been constructed. However, we apply the main result in our paper "Rigidity of gradient Ricci solitons" to show that there are no noncompact cohomogeneity one shrinking gradient solitons with nonnegative curvature.

  1. Biomedical signals and systems

    CERN Document Server

    Tranquillo, Joseph V

    2013-01-01

    Biomedical Signals and Systems is meant to accompany a one-semester undergraduate signals and systems course. It may also serve as a quick-start for graduate students or faculty interested in how signals and systems techniques can be applied to living systems. The biological nature of the examples allows for systems thinking to be applied to electrical, mechanical, fluid, chemical, thermal and even optical systems. Each chapter focuses on a topic from classic signals and systems theory: System block diagrams, mathematical models, transforms, stability, feedback, system response, control, time

  2. Variable metric conjugate gradient methods

    Energy Technology Data Exchange (ETDEWEB)

    Barth, T.; Manteuffel, T.

    1994-07-01

    1.1 Motivation. In this paper we present a framework that includes many well known iterative methods for the solution of nonsymmetric linear systems of equations, Ax = b. Section 2 begins with a brief review of the conjugate gradient method. Next, we describe a broader class of methods, known as projection methods, to which the conjugate gradient (CG) method and most conjugate gradient-like methods belong. The concept of a method having either a fixed or a variable metric is introduced. Methods that have a metric are referred to as either fixed or variable metric methods. Some relationships between projection methods and fixed (variable) metric methods are discussed. The main emphasis of the remainder of this paper is on variable metric methods. In Section 3 we show how the biconjugate gradient (BCG), and the quasi-minimal residual (QMR) methods fit into this framework as variable metric methods. By modifying the underlying Lanczos biorthogonalization process used in the implementation of BCG and QMR, we obtain other variable metric methods. These, we refer to as generalizations of BCG and QMR.

  3. Hydraulic gradients in rock aquifers

    International Nuclear Information System (INIS)

    This report deals with fractured rock as a host for deposits of hazardous waste. In this context the rock, with its fractures containing moving groundwater, is called the geological barrier. The desired properties of the geological barrier are low permeability to water, low hydraulic gradients and ability to retain matter dissolved in the water. The hydraulic gradient together with the permeability and the porosity determines the migration velocity. Mathematical modelling of the migration involves calculation of the water flow and the hydrodynamic dispersion of the contaminant. The porous medium approach can be used to calculate mean flow velocities and hydrodynamic dispersion of a large number of fractures are connected, which means that a large volume have to be considered. It is assumed that the porous medium approach can be applied, and a number of idealized examples are shown. It is assumed that the groundwater table is replenished by percolation at a constant rate. One-dimensional analytical calculations show that zero hydraulic gradients may exist at relatively large distance from the coast. Two-dimensional numerical calculations show that it may be possible to find areas with low hydraulic gradients and flow velocities within blocks surrounded by areas with high hydraulic conductivity. (au)

  4. Momentum expectation values : gradient terms

    OpenAIRE

    Plindov, G.I.; Dmitrieva, I.K.

    1984-01-01

    The lowest order inhomogeneity correction for the momentum expectation values, , is derived by means of Kirzhnits' gradient expansion technique. The use of the scaling allows a qualitative estimate of for the Coulomb many-body systems. A quantitative estimate of the inhomogeneity contribution to the expectation values, , for a neutral atom is made.

  5. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independent...

  6. Compositional gradients in Gramineae genes

    DEFF Research Database (Denmark)

    Wong, Gane Ka-Shu; Wang, Jun; Tao, Lin;

    2002-01-01

    In this study, we describe a property of Gramineae genes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5'-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage...

  7. Analysis of the surface photoabsorption signal during self-limited submonolayer growth of InP in metalorganic chemical vapor deposition

    CERN Document Server

    Lee, T W; Moon, Y B; Yoon, E J; Kim, Y D

    1999-01-01

    In situ, real-time monitoring of InP atomic layer epitaxy (ALE) was performed in low-pressure metalorganic chemical vapor deposition (LP-MOCVD) by surface photoabsorption (SPA). A self-limiting adsorption condition was obtained from the trimethylindium (TMIn) decomposition experiment at various conditions. It was found that the growth rate was less than 1 monolayer (ML)/cycle. From the in situ, real-time SPA measurement during InP ALE, the incomplete PH sub 3 decomposition on the methyl-terminated In surface was attributed to the self-limiting submonolayer growth per cycle.

  8. Emergent Collective Chemotaxis without Single-Cell Gradient Sensing

    Science.gov (United States)

    Camley, Brian A.; Zimmermann, Juliane; Levine, Herbert; Rappel, Wouter-Jan

    2016-03-01

    Many eukaryotic cells chemotax, sensing and following chemical gradients. However, experiments show that even under conditions when single cells cannot chemotax, small clusters may still follow a gradient. This behavior is observed in neural crest cells, in lymphocytes, and during border cell migration in Drosophila, but its origin remains puzzling. Here, we propose a new mechanism underlying this "collective guidance," and study a model based on this mechanism both analytically and computationally. Our approach posits that contact inhibition of locomotion, where cells polarize away from cell-cell contact, is regulated by the chemoattractant. Individual cells must measure the mean attractant value, but need not measure its gradient, to give rise to directional motility for a cell cluster. We present analytic formulas for how the cluster velocity and chemotactic index depend on the number and organization of cells in the cluster. The presence of strong orientation effects provides a simple test for our theory of collective guidance.

  9. Migration of inclusions in solids in stress gradients

    International Nuclear Information System (INIS)

    A theoretical method of assessing the influence of stress and temperature gradients on the motion of inclusions in solids is developed. In nonuniform stress fields, the stress distribution on the surface of the cavity must be calculated and transformed to a potential gradient for driving a surface atom flux. The bubble migration velocity is the first Legendre coefficient of the surface flux. Higher order components represent distortion. The stress gradient effect appears only in small-magnitude terms in the surface chemical potential, specifically in the stress effect on the solid atomic volume and in the elastic energy density. The migration velocities of spherical and faceted bubbles in solids are computed and the extent of distortion of a spherical bubble is estimated. The role of vacancy exchange with the bulk solid on the migration velocity is assessed. (author)

  10. Optimization in Quaternion Dynamic Systems: Gradient, Hessian, and Learning Algorithms.

    Science.gov (United States)

    Xu, Dongpo; Xia, Yili; Mandic, Danilo P

    2016-02-01

    The optimization of real scalar functions of quaternion variables, such as the mean square error or array output power, underpins many practical applications. Solutions typically require the calculation of the gradient and Hessian. However, real functions of quaternion variables are essentially nonanalytic, which are prohibitive to the development of quaternion-valued learning systems. To address this issue, we propose new definitions of quaternion gradient and Hessian, based on the novel generalized Hamilton-real (GHR) calculus, thus making a possible efficient derivation of general optimization algorithms directly in the quaternion field, rather than using the isomorphism with the real domain, as is current practice. In addition, unlike the existing quaternion gradients, the GHR calculus allows for the product and chain rule, and for a one-to-one correspondence of the novel quaternion gradient and Hessian with their real counterparts. Properties of the quaternion gradient and Hessian relevant to numerical applications are also introduced, opening a new avenue of research in quaternion optimization and greatly simplified the derivations of learning algorithms. The proposed GHR calculus is shown to yield the same generic algorithm forms as the corresponding real- and complex-valued algorithms. Advantages of the proposed framework are illuminated over illustrative simulations in quaternion signal processing and neural networks. PMID:26087504

  11. Two-Step Bipolar Electrochemistry: Generation of Composition Gradient and Visual Screening of Electrocatalytic Activity.

    Science.gov (United States)

    Termebaf, Hajar; Shayan, Mohsen; Kiani, Abolfazl

    2015-12-01

    Bipolar electrochemistry (BE) is employed for both creating electrocatalysts composition gradient and visual screening of the prepared composition on a single substrate in just two experiment runs. In a series of proof-of-principle experiments, we demonstrate gradient electrodeposition of Ni-Cu using BE; then the electrocatalytic activity of the prepared composition gradient toward the hydrogen evolution reaction (HER) is visually screened in the BE system using array of BPEs. Moreover, the morphology and the chemical composition of the Ni-Cu gradient are screened along the length of the bipolar electrode (BPE). By measuring the potential gradient over the BPE, it is also demonstrated that by controlling the concentration of the metals precursor and the supporting electrolyte, the length of the bipolar electrodeposited gradient can be controlled. PMID:26595192

  12. Polymer brush gradients grafted from plasma-polymerized surfaces.

    Science.gov (United States)

    Coad, Bryan R; Bilgic, Tugba; Klok, Harm-Anton

    2014-07-22

    A new method for generating a surface density gradient of polymer chains is presented. A substrate-independent polymer deposition technique was used to coat materials with a chemical gradient based on plasma copolymerization of 1,7-octadiene and allylamine. This provided a uniform chemical gradient to which initiators for atom transfer radical polymerization (ATRP) were immobilized. After surface-initiated atom transfer radical polymerization (SI-ATRP), poly(2-hydroxyethyl methacrylate) (PHEMA) chains were grafted from the surface and the measured thickness profiles provided direct evidence for how surface crowding provides an entropic driving force resulting in chain extension away from the surface. Film thicknesses were found to increase with the position along the gradient surface, reflecting the gradual transition from collapsed to more extended surface-tethered polymer chains as the grafting density increased. The method described is novel in that the approach provides covalent linkages from the polymer coating to the substrate and is not limited to a particular surface chemistry of the starting material. PMID:24967529

  13. Dynamics and precision in retinoic acid morphogen gradients

    OpenAIRE

    SCHILLING, THOMAS F.; Nie, Qing; Lander, Arthur D.

    2012-01-01

    Retinoic acid (RA) regulates many cellular behaviors during embryonic development and adult homeostasis. Like other morphogens, RA forms gradients through the use of localized sources and sinks, feedback, and interactions with other signals; this has been particularly well studied in the context of hindbrain segmentation in vertebrate embryos. Yet, as a small lipophilic molecule derived from a dietary source—vitamin A—RA differs markedly from better-studied polypeptide morphogens in its mecha...

  14. Signal Words

    Science.gov (United States)

    SIGNAL WORDS TOPIC FACT SHEET NPIC fact sheets are designed to answer questions that are commonly asked by the ... making decisions about pesticide use. What are Signal Words? Signal words are found on pesticide product labels, ...

  15. Computational strain gradient crystal plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2014-01-01

    A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems...... of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically...... oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale....

  16. Multilayer coating for high gradients

    CERN Document Server

    Kubo, Takayuki

    2016-01-01

    The multilayer coating for high gradients is reviewed. Not only the S-I-S structure, but also the S-S bilayer structure are also treated. This is an incomplete manuscript of an invited article which will be submitted to a journal. I have uploaded this version in order to help the understanding on my talk at the TESLA Technology Collaboration meeting at Saclay, France.

  17. Smooth Optimization with Approximate Gradient

    OpenAIRE

    d'Aspremont, Alexandre

    2005-01-01

    We show that the optimal complexity of Nesterov's smooth first-order optimization algorithm is preserved when the gradient is only computed up to a small, uniformly bounded error. In applications of this method to semidefinite programs, this means in some instances computing only a few leading eigenvalues of the current iterate instead of a full matrix exponential, which significantly reduces the method's computational cost. This also allows sparse problems to be solved efficiently using spar...

  18. Primordial vorticity and gradient expansion

    CERN Document Server

    Giovannini, Massimo

    2012-01-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $\\Lambda$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the or...

  19. Primordial vorticity and gradient expansion

    Science.gov (United States)

    Giovannini, Massimo; Rezaei, Zahra

    2012-02-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the ΛCDM paradigm, the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the order of 10-37 G over the typical comoving scales ranging between 1 and 10 Mpc. While the obtained results seem to be irrelevant for seeding a reasonable galactic dynamo action, they demonstrate how the proposed fully inhomogeneous treatment can be used for the systematic scrutiny of pre-decoupling plasmas beyond the conventional perturbative expansions.

  20. CAPMIX - Deploying Capacitors for Salt Gradient Power Extraction

    OpenAIRE

    Bijmans, M.F.M.; Burheim, O.S.; Bryjak, M.; Delgado, A; Hack, P.; Mantegazza, F.; Tenisson, S.; Hamelers, H.V.M.

    2012-01-01

    The process of mixing sea and river water can be utilised as a power source. At present, three groups of technology are established for doing so; i) mechanical; Pressure Retarded Osmosis PRO, ii) electrochemical reactions; Reverse ElectroDialysis (RED) and Nano Battery Electrodes (NBE) and iii) ultra capacitors; Capacitive Double Layer Expansion (CDLE) and Capacitors charge by the Donnan Potentials (CDP). The chemical potential for salt gradient power systems is only limited by th...

  1. Light scattering from suspensions under external gradients

    OpenAIRE

    Bonet i Avalos, Josep; Rubí Capaceti, José Miguel; Rodríguez, R.; Pérez Madrid, Agustín

    1990-01-01

    We analyze the light-scattering spectrum of a suspension in a viscoelastic fluid under density and velocity gradients. When a density gradient is present, the dynamic structure factor exhibits universality in the sense that its expression depends only on the reduced frequency and the reduced density gradient. For a velocity gradient, however, the universality breaks down. In this last case we have found a transition point from one to three characteristic frequencies in the spectrum, which is ...

  2. STOCHASTIC GRADIENT METHODS FOR UNCONSTRAINED OPTIMIZATION

    OpenAIRE

    Nataša Krejić; Nataša Krklec Jerinkić

    2014-01-01

    This papers presents an overview of gradient based methods for minimization of noisy functions. It is assumed that the objective functions is either given with error terms of stochastic nature or given as the mathematical expectation. Such problems arise in the context of simulation based optimization. The focus of this presentation is on the gradient based Stochastic Approximation and Sample Average Approximation methods. The concept of stochastic gradient approximation of the true gradient ...

  3. Community and ecosystem responses to elevational gradients

    DEFF Research Database (Denmark)

    Sundqvist, Maja K.; Sanders, Nate; Wardle, David A.

    2013-01-01

    Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients. There...... using elevational gradients for understanding community and ecosystem responses to global climate change at much larger spatial and temporal scales than is possible through conventional ecological experiments. However, future studies that integrate elevational gradient approaches with experimental...

  4. Symmetric and asymmetric planetary nebulae and the time variation of the radial abundance gradients

    Science.gov (United States)

    Maciel, W.; Costa, R. D. D.

    2014-04-01

    Planetary nebulae (PN) are excellent laboratories to study the chemical evolution of their host galaxies, especially concerning the radial abundance gradients and their time and spatial variations. Current chemical evolution models predict either some steepening or flattening of the abundance gradients with time, and PN can be useful in order to provide observational constraints on this issue. It is generally believed that asymmetrical nebulae, especially bipolars, are formed by younger, more massive progenitor stars, while symmetrical nebulae, such as the round and elliptical objects, are formed by older, less massive stars. As a consequence, if the abundance gradients change with time, some differences are expected between the gradients measured in symmetrical and asymmetrical nebulae. We have considered a large sample of well-studied galactic PN for which accurate abundances of O, S, Ne, and Ar are known, and for which a reliable morphological classification can be made. Average abundances and radial gradients of the ratios O/H, S/H, Ne/H and Ar/H were then determined for the main morphological classes, comprising B, E, R, and P nebulae. It is found that the average abundances of the younger objects are larger than those of the older nebulae, as expected on chemical evolution grounds, but the derived gradients are essentially the same within the uncertainties. It can then be concluded that the radial abundance gradients have not changed appreciably since the older progenitor stars were born, approximately 4 to 5 Gyr ago.

  5. On the classification of gradient Ricci solitons

    OpenAIRE

    Petersen, Peter; Wylie, William

    2007-01-01

    We show that the only complete shrinking gradient Ricci solitons with vanishing Weyl tensor are quotients of the standard ones. This gives a new proof of the Hamilton-Ivey-Perel'man classification of 3-dimensional shrinking gradient solitons. We also prove a classification for expanding gradient Ricci solitons with constant scalar curvature and suitably decaying Weyl tensor.

  6. Second order gradient ascent pulse engineering

    CERN Document Server

    de Fouquieres, P; Glaser, S J; Kuprov, Ilya

    2011-01-01

    We report some improvements to the gradient ascent pulse engineering (GRAPE) algorithm for optimal control of quantum systems. These include more accurate gradients, convergence acceleration using the BFGS quasi-Newton algorithm as well as faster control derivative calculation algorithms. In all test systems, the wall clock time and the convergence rates show a considerable improvement over the approximate gradient ascent.

  7. Microstructure and hardness development in a copper-nickel diffusion gradient model system

    DEFF Research Database (Denmark)

    Duchstein, Linus Daniel Leonhard; Zhang, Xiaodan; Hansen, Niels

    2015-01-01

    Cu has been electrolytically coated with Ni and subsequently deformed by rotary swaging up to a strain of ε=2 to create a chemical gradient at the interface of the two elements. The extend of this chemical intermixing has been investigated through Energy Dispersive X-ray (EDX) spectroscopy in the...

  8. Ultrasonic flowmeters: temperature gradients and transducer geometry effects.

    Science.gov (United States)

    Willatzen, M

    2003-03-01

    Ultrasonic flowmeter performance is addressed for the case of cylindrically shaped flowmeters employing two reciprocal ultrasonic transducers A and B so as to measure time-of-flight differences between signals transmitted from transducer A towards B followed by an equivalent signal transmitted from transducer B towards A. In the case where a liquid flows through the flowmeter's measuring section ("spoolpiece"), the arrival times of the two signals differ by an amount related to the flow passing between the two transducers. Firstly, a detailed study of flow measurement errors with mean flow in the laminar flow regime is carried out as a function of the mode index and the transducer diameter/cylinder diameter ratio in the case where no temperature gradients are present in the flowmeter sensor. It is shown that all modes except the fundamental mode overestimate the mean flow by a factor of 33.33% while excitation of the fundamental mode solely give error-free measurements. The immediate consequences are that the flowmeter error decreases as the transducer diameter/cylinder diameter ratio approaches 1 from 0 reflecting the fact that the excitation level of the fundamental mode increases from almost 0 to 1 as this ratio approaches 1 from 0. Secondly, the effect on flowmeter performance due to flow-induced temperature gradients is examined. It is shown that the presence of temperature gradients leads to flowmeter errors at the higher-flow values even in the case where the fundamental mode is the only mode excited. It is also deduced that flowmeter errors in general depend on the distance between transducers A and B whether temperature gradients exist or not. This conclusion is not reflected in the usual definition of flowmeter errors given by the so-called mode-dependent deviation of measurement introduced in earlier works. PMID:12565074

  9. Altitude precipitation gradient in Serbia

    Directory of Open Access Journals (Sweden)

    Živković Nenad M.

    2004-01-01

    Full Text Available Using average annual precipitations data for period 1961-90. from all rain gauges in Serbia, southern of Sava and Danube rivers, the map of altitude precipitations gradient is constructed. 59 regions homogeneous for relation X=f(H are obtained by regression analysis method (two-dimensional type, X precipitation height and H - altitude. Some new method are applied, some limitations are shown, some regularities are found in disposition of precipitation growth and it is indicated on practical application of this method in physico-geographical research.

  10. Gradient Clogging in Depth Filtration

    OpenAIRE

    Datta, S.; Redner, S.

    1998-01-01

    We investigate clogging in depth filtration, in which a dirty fluid is ``cleaned'' by the trapping of dirt particles within the pore space during flow through a porous medium. This leads to a gradient percolation process which exhibits a power law distribution for the density of trapped particles at downstream distance x from the input. To achieve a non-pathological clogging (percolation) threshold, the system length L should scale no faster than a power of ln w, where w is the width. Non-tri...

  11. Separation of colloidal two dimensional materials by density gradient ultracentrifugation

    International Nuclear Information System (INIS)

    Two-dimensional (2D) materials have been made through various approaches but obtaining monodispersed simply by synthesis optimization gained little success, which highlighted the need for introducing nanoseparation methods. Density gradient ultracentrifugation method has emerged as a versatile and scalable method for sorting colloidal 2D nanomaterials. Isopycnic separation was applied on thickness-dependent separation of graphene nanosheets. And rate-zonal separation, as a more versatile separation method, demonstrated its capability in sorting nanosheets of chemically modified single layered graphene, layered double hydroxide, and even metallic Ag. Establishing such density gradient ultracentrifugation method not only achieves monodispersed nanosheets and provides new opportunities for investigation on size dependent properties of 2D materials, but also makes the surface modification possible by introducing “reaction zones” during sedimentation of the colloids. - Graphical abstract: Two-dimensional (2D) materials have been made through various approaches but obtaining monodispersed simply by synthesis optimization gained little success, which highlighted the need for introducing nanoseparation methods. Density gradient ultracentrifugation method has emerged as a versatile and scalable method for sorting colloidal 2D nanomaterials according to their size of thickness difference. Establishing such density gradient ultracentrifugation method not only achieves monodispersed nanosheets and provides new opportunities for investigation on size dependent properties of 2D materials, but also makes the surface modification possible by introducing “reaction zones” during sedimentation of the colloids. - Highlights: • Density gradient ultracentrifugation was applied on size separation of 2D material. • Isopycnic separation was applied on separation of low density materials. • Rate-zonal separation was applied on separation of large density materials. • Size

  12. Active Chemical Sampling System for Underwater Chemical Source Localization

    OpenAIRE

    Ryuichi Takemura; Hiromi Sakata; Hiroshi Ishida

    2016-01-01

    This paper investigates the effect of active water sampling to enhance chemical reception for small underwater robots. The search for a chemical source in a stagnant water environment is not an easy task because the chemical solution released from the source stays in the close vicinity of the source. No signal is obtained even if a robot with chemical sensors is placed a few centimeters from the chemical source. In the system under study, four electrochemical sensors are aligned in front of a...

  13. Advantages of horizontal directional Theta method to detect the edges of full tensor gravity gradient data

    Science.gov (United States)

    Yuan, Yuan; Gao, Jin-Yao; Chen, Ling-Na

    2016-07-01

    Full tensor gravity gradient data contain nine signal components. They include higher frequency signals than traditional gravity data, which can extract the small-scale features of the sources. Edge detection has played an important role in the interpretation of potential-field data. There are many methods that have been proposed to detect and enhance the edges of geological bodies based on horizontal and vertical derivatives of potential-field data. In order to make full use of all the measured gradient components, we need to develop a new edge detector to process the full tensor gravity gradient data. We first define the directional Theta and use the horizontal directional Theta to define a new edge detector. This method was tested on synthetic and real full tensor gravity gradient data to validate its feasibility. Compared the results with other balanced detectors, the new detector can effectively delineate the edges and does not produce any additional false edges.

  14. Strain gradient effects on cyclic plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Legarth, Brian Nyvang

    2010-01-01

    Size effects on the cyclic shear response are studied numerically using a recent higher order strain gradient visco-plasticity theory accounting for both dissipative and energetic gradient hardening. Numerical investigations of the response under cyclic pure shear and shear of a finite slab between...... rigid platens have been carried out, using the finite element method. It is shown for elastic–perfectly plastic solids how dissipative gradient effects lead to increased yield strength, whereas energetic gradient contributions lead to increased hardening as well as a Bauschinger effect. For linearly...... hardening materials it is quantified how dissipative and energetic gradient effects promote hardening above that of conventional predictions. Usually, increased hardening is attributed to energetic gradient effects, but here it is found that also dissipative gradient effects lead to additional hardening in...

  15. Observation of single neutral atoms in a large-magnetic-gradient vapour-cell magneto-optical trap

    Institute of Scientific and Technical Information of China (English)

    Wang Jing; He Jun; Qiu Ying; Yang Bao-Dong; Zhao Jiang-Yan; Zhang Tian-Cai; Wang Jun-Min

    2008-01-01

    Single caesium atoms in a large-magnetic-gradient vapour-cell magneto-optical trap have been identified. The trapping of individual atoms is marked by the steps in fluorescence signal corresponding to the capture or loss of single atoms. The typical magnetic gradient is about 29 mT/cm, which evidently reduces the capture rate of magneto-optical trap.

  16. An assessment of an environmental gradient using coral geochemical records, Whitsunday Islands, Great Barrier Reef, Australia

    International Nuclear Information System (INIS)

    Coral cores were collected along an environmental and water quality gradient through the Whitsunday Island group, Great Barrier Reef (Australia), for trace element and stable isotope analysis. The primary aim of the study was to examine if this gradient could be detected in coral records and, if so, whether the gradient has changed over time with changing land use in the adjacent river catchments. Y/Ca was the trace element ratio which varied spatially across the gradient, with concentrations progressively decreasing away from the river mouths. The Ba/Ca and Y/Ca ratios were the only indicators of change in the gradient through time, increasing shortly after European settlement. The Mn/Ca ratio responded to local disturbance related to the construction of tourism infrastructure. Nitrogen isotope ratios showed no apparent trend over time. This study highlights the importance of site selection when using coral records to record regional environmental signals.

  17. Simulation of concomitant magnetic fields on fast switched gradient coils used in advanced application of MRI

    Science.gov (United States)

    Salinas-Muciño, G.; Torres-García, E.; Hidalgo-Tobon, S.

    2012-10-01

    The process to produce an MR image includes nuclear alignment, RF excitation, spatial encoding, and image formation. To form an image, it is necessary to perform spatial localization of the MR signals, which is achieved using gradient coils. MRI requires the use of gradient coils that generate magnetic fields, which vary linearly with position over the imaging volume. Safety issues have been a motivation to study deeply the relation between the interaction of gradient magnetic field and the peripheral nerve stimulation. In this work is presented a numerical modeling between the concomitant magnetic fields produced by the gradient coils and the electric field induced in a cube with σ conductivity by the gradient field switching in pulse sequences as Eco planar Imaging (EPI), due to this kind of sequence is the most used in advance applications of magnetic resonance imaging as functional MRI, cardiac imaging or diffusion.

  18. Wettability-gradient-driven micropump for transporting discrete liquid drops

    International Nuclear Information System (INIS)

    In this paper, we report our efforts toward building a microelectromechanical system-based micropump. The micropump is driven by a wettability gradient and used to transport discrete drops. The gradient in wettability is distributed axisymmetrically, with hydrophobicity of the micropump surface decreasing radially toward the center. Both physical and chemical properties of the surface are altered to obtain the wettability gradient needed for driving the drops. The surface of the micropump is, first, patterned with pre-designed micro-features that define the roughness of the surface and, then, coated with a low-energy interface film. Results show that drops deposited on the surface of the micropump move, in a directional way, along the wettability gradient. The average velocity of the deposited drops is 5 mm s−1. Measured contact angles decrease gradually from 157.0° to 124.2° toward the center of the micropump surface. Maximum driving force exerted by the solid surface on the drops is 12.82 µN. The average size of the drops transported on the surface of the micropump is 2 µL. (paper)

  19. On the thermal gradient in the Earth's deep interior

    Directory of Open Access Journals (Sweden)

    M. Tirone

    2015-09-01

    Full Text Available Temperature variations in large portions of the mantle are mainly controlled by the reversible and irreversible transformation of mechanical energy related to pressure and viscous forces into internal energy along with diffusion of heat and chemical reactions. The simplest approach to determine the temperature gradient is to assume that the dynamic process involved is adiabatic and reversible, which means that entropy remains constant in the system. However heat conduction and viscous dissipation during dynamic processes effectively create entropy. The adiabatic and non-adiabatic temperature variation under the influence of a constant or varying gravitational field are discussed in this study from the perspective of the Joule–Thomson (JT throttling system in relation to the transport equation for change of entropy. The JT model describes a dynamic irreversible process in which entropy in the system increases but enthalpy remains constant (at least in an equipotential gravitational field. A comparison is made between the thermal gradient from the JT model and the thermal gradient from two models, a mantle convection and a plume geodynamic model coupled with thermodynamics including a complete description of the entropy variation. The results show that the difference is relatively small and suggests that thermal structure of the asthenospheric mantle can be well approximated by an isenthalpic model when the formulation includes the effect of the gravitational field. For non-dynamic or parameterized mantle dynamic studies the JT formulation provides a better description of the thermal gradient than the classic isentropic formulation.

  20. NGC 55: a disc galaxy with flat abundance gradients

    CERN Document Server

    Magrini, Laura; Vajgel, Bruna

    2016-01-01

    We present new spectroscopic observations obtained with GMOS@Gemini-S of a sample of 25 hii regions located in NGC 55, a late-type galaxy in the nearby Sculptor group. We derive physical conditions and chemical composition through the te-method for 18 hii regions, and strong-line abundances for 22 hii regions. We provide abundances of He, O, N, Ne, S, Ar, finding a substantially homogenous composition in the ionised gas of the disc of NGC 55, with no trace of radial gradients. The oxygen abundances, both derived with \\te- and strong-line methods, have similar mean values and similarly small dispersion: 12+$\\log$(O/H)=8.13$\\pm$0.18~dex with the former and 12+$\\log$(O/H)=8.17$\\pm$0.13~dex with the latter. The average metallicities and the flat gradients agree with previous studies of smaller samples of \\hii\\ regions and there is a qualitative agreement with the blue supergiant radial gradient as well. We investigate the origin of such flat gradients comparing NGC 55 with NGC 300, its companion galaxy, which is ...

  1. On the thermal gradient in the Earth's deep interior

    Science.gov (United States)

    Tirone, M.

    2016-02-01

    Temperature variations in large portions of the mantle are mainly controlled by the reversible and irreversible transformation of mechanical energy related to pressure and viscous forces into internal energy along with diffusion of heat and chemical reactions. The simplest approach to determine the temperature gradient is to assume that the dynamic process involved is adiabatic and reversible, which means that entropy remains constant in the system. However, heat conduction and viscous dissipation during dynamic processes effectively create entropy. The adiabatic and non-adiabatic temperature variation under the influence of a constant or varying gravitational field are discussed in this study from the perspective of the Joule-Thomson (JT) throttling system in relation to the transport equation for change of entropy. The JT model describes a dynamic irreversible process in which entropy in the system increases but enthalpy remains constant (at least in an equipotential gravitational field). A comparison is made between the thermal gradient from the JT model and the thermal gradient from two models, a mantle convection and a plume geodynamic model, coupled with thermodynamics including a complete description of the entropy variation. The results show that the difference is relatively small and suggests that thermal structure of the asthenospheric mantle can be well approximated by an isenthalpic model when the formulation includes the effect of the gravitational field. For non-dynamic or parameterized mantle dynamic studies, the JT formulation provides a better description of the thermal gradient than the classic isentropic formulation.

  2. Climate change and frog calls: long-term correlations along a tropical altitudinal gradient

    OpenAIRE

    Narins, Peter M.; Meenderink, Sebastiaan W. F.

    2014-01-01

    Temperature affects nearly all biological processes, including acoustic signal production and reception. Here, we report on advertisement calls of the Puerto Rican coqui frog (Eleutherodactylus coqui) that were recorded along an altitudinal gradient and compared these with similar recordings along the same altitudinal gradient obtained 23 years earlier. We found that over this period, at any given elevation, calls exhibited both significant increases in pitch and shortening of their duration....

  3. Structure and properties of sintered tool gradient materials

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2010-12-01

    Full Text Available Purpose: The main objective of the presented is to elaborate the fabrication technology of novel sintered tool gradient materials on the basis of hard wolfram carbide phase with cobalt binding phase, and to carry out research studies on the structure and properties of the newly elaborated sintered tool gradient materials.Design/methodology/approach: The following research studies have been carried out to elaborate a new group of sintered tool gradient materials, wolfram carbide with cobalt matrix, to elaborate their fabrication technology and to determine their structure and properties: a fabrication technology of mixtures and the formation technology of wolfram carbide gradient materials with cobalt matrix WC-Co was applied and elaborated; sintering conditions were selected experimentally: time, temperature and sintering atmosphere as well as isostatic condensation, ensuring the best structure and properties; phase and chemical composition of the sintered gradient WC-Co materials was determined using EDX, EBSD methods and qualitative X-ray analysis; the structure of sintered gradient WC-Co materials was investigated using scanning microscopy and transmission electron microscopy; mechanical and physical properties of sintered gradient WC-Co materials was determined: porosity, density, hardness, resistance to abrasive wear, resistance to brittle cracking.Findings: The presented research results confirm that the newly elaborated technology of powder metallurgy, which consists in sequential coating of the moulding with layers having the increasing content of carbides and decreasing concentration of cobalt, and then sintering such a compact, ensures the acquisition of the required structure and properties, including the resistance to cracking and abrasive wear of tool gradient materials, due to earned high hardness and resistance to abrasive wear on the surface as well as high resistance to cracking in the core of the materials fabricated in such a

  4. Capacity gradient anion chromatography with a borate complex as eluent.

    Science.gov (United States)

    Yamamoto, A; Inoue, Y; Kodama, S; Matsunaga, A

    1999-07-30

    Complex formation between borate compounds and vicinal diols is well recognized. Generally, in a chemically bonded anion-exchange resin, many hydroxyl groups are introduced on the surface of the resin in order to make the resin hydrophilic. The borate as an eluting reagent also reacts to these hydroxyl groups, and this complex formation decreases the apparent ion-exchange capacity of the column by being dissociated to the anion depending on the eluent pH. In the present work a method is described for the simultaneous determination of anions based on the capacity gradient for suppressed ion chromatography. A Tosoh IC-Anion-PW column and dihydroxyphenylborane-mannitol eluent system were used. To maintain baseline stability, it was helpful to keep the borate concentration constant during a gradient of 16 to 0 mM mannitol as a modifier to prevent the complex formation with the hydroxyl on the resin. The chemical composition of the eluents and gradient profiles are discussed and the application to the analysis of the condensed phosphates with widely varying retention times as food additives in a cheese sample is presented. PMID:10457467

  5. Strength gradient enhances fatigue resistance of steels

    Science.gov (United States)

    Ma, Zhiwei; Liu, Jiabin; Wang, Gang; Wang, Hongtao; Wei, Yujie; Gao, Huajian

    2016-02-01

    Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch’s tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility.

  6. Engineering in vivo gradients of sphingosine-1-phosphate receptor ligands for localized microvascular remodeling and inflammatory cell positioning

    OpenAIRE

    Ogle, Molly E.; Sefcik, Lauren S.; Awojoodu, Anthony O.; Chiappa, Nathan F.; Lynch, Kevin; Peirce-Cottler, Shayn; BOTCHWEY, EDWARD A.

    2014-01-01

    Biomaterial-mediated controlled release of soluble signaling molecules is a tissue engineering approach to spatially control processes of inflammation, microvascular remodeling, and host cell recruitment and to generate biochemical gradients in vivo. Lipid mediators, such as sphingosine 1-phosphate (S1P), are recognized for their essential roles in spatial guidance, signaling, and highly regulated endogenous gradients. S1P and pharmacological analogs such as FTY720 are therapeutically attract...

  7. The electric field gradient in fluorides

    International Nuclear Information System (INIS)

    The electric quadrupole hyperfine interaction was investigated for various fluorides by the time-differential observation of the perturbed γ angular correlation and the Kern-Hanle effect of the 197 keV radiation of the 5/2+ level in 19F. This level was excited by inelastic proton scattering. The dependence of the quadrupole coupling constant from the chemical bond of the atom to its ligands was measured in fluorides of two-valid transition elements and in pureley covalent molecules, as (CF2)sub(n) or SF6. The influence of radiation-induced defects in nonmetals was investigated for cubic fluorides between 80 K and 1050 K. For CaF2 two different field gradients are obtained with coupling constants between 27 MHz and 3 MHz. By measurements of the angular distribution for CaF2/PrF3 mixed crystals which contain a variable concentration of F- interstitials was shown that the appearance of the 3 MHz frequency is correlated with the concentration of F- interstitials in CaF2. (BHO)

  8. Systematics of the gradient on the resonant core-hole state

    OpenAIRE

    Takahashi, Osamu; Matsui, Takayuki; Kawano, Aiko; Tabayashi, Kiyohiko; Yamasaki, Katsuyoshi

    2007-01-01

    Systematics of the gradient on the resonant core-hole state in the Franck-Condon region were investigated theoretically. The steepest gradient for a target bond in the resonant core-excited states becomes more negative with increasing sum of atomic numbers of the atom in the bonded pair and increasing bond order for the associated chemical bond. Gradients for molecules that include conjugated double bonds such as butadiene and hexatriene were also examined at the lowest core-hole state. The g...

  9. Emerging Trends in Retrograde Signaling.

    Science.gov (United States)

    Suvarna, Yashasvi; Maity, Nivedita; Shivamurthy, M C

    2016-05-01

    Retrograde signaling is defined as the signaling events leading from the plastids to the nucleus in plants and across the chemical synapse, from the postsynaptic neuron to the presynaptic neuron in animals. The discovery of various retrograde messengers has opened many avenues and clouds of thoughts as to the role of retrograde signaling. They have been implicated particularly in long-term potentiation (LTP) and synaptic plasticity. But the basic assumptions about retrograde signaling have not been studied upon for many years. This review focuses on established facts and hypothesis put forward in retrograde signaling. PMID:26081150

  10. The chemical ecology of cyanobacteria

    OpenAIRE

    Pedro N. Leão; Engene, Niclas; Antunes, Agostinho; Gerwick, William H; Vasconcelos, Vitor

    2012-01-01

    This review covers the literature on the chemically mediated ecology of cyanobacteria, including ultraviolet radiation protection, feeding-deterrence, allelopathy, resource competition, and signalling. To highlight the chemical and biological diversity of this group of organisms, evolutionary and chemotaxonomical studies are presented. Several technologically relevant aspects of cyanobacterial chemical ecology are also discussed.

  11. Emergent collective chemotaxis without single-cell gradient sensing

    CERN Document Server

    Camley, Brian A; Levine, Herbert; Rappel, Wouter-Jan

    2015-01-01

    Many eukaryotic cells chemotax, sensing and following chemical gradients. However, even if single cells do not chemotax significantly, small clusters may still follow a gradient; this behavior is observed in neural crest cells and during border cell migration in Drosophila, but its origin remains puzzling. Here, we study this "collective guidance" analytically and computationally. We show collective chemotaxis can exist without single-cell chemotaxis if contact inhibition of locomotion (CIL), where cells polarize away from cell-cell contact, is regulated by the chemoattractant. We present explicit formulas for how cluster velocity and chemotactic index depend on the number and organization of cells in the cluster. Pairs of cells will have velocities that are strongly dependent on the cell pair's orientation: this provides a simple test for the presence of collective guidance in neural crest cells and other systems. We also study cluster-level adaptation, amplification, and cohesion via co-attraction.

  12. Chemical Emergencies

    Science.gov (United States)

    When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...

  13. Nanofiber Scaffold Gradients for Interfacial Tissue Engineering

    OpenAIRE

    Ramalingam, Murugan; Young, Marian F.; Thomas, Vinoy; Sun, Limin; Chow, Laurence C.; Tison, Christopher K.; Chatterjee, Kaushik; Miles, William C.; Simon, Carl G.

    2012-01-01

    We have designed a 2-spinnerette device that can directly electrospin nanofiber scaffolds containing a gradient in composition that can be used to engineer interfacial tissues such as ligament and tendon. Two types of nanofibers are simultaneously electrospun in an overlapping pattern to create a nonwoven mat of nanofibers containing a composition gradient. The approach is an advance over previous methods due to its versatility - gradients can be formed from any materials that can be electros...

  14. Interpretation of the reduced density gradient

    OpenAIRE

    Boto, Roberto A.; Contreras-García, Julia; Tierny, Julien; Piquemal, Jean-Philip

    2015-01-01

    An interpretation of the reduced density gradient in terms of the bosonic kinetic energy density is presented. Contrary to other bonding indicators based on the kinetic energy density such as the localised orbital locator (LOL) or the electron localization function (ELF), the reduced density gradient is not only able to identify covalent bondings, but also ionic and non-covalent interactions. This study reveals that the critical points of the reduced density gradient are closely connected wit...

  15. Temperature gradient sensor based on CNT composite

    International Nuclear Information System (INIS)

    This work describes fabrication and investigation of thin film temperature gradient sensor based on the composite of carbon nano-tubes (CNT) and polymer adhesive. The dependences of the voltage, current and Seebeck coefficient of the sensor upon gradient of temperature were measured. It was observed that with increase of temperature gradient, the voltage and current of the sensor increase while the Seebeck coefficient decreases.

  16. Methods of preparing polymeric gradient composites

    OpenAIRE

    A. Dybowska; J. Stabik

    2007-01-01

    Purpose: The goal of this work is to introduce basic methods of preparing polymeric gradient materials, which allow to join two different components to ensure the required properties and structure of the functionally gradient materials.Design/methodology/approach: In this paper few of methods of preparing functionally gradient polymeric materials are briefly described which were successful employed in many investigations performed during last few years.Findings: It was noticed that the knowle...

  17. Temperature gradient sensor based on CNT composite

    Energy Technology Data Exchange (ETDEWEB)

    Karimov, Khasan S. [GIK Institute of Engineering Sciences and Technology, Topi, Swabi, KPK 23640 (Pakistan); Center for Innovative Development of Science and New Technologies of Academy of Sciences, Rudaki Ave.33, Dushanbe 734025 (Tajikistan); Abid, Muhammad [GIK Institute of Engineering Sciences and Technology, Topi, Swabi, KPK 23640 (Pakistan); Saleem, Muhammad, E-mail: msaleem108@hotmail.com [GIK Institute of Engineering Sciences and Technology, Topi, Swabi, KPK 23640 (Pakistan); Department of Physics, Government College of Science, Wahdat Road, Lahore 54570 (Pakistan); Akhmedov, Khakim M. [Center for Innovative Development of Science and New Technologies of Academy of Sciences, Rudaki Ave.33, Dushanbe 734025 (Tajikistan); Bashir, Muhammad M. [GIK Institute of Engineering Sciences and Technology, Topi, Swabi, KPK 23640 (Pakistan); Shafique, Umar [Electrical and Computer Engineering Department, Nano Technology Program, University of Waterloo (Canada); Ali, Muhammad M. [GIK Institute of Engineering Sciences and Technology, Topi, Swabi, KPK 23640 (Pakistan)

    2014-08-01

    This work describes fabrication and investigation of thin film temperature gradient sensor based on the composite of carbon nano-tubes (CNT) and polymer adhesive. The dependences of the voltage, current and Seebeck coefficient of the sensor upon gradient of temperature were measured. It was observed that with increase of temperature gradient, the voltage and current of the sensor increase while the Seebeck coefficient decreases.

  18. Spatiotemporal Gradient Analysis of Differential Microphone Arrays

    OpenAIRE

    Kolundzija, Mihailo; Faller, Christof; Vetterli, Martin

    2011-01-01

    The literature on gradient and differential microphone arrays makes a distinction between the two types, and nevertheless shows how both types can be used to obtain the same directional responses. A more theoretically sound rationale for using delays in differential microphone arrays has not yet been given. This paper presents a gradient analysis of the sound field viewed as a spatio-temporal phenomenon, and gives a theoretical interpretation of the working principles of gradient and differen...

  19. Novel Techniques for Pulsed Field Gradient NMR Measurements

    Science.gov (United States)

    Brey, William Wallace

    Pulsed field gradient (PFG) techniques now find application in multiple quantum filtering and diffusion experiments as well as in magnetic resonance imaging and spatially selective spectroscopy. Conventionally, the gradient fields are produced by azimuthal and longitudinal currents on the surfaces of one or two cylinders. Using a series of planar units consisting of azimuthal and radial current elements spaced along the longitudinal axis, we have designed gradient coils having linear regions that extend axially nearly to the ends of the coil and to more than 80% of the inner radius. These designs locate the current return paths on a concentric cylinder, so the coils are called Concentric Return Path (CRP) coils. Coils having extended linear regions can be made smaller for a given sample size. Among the advantages that can accrue from using smaller coils are improved gradient strength and switching time, reduced eddy currents in the absence of shielding, and improved use of bore space. We used an approximation technique to predict the remaining eddy currents and a time-domain model of coil performance to simulate the electrical performance of the CRP coil and several reduced volume coils of more conventional design. One of the conventional coils was designed based on the time-domain performance model. A single-point acquisition technique was developed to measure the remaining eddy currents of the reduced volume coils. Adaptive sampling increases the dynamic range of the measurement. Measuring only the center of the stimulated echo removes chemical shift and B_0 inhomogeneity effects. The technique was also used to design an inverse filter to remove the eddy current effects in a larger coil set. We added pulsed field gradient and imaging capability to a 7 T commercial spectrometer to perform neuroscience and embryology research and used it in preliminary studies of binary liquid mixtures separating near a critical point. These techniques and coil designs will find

  20. The stellar metallicity gradients in galaxy discs in a cosmological scenario

    CERN Document Server

    Tissera, Patricia B; Sánchez-Blázquez, Patricia; Pedrosa, Susana E; Sánchez, Sebastián F; Snaith, Owain N; Vilchez, José M

    2016-01-01

    The stellar metallicity gradients of disc galaxies provide information on the disc assembly, star formation processes and chemical evolution. They also might store information on dynamical processes which could affect the distribution of chemical elements in the gas-phase and the stellar components. We studied the stellar metallicity gradients of stellar discs in a cosmological simulation. We explored the dependence of the stellar metallicity gradients on stellar age and the size and mass of the stellar discs. We used galaxies selected from a cosmological hydrodynamical simulation performed including a physically-motivated Supernova feedback and chemical evolution. The metallicity profiles were estimated for stars with different ages. We confront our numerical findings with results from the CALIFA Survey. The simulated stellar discs are found to have metallicity profiles with slopes in global agreement with observations. Low stellar-mass galaxies tend to have a larger variety of metallicity slopes. When norma...

  1. STOCHASTIC GRADIENT METHODS FOR UNCONSTRAINED OPTIMIZATION

    Directory of Open Access Journals (Sweden)

    Nataša Krejić

    2014-12-01

    Full Text Available This papers presents an overview of gradient based methods for minimization of noisy functions. It is assumed that the objective functions is either given with error terms of stochastic nature or given as the mathematical expectation. Such problems arise in the context of simulation based optimization. The focus of this presentation is on the gradient based Stochastic Approximation and Sample Average Approximation methods. The concept of stochastic gradient approximation of the true gradient can be successfully extended to deterministic problems. Methods of this kind are presented for the data fitting and machine learning problems.

  2. Wireless SAW Based Temperature Gradient Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Prime Photonics proposes design and development of a surface acoustic wave (SAW) based temperature gradient sensor for instrumentation of thermal protection systems...

  3. INFLUENCES OF SLOPE GRADIENT ON SOIL EROSION

    Institute of Scientific and Technical Information of China (English)

    刘青泉; 陈力; 李家春

    2001-01-01

    The main factors influencing soil erosion include the net rain excess, the water depth, the velocity, the shear stress of overland flows , and the erosion-resisting capacity of soil. The laws of these factors varying with the slope gradient were investigated by using the kinematic wave theory. Furthermore, the critical slope gradient of erosion was driven. The analysis shows that the critical slope gradient of soil erosion is dependent on grain size , soil bulk density , surface roughness, runoff length, net rain excess, and the friction coefficient of soil, etc. The critical slope gradient has been estimated theoretically with its range between 41. 5 °~ 50°.

  4. Bacterial Response to Antibiotic Gradients in a Porous Microfluidic Device

    Science.gov (United States)

    Deng, J.; Shechtman, L. A.; Sanford, R. A.; Dong, Y.; Werth, C. J.; Fouke, B. W.

    2015-12-01

    Microorganisms in nature have evolved survival strategies to cope with a wide variety of environmental stresses, including gradients in temperature, pH, substrate availability and aqueous chemistry. Microfluidic devices provide a consistently reliable real-time means to quantitatively measure, control and reproduce the dynamic nature of these stresses. As an example, accelerated adaptation from genetic mutations have been observed in E. coli as it responds to gradients of Ciprofloxacin (Zhang et. al. 2011). However, the mechanisms by which bacteria respond to antibiotic gradients, as well as the effect of changes in how the stressor is applied, have not been systematically studied. In this study, newly designed and fabricated microfluidic devices with porous media have been utilized to determine the chemical stress fields that enhance adaptation and thus to test how E. coli bacterial communities adapt to antibiotic stresses. By applying antibiotic and nutrient into inlet channels adjacent to either side of the porous media inoculated with E. coli, a gradient of antibiotic was formed. Hydrogel barriers were selectively photo-polymerized in between of the inlet channels and the porous media to prevent any undesired convection. Hence, chemical solute can only be transported by diffusion, creating a reproducible antibiotic gradient over the porous media. The bacteria were also constrained by the hydrogel boundary barriers from escaping the porous media. Preliminary results suggest that E. coli moves freely with respect to Ciprofloxacin concentrations. In addition, and unexpectedly, the E. coli colonies exhibit a concentric pulsed growth front radiating away from the point of inoculation within the micromodel ecosystem and pulse over the porous media containing antibiotic. The bacteria at the growth front grow into long filaments (up to 100μm) while the bacteria in the inner concentric area are normal size. We hypothesize that the frontier bacteria, which are first

  5. Diffusion imaging with stimulated echoes: signal models and experiment design

    CERN Document Server

    Alexander, Daniel C

    2013-01-01

    Purpose: Stimulated echo acquisition mode (STEAM) diffusion MRI can be advantageous over pulsed-gradient spin-echo (PGSE) for diffusion times that are long compared to $\\ttwo$. It is important therefore for biomedical diffusion imaging applications at 7T and above where $\\ttwo$ is short. However, imaging gradients in the STEAM sequence contribute much greater diffusion weighting than in PGSE, but are often ignored during post-processing. We demonstrate here that this can severely bias parameter estimates. Method: We present models for the STEAM signal for free and restricted diffusion that account for crusher and slice-select (butterfly) gradients to avoid such bias. The butterfly gradients also disrupt experiment design, typically by skewing gradient-vectors towards the slice direction. We propose a simple compensation to the diffusion gradient vector specified to the scanner that counterbalances the butterfly gradients to preserve the intended experiment design. Results: High-field data fixed monkey brain e...

  6. Monitoring presence of chemical agents

    International Nuclear Information System (INIS)

    The specification describes a case for use with a hand-portable chemical agent detector for continuously monitoring an atmosphere for the presence of predetermined chemical agents. The detector having means for ionizing air samples and providing at an output terminal electrical signals representative of the mobility spectrum of ionized chemical vapours produced by the ionizing means. The case comprises means for defining a chamber in the case for supporting and removably enclosing the detector, means for communicating ambient atmosphere to the chamber, electrical circuit means in the case, the circuit means being adapted to be detachably connected to the detector output terminal when the detector is positioned in the chamber and being responsive to the electrical signals for producing an alarm signal when the signals detect a chemical agent concentration in the atmosphere exceeding a predetermined concentration level, and alarm means responsive to the alarm signal. (author)

  7. MRI appearances of the asymptomatic patellar tendon on gradient echo imaging

    International Nuclear Information System (INIS)

    Thickening of the patellar tendon and foci of increased signal intensity have been described as characteristic features of ''jumper's knee'' (chronic patellar tendinitis) on magnetic resonance imaging (MRI). It was our impression that such appearances may be seen in the patellar tendons of patients without symptoms referable to the anterior part of the knee when using gradient echo images. The appearances of the asymptomatic patellar tendon on three-dimensional gradient echo sequences were studied by retrospectively reviewing the images of 60 patients, none of whom had symptoms related to the anterior part of the knee. The anteroposterior width of the patellar tendon was measured at three levels (superior, middle and inferior) on the central sagittal image of a gradient echo sequence. The relative signal intensities at the same levels were recorded. In 97% of subjects the superior part of the tendon was wider than the midpoint, and in 97% the inferior part was wider than the midpoint. The range of widths was wide, and there was no significant difference between sexes. Focal increased signal intensity in the superior part was shown in 75%, and in the inferior part in 43%. The asymptomatic patellar tendon shows uniform thickness throughout most of its length, but there are focal expansions at the proximal and distal ends. It usually demonstrates low signal on MRI, but may contain foci of increased signal intensity at either or both ends when imaged on gradient-echo sequences. (orig.)

  8. MRI appearances of the asymptomatic patellar tendon on gradient echo imaging

    Energy Technology Data Exchange (ETDEWEB)

    Reiff, D.B. [Dept. of Diagnostic Radiology, St. George`s Hospital, London (United Kingdom); Heenan, S.D. [Dept. of Diagnostic Radiology, St. George`s Hospital, London (United Kingdom); Heron, C.W. [Dept. of Diagnostic Radiology, St. George`s Hospital, London (United Kingdom)

    1995-02-01

    Thickening of the patellar tendon and foci of increased signal intensity have been described as characteristic features of ``jumper`s knee`` (chronic patellar tendinitis) on magnetic resonance imaging (MRI). It was our impression that such appearances may be seen in the patellar tendons of patients without symptoms referable to the anterior part of the knee when using gradient echo images. The appearances of the asymptomatic patellar tendon on three-dimensional gradient echo sequences were studied by retrospectively reviewing the images of 60 patients, none of whom had symptoms related to the anterior part of the knee. The anteroposterior width of the patellar tendon was measured at three levels (superior, middle and inferior) on the central sagittal image of a gradient echo sequence. The relative signal intensities at the same levels were recorded. In 97% of subjects the superior part of the tendon was wider than the midpoint, and in 97% the inferior part was wider than the midpoint. The range of widths was wide, and there was no significant difference between sexes. Focal increased signal intensity in the superior part was shown in 75%, and in the inferior part in 43%. The asymptomatic patellar tendon shows uniform thickness throughout most of its length, but there are focal expansions at the proximal and distal ends. It usually demonstrates low signal on MRI, but may contain foci of increased signal intensity at either or both ends when imaged on gradient-echo sequences. (orig.)

  9. Adjustable, rapidly switching microfluidic gradient generation using focused travelling surface acoustic waves

    Energy Technology Data Exchange (ETDEWEB)

    Destgeer, Ghulam; Im, Sunghyuk; Hang Ha, Byung; Ho Jung, Jin; Ahmad Ansari, Mubashshir; Jin Sung, Hyung, E-mail: hjsung@kaist.ac.kr [Department of Mechanical Engineering, KAIST, 291 Daejak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2014-01-13

    We demonstrate a simple device to generate chemical concentration gradients in a microfluidic channel using focused travelling surface acoustic waves (F-TSAW). A pair of curved interdigitated metal electrodes deposited on the surface of a piezoelectric (LiNbO{sub 3}) substrate disseminate high frequency sound waves when actuated by an alternating current source. The F-TSAW produces chaotic acoustic streaming flow upon its interaction with the fluid inside a microfluidic channel, which mixes confluent streams of chemicals in a controlled fashion for an adjustable and rapidly switching gradient generation.

  10. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2002-01-01

    By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter the...

  11. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2003-01-01

    By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter the...

  12. On 4-dimensional gradient shrinking solitons

    OpenAIRE

    Ni, Lei; Wallach, Nolan

    2007-01-01

    In this paper we classify the four dimensional gradient shrinking solitons under certain curvature conditions satisfied by all solitons arising from finite time singularities of Ricci flow on compact four manifolds with positive isotropic curvature. As a corollary we generalize a result of Perelman on three dimensional gradient shrinking solitons to dimension four.

  13. Microinstabilities in weak density gradient tokamak systems

    International Nuclear Information System (INIS)

    A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient

  14. Efron's curvature of the structural gradient model

    OpenAIRE

    SEI, Tomonari

    2010-01-01

    The structural gradient model is a multivariate statistical model in order to extract various interactions of given data set. In this note, we show that Efron's statistical curvature of the structural gradient model is less than that of a competitive mixture model under a null hypothesis.

  15. Newton's method in the context of gradients

    Directory of Open Access Journals (Sweden)

    John W. Neuberger

    2007-09-01

    Full Text Available This paper gives a common theoretical treatment for gradient and Newton type methods for general classes of problems. First, for Euler-Lagrange equations Newton's method is characterized as an (asymptotically optimal variable steepest descent method. Second, Sobolev gradient type minimization is developed for general problems using a continuous Newton method which takes into account a "boundary condition" operator.

  16. An Inexpensive Digital Gradient Controller for HPLC.

    Science.gov (United States)

    Brady, James E.; Carr, Peter W.

    1983-01-01

    Use of gradient elution techniques in high performance liquid chromatography (HPLC) is often essential for direct separation of complex mixtures. Since most commercial controllers have features that are of marginal value for instructional purposes, a low-cost controller capable of illustrating essential features of gradient elution was developed.…

  17. Open-gradient magnetic separation for physical coal cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Doctor, R.D.; Livengood, C.D.

    1990-01-01

    Open-Gradient Magnetic Separation (OGMS) using superconducting quadrupole magnets offers a novel beneficiation technology for removing pyritic sulfur from pulverized dry coal. It is estimated to have a power demand 75% lower than techniques using conventional electromagnets, while achieving higher separation forces. Additionally, the system operates in a continuous mode and uses no chemicals. Because OGMS is specifically applicable to finely ground coal (120--325 mesh), its development could encourage the commercialization of other unconventional coal technologies, such as coal-water slurries, fluidized-bed combustion, and synfuels. 3 figs., 1 tab.

  18. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    International Nuclear Information System (INIS)

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k (perpendicular) ρs ∼< 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  19. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Y; Mazzucato, E; Guttenfelder, W; Bell, R E; Domier, C W; LeBlanc, B P; Lee, K C; Luhmann Jr, N C; Smith, D R

    2011-03-21

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k⊥ρs ≤10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  20. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects of grad...... gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly.......Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects of...

  1. Dual fuel gradients in uranium silicide plates

    Energy Technology Data Exchange (ETDEWEB)

    Pace, B.W. [Babock and Wilcox, Lynchburg, VA (United States)

    1997-08-01

    Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final core gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.

  2. Stellar Metallicity Gradients in SDSS galaxies

    CERN Document Server

    Roig, Benjamin; Yan, Renbin

    2015-01-01

    We infer stellar metallicity and abundance ratio gradients for a sample of red galaxies in the Sloan Digital Sky Survey (SDSS) Main galaxy sample. Because this sample does not have multiple spectra at various radii in a single galaxy, we measure these gradients statistically. We separate galaxies into stellar mass bins, stack their spectra in redshift bins, and calculate the measured absorption line indices in projected annuli by differencing spectra in neighboring redshift bins. After determining the line indices, we use stellar population modeling from the EZ\\_Ages software to calculate ages, metallicities, and abundance ratios within each annulus. Our data covers the central regions of these galaxies, out to slightly higher than $1 R_{e}$. We find detectable gradients in metallicity and relatively shallow gradients in abundance ratios, similar to results found for direct measurements of individual galaxies. The gradients are only weakly dependent on stellar mass, and this dependence is well-correlated with...

  3. Approximate error conjugation gradient minimization methods

    Science.gov (United States)

    Kallman, Jeffrey S

    2013-05-21

    In one embodiment, a method includes selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, calculating an approximate error using the subset of rays, and calculating a minimum in a conjugate gradient direction based on the approximate error. In another embodiment, a system includes a processor for executing logic, logic for selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, logic for calculating an approximate error using the subset of rays, and logic for calculating a minimum in a conjugate gradient direction based on the approximate error. In other embodiments, computer program products, methods, and systems are described capable of using approximate error in constrained conjugate gradient minimization problems.

  4. Inaudible functional MRI using a truly mute gradient echo sequence

    Energy Technology Data Exchange (ETDEWEB)

    Marcar, V.L. [University of Zurich, Department of Psychology, Neuropsychology, Treichlerstrasse 10, 8032 Zurich (Switzerland); Girard, F. [GE Medical Systems SA, 283, rue de la Miniere B.P. 34, 78533 Buc Cedex (France); Rinkel, Y.; Schneider, J.F.; Martin, E. [University Children' s Hospital, Neuroradiology and Magnetic Resonance, Department of Diagnostic Imaging, Steinwiesstrasse 75, 8032 Zurich (Switzerland)

    2002-11-01

    We performed functional MRI experiments using a mute version of a gradient echo sequence on adult volunteers using either a simple visual stimulus (flicker goggles: 4 subjects) or an auditory stimulus (music: 4 subjects). Because the mute sequence delivers fewer images per unit time than a fast echo planar imaging (EPI) sequence, we explored our data using a parametric ANOVA test and a non-parametric Wilcoxon-Mann-Whitney test in addition to performing a cross-correlation analysis. All three methods were in close agreement regarding the location of the BOLD contrast signal change. We demonstrated that, using appropriate statistical analysis, functional MRI using an MR sequence that is acoustically inaudible to the subject is feasible. Furthermore compared with the ''silent'' event-related procedures involving an EPI protocol, our mGE protocol compares favourably with respect to experiment time and the BOLD signal. (orig.)

  5. Inaudible functional MRI using a truly mute gradient echo sequence

    International Nuclear Information System (INIS)

    We performed functional MRI experiments using a mute version of a gradient echo sequence on adult volunteers using either a simple visual stimulus (flicker goggles: 4 subjects) or an auditory stimulus (music: 4 subjects). Because the mute sequence delivers fewer images per unit time than a fast echo planar imaging (EPI) sequence, we explored our data using a parametric ANOVA test and a non-parametric Wilcoxon-Mann-Whitney test in addition to performing a cross-correlation analysis. All three methods were in close agreement regarding the location of the BOLD contrast signal change. We demonstrated that, using appropriate statistical analysis, functional MRI using an MR sequence that is acoustically inaudible to the subject is feasible. Furthermore compared with the ''silent'' event-related procedures involving an EPI protocol, our mGE protocol compares favourably with respect to experiment time and the BOLD signal. (orig.)

  6. Thermochemical scanning probe lithography of protein gradients at the nanoscale.

    Science.gov (United States)

    Albisetti, E; Carroll, K M; Lu, X; Curtis, J E; Petti, D; Bertacco, R; Riedo, E

    2016-08-01

    Patterning nanoscale protein gradients is crucial for studying a variety of cellular processes in vitro. Despite the recent development in nano-fabrication technology, combining nanometric resolution and fine control of protein concentrations is still an open challenge. Here, we demonstrate the use of thermochemical scanning probe lithography (tc-SPL) for defining micro- and nano-sized patterns with precisely controlled protein concentration. First, tc-SPL is performed by scanning a heatable atomic force microscopy tip on a polymeric substrate, for locally exposing reactive amino groups on the surface, then the substrate is functionalized with streptavidin and laminin proteins. We show, by fluorescence microscopy on the patterned gradients, that it is possible to precisely tune the concentration of the immobilized proteins by varying the patterning parameters during tc-SPL. This paves the way to the use of tc-SPL for defining protein gradients at the nanoscale, to be used as chemical cues e.g. for studying and regulating cellular processes in vitro. PMID:27344982

  7. Thermochemical scanning probe lithography of protein gradients at the nanoscale

    Science.gov (United States)

    Albisetti, E.; Carroll, K. M.; Lu, X.; Curtis, J. E.; Petti, D.; Bertacco, R.; Riedo, E.

    2016-08-01

    Patterning nanoscale protein gradients is crucial for studying a variety of cellular processes in vitro. Despite the recent development in nano-fabrication technology, combining nanometric resolution and fine control of protein concentrations is still an open challenge. Here, we demonstrate the use of thermochemical scanning probe lithography (tc-SPL) for defining micro- and nano-sized patterns with precisely controlled protein concentration. First, tc-SPL is performed by scanning a heatable atomic force microscopy tip on a polymeric substrate, for locally exposing reactive amino groups on the surface, then the substrate is functionalized with streptavidin and laminin proteins. We show, by fluorescence microscopy on the patterned gradients, that it is possible to precisely tune the concentration of the immobilized proteins by varying the patterning parameters during tc-SPL. This paves the way to the use of tc-SPL for defining protein gradients at the nanoscale, to be used as chemical cues e.g. for studying and regulating cellular processes in vitro.

  8. New Radial Abundance Gradients for NGC 628 and NGC 2403

    CERN Document Server

    Berg, Danielle A; Garnett, Donald R; Croxall, Kevin V; Marble, Andrew R; Smith, J D; Gordon, Karl; Kennicutt, Robert C

    2013-01-01

    Motived by recent ISM studies, we present high quality MMT and Gemini spectroscopic observations of H II regions in the nearby spiral galaxies NGC 628 and NGC 2403 in order to measure their chemical abundance gradients. Using long-slit and multi-object mask optical spectroscopy, we obtained measurements of the temperature sensitive auroral lines [O III] {\\lambda}4363 and/or [N II] {\\lambda}5755 at a strength of 4{\\sigma} or greater in 11 H II regions in NGC 628 and 7 regions in NGC 2403. These observations allow us, for the first time, to derive an oxygen abundance gradient in NGC 628 based solely on "direct" oxygen abundances of H II regions: 12 + log(O/H) = (8.43+/-0.03) + (-0.017+/-0.002) x Rg (dex/kpc), with a dispersion in log(O/H) of {\\sigma} = 0.10 dex, from 14 regions with a radial coverage of ~2-19 kpc. This is a significantly shallower slope than found by previous "strong-line" abundance studies. In NGC 2403, we derive an oxygen abundance gradient of 12 + log(O/H) = (8.48+/-0.04) + (-0.032+/-0.007) ...

  9. Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system

    Science.gov (United States)

    Tang, Fangfang; Freschi, Fabio; Sanchez Lopez, Hector; Repetto, Maurizio; Liu, Feng; Crozier, Stuart

    2016-04-01

    An MRI-LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI-LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process.

  10. Flow field thermal gradient gas chromatography.

    Science.gov (United States)

    Boeker, Peter; Leppert, Jan

    2015-09-01

    Negative temperature gradients along the gas chromatographic separation column can maximize the separation capabilities for gas chromatography by peak focusing and also lead to lower elution temperatures. Unfortunately, so far a smooth thermal gradient over a several meters long separation column could only be realized by costly and complicated manual setups. Here we describe a simple, yet flexible method for the generation of negative thermal gradients using standard and easily exchangeable separation columns. The measurements made with a first prototype reveal promising new properties of the optimized separation process. The negative thermal gradient and the superposition of temperature programming result in a quasi-parallel separation of components each moving simultaneously near their lowered specific equilibrium temperatures through the column. Therefore, this gradient separation process is better suited for thermally labile molecules such as explosives and natural or aroma components. High-temperature GC methods also benefit from reduced elution temperatures. Even for short columns very high peak capacities can be obtained. In addition, the gradient separation is particularly beneficial for very fast separations below 1 min overall retention time. Very fast measurements of explosives prove the benefits of using negative thermal gradients. The new concept can greatly reduce the cycle time of high-resolution gas chromatography and can be integrated into hyphenated or comprehensive gas chromatography setups. PMID:26235451

  11. Phospho-proteins patial gradients in a cell of spheroidal shape

    Science.gov (United States)

    Sosa, Gerardo; Ramirez-Santiago, Guillermo

    2010-03-01

    Many signalling proteins undergo phosphorilated-dephosphorilated cycles at different locations inside the cell. These cycles give rise to spatial gradients of phosphoproteins. In this work we solve the reaction-difussion equation in a spheroidal geometry and investigate the diffusion of the phosphorilated form of the proteins to evaluate the size of the spatial gradients. This is done in terms of diffusion coefficients as well as protein kinase and phosphatase activities. Previous estimations of these gradients have been done for two geometries [1]: (i) a spherical cell and (ii) for a kinase and a protein each one located on two parallel planar membranes. This type of quantitative analyzes may have important implications in the cellular signaling processes [2].[4pt] [1] G.C. Brown, B.N. Kholodenko, FEBS Letters, vol. 457, p. 452-454[0pt] [2] B.N. Kholodenko, G.C. Brown, J.B. Hoek, Biochem. J. vol. 350, p. 901-907.

  12. Molybdenum sputtering film characterization for high gradient accelerating structures

    Institute of Scientific and Technical Information of China (English)

    S.Bini; B.Spataro; A.Marcelli; S.Sarti; V.A.Dolgashev; S.Tantawi; A.D.Yeremian

    2013-01-01

    Technological advancements are strongly required to fulfill the demands of new accelerator devices with the highest accelerating gradients and operation reliability for the future colliders.To this purpose an extensive R&D regarding molybdenum coatings on copper is in progress.In this contribution we describe chemical composition,deposition quality and resistivity properties of different molybdenum coatings obtained via sputtering.The deposited films are thick metallic disorder layers with different resistivity values above and below the molibdenum dioxide reference value.Chemical and electrical properties of these sputtered coatings have been characterized by Rutherford backscattering,XANES and photoemission spectroscopy.We will also consider multiple cells standing wave section coated by a molybdenum layer designed to improve the performance of X-Band accelerating systems.

  13. Metamorphism during temperature gradient with undersaturated advective airflow in a snow sample

    Science.gov (United States)

    Ebner, Pirmin Philipp; Schneebeli, Martin; Steinfeld, Aldo

    2016-04-01

    Snow at or close to the surface commonly undergoes temperature gradient metamorphism under advective flow, which alters its microstructure and physical properties. Time-lapse X-ray microtomography is applied to investigate the structural dynamics of temperature gradient snow metamorphism exposed to an advective airflow in controlled laboratory conditions. Cold saturated air at the inlet was blown into the snow samples and warmed up while flowing across the sample with a temperature gradient of around 50 K m-1. Changes of the porous ice structure were observed at mid-height of the snow sample. Sublimation occurred due to the slight undersaturation of the incoming air into the warmer ice matrix. Diffusion of water vapor opposite to the direction of the temperature gradient counteracted the mass transport of advection. Therefore, the total net ice change was negligible leading to a constant porosity profile. However, the strong recrystallization of water molecules in snow may impact its isotopic or chemical content.

  14. Numerical evaluation of voltage gradient constraints on electrokinetic injection of amendments

    Science.gov (United States)

    Wu, Ming Zhi; Reynolds, David A.; Prommer, Henning; Fourie, Andy; Thomas, David G.

    2012-03-01

    A new numerical model is presented that simulates groundwater flow and multi-species reactive transport under hydraulic and electrical gradients. Coupled into the existing, reactive transport model PHT3D, the model was verified against published analytical and experimental studies, and has applications in remediation cases where the geochemistry plays an important role. A promising method for remediation of low-permeability aquifers is the electrokinetic transport of amendments for in situ chemical oxidation. Numerical modelling showed that amendment injection resulted in the voltage gradient adjacent to the cathode decreasing below a linear gradient, producing a lower achievable concentration of the amendment in the medium. An analytical method is derived to estimate the achievable amendment concentration based on the inlet concentration. Even with low achievable concentrations, analysis showed that electrokinetic remediation is feasible due to its ability to deliver a significantly higher mass flux in low-permeability media than under a hydraulic gradient.

  15. Characterization and simulation on antireflective coating of amorphous silicon oxide thin films with gradient refractive index

    Science.gov (United States)

    Huang, Lu; Jin, Qi; Qu, Xingling; Jin, Jing; Jiang, Chaochao; Yang, Weiguang; Wang, Linjun; Shi, Weimin

    2016-08-01

    The optical reflective properties of silicon oxide (SixOy) thin films with gradient refractive index are studied both theoretically and experimentally. The thin films are widely used in photovoltaic as antireflective coatings (ARCs). An effective finite difference time domain (FDTD) model is built to find the optimized reflection spectra corresponding to structure of SixOy ARCs with gradient refractive index. Based on the simulation analysis, it shows the variation of reflection spectra with gradient refractive index distribution. The gradient refractive index of SixOy ARCs can be obtained in adjustment of SiH4 to N2O ratio by plasma-enhanced chemical vapor deposition (PECVD) system. The optimized reflection spectra measured by UV-visible spectroscopy confirms to agree well with that simulated by FDTD method.

  16. Sound beam manipulation based on temperature gradients

    International Nuclear Information System (INIS)

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking

  17. Colour and stellar population gradients in galaxies

    CERN Document Server

    Tortora, C; Cardone, V F; Capaccioli, M; Jetzer, P; Molinaro, R

    2010-01-01

    We discuss the colour, age and metallicity gradients in a wide sample of local SDSS early- and late-type galaxies. From the fitting of stellar population models we find that metallicity is the main driver of colour gradients and the age in the central regions is a dominant parameter which rules the scatter in both metallicity and age gradients. We find a consistency with independent observations and a set of simulations. From the comparison with simulations and theoretical considerations we are able to depict a general picture of a formation scenario.

  18. Sound beam manipulation based on temperature gradients

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Feng [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500 (China); Quan, Li; Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-10-28

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking.

  19. Gradient Yamabe Solitons on Warped Products

    OpenAIRE

    He, Chenxu

    2011-01-01

    The special nature of gradient Yamabe soliton equation which was first observed by Cao-Sun-Zhang\\cite{CaoSunZhang} shows that a complete gradient Yamabe soliton with non-constant potential function is either defined on the Euclidean space with rotational symmetry, or on the warped product of the real line with a manifold of constant scalar curvature. In this paper we consider the classification in the latter case. We show that a complete gradient steady Yamabe soliton on warped product is nec...

  20. Probing the possibility of a 12C13C abundance gradient from observations of interstellar CH+

    International Nuclear Information System (INIS)

    I have performed high signal-to-noise (SN /equals/ 300 to 500) observations of interstellar CH/sup /plus// at Lick Observatory and at CTIO of the reddened, early-type stars HD 183143, HD 24432, and HD 157038 in an effort to probe the existence of a 12C13C abundance gradient in our Galaxy

  1. Leptin signaling

    OpenAIRE

    Park, Hyeong-Kyu; Ahima, Rexford S.

    2014-01-01

    Leptin is secreted by adipose tissue and regulates energy homeostasis, glucose and lipid metabolism, immune function, and other systems. The binding of leptin to its specific receptor activates various intracellular signaling pathways, including Janus kinase 2 (JAK2)/ signal transducer and activator of transcription 3 (STAT3), insulin receptor substrate (IRS)/phosphatidylinositol 3 kinase (PI3K), SH2-containing protein tyrosine phosphatase 2 (SHP2)/mitogen-activated protein kinase (MAPK), and...

  2. On the α-element gradients of the Galactic thin disk using Cepheids

    Science.gov (United States)

    Genovali, K.; Lemasle, B.; da Silva, R.; Bono, G.; Fabrizio, M.; Bergemann, M.; Buonanno, R.; Ferraro, I.; François, P.; Iannicola, G.; Inno, L.; Laney, C. D.; Kudritzki, R.-P.; Matsunaga, N.; Nonino, M.; Primas, F.; Romaniello, M.; Urbaneja, M. A.; Thévenin, F.

    2015-08-01

    We present new homogeneous measurements of Na, Al, and three α-elements (Mg, Si, Ca) for 75 Galactic Cepheids. The abundances are based on high spectral resolution (R~ 38 000) and high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO VLT. The current measurements were complemented with Cepheid abundances provided by our group (75) or available in the literature, for a total of 439 Galactic Cepheids. Special attention was given to providing a homogeneous abundance scale for these five elements plus iron. In addition, accurate Galactocentric distances (RG) based on near-infrared photometry are also available for all the Cepheids in the sample. They cover a large section of the Galactic thin disk (4.1 ≤RG≤ 18.4 kpc). We found that these five elements display well-defined linear radial gradients and modest standard deviations over the entire range of RG. Moreover, the [element/Fe] abundance ratios are constant across the entire thin disk; only the Ca radial distribution shows marginal evidence of a positive slope. These results indicate that the chemical enrichment history of iron and of the quoted five elements has been quite similar across the four quadrants of the Galactic thin disk. The [element/Fe] ratios are also constant over the entire period range. This empirical evidence indicates that the chemical enrichment of Galactic Cepheids has also been very homogenous within the range in age that they cover (~10-300 Myr). Once again, [Ca/Fe] vs. log P shows a (negative) gradient, since it is underabundant among the youngest Cepheids. Finally, we also find that Cepheid abundances agree quite well with similar abundances for thin and thick disk dwarf stars, and they follow the typical Mg-Al and Na-O correlations. Based on spectra collected with the UVES spectrograph available at the ESO Very Large Telescope (VLT), Cerro Paranal, Chile (ESO Proposals: 081.D-0928(A), PI: S. Pedicelli; 082.D-0901(A), PI: S. Pedicelli; 089.D-0767(C), PI: K

  3. Guided Signal Reconstruction with Application to Image Magnification

    OpenAIRE

    Gadde, Akshay; Knyazev, Andrew; Tian, Dong; Mansour, Hassan

    2015-01-01

    We study the problem of reconstructing a signal from its projection on a subspace. The proposed signal reconstruction algorithms utilize a guiding subspace that represents desired properties of reconstructed signals. We show that optimal reconstructed signals belong to a convex bounded set, called the "reconstruction" set. We also develop iterative algorithms, based on conjugate gradient methods, to approximate optimal reconstructions with low memory and computational costs. The effectiveness...

  4. Isotachophoresis of proteins in sucrose density gradients.

    Science.gov (United States)

    Acevedo, F

    1993-10-01

    The separation of proteins from human serum by isotachophoresis in sucrose density gradients, with mixtures of discrete amphoteric substances as spacers, is described. Open columns and columns with a dialysis membrane to hold the sucrose gradients were used. A simple algorithm based on the Kohlrausch function was used to calculate the amount of each spacer. The pH gradients generated in open columns were found to be in agreement with the calculations. The load was up to two gram proteins. The analysis of the fractions obtained after the separation showed a distribution of components similar to as analytical isotachophoresis. It is concluded that sucrose density gradients are suitable as supporting media for the preparative separation of proteins by isotachophoresis. The high resolution attained and the possibility of scaling-up the separation systems are major advantages of this system. In addition, the sample is easily and completely recoverable. PMID:8125049

  5. Optimizing sampling approaches along ecological gradients

    DEFF Research Database (Denmark)

    Schweiger, Andreas; Irl, Severin D. H.; Steinbauer, Manuel;

    2015-01-01

    1. Natural scientists and especially ecologists use manipulative experiments or field observations along gradients to differentiate patterns driven by processes from those caused by random noise. A well-conceived sampling design is essential for identifying, analysing and reporting underlying...

  6. The gradient flow in simple field theories

    CERN Document Server

    Monahan, Christopher

    2015-01-01

    The gradient flow is a valuable tool for the lattice community, with applications from scale-setting to implementing chiral fermions. Here I focus on the gradient flow as a means to suppress power-divergent mixing. Power-divergent mixing stems from the hypercubic symmetry of the lattice regulator and is a particular difficulty for calculations of, for example, high moments of parton distribution functions. The gradient flow removes power-divergent mixing on the lattice, provided the flow time is kept fixed in physical units, at the expense of introducing a new physical scale in the continuum. One approach to dealing with this new scale is the smeared operator product expansion, a formalism that systematically connects nonperturbative calculations of flowed operators to continuum physics. I study the role of the gradient flow in suppressing power-divergent mixing and present the first nonperturbative study in scalar field theory.

  7. CMB Anisotropies from a Gradient Mode

    CERN Document Server

    Mirbabayi, Mehrdad

    2014-01-01

    A pure gradient mode must have no observable dynamical effect at linear level. We confirm this by showing that its contribution to the dipolar power asymmetry of CMB anisotropies vanishes, if Maldacena's consistency condition is satisfied. To this end, the existing second order Sachs-Wolfe formula in the squeezed limit is extended to include a gradient in the long mode and to account for the change in the location of the last scattering surface induced by this mode. At second order, a gradient mode generated in Single-field inflation is shown to induce a quadrupole moment. For instance in a matter-dominated model it is equal to 5/18 times the square of the linear gradient part. This quadrupole can be cancelled by superposing a quadratic perturbation. The result is shown to be a non-linear extension of Weinberg's adiabatic modes: a long-wavelength physical mode which looks locally like a coordinate transformation.

  8. Unimodal and crossmodal gradients of spatial attention

    DEFF Research Database (Denmark)

    Föcker, J.; Hötting, K.; Gondan, Matthias;

    2010-01-01

    Behavioral and event-related potential (ERP) studies have shown that spatial attention is gradually distributed around the center of the attentional focus. The present study compared uni- and crossmodal gradients of spatial attention to investigate whether the orienting of auditory and visual...... spatial attention is based on modality specific or supramodal representations of space. Auditory and visual stimuli were presented from five speaker locations positioned in the right hemifield. Participants had to attend to the innermost or outmost right position in order to detect either visual or...... auditory deviant stimuli. Detection rates and event-related potentials (ERPs) indicated that spatial attention is distributed as a gradient. Unimodal spatial ERP gradients correlated with the spatial resolution of the modality. Crossmodal spatial gradients were always broader than the corresponding...

  9. HIGH-GRADIENT MAGNETIC SEPARATION FOR REMOVAL OF SULFUR FROM COAL

    Science.gov (United States)

    The report gives results of a thorough physical, chemical, and magnetic characterization of a Pennsylvania coal from the Upper Freeport seam. The powdered coal was then subjected to high-gradient magnetic separations, as a function of magnetic field and fluid velocity, in both a ...

  10. Methods for Signal Filtering in NMR Tomography

    Czech Academy of Sciences Publication Activity Database

    Gescheidtová, E.; Kubásek, R.; Bartušek, Karel

    2006-01-01

    Roč. 4, č. 1 (2006), 3404:1-10. ISSN 1738-9682 Institutional research plan: CEZ:AV0Z20650511 Keywords : FID signal * pre-emphasis * gradient pulse * bank of digital filters * threshold Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  11. Enhancing stochastic kriging metamodels with gradient estimators

    OpenAIRE

    Chen, X.; Ankenman, B. E.; Nelson, B. L.

    2013-01-01

    Stochastic kriging is a new metamodeling technique for effectively representing the mean response surface implied by a stochastic simulation; it takes into account both stochastic simulation noise and uncertainty about the underlying response surface of interest. We show theoretically, through some simplified models, that incorporating gradient estimators into stochastic kriging tends to significantly improve surface prediction. To address the issue of which type of gradient estimator to use,...

  12. Voltammetry under a Controlled Temperature Gradient

    OpenAIRE

    Jan Krejci, Jr.; Tomas Marvanek; Zuzana Sajdlova; Jan Krejci

    2010-01-01

    Electrochemical measurements are generally done under isothermal conditions. Here we report on the application of a controlled temperature gradient between the working electrode surface and the solution. Using electrochemical sensors prepared on ceramic materials with extremely high specific heat conductivity, the temperature gradient between the electrode and solution was applied here as a second driving force. This application of the Soret phenomenon increases the mass transfer in the Nerns...

  13. The gradient flow in a twisted box

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Alberto [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2013-08-15

    We study the perturbative behavior of the gradient flow in a twisted box. We apply this information to define a running coupling using the energy density of the flow field. We study the step-scaling function and the size of cutoff effects in SU(2) pure gauge theory. We conclude that the twisted gradient flow running coupling scheme is a valid strategy for step-scaling purposes due to the relatively mild cutoff effects and high precision.

  14. ONLINE REGULARIZED GENERALIZED GRADIENT CLASSIFICATION ALGORITHMS

    Institute of Scientific and Technical Information of China (English)

    Leilei Zhang; Baohui Sheng; Jianli Wang

    2010-01-01

    This paper considers online classification learning algorithms for regularized classification schemes with generalized gradient.A novel capacity independent approach is presented.It verifies the strong convergence of sizes and yields satisfactory convergence rates for polynomially decaying step sizes.Compared with the gradient schemes,this al-gorithm needs only less additional assumptions on the loss function and derives a stronger result with respect to the choice of step sizes and the regularization parameters.

  15. Thermal gradient analysis of solidifying casting

    OpenAIRE

    J. Suchoń; M. Cholewa; M. Kondracki

    2008-01-01

    For description of casting solidification and crystallization process the thermal derivative analysis (TDA) is commonly used. Besides the process kinetics considered in TDA method to describe the solidification process, the thermal gradient analysis can be also used for this purpose [1, 2]. In conducted studies analysis of thermal gradient distribution inside the solidifying wedge casting was shown which enabled determination of heat flow intensity on casting section.

  16. Thermal gradient analysis of solidifying casting

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2008-08-01

    Full Text Available For description of casting solidification and crystallization process the thermal derivative analysis (TDA is commonly used. Besides the process kinetics considered in TDA method to describe the solidification process, the thermal gradient analysis can be also used for this purpose [1, 2]. In conducted studies analysis of thermal gradient distribution inside the solidifying wedge casting was shown which enabled determination of heat flow intensity on casting section.

  17. Salinity gradient power: utilizing vapor pressure differences.

    Science.gov (United States)

    Olsson, M; Wick, G L; Isaacs, J D

    1979-10-26

    By utilizing the vapor pressure difference between high-salinity and lowsalinity wvater, one can obtain power from the gradients of salinity. This scheme eliminates the major problems associated with conversion methods in which membranes are used. The method we tested gave higher conversion efficiencies than membrane methods. Furthermore, hardware and techniques being developed for ocean thermal energy conversion may be applied to this approach to salinity gradient energy conversion. PMID:17809370

  18. Design of spherical symmetric gradient index lenses

    OpenAIRE

    Miñano Dominguez, Juan Carlos; Grabovičkić, Dejan; Benitez Gimenez, Pablo; Gonzalez Lopez, Juan Carlos; Santamaria Galdon, Maria Asuncion

    2012-01-01

    Spherical symmetric refractive index distributions also known as Gradient Index lenses such as the Maxwell-Fish-Eye (MFE), the Luneburg or the Eaton lenses have always played an important role in Optics. The recent development of the technique called Transformation Optics has renewed the interest in these gradient index lenses. For instance, Perfect Imaging within the Wave Optics framework has recently been proved using the MFE distribution. We review here the design problem of these lenses, ...

  19. Gradient-prolongation commutativity and graph theory

    OpenAIRE

    Musy, François; Nicolas, Laurent; Perrussel, Ronan

    2007-01-01

    6 pages International audience This Note gives conditions that must be imposed to algebraic multilevel discretizations involving at the same time nodal and edge elements so that a gradient-prolongation commutativity condition will be satisfied; this condition is very important, since it characterizes the gradients of coarse nodal functions in the coarse edge function space. They will be expressed using graph theory and they provide techniques to compute approximation bases at each level.

  20. Nonlinear strain gradient elastic thin shallow shells

    OpenAIRE

    Lazopoulos, K.A.

    2011-01-01

    Abstract The governing equilibrium equations for strain gradient elastic thin shallow shells are derived, considering non-linear strains and linear constitutive strain gradient elastic relations. Adopting Kirchhoff's theory of thin shallow structures, the equilibrium equations, along with the boundary conditions, are formulated through a variational procedure. It turns out that new terms are introduced, indicating the importance of the cross-section area in bending of thin plates. ...

  1. Gradient-based compressive image fusion

    Institute of Scientific and Technical Information of China (English)

    Yang CHEN‡; Zheng QIN

    2015-01-01

    We present a novel image fusion scheme based on gradient and scrambled block Hadamard ensemble (SBHE) sam-pling for compressive sensing imaging. First, source images are compressed by compressive sensing, to facilitate the transmission of the sensor. In the fusion phase, the image gradient is calculated to reflect the abundance of its contour information. By com-positing the gradient of each image, gradient-based weights are obtained, with which compressive sensing coefficients are achieved. Finally, inverse transformation is applied to the coefficients derived from fusion, and the fused image is obtained. Information entropy (IE), Xydeas’s and Piella’s metrics are applied as non-reference objective metrics to evaluate the fusion quality in line with different fusion schemes. In addition, different image fusion application scenarios are applied to explore the scenario adaptability of the proposed scheme. Simulation results demonstrate that the gradient-based scheme has the best per-formance, in terms of both subjective judgment and objective metrics. Furthermore, the gradient-based fusion scheme proposed in this paper can be applied in different fusion scenarios.

  2. Nucleation modes in sharp concentration gradients

    Energy Technology Data Exchange (ETDEWEB)

    Hodaj, F.; Desre, P.J. [LTPCM-UMR CNRS/INPG/UJF, Saint Martin d`Heres (France); Gusak, A.M.; Kovalchuk, A.O. [Cherkassy State Univ. (Ukraine). Dept. of Theoretical Physics

    1998-12-31

    Reaction kinetics in bimetallic multilayers have demonstrated that sharp unidirectional concentration gradient, which develop as interdiffusion proceeds at the interface are able to delay or to suppress nucleation of intermetallics. It has been found that the existence of a critical gradient beyond which nucleation is inhibited is strongly dependent on the mechanism of formation of the embryo. A mechanism of nucleation under concentration gradient ({gradient}c) is proposed and treated on the basis of the Fokker-Planck equation for the distribution in the size space. The influence of the aspect ratio of the embryo on the critical concentration gradient is also studied. Due to the fluctuations of the embryo shape, it is shown that the minimization of the thermodynamic potential leading to the aspect ratio of the embryo is only significant beyond a certain value of the concentration gradient. Application is presented to the nucleation of the compound Ni{sub 10}Zr{sub 7} in an amorphous layer Ni-Zr.

  3. Statistical analysis of Fe abundances gradients in the Galaxy

    Institute of Scientific and Technical Information of China (English)

    CUI; Chenzhou

    2001-01-01

    [1]Shaver, P. A., McGee, R. X., Newton, L. M. et al., The galactic abundance gradient, MNRAS, 983, 204: 53.[2]Amnuel, P. R., The features of chemical abundances in Galactic planetary nebulae, MNRAS, 993, 26: 263.[3]Maciel, W. J., Kǒppen, J., Abundance gradents from disk planetary nebulae: O, Ne, S and Ar, A&A, 994, 282, 436.[4]Maciel, W. J., Abundance gradients from planetary nebulae in the galactic disk, IAU Samp., 997, 80: 397.[5]Maciel, W. J., Quireza, C., Abundance gradients in the outer galactic disk from planetary nebulae, A&A, 999, 345: 629.[6]Lennon, D. J., Dufton, P. L., Fitzsimmons, A. et al., Dolidze 25: a metal-deficient galactic open cluster, A&A, 990, 240: 349.[7]Fitzsimmons, A., Dufton, P. L., Rolleston, W. R. J., A comparison of oxygen and nitrogen abundances in young clusters and associations and in the interstellar gas, MNRAS, 992, 259: 489.[8]Kilian, J., Montenbruck, O., Nissen, P. E., The galactic distribution of chemical elements as derived from B-stars in open clusters, A&A, 994, 284: 437.[9]Kaufer, A., Szeifert, T., Krenzin, R. et al., The galactic abundance gradients traced by B-type stars, A&A, 994, 289: 740.[10]Smartt, S. J., Dufton, P. L., Rolleston, W. R. J., A metal deficient early B-type star near the edge of the galactic disk, A&A, 996, 305: 64.[11]Smartt, S. J., Dufton, P. L., Rolleston, W. R. J., The chemical composition towards the galactic anti-centre, A&A, 996, 30: 23.[12]Binette, L., Dopita, M. A., D'Odorico, S. et al., The galactic abundance gradient from supernova remnant observations, A&A, 982, 5: 35.[13]Dauphole, B., Geffert, M., Colin, J. et al., The kinematics of globular clusters, apocentric distances and a halo metallicity gradient, A&A, 996, 33: 9.[14]Marsakov, V. A., Shevelev, Y. G., Catalogue of ages, metallicities, orbital elements and other parameters for nearby F stars, BICDS, 995, 47: 3.[15]Cayrel de Strobel, G., Soubiran, C., Friel, E. D. et al., A

  4. Density gradient effects in the tokamak edge turbulence with temperature gradient driving

    International Nuclear Information System (INIS)

    Based on the magnetohydrodynamics, a new theoretical model is established. In this model the density gradient effects is added into the tokamak edge turbulence with temperature gradient driving. The physical mechanism and the density gradient effects in evolution of this turbulence are discussed. The fluctuation levels and the associated diffusion coefficients at the turbulent saturation are calculated. The theoretical results are in agreement with the experimental ones on TEXT

  5. Tuning the Voices of a Choir: Detecting Ecological Gradients in Time-Series Populations

    Science.gov (United States)

    Buras, Allan; van der Maaten-Theunissen, Marieke; van der Maaten, Ernst; Ahlgrimm, Svenja; Hermann, Philipp; Simard, Sonia; Heinrich, Ingo; Helle, Gerd; Unterseher, Martin; Schnittler, Martin; Eusemann, Pascal; Wilmking, Martin

    2016-01-01

    This paper introduces a new approach–the Principal Component Gradient Analysis (PCGA)–to detect ecological gradients in time-series populations, i.e. several time-series originating from different individuals of a population. Detection of ecological gradients is of particular importance when dealing with time-series from heterogeneous populations which express differing trends. PCGA makes use of polar coordinates of loadings from the first two axes obtained by principal component analysis (PCA) to define groups of similar trends. Based on the mean inter-series correlation (rbar) the gain of increasing a common underlying signal by PCGA groups is quantified using Monte Carlo Simulations. In terms of validation PCGA is compared to three other existing approaches. Focusing on dendrochronological examples, PCGA is shown to correctly determine population gradients and in particular cases to be advantageous over other considered methods. Furthermore, PCGA groups in each example allowed for enhancing the strength of a common underlying signal and comparably well as hierarchical cluster analysis. Our results indicate that PCGA potentially allows for a better understanding of mechanisms causing time-series population gradients as well as objectively enhancing the performance of climate transfer functions in dendroclimatology. While our examples highlight the relevance of PCGA to the field of dendrochronology, we believe that also other disciplines working with data of comparable structure may benefit from PCGA. PMID:27467508

  6. Correction of geometric distortion in Propeller echo planar imaging using a modified reversed gradient approach

    Science.gov (United States)

    Chang, Hing-Chiu; Chuang, Tzu-Chao; Wang, Fu-Nien; Huang, Teng-Yi; Chung, Hsiao-Wen

    2013-01-01

    Objective This study investigates the application of a modified reversed gradient algorithm to the Propeller-EPI imaging method (periodically rotated overlapping parallel lines with enhanced reconstruction based on echo-planar imaging readout) for corrections of geometric distortions due to the EPI readout. Materials and methods Propeller-EPI acquisition was executed with 360-degree rotational coverage of the k-space, from which the image pairs with opposite phase-encoding gradient polarities were extracted for reversed gradient geometric and intensity corrections. The spatial displacements obtained on a pixel-by-pixel basis were fitted using a two-dimensional polynomial followed by low-pass filtering to assure correction reliability in low-signal regions. Single-shot EPI images were obtained on a phantom, whereas high spatial resolution T2-weighted and diffusion tensor Propeller-EPI data were acquired in vivo from healthy subjects at 3.0 Tesla, to demonstrate the effectiveness of the proposed algorithm. Results Phantom images show success of the smoothed displacement map concept in providing improvements of the geometric corrections at low-signal regions. Human brain images demonstrate prominently superior reconstruction quality of Propeller-EPI images with modified reversed gradient corrections as compared with those obtained without corrections, as evidenced from verification against the distortion-free fast spin-echo images at the same level. Conclusions The modified reversed gradient method is an effective approach to obtain high-resolution Propeller-EPI images with substantially reduced artifacts. PMID:23630654

  7. Irreducible decomposition of strain gradient tensor in isotropic strain gradient elasticity

    CERN Document Server

    Lazar, Markus

    2016-01-01

    In isotropic strain gradient elasticity, we decompose the strain gradient tensor into its irreducible pieces under the n-dimensional orthogonal group O(n). Using the Young tableau method for traceless tensors, four irreducible pieces (n>2), which are canonical, are obtained. In three dimensions, the strain gradient tensor can be decomposed into four irreducible pieces with 7+5+3+3 independent components whereas in two dimensions, the strain gradient tensor can be decomposed into three irreducible pieces with 2+2+2 independent components. The knowledge of these irreducible pieces is extremely useful when setting up constitutive relations and strain energy.

  8. Rotating-frame gradient fields for magnetic resonance imaging and nuclear magnetic resonance in low fields

    Science.gov (United States)

    Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki

    2014-01-21

    A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.

  9. Mitochondrial emitted electromagnetic signals mediate retrograde signaling.

    Science.gov (United States)

    Bagkos, Georgios; Koufopoulos, Kostas; Piperi, Christina

    2015-12-01

    Recent evidence shows that mitochondria regulate nuclear transcriptional activity both in normal and cell stress conditions, known as retrograde signaling. Under normal mitochondrial function, retrograde signaling is associated with mitochondrial biogenesis, normal cell phenotype and metabolic profile. In contrast, mitochondrial dysfunction leads to abnormal (oncogenic) cell phenotype and altered bio-energetic profile (nucleus reprogramming). Despite intense research efforts, a concrete mechanism through which mitochondria determine the group of genes expressed by the nucleus is still missing. The present paper proposes a novel hypothesis regarding retrograde signaling. More specifically, it reveals the mitochondrial membrane potential (MMP) and the accompanied strong electromagnetic field (EF) as key regulatory factors of nuclear activity. Mitochondrial emitted EFs extend in long distance and affect the function of nuclear membrane receptors. Depending on their frequencies, EFs can directly activate or deactivate different groups of nuclear receptors and so determine nuclear gene expression. One of the key features of the above hypothesis is that nuclear membrane receptors, besides their own endogenous or chemical ligands (hormones, lipids, etc.), can also be activated by electromagnetic signals. Moreover, normal MMP values (about -140 mV) are associated with the production of high ATP quantities and small levels of reactive oxygen species (ROS) while the hyperpolarization observed in all cancer cell types leads to a dramatic fall in ATP production and an analogous increase in ROS. The diminished ATP and increased ROS production negatively affect the function of all cellular systems including nucleus. Restoration of mitochondrial function, which is characterized by the fluctuation of MMP and EF values within a certain (normal) range, is proposed as a necessary condition for normal nuclear function and cancer therapy. PMID:26474928

  10. Increases in the abundance of microbial genes encoding halotolerance and photosynthesis along a sediment salinity gradient

    Directory of Open Access Journals (Sweden)

    T. C. Jeffries

    2011-07-01

    Full Text Available Biogeochemical cycles are driven by the metabolic activity of microbial communities, yet the environmental parameters that underpin shifts in the functional potential coded within microbial community genomes are still poorly understood. Salinity is one of the primary determinants of microbial community structure and can vary strongly along gradients within a variety of habitats. To test the hypothesis that shifts in salinity will also alter the bulk biogeochemical potential of aquatic microbial assemblages, we generated four metagenomic DNA sequence libraries from sediment samples taken along a continuous, natural salinity gradient in the Coorong lagoon, Australia, and compared them to physical and chemical parameters. A total of 392483 DNA sequences obtained from four sediment samples were generated and used to compare genomic characteristics along the gradient. The most significant shifts along the salinity gradient were in the genetic potential for halotolerance and photosynthesis, which were more highly represented in hypersaline samples. At these sites, halotolerance was achieved by an increase in genes responsible for the acquisition of compatible solutes – organic chemicals which influence the carbon, nitrogen and methane cycles of sediment. Photosynthesis gene increases were coupled to an increase in genes matching Cyanobacteria, which are responsible for mediating CO2 and nitrogen cycles. These salinity driven shifts in gene abundance will influence nutrient cycles along the gradient, controlling the ecology and biogeochemistry of the entire ecosystem.

  11. Signal Processing

    International Nuclear Information System (INIS)

    Signal processing techniques, extensively used nowadays to maximize the performance of audio and video equipment, have been a key part in the design of hardware and software for high energy physics detectors since pioneering applications in the UA1 experiment at CERN in 1979

  12. Galactic abundance gradients from Cepheids: alpha and heavy elements in the outer disk

    CERN Document Server

    Lemasle, B; Genovali, K; Kovtyukh, V V; Bono, G; Inno, L; Laney, C D; Kaper, L; Bergemann, M; Fabrizio, M; Matsunaga, N; Pedicelli, S; Primas, F; Romaniello, M

    2013-01-01

    Context: Galactic abundance gradients set strong constraints to chemo-dynamical evolutionary models of the Milky Way. Given the PL relations that provide accurate distances and the large number of spectral lines, Cepheids are excellent tracers of the present-day abundance gradients. Aims: We want to measure the Galactic abundance gradient of several chemical elements. While the slope of the Cepheid iron gradient did not vary much from the very first studies, the gradients of the other elements are not that well constrained. In this paper we focus on the inner and outer regions of the Galactic thin disk. Methods: We use HR spectra (FEROS, ESPADONS, NARVAL) to measure the abundances of several light (Na, Al), alpha (Mg, Si, S, Ca), and heavy elements (Y, Zr, La, Ce, Nd, Eu) in a sample of 65 Milky Way Cepheids. Combining these results with accurate distances from period-Wesenheit relations in the NIR enables us to determine the abundance gradients in the Milky Way. Results: Our results are in good agreement wit...

  13. Coextruded, aligned, and gradient-modified poly(ε-caprolactone) fibers as platforms for neural growth.

    Science.gov (United States)

    Kim, Si-Eun; Harker, Emily C; De Leon, Al C; Advincula, Rigoberto C; Pokorski, Jonathan K

    2015-03-01

    Polymeric fibers are of increasing interest to regenerative medicine, as materials made from these fibers are porous, allowing for cell infiltration, influx of nutrients, and efflux of waste products. Recently, multilayered coextrusion has emerged as a scalable and rapid fabrication method to yield microscale to submicron fibers. In this report, we describe the multilayered coextrusion of aligned poly(ε-caprolactone) (PCL) fibers, followed by a simple photochemical patterning to create surface-immobilized gradients onto the polymer fibers. PCL fibers were photochemically decorated with a linear gradient of propargyl benzophenone using a gradient photomask to control light source intensity. The pendant alkynes were then able to undergo the copper-catalyzed azide-alkyne cycloaddition reaction with an azide-modified IKVAV peptide to further functionalize the surface. Gradient-modified IKVAV fibers were evaluated for neural cell adhesion and neural differentiation, using PC-12 cells cultured onto the fibers. The aligned gradient fibers provided directional cues for neurite outgrowth and alignment of neural cells, as observed by cellular elongation, neurite differentiation, and orientation. The work presented herein describes a scalable fiber system combined with simple chemical patterning to generate aligned fibers with controlled surface gradients as cell-seeding scaffolds. PMID:25715836

  14. Understanding inverse metallicity gradients in galactic discs as a consequence of inside-out formation

    CERN Document Server

    Schönrich, Ralph

    2016-01-01

    The early stages of a galaxy's evolution leave an imprint on its metallicity distribution. We discuss the origins and evolution of radial metallicity gradients in discs of spiral galaxies using an analytical chemical evolution model. We explain how radial metallicity gradients in stellar populations are determined by three factors: the radial metallicity profile of the star-forming ISM, radial changes in the star-formation history (in particular inside-out formation), and radial mixing of stars. Under reasonable assumptions, inside-out formation steepens the negative ISM metallicity gradient, but contributes positively to the stellar metallicity gradient, up to inverting the metallicity profile to a positive d[Fe/H]/dR. This reconciles steep negative d[Fe/H]/dR in some high redshift galaxies to generally flatter gradients in local observations. We discuss the evidence for inverse radial metallicity gradients (positive d[X/H]/dR) at high redshifts and the inverse relationship between azimuthal velocity and the...

  15. Development of the CARS method for measurement of pressure and temperature gradients in centrifuges

    International Nuclear Information System (INIS)

    These experiments evaluated the feasibility of applying the CARS technique to the measurement of UF6 concentrations and pressure gradients in a gas centrifuge. The resultant CARS signals were properly related to system parameters as suggested by theory. The results have been used to guide design of an apparatus for making CARS measurements in a UF6 gas centrifuge. Ease of measurement is expected for pressures as low as 0.1 torr. Temperature gradients can be measured by this technique with changes in the data acquisition method. 16 references, 8 figures, 2 tables

  16. Chemical use

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This is a summary of research and activities related to chemical use on Neal Smith National Wildlife Refuge between 1992 and 2009. The chemicals used on the Refuge...

  17. Collective Signal Processing in Cluster Chemotaxis: Roles of Adaptation, Amplification, and Co-attraction in Collective Guidance

    Science.gov (United States)

    Camley, Brian A.; Zimmermann, Juliane; Levine, Herbert; Rappel, Wouter-Jan

    2016-01-01

    Single eukaryotic cells commonly sense and follow chemical gradients, performing chemotaxis. Recent experiments and theories, however, show that even when single cells do not chemotax, clusters of cells may, if their interactions are regulated by the chemoattractant. We study this general mechanism of “collective guidance” computationally with models that integrate stochastic dynamics for individual cells with biochemical reactions within the cells, and diffusion of chemical signals between the cells. We show that if clusters of cells use the well-known local excitation, global inhibition (LEGI) mechanism to sense chemoattractant gradients, the speed of the cell cluster becomes non-monotonic in the cluster’s size—clusters either larger or smaller than an optimal size will have lower speed. We argue that the cell cluster speed is a crucial readout of how the cluster processes chemotactic signals; both amplification and adaptation will alter the behavior of cluster speed as a function of size. We also show that, contrary to the assumptions of earlier theories, collective guidance does not require persistent cell-cell contacts and strong short range adhesion. If cell-cell adhesion is absent, and the cluster cohesion is instead provided by a co-attraction mechanism, e.g. chemotaxis toward a secreted molecule, collective guidance may still function. However, new behaviors, such as cluster rotation, may also appear in this case. Co-attraction and adaptation allow for collective guidance that is robust to varying chemoattractant concentrations while not requiring strong cell-cell adhesion. PMID:27367541

  18. Mismatch Calibration in LINC Power Amplifiers Using Modified Gradient Algorithm

    Directory of Open Access Journals (Sweden)

    Hosein Miar-Naimi

    2013-09-01

    Full Text Available One of the power amplifiers linearization technique is linear amplification with nonlinear components (LINC.The effects of phase and gain imbalances between two signal branches in LINC transmitters have been analyzed in this paper. Then a feedback path has been added to compensate this mismatches, using two complex gain in each path.This complex gains are controlled in a way to calibrate any gain and phase mismatches between two path using Modified Gradient Algorithm (MGA adaptively. The main advantages of this algorithm over other algorithms are zero residual error and fast convergence time. In the proposedarchitecture power amplifiers in each path are modeled as a complex gain which its phase and amplitude depend on input signal level. Many simulations have been performed to validate the proposed self calibrating LINC transmitter. Simulation results have confirmed the analyticalpredictions. According to simulation results the proposed structure has around 40 dB/Hz improvement in the first adjacent channel of the output signal spectrum.

  19. Queen signaling in social wasps

    DEFF Research Database (Denmark)

    van Zweden, Jelle Stijn; Bonckaert, Wim; Wenseleers, Tom;

    2014-01-01

    sterile (queen control), or if instead queens honestly signal their fertility and workers reproduce according to their own evolutionary incentives (queen signaling). Here, we test these competing hypotheses using data from Vespine wasps. We show that in natural colonies of the Saxon wasp, Dolichovespula...... saxonica, queens emit reliable chemical cues of their true fertility and that these putative queen signals decrease as the colony develops and worker reproduction increases. Moreover, these putative pheromones of D. saxonica show significant conservation with those of Vespula vulgaris and other Vespinae...

  20. Gradient expansion, curvature perturbations and magnetized plasmas

    CERN Document Server

    Giovannini, Massimo

    2011-01-01

    The properties of magnetized plasmas are always investigated under the hypothesis that the relativistic inhomogeneities stemming from the fluid sources and from the geometry itself are sufficiently small to allow for a perturbative description prior to photon decoupling. The latter assumption is hereby relaxed and pre-decoupling plasmas are described within a suitable expansion where the inhomogeneities are treated to a given order in the spatial gradients. It is argued that the (general relativistic) gradient expansion shares the same features of the drift approximation, customarily employed in the description of cold plasmas, so that the two schemes are physically complementary in the large-scale limit and for the low-frequency branch of the spectrum of plasma modes. The two-fluid description, as well as the magnetohydrodynamical reduction, are derived and studied in the presence of the spatial gradients of the geometry. Various solutions of the coupled system of evolution equations in the anti-Newtonian re...

  1. Production process for function-gradient material

    International Nuclear Information System (INIS)

    A function-gradient material to be used for a heat receiving element and a heat releasing plate of a divertor plate for use in a thermonuclear power plant is produced. Powders of two or more kinds of high-melting point ingredients having different grain size are formed into a slurry. This slurry is cast into a mold to form a molding product of powders having ingredients of high-melting point in which the grain size is gradually increased and the porosity is gradually reduced by the change of the sedimentation velocity. The molding product is sintered to form a skeleton having a structure in which the porosity is continuously changed to one surface. Further, the skeleton is impregnated with ingredients of low melting point under melting to form a function-gradient material. With such procedures, continuously gradient structure can be formed easily without using a powder accumulation device. (T.M.)

  2. Conjugate gradient algorithms using multiple recursions

    Energy Technology Data Exchange (ETDEWEB)

    Barth, T.; Manteuffel, T.

    1996-12-31

    Much is already known about when a conjugate gradient method can be implemented with short recursions for the direction vectors. The work done in 1984 by Faber and Manteuffel gave necessary and sufficient conditions on the iteration matrix A, in order for a conjugate gradient method to be implemented with a single recursion of a certain form. However, this form does not take into account all possible recursions. This became evident when Jagels and Reichel used an algorithm of Gragg for unitary matrices to demonstrate that the class of matrices for which a practical conjugate gradient algorithm exists can be extended to include unitary and shifted unitary matrices. The implementation uses short double recursions for the direction vectors. This motivates the study of multiple recursion algorithms.

  3. On fracture in finite strain gradient plasticity

    DEFF Research Database (Denmark)

    Martínez Pañeda, Emilio; Niordson, Christian Frithiof

    2016-01-01

    In this work a general framework for damage and fracture assessment including the effect of strain gradients is provided. Both mechanism-based and phenomenological strain gradient plasticity (SGP) theories are implemented numerically using finite deformation theory and crack tip fields are...... investigated. Differences and similarities between the two approaches within continuum SGP modeling are highlighted and discussed. Local strain hardening promoted by geometrically necessary dislocations (GNDs) in the vicinity of the crack leads to much higher stresses, relative to classical plasticity...... predictions. These differences increase significantly when large strains are taken into account, as a consequence of the contribution of strain gradients to the work hardening of the material. The magnitude of stress elevation at the crack tip and the distance ahead of the crack where GNDs significantly alter...

  4. Dynamics of gradient formation by intracellular shuttling

    Energy Technology Data Exchange (ETDEWEB)

    Berezhkovskii, Alexander M. [Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892 (United States); Shvartsman, Stanislav Y. [Department of Chemical and Biological Engineering and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544 (United States)

    2015-08-21

    A number of important cellular functions rely on the formation of intracellular protein concentration gradients. Experimental studies discovered a number of mechanisms for the formation of such gradients. One of the mechanisms relies on the intracellular shuttling of a protein that interconverts between the two states with different diffusivities, under the action of two enzymes, one of which is localized to the plasma membrane, whereas the second is uniformly distributed in the cytoplasm. Recent work reported an analytical solution for the steady state gradient in this mechanism, obtained in the framework of a one-dimensional reaction-diffusion model. Here, we study the dynamics in this model and derive analytical expressions for the Laplace transforms of the time-dependent concentration profiles in terms of elementary transcendental functions. Inverting these transforms numerically, one can obtain time-dependent concentration profiles of the two forms of the protein.

  5. Vertical gradients of sunspot magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Hagyard, M.J.; Teuber, D.; West, E.A.; Tandberg-Hanssen, E.; Henze, W. Jr.; Beckers, J.M.

    1983-04-01

    The results of a Solar Maximum Mission (SMM) guest investigation to determine the vertical gradients of sunspot magnetic fields for the first time from coordinated observations of photospheric and transition-region fields are described. Descriptions are given of both the photospheric vector field of a sunspot, derived from observations using the NASA Marshall Space Flight Center vector magnetograph, and of the line-of-sight component in the transition region, obtained from the SMM Ultraviolet Spectrometer and Polarimeter instrument. On the basis of these data, vertical gradients of the line-of-sight magnetic field component are calculated using three methods. It is found that the vertical gradient of Bz is lower than values from previous studies and that the transition-region field occurs at a height of approximately 4000-6000 km above the photosphere.

  6. Substrate Curvature Gradient Drives Rapid Droplet Motion

    Science.gov (United States)

    Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

    2014-07-01

    Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42 m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100 m/s on tapered surfaces.

  7. Adaptive Thermostats for Noisy Gradient Systems

    CERN Document Server

    Leimkuhler, Benedict

    2015-01-01

    We study numerical methods for sampling probability measures in high dimensions where the underlying model is only approximately identified with a gradient system. Extended stochastic dynamical methods are discussed which have application to multiscale models, nonequilibrium molecular dynamics and Bayesian sampling techniques arising in emerging machine learning applications. In addition to providing a more comprehensive discussion of the foundations of these methods, we propose a new numerical method for the Adaptive Langevin/stochastic gradient Nos\\'e-Hoover thermostat that achieves a dramatic improvement in numerical efficiency over the most popular stochastic gradient methods reported in the literature. We also demonstrate that the newly-established method inherits a superconvergence property (fourth order convergence to the invariant measure for configurational quantities) recently demonstrated in the setting of Langevin dynamics. Our findings are verified by numerical experiments.

  8. Chemical sensor

    Science.gov (United States)

    Rauh, R. David (Inventor)

    1990-01-01

    A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.

  9. Dynamics of polyelectrolyte solutions under a constant gradient of base concentration

    Science.gov (United States)

    Okuzono, Tohru; Seki, Tomotaka; Toyotama, Akiko; Yamanaka, Junpei

    2015-08-01

    Phase-separation dynamics of weakly charged polyacid solutions under a constant gradient of base concentration is studied both theoretically and numerically. The time-evolution equation of polymer volume fraction is derived by assuming that the chemical equilibrium of the dissociation reaction is locally established. Numerical simulations of the system in contact with two reservoirs in which the base concentrations differ are performed. The numerical results show that the polymer volume fraction can be transported by the concentration gradient of the base, which leads to the dynamic behavior of mesophase domain structures.

  10. Mirror symmetry breaking with limited enantioselective autocatalysis and temperature gradients: a stability survey

    CERN Document Server

    Blanco, Celia; Crusats, Joaquim; El-Hachemi, Zoubir; Moyano, Albert; Hochberg, David; 10.1039/C2CP43488A

    2012-01-01

    We analyze limited enantioselective (LES) autocatalysis in a temperature gradient and with internal flow/recycling of hot and cold material. Microreversibility forbids broken mirror symmetry for LES in the presence of a temperature gradient alone. This symmetry can be broken however when the auto-catalysis and limited enantioselective catalysis are each localized within the regions of low and high temperature, respectively. This scheme has been recently proposed as a plausible model for spontaneous emergence of chirality in abyssal hydrothermal vents. Regions in chemical parameter space are mapped out in which the racemic state is unstable and bifurcates to chiral solutions.

  11. Prosocial Signalling

    DEFF Research Database (Denmark)

    Kahsay, Goytom Abraha

    suggested that consumers pay price premium because this sends the signal that the consumer has prosocial preferences and a few empirical studies have documented that reputation plays a key role when consumers choose products containing prosocial components. However, little is known about consumers...... consumer goods and presents empirical evidences from a natural consumption data. This thesis also investigates consumers’ behaviour under a newly introduced pricing system called Pay-What-You-Want (PWYW) and investigates empirically whether reputation signalling can be used as a policy instrument in other...... role of social network in facilitating factor input transactions and the role of reputation in reducing enforcement. Finally, the third part consists of one paper which is concerned with investigating the effect of climate change and adaptation policy on agricultural production in Eastern Africa. The...

  12. Surface energy and stiffness discrete gradients in additive manufactured scaffolds for osteochondral regeneration.

    Science.gov (United States)

    Di Luca, Andrea; Longoni, Alessia; Criscenti, Giuseppe; Lorenzo-Moldero, Ivan; Klein-Gunnewiek, Michel; Vancso, Julius; van Blitterswijk, Clemens; Mota, Carlos; Moroni, Lorenzo

    2016-03-01

    Swift progress in biofabrication technologies has enabled unprecedented advances in the application of developmental biology design criteria in three-dimensional scaffolds for regenerative medicine. Considering that tissues and organs in the human body develop following specific physico-chemical gradients, in this study, we hypothesized that additive manufacturing (AM) technologies would significantly aid in the construction of 3D scaffolds encompassing such gradients. Specifically, we considered surface energy and stiffness gradients and analyzed their effect on adult bone marrow derived mesenchymal stem cell differentiation into skeletal lineages. Discrete step-wise macroscopic gradients were obtained by sequentially depositing different biodegradable biomaterials in the AM process, namely poly(lactic acid) (PLA), polycaprolactone (PCL), and poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymers. At the bulk level, PEOT/PBT homogeneous scaffolds supported a higher alkaline phosphatase (ALP) activity compared to PCL, PLA, and gradient scaffolds, respectively. All homogeneous biomaterial scaffolds supported also a significantly higher amount of glycosaminoglycans (GAGs) production compared to discrete gradient scaffolds. Interestingly, the analysis of the different material compartments revealed a specific contribution of PCL, PLA, and PEOT/PBT to surface energy gradients. Whereas PEOT/PBT regions were associated to significantly higher ALP activity, PLA regions correlated with significantly higher GAG production. These results show that cell activity could be influenced by the specific spatial distribution of different biomaterial chemistries in a 3D scaffold and that engineering surface energy discrete gradients could be considered as an appealing criterion to design scaffolds for osteochondral regeneration. PMID:26924824

  13. The Effects of Synthetic Cannabinoids on Alveolar-Arterial Oxygen Gradient

    Directory of Open Access Journals (Sweden)

    Egemen Kucuk

    2014-12-01

    Full Text Available Aim: Synthetic cannabinoids are chemicals that produce several marijuana-like effects in humans. Aim of this study is to investigate the effects of synthetic cannabinoids on to alveolar-arterial oxygen gradient. Material and Method: A total of 112 patients, who admitted directly to emergency clinic with synthetic cannabinoid usage, were determined between February 2014 and August 2014. Blood gases of 41 patients were determined as arterial blood gases on room air, and included in to study. Patients were evaluated according to age, sex, decade, partial pressure of arterial oxygen, partial pressure of arterial carbon dioxide, pH, bicarbonate, metabolic status, age consistent expected alveolar-arterial oxygen gradient and calculated alveolar-arterial oxygen gradient. Results: Synthetic cannabinoid using was higher in males, mean age of patients was 23.32±6.14 years. Number of patients in the third decade were significantly higher than the other decades. The calculated alveolar-arterial oxygen gradient value of patients was significantly higher than age consistent expected alveolar-arterial oxygen gradient value. Respiratory acidosis, was significantly higher than the other types of the metabolic disorders. The best cutoff point for calculated alveolar-arterial oxygen gradient was 12.70, with sensitivity of 90% and specifity of 85%. Area under curve was 0.70 for calculated alveolar-arterial oxygen gradient. Discussion: The value of alveolar-arterial oxygen gradient has been increased due to synthetic cannabinoid usage. This can be used as a supportive parameter in the diagnosis of synthetic cannabinoid usage.

  14. Climatic effects on decomposing litter and substrate chemistry along climatological gradients.

    Science.gov (United States)

    Berg, B.

    2009-04-01

    Climatic effects on decomposing litter and substrate chemistry along climatological gradients. B. Berg, Dipartimento Biologia Strutturale e Funzionale, Complesso Universitario, Monte San Angelo, via Cintia, I-80126 Napoli, Italy and Department of Forest Ecology, P.O. Box 27, University of Helsinki, FIN-00014, Helsinki, Finland. Studies of several processes, using climatic gradients do provide new information as compared with studies at e.g. a single site. Decomposition of plant litter in such gradients give response in decomposition rates to natural climate conditions. Thus Scots pine needle litter incubated in a climate gradient with annual average temperature (AVGT) ranging from -0.5 to 6.8oC had a highly significant increase in initial mass-loss rate with R2 = 0.591 (p<0.001) and a 5o increase in temperature doubled the mass-loss rate. As a contrast - needle litter of Norway spruce incubated in the same transect had no significant response to climate and for initial litter a 5o increase increased mass-loss rate c. 6%. For more decomposed Scots pine litter we could see that the effect of temperature on mass-loss rate gradually decreased until it disappeared. Long-term decomposition studies revealed differences in litter decomposition patterns along a gradient, even for the same type of litter. This could be followed by using an asymptotic function that gave, (i) a measure a maximum level of decomposition, (ii) the initial decomposition rate. Over a gradient the calculated maximum level of decomposition decreased with increasing AVGT. Other gradient studies revealed an effect of AVGT on litter chemical composition. Pine needle litter from stands under different climate conditions had nutrient concentrations related to AVGT. Thus N, P, K, and S were positively related to AVGT and Mn negatively, all of them significantly. This information may be used to explain the changing pattern in decomposition over the gradient.

  15. Auxin signaling

    OpenAIRE

    Quint, Marcel; Gray, William M.

    2006-01-01

    Auxin regulates a host of plant developmental and physiological processes, including embryogenesis, vascular differentiation, organogenesis, tropic growth, and root and shoot architecture. Genetic and biochemical studies carried out over the past decade have revealed that much of this regulation involves the SCFTIR1/AFB-mediated proteolysis of the Aux/IAA family of transcriptional regulators. With the recent finding that the TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) pro...

  16. Properties of the multicomponent and gradient PVD coatings

    Directory of Open Access Journals (Sweden)

    L.W. Żukowska

    2007-10-01

    Full Text Available Purpose: This paper presents investigation results of the properties of the multicomponent (Ti,AlN and gradient Ti(C,N wear resistant coatings, deposited with the PVD process onto the substrate from the cemented carbides, cermets and Al2O3+TiC type oxide tool ceramics.Design/methodology/approach: The methodology includes analysis of the mechanical and functional properties. The Ra parameter was assumed to be the value describing surface roughness. The microhardness tests using the Vickers method were made with use of dynamic ultra microhardness tester. The measurements were made in the „load - unload” mode. Tests of the coatings adhesion to the substrate material was made with use of the scratch test. Surface roughness tests were done both before depositing the coatings and after completing the PVD process. Cutting properties of the investigated materials were determined based on the technological continuous cutting tests of the EN-GJL-250 grey cast iron.Findings: Main properties of the investigated materials were introduced. It has been stated, that properties of the cemented carbides, cermets and oxide tool ceramics with deposited multicomponent (Ti,AlN and gradient Ti(C,N PVD coatings increase in comparison with uncoated material. Multiple increase of tool life result among other things from almost double increase of microhardness of PVD coated materials in comparison with uncoated cemented carbides, cermets and oxide tool ceramics, increasing of thermal and chemical wear resistance and improving of chip formation and removing process’ conditions.Practical implications: Pro-ecological dry cutting processes without the use of the cutting fluids and in the „Near-Net-Shape” technology.Originality/value: Application of multicomponent (Ti,AlN and gradient Ti(C,N types of coatings onto sintered tool materials in order to improve cutting properties of tools.

  17. Chemical Evolution of the Galaxy

    OpenAIRE

    Tosi, M.

    1994-01-01

    Standard models for the chemical evolution of the Galaxy are reviewed with particular emphasis on the history of the abundance gradients in the disk. The effects on the disk structure and metallicity of gas accretion are discussed, showing that a significant fraction of the current disk mass has been accreted in the last Gyrs and that the chemical abundances of the infalling gas can be non primordial but should not exceed 0.3 Z(sun). The distributions with time and with galactocentric distanc...

  18. Optimization of encoding gradients for MR-ARFI.

    Science.gov (United States)

    Chen, Jing; Watkins, Ron; Pauly, Kim Butts

    2010-04-01

    MR acoustic radiation force imaging provides a promising method to monitor therapeutic ultrasound treatments. By measuring the displacement induced by the acoustic radiation force, MR acoustic radiation force imaging can locate the focal spot, without a significant temperature rise. In this work, the encoding gradient for MR acoustic radiation force imaging is optimized to achieve an enhanced accuracy and precision of the displacement measurement. By analyzing the sources of artifacts, bulk motion and eddy currents are shown to introduce errors to the measurement, and heavy diffusion-weighting is shown to result in noisy displacement maps. To eliminate these problems, a new encoding scheme is proposed, which utilizes a pair of bipolar gradients. Improved precision is achieved with robustness against bulk motion and background phase distortion, and improved accuracy is achieved with reduced diffusion-weighting and optimized encoding pulse width. The experiment result shows that the signal-to-noise ratio can be enhanced by more than 2-fold. These significant improvements are obtained at no cost of scan time or encoding sensitivity, enabling the detection of a displacement less than 0.l microm in a gel phantom with MR acoustic radiation force imaging. PMID:20373406

  19. Short wavelength ion temperature gradient turbulence

    OpenAIRE

    Chowdhury, J.; Brunner, S; Ganesh, R.; Lapillonne, X.; Villard, L.; Jenko, F.

    2012-01-01

    The ion temperature gradient (ITG) mode in the high wavenumber regime (k(y)rho(s) > 1), referred to as short wavelength ion temperature gradient mode (SWITG) is studied using the nonlinear gyrokinetic electromagnetic code GENE. It is shown that, although the SWITG mode may be linearly more unstable than the standard long wavelength (k(y)rho(s) < 1) ITG mode, nonlinearly its contribution to the total thermal ion heat transport is found to be low. We interpret this as resulting from an increase...

  20. Electric field gradients in Hg compounds

    DEFF Research Database (Denmark)

    Arcisauskaité, Vaida; Knecht, Stefan; Sauer, Stephan P. A.;

    2012-01-01

    We examine the performance of Density Functional Theory (DFT) approaches based on the Zeroth-Order Regular Approximation (ZORA) Hamiltonian (with and without inclusion of spinorbit coupling) for predictions of electric ¿eld gradients (EFGs) at the heavy atom Hg nucleus. This is achieved by compar......We examine the performance of Density Functional Theory (DFT) approaches based on the Zeroth-Order Regular Approximation (ZORA) Hamiltonian (with and without inclusion of spinorbit coupling) for predictions of electric ¿eld gradients (EFGs) at the heavy atom Hg nucleus. This is achieved...

  1. Gradient Elasticity Formulations for Micro/Nanoshells

    Directory of Open Access Journals (Sweden)

    Bohua Sun

    2014-01-01

    Full Text Available The focus of this paper is on illustrating how to extend the second author’s gradient theory of elasticity to shells. Three formulations are presented based on the implicit gradient elasticity constitutive relation 1 -ld2∇2σij=Cijkl(1-ls2∇2εkl and its two approximations 1+ls2∇2-ld2∇2σij=Cijklεkl and σij=Cijkl(1+ld2∇2-ls2∇2εkl.

  2. Chemotaxis signaling systems in model beneficial plant-bacteria associations.

    Science.gov (United States)

    Scharf, Birgit E; Hynes, Michael F; Alexandre, Gladys M

    2016-04-01

    Beneficial plant-microbe associations play critical roles in plant health. Bacterial chemotaxis provides a competitive advantage to motile flagellated bacteria in colonization of plant root surfaces, which is a prerequisite for the establishment of beneficial associations. Chemotaxis signaling enables motile soil bacteria to sense and respond to gradients of chemical compounds released by plant roots. This process allows bacteria to actively swim towards plant roots and is thus critical for competitive root surface colonization. The complete genome sequences of several plant-associated bacterial species indicate the presence of multiple chemotaxis systems and a large number of chemoreceptors. Further, most soil bacteria are motile and capable of chemotaxis, and chemotaxis-encoding genes are enriched in the bacteria found in the rhizosphere compared to the bulk soil. This review compares the architecture and diversity of chemotaxis signaling systems in model beneficial plant-associated bacteria and discusses their relevance to the rhizosphere lifestyle. While it is unclear how controlling chemotaxis via multiple parallel chemotaxis systems provides a competitive advantage to certain bacterial species, the presence of a larger number of chemoreceptors is likely to contribute to the ability of motile bacteria to survive in the soil and to compete for root surface colonization. PMID:26797793

  3. Urothelial Signaling

    OpenAIRE

    Birder, Lori A.

    2009-01-01

    Beyond serving as a simple barrier, there is growing evidence that the urinary bladder urothelium exhibits specialized sensory properties and play a key role in the detection and transmission of both physiological and nociceptive stimuli. These urothelial cells exhibit the ability to sense changes in their extracellular environment including the ability to respond to chemical, mechanical and thermal stimuli that may communicate the state of the urothelial environment to the underlying nervous...

  4. Gradient Ni-Cr-Mo-Nb surface alloying layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xu [Key Lab. of Beam Technology and Material Modification of Ministry of Education, Inst. of Low Energy Nuclear Physics, Beijing Normal Univ., Beijing Radiation Center, Beijing, BJ (China); Xie Xishan [School of Materials Science and Technology, Univ. of Science and Technology Beijing (China); Xu Zhong [Research Inst. of Surface Engineering, Taiyuan Univ. of Technology (China)

    2003-07-01

    In this paper the gradient surface-alloying layer similar to superalloy Inconel 625 is obtained at the surface of three kind steels (low carbon steel, industrial pure iron, stainless steel 304) by using Double Glow Plasma Surface Alloying Technique. These gradient superalloy surface alloying layers are formed by high temperature diffusion of alloy elements at Double Glow Plasma Surface Alloying. The chemical composition of surface layer can be controlled by source electrode material and technological parameters such as power of source electrode and cathode and processing times etc. The microstructures analyzed by XRD show that the alloying layer consists of {gamma} matrix and some precipitates (Laves intermetallic phase etc.) which depends on the local area composition. The corrosion resistance of nickel base surface alloying layer has been investigated by electrochemical method in 3.5%NaCl and 5%HCl solution. The results indicate: the corrosion resistance of surface alloying layer formed at pure iron substrate is better than that of nickel base superalloy Inconel 625. The results of 200 h exposure tests in 20%H{sub 2}SO{sub 4} and 20%HCl solution show that the corrosion rates of surface alloying layer on pure iron are also equal to that of nickel base alloy Inconel 625 and one order of magnitude lower than that of AISI304 stainless steel. (orig.)

  5. Chemical machining

    Directory of Open Access Journals (Sweden)

    A. Yardimeden

    2007-08-01

    Full Text Available Purpose: Nontraditional machining processes are widely used to manufacture geometrically complex and precision parts for aerospace, electronics and automotive industries. There are different geometrically designed parts, such as deep internal cavities, miniaturized microelectronics and fine quality components may only be produced by nontraditional machining processes. This paper is aiming to give details of chemical machining process, industrial applications, applied chemical etchants and machined materials. Advantages and disadvantages of the chemical machining are mentioned.Design/methodology/approach: In this study, chemical machining process was described its importance as nontraditional machining process. The steps of process were discussed in detail. The tolerances of machined parts were examined.Findings: Paper describes the chemical machining process, industrial applications, applied chemical etchants and machined materials.Practical implications: The machining operation should be carried out carefully to produce a desired geometry. Environmental laws have important effects when chemical machining is used.Originality/value: The importance of nontraditional machining processes is very high.

  6. Chemical Leukoderma.

    Science.gov (United States)

    Bonamonte, Domenico; Vestita, Michelangelo; Romita, Paolo; Filoni, Angela; Foti, Caterina; Angelini, Gianni

    2016-01-01

    Chemical leukoderma, often clinically mimicking idiopathic vitiligo and other congenital and acquired hypopigmentation, is an acquired form of cutaneous pigment loss caused by exposure to a variety of chemicals that act through selective melanocytotoxicity. Most of these chemicals are phenols and aromatic or aliphatic catechols derivatives. These chemicals, however, are harmful for melanocytes in individuals with an individual susceptibility. Nowadays, chemical leukoderma is fairly common, caused by common domestic products. The presence of numerous acquired confetti- or pea-sized macules is clinically characteristic of chemical leukoderma, albeit not diagnostic. Other relevant diagnostic elements are a history of repeated exposure to a known or suspected depigmenting agent at the sites of onset and a macules distribution corresponding to sites of chemical exposure. Spontaneous repigmentation has been reported when the causative agent is avoided; the repigmentation process is perifollicular and gradual, taking place for a variable period of weeks to months. PMID:27172302

  7. Chemical basis for minimal cognition

    DEFF Research Database (Denmark)

    Hanczyc, Martin; Ikegami, Takashi

    We have developed a simple chemical system capable of self-movement in order to study the chemical-molecular origins of movement, perception and cognition. The system consists simply of an oil droplet in an aqueous environment. The aqueous phase contains a surfactant that modulates the interfacial...... tension between the drop of oil and its environment. We embed a chemical reaction in the oil phase that reacts with water when an oily precursor comes in contact with the water phase at the liquidliquid interface. This reaction not only powers the droplet to move in the aqueous phase but also allows for...... convection flow is generated inside the oil droplet to cause the movement, which was also confirmed by simulating the fluid dynamics integrated with chemical reactions (Matsuno et al., 2007, ACAL 07, Springer, p.179, Springer). We can observe that the droplet senses the gradient in the environment (either...

  8. Investigation of open-gradient magnetic separation for Illinois coal

    Energy Technology Data Exchange (ETDEWEB)

    Doctor, R.D.; Livengood, C.D.; Genens, L.E.; Swietlik, C.E.; Foote, K.

    1987-01-01

    Open-gradient magnetic separation (OGMS) using superconducting quadrupole magnets is a novel coal-beneficiation technology offering high pyritic-sulfur removal from pulverized dry coal. The system operates in a continuous mode, uses no chemicals, and has an estimated power demand 75% lower than techniques using conventional electromagnets, while achieving magnetic separation forces up to 267% higher. Specifically applicable to finely ground coal (120 to 325 mesh), OGMS could encourage the commercialization of other developing coal technologies, such as coal-water slurries, fludized-bed combustion, and coal synfuels. Both the experimental program conducted by Argonne National Laboratory and the results of modeling in support of the experimental program are described. 11 refs., 9 figs.

  9. Nonlinear magnetic field gradients can reduce SAR in flow-driven arterial spin labeling measurements

    Science.gov (United States)

    Marro, Kenneth I.; Lee, Donghoon; Hyyti, Outi M.

    2007-03-01

    This work describes how custom-built gradient coils, designed to generate magnetic fields with amplitudes that vary nonlinearly with position, can be used to reduce the potential for unsafe tissue heating during flow-driven arterial spin labeling processes. A model was developed to allow detailed analysis of the adiabatic excitation process used for flow-driven arterial water stimulation with elimination of tissue signal (FAWSETS) an arterial spin labeling method developed specifically for use in skeletal muscle. The model predicted that, by adjusting the amplitude of the gradient field, the specific absorption rate could be reduced by more than a factor of 6 while still achieving effective labeling. Flow phantom measurements and in vivo measurements from exercising rat hind limb confirmed the accuracy of the model's predictions. The modeling tools were also applied to the more widely used continuous arterial spin labeling (CASL) method and predicted that specially shaped gradients could allow similar reductions in SAR.

  10. Magnetic Field Gradient Differentiation of Pedogenic Iron Oxide Minerals From Chinese Loess and Paleosols

    Science.gov (United States)

    Wagoner, L.; Roth, A.; Singer, M. J.; Verosub, K.

    2003-12-01

    The correlation between paleosols and enhanced magnetic susceptibility on the Chinese Loess Plateau is by now well established. However, scant effort has focussed on the interpretation of paleoclimate via the specific iron oxide mineral assemblages contributing to the enhanced magnetic susceptibility signal. This paper focuses on the separation and identification of the pedogenic (minerals from selected loess and paleosol layers of the Loess Plateau. Heretofore, it has been difficult if not impossible to isolate mixed iron oxide mineral phases due to their very similar physical and magnetic properties. Chinese loess and paleosol samples were chosen to illustrate the utility of the technique to natural soil systems. In the following method, initial size separation of mineral particles at 0.5 micron or less by gravity and centrifugation reduces the problem of overlapping magnetic susceptibilities due to mixed grain sizes. The submicron mineral fraction is then subjected to a series of high field gradient (HFG) magnetic separations utilizing a new design. Although HFG magnetic separation methods have been used before, the new design is able to differentiate submicron iron oxide mineral phases from bulk earth material. The design includes a Franz Isodynamic Separator fitted with a custom-made flow cell. A recirculating liquid is used to suspend the mineral particles between the poles of the electromagnet. By varying the strength of the field gradient, recirculation time, and flow velocity, step-wise separation of ferrimagnetic from antiferromagnetic minerals is possible. Because of the tendency for particles to aggregate during recirculation, some mixing of the oxide mineralogy has been unavoidable. Although theoretical arguments favor a narrow grain size distribution (about 50-100 nm) for stable single domain magnetite, in soil environments, and particularly for nanoscale materials, discrete particles are the exception rather than the rule. Therefore it is likely that

  11. Up-gradient transport in a probabilistic transport model

    DEFF Research Database (Denmark)

    Gavnholt, J.; Juul Rasmussen, J.; Garcia, O.E.;

    2005-01-01

    The transport of particles or heat against the driving gradient is studied by employing a probabilistic transport model with a characteristic particle step length that depends on the local concentration or heat gradient. When this gradient is larger than a prescribed critical value, the standard....... These results supplement recent works by van Milligen [Phys. Plasmas 11, 3787 (2004)], which applied Levy distributed step sizes in the case of supercritical gradients to obtain the up-gradient transport. (c) 2005 American Institute of Physics....

  12. Color gradient background oriented schlieren imaging

    Science.gov (United States)

    Mier, Frank Austin; Hargather, Michael

    2015-11-01

    Background oriented schlieren (BOS) imaging is a method of visualizing refractive disturbances through the comparison of digital images. By comparing images with and without a refractive disturbance visualizations can be achieved via a range of image processing methods. Traditionally, backgrounds consist of random distributions of high contrast speckle patterns. To image a refractive disturbance, a digital image correlation algorithm is used to identify the location and magnitude of apparent pixel shifts in the background pattern. Here a novel method of using color gradient backgrounds is explored as an alternative. The gradient background eliminates the need to perform an image correlation between the two digital images, as simple image subtraction can be used to identify the location, magnitude, and direction of the image distortions. This allows for quicker processing. Two-dimensional gradient backgrounds using multiple colors are shown. The gradient backgrounds are demonstrated to provide quantitative data limited only by the camera's pixel resolution, whereas speckle backgrounds limit resolution to the size of the random pattern features and image correlation window size. Additional results include the use of a computer screen as a background.

  13. Checking the Quality of Gradient Magnetic Fields

    Czech Academy of Sciences Publication Activity Database

    Bartušek, Karel; Gescheidtová, E.; Kubásek, R.

    Gliwice : Politechnika Slaska, 2006, s. 207-210. ISBN 83-85940-28-6. [IC-SPETO 2006 International Conference on Fundamentals of Electrotechnics and Circuit Theory /29./. Gliwice (PL), 24.05.2006-27.05.2006] Institutional research plan: CEZ:AV0Z20650511 Keywords : MR * NMR * gradient magnetic field Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  14. Lactate uptake against a concentration gradient

    DEFF Research Database (Denmark)

    Nordström, Carl-Henrik; Nielsen, Troels Halfeld; Nielsen, Hans Boye

    2014-01-01

    The recently published article by Jalloh et al (Jalloh I, Helmy A, Shannon RJ, Gallagher CN, Menon D, Carpenter K, Hutchinson P. Lactate uptake by the injured human brain - evidence from an arterio-venous gradient and cerebral microdialysis study. J Neurotrauma. 2013 Aug 22. [Epub ahead of print]...... is of fundamental importance the misconception should be corrected....

  15. Joining of Tungsten Armor Using Functional Gradients

    International Nuclear Information System (INIS)

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  16. 40 CFR 230.25 - Salinity gradients.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Salinity gradients. 230.25 Section 230.25 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING SECTION 404(b)(1) GUIDELINES FOR SPECIFICATION OF DISPOSAL SITES FOR DREDGED OR FILL MATERIAL Potential Impacts...

  17. CMB anisotropies from a gradient mode

    Science.gov (United States)

    Mirbabayi, Mehrdad; Zaldarriaga, Matias

    2015-03-01

    A linear gradient mode must have no observable dynamical effect on short distance physics. We confirm this by showing that if there was such a gradient mode extending across the whole observable Universe, it would not cause any hemispherical asymmetry in the power of CMB anisotropies, as long as Maldacena's consistency condition is satisfied. To study the effect of the long wavelength mode on short wavelength modes, we generalize the existing second order Sachs-Wolfe formula in the squeezed limit to include a gradient in the long mode and to account for the change in the location of the last scattering surface induced by this mode. Next, we consider effects that are of second order in the long mode. A gradient mode Φ = qṡx generated in Single-field inflation is shown to induce an observable quadrupole moment. For instance, in a matter-dominated model it is equal to Q = 5(qṡx)2/18. This quadrupole can be canceled by superposition of a quadratic perturbation. The result is shown to be a nonlinear extension of Weinberg's adiabatic modes: a long-wavelength physical mode which looks locally like a coordinate transformation.

  18. Conformally Coupled Induced Gravity with Gradient Torsion

    OpenAIRE

    Yoon, Yongsung

    1999-01-01

    It is found that conformally coupled induced gravity with gradient torsion gives a dilaton gravity in Riemann geometry. In the Einstein frame of the dilaton gravity the conformal symmetry is hidden and a non-vanishing cosmological constant is not plausible due to the constraint of the conformal coupling.

  19. Gravity gradient torque of spacecraft orbiting asteroids

    CERN Document Server

    Wang, Yue

    2013-01-01

    Purpose: This paper presents a full fourth-order model of the gravity gradient torque of spacecraft around asteroids by taking into consideration of the inertia integrals of the spacecraft up to the fourth order, which is an improvement of the previous fourth-order model of the gravity gradient torque. Design, methodology and approach: The fourth-order gravitational potential of the spacecraft is derived based on Taylor expansion. Then the expression of the gravity gradient torque in terms of gravitational potential derivatives is derived. By using the formulation of the gravitational potential, explicit formulations of the full fourth-order gravity gradient torque are obtained. Then a numerical simulation is carried out to verify our model. Findings: We find that our model is more sound and precise than the previous fourth-order model due to the consideration of higher-order inertia integrals of the spacecraft. Numerical simulation results show that the motion of the previous fourth-order model is quite diff...

  20. Examining the Education Gradient in Chronic Illness

    Science.gov (United States)

    Chatterji, Pinka; Joo, Heesoo; Lahiri, Kajal

    2015-01-01

    We examine the education gradient in diabetes, hypertension, and high cholesterol. We take into account diagnosed as well as undiagnosed cases and use methods accounting for the possibility of unmeasured factors that are correlated with education and drive both the likelihood of having illness and the propensity to be diagnosed. Data come from the…

  1. Ocean thermal gradient hydraulic power plant.

    Science.gov (United States)

    Beck, E J

    1975-07-25

    Solar energy stored in the oceans may be used to generate power by exploiting ploiting thermal gradients. A proposed open-cycle system uses low-pressure steam to elevate vate water, which is then run through a hydraulic turbine to generate power. The device is analogous to an air lift pump. PMID:17813707

  2. Natural equivalents of thermal gradient experiments

    Science.gov (United States)

    Rodríguez, Carmen; Geyer, Adelina; Castro, Antonio; Villaseñor, Antonio

    2015-06-01

    Crystallization experiments using the intrinsic thermal gradient in 10 mm length capsules loaded in piston-cylinder assemblies were used to investigate silicic magma crystallization. The application of experimental results to natural environments requires the scaling of physical parameters of petrological interest. Therefore, we propose here a comparative study between thermal gradients and numerical simulations of natural magma chambers. We use the Finite Element method to calculate thermal profiles across a cooling silicic magma chamber. These numerical profiles are compared with the intrinsic thermal structure of half-inch, piston-cylinder assemblies at 500 MPa. It is concluded that a set of varied magma chamber geometries and/or distinct stages of their cooling history can approach the intrinsic thermal structure of laboratory experiments. Once the thermal properties for magma and its host rock are fixed, the experimental-numerical approach is mostly dependent on the volume and aspect ratio of the magma chamber. Our results indicate, for instance, that a 10 mm length capsule with a thermal gradient of 40 °C/mm (from 1100 to 700 °C) may represent a 150-1100 m wide portion of a cooling magma chamber of 10-20 km diameter and 2-10 km height, emplaced at a depth of 18 km. Additional possible scenarios are represented by larger magma chambers, up to 30 km diameter, in which the experimental thermal gradient can represent a 150-3700 m-thin-section of the large igneous bodies.

  3. Strain gradient plasticity: energetic or dissipative?

    Science.gov (United States)

    Fleck, N. A.; Willis, J. R.

    2015-08-01

    For an infinite slab of strain gradient sensitive material subjected to plane-strain tensile loading, computation established and analysis confirmed that passivation of the lateral boundaries at some stage of loading inhibits plastic deformation upon further loading. This result is not surprising in itself except that, remarkably, if the gradient terms contribute to the dissipation, the plastic deformation is switched off completely and only resumes at a clearly defined higher load, corresponding to a total strain , say. The analysis presented in this paper confirms the delay of plastic deformation following passivation and determines the exact manner in which the plastic flow resumes. The plastic strain rate is continuous at the exact point of resumption of plastic flow and, for the first small increment in the imposed total strain, the corresponding increment in plastic strain, , is proportional to . The constant A in the relation , where denotes the plastic strain increment at the centre of the slab, has been determined explicitly; it depends on the hardening modulus of the material. The presence of energetic gradient terms has no effect on the value of unless the dissipative terms are absent, in which case passivation reduces the rate of plastic deformation but introduces no delay. This qualitative effect of dissipative gradient terms opens the possibility of experimental discrimination of their presence or absence. The analysis employs an incremental variational formulation that is likely to find use in other problems.

  4. Use of high gradient magnetic separation for actinide application

    International Nuclear Information System (INIS)

    Decontamination of materials such as soils or waste water that contain radioactive isotopes, heavy metals, or hazardous components is a subject of great interest. Magnetic separation is a physical separation process that segregates materials on the basis of magnetic susceptibility. Because the process relies on physical properties, separations can be achieved while producing a minimum of secondary waste. Most traditional physical separation processes effectively treat particles larger than 70 microns. In many situations, the radioactive contaminants are found concentrated in the fine particle size fraction of less than 20 microns. For effective decontamination of the fine particle size fraction most current operations resort to chemical dissolution methods for treatment. High gradient magnetic separation (HGMS) is able to effectively treat particles from 90 to ∼0.1 micron in diameter. The technology is currently used on the 60 ton per hour scale in the kaolin clay industry. When the field gradient is of sufficiently high intensity, paramagnetic particles can be physically captured and separated from extraneous nonmagnetic material. Because all actinide compounds are paramagnetic, magnetic separation of actinide containing mixtures is feasible. The advent of reliable superconducting magnets also makes magnetic separation of weakly paramagnetic species attractive. HGMS work at Los Alamos National Laboratory (LANL) is being developed for soil remediation, waste water treatment and treatment of actinide chemical processing residues. LANL and Lockheed Environmental Systems and Technologies Company (LESAT) have worked on a co-operative research and development agreement (CRADA) to develop HGMS for radioactive soil decontamination. The program is designed to transfer HGMS from the laboratory and other industries for the commercial treatment of radioactive contaminated materials. 9 refs., 2 figs., 2 tabs

  5. Capture of metallic copper by high gradient magnetic separation system.

    Science.gov (United States)

    Wu, Wan-I; Wu, Chung-Hsin; Hong, P K Andy; Lin, Cheng-Fang

    2011-10-01

    Valence copper was recovered from wastewater by chemical reduction and use of a high gradient magnetic separation (HGMS) system. Ammonia (NH3) and sodium dithionate (Na2S2O4) at a molar ratio of [Cu]:[NH3]:[Na2S2O4] = 1:4:3 at pH = 9.5 were used first to chemically reduce copper ion to metallic copper; the resultant metal solids were captured in an upflowing reactor space equipped with a permalloy matrix net under a high gradient magnetic field. The captured solids were predominantly 6-20 microm in diameter, with Cu2O and CuO present among the solids. Four treatment configurations with and without the use of magnetic field and metal alloy as the matrix net were tested and their effects evaluated: (1) no magnetic field or matrix, (2) no magnetic field but with matrix, (3) with magnetic field but no matrix, (4) with both magnetic field and matrix. At flow rates of 40, 60, 80 and 100 cm3/min, capture efficiencies for metallic copper in the absence of magnetic field were 87%, 86%, 63%, and 39%, respectively, and in the presence of magnetic field were 99%, 98%, 95%, and 93%, respectively. The HGMS was critical for a high capture efficiency, whereas a matrix net only marginally enhanced it. Additional tests with a larger reactor confirmed similarly high efficiencies of > 85%. The use of an alloy matrix appeared to be important when high flow rates are most likely to be employed in practical applications. PMID:22329132

  6. An Initial Investigation of Ionospheric Gradients for Detection of Ionospheric Disturbances over Turkey

    Science.gov (United States)

    Koroglu, Meltem; Arikan, Feza; Koroglu, Ozan

    2015-04-01

    Ionosphere is an ionized layer of earth's atmosphere which affect the propagation of radio signals due to highly varying electron density structure. Total Electron Content (TEC) and Slant Total Electron Content (STEC) are convenient measures of total electron density along a ray path. STEC model is given by the line integral of the electron density between the receiver and GPS satellite. TEC and STEC can be estimated by observing the difference between the two GPS signal time delays that have different frequencies L1 (1575 MHz) and L2 (1227 MHz). During extreme ionospheric storms ionospheric gradients becomes larger than those of quiet days since time delays of the radio signals becomes anomalous. Ionosphere gradients can be modeled as a linear semi-infinite wave front with constant propagation speed. One way of computing the ionospheric gradients is to compare the STEC values estimated between two neighbouring GPS stations. In this so-called station-pair method, ionospheric gradients are defined by dividing the difference of the time delays of two receivers, that see the same satellite at the same time period. In this study, ionospheric gradients over Turkey are computed using the Turkish National Permanent GPS Network (TNPGN-Active) between May 2009 and September 2012. The GPS receivers are paired in east-west and north-south directions with distances less than 150 km. GPS-STEC for each station are calculated using IONOLAB-TEC and IONOLAB-BIAS softwares (www.ionolab.org). Ionospheric delays are calculated for each paired station for both L1 and L2 frequencies and for each satellite in view with 30 s time resolution. During the investigation period, different types of geomagnetic storms, Travelling Ionospheric Disturbances (TID), Sudden Ionospheric Disturbances (SID) and various earthquakes with magnitudes between 3 to 7.4 have occured. Significant variations in the structure of station-pair gradients have been observed depending on location of station-pairs, the

  7. Inventory Signals

    OpenAIRE

    Lai, Richard

    2006-01-01

    Among practitioners, inventory is often thought to be the root of all evil in operations management. The stock market hates it, the media abhors it, and managers have come to fear it. But high inventory levels can also be the result of strategic buying and high-availability strategies. The problem is that when the market sees lots of inventory, it cannot tell whether it is because of poor or smart operations. We hypothesize that inventory has a signaling role. In our model, publicly- traded f...

  8. Sequential Phosphorylation of Smoothened Transduces Graded Hedgehog Signaling

    OpenAIRE

    Su, Ying; Ospina, Jason K.; Zhang, Junzheng; Michelson, Andrew P.; Schoen, Adam M.; Zhu, Alan Jian

    2011-01-01

    The correct interpretation of a gradient of the morphogen Hedgehog (Hh) during development requires phosphorylation of the Hh signaling activator Smoothened (Smo); however, the molecular mechanism by which Smo transduces graded Hh signaling is not well understood. We show that regulation of the phosphorylation status of Smo by distinct phosphatases at specific phosphorylated residues creates differential thresholds of Hh signaling. Phosphorylation of Smo was initiated by adenosine 3′,5′-monop...

  9. Cells as Active Particles in Asymmetric Potentials: Motility under External Gradients

    Science.gov (United States)

    Comelles, Jordi; Caballero, David; Voituriez, Raphaël; Hortigüela, Verónica; Wollrab, Viktoria; Godeau, Amélie Luise; Samitier, Josep; Martínez, Elena; Riveline, Daniel

    2014-01-01

    Cell migration is a crucial event during development and in disease. Mechanical constraints and chemical gradients can contribute to the establishment of cell direction, but their respective roles remain poorly understood. Using a microfabricated topographical ratchet, we show that the nucleus dictates the direction of cell movement through mechanical guidance by its environment. We demonstrate that this direction can be tuned by combining the topographical ratchet with a biochemical gradient of fibronectin adhesion. We report competition and cooperation between the two external cues. We also quantitatively compare the measurements associated with the trajectory of a model that treats cells as fluctuating particles trapped in a periodic asymmetric potential. We show that the cell nucleus contributes to the strength of the trap, whereas cell protrusions guided by the adhesive gradients add a constant tunable bias to the direction of cell motion. PMID:25296303

  10. Chemical networks*

    OpenAIRE

    Thi Wing-Fai

    2015-01-01

    This chapter discusses the fundamental ideas of how chemical networks are build, their strengths and limitations. The chemical reactions that occur in disks combine the cold phase reactions used to model cold molecular clouds with the hot chemistry applied to planetary atmosphere models. With a general understanding of the different types of reactions that can occur, one can proceed in building a network of chemical reactions and use it to explain the abundance of species seen in disks. One o...

  11. Microsphere-Based Scaffolds Carrying Opposing Gradients of Chondroitin Sulfate and Tricalcium Phosphate

    Directory of Open Access Journals (Sweden)

    Vineet eGupta

    2015-07-01

    Full Text Available Extracellular matrix (ECM components such as chondroitin sulfate (CS and tricalcium phosphate (TCP serve as raw materials and thus spatial patterning of these raw materials may be leveraged to mimic the smooth transition of physical, chemical and mechanical properties at the bone-cartilage interface. We hypothesized that encapsulation of opposing gradients of these raw materials in high molecular weight poly(D,L-lactic-co-glycolic acid (PLGA microsphere-based scaffolds would enhance differentiation of rat bone marrow stromal cells (rBMSCs. The raw material encapsulation altered the microstructure of the microspheres and also influenced the cellular morphology that depended on the type of material encapsulated. Moreover, the mechanical properties of the raw material encapsulating microsphere-based scaffolds initially relied on the composition of the scaffolds and later on were primarily governed by the degradation of the polymer phase and newly synthesized extracellular matrix by the seeded cells. Furthermore, raw materials had a mitogenic effect on the seeded cells and led to increased glycosaminoglycan (GAG, collagen, and calcium content. Interestingly, the initial effects of raw material encapsulation on a per-cell basis might have been overshadowed by medium-regulated environment that appeared to favor osteogenesis. However, it is to be noted that in vivo, differentiation of the cells would be governed by the surrounding native environment. Thus, the results of this study demonstrated the potential of the raw materials in facilitating neo-tissue synthesis in microsphere-based scaffolds and perhaps in combination with bioactive signals, these raw materials may be able to achieve intricate cell differentiation profiles required for regenerating the osteochondral interface.

  12. Microfluidic gradient device for studying mesothelial cell migration and the effect of chronic carbon nanotube exposure

    International Nuclear Information System (INIS)

    Cell migration is one of the crucial steps in many physiological and pathological processes, including cancer development. Our recent studies have shown that carbon nanotubes (CNTs), similarly to asbestos, can induce accelerated cell growth and invasiveness that contribute to their mesothelioma pathogenicity. Malignant mesothelioma is a very aggressive tumor that develops from cells of the mesothelium, and is most commonly caused by exposure to asbestos. CNTs have a similar structure and mode of exposure to asbestos. This has raised a concern regarding the potential carcinogenicity of CNTs, especially in the pleural area which is a key target for asbestos-related diseases. In this paper, a static microfluidic gradient device was applied to study the migration of human pleural mesothelial cells which had been through a long-term exposure (4 months) to subcytotoxic concentration (0.02 µg cm−2) of single-walled CNTs (SWCNTs). Multiple migration signatures of these cells were investigated using the microfluidic gradient device for the first time. During the migration study, we observed that cell morphologies changed from flattened shapes to spindle shapes prior to their migration after their sensing of the chemical gradient. The migration of chronically SWCNT-exposed mesothelial cells was evaluated under different fetal bovine serum (FBS) concentration gradients, and the migration speeds and number of migrating cells were extracted and compared. The results showed that chronically SWCNT-exposed mesothelial cells are more sensitive to the gradient compared to non-SWCNT-exposed cells. The method described here allows simultaneous detection of cell morphology and migration under chemical gradient conditions, and also allows for real-time monitoring of cell motility that resembles in vivo cell migration. This platform would be much needed for supporting the development of more physiologically relevant cell models for better assessment and characterization of the

  13. Microfluidic gradient device for studying mesothelial cell migration and the effect of chronic carbon nanotube exposure

    Science.gov (United States)

    Zhang, Hanyuan; Lohcharoenkal, Warangkana; Sun, Jianbo; Li, Xiang; Wang, Liying; Wu, Nianqiang; Rojanasakul, Yon; Liu, Yuxin

    2016-01-01

    Cell migration is one of the crucial steps in many physiological and pathological processes, including cancer development. Our recent studies have shown that carbon nanotubes (CNTs), similarly to asbestos, can induce accelerated cell growth and invasiveness that contribute to their mesothelioma pathogenicity. Malignant mesothelioma is a very aggressive tumor that develops from cells of the mesothelium, and is most commonly caused by exposure to asbestos. CNTs have a similar structure and mode of exposure to asbestos. This has raised a concern regarding the potential carcinogenicity of CNTs, especially in the pleural area which is a key target for asbestos-related diseases. In this paper, a static microfluidic gradient device was applied to study the migration of human pleural mesothelial cells which had been through a long-term exposure (4 months) to subcytotoxic concentration (0.02 μg cm−2) of single-walled CNTs (SWCNTs). Multiple migration signatures of these cells were investigated using the microfluidic gradient device for the first time. During the migration study, we observed that cell morphologies changed from flattened shapes to spindle shapes prior to their migration after their sensing of the chemical gradient. The migration of chronically SWCNT-exposed mesothelial cells was evaluated under different fetal bovine serum (FBS) concentration gradients, and the migration speeds and number of migrating cells were extracted and compared. The results showed that chronically SWCNT-exposed mesothelial cells are more sensitive to the gradient compared to non-SWCNT-exposed cells. The method described here allows simultaneous detection of cell morphology and migration under chemical gradient conditions, and also allows for real-time monitoring of cell motility that resembles in vivo cell migration. This platform would be much needed for supporting the development of more physiologically relevant cell models for better assessment and characterization of the

  14. The effects of eluent's optothermal parameters on TLS detection in gradient HPLC

    Science.gov (United States)

    Kožar Logar, J.; Franko, M.

    2003-01-01

    The effects of changing solvent composition on the limits of detection (LOD) of thermal lens spectroscopy (TLS) detection in gradient elution HPLC have been studied from the perspective of solvent's thermooptical properties. The refractive index and the temperature dependence of refractive index were measured and are reported for the first time for the methanol-acetone and methanol-ammonium acetate solutions used in this work, and some other methanol based chromatographic eluents. The TLS signal noise during a gradient HPLC protocol is increasing and its value reaches the maximum with a considerable time delay (up to 3 min) compared to the end point of the gradient protocol. The length of the chromatographic column was found to be an important parameter in reduction of signal noise resulting from incomplete solvent mixing. For some carotenoids the LOD values on the order of 50-100 pg/mL can be obtained on a 25 cm column with solvents that yield an increase in TLS enhancement factor up to 1.6 times during the gradient HPLC analysis.

  15. Leishmania amazonensis chemotaxis under glucose gradient studied by the strength and directionality of forces measured with optical tweezers

    Science.gov (United States)

    de Ysasa Pozzo, Liliana; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz Carlos; Ayres, Diana Copi; Giorgio, Selma; Cesar, Carlos Lenz

    2007-02-01

    Chemotaxis is the mechanism microorganisms use to sense the environment surrounding them and to direct their movement towards attractive, or away from the repellent, chemicals. The biochemical sensing is almost the only way for communication between unicellular organisms. Prokaryote and Eukaryote chemotaxis has been mechanically studied mainly by observing the directionality and timing of the microorganisms movements subjected to a chemical gradient, but not through the directionality and strength of the forces it generates. To observe the vector force of microorganisms under a chemical gradient we developed a system composed of two large chambers connected by a tiny duct capable to keep the chemical gradient constant for more than ten hours. We also used the displacements of a microsphere trapped in an Optical Tweezers as the force transducer to measure the direction and the strength of the propulsion forces of flagellum of the microorganism under several gradient conditions. A 9μm diameter microsphere particle was trapped with a Nd:YAG laser and its movement was measured through the light scattered focused on a quadrant detector. We observed the behavior of the protozoa Leishmania amazonensis (eukaryote) under several glucose gradients. This protozoa senses the gradient around it by swimming in circles for three to five times following by tumbling, and not by the typical straight swimming/tumbling of bacteria. Our results also suggest that force direction and strength are also used to control its movement, not only the timing of swimming/tumbling, because we observed a higher force strength clearly directed towards the glucose gradient.

  16. Chemical differentiation of planets: a core issue

    OpenAIRE

    Toulhoat, Herve; Beaumont, Valerie; Zgonnik, Viacheslav; Larin, Nikolay; Larin, Vladimir N.

    2012-01-01

    Prevalent theories of the Solar System formation minimize the role of matter ionization and magnetic field in the Solar nebula. Instead, we propose that a magnetically driven chemical gradient at the scale of the Solar nebula has imprinted chemical differentiation of planets in the further accretion stages. For a given planet, we theoretically relate element abundances relative to Sun to first ionization potentials and distance to Sun. This simple model is successfully tested against availabl...

  17. Encoding of electrophysiology and other signals in MR images

    DEFF Research Database (Denmark)

    Hanson, Lars G; Lund, Torben E; Hanson, Christian G

    2007-01-01

    PURPOSE: To develop a gradient insensitive, generic technique for recording of non-MR signals by use of surplus scanner bandwidth. MATERIALS AND METHODS: Relatively simple battery driven hardware is used to transform one or more signals into radio waves detectable by the MR scanner. Similar...... to the "magstripe" technique used for encoding of soundtracks in motion pictures, the electrical signals are in this way encoded as artifacts appearing in the MR images or spectra outside the region of interest. The encoded signals are subsequently reconstructed from the signal recorded by the scanner. RESULTS...

  18. Limits to Chemically Guided Multicellular Migration

    Science.gov (United States)

    Varennes, Julien; Han, Bumsoo; Mugler, Andrew

    Collective cell migration in response to a chemical cue requires both multicellular sensing of chemical gradients and coordinated mechanical action. Examples from morphogenesis and cancer metastasis demonstrate that clusters of migratory cells are extremely sensitive, responding to gradients of less than 1% difference in chemical concentration across a cell body. While the limits to multicellular sensing are becoming known, the ensuing consequences for coherent migration remain poorly understood. We develop a model of multicellular sensing and migration based on the cellular Potts model. Multicellular sensing of noisy chemical gradients is modeled as a process of local excitation and global inhibition (LEGI) among communicating cells. The output of the sensing process is coupled to individual cells' polarization to model migratory behavior. We find that larger clusters of cells detect the gradient direction with higher precision and thus achieve stronger polarization bias. At the same time, larger clusters are also accompanied by less coherent collective motion. The trade-off between these two effects leads to an optimally efficient cluster size. We discuss how our results relate to cancer metastasis.

  19. Effect of Elongation on Critical Gradient for Toroidal Electron Temperature Gradient Modes

    Institute of Scientific and Technical Information of China (English)

    PENG Li-Li; GAO Zhe

    2008-01-01

    The electron temperature gradient mode is investigated in elongated toroidal plasmas with a gyrokinetic integral eigenmode equation code. Dependence of the critical electron temperature gradient on the elongation is calculated.It is found that when the elongation increases, the growth rate spectrum is greatly shifted towards shorter poloidal wavelength, and then the poloidal wavenumber at which the mode is destabilizing critically in elongated plasmas will be larger than that in circular plasmas.

  20. Synthesis and characterization of chemically functionalized shape memory nanofoams for unattended sensing applications

    Science.gov (United States)

    Soliani, Anna Paola

    The work in this dissertation is devoted to the synthesis and characterization of novel materials for off-line unattended sensing: shape-memory grafted nanofoams. The fabrication process and characterization of highly efficient, polymeric nanosensor element with the ability to selectively detect analytes and retain memory of specific exposure events is reported. These shape memory nanofoams could potentially act as efficient and highly sensitive coatings for evanescent waveguide-based optical monitoring systems. On exposure to specific analytes, the polymeric coatings locally change their internal structure irreversibly at the nanolevel, affecting the local optical properties such as refractive index. Currently, enrichment polymer layers (EPLs) are currently being used to detect of chemical vapors. EPLs are thin polymer films that can increase signal of an analyte through absorption. These films are designed to interact with analytes via chemical interactions while this analyte is present in the environment. Once the analyte is removed from the environment surrounding the EPL, these EPLs have no residual memory of the interaction(s). This dissertation will address this limitation in the field of chemical unattended sensing through the use of functionalized polymeric films that possess ability to retain memory of analyte exposure. Specifically, we will use chemically cross-linked gradient nanofoam as a material with built-in analyte-specific sensing properties. A novel method has been created to fabricate chemically functionalized shape memory nanofoams. First, a polymer film containing epoxy groups is deposited onto a substrate. Then, the film is cross-linked via reaction of the epoxy groups to create a non-soluble, yet swellable coating. This film is then treated with specific chemical substances capable of reacting with the epoxy functionalities. This procedure is necessary to convert the epoxy groups into various functional moieties. This process generates a

  1. Characterization of Soil Quality Under Vegetable Production Along an Urban-Rural Gradient

    Institute of Scientific and Technical Information of China (English)

    ZHANG MINGKUI; WANG MEIQING; LIU XINGMEI; JIANG HONG; XU JIANMING

    2003-01-01

    Human activity and urbanization result in urban-rural environmental gradients. Understanding effect of the gradients on soil properties is necessary for management of the soils around urban areas. In this study, soil quality of some vegetable fields was characterized along an urban-rural gradient in Shaoxing County, Zhejiang Province. Fifteen soil physical and chemical properties were evaluated by using principal component analysis.Results showed that there was a great variation in the soil quality along the gradient. From rural to urban zones, soil organic matter, water-stable aggregates, cation exchangeable capacity (CEC), total N and P, and available K increased, whereas soil pH value decreased. In addition, Pb, Cu, Ni, Co, Zn and Cr in the soils tended to be accumulated toward the urban zone. Sequential chemical extraction showed that mobility of all the heavy metals in the soils tended to increase from the rural to the urban zones. The variation of soil properties accounted for by the first principal component was significantly explained by the difference in application rates of municipal wastes.

  2. Oscillatory behavior of neutrophils under opposing chemoattractant gradients supports a winner-take-all mechanism.

    Directory of Open Access Journals (Sweden)

    Matthew B Byrne

    Full Text Available Neutrophils constitute the largest class of white blood cells and are the first responders in the innate immune response. They are able to sense and migrate up concentration gradients of chemoattractants in search of primary sites of infection and inflammation through a process known as chemotaxis. These chemoattractants include formylated peptides and various chemokines. While much is known about chemotaxis to individual chemoattractants, far less is known about chemotaxis towards many. Previous studies have shown that in opposing gradients of intermediate chemoattractants (interleukin-8 and leukotriene B4, neutrophils preferentially migrate toward the more distant source. In this work, we investigated neutrophil chemotaxis in opposing gradients of chemoattractants using a microfluidic platform. We found that primary neutrophils exhibit oscillatory motion in opposing gradients of intermediate chemoattractants. To understand this behavior, we constructed a mathematical model of neutrophil chemotaxis. Our results suggest that sensory adaptation alone cannot explain the observed oscillatory motion. Rather, our model suggests that neutrophils employ a winner-take-all mechanism that enables them to transiently lock onto sensed targets and continuously switch between the intermediate attractant sources as they are encountered. These findings uncover a previously unseen behavior of neutrophils in opposing gradients of chemoattractants that will further aid in our understanding of neutrophil chemotaxis and the innate immune response. In addition, we propose a winner-take-all mechanism allows the cells to avoid stagnation near local chemical maxima when migrating through a network of chemoattractant sources.

  3. Corrosion resistance of duplex and gradient CrNx coated H13 steel

    International Nuclear Information System (INIS)

    The electrochemical behavior of H13 steel coated with duplex and gradient CrNx coatings deposited by cathodic arc deposition has been studied. The substrate material was coated with CrN by cathodic arc deposition technique. Duplex layers of CrNx, which normally include an interlayer approximately 100-200 nm of Cr under the main CrN coating, were prepared; gradient CrNx coating were produced with continuous elevated nitrogen pressure. The X-ray photoelectron spectroscopy (XPS) was applied to characterize the chemical composition, and the glancing angle X-ray diffraction (GAXRD) was used to examine the crystallographic structure. The potentiodynamic polarization was examined by Zahner IM6e electrochemical workstation in a 0.5 M H2SO4 solution at ambient temperature, and the corrosive surface was detected by scanning electron microscopy (SEM). It was shown that the gradient coating could enhance the corrosion performance of CrNx coated H13 steel. The corrosion resistance improvement was not only attributed to the increase in thickness, but also to the internal microstructure and phase composition. Gradient CrNx coating produced in this work was proved to be particularly promising in terms of corrosion resistance, owing to its incontinuous pinholes and different composition: Cr, Cr2N in inner part and CrN in surface. The results showed that the gradient coating had an improved electrochemical performance than duplex CrN coating

  4. Temperature gradients drive mechanical energy gradients in the flight muscle of Manduca sexta.

    Science.gov (United States)

    George, N T; Sponberg, S; Daniel, T L

    2012-02-01

    A temperature gradient throughout the dominant flight muscle (dorsolongitudinal muscle, DLM(1)) of the hawkmoth Manduca sexta, together with temperature-dependent muscle contractile rates, demonstrates that significant spatial variation in power production is possible within a single muscle. Using in situ work-loop analyses under varying muscle temperatures and phases of activation, we show that regional differences in muscle temperature will induce a spatial gradient in the mechanical power output throughout the DLM(1). Indeed, we note that this power gradient spans from positive to negative values across the predicted temperature range. Warm ventral subunits produce positive power at their in vivo operating temperatures, and therefore act as motors. Concurrently, as muscle temperature decreases dorsally, the subunits produce approximately zero mechanical power output, acting as an elastic energy storage source, and negative power output, behaving as a damper. Adjusting the phase of activation further influences the temperature sensitivity of power output, significantly affecting the mechanical power output gradient that is expressed. Additionally, the separate subregions of the DLM(1) did not appear to employ significant physiological compensation for the temperature-induced differences in power output. Thus, although the components of a muscle are commonly thought to operate uniformly, a significant within-muscle temperature gradient has the potential to induce a mechanical power gradient, whereby subunits within a muscle operate with separate and distinct functional roles. PMID:22246256

  5. Chemical machining

    OpenAIRE

    A. Yardimeden; T. Ozben; O. Cakir

    2007-01-01

    Purpose: Nontraditional machining processes are widely used to manufacture geometrically complex and precision parts for aerospace, electronics and automotive industries. There are different geometrically designed parts, such as deep internal cavities, miniaturized microelectronics and fine quality components may only be produced by nontraditional machining processes. This paper is aiming to give details of chemical machining process, industrial applications, applied chemical etchants and mac...

  6. Comparison of Adaptive Antenna Arrays Controlled by Gradient Algorithms

    Directory of Open Access Journals (Sweden)

    Z. Raida

    1994-09-01

    Full Text Available The paper presents the Simple Kalman filter (SKF that has been designed for the control of digital adaptive antenna arrays. The SKF has been applied to the pilot signal system and the steering vector one. The above systems based on the SKF are compared with adaptive antenna arrays controlled by the classical LMS and the Variable Step Size (VSS LMS algorithms and by the pure Kalman filter. It is shown that the pure Kalman filter is the most convenient for the control of the adaptive arrays because it does not require any a priori information about noise statistics and excels in high rate of convergence and low misadjustment. Extremely high computational requirements are drawback of this filter. Hence, if low computational power of signal processors is at the disposal, the SKF is recommended to be used. Computational requirements of the SKF are of the same order as the classical LMS algorithm exhibits. On the other hand, all the important features of the pure Kalman filter are inherited by the SKF. The paper shows that presented Kalman filters can be regarded as special gradient algorithms. That is why they can be compared with the LMS family.

  7. Obtaining reliable phase-gradient delays from otoacoustic emission data.

    Science.gov (United States)

    Shera, Christopher A; Bergevin, Christopher

    2012-08-01

    Reflection-source otoacoustic emission phase-gradient delays are widely used to obtain noninvasive estimates of cochlear function and properties, such as the sharpness of mechanical tuning and its variation along the length of the cochlear partition. Although different data-processing strategies are known to yield different delay estimates and trends, their relative reliability has not been established. This paper uses in silico experiments to evaluate six methods for extracting delay trends from reflection-source otoacoustic emissions (OAEs). The six methods include both previously published procedures (e.g., phase smoothing, energy-weighting, data exclusion based on signal-to-noise ratio) and novel strategies (e.g., peak-picking, all-pass factorization). Although some of the methods perform well (e.g., peak-picking), others introduce substantial bias (e.g., phase smoothing) and are not recommended. In addition, since standing waves caused by multiple internal reflection can complicate the interpretation and compromise the application of OAE delays, this paper develops and evaluates two promising signal-processing strategies, the first based on time-frequency filtering using the continuous wavelet transform and the second on cepstral analysis, for separating the direct emission from its subsequent reflections. Altogether, the results help to resolve previous disagreements about the frequency dependence of human OAE delays and the sharpness of cochlear tuning while providing useful analysis methods for future studies. PMID:22894215

  8. Soil Organic Matter Dynamics Along Gradients in Temperature and Land Use on the Island of Hawaii

    OpenAIRE

    Townsend, Alan R; Vitousek, Peter M.; Trumbore, Susan E.

    1995-01-01

    We studied soil organic matter (SOM) dynamics in allophanic soils (Udands) along independent gradients of temperature (altitude) and land use (forest-pasture) on the island of Hawaii. Using an integrated ^1^3C signal derived from land conversion along with measurements of soil respiration and soil carbon, we separated rapid, intermediate, and very slow turnover SOM pools, and estimated turnover times for the large intermediate pool. These estimates were compared to independent estimates using...

  9. Signal processing by the endosomal system.

    Science.gov (United States)

    Villaseñor, Roberto; Kalaidzidis, Yannis; Zerial, Marino

    2016-04-01

    Cells need to decode chemical or physical signals from their environment in order to make decisions on their fate. In the case of signalling receptors, ligand binding triggers a cascade of chemical reactions but also the internalization of the activated receptors in the endocytic pathway. Here, we highlight recent studies revealing a new role of the endosomal network in signal processing. The diversity of entry pathways and endosomal compartments is exploited to regulate the kinetics of receptor trafficking, and interactions with specific signalling adaptors and effectors. By governing the spatio-temporal distribution of signalling molecules, the endosomal system functions analogously to a digital-analogue computer that regulates the specificity and robustness of the signalling response. PMID:26921695

  10. Gradient Artefact Correction and Evaluation of the EEG Recorded Simultaneously with fMRI Data Using Optimised Moving-Average

    Directory of Open Access Journals (Sweden)

    José L. Ferreira

    2016-01-01

    Full Text Available Over the past years, coregistered EEG-fMRI has emerged as a powerful tool for neurocognitive research and correlated studies, mainly because of the possibility of integrating the high temporal resolution of the EEG with the high spatial resolution of fMRI. However, additional work remains to be done in order to improve the quality of the EEG signal recorded simultaneously with fMRI data, in particular regarding the occurrence of the gradient artefact. We devised and presented in this paper a novel approach for gradient artefact correction based upon optimised moving-average filtering (OMA. OMA makes use of the iterative application of a moving-average filter, which allows estimation and cancellation of the gradient artefact by integration. Additionally, OMA is capable of performing the attenuation of the periodic artefact activity without accurate information about MRI triggers. By using our proposed approach, it is possible to achieve a better balance than the slice-average subtraction as performed by the established AAS method, regarding EEG signal preservation together with effective suppression of the gradient artefact. Since the stochastic nature of the EEG signal complicates the assessment of EEG preservation after application of the gradient artefact correction, we also propose a simple and effective method to account for it.

  11. Chemical Radioprotectors

    Directory of Open Access Journals (Sweden)

    S. N. Upadhyay

    2005-10-01

    Full Text Available Protection of biological systems against radiation damage is of paramount importance during accidental and unavoidable exposure to radiation. Several physico-chemical and biological factors collectively contribute to the damage caused by radiation and are, therefore, targets for developing radioprotectors. Work on the development of chemicals capable of protecting biological systemsfrom radiation damage was initiated nearly six decades ago with cysteine being the first molecule to be reported. Chemicals capable of scavenging free radicals, inducing oxygen depletion,antioxidants and modulators of immune response have been some of the radioprotectors extensively investigated with limited success. Mechanism of action of some chemical radioprotectors and their combinations have been elucidated, while further understanding is required in many instances. The present review elaborates on structure-activity relationship of some of the chemical radioprotectors, their evaluation, and assessment, limitation, and future prospects.

  12. Spectrum of resistivity gradient driven turbulence

    International Nuclear Information System (INIS)

    The resistivity fluctuation correlation function and electrostatic potential spectrum of resistivity gradient driven turbulence are calculated analytically and compared to the results of three dimensional numerical calculations. Resistivity gradient driven turbulence is characterized by effective Reynolds' numbers of order unity. Steady-state solution of the renormalized spectrum equations yields an electrostatic potential spectrum (circumflex phi2)/sub ktheta/ approx. k/sub theta//sup -3.25/. Agreement of the analytically calculated potential spectrum and mean-square radial velocity with the results of multiple helicity numerical calculations is excellent. This comparison constitutes a quantitative test of the analytical turbulence theory used. The spectrum of magnetic fluctuations is also calculated, and agrees well with that obtained from the numerical computations. 13 refs., 8 figs

  13. Temperature gradient driven lasing and stimulated cooling

    CERN Document Server

    Sandner, K

    2012-01-01

    A laser can be understood as thermodynamic engine converting heat to a coherent single mode field close to Carnot efficiency. From this perspective spectral shaping of the excitation light generates a higher effective temperature on the pump than on the gain transition. Here, using a toy model of a quantum well structure with two suitably designed tunnel-coupled wells kept at different temperature, we study a laser operated on an actual spatial temperature gradient between pump and gain region. We predict gain and narrow band laser emission for a sufficient temperature gradient and resonator quality. Lasing appears concurrent with amplified heat flow and points to a new form of stimulated solid state cooling. Such a mechanism could raise the operating temperature limit of quantum cascade lasers by substituting phonon emission driven injection, which generates intrinsic heat, by an extended model with phonon absorption steps.

  14. Gradient evolution for potential vorticity flows

    Directory of Open Access Journals (Sweden)

    S. Balasuriya

    2001-01-01

    Full Text Available Two-dimensional unsteady incompressible flows in which the potential vorticity (PV plays a key role are examined in this study, through the development of the evolution equation for the PV gradient. For the case where the PV is conserved, precise statements concerning topology-conservation are presented. While establishing some intuitively well-known results (the numbers of eddies and saddles is conserved, other less obvious consequences (PV patches cannot be generated, some types of Lagrangian and Eulerian entities are equivalent are obtained. This approach enables an improvement on an integrability result for PV conserving flows (if there were no PV patches at time zero, the flow would be integrable. The evolution of the PV gradient is also determined for the nonconservative case, and a plausible experiment for estimating eddy diffusivity is suggested. The theory is applied to an analytical diffusive Rossby wave example.

  15. Scalable Kernel Methods via Doubly Stochastic Gradients

    OpenAIRE

    Dai, Bo; Xie, Bo; He, Niao; Liang, Yingyu; Raj, Anant; Balcan, Maria-Florina; Song, Le

    2014-01-01

    The general perception is that kernel methods are not scalable, and neural nets are the methods of choice for nonlinear learning problems. Or have we simply not tried hard enough for kernel methods? Here we propose an approach that scales up kernel methods using a novel concept called "doubly stochastic functional gradients". Our approach relies on the fact that many kernel methods can be expressed as convex optimization problems, and we solve the problems by making two unbiased stochastic ap...

  16. Implementing CAIA Delay-Gradient in Linux

    OpenAIRE

    Jonassen, Kenneth Klette

    2015-01-01

    We have implemented and evaluated an independent implementation of the CAIA Delay-Gradient congestion control in the Linux operating system. We made several adjustments or improvements to the design of CDG in our implementation. We have found sources of noise in the FreeBSD implementation of CDG. We identified areas of improvement to Linux' RTT measurements for congestion control. Our results indicate that our Linux implementation can compete effectively, and that it may operate more effectiv...

  17. Reconstructing global overturning from meridional density gradients

    Science.gov (United States)

    Butler, E. D.; Oliver, K. I. C.; Hirschi, J. J.-M.; Mecking, J. V.

    2016-04-01

    Despite the complexity of the global ocean system, numerous attempts have been made to scale the strength of the meridional overturning circulation (MOC), principally in the North Atlantic, with large-scale, basin-wide hydrographic properties. In particular, various approaches to scaling the MOC with meridional density gradients have been proposed, but the success of these has only been demonstrated under limited conditions. Here we present a scaling relationship linking overturning to twice vertically-integrated meridional density gradients via the hydrostatic equation and a "rotated" form of the geostrophic equation. This provides a meridional overturning streamfunction as a function of depth for each basin. Using a series of periodically forced experiments in a global, coarse resolution configuration of the general circulation model NEMO, we explore the timescales over which this scaling is temporally valid. We find that the scaling holds well in the upper Atlantic cell (at 1000 m) for multi-decadal (and longer) timescales, accurately reconstructing the relative magnitude of the response for different frequencies and explaining over 85 % of overturning variance on timescales of 64-2048 years. Despite the highly nonlinear response of the Antarctic cell in the abyssal Atlantic, between 76 and 94 % of the observed variability at 4000 m is reconstructed on timescales of 32 years (and longer). The scaling law is also applied in the Indo-Pacific. This analysis is extended to a higher resolution, stochastically forced simulation for which correlations of between 0.79 and 0.99 are obtained with upper Atlantic MOC variability on timescales >25 years. These results indicate that meridional density gradients and overturning are linked via meridional pressure gradients, and that both the strength and structure of the MOC can be reconstructed from hydrography on multi-decadal and longer timescales provided that the link is made in this way.

  18. SPECTROSCOPIC GRADIENTS IN EARLY-TYPE GALAXIES

    Directory of Open Access Journals (Sweden)

    A. Buzzoni

    2009-01-01

    Full Text Available We review some relevant properties of the observed changes of H , Mg2, and Fei Lick indices across the surface of 25 bright elliptical galaxies. The impact of these spectroscopic gradients is brie y discussed, in the framework of the leading physical mechanisms that led to galaxy formation. In particular, three relevant evolutionary scenarios are sketched, each one able, in principle, to consistently match galaxy spectral properties and e ectively constrain the composing stellar populations in these systems.

  19. Fluorescence correlation spectroscopy in laser gradient field

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Fluorescence correlation spectroscopy (FCS) is capable of probing dynamic processes in living biological systems. From photon fluctuation of fluorescing particles which diffuse through a small detection volume, FCS reveals information on the concentration and the structure of the particles, as well as information on microscopic environment.In this note, we study the radiation forces experienced by Rayleigh particles in a laser field in details, and analyze the effects of gradient field on FCS measurements.

  20. Fracture driven by a Thermal Gradient

    CERN Document Server

    Pla, O

    1995-01-01

    Motivated by recent experiments by Yuse and Sano (Nature, 362, 329 (1993)), we propose a discrete model of linear springs for studying fracture in thin and elastically isotropic brittle films. The method enables us to draw a map of the stresses in the material. Cracks generated by the model, imposing a moving thermal gradient in the material, can branch or wiggle depending on the driving parameters. The results may be used to compare with other recent theoretical work, or to design future experiments.

  1. Intergenerational and Socioeconomic Gradients of Child Obesity

    OpenAIRE

    Joan Costa-Fonta; Joan Gil

    2012-01-01

    Can the rise in obesity among children be attributed to intergenerationally parental influences? How important is a parent’s socioeconomic status in accounting for the emergence of obesity among children? This paper documents evidence of an emerging social gradient of obesity in pre-school children resulting from a combination of income and education effects, as well as less intensive childcare associated with maternal employment, when different forms of intergenerational transmission are con...

  2. Stress gradients in CrN coatings

    OpenAIRE

    Janssen, G.C.A.M.; Tichelaar, F.D.; Visser, C.C.G.

    2006-01-01

    Stress in hard films is the net sum of tensile stress generated at the grain boundaries, compressive stress due to ion peening, and thermal stress due to the difference in thermal expansion of the coating and substrate. The tensile part due to grain boundaries is thickness dependent. The other two contributions are not thickness dependent. Summation of the three components leads to a stress gradient in the coating. In the present paper it is demonstrated that adding the three contributions me...

  3. Quantized Concentration Gradient in Picoliter Scale

    Science.gov (United States)

    Hong, Jong Wook

    2010-10-01

    Generation of concentration gradient is of paramount importance in the success of reactions for cell biology, molecular biology, biochemistry, drug-discovery, chemotaxis, cell culture, biomaterials synthesis, and tissue engineering. In conventional method of conducting reactions, the concentration gradients is achieved by using pipettes, test tubes, 96-well assay plates, and robotic systems. Conventional methods require milliliter or microliter volumes of samples for typical experiments with multiple and sequential reactions. It is a challenge to carry out experiments with precious samples that have strict limitations with the amount of samples or the price to pay for the amount. In order to overcome this challenge faced by the conventional methods, fluidic devices with micrometer scale channels have been developed. These devices, however, cause restrictions on changing the concentration due to the fixed gradient set based on fixed fluidic channels.ootnotetextJambovane, S.; Duin, E. C.; Kim, S-K.; Hong, J. W., Determination of Kinetic Parameters, KM and kcat, with a Single Experiment on a Chip. textitAnalytical Chemistry, 81, (9), 3239-3245, 2009.^,ootnotetextJambovane, S.; Hong, J. W., Lorenz-like Chatotic System on a Chip In The 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences (MicroTAS), The Netherlands, October, 2010. Here, we present a unique microfluidic system that can generate quantized concentration gradient by using series of droplets generated by a mechanical valve based injection method.ootnotetextJambovane, S.; Rho, H.; Hong, J., Fluidic Circuit based Predictive Model of Microdroplet Generation through Mechanical Cutting. In ASME International Mechanical Engineering Congress & Exposition, Lake Buena Vista, Florida, USA, October, 2009.^,ootnotetextLee, W.; Jambovane, S.; Kim, D.; Hong, J., Predictive Model on Micro Droplet Generation through Mechanical Cutting. Microfluidics and Nanofluidics, 7, (3), 431-438, 2009

  4. Exponentiated Gradient Exploration for Active Learning

    OpenAIRE

    Djallel Bouneffouf

    2016-01-01

    Active learning strategies respond to the costly labeling task in a supervised classification by selecting the most useful unlabeled examples in training a predictive model. Many conventional active learning algorithms focus on refining the decision boundary, rather than exploring new regions that can be more informative. In this setting, we propose a sequential algorithm named exponentiated gradient (EG)-active that can improve any active learning algorithm by an optimal random exploration. ...

  5. Fixed-Field Alternating-Gradient Accelerators

    OpenAIRE

    Sheehy, S. L.

    2016-01-01

    These notes provide an overview of Fixed-Field Alternating-Gradient (FFAG) accelerators for medical applications. We begin with a review of the basic principles of this type of accelerator, including the scaling and non-scaling types, highlighting beam dynamics issues that are of relevance to hadron ac- celerators. The potential of FFAG accelerators in the field of hadron therapy is discussed in detail, including an overview of existing medical FFAG designs. The options for FFAG treatment gan...

  6. Optimization of ceramic strength using elastic gradients

    OpenAIRE

    Zhang, Yu; Ma, Li

    2009-01-01

    We present a new concept for strengthening ceamics by utilizing a graded structure with a low elastic modulus at both top and bottom surfaces sandwiching a high-modulus interior. Closed-form equations have been developed for stress analysis of simply supported graded sandwich beams subject to transverse center loads. Theory predicts that suitable modulus gradients at the ceramic surface can effectively reduce and spread the maximum bending stress from the surface into the interior. The magnit...

  7. Gradient Domain Mesh Deformation - A Survey

    Institute of Scientific and Technical Information of China (English)

    Wei-Wei Xu; Kun Zhou

    2009-01-01

    This survey reviews the recent development of gradient domain mesh deformation method. Different to other deformation methods, the gradient domain deformation method is a surface-based, variational optimization method. It directly encodes the geometric details in differential coordinates, which are also called Laplacian coordinates in literature. By preserving the Laplacian coordinates, the mesh details can be well preserved during deformation. Due to the locality of the Laplacian coordinates, the variational optimization problem can be casted into a sparse linear system. Fast sparse linear solver can be adopted to generate deformation result interactively, or even in real-time. The nonlinear nature of gradient domain mesh deformation leads to the development of two categories of deformation methods: linearization methods and nonlinear optimization methods. Basically, the linearization methods only need to solve the linear least-squares system once. They are fast, easy to understand and control, while the deformation result might be suboptimal. Nonlinear optimization methods can reach optimal solution of deformation energy function by iterative updating. Since the computation of nonlinear methods is expensive, reduced deformable models should be adopted to achieve interactive performance. The nonlinear optimization methods avoid the user burden to input transformation at deformation handles, and they can be extended to incorporate various nonlinear constraints, like volume constraint, skeleton constraint, and so on. We review representative methods and related approaches of each category comparatively and hope to help the user understand the motivation behind the algorithms. Finally, we discuss the relation between physical simulation and gradient domain mesh deformation to reveal why it can achieve physically plausible deformation result.

  8. Fixed-Field Alternating-Gradient Accelerators

    CERN Document Server

    Sheehy, S L

    2016-01-01

    These notes provide an overview of Fixed-Field Alternating-Gradient (FFAG) accelerators for medical applications. We begin with a review of the basic principles of this type of accelerator, including the scaling and non-scaling types, highlighting beam dynamics issues that are of relevance to hadron ac- celerators. The potential of FFAG accelerators in the field of hadron therapy is discussed in detail, including an overview of existing medical FFAG designs. The options for FFAG treatment gantries are also considered.

  9. CERN/KEK: Very high accelerating gradients

    International Nuclear Information System (INIS)

    Full text: A world-wide effort is under way to develop linear electron-positron colliders so that physics experiments can be extended into a range of energies where circular machines (necessarily much larger than CERN's 27-kilometre LEP machine) would be crippled by synchrotron radiation. CERN is studying the feasibility of building a 2 TeV machine called CLIC powered not by individual klystrons, but by a high intensity electron 'drive' linac running parallel to the main linac (November 1990, page 7). This drive linac will itself be powered by similar superconducting cavities to those developed for LEP. A high gradient is an obvious design aim for any future high energy linear collider because it makes it shorter and therefore cheaper - the design figure for the CLIC machine is 80 MV/m. The CLIC study group has taken a significant step forward in demonstrating the technical feasibility of their machine by achieving peak and average accelerating gradients of 137 MV/m and 84 MV/m respectively in a short section of accelerating structure during high gradient tests at the Japanese KEK Laboratory last year. This result obtained within the framework of a CERN/KEK collaboration on linear colliders was obtained using a 20-cell accelerating section built at CERN using state-of the- art technology which served both as a model for CLIC studies as well as a prototype for the Japanese Linear Collider studies. The operating frequency of the model accelerating section is 2.6 times lower than the CLIC frequency but was chosen because a high power r.f. source and pulse compression scheme has been developed for this frequency at KEK. Testing CLIC models at 11.4 GHz is however more stringent than at 30 GHz because the chance of electrical breakdown increases as the frequency is lowered. This recent result clearly demonstrates that a gradient of 80 MV/m is feasible

  10. Gradient Method Optimization of Penicillin Production

    Czech Academy of Sciences Publication Activity Database

    Pčolka, M.; Čelikovský, Sergej

    Vol. IEEE Catalog Number: CFP1251D-CDR. Taiyuan: IEEE, 2012, s. 74-79. ISBN 978-1-4577-2072-7. [The 24th Chinese Control and Decision Conference (2012 CCDC). Taiyuan (CN), 23.05.2012-25.05.2012] R&D Projects: GA ČR(CZ) GAP103/12/1794 Institutional support: RVO:67985556 Keywords : fermentation process * penicillin * gradient method * optimization Subject RIV: BC - Control Systems Theory www.ccdc.neu.edu.cn

  11. Intergenerational and socioeconomic gradients of childhood obesity

    OpenAIRE

    Costa-i-Font, Joan; Gil, Joan

    2013-01-01

    Can the rise in obesity among children be attributed to intergenerationally parental influences? How important is a parent’s socioeconomic status in accounting for the emergence of obesity among children? This paper documents evidence of an emerging social gradient of obesity in pre-school children resulting from a combination of income and education effects, as well as less intensive childcare associated with maternal employment, when different forms of intergenerational transmission are con...

  12. Typical MR intensity distribution patterns in different knee joint diseases using a gradient echo sequence

    International Nuclear Information System (INIS)

    The knee joints of 31 patients and 3 volunteers were examined with a 1.5 T Magnetom using 3D-gradient echo sequences. We measured for the most widespread diseases: The gonarthrosis (n=23) and rheumatoid arthritis (n=8) the signal intensities in all joint parts and the typical signal plots were worked out. In case of minimal changes at the articular cartilage, the method developed and tried out by us can facilitate diagnosis. A special aspect of this method is also the patient follow-up which is now possible quantitatively and objectively. (orig.)

  13. Pedestrian Detection Using Gradient Local Binary Patterns

    Science.gov (United States)

    Jiang, Ning; Xu, Jiu; Goto, Satoshi

    In recent years, local pattern based features have attracted increasing interest in object detection and recognition systems. Local Binary Pattern (LBP) feature is widely used in texture classification and face detection. But the original definition of LBP is not suitable for human detection. In this paper, we propose a novel feature named gradient local binary patterns (GLBP) for human detection. In this feature, original 256 local binary patterns are reduced to 56 patterns. These 56 patterns named uniform patterns are used for generating a 56-bin histogram. And gradient value of each pixel is set as the weight which is always same in LBP based features in histogram calculation to computing the values in 56 bins for histogram. Experiments are performed on INRIA dataset, which shows the proposal GLBP feature is discriminative than histogram of orientated gradient (HOG), Semantic Local Binary Patterns (S-LBP) and histogram of template (HOT). In our experiments, the window size is fixed. That means the performance can be improved by boosting methods. And the computation of GLBP feature is parallel, which make it easy for hardware acceleration. These factors make GLBP feature possible for real-time pedestrian detection.

  14. Fast algorithm for integrating inconsistent gradient fields

    Science.gov (United States)

    Rivera, Mariano; Marroquin, Jose L.; Servin, Manuel; Rodriguez-Vera, Ramon

    1997-11-01

    A discrete Fourier transform (DFT) based algorithm for solving a quadratic cost functional is proposed; this regularized functional allows one to obtain a consistent gradient field from an inconsistent one. The calculated consistent gradient may then be integrated by use of simple methods. The technique is presented in the context of the phase-unwrapping problem; however, it may be applied to other problems, such as shapes from shading (a robot-vision technique) when inconsistent gradient fields with irregular domains are obtained. The regularized functional introduced here has advantages over existing techniques; in particular, it is able to manage complex irregular domains and to interpolate over regions with invalid data without any smoothness assumptions over the rest of the lattice, so that the estimation error is reduced. Furthermore, there are no free parameters to adjust. The DFT is used to compute a preconditioner because there is highly efficient hardware to perform the calculations and also because it may be computed by optical means.

  15. Sparse and Robust Signal Reconstruction

    Directory of Open Access Journals (Sweden)

    Sandra V. B. Jardim

    2015-04-01

    Full Text Available Many problems in signal processing and statistical inference are based on finding a sparse solution to an undetermined linearsystem. The reference approach to this problem of finding sparse signal representations, onovercomplete dictionaries, leads to convex unconstrained optimization problems, with a quadratic term $\\ell_{2}$, for the adjustment to the observed signal, and a coefficient vector $\\ell_{1}$-norm. This work focus the development and experimental analysis of an algorithm for the solution of $\\ell_{q}$-$\\ell_{p}$ optimization problems, where $p \\in \\, ]0, \\, 1] \\, \\wedge \\, q \\in \\, [1, \\, 2]$, of which $\\ell_{2}$-$\\ell_{1}$ is an instance. The developed algorithm belongs to the majorization-minimization class, where the solution of the problem is given by the minimization of a progression of majorizers of the original function. Each iteration corresponds to the solution of an $\\ell_{2}$-$\\ell_{1}$ problem, solved by the projected gradient algorithm. When tested on synthetic data and image reconstruction problems, the results shows a good performance of the implemented algorithm, both in compressed sensing and signal restoration scenarios.

  16. Transient Chemical Denudation Rates in Soils and Saprolites: Responses to Channel Incision in Sierra Nevada, California

    Science.gov (United States)

    Weinman, B. A.; Yoo, K.; Mudd, S. M.; Hurst, M. D.; Maher, K.

    2012-12-01

    Here we explore soil and saprolite weathering along a denudation gradient (~40-400 mm kyr-1) in the Feather River catchment of northwestern California. By comparing the geochemical differences in soils and saprolites along three hillslopes--located above, at, and below a knickpoint--we can discern the impact of a propagating incision signal on the geochemical evolution of the catchment's saprolites and soil. Specifically, we couple mass balance geochemistry with soil and saprolite turnover times to determine rates of chemical weathering of soils and saprolites at the hillslope scale. Soil turnover time was determined by dividing the average soil thickness (L) with the rate of denudation (LT-1). For the catchment scale, we used 10Be-based denudation rates (Riebe et al., 2001; Hurst et al., 2012). For hilltops where accelerated channel incision signal has not yet reached, LiDAR-based hilltop curvature is used for calculating total denudation rates (Hurst et al., 2012). Lastly, for the steepest hillslope base adjacent to channels, we used a nonlinear slope-dependent sediment transport law to estimate denudation (Roering et al., 2007). Turnover times, soil bulk density, and elemental chemistry were then used to estimate the rates of chemical weathering (ML-2T-1) experienced in the soils and saprolites. Our results indicate that, for transient landscapes, both hilltop curvature and the bottom-most slope should be used to capture a range of chemical denudation occurring along adjusting hillslopes. This is because soils and saprolites are undergoing variable rates of physical and chemical denudation along a single hillform: total chemical denudation (of both soils and saprolites) tends to be ~4x's larger at the bottommost part of the hillslope, nearest to the channel. Along the denudation gradient, soils along steeper hillslopes are chemically denuding faster than more gently sloped hillslopes, at rates of ~50 vs. 10t/km2/yr, respectively. Overall, our analysis suggests

  17. A Modular Gradient-Sensing Network for Chemotaxis in Escherichia coli Revealed by Responses to Time-Varying Stimuli

    OpenAIRE

    Shimizu, Thomas S.; Tu, Yuhai; Berg, Howard

    2010-01-01

    In searching for better environments, bacteria sample their surroundings by random motility, and make temporal comparisons of experienced sensory cues to bias their movement toward favorable directions (Berg and Brown, 1972). Thus, the problem of sensing spatial gradients is reduced to time-derivative computations, carried out by a signaling pathway that is well characterized at the molecular level in Escherichia coli. Here, we study the physiology of this signal processing system in vivo by ...

  18. The effect of deposition parameters on the properties of gradient a-C:H/Ti layers

    OpenAIRE

    D. Batory; A. Stanishevsky; W. Kaczorowski

    2009-01-01

    Purpose: During the last 20 years DLC (diamond-like carbon) layers became a very attractive material in many medical and engineering applications. While the layer’s stress and adhesion were always a concern, several adhesion improvement methods have been proposed. A majority of those methods consists of either the deposition of an adhesion promoting interlayer or the application of a gradient of chemical composition. In whatever way this reduces the internal stress and improves the adhesion o...

  19. Constant pressure gradient separation with our simple automated nano-LC platform

    Czech Academy of Sciences Publication Activity Database

    Šesták, Jozef; Kahle, Vladislav

    The Royal Flemish Chemical Society (KVCV), 2014. s. 143. [International Symposium on Hyphenated Techniques in Chromatography and eparation Technology (HTC-13) /13./ and International Symposium on Hyphenated Techniques for Sample Preparation (HTSP-3) /3./. 28.01.2014-31.01.2014, Bruges] R&D Projects: GA MV VG20112015021; GA MV VG20102015023 Institutional support: RVO:68081715 Keywords : constant pressure * liquid chromatography * gradient elution Subject RIV: CB - Analytical Chemistry, Separation

  20. Microsphere-Based Scaffolds Carrying Opposing Gradients of Chondroitin Sulfate and Tricalcium Phosphate

    OpenAIRE

    Gupta, Vineet; Mohan, Neethu; Berkland, Cory J.; Detamore, Michael S.

    2015-01-01

    Extracellular matrix (ECM) components, such as chondroitin sulfate (CS) and tricalcium phosphate, serve as raw materials, and thus spatial patterning of these raw materials may be leveraged to mimic the smooth transition of physical, chemical, and mechanical properties at the bone-cartilage interface. We hypothesized that encapsulation of opposing gradients of these raw materials in high molecular weight poly(d,l-lactic-co-glycolic acid) (PLGA) microsphere-based scaffolds would enhance differ...