Science.gov

Sample records for mesoscopic biological test

  1. Cosmic heavy ion tracks in mesoscopic biological test objects

    NASA Technical Reports Server (NTRS)

    Facius, R.

    1994-01-01

    Since more than 20 years ago, when the National Academy of Sciences and the National Research Council of the U.S.A. released their report on 'HZE particle effects in manned spaced flight', it has been emphasized how difficult - if not even impossible - it is to assess their radiobiological impact on man from conventional studies where biological test organisms are stochastically exposed to 'large' fluences of heavy ions. An alternative, competing approach had been realized in the BIOSTACK experiments, where the effects of single cosmic as well as accelerator - heavy ions on individual biological test organisms could be investigated. Although presented from the beginning as the preferable approach for terrestrial investigations with accelerator heavy ions too ('The BIOSTACK as an approach to high LET radiation research'), only recently this insight is gaining more widespread recognition. In space flight experiments, additional constraints imposed by the infrastructure of the vehicle or satellite further impede such investigations. Restrictions concern the physical detector systems needed for the registration of the cosmic heavy ions' trajectories as well as the biological systems eligible as test organisms. Such optimized procedures and techniques were developed for the investigations on chromosome aberrations induced by cosmic heavy ions in cells of the stem meristem of lettuce seeds (Lactuca sativa) and for the investigation of the radiobiological response of Wolffia arriza, which is the smallest flowering (water) plant. The biological effects were studied by the coworkers of the Russian Institute of Biomedical Problems (IBMP) which in cooperation with the European Space Agency ESA organized the exposure in the Biosatellites of the Cosmos series. Since biological investigations and physical measurements of particle tracks had to be performed in laboratories widely separated, the preferred fixed contact between biological test objects and the particle detectors

  2. Cosmic heavy ion tracks in mesoscopic biological test objects

    SciTech Connect

    Facius, R.

    1994-12-31

    Since more than 20 years ago, when the National Academy of Sciences and the National Research Council of the U.S.A. released their report on `HZE particle effects in manned spaced flight`, it has been emphasized how difficult - if not even impossible - it is to assess their radiobiological impact on man from conventional studies where biological test organisms are stochastically exposed to `large` fluences of heavy ions. An alternative, competing approach had been realized in the BIOSTACK experiments, where the effects of single cosmic as well as accelerator - heavy ions on individual biological test organisms could be investigated. Although presented from the beginning as the preferable approach for terrestrial investigations with accelerator heavy ions too (`The BIOSTACK as an approach to high LET radiation research`), only recently this insight is gaining more widespread recognition. In space flight experiments, additional constraints imposed by the infrastructure of the vehicle or satellite further impede such investigations. Restrictions concern the physical detector systems needed for the registration of the cosmic heavy ions` trajectories as well as the biological systems eligible as test organisms. Such optimized procedures and techniques were developed for the investigations on chromosome aberrations induced by cosmic heavy ions in cells of the stem meristem of lettuce seeds (Lactuca sativa) and for the investigation of the radiobiological response of Wolffia arriza, which is the smallest flowering (water) plant. The biological effects were studied by the coworkers of the Russian Institute of Biomedical Problems (IBMP) which in cooperation with the European Space Agency ESA organized the exposure in the Biosatellites of the Cosmos series.

  3. Fundamental and functional aspects of mesoscopic architectures with examples in physics, cell biology, and chemistry.

    PubMed

    Kalay, Ziya

    2011-08-01

    How small can a macroscopic object be made without losing its intended function? Obviously, the smallest possible size is determined by the size of an atom, but it is not so obvious how many atoms are required to assemble an object so small, and yet that performs the same function as its macroscopic counterpart. In this review, we are concerned with objects of intermediate nature, lying between the microscopic and the macroscopic world. In physics and chemistry literature, this regime in-between is often called mesoscopic, and is known to bear interesting and counterintuitive features. After a brief introduction to the concept of mesoscopic systems from the perspective of physics, we discuss the functional aspects of mesoscopic architectures in cell biology, and supramolecular chemistry through many examples from the literature. We argue that the biochemistry of the cell is largely regulated by mesoscopic functional architectures; however, the significance of mesoscopic phenomena seems to be quite underappreciated in biological sciences. With this motivation, one of our main purposes here is to emphasize the critical role that mesoscopic structures play in cell biology and biochemistry.

  4. Reconstruction of fluorescence distribution hidden in biological tissue using mesoscopic epifluorescence tomography

    NASA Astrophysics Data System (ADS)

    Björn, Saskia; Englmeier, Karl-Hans; Ntziachristos, Vasilis; Schulz, Ralf

    2011-04-01

    Mesoscopic epifluorescence tomography is a novel technique that discovers fluorescence bio-distribution in small animals by tomographic means in reflectance geometry. A collimated laser beam is scanned over the skin surface to excite fluorophores hidden within the tissue while a CCD camera acquires an image of the fluorescence emission for each source position. This configuration is highly efficient in the visible spectrum range where trans-illumination imaging of small animals is not feasible due to the high tissue absorption and scattering in biological organisms. The reconstruction algorithm is similar to the one used in fluorescence molecular tomography. However, diffusion theory cannot be employed since the source-detector separation for most image pixels is comparable to or below the scattering length of the tissue. Instead Monte Carlo simulations are utilized to predict the sensitivity functions. In a phantom study we show the effect of using enhanced source grid arrangements during the data acquisition and the reconstruction process to minimize boundary artefacts. Furthermore, we present ex vivo data that show high spatial resolution and quantitative accuracy in heterogeneous tissues using GFP-like fluorescence in B6-albino mice up to a depth of 1100 μm.

  5. Crucial tests of macrorealist and semiclassical gravity models with freely falling mesoscopic nanospheres

    NASA Astrophysics Data System (ADS)

    Colin, Samuel; Durt, Thomas; Willox, Ralph

    2016-06-01

    Recently, several proposals have been made to test the quantum superposition principle in the mesoscopic regime. Most of these tests consist of a careful measurement of the loss of interference due to decoherence. Here we consider, instead, the spread in position of a freely falling nanosphere. We study in depth the dependence of this spread on self-gravity in the presence of decoherence (exotic and nonexotic). We show that the influence of self-gravity is robust in the presence of weak decoherence, and quantify this robustness by introducing a parameter, the critical decoherence, aimed at estimating the critical value above which self-gravity is overwhelmed by decoherence. We also emphasize the crucial role played by the spread of the initial wave packet for the sensitivity of free-fall experiments to decoherence.

  6. cellPACK: A Virtual Mesoscope to Model and Visualize Structural Systems Biology

    PubMed Central

    Johnson, Graham T.; Autin, Ludovic; Al-Alusi, Mostafa; Goodsell, David S.; Sanner, Michel F.; Olson, Arthur J.

    2014-01-01

    cellPACK assembles computational models of the biological mesoscale, an intermediate scale (10−7–10−8m) between molecular and cellular biology. cellPACK’s modular architecture unites existing and novel packing algorithms to generate, visualize and analyze comprehensive 3D models of complex biological environments that integrate data from multiple experimental systems biology and structural biology sources. cellPACK is currently available as open source code, with tools for validation of models and with recipes and models for five biological systems: blood plasma, cytoplasm, synaptic vesicles, HIV and a mycoplasma cell. We have applied cellPACK to model distributions of HIV envelope protein to test several hypotheses for consistency with experimental observations. Biologists, educators, and outreach specialists can interact with cellPACK models, develop new recipes and perform packing experiments through scripting and graphical user interfaces at http://cellPACK.org. PMID:25437435

  7. Mesoscopic Lawlessness

    NASA Astrophysics Data System (ADS)

    Laughlin, R. B.

    2012-02-01

    Whether physics will contribute significantly to unraveling the secrets of life, the grandest challenge of them all, depends critically on whether proteins and other mesoscale objects exhibit emergent law. By this I mean quantitative relationships among their measured properties that are always true. The jury is still out on the matter, for there is evidence both for and against, but it is spotty, on account of the difficulty of measuring 100 nm - 1000 objects without damaging them quantum mechanically. It is therefore not clear that history will repeat itself. Physics contributed mightily to 20th century materials science through its identification and mastery of powerful macroscopic emergent laws such as crystalline rigidity, superconductivity and ferromagnetism, but it cannot do the same thing in biology, regardless of how powerful computers get, unless nature cooperates. The challenge before us as physicists is therefore not to amass more and more terabytes of data and computational output but rather to search for and, with luck, find operating principles at the scale of life greater than those of chemistry, which is to say, greater than a world ruled by nothing but miraculous accidents.

  8. Simultaneous measurement of the microscopic dynamics and the mesoscopic displacement field in soft systems by speckle imaging.

    PubMed

    Cipelletti, L; Brambilla, G; Maccarrone, S; Caroff, S

    2013-09-23

    The constituents of soft matter systems such as colloidal suspensions, emulsions, polymers, and biological tissues undergo microscopic random motion, due to thermal energy. They may also experience drift motion correlated over mesoscopic or macroscopic length scales, e.g. in response to an internal or applied stress or during flow. We present a new method for measuring simultaneously both the microscopic motion and the mesoscopic or macroscopic drift. The method is based on the analysis of spatio-temporal cross-correlation functions of speckle patterns taken in an imaging configuration. The method is tested on a translating Brownian suspension and a sheared colloidal glass.

  9. Electron waiting times for the mesoscopic capacitor

    NASA Astrophysics Data System (ADS)

    Hofer, Patrick P.; Dasenbrook, David; Flindt, Christian

    2016-08-01

    We evaluate the distribution of waiting times between electrons emitted by a driven mesoscopic capacitor. Based on a wave packet approach we obtain analytic expressions for the electronic waiting time distribution and the joint distribution of subsequent waiting times. These semi-classical results are compared to a full quantum treatment based on Floquet scattering theory and good agreement is found in the appropriate parameter ranges. Our results provide an intuitive picture of the electronic emissions from the driven mesoscopic capacitor and may be tested in future experiments.

  10. - and Perovskite-Sensitised Mesoscopic Solar Cells

    NASA Astrophysics Data System (ADS)

    Grätzel, Michael; Durrant, James R.

    2015-10-01

    The following sections are included: * Introduction * Historical background * Mode of function of dye-sensitised solar cells * DSSC research and development * Solid-state mesoscopic cells based on molecular dyes or perovskite pigments as sensitisers * Pilot production of modules, field tests and commercial DSSC development * Outlook * Acknowledgements * References

  11. Entanglement of mesoscopic systems

    NASA Astrophysics Data System (ADS)

    Narnhofer, Heide; Thirring, Walter

    2002-11-01

    The entanglement of clouds of N=1011 atoms recently experimentally verified is expressed in terms of the fluctuation algebra introduced by [P. Goderis, A. Verbeure, and P. Vets, Commun. Phys. 128, 533 (1990)]. A mean-field Hamiltonian describing the coupling to a laser beam leads to different time evolutions if considered on microscopic or mesoscopic operators. Only the latter creates nontrivial correlations that finally after a measurement lead to entanglement between the clouds.

  12. Apparatus for automated testing of biological specimens

    DOEpatents

    Layne, Scott P.; Beugelsdijk, Tony J.

    1999-01-01

    An apparatus for performing automated testing of infections biological specimens is disclosed. The apparatus comprise a process controller for translating user commands into test instrument suite commands, and a test instrument suite comprising a means to treat the specimen to manifest an observable result, and a detector for measuring the observable result to generate specimen test results.

  13. Mesoscopic Interferometers for Electron Waves

    SciTech Connect

    Rohrlich, D.

    2005-09-15

    Mesoscopic interferometers are electronic analogues of optical interferometers, with 'quantum point contacts' playing the role of optical beam splitters. Mesoscopic analogues of two-slit, Mach-Zehnder and Fabry-Perot interferometers have been built. A fundamental difference between electron and photon interferometry is that electron interferometry is nonlocal.

  14. Biomonitoring test procedures and biological criteria

    SciTech Connect

    Kszos, L.A.; Lipschultz, M.J.; Foster, W.E.

    1997-10-01

    The Water Environment Federation recently issued a special publication, Biomonitoring in the Water Environment. In this paper, the authors highlight the contents of the chapter 3, Biomonitoring Test Procedures, identify current trends in test procedures and introduce the concept of biological criteria (biocriteria). The book chapter (and this paper) focuses on freshwater and marine chronic and acute toxicity tests used in the National Pollutant Discharge Elimination System (NPDES) permits program to identify effluents and receiving waters containing toxic materials in acutely or chronically toxic concentrations. The two major categories of toxicity tests include acute tests and chronic tests. The USEPA chronic tests required in NPDEs permits have been shortened to 7 days by focusing on the most sensitive life-cycle stages; these tests are often referred to as short-term chronic tests. The type of test(s) required depend on NPDES permit requirements, objectives of the test, available resources, requirements of the test organisms, and effluent characteristics such as variability in flow or toxicity. The permit writer will determine the requirements for toxicity test(s) by considering such factors as dilution, effluent variability, and exposure variability. Whether the required test is acute or chronic, the objective of the test is to estimate the safe or no effect concentration which is defined as the concentration which will permit normal propagation of fish and other aquatic life in the receiving waters. In this paper, the authors review the types of toxicity tests, the commonly used test organisms, and the uses of toxicity test data. In addition, they briefly describe research on new methods and the use of biological criteria.

  15. Seismoelectric effects due to mesoscopic heterogeneities

    NASA Astrophysics Data System (ADS)

    Jougnot, Damien; Rubino, J. GermáN.; Carbajal, Marina Rosas; Linde, Niklas; Holliger, Klaus

    2013-05-01

    While the seismic effects of wave-induced fluid flow due to mesoscopic heterogeneities have been studied for several decades, the role played by these types of heterogeneities on seismoelectric phenomena is largely unexplored. To address this issue, we have developed a novel methodological framework which allows for the coupling of wave-induced fluid flow, as inferred through numerical oscillatory compressibility tests, with the pertinent seismoelectric conversion mechanisms. Simulating the corresponding response of a water-saturated sandstone sample containing mesoscopic fractures, we demonstrate for the first time that these kinds of heterogeneities can produce measurable seismoelectric signals under typical laboratory conditions. Given that this phenomenon is sensitive to key hydraulic and mechanical properties, we expect that the results of this pilot study will stimulate further exploration on this topic in several domains of the Earth, environmental, and engineering sciences.

  16. [Biological tests of sol-gel biomaterials].

    PubMed

    Ulatowska-Jarza, A; Podbielska, H; Szymonowicz, M; Staniszewska-Kuś, J; Paluch, D

    2000-01-01

    Recently, the sol-gel based biomaterials are extendedly investigated in emphasis on theirs medical applications. In this respect it is important to investigate the influence of sol-gel matrices on biological systems. The results of laboratory and biological testing of water extracts of sol-gels are presented in this work. It was proved that it is possible to construct the sol-gels that are not cytotoxic for which the haemolytic reactions fulfils the foreseen norms. This can be achieved by heating the materials in certain temperatures (higher than 350 degrees C). This effect can also be reached by suitably long aging (minimum 6 months).

  17. Unit testing, model validation, and biological simulation.

    PubMed

    Sarma, Gopal P; Jacobs, Travis W; Watts, Mark D; Ghayoomie, S Vahid; Larson, Stephen D; Gerkin, Richard C

    2016-01-01

    The growth of the software industry has gone hand in hand with the development of tools and cultural practices for ensuring the reliability of complex pieces of software. These tools and practices are now acknowledged to be essential to the management of modern software. As computational models and methods have become increasingly common in the biological sciences, it is important to examine how these practices can accelerate biological software development and improve research quality. In this article, we give a focused case study of our experience with the practices of unit testing and test-driven development in OpenWorm, an open-science project aimed at modeling Caenorhabditis elegans. We identify and discuss the challenges of incorporating test-driven development into a heterogeneous, data-driven project, as well as the role of model validation tests, a category of tests unique to software which expresses scientific models. PMID:27635225

  18. Unit testing, model validation, and biological simulation

    PubMed Central

    Watts, Mark D.; Ghayoomie, S. Vahid; Larson, Stephen D.; Gerkin, Richard C.

    2016-01-01

    The growth of the software industry has gone hand in hand with the development of tools and cultural practices for ensuring the reliability of complex pieces of software. These tools and practices are now acknowledged to be essential to the management of modern software. As computational models and methods have become increasingly common in the biological sciences, it is important to examine how these practices can accelerate biological software development and improve research quality. In this article, we give a focused case study of our experience with the practices of unit testing and test-driven development in OpenWorm, an open-science project aimed at modeling Caenorhabditis elegans. We identify and discuss the challenges of incorporating test-driven development into a heterogeneous, data-driven project, as well as the role of model validation tests, a category of tests unique to software which expresses scientific models. PMID:27635225

  19. Unit testing, model validation, and biological simulation

    PubMed Central

    Watts, Mark D.; Ghayoomie, S. Vahid; Larson, Stephen D.; Gerkin, Richard C.

    2016-01-01

    The growth of the software industry has gone hand in hand with the development of tools and cultural practices for ensuring the reliability of complex pieces of software. These tools and practices are now acknowledged to be essential to the management of modern software. As computational models and methods have become increasingly common in the biological sciences, it is important to examine how these practices can accelerate biological software development and improve research quality. In this article, we give a focused case study of our experience with the practices of unit testing and test-driven development in OpenWorm, an open-science project aimed at modeling Caenorhabditis elegans. We identify and discuss the challenges of incorporating test-driven development into a heterogeneous, data-driven project, as well as the role of model validation tests, a category of tests unique to software which expresses scientific models.

  20. Mesoscopic simulations of recrystallization

    SciTech Connect

    Holm, E.A.; Rollett, A.D.; Srolovitz, D.J.

    1995-08-01

    The application of computer simulation to grain growth and recrystallization was strongly stimulated in the early 80s by the realization that Monte Carlo models could be applied to problems of grain structure evolution. By extension of the Ising model for domain modeling of magnetic domains to the Potts model (with generalized spin numbers) it was then possible to represent discretely grains (domains) by regions of similarly oriented sets of material (lattice) points. In parallel with this fascinating development, there also occured notable work on analytical models, especially by Abbruzzese and Bunge, which has been particularly useful for understanding the variation of texture (crystallographic preferred orientation) during grain growth processes. Geometric models of recrystallization, worked on most recently and productively by Nes et al., have been useful in connection with grain size prediction as a result of recrystallization. Also, mesh-based models have been developed to a high degree by Kawasaki, Fradkov and others, and, rather recently, by Humphreys to model not just grain growth but also the nucleation process in recrystallization. These models have the strength that they deal with the essential features of grains, i.e. the nodes, but have some limitations when second phases must be considered. These various approaches to modeling of recrystallization processes will be reviewed, with a special emphasis on practical approaches to implementing the Potts model. This model has been remarkably successful in modeling such diverse phenomena as dynamic recrystallization, secondary recrystallization (abnormal grain growth), particle-inhibited recrystallization, and grain structure evolution in soldering and welding. In summary, the application of mesoscopic simulation to the phenomenon of recrystallization has yielded much new insight into some longstanding deficiencies in our understanding.

  1. The developmental toxicity testing of biologics.

    PubMed

    Hazelden, Keith P

    2013-01-01

    The characteristics of biologic drugs, as compared with small molecules, confer significant advantages for both the drug developer and the prospective patients. The necessity for, and the timing of, developmental toxicity testing in the preclinical program must be considered. Choice of an appropriate test system is of particular importance, one that shows pharmacodynamic activity comparable to man. Where the conventional rodent/non-rodent species show such functional cross-reactivity, those species can be used in developmental testing, but often the only relevant species will be a nonhuman primate, in which case an extended study design (the ePPND) should be the default. Such an approach provides appropriate toxicity screening while reducing animal usage.

  2. What can we learn from noise? - Mesoscopic nonequilibrium statistical physics.

    PubMed

    Kobayashi, Kensuke

    2016-01-01

    Mesoscopic systems - small electric circuits working in quantum regime - offer us a unique experimental stage to explorer quantum transport in a tunable and precise way. The purpose of this Review is to show how they can contribute to statistical physics. We introduce the significance of fluctuation, or equivalently noise, as noise measurement enables us to address the fundamental aspects of a physical system. The significance of the fluctuation theorem (FT) in statistical physics is noted. We explain what information can be deduced from the current noise measurement in mesoscopic systems. As an important application of the noise measurement to statistical physics, we describe our experimental work on the current and current noise in an electron interferometer, which is the first experimental test of FT in quantum regime. Our attempt will shed new light in the research field of mesoscopic quantum statistical physics. PMID:27477456

  3. Reaction rates for mesoscopic reaction-diffusion kinetics

    PubMed Central

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2016-01-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results. PMID:25768640

  4. Reaction rates for mesoscopic reaction-diffusion kinetics

    NASA Astrophysics Data System (ADS)

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  5. Reaction rates for mesoscopic reaction-diffusion kinetics.

    PubMed

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  6. Spontaneous currents in mesoscopic rings

    SciTech Connect

    Wohleben, D.; Freche, P.; Esser, M. ); Zipper, E.; Szopa, M. )

    1992-10-20

    In this paper, in a system of mesoscopic rings, the influence of orbital magnetic interaction between the electrons is investigated. At a critical temperature T[sub c] the system undergoes a phase transition into a current carrying state. T[sub c] depends strongly on geometry of the system and/or its Fermi-surface, and on the quantum size gap at the Fermi level. Elastic scattering reduces T[sub c] and eventually suppresses the transition.

  7. Mesoscopic Superposition States in Relativistic Landau Levels

    SciTech Connect

    Bermudez, A.; Martin-Delgado, M. A.; Solano, E.

    2007-09-21

    We show that a linear superposition of mesoscopic states in relativistic Landau levels can be built when an external magnetic field couples to a relativistic spin 1/2 charged particle. Under suitable initial conditions, the associated Dirac equation produces unitarily superpositions of coherent states involving the particle orbital quanta in a well-defined mesoscopic regime. We demonstrate that these mesoscopic superpositions have a purely relativistic origin and disappear in the nonrelativistic limit.

  8. Raise Test Scores: Integrate Biology and Calculus.

    ERIC Educational Resources Information Center

    Lukens, Jeffrey D.; Feinstein, Sheryl

    This paper presents the results of research that compared the academic achievement of high school students enrolled in an integrated Advanced Placement Biology/Advanced Placement Calculus course with students enrolled in traditional Advanced Placement Biology and Advanced Placement Calculus courses. Study subjects included high school students…

  9. Mesoscopic Simulations of Crosslinked Polymer Networks

    NASA Astrophysics Data System (ADS)

    Megariotis, Grigorios; Vogiatzis, Georgios G.; Schneider, Ludwig; Müller, Marcus; Theodorou, Doros N.

    2016-08-01

    A new methodology and the corresponding C++ code for mesoscopic simulations of elastomers are presented. The test system, crosslinked ds-1’4-polyisoprene’ is simulated with a Brownian Dynamics/kinetic Monte Carlo algorithm as a dense liquid of soft, coarse-grained beads, each representing 5-10 Kuhn segments. From the thermodynamic point of view, the system is described by a Helmholtz free-energy containing contributions from entropic springs between successive beads along a chain, slip-springs representing entanglements between beads on different chains, and non-bonded interactions. The methodology is employed for the calculation of the stress relaxation function from simulations of several microseconds at equilibrium, as well as for the prediction of stress-strain curves of crosslinked polymer networks under deformation.

  10. Mesoscopic electronics beyond DC transport

    NASA Astrophysics Data System (ADS)

    di Carlo, Leonardo

    Since the inception of mesoscopic electronics in the 1980's, direct current (dc) measurements have underpinned experiments in quantum transport. Novel techniques complementing dc transport are becoming paramount to new developments in mesoscopic electronics, particularly as the road is paved toward quantum information processing. This thesis describes seven experiments on GaAs/AlGaAs and graphene nanostructures unified by experimental techniques going beyond traditional dc transport. Firstly, dc current induced by microwave radiation applied to an open chaotic quantum dot is investigated. Asymmetry of mesoscopic fluctuations of induced current in perpendicular magnetic field is established as a tool for separating the quantum photovoltaic effect from classical rectification. A differential charge sensing technique is next developed using integrated quantum point contacts to resolve the spatial distribution of charge inside a double quantum clot. An accurate method for determining interdot tunnel coupling and electron temperature using charge sensing is demonstrated. A two-channel system for detecting current noise in mesoscopic conductors is developed, enabling four experiments where shot noise probes transmission properties not available in dc transport and Johnson noise serves as an electron thermometer. Suppressed shot noise is observed in quantum point contacts at zero parallel magnetic field, associated with the 0.7 structure in conductance. This suppression evolves with increasing field into the shot-noise signature of spin-lifted mode degeneracy. Quantitative agreement is found with a phenomenological model for density-dependent mode splitting. Shot noise measurements of multi-lead quantum-dot structures in the Coulomb blockade regime distill the mechanisms by which Coulomb interaction and quantum indistinguishability correlate electron flow. Gate-controlled sign reversal of noise cross correlation in two capacitively-coupled dots is observed, and shown to

  11. Statistics and Hypothesis Testing in Biology.

    ERIC Educational Resources Information Center

    Maret, Timothy J.; Ziemba, Robert E.

    1997-01-01

    Suggests that early in their education students be taught to use basic statistical tests as rigorous methods of comparing experimental results with scientific hypotheses. Stresses that students learn how to use statistical tests in hypothesis-testing by applying them in actual hypothesis-testing situations. To illustrate, uses questions such as…

  12. Multidimensional Computerized Adaptive Testing for Indonesia Junior High School Biology

    ERIC Educational Resources Information Center

    Kuo, Bor-Chen; Daud, Muslem; Yang, Chih-Wei

    2015-01-01

    This paper describes a curriculum-based multidimensional computerized adaptive test that was developed for Indonesia junior high school Biology. In adherence to the Indonesian curriculum of different Biology dimensions, 300 items was constructed, and then tested to 2238 students. A multidimensional random coefficients multinomial logit model was…

  13. Mesoscopic superconductor-semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Klapwijk, T. M.

    1994-03-01

    A summary is given of recent results on carrier transport in mesoscopic conductors with superconducting electrodes. Three-dimensional transport in the diffusive limit is studied with crystalline silicon membranes sandwiched between two niobium electrodes or between one electrode superconducting and one normal. At low temperatures, inelastic scattering is negligible in the intermediate silicon layer. At finite voltages the distribution of electrons over the energies in the silicon is found to be strongly nonthermal, with details depending on the interplay between Andreev scattering and elastic scattering at the interfaces. At small voltages, well below the gap-voltage, transport is phase-coherent. A supercurrent is found if both electrodes are superconducting, provided the membrane is thin enough. If only one electrode is superconducting or for thick membranes an enhanced conductance is observed, which decreases with increasing voltage and magnetic field. Two-dimensional transport and the ballistic regime are being studied by using InAs- and GaAs-based heterostructures. Various interesting theoretical predictions have been made and some novel phenomena have been discovered experimentally. Interesting new phenomena have also been found in mesoscopic normal metals with superconducting electrodes.

  14. Comparison of agriculture biology and general biology testing outcomes in Utah

    NASA Astrophysics Data System (ADS)

    Despain, Deric Walter

    Agriculture education can take scientific topics to higher levels, emphasize scientific concepts, involve hands-on learning, and develop interrelationships with the other sciences, thus making the living and non-living world around them relevant for students. Prior to 1996, agriculture education was not considered adequate to prepare Utah high school students to meet state biology requirements. The appropriateness of making that equalizing decision in 1996 was not tested until this 2014 study, comparing student test scores on the state biology test for general biology and agriculture biology students. The 2008-2012 data were collected from the Utah Department of Education Data and Statistics, utilizing a descriptive comparative post-test only analysis. As seen in this study, not only did B/AS students tend to score lower than their General Biology counterparts, in multiple cases this difference was significant (p ≤ .05). This contrary finding challenges the theoretical foundation of this study. As a result of this study three implications were made; (a) the Utah CRT-Biology test is not a reliable gauge of academic achievement in agriculture biology, (b) agriculture students in the sample population have not been taught with rigorous biology standards, and (c) biology standards taught in agricultural biology classes are not aligned with content tested by the biology portion of the Utah CRT-Biology test standards. The results of this study indicate to stakeholders that there is a gap occurring within the B/AS education, and the need to reevaluate the biology curriculum delivery to its population may possibly be in need of immediate action.

  15. Biologically false positive reactions to serological tests for syphilis

    PubMed Central

    Kostant, George H.

    1956-01-01

    The frequency of biologically false positive reactions to serological tests for syphilis depends on a number of factors, including the individual immunological response, the number and type of serological tests performed, and the stage of the disease producing such reactions; the relative importance of such factors is discussed. The author also considers in detail the diseases or conditions giving rise to acute or chronic biologically false positive reactions. A variety of verification tests exists for differentiating the true syphilitic reaction from the biologically false positive reaction, but none is so accurate as the Treponema pallidum immobilization and immune adherence tests, which the author considers should be used when others have proved inconclusive. In the final section of his paper, he indicates the steps to be followed in attempting to distinguish between latent syphilis and biologically false positive reactions in persons with positive serological tests but no anamnestic or clinical evidence of syphilis. PMID:13329848

  16. Nonequilibrium mesoscopic transport: a genealogy

    NASA Astrophysics Data System (ADS)

    Das, Mukunda P.; Green, Frederick

    2012-05-01

    Models of nonequilibrium quantum transport underpin all modern electronic devices, from the largest scales to the smallest. Past simplifications such as coarse graining and bulk self-averaging served well to understand electronic materials. Such particular notions become inapplicable at mesoscopic dimensions, edging towards the truly quantum regime. Nevertheless a unifying thread continues to run through transport physics, animating the design of small-scale electronic technology: microscopic conservation and nonequilibrium dissipation. These fundamentals are inherent in quantum transport and gain even greater and more explicit experimental meaning in the passage to atomic-sized devices. We review their genesis, their theoretical context, and their governing role in the electronic response of meso- and nanoscopic systems.

  17. Biologic concentration testing in inflammatory bowel disease.

    PubMed

    Vaughn, Byron P; Sandborn, William J; Cheifetz, Adam S

    2015-06-01

    Anti-TNF medications have revolutionized the care of patients with inflammatory bowel disease. However, despite an initial robust effect, loss of response is common and long-term results are disappointing. Much of this lack of durability may be due to inadequate dose optimization, and recent studies suggest a correlation between serum drug concentrations and clinical outcomes. Currently, in clinical practice, measurement of drug concentrations and antibodies to drug are typically performed only when a patient presents with active inflammatory bowel disease symptoms or during a potential immune-mediated reaction to anti-TNF ("reactive" setting). However, proactive monitoring of anti-TNF concentrations with titration to a therapeutic window (i.e., therapeutic concentration monitoring) represents a new strategy with many potential clinical benefits including prevention of immunogenicity, less need for IFX rescue therapy, and greater durability of IFX treatment. This review will cover the salient features of anti-TNF pharmacokinetics and pharmacodynamics and provide a rational approach for the use of anti-TNF concentration testing in both the reactive and proactive settings. PMID:25590953

  18. Seismological Field Observation of Mesoscopic Nonlinearity

    NASA Astrophysics Data System (ADS)

    Sens-Schönfelder, Christoph; Gassenmeier, Martina; Eulenfeld, Tom; Tilmann, Frederik; Korn, Michael; Niederleithinger, Ernst

    2016-04-01

    Noise based observations of seismic velocity changes have been made in various environments. We know of seasonal changes of velocities related to ground water or temperature changes, co-seismic changes originating from shaking or stress redistribution and changes related to volcanic activity. Is is often argued that a decrease of velocity is related to the opening of cracks while the closure of cracks leads to a velocity increase if permanent stress changes are invoked. In contrast shaking induced changes are often related to "damage" and subsequent "healing" of the material. The co-seismic decrease and transient recovery of seismic velocities can thus be explained with both - static stress changes or damage/healing processes. This results in ambiguous interpretations of the observations. Here we present the analysis of one particular seismic station in northern Chile that shows very strong and clear velocity changes associated with several earthquakes ranging from Mw=5.3 to Mw=8.1. The fact that we can observe the response to several events of various magnitudes from different directions offers the unique possibility to discern the two possible causative processes. We test the hypothesis, that the velocity changes are related to shaking rather than stress changes by developing an empirical model that is based on the local ground acceleration at the sensor site. The eight year of almost continuous observations of velocity changes are well modeled by a daily drop of the velocity followed by an exponential recovery. Both, the amplitude of the drop as well as the recovery time are proportional to the integrated acceleration at the seismic station. Effects of consecutive days are independent and superimposed resulting in strong changes after earthquakes and constantly increasing velocities during quiet days thereafter. This model describes the continuous observations of the velocity changes solely based on the acceleration time series without individually defined dates

  19. UNDERSTANDINGS OF BSCS BIOLOGY STUDENTS AS DETERMINED BY INSTRUCTIONAL TESTS.

    ERIC Educational Resources Information Center

    ROBINSON, JAMES T.

    EIGHT INSTRUCTIONAL TESTS SPANNED THE CURRICULUM OF ONE YEAR OF BIOLOGY STUDY. THE FIRST CONCERNED THE NATURE OF SCIENCE INCLUDED 4 AREAS OF EMPHASIS--THE NATURE AND FUNCTION OF HYPOTHESIS, THE IDEA OF CONTROLS IN EXPERIMENTS, INTERPRETATION OF GRAPHED DATA, AND THE NATURE OF DATA. THE SECOND TEST WAS DESIGNED TO SHOW AN UNDERSTANDING OF…

  20. Mesoscopic Modeling of Reactive Transport Processes

    NASA Astrophysics Data System (ADS)

    Kang, Q.; Chen, L.; Deng, H.

    2012-12-01

    Reactive transport processes involving precipitation and/or dissolution are pervasive in geochemical, biological and engineered systems. Typical examples include self-assembled patterns such as Liesegang rings or bands, cones of stalactites in limestones caves, biofilm growth in aqueous environment, formation of mineral deposits in boilers and heat exchangers, uptake of toxic metal ions from polluted water by calcium carbonate, and mineral trapping of CO2. Compared to experimental studies, a numerical approach enables a systematic study of the reaction kinetics, mass transport, and mechanisms of nucleation and crystal growth, and hence provides a detailed description of reactive transport processes. In this study, we enhance a previously developed lattice Boltzmann pore-scale model by taking into account the nucleation process, and develop a mesoscopic approach to simulate reactive transport processes involving precipitation and/or dissolution of solid phases. The model is then used to simulate the formation of Liesegang precipitation patterns and investigate the effects of gel on the morphology of the precipitates. It is shown that this model can capture the porous structures of the precipitates and can account for the effects of the gel concentration and material. A wide range of precipitation patterns is predicted under different gel concentrations, including regular bands, treelike patterns, and for the first time with numerical models, transition patterns from regular bands to treelike patterns. The model is also applied to study the effect of secondary precipitate on the dissolution of primary mineral. Several types of dissolution and precipitation processes are identified based on the morphology and structures of the precipitates and on the extent to which the precipitates affect the dissolution of the primary mineral. Finally the model is applied to study the formation of pseudomorph. It is demonstrated for the first time by numerical simulation that a

  1. Revealing mesoscopic structural universality with diffusion.

    PubMed

    Novikov, Dmitry S; Jensen, Jens H; Helpern, Joseph A; Fieremans, Els

    2014-04-01

    Measuring molecular diffusion is widely used for characterizing materials and living organisms noninvasively. This characterization relies on relations between macroscopic diffusion metrics and structure at the mesoscopic scale commensurate with the diffusion length. Establishing such relations remains a fundamental challenge, hindering progress in materials science, porous media, and biomedical imaging. Here we show that the dynamical exponent in the time dependence of the diffusion coefficient distinguishes between the universality classes of the mesoscopic structural complexity. Our approach enables the interpretation of diffusion measurements by objectively selecting and modeling the most relevant structural features. As an example, the specific values of the dynamical exponent allow us to identify the relevant mesoscopic structure affecting MRI-measured water diffusion in muscles and in brain, and to elucidate the structural changes behind the decrease of diffusion coefficient in ischemic stroke.

  2. Accurate atom counting in mesoscopic ensembles.

    PubMed

    Hume, D B; Stroescu, I; Joos, M; Muessel, W; Strobel, H; Oberthaler, M K

    2013-12-20

    Many cold atom experiments rely on precise atom number detection, especially in the context of quantum-enhanced metrology where effects at the single particle level are important. Here, we investigate the limits of atom number counting via resonant fluorescence detection for mesoscopic samples of trapped atoms. We characterize the precision of these fluorescence measurements beginning from the single-atom level up to more than one thousand. By investigating the primary noise sources, we obtain single-atom resolution for atom numbers as high as 1200. This capability is an essential prerequisite for future experiments with highly entangled states of mesoscopic atomic ensembles.

  3. Translating biological parameters into clinically useful diagnostic tests.

    PubMed

    Arfken, Cynthia L; Carney, Stuart; Boutros, Nash N

    2009-08-01

    Psychiatry has lagged behind other specialties in developing diagnostic laboratory tests for the purpose of confirming or ruling out a diagnosis. Biological research into the pathophysiology of psychiatric disorders has, however, yielded some highly replicable abnormalities that have the potential for development into clinically useful diagnostic tests. To achieve this goal, a process for systematic translation must be developed and implemented. Building on our previous work, we review a proposed process using four clearly defined steps. We conclude that biological parameters currently face challenges in their pathways to becoming diagnostic tests because of both the premature release and premature abandonment of tests. Attention to a systematic translation process aided by these principles may help to avoid these problems.

  4. A new biological test of water toxicity-yeast Saccharomyces cerevisiae conductometric test.

    PubMed

    Dolezalova, Jaroslava; Rumlova, Lubomira

    2014-11-01

    This new biological test of water toxicity is based on monitoring of specific conductivity changes of yeast Saccharomyces cerevisiae suspension as a result of yeast fermentation activity inhibition in toxic conditions. The test was verified on ten substances with various mechanisms of toxic effect and the results were compared with two standard toxicity tests based on Daphnia magna mobility inhibition (EN ISO 6341) and Vibrio fischeri bioluminescence inhibition (EN ISO 11348-2) and with the results of the S. cerevisiae lethal test (Rumlova and Dolezalova, 2012). The new biological test - S. cerevisiae conductometric test - is an express method developed primarily for field conditions. It is applicable in case of need of immediate information about water toxicity. Fast completion is an advantage of this test (time necessary for test completion is about 60min), the test is simple and the test organism - dried instant yeast - belongs among its biggest advantages because of its long-term storage life and broad availability.

  5. Mesoscopic Rings with Spin-Orbit Interactions

    ERIC Educational Resources Information Center

    Berche, Bertrand; Chatelain, Christophe; Medina, Ernesto

    2010-01-01

    A didactic description of charge and spin equilibrium currents on mesoscopic rings in the presence of spin-orbit interaction is presented. Emphasis is made on the non-trivial construction of the correct Hamiltonian in polar coordinates, the calculation of eigenvalues and eigenfunctions and the symmetries of the ground-state properties. Spin…

  6. Testing of Synthetic Biological Membranes for Forward Osmosis Applications

    NASA Technical Reports Server (NTRS)

    Parodi, Jurek; Mangado, Jaione Romero; Stefanson, Ofir; Flynn, Michael; Mancinelli, Rocco; Kawashima, Brian; Trieu, Serena; Brozell, Adrian; Rosenberg, Kevan

    2016-01-01

    Commercially available forward osmosis membranes have been extensively tested for human space flight wastewater treatment. Despite the improvements achieved in the last decades, there is still a challenge to produce reliable membranes with anti-fouling properties, chemical resistance, and high flux and selectivity. Synthetic biological membranes that mimic the ones present in nature, which underwent millions of years of evolution, represent a potential solution for further development and progress in membrane technology. Biomimetic forward osmosis membranes based on a polymeric support filter and coated with surfactant multilayers have been engineered to investigate how different manufacturing processes impact the performance and structure of the membrane. However, initial results of the first generation prototype membranes tests reveal a high scatter in the data, due to the current testing apparatus set up. The testing apparatus has been upgraded to improve data collection, reduce errors, and to allow higher control of the testing process.

  7. Biological testing of a digested sewage sludge and derived composts.

    PubMed

    Moreira, R; Sousa, J P; Canhoto, C

    2008-11-01

    Aiming to evaluate a possible loss of soil habitat function after amendment with organic wastes, a digested sewage sludge and derived composts produced with green residues, where biologically tested in the laboratory using soil animals (Eisenia andrei and Folsomia candida) and plants (Brassica rapa and Avena sativa). Each waste was tested mimicking a field application of 6ton/ha or 12ton/ha. Avoidance tests did not reveal any impact of sludge and composts to soil biota. Germination and growth tests showed that application of composts were beneficial for both plants. Composts did not affect earthworm's mass increase or reproduction, but the highest sludge amendment revealed negative effects on both parameters. Only the amendment of composts at the highest dose originated an impairment of springtails reproductive output. We suggest that bioassays using different test species may be an additional tool to evaluate effects of amendment of organic wastes in soil. Biological tests are sensitive to pollutants at low concentrations and to interactions undetected by routine chemical analysis.

  8. Wave basin model tests of technical-biological bank protection

    NASA Astrophysics Data System (ADS)

    Eisenmann, J.

    2012-04-01

    Sloped embankments of inland waterways are usually protected from erosion and other negative im-pacts of ship-induced hydraulic loads by technical revetments consisting of riprap. Concerning the dimensioning of such bank protection there are several design rules available, e.g. the "Principles for the Design of Bank and Bottom Protection for Inland Waterways" or the Code of Practice "Use of Standard Construction Methods for Bank and Bottom Protection on Waterways" issued by the BAW (Federal Waterways Engineering and Research Institute). Since the European Water Framework Directive has been put into action special emphasis was put on natural banks. Therefore the application of technical-biological bank protection is favoured. Currently design principles for technical-biological bank protection on inland waterways are missing. The existing experiences mainly refer to flowing waters with no or low ship-induced hydraulic loads on the banks. Since 2004 the Federal Waterways Engineering and Research Institute has been tracking the re-search and development project "Alternative Technical-Biological Bank Protection on Inland Water-ways" in company with the Federal Institute of Hydrology. The investigation to date includes the ex-amination of waterway sections where technical- biological bank protection is applied locally. For the development of design rules for technical-biological bank protection investigations shall be carried out in a next step, considering the mechanics and resilience of technical-biological bank protection with special attention to ship-induced hydraulic loads. The presentation gives a short introduction into hydraulic loads at inland waterways and their bank protection. More in detail model tests of a willow brush mattress as a technical-biological bank protec-tion in a wave basin are explained. Within the scope of these tests the brush mattresses were ex-posed to wave impacts to determine their resilience towards hydraulic loads. Since the

  9. Mesoscopic structure conditions the emergence of cooperation on social networks

    SciTech Connect

    Lozano, S.; Arenas, A.; Sanchez, A.

    2008-12-01

    We study the evolutionary Prisoner's Dilemma on two social networks substrates obtained from actual relational data. We find very different cooperation levels on each of them that cannot be easily understood in terms of global statistical properties of both networks. We claim that the result can be understood at the mesoscopic scale, by studying the community structure of the networks. We explain the dependence of the cooperation level on the temptation parameter in terms of the internal structure of the communities and their interconnections. We then test our results on community-structured, specifically designed artificial networks, finding a good agreement with the observations in both real substrates. Our results support the conclusion that studies of evolutionary games on model networks and their interpretation in terms of global properties may not be sufficient to study specific, real social systems. Further, the study allows us to define new quantitative parameters that summarize the mesoscopic structure of any network. In addition, the community perspective may be helpful to interpret the origin and behavior of existing networks as well as to design structures that show resilient cooperative behavior.

  10. Frozen magnetic response in mesoscopics superconductors

    NASA Astrophysics Data System (ADS)

    Durán Flórez, F.; V-Niño, E. D.; Barba-Ortega, J.

    2016-08-01

    For a bulk type II superconducting sample at low temperature, the magnetic field can penetrate in the form of a single quantum fluxoid, for bulk samples this fluxoides are arranged in a hexagonal lattice, this so-called Shubnikov-Abrikosov state or vortex state and takes place between the first and the second critical thermodynamics magnetic fields. Under the first magnetic critical field is present the Meissner-Oschenfeld state. For mesoscopic samples, the magnetic response can present very interesting properties due the proximity effect of in-homogeneous boundary conditions and the presence of dots, anti-dots and/or impurities. The superconducting state in a mesoscopic sample with dot/anti-dot/dot/pillar/trench is calculated within the nonlinear Ginzburg-Landau equations. We predict that the critical magnetic fields and magnetization depends on strongly of the nature, geometry, size of the defects and the boundary conditions used.

  11. Harvesting dissipated energy with a mesoscopic ratchet

    NASA Astrophysics Data System (ADS)

    Roche, B.; Roulleau, P.; Jullien, T.; Jompol, Y.; Farrer, I.; Ritchie, D. A.; Glattli, D. C.

    2015-04-01

    The search for new efficient thermoelectric devices converting waste heat into electrical energy is of major importance. The physics of mesoscopic electronic transport offers the possibility to develop a new generation of nanoengines with high efficiency. Here we describe an all-electrical heat engine harvesting and converting dissipated power into an electrical current. Two capacitively coupled mesoscopic conductors realized in a two-dimensional conductor form the hot source and the cold converter of our device. In the former, controlled Joule heating generated by a voltage-biased quantum point contact results in thermal voltage fluctuations. By capacitive coupling the latter creates electric potential fluctuations in a cold chaotic cavity connected to external leads by two quantum point contacts. For unequal quantum point contact transmissions, a net electrical current is observed proportional to the heat produced.

  12. Harvesting dissipated energy with a mesoscopic ratchet.

    PubMed

    Roche, B; Roulleau, P; Jullien, T; Jompol, Y; Farrer, I; Ritchie, D A; Glattli, D C

    2015-04-01

    The search for new efficient thermoelectric devices converting waste heat into electrical energy is of major importance. The physics of mesoscopic electronic transport offers the possibility to develop a new generation of nanoengines with high efficiency. Here we describe an all-electrical heat engine harvesting and converting dissipated power into an electrical current. Two capacitively coupled mesoscopic conductors realized in a two-dimensional conductor form the hot source and the cold converter of our device. In the former, controlled Joule heating generated by a voltage-biased quantum point contact results in thermal voltage fluctuations. By capacitive coupling the latter creates electric potential fluctuations in a cold chaotic cavity connected to external leads by two quantum point contacts. For unequal quantum point contact transmissions, a net electrical current is observed proportional to the heat produced.

  13. A NONLINEAR MESOSCOPIC ELASTIC CLASS OF MATERIALS

    SciTech Connect

    P. JOHNSON; R. GUYER; L. OSTROVSKY

    1999-09-01

    It is becoming clear that the elastic properties of rock are shared by numerous other materials (sand, soil, some ceramics, concrete, etc.). These materials have one or more of the following properties in common strong nonlinearity, hysteresis in stress-strain relation, slow dynamics and discrete memory. Primarily, it is the material's compliance, the mesoscopic linkages between the rigid components, that give these materials their unusual elastic properties.

  14. Entropy production in mesoscopic stochastic thermodynamics: nonequilibrium kinetic cycles driven by chemical potentials, temperatures, and mechanical forces

    NASA Astrophysics Data System (ADS)

    Qian, Hong; Kjelstrup, Signe; Kolomeisky, Anatoly B.; Bedeaux, Dick

    2016-04-01

    Nonequilibrium thermodynamics (NET) investigates processes in systems out of global equilibrium. On a mesoscopic level, it provides a statistical dynamic description of various complex phenomena such as chemical reactions, ion transport, diffusion, thermochemical, thermomechanical and mechanochemical fluxes. In the present review, we introduce a mesoscopic stochastic formulation of NET by analyzing entropy production in several simple examples. The fundamental role of nonequilibrium steady-state cycle kinetics is emphasized. The statistical mechanics of Onsager’s reciprocal relations in this context is elucidated. Chemomechanical, thermomechanical, and enzyme-catalyzed thermochemical energy transduction processes are discussed. It is argued that mesoscopic stochastic NET in phase space provides a rigorous mathematical basis of fundamental concepts needed for understanding complex processes in chemistry, physics and biology. This theory is also relevant for nanoscale technological advances.

  15. Toxicity testing and instream biological monitoring in evaluating municipal effluents

    SciTech Connect

    Krier, K.; Pontasch, K.

    1995-12-31

    Twelve streams receiving municipal wastewater treatment plant effluents were evaluated in riffle areas above and below the outfall using the Environmental Protection Agency`s Rapid Bioassessment Protocols (RBPs) for benthic macroinvertebrates. Eight of the sites evaluated using RBP 1 exhibited stream health in the downstream riffles equaling or exceeding the upstream riffles. RBP 1 results suggested possible impacts at the remaining four sites, and these sites were more intensely evaluated using RBPs 2 and 3, acute effluent toxicity tests with Daphnia magna, and quantification of periphytic chlorophyll a and ash free dry weight (AFDW). Results from RBP 2 indicated three of the four sites evaluated have similar taxonomic richness above and below the outfall, while one site is heavily impacted by organic pollutants. Toxicity tests with 100% effluent resulted in no mortality with any of the four effluents tested. Relative to the respective upstream sites, chlorophyll a was significantly increased at one downstream site and significantly reduced at another. AFDW was similar above and below the outfalls in all streams. These results suggest that laboratory toxicity tests may not always be adequate predictors of instream biological effects.

  16. Intrinsic noise alters the frequency spectrum of mesoscopic oscillatory chemical reaction systems

    PubMed Central

    Ramaswamy, Rajesh; Sbalzarini, Ivo F.

    2011-01-01

    Mesoscopic oscillatory reaction systems, for example in cell biology, can exhibit stochastic oscillations in the form of cyclic random walks even if the corresponding macroscopic system does not oscillate. We study how the intrinsic noise from molecular discreteness influences the frequency spectrum of mesoscopic oscillators using as a model system a cascade of coupled Brusselators away from the Hopf bifurcation. The results show that the spectrum of an oscillator depends on the level of noise. In particular, the peak frequency of the oscillator is reduced by increasing noise, and the bandwidth increased. Along a cascade of coupled oscillators, the peak frequency is further reduced with every stage and also the bandwidth is reduced. These effects can help understand the role of noise in chemical oscillators and provide fingerprints for more reliable parameter identification and volume measurement from experimental spectra. PMID:22545192

  17. Prediction and Testing of Biological Networks Underlying Intestinal Cancer

    PubMed Central

    Mariadason, John M.; Wang, Donghai; Augenlicht, Leonard H.; Chance, Mark R.

    2010-01-01

    Colorectal cancer progresses through an accumulation of somatic mutations, some of which reside in so-called “driver” genes that provide a growth advantage to the tumor. To identify points of intersection between driver gene pathways, we implemented a network analysis framework using protein interactions to predict likely connections – both precedented and novel – between key driver genes in cancer. We applied the framework to find significant connections between two genes, Apc and Cdkn1a (p21), known to be synergistic in tumorigenesis in mouse models. We then assessed the functional coherence of the resulting Apc-Cdkn1a network by engineering in vivo single node perturbations of the network: mouse models mutated individually at Apc (Apc1638N+/−) or Cdkn1a (Cdkn1a−/−), followed by measurements of protein and gene expression changes in intestinal epithelial tissue. We hypothesized that if the predicted network is biologically coherent (functional), then the predicted nodes should associate more specifically with dysregulated genes and proteins than stochastically selected genes and proteins. The predicted Apc-Cdkn1a network was significantly perturbed at the mRNA-level by both single gene knockouts, and the predictions were also strongly supported based on physical proximity and mRNA coexpression of proteomic targets. These results support the functional coherence of the proposed Apc-Cdkn1a network and also demonstrate how network-based predictions can be statistically tested using high-throughput biological data. PMID:20824133

  18. Membrane characteristics for biological blast overpressure testing using blast simulators.

    PubMed

    Alphonse, Vanessa D; Siva Sai Sujith Sajja, Venkata; Kemper, Andrew R; Rizel, Dave V; Duma, Stefan M; VandeVord, Pamela J

    2014-01-01

    Blast simulators often use passive-rupture membranes to generate shock waves similar to free-field blasts. The purpose of this study was to compare rupture patterns and pressure traces of three distinct membrane materials for biological and biomechanical blast studies. An Advanced Blast Simulator (ABS) located at the Center for Injury Biomechanics at Virginia Tech was used to test membrane characteristics. Acetate, Mylar, and aluminum sheets with different thicknesses were used to obtain pressures between 70–210 kPa. Static pressure was measured inside the tube at the test section using piezoelectric pressure sensors. Peak overpressure, positive duration, and positive impulse were calculated for each test. Rupture patterns and characteristic pressure traces were unique to each membrane type and thickness. Shock wave speed ranged between 1.2-1.8 Mach for static overpressures of 70–210 kPa. Acetate membranes fragmented sending pieces down the tube, but produced ideal (Friedlander) pressure traces. Mylar membranes bulged without fragmenting, but produced less-than-ideal pressure traces. Aluminum membranes did not fragment and produced ideal pressure traces. However, the cost of manufacturing and characterizing aluminum membranes should be considered during membrane selection. This study illustrates the advantages and disadvantages of using Mylar, acetate, and aluminum for passive rupture membranes for blast simulators. PMID:25405432

  19. Dynamic quantum tunneling in mesoscopic driven Duffing oscillators.

    PubMed

    Guo, Lingzhen; Zheng, Zhigang; Li, Xin-Qi; Yan, Yijing

    2011-07-01

    We investigate the dynamic quantum tunneling between two attractors of a mesoscopic driven Duffing oscillator. We find that, in addition to inducing a remarkable quantum shift of the bifurcation point, the mesoscopic nature also results in a perfect linear scaling behavior for the tunneling rate with the driving distance to the shifted bifurcation point. PMID:21867149

  20. Quantum measurement of a mesoscopic spin ensemble

    SciTech Connect

    Giedke, G.; Taylor, J. M.; Lukin, M. D.; D'Alessandro, D.; Imamoglu, A.

    2006-09-15

    We describe a method for precise estimation of the polarization of a mesoscopic spin ensemble by using its coupling to a single two-level system. Our approach requires a minimal number of measurements on the two-level system for a given measurement precision. We consider the application of this method to the case of nuclear-spin ensemble defined by a single electron-charged quantum dot: we show that decreasing the electron spin dephasing due to nuclei and increasing the fidelity of nuclear-spin-based quantum memory could be within the reach of present day experiments.

  1. Mesoscopic virial equation for nonequilibrium statistical mechanics

    NASA Astrophysics Data System (ADS)

    Falasco, G.; Baldovin, F.; Kroy, K.; Baiesi, M.

    2016-09-01

    We derive a class of mesoscopic virial equations governing energy partition between conjugate position and momentum variables of individual degrees of freedom. They are shown to apply to a wide range of nonequilibrium steady states with stochastic (Langevin) and deterministic (Nosé-Hoover) dynamics, and to extend to collective modes for models of heat-conducting lattices. A macroscopic virial theorem ensues upon summation over all degrees of freedom. It allows for the derivation of generalised (nonequilibrium) equations of state that involve average dissipative heat flows besides genuine state variables, as exemplified for inertial Brownian motion with solid friction and overdamped active Brownian particles subject to inhomogeneous pressure.

  2. Flux qubit on a mesoscopic nonsuperconducting ring

    NASA Astrophysics Data System (ADS)

    Zipper, E.; Kurpas, M.; Szeląg, M.; Dajka, J.; Szopa, M.

    2006-09-01

    The possibility of making a flux qubit on a nonsuperconducting mesoscopic ballistic quasi-one-dimensional ring is discussed. We showed that such a ring can be effectively reduced to a two-state system with two external control parameters. The two states carry opposite persistent currents and are coupled by tunneling, which leads to a quantum superposition of states. The qubit states can be manipulated by resonant microwave pulses. The flux state of the sample can be measured by a superconducting quantum interference device magnetometer. Two or more qubits can be coupled by the flux the circulating currents generate. The problem of decoherence is also discussed.

  3. Current Correlations from a Mesoscopic Anyon Collider.

    PubMed

    Rosenow, Bernd; Levkivskyi, Ivan P; Halperin, Bertrand I

    2016-04-15

    Fermions and bosons are fundamental realizations of exchange statistics, which governs the probability for two particles being close to each other spatially. Anyons in the fractional quantum Hall effect are an example for exchange statistics intermediate between bosons and fermions. We analyze a mesoscopic setup in which two dilute beams of anyons collide with each other, and relate the correlations of current fluctuations to the probability of particles excluding each other spatially. While current correlations for fermions vanish, negative correlations for anyons are a clear signature of a reduced spatial exclusion as compared to fermions.

  4. The Mesoscopic Electrochemistry of Molecular Junctions

    PubMed Central

    Bueno, Paulo R.; Benites, Tiago A.; Davis, Jason J.

    2016-01-01

    Within the context of an electron dynamic (time-dependent) perspective and a voltage driving force acting to redistribute electrons between metallic and addressable molecular states, we define here the associated electron admittance and conductance. We specifically present a mesoscopic approach to resolving the electron transfer rate associated with the electrochemistry of a redox active film tethered to metallic leads and immersed in electrolyte. The methodology is centred on aligning the lifetime of the process of electron exchange with associated resistance and capacitance quantities. Notably, however, these are no longer those empirically known as charge transfer resistance and pseudo-capacitance, but are those derived instead from a consideration of the quantum states contained in molecular films and their accessibility through a scattering region existing between them and the metallic probe. The averaged lifetime (τr) associated with the redox site occupancy is specifically dependent on scattering associated with the quantum channels linking them to the underlying metallic continuum and associated with both a quantum resistance (Rq) and an electrochemical (redox) capacitance (Cr). These are related to electron transfer rate through k = 1/τr = (RqCr)−1. The proposed mesoscopic approach is consistent with Marcus’s (electron transfer rate) theory and experimental measurements obtained by capacitance spectroscopy. PMID:26757677

  5. Mesoscopic Simulation Methods for Polymer Dynamics

    NASA Astrophysics Data System (ADS)

    Larson, Ronald

    2015-03-01

    We assess the accuracy and efficiency of mesoscopic simulation methods, namely Brownian Dynamics (BD), Stochastic Rotation Dynamics (SRD) and Dissipative Particle Dynamics (DPD), for polymers in solution at equilibrium and in flows in microfluidic geometries. Both SRD and DPD use solvent ``particles'' to carry momentum, and so account automatically for hydrodynamic interactions both within isolated polymer coils, and with other polymer molecules and with nearby solid boundaries. We assess quantitatively the effects of artificial particle inertia and fluid compressibility and show that they can be made small with appropriate choice of simulation parameters. We then use these methods to study flow-induced migration of polymer chains produced by: 1) hydrodynamic interactions, 2) streamline curvature or stress-gradients, and 3) convection of wall depletion zones. We show that huge concentration gradients can be produced by these mechanisms in microfluidic geometries that can be exploited for separation of polymers by size in periodic contraction-expansion geometries. We also assess the range of conditions for which BD, SRD or DPD is preferable for mesoscopic simulations. Finally, we show how such methods can be used to simulate quantitatively the swimming of micro-organisms such as E. coli. In collaboration with Lei Jiang and Tongyang Zhao, University of Michigan, Ann Arbor, MI.

  6. The Mesoscopic Electrochemistry of Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Bueno, Paulo R.; Benites, Tiago A.; Davis, Jason J.

    2016-01-01

    Within the context of an electron dynamic (time-dependent) perspective and a voltage driving force acting to redistribute electrons between metallic and addressable molecular states, we define here the associated electron admittance and conductance. We specifically present a mesoscopic approach to resolving the electron transfer rate associated with the electrochemistry of a redox active film tethered to metallic leads and immersed in electrolyte. The methodology is centred on aligning the lifetime of the process of electron exchange with associated resistance and capacitance quantities. Notably, however, these are no longer those empirically known as charge transfer resistance and pseudo-capacitance, but are those derived instead from a consideration of the quantum states contained in molecular films and their accessibility through a scattering region existing between them and the metallic probe. The averaged lifetime (τr) associated with the redox site occupancy is specifically dependent on scattering associated with the quantum channels linking them to the underlying metallic continuum and associated with both a quantum resistance (Rq) and an electrochemical (redox) capacitance (Cr). These are related to electron transfer rate through k = 1/τr = (RqCr)‑1. The proposed mesoscopic approach is consistent with Marcus’s (electron transfer rate) theory and experimental measurements obtained by capacitance spectroscopy.

  7. Dephasing of mesoscopic interferences from Electron Fractionalization

    NASA Astrophysics Data System (ADS)

    Lehur, Karyn

    2006-03-01

    The understanding of dephasing processes (the physical causes of supressed interference effects) constitutes a topics of perpetual interest in mesoscopic systems. Phase-breaking mechanisms in ballistic systems of dimensionality less than two are presently not completely understood and therefore deserve intensive theoretical and experimental endeavors. In this talk, we investigate the dephasing of mesoscopic interferences by electron-electron interactions in a well-defined geometry composed of two tunnel-coupled wires embodied by a Luttinger liquid. We thoroughly demonstrate that interactions can produce a visible attenuation of Aharonov-Bohm oscillations [1]. Moreover, in our geometry, we firmly emphasize that the emerging dephasing time results from the electron factionalization phenomenon that is known to produce an electron life-time in 1/T with T being the temperature [2]. A dephasing time in 1/T has been reported in one-dimensional GaAs rings. [1] Karyn Le Hur, Phys. Rev. Lett. 95, 076801 (2005). [2] Karyn Le Hur, Phys. Rev. B 65, 233314 (2002).

  8. Mesoscopic Physics of Electrons and Photons

    NASA Astrophysics Data System (ADS)

    Akkermans, Eric; Montambaux, Gilles

    2001-12-01

    Quantum mesoscopic physics covers a whole class in interference effects related to the propagation of waves in complex and random media. These effects are ubiquitous in physics, from the behaviour of electrons in metals and semiconductors to the propagation of electromagnetic waves in suspensions such as colloids, and quantum systems like cold atomic gases. A solid introduction to quantum mesoscopic physics, this book is a modern account of the problem of coherent wave propagation in random media. It provides a unified account of the basic theoretical tools and methods, highlighting the common aspects of the various optical and electronic phenomena involved and presenting a large number of experimental results. With over 200 figures, and exercises throughout, the book is ideal for graduate students in physics, electrical engineering, applied physics, acoustics and astrophysics. It will also be an interesting reference for researchers in this rapidly evolving field. Presents a large number of experimental results to give readers a broad overview of the field Self-contained, with all elementary presentations of the necessary basic theories in quantum mechanics and scattering theory Contains exercises throughout the book to help readers understand the concepts

  9. Nanocalorimeter for Explorations of Mesoscopic Heat Flow

    NASA Astrophysics Data System (ADS)

    Henriksen, E. A.; Schwab, K. C.; Worlock, J. M.; Roukes, M. L.

    1998-03-01

    Suspended devices, fabricated by surface nanomachining, have recently enabled the first direct phonon transport measurements in nanostructures.(T.S. Tighe, J.M. Worlock, and M.L. Roukes, Appl. Phys. Lett.) 71, 3087 (1997) We are extending these techniques to permit explorations well into the mesoscopic regime where the dominant phonon wavelength greatly exceeds sample dimensions. Our current approach has involved the development of suspended, nanometer-scale devices patterned from undoped GaAs heterostructures to realize calorimeters with extremely small heat capacity. The devices incorporate integral thermal transducers patterned from a heavily doped epilayer. Thermal decoupling from the environment is achieved through narrow superconducting leads. A graded InAs/GaAs epilayer permits ohmic contact between the superconducting Nb leads and the doped n+ GaAs transducers that are used as thermal sensors. These devices appear to offer the possibility of achieving energy sensitivity at the level of individual phonons.

  10. Mesoscopic magnetism and superconductivity: recent perspectives.

    SciTech Connect

    Basaran, Ali C.; Villegas, Javier E.; Jiang, J. S.; Hoffmann, Axel; Schuller, Ivan K.

    2015-11-01

    Mesoscopic Superconductivity and Magnetism at intermediate (“Mesoscopic”) length scales between atomic and bulk, have a long history of interesting new science. The existence of multiple length scales allows for the development of new science when different length scales become comparable to relevant geometric sizes. Different new phenomena appear due to topological interactions, geometric confinement, proximity between dissimilar materials, dimensional crossover, and collective effects induced by the periodicity. In this brief review we are not able to cover comprehensively this vast field. Instead we select a few recent exciting highlights, which illustrate the type of novel science which can be accomplished in superconducting and magnetic structures. Superconductors and magnetic materials can serve as model systems and provide new ideas, which can be extended to other systems such as ferroelectrics and multiferroics. In this paper we also highlight general open questions and new directions in which the field may move.

  11. Vortex phase separation in mesoscopic superconductors

    PubMed Central

    Iaroshenko, O.; Rybalko, V.; Vinokur, V. M.; Berlyand, L.

    2013-01-01

    We demonstrate that in mesoscopic type II superconductors with the lateral size commensurate with London penetration depth, the ground state of vortices pinned by homogeneously distributed columnar defects can form a hierarchical nested domain structure. Each domain is characterized by an average number of vortices trapped at a single pinning site within a given domain. Our study marks a radical departure from the current understanding of the ground state in disordered macroscopic systems and provides an insight into the interplay between disorder, vortex-vortex interaction, and confinement within finite system size. The observed vortex phase segregation implies the existence of the soliton solution for the vortex density in the finite superconductors and establishes a new class of nonlinear systems that exhibit the soliton phenomenon.

  12. Low Frequency Noise in Mesoscopic Magnetic Dots

    NASA Astrophysics Data System (ADS)

    Dahlberg, E. Dan

    2014-03-01

    Measurements of random telegraph noise (RTN) in individual mesoscopic sized NiFe alloy dots will be presented; the dots dimensions are as small as 200nm x 200nm x 10nm. The temperature and magnetic field dependence of the RTN are explained by the energy landscape in the dots; the energy landscape RTN was independently measured [Appl. Phys. Lett. 103, 042409 (2013)]. The research was motivated by questions raised in understanding magnetic noise in magnetic tunnel junctions and giant magnetoresistance devices [Appl. Phys. Lett. 95, 062512 (2009) and Phys. Rev. B 88, 014409 (2013)]. This work was supported primarily by ONR Grant N00014-11-1-0850 and the MRSEC Program of the NSF under Grant No. DMR-0819885. Additional support for work done using the University of Minnesota Nanofabrication Center and Characterization Facility was provided by the NSF NNIN network. Reseach performed in collaboration with Dan Endean, Feng Guo, C. T. Weigelt and R. H. Victora.

  13. Dormancy and Recovery Testing for Biological Wastewater Processors

    NASA Technical Reports Server (NTRS)

    Hummerick, Mary F.; Coutts, Janelle L.; Lunn, Griffin M.; Spencer, LaShelle; Khodadad, Christina L.; Birmele, Michele N.; Frances, Someliz; Wheeler, Raymond

    2015-01-01

    Resource recovery and recycling waste streams to usable water via biological water processors is a plausible component of an integrated water purification system. Biological processing as a pretreatment can reduce the load of organic carbon and nitrogen compounds entering physiochemical systems downstream. Aerated hollow fiber membrane bioreactors, have been proposed and studied for a number of years as an approach for treating wastewater streams for space exploration.

  14. Optomechanical tests of hydrated biological tissues subjected to laser shaping

    SciTech Connect

    Omel'chenko, A I; Sobol', E N

    2008-03-31

    The mechanical properties of a matrix are studied upon changing the size and shape of biological tissues during dehydration caused by weak laser-induced heating. The cartilage deformation, dehydration dynamics, and hydraulic conductivity are measured upon laser heating. The hydrated state and the shape of samples of separated fascias and cartilaginous tissues were controlled by using computer-aided processing of tissue images in polarised light. (laser biology)

  15. Emerging measurement techniques for studies of mesoscopic superconductors.

    SciTech Connect

    Rydh, A.; Tagliati, S.; Nilsson, R. A.; Xie, R.; Pearson, J. E.; Welp, U.; Kwok, W. K.; Divan, R.

    2008-01-01

    Experimental research on mesoscopic systems puts high demands on the measurement infrastructure, including measurement system with associated sample preparation, experimental design, measurement electronics, and data collection. Successful experiments require both the ability to manufacture small samples and to successfully and accurately study their novel properties. Here, we discuss some aspects and recent advancements of general measurement techniques that should benefit several characterization methods such as thermodynamic, magnetic, and transport studies of mesoscopic superconductors.

  16. Vestigial Biological Structures: A Classroom-Applicable Test of Creationist Hypotheses

    ERIC Educational Resources Information Center

    Senter, Phil; Ambrocio, Zenis; Andrade, Julia B.; Foust, Katanya K.; Gaston, Jasmine E.; Lewis, Ryshonda P.; Liniewski, Rachel M.; Ragin, Bobby A.; Robinson, Khanna L.; Stanley, Shane G.

    2015-01-01

    Lists of vestigial biological structures in biology textbooks are so short that some young-Earth creationist authors claim that scientists have lost confidence in the existence of vestigial structures and can no longer identify any verifiable ones. We tested these hypotheses with a method that is easily adapted to biology classes. We used online…

  17. Broken detailed balance at mesoscopic scales in active biological systems.

    PubMed

    Battle, Christopher; Broedersz, Chase P; Fakhri, Nikta; Geyer, Veikko F; Howard, Jonathon; Schmidt, Christoph F; MacKintosh, Fred C

    2016-04-29

    Systems in thermodynamic equilibrium are not only characterized by time-independent macroscopic properties, but also satisfy the principle of detailed balance in the transitions between microscopic configurations. Living systems function out of equilibrium and are characterized by directed fluxes through chemical states, which violate detailed balance at the molecular scale. Here we introduce a method to probe for broken detailed balance and demonstrate how such nonequilibrium dynamics are manifest at the mesosopic scale. The periodic beating of an isolated flagellum from Chlamydomonas reinhardtii exhibits probability flux in the phase space of shapes. With a model, we show how the breaking of detailed balance can also be quantified in stationary, nonequilibrium stochastic systems in the absence of periodic motion. We further demonstrate such broken detailed balance in the nonperiodic fluctuations of primary cilia of epithelial cells. Our analysis provides a general tool to identify nonequilibrium dynamics in cells and tissues. PMID:27126047

  18. Video and HTML: Testing Online Tutorial Formats with Biology Students

    ERIC Educational Resources Information Center

    Craig, Cindy L.; Friehs, Curt G.

    2013-01-01

    This study compared two common types of online information literacy tutorials: a streaming media tutorial using animation and narration and a text-based tutorial with static images. Nine sections of an undergraduate biology lab class (234 students total) were instructed by a librarian on how to use the BIOSIS Previews database. Three sections…

  19. Photon-assisted tunneling through mesoscopic systems

    NASA Astrophysics Data System (ADS)

    Niu, Cheng

    2000-11-01

    In this thesis, we present a systematic study of the photon-assisted tunneling (PAT) through a mesoscopic structure, such as quantum well, quantum wire or quantum dot. The main objective is to fully understand the effect of the time-coherence electron-photon interaction on the spatial-coherence electronic tunneling. The concept of PAT is originated from Tien and Gordon, who invested the electron tunneling in superconductor junctions by absorbing a number of photons. Theoretically, Wingreen and co-workers present formalism for time-dependent coherent tunneling assuming single electronic level in the mesoscopic structures. We are the first group to investigate coherent transport with the intra-subband transition included. A complete numerical solution is presented for a Hamiltonian describing a two-level atom coherently coupling with both external time-dependant field and reservoirs. From such a solution, we clarified many aspects of electon-photon interaction that were unclear and have yielded new information about the effect of spatial coherence and confinement on the electron-photon interaction. We also derived the Coulomb blockade model including an external photon field. Based on this model, the PAT in quantum dot system with strong intra-dot electron-electron interaction is investigated. Under such situation, the external light field may modify the intra-dot electron distribution, and indirectly modify the tunneling property. Most works studying PAT model the photon field as a classical time-dependant function for its computational feasibility. However, the interaction of electrons with the vacuum fluctuation may change the electronic density of states if electron-photon interaction is not in the weak limit. We studied the PAT using a quantum electrodynamic (QED) description of photons. The QED result shows enhance effect of electron-photon interaction. The non-equilibrium Green function (GF) is originated from Schwinger's time-loop technique, and its

  20. Memory effects and mesoscopic quantum transport

    NASA Astrophysics Data System (ADS)

    Knezevic, Irena

    The active region of a mesoscopic structure or a modern semiconductor device needs to be treated as a dynamically open many-body system, exchanging information and particles with the contacts. The feedback from the active region to the contacts cannot be neglected, especially during the transient regime, because, due to the small size, both the active region and the contacts contain a small number of electrons. In this work, a rigorous theoretical approach for treating mesoscopic electronic systems as open many-body systems is developed. It is based on the partial-trace-free (PTF) approach that has provided a new outlook on the evolution of the reduced density matrix of an open system, and enabled several lines of research, which are presented in this work. First, an effective, memory-containing interaction was recognized in the equations of motion for the representation submatrices of the evolution operator (these submatrices are written in a special basis, adapted for the PTF approach, in the Liouville space of the composite closed system). The memory dressing, a quantity that separates the effective from the physical interaction, was identified. It obeys a self-contained nonlinear equation of motion (the Riccati matrix equation), whose solution can be represented in a diagrammatic fashion and enables physical approximations beyond the weak coupling limit. On the other hand, a foundation for the generalization of nonequilibrium Green's functions to open systems was laid. Two-time correlation functions were generalized, and evolution in both the transient and the steady-state regime was discussed. Based on the PTF approach, a second-order master equation of motion was derived for the reduced density matrix of the active region of a real electronic system: a resonant-tunneling diode (RTD). This equation incorporates the exchange of information and particles between the active region and the contacts, while being computationally tractable. The master equation was

  1. Persisting Misconceptions: Using Pre- and Post-Tests to Identify Biological Misconceptions.

    ERIC Educational Resources Information Center

    Nazario, Gladys M.; Burrowes, Patricia A.; Rodriguez, Julio

    2002-01-01

    Explains a research project conducted at the University of Puerto Rico among students taking biology to develop and test a constructivist learning environment and identify students' misconceptions in biology. Lists the questions on which students showed misconceptions during the pre- and post-tests. (Contains 27 references.) (YDS)

  2. Mesoscopic hydrothermodynamics of complex-structured materials.

    PubMed

    Vasconcellos, Áurea R; Silva, A A P; Luzzi, Roberto; Casas-Vázquez, J; Jou, David

    2013-10-01

    Some experimental results in the study of disordered systems, polymeric fluids, solutions of micelles and surfactants, ionic-glass conductors, and others show a hydrodynamic behavior labeled "anomalous" with properties described by some kind of fractional power laws in place of the standard ones. This is a consequence of the fractal-like structure that is present in these systems of which we do not have a detailed description, thus impairing the application of the conventional ensemble formalism of statistical mechanics. In order to obtain a physical picture of the phenomenon for making predictions which may help with technological and industrial decisions, one may resort to different styles (so-called nonconventional) in statistical mechanics. In that way can be introduced a theory for handling such impaired situations, a nonconventional mesoscopic hydrothermodynamics (MHT). We illustrate the question presenting an application in a contracted description of such nonconventional MHT, consisting in the use of the Renyi approach to derive a set of coupled nonstandard evolution equations, one for the density, a nonconventional Maxwell-Cattaneo equation, which in a limiting case goes over a non-Fickian diffusion equation, and other for the velocity in fluids under forced flow. For illustration the theory is applied to the study of the hydrodynamic motion in several soft-matter systems under several conditions such as streaming flow appearing in electrophoretic techniques and flow generated by harmonic forces arising in optical traps. The equivalence with Lévy processes is discussed and comparison with experiment is done. PMID:24229119

  3. Mesoscopic magnetomechanical hysteresis in a magnetorheological elastomer.

    PubMed

    Biller, A M; Stolbov, O V; Raikher, Yu L

    2015-08-01

    Field-induced magnetostatic interaction in a pair of identical particles made of a magnetically soft ferromagnet is studied. It is shown that due to saturation of the ferromagnet magnetization, this case differs significantly from the (super)paramagnetic one. A numerical solution is given, discussed, and compared with that provided by a simpler model (nonlinear mutual dipoles). We show that for multidomain ferromagnetic particles embedded in an elastomer matrix, as for paramagnetic ones in the same environment, pair clusters may form or break by a hysteresis scenario. However, the magnetization saturation brings in important features to this effect. First, the bistability state and the hysteresis take place only in a limited region of the material parameters of the system. Second, along with the hysteresis jumps occurring under the sole influence of the field, the "latent" hysteresis is possible which realizes only if the action of the field is combined with some additional (nonmagnetic) external factor. The obtained conditions, when used to assess the possibility of clustering in real magnetorheological polymers, infer an important role of mesoscopic magnetomechanical hysteresis for the macroscopic properties of these composites.

  4. Mesoscopic quantum multiplex for channeling bunches

    NASA Astrophysics Data System (ADS)

    Shen, Jing

    1998-09-01

    (1) Bogacz-Cline channeling is an interesting idea that can transform a bunch of low particle intensity to a collider of high luminosity but it was maintained as impossible to carry out because of three technical problems. (2) The first of which is discussed in this paper, and it is how to get billions particles from each bunch to enter into and channel through a single crystal channel. (3) Two basic difficulties of entrance are discussed in this paper. The first is due to the Heisenberg's uncertainty, and the second is the dimension reduction of a beam bunch in crystal from 3D to 1D. (4) To overcome these difficulties, a hybrid device named Mesoscopic Quantum Multiplex (MQM) is designed to achieve entrance and channeling. It is a quantum generalization of classical multiplex in detector readout electronics for the classical-quantum interface. It is made by nano-crystalline technology. (5) The MQM can channel the Richter-Kimura-Takada flat e± beams of NLC-JLC, and low emittance p or heavy ion beams as well as the Bogacz-Cline μ± beams, and the Nagamine-Chu cool μ± beams.

  5. Quantum Mesoscopic Physics of Electrons and Photons

    NASA Astrophysics Data System (ADS)

    Akkermans, Eric

    2013-03-01

    We first review basic notions of coherent quantum transport at the mesoscopic scale for both electronic and photonic systems. We then show that successful descriptions developed for coherent electronic transport (e.g. weak localization and UCF) and thermodynamics (persistent currents), noise and full counting statistics can be extended and applied to the study of Quantum Electrodynamics of quantum conductors and of quantum optics based on photons emitted by such conductors. In this context, we discuss the two following specific problems : (1) Ramsey fringes and time domain interference for particle creation form a quantum vacuum with a specific application to dynamical Coulomb blockade. In that setup, the current noise of a coherent conductor is biased by two successive voltage pulses. An interference pattern between photon assisted processes is observed which is explained by the contribution of several processes to the probability to emit photons after each pulse. Recent experiments in this context will be discussed. (2) Quantum emitter coupled to a fractal environment. A new and unexpected type of oscillatory structures for the probability of spontaneous emission has been obtained which results from the fractal nature of the quantum vacuum. When applied to the case of a tunnel junction as a quantum emitter of photons, the same oscillatory structure arises for the conductance of the tunnel junction. This work was supported by the Israel Science Foundation Grant No.924/09

  6. Vortex matter driven through mesoscopic channels

    NASA Astrophysics Data System (ADS)

    Kes, P. H.; Kokubo, N.; Besseling, R.

    2004-08-01

    The dynamics of vortex matter confined to mesoscopic channels has been investigated by means of mode locking experiments. When vortices are coherently driven through the potential provided by static vortices pinned in the channel edges, interference between the washboard frequency of the moving vortex lattice and the frequency of the superimposed rf-drive causes (Shapiro-like) steps in the dc- I- V curves. The position of the voltage steps uniquely determines the number of moving rows in each channel. It also shows how the frustration between row spacing and channel width behaves as a function of magnetic field. Maxima in flow stress (∼ Ic) occur at mismatch conditions. They are related to the traffic-jam-like flow impedance caused by the disorder in the edges. At higher fields, near the 2D-melting line Bm( T), the mode-locking interference characteristic for crystalline motion, strongly depends on the velocity, i.e. the applied frequency at which the vortex motion is probed. The minimum velocity at which coherent motion could be observed, diverges when the melting line is approached from below. Above the melting line interference is absent for any frequency. These observations give the first direct evidence for a dynamic phase transition of vortex matter driven through a disorder potential as predicted by Koshelev and Vinokur.

  7. Biologically Relevant Exposure Science for 21st Century Toxicity Testing

    EPA Science Inventory

    High visibility efforts in toxicity testing and computational toxicology including the recent NRC report, Toxicity Testing in the 21st Century: a Vision and Strategy (NRC, 2007), raise important research questions and opportunities for the field of exposure science. The authors ...

  8. Testing systems for biologic markers of genotoxic exposure and effect

    SciTech Connect

    Mendelsohn, M.L.

    1986-11-19

    Societal interest in genotoxicity stems from two concerns: the fear of carcinogenesis secondary to somatic mutation; and the fear of birth defects and decreasing genetic fitness secondary to heritable mutation. There is a pressing need to identify agents that can cause these effects, to understand the underlying dose-response relationships, to identify exposed populations, and to estimate both the magnitude of exposure and the risk of adverse health effects in such populations. Biologic markers refer either to evidence in surrogate organisms, or to the expressions of exposure and effect in human populations. 21 refs.

  9. LASER BIOLOGY: Optomechanical tests of hydrated biological tissues subjected to laser shaping

    NASA Astrophysics Data System (ADS)

    Omel'chenko, A. I.; Sobol', E. N.

    2008-03-01

    The mechanical properties of a matrix are studied upon changing the size and shape of biological tissues during dehydration caused by weak laser-induced heating. The cartilage deformation, dehydration dynamics, and hydraulic conductivity are measured upon laser heating. The hydrated state and the shape of samples of separated fascias and cartilaginous tissues were controlled by using computer-aided processing of tissue images in polarised light.

  10. Reaction times to weak test lights. [psychophysics biological model

    NASA Technical Reports Server (NTRS)

    Wandell, B. A.; Ahumada, P.; Welsh, D.

    1984-01-01

    Maloney and Wandell (1984) describe a model of the response of a single visual channel to weak test lights. The initial channel response is a linearly filtered version of the stimulus. The filter output is randomly sampled over time. Each time a sample occurs there is some probability increasing with the magnitude of the sampled response - that a discrete detection event is generated. Maloney and Wandell derive the statistics of the detection events. In this paper a test is conducted of the hypothesis that the reaction time responses to the presence of a weak test light are initiated at the first detection event. This makes it possible to extend the application of the model to lights that are slightly above threshold, but still within the linear operating range of the visual system. A parameter-free prediction of the model proposed by Maloney and Wandell for lights detected by this statistic is tested. The data are in agreement with the prediction.

  11. Mesoscopic spin Hall effect in semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Zarbo, Liviu

    The spin Hall effect (SHE) is a name given to a collection of diverse phenomena which share two principal features: (i) longitudinal electric current flowing through a paramagnetic semiconductor or metallic sample leads to transverse spin current and spin accumulation of opposite sign at opposing lateral edges; (ii) SHE does not require externally applied magnetic field or magnetic ordering in the equilibrium state of the sample, instead it relies on the presence of spin-orbit (SO) couplings within the sample. This thesis elaborates on a new type of phenomenon within the SHE family, predicted in our recent studies [Phys. Rev. B 72, 075361 (2005); Phys. Rev. Lett. 95, 046601 (2005); Phys. Rev. B 72, 075335 (2005); Phys. Rev. B 73 , 075303 (2006); and Europhys. Lett. 77, 47004 (2007)], where pure spin current flows through the transverse electrodes attached to a clean finitesize two-dimensional electron gas (2DEG) due to unpolarized charge current injected through its longitudinal leads. If transverse leads are removed, the effect manifests as nonequilibrium spin Hall accumulation at the lateral edges of 2DEG wires. The SO coupling driving this SHE effect is of the Rashba type, which arises due to structural inversion asymmetry of semiconductor heterostructure hosting the 2DEG. We term the effect "mesoscopic" because the spin Hall currents and accumulations reach optimal value in samples of the size of the spin precession length---the distance over which the spin of an electron precesses by an angle pi. In strongly SO-coupled structures this scale is of the order of ˜100 nm, and, therefore, mesoscopic in the sense of being much larger than the characteristic microscopic scales (such as the Fermi wavelength, screening length, or the mean free path in disordered systems), but still much smaller than the macroscopic ones. Although the first theoretical proposal for SHE, driven by asymmetry in SO-dependent scattering of spin-up and spin-down electrons off impurities

  12. Multi-dimensional, mesoscopic Monte Carlo simulations of inhomogeneous reaction-drift-diffusion systems on graphics-processing units.

    PubMed

    Vigelius, Matthias; Meyer, Bernd

    2012-01-01

    For many biological applications, a macroscopic (deterministic) treatment of reaction-drift-diffusion systems is insufficient. Instead, one has to properly handle the stochastic nature of the problem and generate true sample paths of the underlying probability distribution. Unfortunately, stochastic algorithms are computationally expensive and, in most cases, the large number of participating particles renders the relevant parameter regimes inaccessible. In an attempt to address this problem we present a genuine stochastic, multi-dimensional algorithm that solves the inhomogeneous, non-linear, drift-diffusion problem on a mesoscopic level. Our method improves on existing implementations in being multi-dimensional and handling inhomogeneous drift and diffusion. The algorithm is well suited for an implementation on data-parallel hardware architectures such as general-purpose graphics processing units (GPUs). We integrate the method into an operator-splitting approach that decouples chemical reactions from the spatial evolution. We demonstrate the validity and applicability of our algorithm with a comprehensive suite of standard test problems that also serve to quantify the numerical accuracy of the method. We provide a freely available, fully functional GPU implementation. Integration into Inchman, a user-friendly web service, that allows researchers to perform parallel simulations of reaction-drift-diffusion systems on GPU clusters is underway.

  13. Electronic transmittance phase extracted from mesoscopic interferometers

    PubMed Central

    2012-01-01

    The usual experimental set-up for measuring the wave function phase shift of electrons tunneling through a quantum dot (QD) embedded in a ring (i.e., the transmittance phase) is the so-called ‘open’ interferometer as first proposed by Schuster et al. in 1997, in which the electrons back-scattered at source and the drain contacts are absorbed by additional leads in order to exclude multiple interference. While in this case one can conveniently use a simple two-path interference formula to extract the QD transmittance phase, the open interferometer has also a number of draw-backs, such as a reduced signal and some uncertainty regarding the effects of the extra leads. Here we present a meaningful theoretical study of the QD transmittance phase in ‘closed’ interferometers (i.e., connected only to source and drain leads). By putting together data from existing literature and giving some new proofs, we show both analytically and by numerical simulations that the existence of phase lapses between consecutive resonances of the ‘bare’ QD is related to the signs of the corresponding Fano parameters - of the QD + ring system. More precisely, if the Fano parameters have the same sign, the transmittance phase of the QD exhibits a Π lapse. Therefore, closed mesoscopic interferometers can be used to address the ‘universal phase lapse’ problem. Moreover, the data from already existing Fano interference experiments from Kobayashi et al. in 2003 can be used to infer the phase lapses. PMID:23061877

  14. Speed limit to the Abrikosov lattice in mesoscopic superconductors

    NASA Astrophysics Data System (ADS)

    Grimaldi, G.; Leo, A.; Sabatino, P.; Carapella, G.; Nigro, A.; Pace, S.; Moshchalkov, V. V.; Silhanek, A. V.

    2015-07-01

    We study the instability of the superconducting state in a mesoscopic geometry for the low pinning material Mo3Ge characterized by a large Ginzburg-Landau parameter. We observe that in the current-driven switching to the normal state from a nonlinear region of the Abrikosov flux flow, the mean critical vortex velocity reaches a limiting maximum velocity as a function of the applied magnetic field. Based on time-dependent Ginzburg-Landau simulations, we argue that the observed behavior is due to the high-velocity vortex dynamics confined on a mesoscopic scale. We build up a general phase diagram which includes all possible dynamic configurations of the Abrikosov lattice in a mesoscopic superconductor.

  15. Australian Biology Test Item Bank, Years 11 and 12. Volume II: Year 12.

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Sewell, Jeffrey J., Ed.

    This document consists of test items which are applicable to biology courses throughout Australia (irrespective of course materials used); assess key concepts within course statement (for both core and optional studies); assess a wide range of cognitive processes; and are relevant to current biological concepts. These items are arranged under…

  16. A Knowledge Base for Teaching Biology Situated in the Context of Genetic Testing

    ERIC Educational Resources Information Center

    van der Zande, Paul; Waarlo, Arend Jan; Brekelmans, Mieke; Akkerman, Sanne F.; Vermunt, Jan D.

    2011-01-01

    Recent developments in the field of genomics will impact the daily practice of biology teachers who teach genetics in secondary education. This study reports on the first results of a research project aimed at enhancing biology teacher knowledge for teaching genetics in the context of genetic testing. The increasing body of scientific knowledge…

  17. Expertise for Teaching Biology Situated in the Context of Genetic Testing

    ERIC Educational Resources Information Center

    van der Zande, Paul; Akkerman, Sanne F.; Brekelmans, Mieke; Waarlo, Arend Jan; Vermunt, Jan D.

    2012-01-01

    Contemporary genomics research will impact the daily practice of biology teachers who want to teach up-to-date genetics in secondary education. This article reports on a research project aimed at enhancing biology teachers' expertise for teaching genetics situated in the context of genetic testing. The increasing body of scientific knowledge…

  18. Energy distribution in quantized mesoscopic RLC electric circuit

    NASA Astrophysics Data System (ADS)

    Wu, Wei-Feng; Fan, Hong-Yi

    2016-09-01

    Quantum information processing experimentally depends on optical-electronic devices. In this paper, we consider quantized mesoscopic RLC (resistance, inductance and capacitance) electric circuit in stable case as a quantum statistical ensemble, and calculate energy distribution (i.e. the energy stored in inductance and capacitance as well as the energy consumed on the resistance). For this aim, we employ the technique of integration within ordered product (IWOP) of operator to derive the thermo-vacuum state for this mesoscopic system, with which ensemble average energy calculation is replaced by evaluating expected value in pure state. This approach is concise and the result we deduced is physically appealling.

  19. CHAIRMEN'S FOREWORD: The Seventh International Conference on New Phenomena in Mesoscopic Structures & The Fifth International Conference on Surfaces and Interfaces of Mesoscopic Devices

    NASA Astrophysics Data System (ADS)

    Aoyagi, Yoshinobu; Goodnick, Stephen M.

    2006-05-01

    , non-equilibrium transport, instabilities, nano-electro-mechanical systems, mesoscopic Josephson effects, phase coherence and breaking, and the Kondo effect •Systems of nanodevices: Quantum cellular automata, systolic SET processors, quantum neural nets, adaptive effects in circuits, and molecular circuits •Nanomaterials: nanotubes, nanowires, organic and molecular materials, self-assembled nano wires, and organic devices •Nanobioelectronics: electronic properties of biological structures on the nanoscale. This year's conference was organized by Prof Stephen Goodnick, Arizona State University, and Prof Yoshinobu Aoyagi, Tokyo Institute of Technology. The conference benefited from 14 invited speakers, whose topics spanned the above list, and a total of 97 registered attendees. The largest contingent was from Japan, followed closely by the US. In total, there were 49 from Japan, 31 fiom the US, and 17 from Europe. The organizers want to especially thank the sponsors for the meeting: The Office of Naval Research, the Army Research Office, and Arizona State University on the US side, and the Japan Society for the Promotion of Science, through their 151 Committee, on the Japanese side. PROGRAM COMMITTEE •Prof Gerhard Abstreiter, Technical University of Munich •Prof Tsuneya Ando, Tokyo Institute of Technology •Prof John Barker, University of Glasgow •Prof Jonathan Bird, the University at Buffalo •Prof Robert Blick, University of Wisconsin •Prof David Ferry, Chair, Arizona State University •Dr Yoshiro Hirayama, NTT Basic Research Laboratories •Dr Koji Ishibashi, RIKEN •Prof Carlo Jacoboni, University of Modena •Prof David Janes, Purdue University •Prof Friedl Kuchar, University of Leoben •Prof K. Matsumoto, Osaka University •Prof Wolfgang Porod, Notre Dame University •Prof Michiharu Tabe, Shizuoka University •Prof Joachim Wolter, Eindhoven Institute of Technology •Prof Lukas Worschech, University of Würzburg •Dr Naoki Yokoyama, Fujitsu

  20. Cosmo Cassette: A Microfluidic Microgravity Microbial System For Synthetic Biology Unit Tests and Satellite Missions

    NASA Technical Reports Server (NTRS)

    Berliner, Aaron J.

    2013-01-01

    Although methods in the design-build-test life cycle of the synthetic biology field have grown rapidly, the expansion has been non-uniform. The design and build stages in development have seen innovations in the form of biological CAD and more efficient means for building DNA, RNA, and other biological constructs. The testing phase of the cycle remains in need of innovation. Presented will be both a theoretical abstraction of biological measurement and a practical demonstration of a microfluidics-based platform for characterizing synthetic biological phenomena. Such a platform demonstrates a design of additive manufacturing (3D printing) for construction of a microbial fuel cell (MFC) to be used in experiments carried out in space. First, the biocompatibility of the polypropylene chassis will be demonstrated. The novel MFCs will be cheaper, and faster to make and iterate through designs. The novel design will contain a manifold switchingdistribution system and an integrated in-chip set of reagent reservoirs fabricated via 3D printing. The automated nature of the 3D printing yields itself to higher resolution switching valves and leads to smaller sized payloads, lower cost, reduced power and a standardized platform for synthetic biology unit tests on Earth and in space. It will be demonstrated that the application of unit testing in synthetic biology will lead to the automatic construction and validation of desired constructs. Unit testing methodologies offer benefits of preemptive problem identification, change of facility, simplicity of integration, ease of documentation, and separation of interface from implementation, and automated design.

  1. Generalized correlation functions for conductance fluctuations and the mesoscopic spin Hall effect

    NASA Astrophysics Data System (ADS)

    Ramos, J. G. G. S.; Barbosa, A. L. R.; Bazeia, D.; Hussein, M. S.; Lewenkopf, C. H.

    2012-12-01

    We study the spin Hall conductance fluctuations in ballistic mesoscopic systems. We obtain universal expressions for the spin and charge current fluctuations, cast in terms of current-current autocorrelation functions. We show that the latter are conveniently parametrized as deformed Lorentzian shape lines, functions of an external applied magnetic field and the Fermi energy. We find that the charge current fluctuations show quite unique statistical features at the symplectic-unitary crossover regime. Our findings are based on an evaluation of the generalized transmission coefficients correlation functions within the stub model and are amenable to experimental test.

  2. Modeling the Drug Discovery Process: The Isolation and Biological Testing of Eugenol from Clove Oil

    NASA Astrophysics Data System (ADS)

    Miles, William H.; Smiley, Patricia M.

    2002-01-01

    This experiment describes the isolation and biological testing of eugenol and neutral compounds from commercially available clove oil. By coupling the chemical separation of the components of clove oil (an experiment described in many introductory organic laboratory textbooks) with a simple antibiotic test, the students "discover" the biologically active compound in clove oil. This experiment models one of the primary methods used in the discovery of new pharmaceutical agents.

  3. High-resolution mesoscopic fluorescence molecular tomography based on compressive sensing.

    PubMed

    Yang, Fugang; Ozturk, Mehmet S; Zhao, Lingling; Cong, Wenxiang; Wang, Ge; Intes, Xavier

    2015-01-01

    Mesoscopic fluorescence molecular tomography (MFMT) is new imaging modality aiming at 3-D imaging of molecular probes in a few millimeter thick biological samples with high-spatial resolution. In this paper, we develop a compressive sensing-based reconstruction method with l1-norm regularization for MFMT with the goal of improving spatial resolution and stability of the optical inverse problem. Three-dimensional numerical simulations of anatomically accurate microvasculature and real data obtained from phantom experiments are employed to evaluate the merits of the proposed method. Experimental results show that the proposed method can achieve 80 μm spatial resolution for a biological sample of 3 mm thickness and more accurate quantifications of concentrations and locations for the fluorophore distribution than those of the conventional methods.

  4. Dormancy and Recovery Testing for Biological Wastewater Processors

    NASA Technical Reports Server (NTRS)

    Hummerick, Mary E.; Coutts, Janelle L.; Lunn, Griffin M.; Spencer, LaShelle; Khodadad, Christina L.; Frances, Someliz; Wheller, Raymond

    2015-01-01

    Bioreactors, such as aerated membrane type bioreactors have been proposed and studied for a number of years as an alternate approach for treating wastewater streams for space exploration. Several challenges remain before these types of bioreactors can be used in space settings, including transporting the bioreactors with their microbial communities to space, whether that be the International Space Station or beyond, or procedures for safing the systems and placing them into dormant state for later start-up. Little information is available on such operations as it is not common practice for terrestrial systems. This study explored several dormancy processes for established bioreactors to determine optimal storage and recovery conditions. Procedures focused on complete isolation of the microbial communities from an operational standpoint and observing the effects of: 1) storage temperature, and 2) storage with or without the reactor bulk fluid. The first consideration was tested from a microbial integrity and power consumption standpoint; both room temperature (25 C) and cold (4 C) storage conditions were studied. The second consideration was explored; again, for microbial integrity as well as plausible real-world scenarios of how terrestrially established bioreactors would be transported to microgravity and stored for periods of time between operations. Biofilms were stored without the reactor bulk fluid to simulate transport of established biofilms into microgravity, while biofilms stored with the reactor bulk fluid simulated the most simplistic storage condition to implement operations for extended periods of nonuse. Dormancy condition did not have an influence on recovery in initial studies with immature biofilms (48 days old), however, a lengthy recovery time was required (20+ days). Bioreactors with fully established biofilms (13 months) were able to recover from a 7-month dormancy period to steady state operation within 4 days (approximately 1 residence cycle

  5. Dormancy and Recovery Testing for Biological Wastewater Processors

    NASA Technical Reports Server (NTRS)

    Hummerick, Mary E.; Coutts, Janelle L.; Lunn, Griffin M.; Spencer, LaShelle; Khodadad, Christina L.; Birmele, Michele N.; Frances, Someliz; Wheeler, Raymond

    2015-01-01

    Bioreactors, such as the aerated hollow fiber membrane type, have been proposed and studied for a number of years as an alternate approach for treating wastewater streams for space exploration. Several challenges remain to be resolved before these types of bioreactors can be used in space settings, including transporting the bioreactors with intact and active biofilms, whether that be to the International Space Station or beyond, or procedures for safing the systems and placing them into a dormant state for later start-up. Little information is available on such operations as it is not common practice for terrestrial systems. This study explored several dormancy processes for established bioreactors to determine optimal storage and recovery conditions. Procedures focused on complete isolation of the microbial communities from an operational standpoint and observing the effects of: 1) storage temperature, and 2) storage with or without the reactor bulk fluid. The first consideration was tested from a microbial integrity and power consumption standpoint; both ambient temperature (25 C) and cold (4 C) storage conditions were studied. The second consideration was explored; again, for microbial integrity as well as plausible real-world scenarios of how terrestrially established bioreactors would be transported to microgravity and stored for periods of time between operations. Biofilms were stored without the reactor bulk fluid to simulate transport of established biofilms into microgravity, while biofilms stored with the reactor bulk fluid simulated the most simplistic storage condition to implement operations for extended periods of nonuse. Dormancy condition did not have an influence on recovery in initial studies with immature biofilms (48 days old), however a lengthy recovery time was required (20+ days). Bioreactors with fully established biofilms (13 months) were able to recover from a 7-month dormancy period to steady state operation within 4 days (approx. 1

  6. Mesoscopic structures reveal the network between the layers of multiplex data sets

    NASA Astrophysics Data System (ADS)

    Iacovacci, Jacopo; Wu, Zhihao; Bianconi, Ginestra

    2015-10-01

    Multiplex networks describe a large variety of complex systems, whose elements (nodes) can be connected by different types of interactions forming different layers (networks) of the multiplex. Multiplex networks include social networks, transportation networks, or biological networks in the cell or in the brain. Extracting relevant information from these networks is of crucial importance for solving challenging inference problems and for characterizing the multiplex networks microscopic and mesoscopic structure. Here we propose an information theory method to extract the network between the layers of multiplex data sets, forming a "network of networks." We build an indicator function, based on the entropy of network ensembles, to characterize the mesoscopic similarities between the layers of a multiplex network, and we use clustering techniques to characterize the communities present in this network of networks. We apply the proposed method to study the Multiplex Collaboration Network formed by scientists collaborating on different subjects and publishing in the American Physical Society journals. The analysis of this data set reveals the interplay between the collaboration networks and the organization of knowledge in physics.

  7. Transport dissipative particle dynamics model for mesoscopic advection- diffusion-reaction problems

    SciTech Connect

    Zhen, Li; Yazdani, Alireza; Tartakovsky, Alexandre M.; Karniadakis, George E.

    2015-07-07

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic DPD framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between particles, and an analytical formula is proposed to relate the mesoscopic concentration friction to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.

  8. Mesoscopic structures reveal the network between the layers of multiplex data sets.

    PubMed

    Iacovacci, Jacopo; Wu, Zhihao; Bianconi, Ginestra

    2015-10-01

    Multiplex networks describe a large variety of complex systems, whose elements (nodes) can be connected by different types of interactions forming different layers (networks) of the multiplex. Multiplex networks include social networks, transportation networks, or biological networks in the cell or in the brain. Extracting relevant information from these networks is of crucial importance for solving challenging inference problems and for characterizing the multiplex networks microscopic and mesoscopic structure. Here we propose an information theory method to extract the network between the layers of multiplex data sets, forming a "network of networks." We build an indicator function, based on the entropy of network ensembles, to characterize the mesoscopic similarities between the layers of a multiplex network, and we use clustering techniques to characterize the communities present in this network of networks. We apply the proposed method to study the Multiplex Collaboration Network formed by scientists collaborating on different subjects and publishing in the American Physical Society journals. The analysis of this data set reveals the interplay between the collaboration networks and the organization of knowledge in physics.

  9. Using biological data to test climate change refugia

    NASA Astrophysics Data System (ADS)

    Morelli, T. L.; Maher, S. P.

    2015-12-01

    The concept of refugia has been discussed from theoretical and paleontological perspectives to address how populations persisted during periods of unfavorable climate. Recently, several studies have applied the idea to contemporary landscapes to identify locations that are buffered from climate change effects so as to favor greater persistence of valued resources relative to other areas. Refugia are now being discussed among natural resource agencies as a potential adaptation option in the face of anthropogenic climate change. Using downscaled climate data, we identified hypothetical refugial meadows in the Sierra Nevada and then tested them using survey and genetic data from Belding's ground squirrel (Urocitellus beldingi) populations. We predicted that refugial meadows would show higher genetic diversity, higher rates of occupancy and lower rates of extirpation over time. At each step of the research, we worked with managers to ensure the largest impact. Although no panacea, identifying climate change refugia could be an important strategy for prioritizing habitats for management intervention in order to conserve populations. This research was supported by the California LCC, the Northeast Climate Science Center, and NSF.

  10. Mesoscopic faults in the Bregaglia (Bergell) massif, Central Alps

    NASA Astrophysics Data System (ADS)

    Passerini, P.; Sguazzoni, G.; Marcucci, M.

    1991-11-01

    The strike, direction of dip and pitch of the striae along mesoscopic faults in the Oligocene granodiorite-tonalite of Val Masino-Val Bregaglia (Bergell) are analysed. Most fault planes are steeply dipping, and show strike-slip or oblique-slip motion. Dominant strikes are NNW or NNE. A relative chronology of fault sets is suggested based on the presence of different minerals (chlorite and epidote) on fault planes. The pattern of mesoscopic faults in the Val Masino-Val Bregaglia massif does not follow the earlier tectonic trends of the Pennidic nappe edifice, nor even the trend of the nearby section of the Insubric Line considered at both regional and mesoscopic scales. The mesoscopic analysis of the Val Masino-Val Bregaglia massif thus reveals a fault system largely oblique to the major Alpine lineaments. The observed fault pattern does not reveal traces of thrusting referable to late Alpine orogenic phases, and can be related to subsequent deformation, dominated by strike-slip movements; this pattern does not match the traditional schemes of extensional dip-slip faulting following orogenesis. It records a stage of tectonic evolution which follows nappe emplacement, yet it precedes vertical or extensional post-orogenic tectonics.

  11. Quality in molecular biology testing for inherited thrombophilia disorders.

    PubMed

    Cooper, Peter C; Goodeve, Anne C; Beauchamp, Nicholas J

    2012-09-01

    As the understanding of the genetic basis of the inherited thrombophilias has increased over recent years, their routine diagnostic genetic analysis has also matured. This review considers methods used to test for the factor V (F5) Leiden mutation and prothrombin 20210A (F2 c.*97G>A) allele, and analysis of the SERPINC1, PROC, and PROS1 genes in cases of antithrombin, protein C (PC), and protein S (PS) deficiency, respectively. Issues relating to quality are explored, highlighting where analytical and sample handling errors may occur. Detection of the factor V Leiden mutation and the prothrombin c.*97G>A allele are best performed using real-time polymerase chain reaction analysis as this relatively simple technique allows their discrimination from rare variants of neighboring nucleotides; not possible using the more time-consuming restriction digestion assays. With the advent of low-cost and high-throughput sequence analysis, direct sequencing has become the first-line method to provide a definitive diagnosis of inherited, rather than acquired, deficiencies. Large cohort studies have shown that antithrombin and PC mutations are identified in between 61 and 87% of patients, whereas the detection rate in PS deficiency is substantially lower in around 40% of patients. Large gene deletions make up between 7 and 10% of PS and antithrombin mutations and only 1% of PC mutations, but it is suggested that dosage analysis techniques such as multiplex ligation-dependent probe amplification should be used for all three genes as part of routine analysis to ensure mutations are not missed. Best practice guidelines are available from EuroGentest covering a wide variety of the issues raised in this review and all laboratories should participate in appropriate external quality assurance schemes to ensure they continue to offer high quality service.

  12. Testing with Feedback Yields Potent, but Piecewise, Learning of History and Biology Facts

    ERIC Educational Resources Information Center

    Pan, Steven C.; Gopal, Arpita; Rickard, Timothy C.

    2016-01-01

    Does correctly answering a test question about a multiterm fact enhance memory for the entire fact? We explored that issue in 4 experiments. Subjects first studied Advanced Placement History or Biology facts. Half of those facts were then restudied, whereas the remainder were tested using "5 W" (i.e., "who, what, when, where",…

  13. Collaborative Testing Improves Performance but Not Content Retention in a Large-Enrollment Introductory Biology Class

    ERIC Educational Resources Information Center

    Leight, Hayley; Saunders, Cheston; Calkins, Robin; Withers, Michelle

    2012-01-01

    Collaborative testing has been shown to improve performance but not always content retention. In this study, we investigated whether collaborative testing could improve both performance and content retention in a large, introductory biology course. Students were semirandomly divided into two groups based on their performances on exam 1. Each group…

  14. 77 FR 22282 - Draft Guidelines on Biologics Quality Monitoring: Testing for the Detection of Mycoplasma...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-13

    ... Animal and Plant Health Inspection Service Draft Guidelines on Biologics Quality Monitoring: Testing for... master seed/cell testing in veterinary vaccines regulated by the Animal and Plant Health Inspection... veterinary vaccines regulated by the APHIS under the Virus-Serum-Toxin Act (VSTA), we are requesting...

  15. Effects of Scoring by Section and Independent Scorers' Patterns on Scorer Reliability in Biology Essay Tests

    ERIC Educational Resources Information Center

    Ebuoh, Casmir N.; Ezeudu, S. A.

    2015-01-01

    The study investigated the effects of scoring by section, use of independent scorers and conventional patterns on scorer reliability in Biology essay tests. It was revealed from literature review that conventional pattern of scoring all items at a time in essay tests had been criticized for not being reliable. The study was true experimental study…

  16. A Computer-Aided Self-Testing System for Biological Psychology.

    ERIC Educational Resources Information Center

    Leiblum, M. D.; And Others

    1994-01-01

    Describes the production of a computer-aided, self-testing system for university students enrolled in a first-year course in biological psychology. Project aspects described include selection, acquisition and description of software; question banks and test structures; modes of use (computer or printed version); evaluation; and future plans. (11…

  17. Using Open-Book Tests to Strengthen the Study Skills of Community-College Biology Students

    ERIC Educational Resources Information Center

    Phillips, Gregory

    2006-01-01

    The author observed that students enrolled in first-year college biology courses often had weak study skills. This longitudinal study examined the use of open-book tests to encourage reading and to assess the improvement of college students' study skills. There was a statistically significant improvement from the initial test to the final test…

  18. Recent advances in sensitized mesoscopic solar cells.

    PubMed

    Grätzel, Michael

    2009-11-17

    -intensive high vacuum and materials purification steps that are currently employed in the fabrication of all other thin-film solar cells. Organic materials are abundantly available, so that the technology can be scaled up to the terawatt scale without running into feedstock supply problems. This gives organic-based solar cells an advantage over the two major competing thin-film photovoltaic devices, i.e., CdTe and CuIn(As)Se, which use highly toxic materials of low natural abundance. However, a drawback of the current embodiment of OPV cells is that their efficiency is significantly lower than that for single and multicrystalline silicon as well as CdTe and CuIn(As)Se cells. Also, polymer-based OPV cells are very sensitive to water and oxygen and, hence, need to be carefully sealed to avoid rapid degradation. The research discussed within the framework of this Account aims at identifying and providing solutions to the efficiency problems that the OPV field is still facing. The discussion focuses on mesoscopic solar cells, in particular, dye-sensitized solar cells (DSCs), which have been developed in our laboratory and remain the focus of our investigations. The efficiency problem is being tackled using molecular science and nanotechnology. The sensitizer constitutes the heart of the DSC, using sunlight to pump electrons from a lower to a higher energy level, generating in this fashion an electric potential difference, which can exploited to produce electric work. Currently, there is a quest for sensitizers that achieve effective harnessing of the red and near-IR part of sunlight, converting these photons to electricity better than the currently used generation of dyes. Progress in this area has been significant over the past few years, resulting in a boost in the conversion efficiency of the DSC that will be reviewed. PMID:19715294

  19. Establishing construct validity of the Biology I Subject Area Testing program in Mississippi

    NASA Astrophysics Data System (ADS)

    Philippoff, Christy Michelle Hollis

    Science education has undergone many revisions since it was permanently embedded in the country's educational curriculum at the end of the 19th century. Some of these revisions occurred as a direct result of the No Child Left Behind Act (NCLB). This legislation placed more accountability on schools than ever before by requiring that all students pass a series of standardized tests (USDE, 2010). High schools in Mississippi require four areas of standardized testing: English II, Algebra I, U.S. History, and Biology I (Wroten, 2008). The focus of this study is the Biology I Subject Area Test. In an effort to determine the validity of that test, this study explores the importance of the Mississippi Biology I content standards according to the importance ratings and frequency of use ratings by science professionals in Mississippi. The science professionals surveyed for this study were high school science teachers, college science professors and scientists in their professional settings. The science professionals' importance ratings were compared to the importance ratings placed on the content strands by the Mississippi Biology I Subject Area Test. To further determine the test's validity, it is also compared to the National Science Education Standards.

  20. A Knowledge Base for Teaching Biology Situated in the Context of Genetic Testing

    NASA Astrophysics Data System (ADS)

    van der Zande, Paul; Waarlo, Arend Jan; Brekelmans, Mieke; Akkerman, Sanne F.; Vermunt, Jan D.

    2011-10-01

    Recent developments in the field of genomics will impact the daily practice of biology teachers who teach genetics in secondary education. This study reports on the first results of a research project aimed at enhancing biology teacher knowledge for teaching genetics in the context of genetic testing. The increasing body of scientific knowledge concerning genetic testing and the related consequences for decision-making indicate the societal relevance of such a situated learning approach. What content knowledge do biology teachers need for teaching genetics in the personal health context of genetic testing? This study describes the required content knowledge by exploring the educational practice and clinical genetic practices. Nine experienced teachers and 12 respondents representing the clinical genetic practices (clients, medical professionals, and medical ethicists) were interviewed about the biological concepts and ethical, legal, and social aspects (ELSA) of testing they considered relevant to empowering students as future health care clients. The ELSA suggested by the respondents were complemented by suggestions found in the literature on genetic counselling. The findings revealed that the required teacher knowledge consists of multiple layers that are embedded in specific genetic test situations: on the one hand, the knowledge of concepts represented by the curricular framework and some additional concepts (e.g. multifactorial and polygenic disorder) and, on the other hand, more knowledge of ELSA and generic characteristics of genetic test practice (uncertainty, complexity, probability, and morality). Suggestions regarding how to translate these characteristics, concepts, and ELSA into context-based genetics education are discussed.

  1. An investigation on impacts of scheduling configurations on Mississippi biology subject area testing

    NASA Astrophysics Data System (ADS)

    Marchette, Frances Lenora

    The purpose of this mixed modal study was to compare the results of Biology Subject Area mean scores of students on a 4 x 4 block schedule, A/B block schedule, and traditional year-long schedule for 1A to 5A size schools. This study also reviewed the data to determine if minority or gender issues might influence the test results. Interviews with administrators and teachers were conducted about the type of schedule configuration they use and the influence that the schedule has on student academic performance on the Biology Subject Area Test. Additionally, this research further explored whether schedule configurations allow sufficient time for students to construct knowledge. This study is important to schools, teachers, and administrators because it can assist them in considering the impacts that different types of class schedules have on student performance and if ethnic or gender issues are influencing testing results. This study used the causal-comparative method for the quantitative portion of the study and constant comparative method for the qualitative portion to explore the relationship of school schedules on student academic achievement on the Mississippi Biology Subject Area Test. The aggregate means of selected student scores indicate that the Mississippi Biology Subject Area Test as a measure of student performance reveals no significant difference on student achievement for the three school schedule configurations. The data were adjusted for initial differences of gender, minority, and school size on the three schedule configurations. The results suggest that schools may employ various schedule configurations and expect student performance on the Mississippi Biology Subject Area Test to be unaffected. However, many areas of concern were identified in the interviews that might impact on school learning environments. These concerns relate to effective classroom management, the active involvement of students in learning, the adequacy of teacher education

  2. Bioinformatics for the synthetic biology of natural products: integrating across the Design–Build–Test cycle

    PubMed Central

    Currin, Andrew; Jervis, Adrian J.; Rattray, Nicholas J. W.; Swainston, Neil; Yan, Cunyu; Breitling, Rainer

    2016-01-01

    Covering: 2000 to 2016 Progress in synthetic biology is enabled by powerful bioinformatics tools allowing the integration of the design, build and test stages of the biological engineering cycle. In this review we illustrate how this integration can be achieved, with a particular focus on natural products discovery and production. Bioinformatics tools for the DESIGN and BUILD stages include tools for the selection, synthesis, assembly and optimization of parts (enzymes and regulatory elements), devices (pathways) and systems (chassis). TEST tools include those for screening, identification and quantification of metabolites for rapid prototyping. The main advantages and limitations of these tools as well as their interoperability capabilities are highlighted. PMID:27185383

  3. Robust mesoscopic superposition of strongly correlated ultracold atoms

    SciTech Connect

    Hallwood, David W.; Ernst, Thomas; Brand, Joachim

    2010-12-15

    We propose a scheme to create coherent superpositions of annular flow of strongly interacting bosonic atoms in a one-dimensional ring trap. The nonrotating ground state is coupled to a vortex state with mesoscopic angular momentum by means of a narrow potential barrier and an applied phase that originates from either rotation or a synthetic magnetic field. We show that superposition states in the Tonks-Girardeau regime are robust against single-particle loss due to the effects of strong correlations. The coupling between the mesoscopically distinct states scales much more favorably with particle number than in schemes relying on weak interactions, thus making particle numbers of hundreds or thousands feasible. Coherent oscillations induced by time variation of parameters may serve as a 'smoking gun' signature for detecting superposition states.

  4. Emulating a mesoscopic system using superconducting quantum circuits

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Barends, R.; Bochmann, J.; Campbell, B.; Chiaro, B.; Jeffrey, E.; Kelly, J.; Mariantoni, M.; Megrant, A.; Mutus, J.; Neill, C.; O'Malley, P.; Ohya, S.; Roushan, P.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T.; Cleland, A. N.; Martinis, J. M.

    2013-03-01

    We demonstrate an emulation of a mesoscopic system using superconducting quantum circuits. Taking advantage of our ReZQu-architectured quantum processor, we controllably splitted a microwave photon and manipulated the splitted photons before they recombined for detection. In this way, we were able to simulate the weak localization effect in mesoscopic systems - a coherent backscattering process due to quantum interference. The influence of the phase coherence was investigated by tuning the coherence time of the quantum circuit, which in turn mimics the temperature effect on the weak localization process. At the end, we demonstrated an effect resembling universal conductance fluctuations, which arises from the frequency beating between different coherent backscattering processes. The universality of the observed fluctuation was shown as the independence of the fluctuation amplitude on detailed experimental conditions.

  5. Flux flow in current driven mesoscopic superconductors: size effects

    NASA Astrophysics Data System (ADS)

    Sánchez-Lotero, Pedro; Domínguez, Daniel; Albino Aguiar, J.

    2016-06-01

    Flux-flow phenomena in a superconducting mesoscopic stripe submitted to an applied current and external magnetic field is studied. The time-dependent Ginzburg-Landau equations are solved numerically to obtain the electric and magnetic response of the system. It is shown that the I- V curves, for the wider strips, present a universal behaviour. The dependence of the flux-flow resistivity on the magnetic field and width allow us to propose a criterion characterizing, both, the macroscopic and mesoscopic regimes. The power spectrum of the average voltage permits identifying the effect of surface currents in vortices movement. Based on the maximum value of the power spectrum first harmonic we propose a geometric condition for matching between the sample dimensions and the vortex lattice parameter.

  6. Vortex states and magnetization curve of square mesoscopic superconductors.

    SciTech Connect

    Melnikov, A. S.; Nefedov, I. M.; Ryzhov, D. A.; Shereshevskii, I. A.; Vinokur, V. M.; Vysheslavtsev, P. P.; Materials Science Division; Russian Academy of Sciences

    2002-03-22

    The structure of the vortex states in a square mesoscopic superconductor is analyzed in detail using the numerical simulation within the time-dependent Ginzburg-Landau (TDGL) theory. Various vortex states (vortices, vortex molecules, multiquanta vortices) are observed and the magnetization curve is obtained. Different changes in vortex structures are identified with the peculiarities on the magnetization curve. Stability of a state consisting of vortices and antivortices is discussed.

  7. Mesoscopic cell structure of relaxor ferroelectrics at morphotropic phase boundary

    NASA Astrophysics Data System (ADS)

    Ahn, Sang-Jin; Kim, Jong-Jean

    2003-03-01

    Mesoscopic cell structure of relaxor ferroelectrics at morphotropic phase boundary Sang-Jin Ahn and Jong-Jean Kim Physics Department, KAIST, Taejon 305-701, Korea Relaxor-based ferroelectrics such as PZN-xPT and PMN-xPT have drawn a great attention due to an observation of a huge piezoelectric coefficient and an ultra high strain level. Although the first principle calculations on the basis of a single perovskite unit cell structure could explain much of the experimental observations, recent observations of a complex mesoscopic ordering and a heterogeneous domain structure suggest a composite cell of many perovskite units as a basic building block. Raman scattering spectra and observed stoichiometry of PZN-xPT and PMN-xPT allow for only a random pile-up structure of the composite block cells. Our composite block cell needs 27 perovskite unit cells to satisfy the morphotropic phase boundary conditions of structural and compositional variations. Using this mesoscopic block cell model we calculate for allowed mixing concentrations x at morphotropic phase boundaries of relaxor ferroelectrics, which agree with observed values.

  8. Spin Hall effects in mesoscopic Pt films with high resistivity

    NASA Astrophysics Data System (ADS)

    Qin, Chuan; Luo, Yongming; Zhou, Chao; Cai, Yunjiao; Jia, Mengwen; Chen, Shuhan; Wu, Yizheng; Ji, Yi

    2016-10-01

    The energy efficiency of the spin Hall effects (SHE) can be enhanced if the electrical conductivity is decreased without sacrificing the spin Hall conductivity. The resistivity of Pt films can be increased to 150-300 µΩ · cm by mesoscopic lateral confinement, thereby decreasing the conductivity. The SHE and inverse spin Hall effects (ISHE) in these mesoscopic Pt films are explored at 10 K by using the nonlocal spin injection/detection method. All relevant physical quantities are determined in situ on the same substrate, and a quantitative approach is developed to characterize all processes effectively. Extensive measurements with various Pt thickness values reveal an upper limit for the Pt spin diffusion length: {λ\\text{pt}}   ⩽  0.8 nm. The average product of {λ\\text{pt}} and the Pt spin Hall angle {α\\text{H}} is substantial: {α\\text{H}}{λ\\text{pt}}   =  (0.142  ±  0.040) nm for 4 nm thick Pt, though a gradual decrease is observed at larger Pt thickness. The results suggest enhanced spin Hall effects in resistive mesoscopic Pt films.

  9. Energy relaxation rate and its mesoscopic fluctuations in quantum dots

    NASA Astrophysics Data System (ADS)

    Kozii, Vladyslav A.; Skvortsov, Mikhail A.

    2016-08-01

    We analyze the applicability of the Fermi-golden-rule description of quasiparticle relaxation in a closed diffusive quantum dot with electron-electron interaction. Assuming that single-particle levels are already resolved but the initial stage of quasiparticle disintegration can still be described by a simple exponential decay, we calculate the average inelastic energy relaxation rate of single-particle excitations and its mesoscopic fluctuations. The smallness of mesoscopic fluctuations can then be used as a criterion for the validity of the Fermi-golden-rule description. Technically, we implement the real-space Keldysh diagram technique, handling correlations in the quasi-discrete spectrum non-perturbatively by means of the non-linear supersymmetric sigma model. The unitary symmetry class is considered for simplicity. Our approach is complementary to the lattice-model analysis of Fock space: though we are not able to describe many-body localization, we derive the exact lowest-order expression for mesoscopic fluctuations of the relaxation rate, making no assumptions on the matrix elements of the interaction. It is shown that for the quasiparticle with the energy ε on top of the thermal state with the temperature T, fluctuations of its energy width become large and the Fermi-golden-rule description breaks down at max { ε , T } ∼ Δ√{ g }, where Δ is the mean level spacing in the quantum dot, and g is its dimensionless conductance.

  10. An investigation of algebraic quantum dynamics for mesoscopic coupled electric circuits with mutual inductance

    NASA Astrophysics Data System (ADS)

    Pahlavani, H.; Kolur, E. Rahmanpour

    2016-08-01

    Based on the electrical charge discreteness, the Hamiltonian operator for the mutual inductance coupled quantum mesoscopic LC circuits has been found. The persistent current on two driven coupled mesoscopic electric pure L circuits (two quantum loops) has been obtained by using algebraic quantum dynamic approach. The influence of the mutual inductance on energy spectrum and quantum fluctuations of the charge and current for two coupled quantum electric mesoscopic LC circuits have been investigated.

  11. 76 FR 36019 - Amendments to Sterility Test Requirements for Biological Products

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-21

    ... November 20, 1973 (38 FR 32048), we reorganized and republished the biologics regulations, which included... requirements. On March 11, 1976 (41 FR 10427) and March 2, 1979 (44 FR 11754), we updated Sec. 610.12 to clarify the procedures for repeat testing. On April 18, 1984 (49 FR 15186), we amended Sec. 610.12...

  12. Sound and Faulty Arguments Generated by Preservice Biology Teachers When Testing Hypotheses Involving Unobservable Entities.

    ERIC Educational Resources Information Center

    Lawson, Anton E.

    2002-01-01

    Investigates the responses of a sample of preservice biology teachers enrolled in a teaching methods course to a casual question about why water rose in a jar inverted over a burning candle placed in a pan of water by formulating and testing six hypotheses. (Contains 43 references.) (Author/YDS)

  13. Gender Differences in Caribbean Students' Performance on a Test of Errors in Biological Labelling.

    ERIC Educational Resources Information Center

    Soyibo, Kola

    1999-01-01

    Discusses the performance of 11th-grade students from Barbados, Belize, Jamaica, St. Lucia, St. Vincent, and Trinidad (n=1216) on an Errors in Biological Labeling Test (EBLT). Concludes that performance was low in six categories of errors, and that girls performed significantly better on each category of error than did boys. Contains 15…

  14. Causal attributions of obese men and women in genetic testing: implications of genetic/biological attributions.

    PubMed

    Hilbert, Anja; Dierk, Jan-Michael; Conradt, Matthias; Schlumberger, Pia; Hinney, Anke; Hebebrand, Johannes; Rief, Winfried

    2009-09-01

    The present study sought to investigate genetic/biological attributions of obesity, their associations with a predisposition to obesity and their crossectional and longitudinal implications for weight regulation in obese individuals presenting for genetic testing and counselling. A total of 421 obese men and women underwent psychological and anthropometric assessment and a mutation screen of the melanocortin-4 receptor gene. At study entry, women revealed more genetic/biological attributions than men on the Revised Illness Perception Questionnaire adapted to obesity (86.2% versus 59.7%). Genetic/biological attributions of obesity were associated in both sexes with a family history of obesity, assessed through Stunkard's Figure Rating Scale. In both sexes, genetic/biological attributions were unrelated to weight regulation beliefs and behaviour (i.e. self-efficacy, controllability beliefs, restrained eating and physical activity), assessed through standardised questionnaires or interview at baseline and at six-month follow-up. In addition, causal attributions and weight regulation beliefs and behaviour were not predictive of body mass index at six-month follow-up. Overall, the results indicate that causal attributions of obesity to genetic/biological factors in obese individuals presenting for genetic screening and counselling are crossectionally and longitudinally unrelated to weight regulation and longer-term weight outcome. Those who attribute their obesity to genetic/biological factors likely have a familial obesity risk. PMID:20205024

  15. - and Mesoscopic Soft Condensed Matter Architectures on Semiconductor Surfaces

    NASA Astrophysics Data System (ADS)

    Samuilov, Vladimir; Seo, Young-Soo; Ksenevich, Vitaly; Galibert, Jean; Sokolov, John; Rafailovich, Miriam

    2003-03-01

    A novel and simple approach of self-organized fabrication of two dimensional mesoscopic networks with the feature size down to 50 nm has been developed. The technique is based on the self-organized patterning in a thin layer of complex liquid (polymer solution) in the presence of humid atmosphere. Two dimensional mesoscopic honeycomb-shaped carbon structures were produced by high temperature annealing of nitrocellulose precursors [1]. The polymer network was also utilized as a mask for further reactive ion etching of surfaces with epi-layer of GaAs [2,3] and GaAs/AlGaAs ? -doped heterostructures [4]. The electrical transport in the obtained structures was studied in a temperature range from 1.9 to 300 K and in pulsed magnetic fields up to 35 T. A crossover from the Mott variable range hopping to the Colomb-gap Efros-Shklovskii variable range hopping has been observed experimentally in mesoscopic carbon structures [1]. At low fields, ln(R/R0) is proportional to B2. In the intermediate range, the magnetoresistance is linear on B. At high temperatures, if the hopping distance is comparable to the localization length, the observed small negative magnetoresistance in our samples is consistent to the weak-localization picture. Magnetoresistance of patterned GaAs/AlGaAs ?-doped structures is negative [4], which is relater to quantum interference in hopping regime. At B=0, the resistance showed typical behavior of a two-dimensional hopping. Below about 20 K, the data followed the Mott variable-range-hopping mechanism for two dimensions. Also, we have used diblock-copolymer system, self-assembled with L-B technique, to produce nano-patterns. These structures were utilized as templates for introducing metal nanopatterns on semiconductor surfaces by reactive ion beam etching for magnetic storage systems [5] and DNA separation on a flat surface [6] devices. 1. V.A. Samuilov, J. Galibert, V.K. Ksenevich, V.J. Goldman, M. Rafailovich, J. Sokolov, I.A. Bashmakov, V.A. Dorosinets

  16. Offer of rapid testing and alternative biological samples as practical tools to implement HIV screening programs.

    PubMed

    Parisi, Maria Rita; Soldini, Laura; Di Perri, Giovanni; Tiberi, Simon; Lazzarin, Adriano; Lillo, Flavia B

    2009-10-01

    Implementation of HIV testing has the objective to increase screening, identify and counsel persons with infection, link them to clinical services and reduce transmission. Rapid tests and/or alternative biological samples (like oral fluid) give the option for a better general consent in approaching screening, immediate referral of HIV positives to medical treatment and partner notification. We tested the performance characteristics of an oral fluid-based rapid HIV test (Rapidtest HIV lateral flow-Healthchem diag. LLC) in comparison with routinely utilized methods in a selected population of known positive (N = 121) or negative (N = 754) subjects. The sensitivity of the rapid test was 99.1% (one false negative sample) and the specificity 98.8%. Five negatives showed a faint reactivity, 3 of these were reactive also in the reference test, one with a p24 only reaction in Western blot. If these 3 samples were excluded from the analysis the specificity increases to 99.2%. Results from our study confirm that, although a continuous improvement of the test performance is still needed to minimize false negative and positive results, rapid test and alternative biological samples may contribute to HIV prevention strategies by reaching a larger population particularly when and where regular screening procedures are difficult to obtain. PMID:20128446

  17. A new approach for biological online testing of stack gas condensate from municipal waste incinerators.

    PubMed

    Elsner, Dorothea; Fomin, Anette

    2002-01-01

    A biological testing system for the monitoring of stack gas condensates of municipal waste incinerators has been developed using Euglena gracilis as a test organism. The motility, velocity and cellular form of the organisms were the endpoints, calculated by an image analysis system. All endpoints showed statistically significant changes in a short time when organisms were exposed to samples collected during combustion situations with increased pollutant concentrations. The velocity of the organisms proved to be the most appropriate endpoint. A semi-continuous system with E. gracilis for monitoring stack gas condensate is proposed, which could result in an online system for testing stack gas condensates in the future.

  18. Personalized Genetic Testing as a Tool for Integrating Ethics Instruction into Biology Courses

    PubMed Central

    Zhang, Tenny R.; Anderson, Misti Ault

    2014-01-01

    Personalized genetic testing (PGT) has been used by some educational institutions as a pedagogical tool for teaching human genetics. While work has been done that examines the potential for PGT to improve students’ interest and understanding of the science involved in genetic testing, there has been less dialogue about how this method might be useful for integrating ethical and societal issues surrounding genetic testing into classroom discussions. Citing the importance of integrating ethics into the biology classroom, we argue that PGT can be an effective educational tool for integrating ethics and science education, and discuss relevant ethical considerations for instructors using this approach. PMID:25574278

  19. Development and testing of hyperbaric atomic force microscopy (AFM) and fluorescence microscopy for biological applications.

    PubMed

    D'Agostino, D P; McNally, H A; Dean, J B

    2012-05-01

    A commercially available atomic force microscopy and fluorescence microscope were installed and tested inside a custom-designed hyperbaric chamber to provide the capability to study the effects of hyperbaric gases on biological preparations, including cellular mechanism of oxidative stress. In this report, we list details of installing and testing atomic force microscopy and fluorescence microscopy inside a hyperbaric chamber. The pressure vessel was designed to accommodate a variety of imaging equipment and ensures full functionality at ambient and hyperbaric conditions (≤85 psi). Electrical, gas and fluid lines were installed to enable remote operation of instrumentation under hyperbaric conditions, and to maintain viable biological samples with gas-equilibrated superfusate and/or drugs. Systems were installed for vibration isolation and temperature regulation to maintain atomic force microscopy performance during compression and decompression. Results of atomic force microscopy testing demonstrate sub-nanometre resolution at hyperbaric pressure in dry scans and fluid scans, in both contact mode and tapping mode. Noise levels were less when measurements were taken under hyperbaric pressure with air, helium (He) and nitrogen (N(2) ). Atomic force microscopy and fluorescence microscopy measurements were made on a variety of living cell cultures exposed to hyperbaric gases (He, N(2) , O(2) , air). In summary, atomic force microscopy and fluorescence microscopy were installed and tested for use at hyperbaric pressures and enables the study of cellular and molecular effects of hyperbaric gases and pressure per se in biological preparations.

  20. Expertise for Teaching Biology Situated in the Context of Genetic Testing

    NASA Astrophysics Data System (ADS)

    Van der Zande, Paul; Akkerman, Sanne F.; Brekelmans, Mieke; Waarlo, Arend Jan; Vermunt, Jan D.

    2012-07-01

    Contemporary genomics research will impact the daily practice of biology teachers who want to teach up-to-date genetics in secondary education. This article reports on a research project aimed at enhancing biology teachers' expertise for teaching genetics situated in the context of genetic testing. The increasing body of scientific knowledge concerning genetic testing and the related consequences for decision-making indicate the societal relevance of an educational approach based on situated learning. What expertise do biology teachers need for teaching genetics in the personal health context of genetic testing? This article describes the required expertise by exploring the educational practice. Nine experienced teachers were interviewed about the pedagogical content, moral and interpersonal expertise areas concerning how to teach genetics in the personal health context of genetic testing, and the lessons of five of them were observed. The findings showed that the required teacher expertise encompasses specific pedagogical content expertise, interpersonal expertise and a preference for teacher roles and teaching approaches for the moral aspects of teaching in this context. A need for further development of teaching and learning activities for (reflection on) moral reasoning came to the fore. Suggestions regarding how to apply this expertise into context-based genetics education are discussed.

  1. BEO-Life, a Test and Refurbishment Support for Biological Research Facilities

    NASA Astrophysics Data System (ADS)

    Engeln, I.; Hueser, D.; Reese, C.; Schoenfeld, R.

    Since the ISS commenced its operational phase, the need of ground based test and refurbishment support, facilitating the utilisation of the station and especially its facilities for biological research, becomes increasingly important.. The onboard biological research facilities (e.g. BIOLAB) are designed and built for a life time of 10 years, requiring the regular exchange of the integrated life support systems. The exact conditioning of the atmosphere in these systems plays an important role for the scientific outcome. The composition of the air (O2, N2 and CO2) as well as the humidity and the temperature inside the experiment chambers containing the plants and cell-cultures needs to be adjustable for various types of experiments. Since the various ingredients for a life support system are consumables, which consumption depends on the number of performed experiments, the life support systems needs to be refurbished from time to time. Our contribution to this challenge is BEO- Life, which offers a unique test, refurbishment and qualification environment for maintenance and re-supply for life support systems of the ISS onboard biological facilities. BEO-Life provides the ground support for all these tasks, such as tests, maintenance, verification and procedures. To fulfil the demanding requirements for the automatic and stable conditioning of the life support system, a complex arrangement of pumps, valves, sensors and an electronic system including software with exact control algorithms is provided. Beside the refurbishment activities, BEO-Life will support preliminary ground-based investigations of scientists before utilisation of the ISS biological research facilities, too. In conclusion, we offer a novel service element for the ground-based maintenance of biological research facilities onboard the ISS. This service can be easily adapted to the needs of users for preparatory work.

  2. [Testing the sterilisation effect of autoclaves by means of biological indicators (author's transl)].

    PubMed

    Werner, H P; Kindt, R; Borneff, J

    1975-07-01

    Because of the great number of failures with sterilization-programs it seems to be necessary to check up the effect of sterilization not only by the annual official tests but also continuously with biological indicators. Marketable indicators have not to be tested necessarily at present. Therefore six different types of indicators were examined experimentally and under practice-conditions. As to be seen in table 1 samples of the same charge didn't show great differences, in spite of this germ-counts of several charges differed considerably. Reductions of germ-counts after sterilization in the autoclave at 123,5 degrees C (fig. 1) and at 134 degrees C (fig 2), as well as with hot air at 120-125 degrees C (fig 3) and 133-138 degrees C (fig 4) demonstrate the heat-resistance. The individual biological indicators differ in killing-time and times of survival (table 2). Our tests demonstrate that only single biological indicators (table 4) will grant satisfying results in continuous checking of sterilization process. PMID:811008

  3. Proximity effect thermometer for local temperature measurements on mesoscopic samples.

    SciTech Connect

    Aumentado, J.; Eom, J.; Chandrasekhar, V.; Baldo, P. M.; Rehn, L. E.; Materials Science Division; Northwestern Univ; Univ. of Chicago

    1999-11-29

    Using the strong temperature-dependent resistance of a normal metal wire in proximity to a superconductor, we have been able to measure the local temperature of electrons heated by flowing a direct-current (dc) in a metallic wire to within a few tens of millikelvin at low temperatures. By placing two such thermometers at different parts of a sample, we have been able to measure the temperature difference induced by a dc flowing in the samples. This technique may provide a flexible means of making quantitative thermal and thermoelectric measurements on mesoscopic metallic samples.

  4. Mesoscopic Rydberg Gate Based on Electromagnetically Induced Transparency

    SciTech Connect

    Mueller, M.; Lesanovsky, I.; Zoller, P.; Weimer, H.; Buechler, H. P.

    2009-05-01

    We demonstrate theoretically a parallelized C-NOT gate which allows us to entangle a mesoscopic ensemble of atoms with a single control atom in a single step, with high fidelity and on a microsecond time scale. Our scheme relies on the strong and long-ranged interaction between Rydberg atoms triggering electromagnetically induced transparency. By this we can robustly implement a conditional transfer of all ensemble atoms between two logical states, depending on the state of the control atom. We outline a many-body interferometer which allows a comparison of two many-body quantum states by performing a measurement of the control atom.

  5. Mesoscopic Simulations of Microfluidic Flow in Irregular Geometries

    NASA Astrophysics Data System (ADS)

    Shendruk, Tyler N.; Slater, Gary W.

    2009-03-01

    Stochastic Rotation Dynamics, a particle-based model for mesoscopic fluid dynamics, is used to study two and three-dimensional flow in a variety of complex boundaries and for a range of low Reynolds numbers (between 10 and 200). The systems considered are of two types: they consist of either irregular geometries such as dimpled pipes or require adaptive boundary conditions such as particle impact on a solid boundary. We apply out techniques to microfluidic devices with complex channel walls such as those used for slalom chromatography and sinusoidal undulation surface patterning chromatography. Numerical results showing good agreement with experimental data and previous computational simulations are presented.

  6. A mesoscopic network model for permanent set in crosslinked elastomers

    SciTech Connect

    Weisgraber, T H; Gee, R H; Maiti, A; Clague, D S; Chinn, S; Maxwell, R S

    2009-01-29

    A mesoscopic computational model for polymer networks and composites is developed as a coarse-grained representation of the composite microstructure. Unlike more complex molecular dynamics simulations, the model only considers the effects of crosslinks on mechanical behavior. The elastic modulus, which depends only on the crosslink density and parameters in the bond potential, is consistent with rubber elasticity theory, and the network response satisfies the independent network hypothesis of Tobolsky. The model, when applied to a commercial filled silicone elastomer, quantitatively reproduces the experimental permanent set and stress-strain response due to changes in the crosslinked network from irradiation.

  7. Vortical versus skyrmionic states in mesoscopic p -wave superconductors

    NASA Astrophysics Data System (ADS)

    Fernández Becerra, V.; Sardella, E.; Peeters, F. M.; Milošević, M. V.

    2016-01-01

    We investigate the superconducting states that arise as a consequence of mesoscopic confinement and a multicomponent order parameter in the Ginzburg-Landau model for p -wave superconductivity. Conventional vortices, but also half-quantum vortices and skyrmions, are found as the applied magnetic field and the anisotropy parameters of the Fermi surface are varied. The solutions are well differentiated by a topological charge that for skyrmions is given by the Hopf invariant and for vortices by the circulation of the superconducting velocity. We revealed several unique states combining vortices and skyrmions, their possible reconfiguration with varied magnetic field, as well as temporal and field-induced transitions between vortical and skyrmionic states.

  8. Phosphorus recycling potential assessment by a biological test applied to wastewater sludge.

    PubMed

    Braak, Etienne; Auby, Sarah; Piveteau, Simon; Guilayn, Felipe; Daumer, Marie-Line

    2016-01-01

    Phosphorus (P) recycling as mineral fertilizer from wastewater activated sludge (WAS) depends on the amount that can be dissolved and separated from the organic matter before the final crystallization step. The aim of the biological phosphorus dissolution potential (BPDP) test developed here was to assess the maximum amount of P that could be biologically released from WAS prior that the liquid phase enters the recovery process. It was first developed for sludge combining enhanced biological phosphorus removal and iron chloride. Because carbohydrates are known to induce acidification during the first stage of anaerobic digestion, sucrose was used as a co-substrate. Best results were obtained after 24-48 h, without inoculum, with a sugar/sludge ratio of 0.5 gCOD/gVS and under strict anaerobic conditions. Up to 75% of the total phosphorus in sludge from a wastewater treatment plant combining enhanced biological phosphorus removal and iron chloride phosphorus removal could be dissolved. Finally, the test was applied to assess BPDP from different sludge using alum compounds for P removal. No dissolution was observed when alum polychloride was used and less than 20% when alum sulphate was used. In all the cases, comparison to chemical acidification showed that the biological process was a major contributor to P dissolution. The possibility to crystallize struvite was discussed from the composition of the liquids obtained. The BPDP will be used not only to assess the potential for phosphorus recycling from sludge, but also to study the influence of the co-substrates available for anaerobic digestion of sludge.

  9. Phosphorus recycling potential assessment by a biological test applied to wastewater sludge.

    PubMed

    Braak, Etienne; Auby, Sarah; Piveteau, Simon; Guilayn, Felipe; Daumer, Marie-Line

    2016-01-01

    Phosphorus (P) recycling as mineral fertilizer from wastewater activated sludge (WAS) depends on the amount that can be dissolved and separated from the organic matter before the final crystallization step. The aim of the biological phosphorus dissolution potential (BPDP) test developed here was to assess the maximum amount of P that could be biologically released from WAS prior that the liquid phase enters the recovery process. It was first developed for sludge combining enhanced biological phosphorus removal and iron chloride. Because carbohydrates are known to induce acidification during the first stage of anaerobic digestion, sucrose was used as a co-substrate. Best results were obtained after 24-48 h, without inoculum, with a sugar/sludge ratio of 0.5 gCOD/gVS and under strict anaerobic conditions. Up to 75% of the total phosphorus in sludge from a wastewater treatment plant combining enhanced biological phosphorus removal and iron chloride phosphorus removal could be dissolved. Finally, the test was applied to assess BPDP from different sludge using alum compounds for P removal. No dissolution was observed when alum polychloride was used and less than 20% when alum sulphate was used. In all the cases, comparison to chemical acidification showed that the biological process was a major contributor to P dissolution. The possibility to crystallize struvite was discussed from the composition of the liquids obtained. The BPDP will be used not only to assess the potential for phosphorus recycling from sludge, but also to study the influence of the co-substrates available for anaerobic digestion of sludge. PMID:26786893

  10. Sound and faulty arguments generated by preservice biology teachers when testing hypotheses involving unobservable entities

    NASA Astrophysics Data System (ADS)

    Lawson, Anton E.

    2002-03-01

    A sample of preservice biology teachers (biology majors) enrolled in a teaching methods course formulated and attempted to test six hypotheses to answer a causal question about why water rose in a jar inverted over a burning candle placed in a pan of water. The students submitted a lab report in which arguments and evidence for testing each hypothesis were presented in an if/then/therefore hypothetico-predictive form. Analysis of written arguments revealed considerable success when students were able to manipulate observable hypothesized causes. However, when the hypothesized causes were unobservable, such that they could be only indirectly tested, performance dropped, as shown by use of three types of faulty arguments: (a) arguments that had missing or confused elements, (b) arguments whose predictions did not follow from hypotheses and planned tests, and (c) arguments that failed to consider alternative hypotheses. Science is an enterprise in which unobservable theoretical entities and processes (e.g., atoms, genes, osmosis, and photosynthesis) are often used to explain observable phenomena. Consequently, if it is assumed that effective teaching requires prior understanding, then it follows that these future teachers have yet to develop adequate hypothesis-testing skills and sufficient awareness of the nature of science to teach science in the inquiry mode advocated by reform guidelines.

  11. Mesoscopic theory of the viscoelasticity of polymers

    SciTech Connect

    Chitanvis, S.M. )

    1999-09-01

    We have advanced our previous static theory of polymer entanglement involving an extended Cahn-Hilliard functional, to include time-dependent dynamics. We go beyond the Gaussian approximation, to the one-loop level, to compute the frequency dependent storage and loss moduli of the system. The four parameters in our theory are obtained by fitting to available experimental data on polystyrene melts of various chain lengths. This provides a physical representation of the parameters in terms of the chain length of the system. It is shown that the parameters chosen describe the crossover from an unentangled to an entangled state. The crossover is characterized by a dramatic increase in a time scale appearing in the theory, analogous to critical slowing down in phase transition theory. This result should stimulate more detailed experiments in this regime to test this concept. [copyright] [ital 1999] [ital The American Physical Society

  12. Insects as test systems for assessing the potential role of microgravity in biological development and evolution

    NASA Astrophysics Data System (ADS)

    Vernós, I.; Carratalá, M.; González-Jurado, J.; Valverde, J. R.; Calleja, M.; Domingo, A.; Vinós, J.; Cervera, M.; Marco, R.

    Gravity and radiation are undoubtedly the two major environmental factors altered in space. Gravity is a weak force, which creates a permanent potential field acting on the mass of biological systems and their cellular components, strongly reduced in space flights. Developmental systems, particularly at very early stages, provide the larger cellular compartments known, where the effects of alterations in the size of the gravity vector on living organisms can be more effectively tested. The insects, one of the more highly evolved classes of animals in which early development occurs in a syncytial embryo, are systems particularly well suited to test these effects and the specific developmental mechanisms affected. Furthermore, they share some basic features such as small size, short life cycles, relatively high radio-resistance, etc. and show a diversity of developmental strategies and tempos advantageous in experiments of this type in space. Drosophila melanogaster, the current biological paradigm to study development, with so much genetic and evolutionary background available, is clearly the reference organism for these studies. The current evidence on the effects of the physical parameters altered in space flights on insect development indicate a surprising correlation between effects seen on the fast developing and relatively small Drosophila embryo and the more slowly developing and large Carausius morosus system. In relation to the issue of the importance of developmental and environmental constraints in biological evolution, still the missing link in current evolutionary thinking, insects and space facilities for long-term experiments could provide useful experimental settings where to critically assess how development and evolution may be interconnected. Finally, it has to be pointed out that since there are experimental data indicating a possible synergism between microgravity and space radiation, possible effects of space radiation should be taken into

  13. Detecting Change in Biological Rhythms: A Multivariate Permutation Test Approach to Fourier-Transformed Data

    PubMed Central

    Blackford, Jennifer Urbano; Salomon, Ronald M.; Waller, Niels G.

    2009-01-01

    Treatment-related changes in neurobiological rhythms are of increasing interest to psychologists, psychiatrists, and biological rhythms researchers. New methods for analyzing change in rhythms are needed, as most common methods disregard the rich complexity of biological processes. Large time series data sets reflect the intricacies of underlying neurobiological processes, but can be difficult to analyze. We propose the use of Fourier methods with multivariate permutation test (MPT) methods for analyzing change in rhythms from time series data. To validate the use of MPT for Fourier-transformed data, we performed Monte Carlo simulations and compared statistical power and family-wise error for MPT to Bonferroni-corrected and uncorrected methods. Results show that MPT provides greater statistical power than Bonferroni-corrected tests, while appropriately controlling family-wise error. We applied this method to human, pre-and post-treatment, serially-sampled neurotransmitter data to confirm the utility of this method using real data. Together, Fourier with MPT methods provides a statistically powerful approach for detecting change in biological rhythms from time series data. PMID:19212840

  14. METHODS FOR USING 3-D ULTRASOUND SPECKLE TRACKING IN BIAXIAL MECHANICAL TESTING OF BIOLOGICAL TISSUE SAMPLES

    PubMed Central

    Yap, Choon Hwai; Park, Dae Woo; Dutta, Debaditya; Simon, Marc; Kim, Kang

    2014-01-01

    Being multilayered and anisotropic, biological tissues such as cardiac and arterial walls are structurally complex, making full assessment and understanding of their mechanical behavior challenging. Current standard mechanical testing uses surface markers to track tissue deformations and does not provide deformation data below the surface. In the study described here, we found that combining mechanical testing with 3-D ultrasound speckle tracking could overcome this limitation. Rat myocardium was tested with a biaxial tester and was concurrently scanned with high-frequency ultrasound in three dimensions. The strain energy function was computed from stresses and strains using an iterative non-linear curve-fitting algorithm. Because the strain energy function consists of terms for the base matrix and for embedded fibers, spatially varying fiber orientation was also computed by curve fitting. Using finite-element simulations, we first validated the accuracy of the non-linear curve-fitting algorithm. Next, we compared experimentally measured rat myocardium strain energy function values with those in the literature and found a matching order of magnitude. Finally, we retained samples after the experiments for fiber orientation quantification using histology and found that the results satisfactorily matched those computed in the experiments. We conclude that 3-D ultrasound speckle tracking can be a useful addition to traditional mechanical testing of biological tissues and may provide the benefit of enabling fiber orientation computation. PMID:25616585

  15. Modeling of mesoscopic electrokinetic phenomena using charged dissipative particle dynamics

    NASA Astrophysics Data System (ADS)

    Deng, Mingge; Li, Zhen; Karniadakis, George

    2015-11-01

    In this work, we propose a charged dissipative particle dynamics (cDPD) model for investigation of mesoscopic electrokinetic phenomena. In particular, this particle-based method was designed to simulate micro- or nano- flows which governing by Poisson-Nernst-Planck (PNP) equation coupled with Navier-Stokes (NS) equation. For cDPD simulations of wall-bounded fluid systems, a methodology for imposing correct Dirichlet and Neumann boundary conditions for both PNP and NS equations is developed. To validate the present cDPD model and the corresponding boundary method, we perform cDPD simulations of electrostatic double layer (EDL) in the vicinity of a charged wall, and the results show good agreement with the mean-field theoretical solutions. The capacity density of a parallel plate capacitor in salt solution is also investigated with different salt concentration. Moreover, we utilize the proposed methodology to study the electroosmotic and electroosmotic/pressure-driven flow in a micro-channel. In the last, we simulate the dilute polyelectrolyte solution both in bulk and micro-channel, which show the flexibility and capability of this method in studying complex fluids. This work was sponsored by the Collaboratory on Mathematics for Mesoscopic Modeling of Materials (CM4) supported by DOE.

  16. Assessment of mesoscopic particle-based methods in microfluidic geometries

    NASA Astrophysics Data System (ADS)

    Zhao, Tongyang; Wang, Xiaogong; Jiang, Lei; Larson, Ronald G.

    2013-08-01

    We assess the accuracy and efficiency of two particle-based mesoscopic simulation methods, namely, Dissipative Particle Dynamics (DPD) and Stochastic Rotation Dynamics (SRD) for predicting a complex flow in a microfluidic geometry. Since both DPD and SRD use soft or weakly interacting particles to carry momentum, both methods contain unavoidable inertial effects and unphysically high fluid compressibility. To assess these effects, we compare the predictions of DPD and SRD for both an exact Stokes-flow solution and nearly exact solutions at finite Reynolds numbers from the finite element method for flow in a straight channel with periodic slip boundary conditions. This flow represents a periodic electro-osmotic flow, which is a complex flow with an analytical solution for zero Reynolds number. We find that SRD is roughly ten-fold faster than DPD in predicting the flow field, with better accuracy at low Reynolds numbers. However, SRD has more severe problems with compressibility effects than does DPD, which limits the Reynolds numbers attainable in SRD to around 25-50, while DPD can achieve Re higher than this before compressibility effects become too large. However, since the SRD method runs much faster than DPD does, we can afford to enlarge the number of grid cells in SRD to reduce the fluid compressibility at high Reynolds number. Our simulations provide a method to estimate the range of conditions for which SRD or DPD is preferable for mesoscopic simulations.

  17. Density functional theory for systems with mesoscopic inhomogeneities

    NASA Astrophysics Data System (ADS)

    Ciach, A.; Gozdz, W. T.

    2016-06-01

    We study the effects of fluctuations on the mesoscopic length scale on systems with mesoscopic inhomogeneities. Equations for the correlation function and for the average volume fraction are derived in the self-consistent Gaussian approximation. The equations are further simplified by postulating the expression for the structure factor consistent with scattering experiments for self-assembling systems. Predictions of the approximate theory are verified by a comparison with the exact results obtained earlier for the one-dimensional lattice model with first-neighbor attraction and third-neighbor repulsion. We find qualitative agreement for the correlation function, the equation of state and the dependence of the chemical potential μ on the volume fraction ζ. Our results confirm also that strong inhomogeneities in the disordered phase are found only in the case of strong repulsion. The inhomogeneities are reflected in an oscillatory decay of the correlation function with a very large correlation length, three inflection points in the μ ≤ft(\\zeta \\right) curve and a compressibility that for increasing ζ takes very large, very small and again very large values.

  18. Insight or illusion? Seeing inside the cell with mesoscopic simulations

    PubMed Central

    Shillcock, Julian C.

    2008-01-01

    The expulsion of material from a cell by fusion of vesicles at the plasma membrane, and the entry of a virus by membrane invagination are complex membrane-associated processes whose control is crucial to cell survival. Our ability to visualize the dynamics of such processes experimentally is limited by spatial resolution and the speed of molecular rearrangements. The increase in computing power of the last few decades enables the construction of computational tools for observing cellular processes in silico. As experiments yield increasing amounts of data on the protein and lipid constituents of the cell, computer simulations parametrized using this data are beginning to allow models of cellular processes to be interrogated in ways unavailable in the laboratory. Mesoscopic simulations retain only those molecular features that are believed to be relevant to the processes of interest. This allows the dynamics of spatially heterogeneous membranes and the crowded cytoplasmic environment to be followed at a modest computational cost. The price for such power is that the atomic detail of the constituents is much lower than in atomistic Molecular Dynamics simulations. We argue that this price is worth paying because mesoscopic simulations can generate new insight into the complex, dynamic life of a cell. PMID:19404447

  19. HRI catalytic two-stage liquefaction (CTSL) process materials: chemical analysis and biological testing

    SciTech Connect

    Wright, C.W.; Later, D.W.

    1985-12-01

    This report presents data from the chemical analysis and biological testing of coal liquefaction materials obtained from the Hydrocarbon Research, Incorporated (HRI) catalytic two-stage liquefaction (CTSL) process. Materials from both an experimental run and a 25-day demonstration run were analyzed. Chemical methods of analysis included adsorption column chromatography, high-resolution gas chromatography, gas chromatography/mass spectrometry, low-voltage probe-inlet mass spectrometry, and proton nuclear magnetic resonance spectroscopy. The biological activity was evaluated using the standard microbial mutagenicity assay and an initiation/promotion assay for mouse-skin tumorigenicity. Where applicable, the results obtained from the analyses of the CTSL materials have been compared to those obtained from the integrated and nonintegrated two-stage coal liquefaction processes. 18 refs., 26 figs., 22 tabs.

  20. Unconventional states and geometric effects in mesoscopic systems of ultra-cold atomic Fermi gases

    SciTech Connect

    Bolech, C. J.

    2014-10-15

    During the last decade, experiments all over the world started to test the superconducting state of matter using a newly developed mesoscopic tunable system: trapped ultra-cold atomic gases. Theorists and experimentalists hand-in-hand are now able to advance our understanding of the superconducting state by asking new questions that probe further into the physical mechanisms underlying the phenomenon and the door is open to the exploration of exotic unconventional superconducting states. In particular, a series of experiments on systems of trapped cold atomic gases were aimed at studying the effects of polarization on superconducting pairing. Two different experimental groups encountered surprising qualitative and quantitative discrepancies which seemed to be a function of the confining geometry and the cooling protocol. Our numerical studies demonstrate a tendency towards metastability and suggest an explanation for the observed discrepancy. From our calculations, the most likely solution which is consistent with the experiments supports a state strikingly similar to the so called FFLO state (after Ferrell, Fulde, Larkin and Ovchinnikov), which had been theorized long ago but eluded detection so far. Moreover, the three-dimensional scenario described above is reminiscent of predictions for one-dimensional systems of dilute polarized attractive gases and another set of ultra-cold-atom experiments incorporates optical lattices to study this reduced-dimensionality setting. The measurements are in quantitative agreement with theoretical calculations (using a wide array of numerical and analytic techniques) in which a partially polarized phase is found to be the one-dimensional analogue of the FFLO state. Moreover, exploring the dimensional-crossover regime, our latest findings indicate that the mesoscopic nature of these quasi-one-dimensional systems favors the appearance of a new type of Mott phase transition involving an emergent pair-superfluid of equal

  1. Persistent Currents and Quantum Critical Phenomena in Mesoscopic Physics

    NASA Astrophysics Data System (ADS)

    Zelyak, Oleksandr

    In this thesis, we study persistent currents and quantum critical phenomena in the systems of mesoscopic physics. As an introduction in Chapter 1 we familiarize the reader with the area of mesoscopic physics. We explain how mesoscopic systems are different from quantum systems of single atoms and molecules and bulk systems with an Avogadro number of elements. We also describe some important mesoscopic phenomena. One of the mathematical tools that we extensively use in our studies is Random Matrix Theorty. This theory is not a part of standard physics courses and for educational purposes we provide the basics of Random Matrix Theory in Chapter 2. In Chapter 3 we study the persistent current of noninteracting electrons in quantum billiards. We consider simply connected chaotic Robnik-Berry quantum billiard and its annular analog. The electrons move in the presence of a point-like magnetic flux at the center of the billiard. For the simply connected billiard, we find a large diamagnetic contribution to the persistent current at small flux, which is independent of the flux and is proportional to the number of electrons (or equivalently the density since we keep the area fixed). The size of this diamagnetic contribution is much larger than the previously studied mesoscopic fluctuations in the persistent current in the simply connected billiard. This behavior of persistent current can ultimately be traced to the response of the angular-momentum l = 0 levels (neglected in semiclassical expansions) on the unit disk to a point-like flux at its center. We observe the same behavior for the annular billiard when the inner radius is much smaller than the outer one. We also find that the usual fluctuating persistent current and Anderson-like localization due to boundary scattering are seen when the annulus tends to a one-dimensional ring. We explore the conditions for the observability of this phenomenon. In Chapter 4 we study quantum critical phenomena in a system of two

  2. [Plasma antioxidant activity--a test for impaired biological functions of endoecology, exotrophy, and inflammation reactions].

    PubMed

    Titov, V N; Krylin, V V; Dmitriev, V A; Iashin, Ia I

    2010-07-01

    The authors discuss the diagnostic value of a test for total serum antioxidant activity determined by an electrochemistry method on a liquid chromatograph (without a column), by using an amperometric detector, as well as the composition of the endogenously synthesized hydrophilic and hydrophobic acceptors of reactive oxygen species (ROS). Uric acid is a major hydrophilic acceptor of ROS; monoenic oleic fatty acid acts as its major lipophilic acceptor. The constant determined by the authors for of 03 oleic acid oxidation during automatic titration in the organic medium is an order of magnitude higher than that for alpha-tocopherol, beta-carotene and linoleic fatty acid; its concentration is also an order of magnitude higher. In oxidative stress, the adrenal steroid hormone dehydroepiandrosterone initiates oleic acid synthesis via expression of palmitoyl elongase and steatoryl desaturase. In early steps of phylogenesis in primates, spontaneous mutation resulted in ascorbic acid synthesis gene knockout; phylogenetically, further other mutation knocked out the gene encoding the synthesis of uricase and the conversion of uric acid to alantoin. In primates, uric acid became not only a catabolite of purine bases in vivo, but also the major endogenous hydrophilic acceptor of ROS. This philogenetic order makes it clear why the epithelium in the proximal nephron tubule entirely reabsorbs uric acid (a catabolite?) from primary urine and then secretes it again to urine depending on the impairment of biological functions of endoecology (the intercellular medium being contaminated with biological rubbish), the activation of a biological inflammatory reaction, the cellular production of ROS, and the reduction in serum total antioxidant activity. With each biological reaction, there was an increase in the blood content of uric acid as a hydrophilic acceptor of ROS, by actively lowering its secretion into urine. Uric acid is a diagnostic test of inflammation, or rather compensatory

  3. Ergometer error and biological variation in power output in a performance test with three cycle ergometers.

    PubMed

    Paton, C D; Hopkins, W G

    2006-06-01

    When physical performance is monitored with an ergometer, random error arising from the ergometer combines with biological variation from the subject to limit the precision of estimation of performance changes. We report here the contributions of ergometer error and biological variation to the error of measurement in a performance test with two popular cycle ergometers (air-braked Kingcycle, mobile SRM crankset) and a relatively new inexpensive mobile ergometer (PowerTap hub). Eleven well-trained male cyclists performed a familiarization trial followed by three 5-min time trials within 2 wk on a racing cycle fitted with the SRM and PowerTap and mounted on the Kingcycle. Mean power output in each trial was recorded with all ergometers simultaneously. A novel analysis using mixed modelling of log-transformed mean power provided estimates of the standard error of measurement as a coefficient of variation and its components arising from the ergometer and the cyclists. The usual errors of measurement were: Kingcycle 2.2 %, PowerTap 1.5 %, and SRM 1.6 % (90 % confidence limits +/- 1.3). The components of these errors arising purely from the ergometers and the cyclists were: Kingcycle 1.8 %, PowerTap 0.9 %, SRM 1.1 %, and cyclists 1.2 % (+/- 1.5). Thus, ergometer errors and biological variation made substantial contributions to the usual error of measurement. Use of the best ergometers and of test protocols that reduce biological variation would improve monitoring of the small changes that matter to elite athletes.

  4. "Active" drops as phantom models for living cells: a mesoscopic particle-based approach.

    PubMed

    Dallavalle, Marco; Lugli, Francesca; Rapino, Stefania; Zerbetto, Francesco

    2016-04-21

    Drops and biological cells share some morphological features and visco-elastic properties. The modelling of drops by mesoscopic non-atomistic models has been carried out to a high degree of success in recent years. We extend such treatment and discuss a simple, drop-like model to describe the interactions of the outer layer of cells with the surfaces of materials. Cells are treated as active mechanical objects that are able to generate adhesion forces. They appear with their true size and are made of "parcels of fluids" or beads. The beads are described by (very) few quantities/parameters related to fundamental chemical forces such as hydrophilicity and lipophilicity that represent an average of the properties of a patch of material or an area of the cell(s) surface. The investigation of adhesion dynamics, motion of individual cells, and the collective behavior of clusters of cells on materials is possible. In the simulations, the drops become active soft matter objects and different from regular droplets they do not fuse when in contact, their trajectories are not Brownian, and they can be forced "to secrete" molecules, to name some of the properties targeted by the modeling. The behavior that emerges from the simulations allows ascribing some cell properties to their mechanics, which are related to their biological features. PMID:26890581

  5. Time dependence of mesoscopic strain distribution for triaxial woven carbon-fiber-reinforced polymer under creep loading measured by digital image correlation

    NASA Astrophysics Data System (ADS)

    Koyanagi, Jun; Nagayama, Hideo; Yoneyama, Satoru; Aoki, Takahira

    2016-06-01

    This paper presents the time dependence of the mesoscopic strain of a triaxial woven carbon-fiber-reinforced polymer under creep loading measured using digital image correlation (DIC). Two types of DIC techniques were employed for the measurement: conventional subset DIC and mesh DIC. Static tensile and creep tests were carried out, and the time dependence of the mesoscopic strain distribution was investigated by applying these techniques. The ultimate failure of this material is dominated by inter-bundle decohesion caused by relative rigid rotation and relating shear stress. Therefore, these were focused on in the present study. During the creep tests, the fiber directional strain, shear strain, and rotation were monitored using the DIC, and the mechanism for the increase in the specimen's macro-strain over time was investigated based on the results obtained by the DIC measurement.

  6. Inquiry-based laboratory investigations and student performance on standardized tests in biological science

    NASA Astrophysics Data System (ADS)

    Patke, Usha

    Achievement data from the 3rd International Mathematics and Sciences Study and Program for International Student Assessment in science have indicated that Black students from economically disadvantaged families underachieve at alarming rates in comparison to White and economically advantaged peer groups. The study site was a predominately Black, urban school district experiencing underachievement. The purpose of this correlational study was to examine the relationship between students' use of inquiry-based laboratory investigations and their performance on the Biology End of Course Test, as well as to examine the relationship while partialling out the effects of student gender. Constructivist theory formed the theoretical foundation of the study. Students' perceived levels of experience with inquiry-based laboratory investigations were measured using the Laboratory Program Variable Inventory (LPVI) survey. LPVI scores of 256 students were correlated with test scores and were examined by student gender. The Pearson correlation coefficient revealed a small direct correlation between students' experience in inquiry-based laboratory investigation classes and standardized test scores on the Biology EOCT. A partial correlational analysis indicated that the correlation remained after controlling for gender. This study may prompt a change from teacher-centered to student-centered pedagogy at the local site in order to increase academic achievement for all students. The results of this study may also influence administrators and policy makers to initiate local, state, or nationwide curricular development. A change in curriculum may promote social change as students become more competent, and more able, to succeed in life beyond secondary school.

  7. Assessment of a multi-assay biological diagnostic test for mood disorders in a Japanese population.

    PubMed

    Yamamori, Hidenaga; Ishima, Tamaki; Yasuda, Yuka; Fujimoto, Michiko; Kudo, Noriko; Ohi, Kazutaka; Hashimoto, Kenji; Takeda, Masatoshi; Hashimoto, Ryota

    2016-01-26

    The current diagnostic tests for mood disorders, including major depressive disorder (MDD) and bipolar disorder (BD), have limitations. Inflammatory markers, growth factors, and oxidative stress markers are involved in the pathophysiology of mood disorders. A multi-assay biological diagnostic test combining these biomarkers might improve diagnostic efficiency. The plasma levels of soluble tumor necrosis factor receptor 2 (sTNFR2), epidermal growth factor (EGF), and myeloperoxidase were measured in 40 MDD patients, 40 BD patients and 40 controls in a Japanese population. We also investigated the plasma levels of these markers in 40 patients with schizophrenia to determine the utility of these markers in differential diagnosis. The plasma levels of sTNFR2 were significantly higher in BD and schizophrenia patients than in controls. The plasma levels of EGF and myeloperoxidase were significantly higher in patients with BD than in controls. The correct classification rate obtained from discriminant analysis with sTNFR2 and EGF between controls and mood disorders was 69.2%, with a sensitivity and specificity of 62.5% and 82.5%, respectively. The correct classification rate obtained from discriminant analysis with sTNFR2 and EGF between controls and BD was 85.0%, with a sensitivity and specificity of 77.6% and 92.5%, respectively. Our results suggest that sTNFR2 and EGF could be biological markers of BD. Further studies are needed to determine the utility of these markers in diagnostic tests for mood disorders. PMID:26687272

  8. Chemical analysis and biological testing of materials from the EDS coal liquefaction process: a status report

    SciTech Connect

    Later, D.W.; Pelroy, R.A.; Wilson, B.W.

    1984-05-01

    Representative process materials were obtained from the EDS pilot plant for chemical and biological analyses. These materials were characterized for biological activity and chemical composition using a microbial mutagenicity assay and chromatographic and mass spectrometric analytical techniques. The two highest boiling distillation cuts, as well as process solvent (PS) obtained from the bottoms recycle mode operation, were tested for initiation of mouse skin tumorigenicity. All three materials were active; the crude 800/sup 0 +/F cut was substantially more potent than the crude bottoms recycle PS or 750 to 800/sup 0/F distillate cut. Results from chemical analyses showed the EDS materials, in general, to be more highly alkylated and have higher hydroaromatic content than analogous SRC II process materials (no in-line process hydrogenation) used for comparison. In the microbial mutagenicity assays the N-PAC fractions showed greater activity than did the aliphatic hydrocarbon, hydroxy-PAH, or PAH fractions, although mutagenicity was detected in certain PAH fractions by a modified version of the standard microbial mutagenicity assay. Mutagenic activities for the EDS materials were lower, overall, than those for the corresponding materials from the SRC II process. The EDS materials produced under different operational modes had distinguishable differences in both their chemical constituency and biological activity. The primary differences between the EDS materials studied here and their SRC II counterparts used for comparison are most likely attributable to the incorporation of catalytic hydrogenation in the EDS process. 27 references, 28 figures, 27 tables.

  9. Mesoscopic homogenization of semi-insulating GaAs by two-step post growth annealing

    SciTech Connect

    Hoffmann, B.; Jurisch, M.; Koehler, A.; Reinhold, T.; Weinert, B.; Kissinger, G.

    1996-12-31

    Mesoscopic homogenization of the electrical properties of s.i. LEC-GaAs is commonly realized by thermal treatment of the crystals including the steps of dissolution of arsenic precipitates, homogenization of excess As and re-precipitation by creating a controlled supersaturation. Caused by the inhomogeneous distribution of dislocations and the corresponding cellular structure along and across LEC-grown crystals a proper choice of the time-temperature program is necessary to minimize fluctuations of mesoscopic homogeneity. A modified two-step ingot annealing process is demonstrated to ensure the homogeneous distribution of mesoscopic homogeneity.

  10. Molecular and biological diagnostic tests for monitoring benzimidazole resistance in human soil-transmitted helminths.

    PubMed

    Diawara, Aïssatou; Schwenkenbecher, Jan M; Kaplan, Ray M; Prichard, Roger K

    2013-06-01

    In endemic countries with soil-transmitted helminths mass drug administration with albendazole or mebendazole are being implemented as a control strategy. However, it is well known in veterinary helminths that the use of the same benzimidazole drugs can place selection on the β-tubulin gene, leading to resistance. Given the concern that resistance could arise in human soil-transmitted helminths, there is an urgent need to develop accurate diagnostic tools for monitoring resistance. In this study, we developed molecular assays to detect putative resistance genetic changes in Ascaris lumbricoides, Trichuris trichiura, and hookworms, and we optimized an egg hatch assay for the canine hookworm Ancylostoma caninum and applied it to Necator americanus. Both assays were tested on field samples. The molecular assays demonstrated their reproducibility and capacity to detect the presence of worms carrying putative resistance-associated genetic changes. However, further investigations are needed to validate our molecular and biological tests on additional field isolates.

  11. Electrophoresis tests on STS-3 and ground control experiments - A basis for future biological sample selections

    NASA Technical Reports Server (NTRS)

    Morrison, D. R.; Lewis, M. L.

    1982-01-01

    Static zone electrophoresis is an electrokinetic method of separating macromolecules and small particles. However, its application for the isolation of biological cells and concentrated protein solutions is limited by sedimentation and convection. Microgravity eliminates or reduces sedimentation, floatation, and density-driven convection arising from either Joule heating or concentration differences. The advantages of such an environment were first demonstrated in space during the Apollo 14 and 16 missions. In 1975 the Electrophoresis Technology Experiment (MA-011) was conducted during the Apollo-Soyuz Test Project flight. In 1979 a project was initiated to repeat the separations of human kidney cells. One of the major objectives of the Electrophoresis Equipment Verification Tests (EEVT) on STS-3 was to repeat and thereby validate the first successful electrophoretic separation of human kidney cells. Attention is given to the EEVT apparatus, the preflight electrophoresis, and inflight operational results.

  12. Support for the revocation of general safety test regulations in biologics license applications.

    PubMed

    Evans, Dana M; Thorn, Jennifer M; Arch-Douglas, Katherine; Sperry, Justin B; Thompson, Bruce; Davis, Heather L; McCluskie, Michael J

    2016-05-01

    The United States Food and Drug Administration recently removed the requirement for a General Safety Test (GST) for biologics in the Code of Federal Regulations (21 CFR 610.11). The GST, as well as abnormal toxicity (European Pharmacopeia) and innocuity tests (World Health Organization), were designed to test for extraneous toxic contaminants on each product lot intended for human use. Tests require one-week observations for general health and weight following injection of specified volumes of product batches into guinea pigs and mice. At the volumes specified, dose-related toxicity may result when the product is pharmacologically active in rodents. With vaccines, required doses may be > 3 logs higher than intended human dose on a weight-adjusted basis and if an immune modulatory adjuvant is included, systemic immune hyperactivation may cause toxicity. Herein, using the CpG/alum adjuvant combination we evaluated the different test protocols and showed their unsuitability for this adjuvant combination. PMID:26996102

  13. A new biological test utilising the yeast Saccharomyces cerevisiae for the rapid detection of toxic substances in water.

    PubMed

    Rumlova, Lubomira; Dolezalova, Jaroslava

    2012-05-01

    This study evaluates the toxic effects of five substances (atropine, fenitrothion, potassium cyanide, mercuric chloride and lead nitrate) on the yeast Saccharomyces cerevisiae. It describes a new biological toxicity test based on inhibition of S. cerevisiae viability and compares it with two standard toxicity tests based on Daphnia magna mobility inhibition (EN ISO 6341) and Vibrio fischeri bioluminiscence inhibition (EN ISO 11348-2). The new biological test -S. cerevisiae lethal test - is cheaper and 24 times faster than the D. magna test. The test speed is comparable with the V. fischeri test but the new test is more sensitive for some substances. The test indicates reliably the presence of all used toxicants in water in concentrations which are significantly lower than the concentration in toxic or lethal doses for man. Therefore, this new toxicity test could be proposed for rapid detection of toxic substances in water.

  14. [Tests of biological indicators in controling sterilisation processes of autoclaves (author's transl)].

    PubMed

    Holstein, N

    1975-07-01

    For the control of sterilisation processes in autoclaves several biological indicators were examined and compared with native spore samples. The biological indicators were STERIKON (Merck, Darmstadt), KILIT (BBL, USA); the ampulated native spore samples came from Mainz and Berlin, furthermore Bac. subtilis was used on arenaceous quartz. To receive more accurate results and better possibilities for standardization, indicators were not tested in autoclaves but in ultrathermostates. The effect of heat on the viability of ampulated test spores was ascertained by the count of colony formating units on count plates. With two of the tested indicators, KILIT and STERIKON, success of the germicidal process can also be seen by the change of color of the contents of the ampules. Investigations showed ampulated wet spore samples to be totally inefficient, because of their low resistance level, but also suspensios of Bac. subtilis did not meet requirements. Tests of KILIT indicated equally unsatisfactory low levels of heat resistance. Only KTERIKON met the requirements and equalled native spore samples. Since the producer lowered the heat resistance, which was too high initially, by reducing the sowing of spores to 10(2)-10(3) per ml medium of the ampules, the germicidal curve became almost ideal. It has to be mentioned that STERIKON-ampules can only be recommended to ampule-producing-industries. For the control of medicaments in ampules a replacement of native spore samples by STERIKON will only be possible, after the producer has standardized the optimal heat resistance and prevented its decrease while being stored. At present native spore samples are still indispensable - also because they can be widely employed. PMID:811007

  15. In silico model-based inference: a contemporary approach for hypothesis testing in network biology

    PubMed Central

    Klinke, David J.

    2014-01-01

    Inductive inference plays a central role in the study of biological systems where one aims to increase their understanding of the system by reasoning backwards from uncertain observations to identify causal relationships among components of the system. These causal relationships are postulated from prior knowledge as a hypothesis or simply a model. Experiments are designed to test the model. Inferential statistics are used to establish a level of confidence in how well our postulated model explains the acquired data. This iterative process, commonly referred to as the scientific method, either improves our confidence in a model or suggests that we revisit our prior knowledge to develop a new model. Advances in technology impact how we use prior knowledge and data to formulate models of biological networks and how we observe cellular behavior. However, the approach for model-based inference has remained largely unchanged since Fisher, Neyman and Pearson developed the ideas in the early 1900’s that gave rise to what is now known as classical statistical hypothesis (model) testing. Here, I will summarize conventional methods for model-based inference and suggest a contemporary approach to aid in our quest to discover how cells dynamically interpret and transmit information for therapeutic aims that integrates ideas drawn from high performance computing, Bayesian statistics, and chemical kinetics. PMID:25139179

  16. Numerical analysis of wave-induced fluid flow effects related to mesoscopic heterogeneities for realistic models of porous media

    NASA Astrophysics Data System (ADS)

    Rubino, J. G.; Holliger, K.

    2010-12-01

    suitable upscaling procedure. This computational procedure emulates a corresponding pertinent laboratory experiment, in which a representative, mesoscopic-scale rock sample is subjected to a time-harmonic compressibility test. The thus observed complex volume change of the probed sample then allows for estimating the equivalent complex plane-wave modulus, which in turn yields the corresponding effective phase velocity and quality factor as functions of frequency. We apply this approach to a range of canonical models of porous media characterized by realistic, highly heterogeneous distributions of the hydraulic and/or elastic properties as well as varying levels of saturation. In particular, we also compare the results of spatially continuous variations of the medium and fluid properties with equivalent binary parameter distributions. Interestingly, preliminary results provide evidence to suggest that for most heterogeneous porous media characterized by spatially continuous variations of the hydraulic and/or elastic properties, the contribution of wave-induced mesoscopic fluid flow effects to the velocity dispersion and attenuation of seismic waves is likely to be of subordinate importance.

  17. Mesoscopic Patterns of Neural Activity Support Songbird Cortical Sequences

    PubMed Central

    Guitchounts, Grigori; Velho, Tarciso; Lois, Carlos; Gardner, Timothy J.

    2015-01-01

    Time-locked sequences of neural activity can be found throughout the vertebrate forebrain in various species and behavioral contexts. From “time cells” in the hippocampus of rodents to cortical activity controlling movement, temporal sequence generation is integral to many forms of learned behavior. However, the mechanisms underlying sequence generation are not well known. Here, we describe a spatial and temporal organization of the songbird premotor cortical microcircuit that supports sparse sequences of neural activity. Multi-channel electrophysiology and calcium imaging reveal that neural activity in premotor cortex is correlated with a length scale of 100 µm. Within this length scale, basal-ganglia–projecting excitatory neurons, on average, fire at a specific phase of a local 30 Hz network rhythm. These results show that premotor cortical activity is inhomogeneous in time and space, and that a mesoscopic dynamical pattern underlies the generation of the neural sequences controlling song. PMID:26039895

  18. Manipulating mesoscopic multipartite entanglement with atom-light interfaces

    SciTech Connect

    Stasinska, J.; Rodo, C.; Paganelli, S.; Birkl, G.; Sanpera, A.

    2009-12-15

    Entanglement between two macroscopic atomic ensembles induced by measurement on an ancillary light system has proven to be a powerful method for engineering quantum memories and quantum state transfer. Here we investigate the feasibility of such methods for generation, manipulation, and detection of genuine multipartite entanglement (Greenberger-Horne-Zeilinger and clusterlike states) between mesoscopic atomic ensembles without the need of individual addressing of the samples. Our results extend in a nontrivial way the Einstein-Podolsky-Rosen entanglement between two macroscopic gas samples reported experimentally in [B. Julsgaard, A. Kozhekin, and E. Polzik, Nature (London) 413, 400 (2001)]. We find that under realistic conditions, a second orthogonal light pulse interacting with the atomic samples, can modify and even reverse the entangling action of the first one leaving the samples in a separable state.

  19. The interplay between microscopic and mesoscopic structures in complex networks.

    PubMed

    Reichardt, Jörg; Alamino, Roberto; Saad, David

    2011-01-01

    Understanding a complex network's structure holds the key to understanding its function. The physics community has contributed a multitude of methods and analyses to this cross-disciplinary endeavor. Structural features exist on both the microscopic level, resulting from differences between single node properties, and the mesoscopic level resulting from properties shared by groups of nodes. Disentangling the determinants of network structure on these different scales has remained a major, and so far unsolved, challenge. Here we show how multiscale generative probabilistic exponential random graph models combined with efficient, distributive message-passing inference techniques can be used to achieve this separation of scales, leading to improved detection accuracy of latent classes as demonstrated on benchmark problems. It sheds new light on the statistical significance of motif-distributions in neural networks and improves the link-prediction accuracy as exemplified for gene-disease associations in the highly consequential Online Mendelian Inheritance in Man database.

  20. Superconducting properties of a mesoscopic parallelepiped with anisotropic surface conditions

    NASA Astrophysics Data System (ADS)

    Barba-Ortega, J.; Sardella, Edson

    2015-12-01

    We consider a mesoscopic superconducting parallelepiped with different boundary conditions on different parts of the surface, xy, xz and yz surface planes. This is realized by considering different values of the de Gennes extrapolation length b on different surfaces of the sample. Our investigation was carried out by solving the three-dimensional (3D) time dependent Ginzburg-Landau (TDGL) equations. We studied the local magnetic field, order parameter, and both the magnetization and vorticity curves as functions of the external applied magnetic field for different values of b on the surfaces of the sample. We show that this surface anisotropy has very strong influence on the vortex configurations and the magnetization as a function of the external applied magnetic field, both experimentally accessible.

  1. Persistent currents in an ensemble of isolated mesoscopic rings

    SciTech Connect

    Altland, A.; Iida, S.; Mueller-Groelling, A.; Weidenmueller, H.A. )

    1992-10-01

    In this work, the authors calculate the persistent current induced at zero temperature by an external, constant, and homogeneous magnetic field in an ensemble of isolated mesoscopic rings. In each ring, the electrons are assumed to move independently under the influence of a Gaussian white noise random impurity potential. They account for the magnetic field only in terms of the flux threading each ring, without considering the field present in the body of the ring. Particular attention is paid to the constraint of integer particle number on each ring. The authors evaluate the persistent current non-perturbatively, using a generating functional involving Grassmann integration. The magnetic flux threading each ring breaks the orthogonal symmetry of the formalism; forcing us to calculate explicitly the orthogonal-unitary crossover. 24 refs., 1 fig.

  2. Simulating mesoscopic reaction-diffusion systems using the Gillespie algorithm

    SciTech Connect

    Bernstein, David

    2004-12-12

    We examine an application of the Gillespie algorithm to simulating spatially inhomogeneous reaction-diffusion systems in mesoscopic volumes such as cells and microchambers. The method involves discretizing the chamber into elements and modeling the diffusion of chemical species by the movement of molecules between neighboring elements. These transitions are expressed in the form of a set of reactions which are added to the chemical system. The derivation of the rates of these diffusion reactions is by comparison with a finite volume discretization of the heat equation on an unevenly spaced grid. The diffusion coefficient of each species is allowed to be inhomogeneous in space, including discontinuities. The resulting system is solved by the Gillespie algorithm using the fast direct method. We show that in an appropriate limit the method reproduces exact solutions of the heat equation for a purely diffusive system and the nonlinear reaction-rate equation describing the cubic autocatalytic reaction.

  3. Modeling the reversible decoherence of mesoscopic superpositions in dissipative environments

    NASA Astrophysics Data System (ADS)

    Mokarzel, S. G.; Salgueiro, A. N.; Nemes, M. C.

    2002-04-01

    A model is presented to describe the recently proposed experiment [J. Raimond, M. Brune, and S. Haroche, Phys. Rev. Lett 79, 1964 (1997)] in which a mesoscopic superposition of radiation states is prepared in a high-Q cavity that is coupled to a similar resonator. The dynamical coherence loss of such a state in the absence of dissipation is reversible and can be observed in principle. We show how this picture is modified due to the presence of the environmental couplings. Analytical expressions for the experimental conditional probabilities and the linear entropy are given. We conclude that the phenomenon can still be observed provided the ratio between the damping constant and the intercavities coupling does not exceed about a few percent. This observation is favored for superpositions of states with a large overlap.

  4. Acoustic dynamics of network-forming glasses at mesoscopic wavelengths.

    PubMed

    Ferrante, C; Pontecorvo, E; Cerullo, G; Chiasera, A; Ruocco, G; Schirmacher, W; Scopigno, T

    2013-01-01

    The lack of long-range structural order in amorphous solids induces well known thermodynamic anomalies, which are the manifestation of distinct peculiarities in the vibrational spectrum. Although the impact of such anomalies vanishes in the long wavelength, elastic continuum limit, it dominates at length scales comparable to interatomic distances, implying an intermediate transition regime still poorly understood. Here we report a study of such mesoscopic domains by means of a broadband version of picosecond photo-acoustics, developed to coherently generate and detect hypersonic sound waves in the sub-THz region with unprecedented sampling efficiency. We identify a temperature-dependent fractal v(3/2) frequency behaviour of the sound attenuation, pointing to the presence of marginally stable regions and a transition between the two above mentioned limits. The essential features of this behaviour are captured by a theoretical approach based on random spatial variation of the shear modulus, including anharmonic interactions.

  5. Acoustic dynamics of network-forming glasses at mesoscopic wavelengths

    PubMed Central

    Ferrante, C.; Pontecorvo, E.; Cerullo, G.; Chiasera, A.; Ruocco, G.; Schirmacher, W.; Scopigno, T.

    2013-01-01

    The lack of long-range structural order in amorphous solids induces well known thermodynamic anomalies, which are the manifestation of distinct peculiarities in the vibrational spectrum. Although the impact of such anomalies vanishes in the long wavelength, elastic continuum limit, it dominates at length scales comparable to interatomic distances, implying an intermediate transition regime still poorly understood. Here we report a study of such mesoscopic domains by means of a broadband version of picosecond photo-acoustics, developed to coherently generate and detect hypersonic sound waves in the sub-THz region with unprecedented sampling efficiency. We identify a temperature-dependent fractal v3/2 frequency behaviour of the sound attenuation, pointing to the presence of marginally stable regions and a transition between the two above mentioned limits. The essential features of this behaviour are captured by a theoretical approach based on random spatial variation of the shear modulus, including anharmonic interactions. PMID:23653205

  6. On time-dependent counting statistics of mesoscopic electron transport

    NASA Astrophysics Data System (ADS)

    Belzig, Wolfgang

    2009-03-01

    Full counting statistics (FCS) has emerged as a key concept to understand quantum transport in mesoscopic systems like heterostructures, quantum wires, and quantum dots. The knowlegde of the FCS not only enables to predict all measurable zero-frequency quantities accessible via charge detection, but also allows to identify the elementary transport events and the correlations between them. We demonstrate this concept for a standard quantum point contact between normal and/or superconducting leads under dc- and ac-bias. [M. Vanevic, Yu. V. Nazarov, W. Belzig, Phys. Rev. Lett. 99, 076601 (2007)] Finally we address the question, how these concepts can be applied to time-resolved current measurements. [A. Bednorz and W. Belzig, Phys. Rev. Lett. 101, 206803 (2008)

  7. Mesoscopic mechanical resonators as quantum noninertial reference frames

    NASA Astrophysics Data System (ADS)

    Katz, B. N.; Blencowe, M. P.; Schwab, K. C.

    2015-10-01

    An atom attached to a micrometer-scale wire that is vibrating at a frequency ˜100 MHz and with displacement amplitude ˜1 nm experiences an acceleration magnitude ˜109ms -2 , approaching the surface gravity of a neutron star. As one application of such extreme noninertial forces in a mesoscopic setting, we consider a model two-path atom interferometer with one path consisting of the 100 MHz vibrating wire atom guide. The vibrating wire guide serves as a noninertial reference frame and induces an in principle measurable phase shift in the wave function of an atom traversing the wire frame. We furthermore consider the effect on the two-path atom wave interference when the vibrating wire is modeled as a quantum object, hence functioning as a quantum noninertial reference frame. We outline a possible realization of the vibrating wire, atom interferometer using a superfluid helium quantum interference setup.

  8. Electron teleportation via Majorana bound states in a mesoscopic superconductor.

    PubMed

    Fu, Liang

    2010-02-01

    Zero-energy Majorana bound states in superconductors have been proposed to be potential building blocks of a topological quantum computer, because quantum information can be encoded nonlocally in the fermion occupation of a pair of spatially separated Majorana bound states. However, despite intensive efforts, nonlocal signatures of Majorana bound states have not been found in charge transport. In this work, we predict a striking nonlocal phase-coherent electron transfer process by virtue of tunneling in and out of a pair of Majorana bound states. This teleportation phenomenon only exists in a mesoscopic superconductor because of an all-important but previously overlooked charging energy. We propose an experimental setup to detect this phenomenon in a superconductor-quantum-spin-Hall-insulator-magnetic-insulator hybrid system.

  9. Mesoscopic resonating valence bond system on a triple dot.

    PubMed

    Le Hur, Karyn; Recher, Patrik; Dupont, Emilie; Loss, Daniel

    2006-03-17

    We theoretically introduce a mesoscopic pendulum from a triple dot. The pendulum is fastened through a singly occupied dot (spin qubit). Two other strongly capacitively coupled islands form a double-dot charge qubit with one electron in excess oscillating between the two low-energy charge states (1,0) and (0,1). The triple dot is placed between two superconducting leads. Under realistic conditions, the main proximity effect stems from the injection of resonating singlet (valence) bonds on the triple dot. This gives rise to a Josephson current that is charge- and spin-dependent and, as a consequence, exhibits a distinct resonance as a function of the superconducting phase difference. PMID:16605773

  10. Chaste: A test-driven approach to software development for biological modelling

    NASA Astrophysics Data System (ADS)

    Pitt-Francis, Joe; Pathmanathan, Pras; Bernabeu, Miguel O.; Bordas, Rafel; Cooper, Jonathan; Fletcher, Alexander G.; Mirams, Gary R.; Murray, Philip; Osborne, James M.; Walter, Alex; Chapman, S. Jon; Garny, Alan; van Leeuwen, Ingeborg M. M.; Maini, Philip K.; Rodríguez, Blanca; Waters, Sarah L.; Whiteley, Jonathan P.; Byrne, Helen M.; Gavaghan, David J.

    2009-12-01

    Chaste ('Cancer, heart and soft-tissue environment') is a software library and a set of test suites for computational simulations in the domain of biology. Current functionality has arisen from modelling in the fields of cancer, cardiac physiology and soft-tissue mechanics. It is released under the LGPL 2.1 licence. Chaste has been developed using agile programming methods. The project began in 2005 when it was reasoned that the modelling of a variety of physiological phenomena required both a generic mathematical modelling framework, and a generic computational/simulation framework. The Chaste project evolved from the Integrative Biology (IB) e-Science Project, an inter-institutional project aimed at developing a suitable IT infrastructure to support physiome-level computational modelling, with a primary focus on cardiac and cancer modelling. Program summaryProgram title: Chaste Catalogue identifier: AEFD_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFD_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: LGPL 2.1 No. of lines in distributed program, including test data, etc.: 5 407 321 No. of bytes in distributed program, including test data, etc.: 42 004 554 Distribution format: tar.gz Programming language: C++ Operating system: Unix Has the code been vectorised or parallelized?: Yes. Parallelized using MPI. RAM:<90 Megabytes for two of the scenarios described in Section 6 of the manuscript (Monodomain re-entry on a slab or Cylindrical crypt simulation). Up to 16 Gigabytes (distributed across processors) for full resolution bidomain cardiac simulation. Classification: 3. External routines: Boost, CodeSynthesis XSD, CxxTest, HDF5, METIS, MPI, PETSc, Triangle, Xerces Nature of problem: Chaste may be used for solving coupled ODE and PDE systems arising from modelling biological systems. Use of Chaste in two application areas are described in this paper: cardiac electrophysiology and

  11. Biology-inspired microphysiological system approaches to solve the prediction dilemma of substance testing.

    PubMed

    Marx, Uwe; Andersson, Tommy B; Bahinski, Anthony; Beilmann, Mario; Beken, Sonja; Cassee, Flemming R; Cirit, Murat; Daneshian, Mardas; Fitzpatrick, Susan; Frey, Olivier; Gaertner, Claudia; Giese, Christoph; Griffith, Linda; Hartung, Thomas; Heringa, Minne B; Hoeng, Julia; de Jong, Wim H; Kojima, Hajime; Kuehnl, Jochen; Leist, Marcel; Luch, Andreas; Maschmeyer, Ilka; Sakharov, Dmitry; Sips, Adrienne J A M; Steger-Hartmann, Thomas; Tagle, Danilo A; Tonevitsky, Alexander; Tralau, Tewes; Tsyb, Sergej; van de Stolpe, Anja; Vandebriel, Rob; Vulto, Paul; Wang, Jufeng; Wiest, Joachim; Rodenburg, Marleen; Roth, Adrian

    2016-01-01

    The recent advent of microphysiological systems - microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro - is envisaged to enable a global paradigm shift in drug development. An extraordinary US governmental initiative and various dedicated research programs in Europe and Asia have led recently to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis would model various disease stages, and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus, replacing laboratory animal models used currently. Thirty-six experts from academia, industry and regulatory bodies present here the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies, as well as various national and international programs are highlighted. Finally, a roadmap into the future is outlined, to allow for more predictive and regulatory-accepted substance testing on a global scale. PMID:27180100

  12. Biology-inspired microphysiological system approaches to solve the prediction dilemma of substance testing.

    PubMed

    Marx, Uwe; Andersson, Tommy B; Bahinski, Anthony; Beilmann, Mario; Beken, Sonja; Cassee, Flemming R; Cirit, Murat; Daneshian, Mardas; Fitzpatrick, Susan; Frey, Olivier; Gaertner, Claudia; Giese, Christoph; Griffith, Linda; Hartung, Thomas; Heringa, Minne B; Hoeng, Julia; de Jong, Wim H; Kojima, Hajime; Kuehnl, Jochen; Leist, Marcel; Luch, Andreas; Maschmeyer, Ilka; Sakharov, Dmitry; Sips, Adrienne J A M; Steger-Hartmann, Thomas; Tagle, Danilo A; Tonevitsky, Alexander; Tralau, Tewes; Tsyb, Sergej; van de Stolpe, Anja; Vandebriel, Rob; Vulto, Paul; Wang, Jufeng; Wiest, Joachim; Rodenburg, Marleen; Roth, Adrian

    2016-01-01

    The recent advent of microphysiological systems - microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro - is envisaged to enable a global paradigm shift in drug development. An extraordinary US governmental initiative and various dedicated research programs in Europe and Asia have led recently to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis would model various disease stages, and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus, replacing laboratory animal models used currently. Thirty-six experts from academia, industry and regulatory bodies present here the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies, as well as various national and international programs are highlighted. Finally, a roadmap into the future is outlined, to allow for more predictive and regulatory-accepted substance testing on a global scale.

  13. Mesoscopic capacitor and zero-point energy: Poisson's distribution for virtual charges, pressure, and decoherence control

    NASA Astrophysics Data System (ADS)

    Flores, J. C.

    2014-08-01

    Mesoscopic capacitor theory, which includes intrinsic inductive effects from quantum tunneling, is applied to conducting spherical shells. The zero-point pressure and the number of virtual charged pairs are determined assuming a Poisson distribution. They are completely defined by a dimensionless mesoscopic parameter (χc) measuring the average number of virtual pairs per solid angle and carrying mesoscopic information. Fluctuations remain finite and well defined. Connections with usual quantum-field-theory limit enables us to evaluate χc 1.007110. Equivalently, for a mesoscopic parallel-plate capacitor, the shot noise distribution becomes operative with χc 0.94705 as well being related to the density of virtual pairs. Temperature decoherence and capacitor control are discussed by considering typical values of quantum dot devices and Coulomb blockade theory.

  14. Nature of Mesoscopic Organization in Protic Ionic Liquid-Alcohol Mixtures.

    PubMed

    Schroer, Wolffram; Triolo, Alessandro; Russina, Olga

    2016-03-10

    The mesoscopic morphology of mixtures of ethylammonium nitrate, a protic ionic liquid, and n-pentanol is explored for the first time using small angle X-ray scattering as a function of concentration and temperature. Both compounds are amphiphilic and characterized by an extended hydrogen bonding network; however, though macroscopically homogeneous, their mixtures are highly heterogeneous at the mesoscopic spatial scales. Previous structural studies rationalized similar features in related mixtures proposing the existence of large aggregates or micelle- and/or microemulsion-like structures. Here we show that a detailed analysis of the present concentration and temperature resolved experimental data set supports a structural scenario where the mesoscopic heterogeneities are the due to density fluctuations that are precursors of liquid-liquid phase separation. Accordingly no existence of structurally organized aggregates (such as micellar or microemulsion aggregates) is required to account for the mesoscopic heterogeneities detected in this class of binary mixtures. PMID:26895177

  15. The Closed Equilibrated Biological Aquatic System: A 12 months Test of an Artificial Aquatic Ecosystem

    NASA Astrophysics Data System (ADS)

    Blüm, V.; Andriske, M.; Ludwig, Ch.; Paaßen, U.; Voeste, D.

    1999-01-01

    The ``Closed Equilibrated Biological Aquatic System'' (C.E.B.A.S.) is finally disposed for long-term multi-generation experiments with aquatic organisms in a space station. Therefore a minimum operation time of three month is required. It is verified in three versions of laboratory prototypes. The third one passed successfully a 12 months mid-term test in 1995/96 thus demonstrating its high biological stability. The third version of the C.E.B.A.S. consists of a 100 l animal tank, two plant cultivators with a volume of 15 l each with independent illuminations, a 3.0 l semibiological ``mechanical'' filter, a 3.0 l bacteria filter, a heating/cooling device and a dummy filter unit. The live-bearing teleost Xiphophorus helleri is the vertebrate and the pulmonate water snail Biomphalaria glabrata the invertebrate experimental animal in the system. The rootless higher water plant Ceratophyllum demersum is the producer organism. Ammonia oxidizing bacteria and other microorganisms settle in the filters. A simple data acquisition is combined with temperature and plant illumination control. Besides of the space aspects the C.E.B.A.S. proved to be an extremely suitable tool to investigate the organism and subcomponent interactions in a well defined terrestrial aquatic closed ecosystem by providing physical, chemical and biological data which allow an approach to a comprehensive system analysis. Moreover the C.E.B.A.S. is the base for the development of innovative combined animal-plant aquaculture systems for human nutrition on earth which could be implemented into bioregenerative life support systems with a higher degree of complexity suitable for lunar or planetary bases.

  16. The closed equilibrated biological aquatic system: a 12 months test of an artificial aquatic ecosystem.

    PubMed

    Blum, V; Andriske, M; Ludwig, C h; Paassen, U; Voeste, D

    1999-01-01

    The Closed Equilibrated Biological Aquatic System" (C.E.B.A.S.) is finally disposed for long-term multi-generation experiments with aquatic organisms in a space station. Therefore a minimum operation time of three months is required. It is verified in three versions of laboratory prototypes. The third one passed successfully a 12 months mid-term test in 1995/96 thus demonstrating its high biological stability. The third version of the C.E.B.A.S. consists of a 100 l animal tank, two plant cultivators with a volume of 15 l each with independent illuminations, a 3.0 l semibiological "mechanical" filter, a 3.0 l bacteria filter, a heating/cooling device and a dummy filter unit. The live-bearing teleost Xiphophorus helleri is the vertebrate and the pulmonate water snail Biomphalana glabrata the invertebrate experimental animal in the system. The rootless higher water plant Ceratophyllum demersum is the producer organism. Ammonia oxidizing bacteria and other microorganisms settle in the filters. A sample data acquisition is combined with temperature and plant illumination control. Besides of the space aspects the C.E.B.A.S. proved to be an extremely suitable tool to investigate the organism and subcomponent interactions in a well defined terrestrial aquatic closed ecosystem by providing physical, chemical and biological data which allow an approach to a comprehensive system analysis. Moreover the C.E.B.A.S. is the base for the development of innovative combined animal-plant aquaculture systems for human nutrition on earth which could be implemented into bioregenerative life support systems with a higher degree of complexity suitable for lunar or planetary bases.

  17. Comparison between Lagrangian and mesoscopic Eulerian modelling approaches for inertial particles suspended in decaying isotropic turbulence

    NASA Astrophysics Data System (ADS)

    Kaufmann, A.; Moreau, M.; Simonin, O.; Helie, J.

    2008-06-01

    The purpose of this paper is to evaluate the accuracy of the mesoscopic approach proposed by Février et al. [P. Février, O. Simonin, K.D. Squires, Partitioning of particle velocities in gas-solid turbulent flows into a continuous field and a spatially uncorrelated random distribution: theoretical formalism and numerical study, J. Fluid Mech. 533 (2005) 1-46] by comparison against the Lagrangian approach for the simulation of an ensemble of non-colliding particles suspended in a decaying homogeneous isotropic turbulence given by DNS. The mesoscopic Eulerian approach involves to solve equations for a few particle PDF moments: number density, mesoscopic velocity, and random uncorrelated kinetic energy (RUE), derived from particle flow ensemble averaging conditioned by the turbulent fluid flow realization. In addition, viscosity and diffusivity closure assumptions are used to compute the unknown higher order moments which represent the mesoscopic velocity and RUE transport by the uncorrelated velocity component. A detailed comparison between the two approaches is carried out for two different values of the Stokes number based on the initial fluid Kolmogorov time scale, St=0.17 and 2.2. In order to perform reliable comparisons for the RUE local instantaneous distribution and for the mesoscopic kinetic energy spectrum, the error due to the computation method of mesoscopic quantities from Lagrangian simulation results is evaluated and minimized. A very good agreement is found between the mesoscopic Eulerian and Lagrangian predictions for the small particle Stokes number case corresponding to the smallest particle inertia. For larger particle inertia, a bulk viscous term is included in the mesoscopic velocity governing equation to avoid spurious spatial oscillation that may arise due to the inability of the numerical scheme to resolve sharp number density gradients. As a consequence, for St=2.2, particle number density and RUE spatial distribution predicted by the

  18. High Resolution Higher Energy X-ray Microscope for Mesoscopic Materials

    NASA Astrophysics Data System (ADS)

    Snigireva, I.; Snigirev, A.

    2013-10-01

    We developed a novel X-ray microscopy technique to study mesoscopically structured materials, employing compound refractive lenses. The easily seen advantage of lens-based methodology is the possibility to retrieve high resolution diffraction pattern and real-space images in the same experimental setup. Methodologically the proposed approach is similar to the studies of crystals by high resolution transmission electron microscopy. The proposed microscope was applied for studying of mesoscopic materials such as natural and synthetic opals, inverted photonic crystals.

  19. A test of biological trait analysis with nematodes and an anthropogenic stressor.

    PubMed

    Mitwally, Hanan M; Fleeger, John W

    2016-03-01

    Aquatic ecosystems are fundamentally altered by nutrient enrichment, and effective monitoring tools are needed to detect biological responses especially in the early stages of eutrophication. We tested the utility of biological trait analysis (BTA) to quantify the temporal responses of nematodes inhabiting salt marsh creeks that were experimentally enriched with nutrients for 6 years. Feeding, body shape, and tail shape traits were characterized on >6000 nematodes from annual samples from enriched and non-enriched sites. Here, we ask if trait combinations are more effective than single traits in detecting the magnitude and rate of change. We also sought to identify combinations of traits that best distinguish natural from nutrient-induced variation. BTA revealed that feeding, body shape, and all traits combined equally detected the response to nutrient enrichment. Compared to single traits however, BTAs were more sensitive to temporal trends and better distinguished natural variation from the response to nutrient enrichment. Tail shape traits (that might respond to altered sediment texture or geochemistry) were not affected by enrichment, and feeding traits yielded the greatest difference between enriched and reference communities indicating that changes in food resources drove responses. Feeding traits provided the highest quality information content in our study, and the use of feeding traits alone may adequately identify anthropogenic effects in many studies. However, we caution that body shape, tail shape, and feeding traits were strongly interrelated at our study site, and a diversity of trait groups may increase the information content of BTAs in more diverse habitats.

  20. A test of biological trait analysis with nematodes and an anthropogenic stressor.

    PubMed

    Mitwally, Hanan M; Fleeger, John W

    2016-03-01

    Aquatic ecosystems are fundamentally altered by nutrient enrichment, and effective monitoring tools are needed to detect biological responses especially in the early stages of eutrophication. We tested the utility of biological trait analysis (BTA) to quantify the temporal responses of nematodes inhabiting salt marsh creeks that were experimentally enriched with nutrients for 6 years. Feeding, body shape, and tail shape traits were characterized on >6000 nematodes from annual samples from enriched and non-enriched sites. Here, we ask if trait combinations are more effective than single traits in detecting the magnitude and rate of change. We also sought to identify combinations of traits that best distinguish natural from nutrient-induced variation. BTA revealed that feeding, body shape, and all traits combined equally detected the response to nutrient enrichment. Compared to single traits however, BTAs were more sensitive to temporal trends and better distinguished natural variation from the response to nutrient enrichment. Tail shape traits (that might respond to altered sediment texture or geochemistry) were not affected by enrichment, and feeding traits yielded the greatest difference between enriched and reference communities indicating that changes in food resources drove responses. Feeding traits provided the highest quality information content in our study, and the use of feeding traits alone may adequately identify anthropogenic effects in many studies. However, we caution that body shape, tail shape, and feeding traits were strongly interrelated at our study site, and a diversity of trait groups may increase the information content of BTAs in more diverse habitats. PMID:26846290

  1. Novel Biological Approaches for Testing the Contributions of Single DSBs and DSB Clusters to the Biological Effects of High LET Radiation.

    PubMed

    Mladenova, Veronika; Mladenov, Emil; Iliakis, George

    2016-01-01

    The adverse biological effects of ionizing radiation (IR) are commonly attributed to the generation of DNA double-strand breaks (DSBs). IR-induced DSBs are generated by clusters of ionizations, bear damaged terminal nucleotides, and frequently comprise base damages and single-strand breaks in the vicinity generating a unique DNA damage-clustering effect that increases DSB "complexity." The number of ionizations in clusters of different radiation modalities increases with increasing linear energy transfer (LET), and is thought to determine the long-known LET-dependence of the relative biological effectiveness (RBE). Multiple ionizations may also lead to the formation of DSB clusters, comprising two or more DSBs that destabilize chromatin further and compromise overall processing. DSB complexity and DSB-cluster formation are increasingly considered in the development of mathematical models of radiation action, which are then "tested" by fitting available experimental data. Despite a plethora of such mathematical models the ultimate goal, i.e., the "a priori" prediction of the radiation effect, has not yet been achieved. The difficulty partly arises from unsurmountable difficulties in testing the fundamental assumptions of such mathematical models in defined biological model systems capable of providing conclusive answers. Recently, revolutionary advances in methods allowing the generation of enzymatic DSBs at random or in well-defined locations in the genome, generate unique testing opportunities for several key assumptions frequently fed into mathematical modeling - including the role of DSB clusters in the overall effect. Here, we review the problematic of DSB-cluster formation in radiation action and present novel biological technologies that promise to revolutionize the way we address the biological consequences of such lesions. We describe new ways of exploiting the I-SceI endonuclease to generate DSB-clusters at random locations in the genome and describe the

  2. Impact of hydrogen peroxide oxygen transfer tests on the performance of the biological nutrient removal process.

    PubMed

    Mahendraker, V; Mavinic, D S; Rabinowitz, B

    2002-02-01

    Knowledge of in-process oxygen transfer is essential to the optimum design and operation of aeration systems in activated sludge processes. In this study, non-steady state H2O2 oxygen transfer tests were performed in a laboratory scale, University of Cape Town configuration biological nutrient removal process (BNR) to measure the in-process oxygen transfer rates. Given the small quantity (about 1 ml @30% concentration) of H2O2 used in the aerobic reactor with a mixed liquor volume of 161 (total system working volume of 33.65 l), no effect on the process performance itself was expected. However, the process performance data obtained indicated results to the contrary. Use of H2O2 in measuring process oxygen transfer rates may not be suitable for BNR processes, as all the major process performance indicators (carbon, nitrogen and phosphorus removal by the system and carbon uptake and phosphorus release in the anaerobic zone) were negatively affected. Evidence in thiswork leads to the conclusion that external addition of H2O2 leads to excessive production of the hydroxyl radical. Since microorganisms do not have enzyme systems capable of acting upon this additional reactive radical, it resulted in loss of process performance. It is also possible that H2O2 could have upset the normal aerobic respiration process by introducing oxidative stress conditions on the catalase, peroxidase and superoxide dismutase enzymes that deal with other oxygen radicals generated as part of the overall process of reducing oxygen to water. Any test that interferes with the system in which the test is being performed is suspect. Therefore, in light of these results, the H2O2 method to test in-process oxygen transfer should be re-evaluated.

  3. Magnetic response measurements of mesoscopic superconducting and normal metal rings

    NASA Astrophysics Data System (ADS)

    Bluhm, Hendrik

    The main part of this thesis reports three experiments on the magnetic response of mesoscopic superconducting and normal metal rings using a scanning SQUID microscope. The first experiment explores the magnetic response and fluxoid transitions of superconducting, mesoscopic bilayer aluminum rings in the presence of two coupled order parameters arising from the layered structure. For intermediate couplings, metastable states that have different phase winding numbers around the ring in each of the two order parameters were observed. Larger coupling locks the relative phase, so that the two order parameters are only manifest in the temperature dependence of the response. With increasing proximitization, this signature gradually disappears. The data can be described with a two-order-parameter Ginzburg-Landau theory. The second experiment concentrates on fluxoid transitions in similar, but single-layer rings. Near the critical temperature, the transitions, which are induced by applying a flux to the ring, only admit a single fluxoid at a time. At lower temperatures, several fluxoids enter or leave at once, and the final state approaches the ground state. Currently available theoretical frameworks cannot quantitatively explain the data. Heating and quasiparticle diffusion are likely important for a quantitative understanding of this experiment, which could provide a model system for studying the nonlinear dynamics of superconductors far from equilibrium. The third and most important scanning SQUID study concerns 33 individual mesoscopic gold rings. All measured rings show a paramagnetic linear susceptibility and a poorly understood anomaly around zero field, both of which are likely due to unpaired defect spins. The response of sufficiently small rings also has a component that is periodic in the flux through the ring, with a period close to h/e. Its amplitude varies in sign and magnitude from ring to ring, and its typical value and temperature dependence agree with

  4. Novel Biological Approaches for Testing the Contributions of Single DSBs and DSB Clusters to the Biological Effects of High LET Radiation

    PubMed Central

    Mladenova, Veronika; Mladenov, Emil; Iliakis, George

    2016-01-01

    The adverse biological effects of ionizing radiation (IR) are commonly attributed to the generation of DNA double-strand breaks (DSBs). IR-induced DSBs are generated by clusters of ionizations, bear damaged terminal nucleotides, and frequently comprise base damages and single-strand breaks in the vicinity generating a unique DNA damage-clustering effect that increases DSB “complexity.” The number of ionizations in clusters of different radiation modalities increases with increasing linear energy transfer (LET), and is thought to determine the long-known LET-dependence of the relative biological effectiveness (RBE). Multiple ionizations may also lead to the formation of DSB clusters, comprising two or more DSBs that destabilize chromatin further and compromise overall processing. DSB complexity and DSB-cluster formation are increasingly considered in the development of mathematical models of radiation action, which are then “tested” by fitting available experimental data. Despite a plethora of such mathematical models the ultimate goal, i.e., the “a priori” prediction of the radiation effect, has not yet been achieved. The difficulty partly arises from unsurmountable difficulties in testing the fundamental assumptions of such mathematical models in defined biological model systems capable of providing conclusive answers. Recently, revolutionary advances in methods allowing the generation of enzymatic DSBs at random or in well-defined locations in the genome, generate unique testing opportunities for several key assumptions frequently fed into mathematical modeling – including the role of DSB clusters in the overall effect. Here, we review the problematic of DSB-cluster formation in radiation action and present novel biological technologies that promise to revolutionize the way we address the biological consequences of such lesions. We describe new ways of exploiting the I-SceI endonuclease to generate DSB-clusters at random locations in the genome and

  5. Dosimetric and biological results from the Bacillus subtilis Biostack experiment with the Apollo-Soyuz Test Project.

    PubMed

    Facius, R; Bucker, H; Horneck, G; Reitz, G; Schafer, M

    1979-01-01

    The evaluation of the Bacillus subtilis experiment has been completed. The biological and the physical results for this part of the Apollo-Soyuz Test Project (ASTP) Biostack experiment are given. This comprises dosimetric data for the cosmic radiation at that orbit as well as biological findings from two types of plastic detectors. Further, the frequency distributions of the physical quantities atomic number, energy and energy loss of the heavy ions within the sample of spores hit are presented. The biological hazard presented by cosmic HZE-particles has been much underestimated.

  6. Dosimetric and biological results from the Bacillus subtilis Biostack experiment with the Apollo-Soyuz Test Project.

    PubMed

    Facius, R; Bucker, H; Horneck, G; Reitz, G; Schafer, M

    1979-01-01

    The evaluation of the Bacillus subtilis experiment has been completed. The biological and the physical results for this part of the Apollo-Soyuz Test Project (ASTP) Biostack experiment are given. This comprises dosimetric data for the cosmic radiation at that orbit as well as biological findings from two types of plastic detectors. Further, the frequency distributions of the physical quantities atomic number, energy and energy loss of the heavy ions within the sample of spores hit are presented. The biological hazard presented by cosmic HZE-particles has been much underestimated. PMID:12001965

  7. Hearing Tests on Mobile Devices: Evaluation of the Reference Sound Level by Means of Biological Calibration

    PubMed Central

    Kipiński, Lech; Grysiński, Tomasz; Kręcicki, Tomasz

    2016-01-01

    Background Hearing tests carried out in home setting by means of mobile devices require previous calibration of the reference sound level. Mobile devices with bundled headphones create a possibility of applying the predefined level for a particular model as an alternative to calibrating each device separately. Objective The objective of this study was to determine the reference sound level for sets composed of a mobile device and bundled headphones. Methods Reference sound levels for Android-based mobile devices were determined using an open access mobile phone app by means of biological calibration, that is, in relation to the normal-hearing threshold. The examinations were conducted in 2 groups: an uncontrolled and a controlled one. In the uncontrolled group, the fully automated self-measurements were carried out in home conditions by 18- to 35-year-old subjects, without prior hearing problems, recruited online. Calibration was conducted as a preliminary step in preparation for further examination. In the controlled group, audiologist-assisted examinations were performed in a sound booth, on normal-hearing subjects verified through pure-tone audiometry, recruited offline from among the workers and patients of the clinic. In both the groups, the reference sound levels were determined on a subject’s mobile device using the Bekesy audiometry. The reference sound levels were compared between the groups. Intramodel and intermodel analyses were carried out as well. Results In the uncontrolled group, 8988 calibrations were conducted on 8620 different devices representing 2040 models. In the controlled group, 158 calibrations (test and retest) were conducted on 79 devices representing 50 models. Result analysis was performed for 10 most frequently used models in both the groups. The difference in reference sound levels between uncontrolled and controlled groups was 1.50 dB (SD 4.42). The mean SD of the reference sound level determined for devices within the same model

  8. Mesoscopic structure of neuronal tracts from time-dependent diffusion.

    PubMed

    Burcaw, Lauren M; Fieremans, Els; Novikov, Dmitry S

    2015-07-01

    Interpreting brain diffusion MRI measurements in terms of neuronal structure at a micrometer level is an exciting unresolved problem. Here we consider diffusion transverse to a bundle of fibers, and show theoretically, as well as using Monte Carlo simulations and measurements in a phantom made of parallel fibers mimicking axons, that the time dependent diffusion coefficient approaches its macroscopic limit slowly, in a (ln t)/t fashion. The logarithmic singularity arises due to short range disorder in the fiber packing. We identify short range disorder in axonal fibers based on histological data from the splenium, and argue that the time dependent contribution to the overall diffusion coefficient from the extra-axonal water dominates that of the intra-axonal water. This dominance may explain the bias in measuring axon diameters in clinical settings. The short range disorder is also reflected in the asymptotically linear frequency dependence of the diffusion coefficient measured with oscillating gradients, in agreement with recent experiments. Our results relate the measured diffusion to the mesoscopic structure of neuronal tissue, uncovering the sensitivity of diffusion metrics to axonal arrangement within a fiber tract, and providing an alternative interpretation of axonal diameter mapping techniques.

  9. Concentration fluctuations in a mesoscopic oscillating chemical reaction system

    PubMed Central

    Qian, Hong; Saffarian, Saveez; Elson, Elliot L.

    2002-01-01

    Under sustained pumping, kinetics of macroscopic nonlinear biochemical reaction systems far from equilibrium either can be in a stationary steady state or can execute sustained oscillations about a fixed mean. For a system of two dynamic species X and Y, the concentrations nx and ny will be constant or will repetitively trace a closed loop in the (nx, ny) phase plane, respectively. We study a mesoscopic system with nx and ny very small; hence the occurrence of random fluctuations modifies the deterministic behavior and the law of mass action is replaced by a stochastic model. We show that nx and ny execute cyclic random walks in the (nx, ny) plane whether or not the deterministic kinetics for the corresponding macroscopic system represents a steady or an oscillating state. Probability distributions and correlation functions for nx(t) and ny(t) show quantitative but not qualitative differences between states that would appear as either oscillating or steady in the corresponding macroscopic systems. A diffusion-like equation for probability P(nx, ny, t) is obtained for the two-dimensional Brownian motion in the (nx, ny) phase plane. In the limit of large nx, ny, the deterministic nonlinear kinetics derived from mass action is recovered. The nature of large fluctuations in an oscillating nonequilibrium system and the conceptual difference between “thermal stochasticity” and “temporal complexity” are clarified by this analysis. This result is relevant to fluorescence correlation spectroscopy and metabolic reaction networks. PMID:12124397

  10. Energy transfer in mesoscopic vibrational systems enabled by eigenfrequency fluctuations

    NASA Astrophysics Data System (ADS)

    Atalaya, Juan

    Energy transfer between low-frequency vibrational modes can be achieved by means of nonlinear coupling if their eigenfrequencies fulfill certain nonlinear resonance conditions. Because of the discreteness of the vibrational spectrum at low frequencies, such conditions may be difficult to satisfy for most low-frequency modes in typical mesoscopic vibrational systems. Fluctuations of the vibrational eigenfrequencies can also be relatively strong in such systems. We show that energy transfer between modes can occur in the absence of nonlinear resonance if frequency fluctuations are allowed. The case of three modes with cubic nonlinear coupling and no damping is particularly interesting. It is found that the system has a non-thermal equilibrium state which depends only on the initial conditions. The rate at which the system approaches to such state is determined by the parameters such as the noise strength and correlation time, the nonlinearity strength and the detuning from exact nonlinear resonance. We also discuss the case of many weakly coupled modes. Our results shed light on the problem of energy relaxation of low-frequency vibrational modes into the continuum of high-frequency vibrational modes. The results have been obtained with Mark Dykman. Alternative email: jatalaya2012@gmail.com.

  11. Mesoscopic nonequilibrium thermodynamics approach to non-Debye dielectric relaxation

    NASA Astrophysics Data System (ADS)

    Híjar, Humberto; Méndez-Bermúdez, J. G.; Santamaría-Holek, Iván

    2010-02-01

    Mesoscopic nonequilibrium thermodynamics is used to formulate a model describing nonhomogeneous and non-Debye dielectric relaxation. The model is presented in terms of a Fokker-Planck equation for the probability distribution of noninteracting polar molecules in contact with a heat bath and in the presence of an external time-dependent electric field. Memory effects are introduced in the Fokker-Planck description through integral relations containing memory kernels, which in turn are used to establish a connection with fractional Fokker-Planck descriptions. The model is developed in terms of the evolution equations for the first two moments of the distribution function. These equations are solved by following a perturbative method from which the expressions for the complex susceptibilities are obtained as a function of the frequency and the wave number. Different memory kernels are considered and used to compare with experiments of dielectric relaxation in glassy systems. For the case of Cole-Cole relaxation, we infer the distribution of relaxation times and its relation with an effective distribution of dipolar moments that can be attributed to different segmental motions of the polymer chains in a melt.

  12. Analysing DNA structural parameters using a mesoscopic model

    NASA Astrophysics Data System (ADS)

    Amarante, Tauanne D.; Weber, Gerald

    2014-03-01

    The Peyrard-Bishop model is a mesoscopic approximation to model DNA and RNA molecules. Several variants of this model exists, from 3D Hamiltonians, including torsional angles, to simpler 2D versions. Currently, we are able to parametrize the 2D variants of the model which allows us to extract important information about the molecule. For example, with this technique we were able recently to obtain the hydrogen bonds of RNA from melting temperatures, which previously were obtainable only from NMR measurements. Here, we take the 3D torsional Hamiltonian and set the angles to zero. Curiously, in doing this we do not recover the traditional 2D Hamiltonians. Instead, we obtain a different 2D Hamiltonian which now includes a base pair step distance, commonly known as rise. A detailed knowledge of the rise distance is important as it determines the overall length of the DNA molecule. This 2D Hamiltonian provides us with the exciting prospect of obtaining DNA structural parameters from melting temperatures. Our results of the rise distance at low salt concentration are in good qualitative agreement with those from several published x-ray measurements. We also found an important dependence of the rise distance with salt concentration. In contrast to our previous calculations, the elastic constants now show little dependence with salt concentrations which appears to be closer to what is seen experimentally in DNA flexibility experiments.

  13. Universality of Shot Noise in Mesoscopic Diffusive Conductors.

    NASA Astrophysics Data System (ADS)

    Sukhorukov, Eugene; Loss, Daniel

    1998-03-01

    Shot noise is the time-dependent fluctuations in the electrical current caused by the discreteness of the electron charge. In mesoscopic conductors the shot noise is suppressed below the noise of a Poisson process due to correlations in the electron transmission imposed by the Pauli principle. In diffusive conductors with purely elastic scattering the suppression factor is 1/3, and in the case of strong electron-electron scattering it is √3/4 (C.W.J. Beenakker and M. Büttiker, Phys. Rev. B46, 1889 (1992); K.E. Nagaev, Phys. Lett. A169, 103 (1992); Phys. Rev. B52, 4740 (1995)). Subsequently, it has been proven by Nazarov that the 1/3 suppression is universal and holds for an arbitrary two-terminal geometry of the conductor and distribution of impurities. Using a different approach, we confirm the universality of the 1/3 and prove the universality of the √3/4 suppressions. A possible generalization of our results to the case of multiterminal conductors is discussed.

  14. Mesoscopic Higher Regularity and Subadditivity in Elliptic Homogenization

    NASA Astrophysics Data System (ADS)

    Armstrong, Scott; Kuusi, Tuomo; Mourrat, Jean-Christophe

    2016-10-01

    We introduce a new method for obtaining quantitative results in stochastic homogenization for linear elliptic equations in divergence form. Unlike previous works on the topic, our method does not use concentration inequalities (such as Poincaré or logarithmic Sobolev inequalities in the probability space) and relies instead on a higher ( C k , k ≥ 1) regularity theory for solutions of the heterogeneous equation, which is valid on length scales larger than a certain specified mesoscopic scale. This regularity theory, which is of independent interest, allows us to, in effect, localize the dependence of the solutions on the coefficients and thereby accelerate the rate of convergence of the expected energy of the cell problem by a bootstrap argument. The fluctuations of the energy are then tightly controlled using subadditivity. The convergence of the energy gives control of the scaling of the spatial averages of gradients and fluxes (that is, it quantifies the weak convergence of these quantities), which yields, by a new "multiscale" Poincaré inequality, quantitative estimates on the sublinearity of the corrector.

  15. Mesoscopic structure of neuronal tracts from time-dependent diffusion

    PubMed Central

    Burcaw, Lauren M.; Fieremans, Els; Novikov, Dmitry S.

    2015-01-01

    Interpreting brain diffusion MRI measurements in terms of neuronal structure at a micrometer level is an exciting unresolved problem. Here we consider diffusion transverse to a bundle of fibers, and show theoretically, as well as using Monte Carlo simulations and measurements in a phantom made of parallel fibers mimicking axons, that the time dependent diffusion coefficient approaches its macroscopic limit slowly, in a (lnt)/t fashion. The logarithmic singularity arises due to short range disorder in the fiber packing. We identify short range disorder in axonal fibers based on histological data from the splenium, and argue that the time dependent contribution to the overall diffusion coefficient from the extra-axonal water dominates that of the intra-axonal water. This dominance may explain the bias in measuring axon diameters in clinical settings. The short range disorder is also reflected in the linear frequency dependence of the diffusion coefficient measured with oscillating gradients, in agreement with recent experiments. Our results relate the measured diffusion to the mesoscopic structure of neuronal tissue, uncovering the sensitivity of diffusion metrics to axonal arrangement within a fiber tract, and providing an alternative interpretation of axonal diameter mapping techniques. PMID:25837598

  16. Superparamagnetism-induced mesoscopic electron focusing in topological insulators

    NASA Astrophysics Data System (ADS)

    Sessi, P.; Rüßmann, P.; Bathon, T.; Barla, A.; Kokh, K. A.; Tereshchenko, O. E.; Fauth, K.; Mahatha, S. K.; Valbuena, M. A.; Godey, S.; Glott, F.; Mugarza, A.; Gargiani, P.; Valvidares, M.; Long, N. H.; Carbone, C.; Mavropoulos, P.; Blügel, S.; Bode, M.

    2016-08-01

    Recently it has been shown that surface magnetic doping of topological insulators induces backscattering of Dirac states which are usually protected by time-reversal symmetry [Sessi et al., Nat. Commun. 5, 5349 (2014), 10.1038/ncomms6349]. Here we report on quasiparticle interference measurements where, by improved Fermi level tuning, strongly focused interference patterns on surface Mn-doped Bi2Te3 could be directly observed by means of scanning tunneling microscopy at 4 K. Ab initio and model calculations reveal that their mesoscopic coherence relies on two prerequisites: (i) a hexagonal Fermi surface with large parallel segments (nesting) and (ii) magnetic dopants which couple to a high-spin state. Indeed, x-ray magnetic circular dichroism shows superparamagnetism even at very dilute Mn concentrations. Our findings provide evidence of strongly anisotropic Dirac-fermion-mediated interactions and demonstrate how spin information can be transmitted over long distances, allowing the design of experiments and devices based on coherent quantum effects in topological insulators.

  17. Programmable Mesoscopic Architecture using Directionally-Functionalized Nanoparticles

    NASA Astrophysics Data System (ADS)

    Halverson, Jonathan; Tkachenko, Alexei

    2013-03-01

    Nanoparticles that have been isotropically-functionalized with complementary DNA strands have been shown to self-assemble into a variety of crystalline morphologies. To produce a nanoparticle assembly with a finite size and arbitrary shape, the NPs must be endowed with directional interactions. Directionally-functionalized nanoparticles (dfNPs) can be constructed by grafting ssDNA at specific locations on the particles, and proof-of-principle experiments have successfully demonstrated the self-assembly of such particles. Using these building blocks we have previously demonstrated with numerical simulations that a variety of target mesoscopic structures, each with a programmed local morphology and complex overall shape, can be self-assembled in near perfect yield. Here we present a model to describe the kinetics of assembly of a structure composed on dfNPs. The capability to produce these structures can be utilized in a variety of applications where bottom-up construction of 3D nano-objects with well-defined composition and architecture is required (e.g., nanoplasmonics, nanomedicine, metamaterials). Research carried out in whole at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  18. Emission of entangled Kramers pairs from a helical mesoscopic capacitor

    NASA Astrophysics Data System (ADS)

    Dolcetto, Giacomo; Schmidt, Thomas L.

    2016-08-01

    The realization of single-electron sources in integer quantum Hall systems has paved the way for exploring electronic quantum optics experiments in solid-state devices. In this paper, we characterize a single Kramers pair emitter realized by a driven antidot embedded in a two-dimensional topological insulator, where spin-momentum locked edge states can be exploited for generating entanglement. Contrary to previous proposals, the antidot is coupled to both edges of a quantum spin Hall bar, thus enabling this mesoscopic capacitor to emit an entangled two-electron state. We study the concurrence C of the emitted state and the efficiency F of its emission as a function of the different spin-preserving and spin-flipping tunnel couplings of the antidot with the edges. We show that the efficiency remains very high (F ≥50 % ) even for maximally entangled states (C =1 ). We also discuss how the entanglement can be probed by means of noise measurements and violation of the Clauser-Horne-Shimony-Holt inequality.

  19. Mesoscopic structure formation in condensed matter due to vacuum fluctuations

    NASA Astrophysics Data System (ADS)

    Sen, Siddhartha; Gupta, Kumar S.; Coey, J. M. D.

    2015-10-01

    An observable influence of zero-point fluctuations of the vacuum electromagnetic field on bound electrons is well known in the hydrogen atom, where it produces the Lamb shift. Here, we adapt an approach used to explain the Lamb shift in terms of a slight expansion of the orbits due to interaction with the zero-point field and apply it to assemblies of N electrons that are modeled as independent atomically bound two-level systems. The effect is to stabilize a collective ground-state energy, which leads to a prediction of novel effects at room temperature for quasi-two-dimensional systems over a range of parameters in the model, namely, N , the two-level excitation energy ℏ ω and the ionization energy ℏ ω +ɛ . Some mesoscopic systems where these effects may be observable include water sheaths on protein or DNA, surfaces of gaseous nanobubbles, and the magnetic response of inhomogeneous, electronically dilute oxides. No such effects are envisaged for uniform three-dimensional systems.

  20. Examples of testing global identifiability of biological and biomedical models with the DAISY software.

    PubMed

    Saccomani, Maria Pia; Audoly, Stefania; Bellu, Giuseppina; D'Angiò, Leontina

    2010-04-01

    DAISY (Differential Algebra for Identifiability of SYstems) is a recently developed computer algebra software tool which can be used to automatically check global identifiability of (linear and) nonlinear dynamic models described by differential equations involving polynomial or rational functions. Global identifiability is a fundamental prerequisite for model identification which is important not only for biological or medical systems but also for many physical and engineering systems derived from first principles. Lack of identifiability implies that the parameter estimation techniques may not fail but any obtained numerical estimates will be meaningless. The software does not require understanding of the underlying mathematical principles and can be used by researchers in applied fields with a minimum of mathematical background. We illustrate the DAISY software by checking the a priori global identifiability of two benchmark nonlinear models taken from the literature. The analysis of these two examples includes comparison with other methods and demonstrates how identifiability analysis is simplified by this tool. Thus we illustrate the identifiability analysis of other two examples, by including discussion of some specific aspects related to the role of observability and knowledge of initial conditions in testing identifiability and to the computational complexity of the software. The main focus of this paper is not on the description of the mathematical background of the algorithm, which has been presented elsewhere, but on illustrating its use and on some of its more interesting features. DAISY is available on the web site http://www.dei.unipd.it/ approximately pia/.

  1. Examples of Testing Global Identifiability of Biological and Biomedical Models with the DAISY Software

    PubMed Central

    Saccomani, Maria Pia; Audoly, Stefania; Bellu, Giuseppina; D’Angiò, Leontina

    2010-01-01

    DAISY (Differential Algebra for Identifiability of SYstems) is a recently developed computer algebra software tool which can be used to automatically check global identifiability of (linear and) nonlinear dynamic models described by differential equations involving polynomial or rational functions. Global identifiability is a fundamental prerequisite for model identification which is important not only for biological or medical systems but also for many physical and engineering systems derived from first principles. Lack of identifiability implies that the parameter estimation techniques may not fail but any obtained numerical estimates will be meaningless. The software does not require understanding of the underlying mathematical principles and can be used by researchers in applied fields with a minimum of mathematical background. We illustrate the DAISY software by checking the a priori global identifiability of two benchmark nonlinear models taken from the literature. The analysis of these two examples includes comparison with other methods and demonstrates how identifiability analysis is simplified by this tool. Thus we illustrate the identifiability analysis of other two examples, by including discussion of some specific aspects related to the role of observability and knowledge of initial conditions in testing identifiability and to the computational complexity of the software. The main focus of this paper is not on the description of the mathematical background of the algorithm, which has been presented elsewhere, but on illustrating its use and on some of its more interesting features. DAISY is available on the web site http://www.dei.unipd.it/~pia/. PMID:20185123

  2. Validation of the orthogonal tilt reconstruction method with a biological test sample.

    PubMed

    Chandramouli, Preethi; Hernandez-Lopez, Rogelio; Wang, Hong-Wei; Leschziner, Andres E

    2011-07-01

    Electron microscopy of frozen-hydrated samples (cryo-EM) can yield high resolution structures of macromolecular complexes by accurately determining the orientation of large numbers of experimental views of the sample relative to an existing 3D model. The "initial model problem", the challenge of obtaining these orientations ab initio, remains a major bottleneck in determining the structure of novel macromolecules, chiefly those lacking internal symmetry. We previously proposed a method for the generation of initial models--orthogonal tilt reconstruction (OTR)--that bypasses limitations inherent to the other two existing methods, random conical tilt (RCT) and angular reconstitution (AR). Here we present a validation of OTR with a biological test sample whose structure was previously solved by RCT: the complex between the yeast exosome and the subunit Rrp44. We show that, as originally demonstrated with synthetic data, OTR generates initial models that do not exhibit the "missing cone" artifacts associated with RCT and show an isotropic distribution of information when compared with the known structure. This eliminates the need for further user intervention to solve these artifacts and makes OTR ideal for automation and the analysis of heterogeneous samples. With the former in mind, we propose a set of simple quantitative criteria that can be used, in combination, to select from a large set of initial reconstructions a subset that can be used as reliable references for refinement to higher resolution.

  3. Space experiment "Cellular Responses to Radiation in Space (CellRad)": Hardware and biological system tests.

    PubMed

    Hellweg, Christine E; Dilruba, Shahana; Adrian, Astrid; Feles, Sebastian; Schmitz, Claudia; Berger, Thomas; Przybyla, Bartos; Briganti, Luca; Franz, Markus; Segerer, Jürgen; Spitta, Luis F; Henschenmacher, Bernd; Konda, Bikash; Diegeler, Sebastian; Baumstark-Khan, Christa; Panitz, Corinna; Reitz, Günther

    2015-11-01

    One factor contributing to the high uncertainty in radiation risk assessment for long-term space missions is the insufficient knowledge about possible interactions of radiation with other spaceflight environmental factors. Such factors, e.g. microgravity, have to be considered as possibly additive or even synergistic factors in cancerogenesis. Regarding the effects of microgravity on signal transduction, it cannot be excluded that microgravity alters the cellular response to cosmic radiation, which comprises a complex network of signaling pathways. The purpose of the experiment "Cellular Responses to Radiation in Space" (CellRad, formerly CERASP) is to study the effects of combined exposure to microgravity, radiation and general space flight conditions on mammalian cells, in particular Human Embryonic Kidney (HEK) cells that are stably transfected with different plasmids allowing monitoring of proliferation and the Nuclear Factor κB (NF-κB) pathway by means of fluorescent proteins. The cells will be seeded on ground in multiwell plate units (MPUs), transported to the ISS, and irradiated by an artificial radiation source after an adaptation period at 0 × g and 1 × g. After different incubation periods, the cells will be fixed by pumping a formaldehyde solution into the MPUs. Ground control samples will be treated in the same way. For implementation of CellRad in the Biolab on the International Space Station (ISS), tests of the hardware and the biological systems were performed. The sequence of different steps in MPU fabrication (cutting, drilling, cleaning, growth surface coating, and sterilization) was optimized in order to reach full biocompatibility. Different coatings of the foil used as growth surface revealed that coating with 0.1 mg/ml poly-D-lysine supports cell attachment better than collagen type I. The tests of prototype hardware (Science Model) proved its full functionality for automated medium change, irradiation and fixation of cells. Exposure of

  4. Space experiment "Cellular Responses to Radiation in Space (CELLRAD)": Hardware and biological system tests

    NASA Astrophysics Data System (ADS)

    Hellweg, Christine E.; Dilruba, Shahana; Adrian, Astrid; Feles, Sebastian; Schmitz, Claudia; Berger, Thomas; Przybyla, Bartos; Briganti, Luca; Franz, Markus; Segerer, Jürgen; Spitta, Luis F.; Henschenmacher, Bernd; Konda, Bikash; Diegeler, Sebastian; Baumstark-Khan, Christa; Panitz, Corinna; Reitz, Günther

    2015-11-01

    One factor contributing to the high uncertainty in radiation risk assessment for long-term space missions is the insufficient knowledge about possible interactions of radiation with other spaceflight environmental factors. Such factors, e.g. microgravity, have to be considered as possibly additive or even synergistic factors in cancerogenesis. Regarding the effects of microgravity on signal transduction, it cannot be excluded that microgravity alters the cellular response to cosmic radiation, which comprises a complex network of signaling pathways. The purpose of the experiment "Cellular Responses to Radiation in Space" (CELLRAD, formerly CERASP) is to study the effects of combined exposure to microgravity, radiation and general space flight conditions on mammalian cells, in particular Human Embryonic Kidney (HEK) cells that are stably transfected with different plasmids allowing monitoring of proliferation and the Nuclear Factor κB (NF-κB) pathway by means of fluorescent proteins. The cells will be seeded on ground in multiwell plate units (MPUs), transported to the ISS, and irradiated by an artificial radiation source after an adaptation period at 0 × g and 1 × g. After different incubation periods, the cells will be fixed by pumping a formaldehyde solution into the MPUs. Ground control samples will be treated in the same way. For implementation of CELLRAD in the Biolab on the International Space Station (ISS), tests of the hardware and the biological systems were performed. The sequence of different steps in MPU fabrication (cutting, drilling, cleaning, growth surface coating, and sterilization) was optimized in order to reach full biocompatibility. Different coatings of the foil used as growth surface revealed that coating with 0.1 mg/ml poly-D-lysine supports cell attachment better than collagen type I. The tests of prototype hardware (Science Model) proved its full functionality for automated medium change, irradiation and fixation of cells. Exposure of

  5. Space experiment "Cellular Responses to Radiation in Space (CellRad)": Hardware and biological system tests.

    PubMed

    Hellweg, Christine E; Dilruba, Shahana; Adrian, Astrid; Feles, Sebastian; Schmitz, Claudia; Berger, Thomas; Przybyla, Bartos; Briganti, Luca; Franz, Markus; Segerer, Jürgen; Spitta, Luis F; Henschenmacher, Bernd; Konda, Bikash; Diegeler, Sebastian; Baumstark-Khan, Christa; Panitz, Corinna; Reitz, Günther

    2015-11-01

    One factor contributing to the high uncertainty in radiation risk assessment for long-term space missions is the insufficient knowledge about possible interactions of radiation with other spaceflight environmental factors. Such factors, e.g. microgravity, have to be considered as possibly additive or even synergistic factors in cancerogenesis. Regarding the effects of microgravity on signal transduction, it cannot be excluded that microgravity alters the cellular response to cosmic radiation, which comprises a complex network of signaling pathways. The purpose of the experiment "Cellular Responses to Radiation in Space" (CellRad, formerly CERASP) is to study the effects of combined exposure to microgravity, radiation and general space flight conditions on mammalian cells, in particular Human Embryonic Kidney (HEK) cells that are stably transfected with different plasmids allowing monitoring of proliferation and the Nuclear Factor κB (NF-κB) pathway by means of fluorescent proteins. The cells will be seeded on ground in multiwell plate units (MPUs), transported to the ISS, and irradiated by an artificial radiation source after an adaptation period at 0 × g and 1 × g. After different incubation periods, the cells will be fixed by pumping a formaldehyde solution into the MPUs. Ground control samples will be treated in the same way. For implementation of CellRad in the Biolab on the International Space Station (ISS), tests of the hardware and the biological systems were performed. The sequence of different steps in MPU fabrication (cutting, drilling, cleaning, growth surface coating, and sterilization) was optimized in order to reach full biocompatibility. Different coatings of the foil used as growth surface revealed that coating with 0.1 mg/ml poly-D-lysine supports cell attachment better than collagen type I. The tests of prototype hardware (Science Model) proved its full functionality for automated medium change, irradiation and fixation of cells. Exposure of

  6. A Test of the Relationship between Reading Ability & Standardized Biology Assessment Scores

    ERIC Educational Resources Information Center

    Allen, Denise A.

    2014-01-01

    Little empirical evidence suggested that independent reading abilities of students enrolled in biology predicted their performance on the Biology I Graduation End-of-Course Assessment (ECA). An archival study was conducted at one Indiana urban public high school in Indianapolis, Indiana, by examining existing educational assessment data to test…

  7. Transport studies of mesoscopic and magnetic topological insulators

    NASA Astrophysics Data System (ADS)

    Kandala, Abhinav

    Topological Insulators (TI) are a novel class of materials that are ideally insulating in the bulk, but have gapless, metallic states at the surface. These surface states have very exciting properties such as suppressed backscattering and spin-momentum locking, which are of great interest for research efforts towards dissipation-less electronics and spintronics. The popular thermo-electrics from the Bi chalcogenide family -- Bi2Se3 and Bi 2Te3 -- have been experimentally demonstrated to be promising candidate TI materials, and form the chosen material system for this dissertation research. The first part of this dissertation research focuses on low temperature magneto-transport measurements of mesoscopic topological insulator devices (Chapter 3). The top-down patterning of epitaxial thin films of Bi2Se 3 and Bi2Te3 (that are plagued with bulk conduction) is motivated, in part, by an effort to enhance the surface-to-volume ratio in mesoscopic channels. At cryogenic temperatures, transport measurements of these devices reveal periodic conductance fluctuations in straight channel devices, despite the lack of any explicit patterning of the TI film into a ring or a loop. A careful analysis of the surface morphology and comparison with the transport data then demonstrate that scattering off the edges of triangular plateaus at the surface leads to the creation of Aharonov-Bohm electronic orbits responsible for the periodicity. Another major focus of this dissertation work is on combining topological insulators with magnetism. This has been shown to open a gap in the surface states leading to possibilities of magnetic "gating" and the realization of dissipation-less transport at zero-field, amongst several other exotic quantum phenomena. In this dissertation, I present two different schemes for probing these effects in electrical transport devices -- interfacing with insulating ferromagnets (Chapter 4) and bulk magnetic doping (Chapter 5). In Chapter 4, I shall present the

  8. Mesoscopics of ultrasound and seismic waves: application to passive imaging

    NASA Astrophysics Data System (ADS)

    Larose, É.

    2006-05-01

    This manuscript deals with different aspects of the propagation of acoustic and seismic waves in heterogeneous media, both simply and multiply scattering ones. After a short introduction on conventional imaging techniques, we describe two observations that demonstrate the presence of multiple scattering in seismic records: the equipartition principle, and the coherent backscattering effect (Chap. 2). Multiple scattering is related to the mesoscopic nature of seismic and acoustic waves, and is a strong limitation for conventional techniques like medical or seismic imaging. In the following part of the manuscript (Chaps. 3 5), we present an application of mesoscopic physics to acoustic and seismic waves: the principle of passive imaging. By correlating records of ambient noise or diffuse waves obtained at two passive sensors, it is possible to reconstruct the impulse response of the medium as if a source was placed at one sensor. This provides the opportunity of doing acoustics and seismology without a source. Several aspects of this technique are presented here, starting with theoretical considerations and numerical simulations (Chaps. 3, 4). Then we present experimental applications (Chap. 5) to ultrasound (passive tomography of a layered medium) and to seismic waves (passive imaging of California, and the Moon, with micro-seismic noise). Physique mésoscopique des ultrasons et des ondes sismiques : application à l'imagerie passive. Cet article de revue rassemble plusieurs aspects fondamentaux et appliqués de la propagation des ondes acoustiques et élastiques dans les milieux hétérogènes, en régime de diffusion simple ou multiple. Après une introduction sur les techniques conventionelles d'imagerie sismique et ultrasonore, nous présentons deux expériences qui mettent en évidence la présence de diffusion multiple dans les enregistrements sismologiques : l'équipartition des ondes, et la rétrodiffusion cohérente (Chap. 2). La diffusion multiple des

  9. Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-07-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of these Lagrangian particles. An analytical formula is proposed to relate the tDPD parameters to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the conventional DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.

  10. Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems.

    PubMed

    Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-07-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of these Lagrangian particles. An analytical formula is proposed to relate the tDPD parameters to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the conventional DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.

  11. Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems

    PubMed Central

    Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-01-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of these Lagrangian particles. An analytical formula is proposed to relate the tDPD parameters to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the conventional DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers. PMID:26156459

  12. Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems.

    PubMed

    Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-07-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of these Lagrangian particles. An analytical formula is proposed to relate the tDPD parameters to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the conventional DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers. PMID:26156459

  13. Mesoscopic simulations of accelerated polymer drift in microfluidic capillaries

    NASA Astrophysics Data System (ADS)

    Berkenbos, A.; Lowe, C. P.

    2007-10-01

    We use a mesoscopic simulation technique to study the transport of polymers in dilute solution flowing through a cylindrical tube. The simulations use an explicit solvent model to include all the relevant hydrodynamic couplings and a coarse grained ideal chain model for the polymers (appropriate for systems near the theta temperature). For the interactions between the solvent and the tube wall we use a novel method that ensures continuity of the stress at the interface. We show that the results for the polymer drift velocity are independent of the degree of coarse graining. Further, for the case where the size of the chains is small but not negligible compared to the tube radius, our results are in excellent agreement with experiment. However, they also show that in this regime, the "accelerated" drift, relative to the average solvent flow velocity, is described by the steric effect of the tube wall excluding the polymer center of mass from sampling the full cross section of the tube. Hydrodynamic interactions have a negligible influence in this regime. Consequently, the agreement between experiment and theories that approximates the former but includes the latter is fortunate. When the undisturbed polymer radius approaches or exceeds the tube radius, the hydrodynamic interactions do have a significant effect. They reduce the drift velocity, in qualitative agreement with theoretical predictions. The accelerated drift still approaches the maximum value, one would expect based on a Poiseuille flow but more slowly than if one neglects hydrodynamics. Finally, we propose an empirical fit that accurately describes data in the intermediate regime.

  14. Self-consistent theory for systems with mesoscopic fluctuations

    NASA Astrophysics Data System (ADS)

    Ciach, A.; Góźdź, W. T.

    2016-10-01

    We have developed a theory for inhomogeneous systems that allows for the incorporation of the effects of mesoscopic fluctuations. A hierarchy of equations relating the correlation and direct correlation functions for the local excess φ ≤ft(\\mathbf{r}\\right) of the volume fraction of particles ζ has been obtained, and an approximation leading to a closed set of equations for the two-point functions has been introduced for the disordered inhomogeneous phase. We have numerically solved the self-consistent equations for one-dimensional (1D) and three-dimensional (3D) models with short-range attraction and long-range repulsion. Predictions for all of the qualitative properties of the 1D model agree with the exact results, but only semi-quantitative agreement is obtained in the simplest version of the theory. The effects of fluctuations in the two 3D models considered are significantly different, despite the very similar properties of these models in the mean-field approximation. In both cases we obtain the sequence of large-small-large compressibility for increasing ζ. The very small compressibility is accompanied by the oscillatory decay of correlations with correlation lengths that are orders of magnitude larger than the size of particles. In one of the two models considered, the small compressibility becomes very small and the large compressibility becomes very large with decreasing temperature, and eventually van der Waals loops appear. Further studies are necessary in order to determine the nature of the strongly inhomogeneous phase present for intermediate volume fractions in 3D.

  15. Mesoscopic dynamics of diffusion-influenced enzyme kinetics.

    PubMed

    Chen, Jiang-Xing; Kapral, Raymond

    2011-01-28

    A particle-based mesoscopic model for enzyme kinetics is constructed and used to investigate the influence of diffusion on the reactive dynamics. Enzymes and enzyme-substrate complexes are modeled as finite-size soft spherical particles, while substrate, product, and solvent molecules are point particles. The system is evolved using a hybrid molecular dynamics-multiparticle collision dynamics scheme. Both the nonreactive and reactive dynamics are constructed to satisfy mass, momentum, and energy conservation laws, and reversible reaction steps satisfy detailed balance. Hydrodynamic interactions among the enzymes and complexes are automatically accounted for in the dynamics. Diffusion manifests itself in various ways, notably in power-law behavior in the evolution of the species concentrations. In accord with earlier investigations, regimes where the product production rate exhibits either monotonic or nonmonotonic behavior as a function of time are found. In addition, the species concentrations display both t(-1/2) and t(-3/2) power-law behavior, depending on the dynamical regime under investigation. For high enzyme volume fractions, cooperative effects influence the enzyme kinetics. The time dependent rate coefficient determined from the mass action rate law is computed and shown to depend on the enzyme concentration. Lifetime distributions of substrate molecules newly released in complex dissociation events are determined and shown to have either a power-law form for rebinding to the same enzyme from which they were released or an exponential form for rebinding to different enzymes. The model can be used and extended to explore a variety of issues related concentration effects and diffusion on enzyme kinetics.

  16. Capacitance, entanglement energetics and persistent currents of mesoscopic rings

    NASA Astrophysics Data System (ADS)

    Buttiker, Markus

    2009-03-01

    Small rings are a quintessential mesoscopic system. As a consequence of quantum coherence small normal metal rings support a persistent current. Novel experimental techniques will permit to investigate rings with geometries which highlight the effects of interactions. We discuss rings with in-line and side quantum dots. In the Coulomb blockade regime we derive an effective two-state Hamiltonian and discuss the flux dependence of the Coulomb blockade peaks in the capacitance and the persistent current [1]. Different nearly degenerate charge configurations of the ring-dot system become entangled with an electrical environment. With an environment consisting of an external resistor capacitively coupled to the ring and dot the entire system maps on a spin boson problem. Analysis shows that the visibility of the persistent current decreases with increasing coupling to the environment [2]. The system-bath entanglement which is at the origin of this phenomenon can be detected by projective measurements of the energy of the ring-dot subsystem or the persistent current: even in the ground state of the total system the ring can be found with some probability in the energetically higher lying state [3]. The distribution of energy or of the persistent currents is a direct measure of the system bath entanglement. [4pt] [1] M. Buttiker and C. A. Stafford, Phys. Rev. Lett. 76, 495 (1996); [0pt] [2] P. Cedraschi, V. V. Ponomarenko, and M. Buttiker, Phys. Rev. Lett. 84, 346 (2000); P. Cedraschi and M. Buttiker, Annals of Physics, 289, 1 (2001). [0pt] [3] A. N. Jordan and M. Buttiker, Phys. Rev. Lett. 92, 247901 (2004); M. Buttiker and A. N. Jordan, Physica E 29, 272 (2005); K. Le Hur, Annals of Physics, 323, 2208 (2008).

  17. Mesoscopic coarse-grained simulations of lysozyme adsorption.

    PubMed

    Yu, Gaobo; Liu, Jie; Zhou, Jian

    2014-05-01

    Coarse-grained simulations are adopted to study the adsorption behavior of lysozyme on different (hydrophobic, neutral hydrophilic, zwitterionic, negatively charged, and positively charged) surfaces at the mesoscopic microsecond time scale (1.2 μs). Simulation results indicate the following: (i) the conformation change of lysozyme on the hydrophobic surface is bigger than any other studied surfaces; (ii) the active sites of lysozyme are faced to the hydrophobic surface with a "top end-on" orientation, while they are exposed to the liquid phase on the hydrophilic surface with a "back-on" orientation; (iii) the neutral hydrophilic surface can induce the adsorption of lysozyme, while the nonspecific protein adsorption can be resisted by the zwitterionic surface; (iv) when the solution ionic strength is low, lysozyme can anchor on the negatively charged surface easily but cannot adsorb on the positively charged surface; (v) when the solution ionic strength is high, the positively charged lysozyme can also adsorb on the like-charged surface; (vi) the major positive potential center of lysozyme, especially the residue ARG128, plays a vital role in leading the adsorption of lysozyme on charged surfaces; (vii) when the ionic strength is high, a counterion layer is formed above the positively charged surface, which is the key factor why lysozyme can adsorb on a like-charged surface. The coarse-grained method based on the MARTINI force field for proteins and the BMW water model could provide an efficient way to understand protein interfacial adsorption behavior at a greater length scale and time scale. PMID:24785197

  18. Multiscale modelling of mesoscopic phenomena triggered by quantum events: light-driven azo-materials and beyond.

    PubMed

    Böckmann, Marcus; Marx, Dominik; Peter, Christine; Site, Luigi Delle; Kremer, Kurt; Doltsinis, Nikos L

    2011-05-01

    The macroscopic functionality of soft (bio-)materials is often triggered by quantum-mechanical events which are highly local in space and time. In order to arrive at the resulting macroscopically observable phenomena, many orders of magnitude need to be bridged on both the time and the length scale. In the present paper, we first introduce a range of simulation methods at different scales as well as theoretical approaches to form bridges between them. We then outline a strategy to develop an adaptive multiscale simulation approach which connects the quantum to the mesoscopic level by bringing together ab initio molecular dynamics (QM), classical (force field) molecular dynamics (MM), and coarse grained (CG) simulation techniques. With a multitude of photoactive materials in mind, we apply our methodology to a prototypical test case-light-induced phase transitions in a liquid crystal containing the azobenzene photoswitch.

  19. Inferring local competition intensity from patch size distributions: a test using biological soil crusts

    USGS Publications Warehouse

    Bowker, Matthew A.; Maestre, Fernando T.

    2012-01-01

    Dryland vegetation is inherently patchy. This patchiness goes on to impact ecology, hydrology, and biogeochemistry. Recently, researchers have proposed that dryland vegetation patch sizes follow a power law which is due to local plant facilitation. It is unknown what patch size distribution prevails when competition predominates over facilitation, or if such a pattern could be used to detect competition. We investigated this question in an alternative vegetation type, mosses and lichens of biological soil crusts, which exhibit a smaller scale patch-interpatch configuration. This micro-vegetation is characterized by competition for space. We proposed that multiplicative effects of genetics, environment and competition should result in a log-normal patch size distribution. When testing the prevalence of log-normal versus power law patch size distributions, we found that the log-normal was the better distribution in 53% of cases and a reasonable fit in 83%. In contrast, the power law was better in 39% of cases, and in 8% of instances both distributions fit equally well. We further hypothesized that the log-normal distribution parameters would be predictably influenced by competition strength. There was qualitative agreement between one of the distribution's parameters (μ) and a novel intransitive (lacking a 'best' competitor) competition index, suggesting that as intransitivity increases, patch sizes decrease. The correlation of μ with other competition indicators based on spatial segregation of species (the C-score) depended on aridity. In less arid sites, μ was negatively correlated with the C-score (suggesting smaller patches under stronger competition), while positive correlations (suggesting larger patches under stronger competition) were observed at more arid sites. We propose that this is due to an increasing prevalence of competition transitivity as aridity increases. These findings broaden the emerging theory surrounding dryland patch size distributions

  20. Applications of mesoscopic physics. Annual technical report, July 1992--June 1993

    SciTech Connect

    Feng, Shechao

    1993-04-01

    Research activities in the area ``applications of mesoscopic physics to novel correlations and fluctuations of speckle patterns: imaging and tomography with multiply scattered classical waves`` are briefly summarized. The main thrust in fundamental research is in the general areas of mesoscopic effects in disordered semiconductors and metals and the related field of applications of mesoscopic physics to the subject matter of classical wave propagation through disordered scattering media. Specific topics are Fabry-Perot interferometer with disorder: correlations and light localization; electron-phonon inelastic scattering rate and the temperature scaling exponent in integer quantum Hall effect; and transmission and reflection correlations of second harmonic waves in nonlinear random media. Research in applied physics centered on far infrared photon-assisted transport through quantum point contact devices and photon migration distributions in multiple scattering media. 7 refs.

  1. Applications of mesoscopic physics. [Dept. of Physics, UCLA, Los Angeles, California

    SciTech Connect

    Feng, Shechao.

    1993-01-01

    Research activities in the area applications of mesoscopic physics to novel correlations and fluctuations of speckle patterns: imaging and tomography with multiply scattered classical waves'' are briefly summarized. The main thrust in fundamental research is in the general areas of mesoscopic effects in disordered semiconductors and metals and the related field of applications of mesoscopic physics to the subject matter of classical wave propagation through disordered scattering media. Specific topics are Fabry-Perot interferometer with disorder: correlations and light localization; electron-phonon inelastic scattering rate and the temperature scaling exponent in integer quantum Hall effect; and transmission and reflection correlations of second harmonic waves in nonlinear random media. Research in applied physics centered on far infrared photon-assisted transport through quantum point contact devices and photon migration distributions in multiple scattering media. 7 refs.

  2. Tunable quasiparticle trapping in Meissner and vortex states of mesoscopic superconductors

    PubMed Central

    Taupin, M.; Khaymovich, I. M.; Meschke, M.; Mel'nikov, A. S.; Pekola, J. P.

    2016-01-01

    Nowadays, superconductors serve in numerous applications, from high-field magnets to ultrasensitive detectors of radiation. Mesoscopic superconducting devices, referring to those with nanoscale dimensions, are in a special position as they are easily driven out of equilibrium under typical operating conditions. The out-of-equilibrium superconductors are characterized by non-equilibrium quasiparticles. These extra excitations can compromise the performance of mesoscopic devices by introducing, for example, leakage currents or decreased coherence time in quantum devices. By applying an external magnetic field, one can conveniently suppress or redistribute the population of excess quasiparticles. In this article, we present an experimental demonstration and a theoretical analysis of such effective control of quasiparticles, resulting in electron cooling both in the Meissner and vortex states of a mesoscopic superconductor. We introduce a theoretical model of quasiparticle dynamics, which is in quantitative agreement with the experimental data. PMID:26980225

  3. Tunable quasiparticle trapping in Meissner and vortex states of mesoscopic superconductors.

    PubMed

    Taupin, M; Khaymovich, I M; Meschke, M; Mel'nikov, A S; Pekola, J P

    2016-01-01

    Nowadays, superconductors serve in numerous applications, from high-field magnets to ultrasensitive detectors of radiation. Mesoscopic superconducting devices, referring to those with nanoscale dimensions, are in a special position as they are easily driven out of equilibrium under typical operating conditions. The out-of-equilibrium superconductors are characterized by non-equilibrium quasiparticles. These extra excitations can compromise the performance of mesoscopic devices by introducing, for example, leakage currents or decreased coherence time in quantum devices. By applying an external magnetic field, one can conveniently suppress or redistribute the population of excess quasiparticles. In this article, we present an experimental demonstration and a theoretical analysis of such effective control of quasiparticles, resulting in electron cooling both in the Meissner and vortex states of a mesoscopic superconductor. We introduce a theoretical model of quasiparticle dynamics, which is in quantitative agreement with the experimental data. PMID:26980225

  4. Giant Mesoscopic Fluctuations and Long-Range Superconducting Correlations in Superconductor-Ferromagnet Structures.

    PubMed

    Mel'nikov, A S; Buzdin, A I

    2016-08-12

    The fluctuating superconducting correlations emerging in dirty hybrid structures under the conditions of the strong proximity effect are demonstrated to affect the validity range of the widely used formalism of Usadel equations at mesoscopic scales. In superconductor-ferromagnet structures these giant mesoscopic fluctuations originating from the interference effects for the Cooper pair wave function in the presence of the exchange field can be responsible for an anomalously slow decay of superconducting correlations in a ferromagnet even when the noncollinear and spin-orbit effects are negligible. The resulting sample-to-sample fluctuations of the Josephson current in superconductor-ferromagnetic-superconductor junctions and the local density of states in superconductor-ferromagnetic hybrid structures can provide an explanation of the long-range proximity phenomena observed in mesoscopic samples with collinear magnetization. PMID:27563990

  5. Giant Mesoscopic Fluctuations and Long-Range Superconducting Correlations in Superconductor-Ferromagnet Structures

    NASA Astrophysics Data System (ADS)

    Mel'nikov, A. S.; Buzdin, A. I.

    2016-08-01

    The fluctuating superconducting correlations emerging in dirty hybrid structures under the conditions of the strong proximity effect are demonstrated to affect the validity range of the widely used formalism of Usadel equations at mesoscopic scales. In superconductor-ferromagnet structures these giant mesoscopic fluctuations originating from the interference effects for the Cooper pair wave function in the presence of the exchange field can be responsible for an anomalously slow decay of superconducting correlations in a ferromagnet even when the noncollinear and spin-orbit effects are negligible. The resulting sample-to-sample fluctuations of the Josephson current in superconductor-ferromagnetic-superconductor junctions and the local density of states in superconductor-ferromagnetic hybrid structures can provide an explanation of the long-range proximity phenomena observed in mesoscopic samples with collinear magnetization.

  6. Giant Mesoscopic Fluctuations and Long-Range Superconducting Correlations in Superconductor-Ferromagnet Structures.

    PubMed

    Mel'nikov, A S; Buzdin, A I

    2016-08-12

    The fluctuating superconducting correlations emerging in dirty hybrid structures under the conditions of the strong proximity effect are demonstrated to affect the validity range of the widely used formalism of Usadel equations at mesoscopic scales. In superconductor-ferromagnet structures these giant mesoscopic fluctuations originating from the interference effects for the Cooper pair wave function in the presence of the exchange field can be responsible for an anomalously slow decay of superconducting correlations in a ferromagnet even when the noncollinear and spin-orbit effects are negligible. The resulting sample-to-sample fluctuations of the Josephson current in superconductor-ferromagnetic-superconductor junctions and the local density of states in superconductor-ferromagnetic hybrid structures can provide an explanation of the long-range proximity phenomena observed in mesoscopic samples with collinear magnetization.

  7. Probabilistic simulation of mesoscopic “Schrödinger cat” states

    NASA Astrophysics Data System (ADS)

    Opanchuk, B.; Rosales-Zárate, L.; Reid, M. D.; Drummond, P. D.

    2014-02-01

    We carry out probabilistic phase-space sampling of mesoscopic Schrödinger cat quantum states, demonstrating multipartite Bell violations for up to 60 qubits. We use states similar to those generated in photonic and ion-trap experiments. These results show that mesoscopic quantum superpositions are directly accessible to probabilistic sampling, and we analyze the properties of sampling errors. We also demonstrate dynamical simulation of super-decoherence in ion traps. Our computer simulations can be either exponentially faster or slower than experiment, depending on the correlations measured.

  8. A comparative study on characterization of textile wastewaters (untreated and treated) toxicity by chemical and biological tests.

    PubMed

    Sharma, K P; Sharma, S; Sharma, Subhasini; Singh, P K; Kumar, S; Grover, R; Sharma, P K

    2007-08-01

    Toxicity of textile wastewaters (untreated and treated) and their ingredient chemicals was quantified in terms of their chemical characteristics, fish (Gambusia affinis) mortality and end point growth responses of duckweed (Lemna aequinoctialis) in short-term bioassays. Other parameters of fish bioassay were erythrocyte morphology and its counts. Despite of a definite correlation between data of biological tests (LC/EC(50) values) with that of chemical tests, biological tests were found to be relatively more sensitive to both wastewaters and ingredient chemicals. Amongst all the examined parameters of test organisms, fish RBCs (morphology and counts) sensitivity to pollutants in the wastewaters was usually maximum and therefore, their study should be included in the routine fish bioassay. Other advantage of biological test such as on Lemna is even detection of eutrophic potential of wastewaters, as noted at their higher dilutions. The ingredient chemicals (major) contributing maximum toxicity to textile dye wastewater were, acids (HCl and H(2)SO(4)), alkali (Na(2)O SiO(2)), salt (NaNO(2)) and heavy metal (Cu), whereas dyes (4) were relatively less toxic. PMID:17583772

  9. Energy utilization in fluctuating biological energy converters.

    PubMed

    Szőke, Abraham; Hajdu, Janos

    2016-05-01

    We have argued previously [Szoke et al., FEBS Lett. 553, 18-20 (2003); Curr. Chem. Biol. 1, 53-57 (2007)] that energy utilization and evolution are emergent properties based on a small number of established laws of physics and chemistry. The relevant laws constitute a framework for biology on a level intermediate between quantum chemistry and cell biology. There are legitimate questions whether these concepts are valid at the mesoscopic level. Such systems fluctuate appreciably, so it is not clear what their efficiency is. Advances in fluctuation theorems allow the description of such systems on a molecular level. We attempt to clarify this topic and bridge the biochemical and physical descriptions of mesoscopic systems. PMID:27191009

  10. Energy utilization in fluctuating biological energy converters

    PubMed Central

    Szőke, Abraham; Hajdu, Janos

    2016-01-01

    We have argued previously [Szoke et al., FEBS Lett. 553, 18–20 (2003); Curr. Chem. Biol. 1, 53–57 (2007)] that energy utilization and evolution are emergent properties based on a small number of established laws of physics and chemistry. The relevant laws constitute a framework for biology on a level intermediate between quantum chemistry and cell biology. There are legitimate questions whether these concepts are valid at the mesoscopic level. Such systems fluctuate appreciably, so it is not clear what their efficiency is. Advances in fluctuation theorems allow the description of such systems on a molecular level. We attempt to clarify this topic and bridge the biochemical and physical descriptions of mesoscopic systems. PMID:27191009

  11. Dynamic studies of proton diffusion in mesoscopic heterogeneous matrix

    PubMed Central

    Gutman, M.; Nachliel, E.; Kiryati, S.

    1992-01-01

    The thin water layer, as found in chloroplast or mitochondria, is confined between low dielectric amphypathic surfaces a few nm apart. The physical properties of this mesoscopic space, and how its dimensions affect the rate of chemical reactions proceeding in it, is the subject for this study. The method selected for this purpose is time resolved fluorometry which can monitor the reversible dissociation of a proton from excited molecule of pyranine (8 hydroxy pyrene 1,3,6 tri sulfonate) trapped in thin water layers of a multilamellar vesicle made of neutral or slightly charged phospholipids. The results were analyzed by a computer program of N. Agmon (Pines, E., D. Huppert, and N. Agmon. 1988. J. Am. Chem. Soc. 88:5620-5630) that simulates the diffusion of a proton, subjected to electrostatic attraction, in a thin water layer enclosed between low affinity, proton binding surfaces. The analysis determines the diffusion coefficient of the proton, the effective dielectric constant of the water and the water accessibility of the phosphomoieties of the lipids. These parameters were measured for various lipids [egg-phosphatidylcholine (egg PC), dipalmitoyl phosphatidylcholine (DPPC), cholesterol + DPPC (1:1) and egg PC plus phosphatidyl serine (9:1)] and under varying osmotic pressure which reduces the width of the water layer down to ∼10 ∼ across. We found that: (a) The effective dielectric constant of the aqueous layer, depending on the lipid composition, is ∼40. (b) The diffusion coefficient of the proton in the thin layer (30-10 ∼ across) is that measured in bulk water D = 9.3 10-5 cm2/s, indicating that the water retains its normal liquid state even on contact with the membrane. (c) The reactivity of the phosphomoiety, quantitated by rate of its reaction with proton, diminishes under lateral pressure which reduces the surface area per lipid. We find no evidence for abnormal dynamics of proton transfer at the lipid water interface which, by any mechanism

  12. Testing biological effects of hand-washing grey water for reuse in irrigation on an urban farm: a case study.

    PubMed

    Khan, Mohammad Zain; Sim, Yei Lin; Lin, Yang Jian; Lai, Ka Man

    2013-01-01

    The feasibility of reusing hand-washing grey water contaminated with antibacterial hand-washing liquid for irrigation purposes in an urban farm is explored in this case study. Experiments are carried out to investigate if the quality of this grey water allows for its reuse in agriculture as per the guidelines established by the World Health Organization (WHO). However, there is no guideline to test the biological effect of grey water prior to agricultural use. It is plausible that the antibacterial property of the grey water can harm the soil microbial system and plants when applied to land, even if all other water quality parameters satisfy the WHO limit. We use algae (Chlorella vulgaris) and indigenous soil bacteria as initial plant and soil bacteria indicators, respectively, to test the potential inhibition of the water on plants and soil bacteria. Results show that the chemical oxygen demand (COD) of the grey water is 10% higher than the WHO permissible level, while all other water quality parameters are within the limits after four days of our experimental period. An inhibitory effect is observed in all of the biological tests. However, the inhibitory effect on algae and soil bacteria is not observed after the four-day period. The case study demonstrates a new approach for testing the biological effect of grey water, which can be used in conjunction with the WHO guideline, and provides data for this urban farm to set up a future water treatment system for grey-water reuse in irrigation. PMID:23530370

  13. Testing biological effects of hand-washing grey water for reuse in irrigation on an urban farm: a case study.

    PubMed

    Khan, Mohammad Zain; Sim, Yei Lin; Lin, Yang Jian; Lai, Ka Man

    2013-01-01

    The feasibility of reusing hand-washing grey water contaminated with antibacterial hand-washing liquid for irrigation purposes in an urban farm is explored in this case study. Experiments are carried out to investigate if the quality of this grey water allows for its reuse in agriculture as per the guidelines established by the World Health Organization (WHO). However, there is no guideline to test the biological effect of grey water prior to agricultural use. It is plausible that the antibacterial property of the grey water can harm the soil microbial system and plants when applied to land, even if all other water quality parameters satisfy the WHO limit. We use algae (Chlorella vulgaris) and indigenous soil bacteria as initial plant and soil bacteria indicators, respectively, to test the potential inhibition of the water on plants and soil bacteria. Results show that the chemical oxygen demand (COD) of the grey water is 10% higher than the WHO permissible level, while all other water quality parameters are within the limits after four days of our experimental period. An inhibitory effect is observed in all of the biological tests. However, the inhibitory effect on algae and soil bacteria is not observed after the four-day period. The case study demonstrates a new approach for testing the biological effect of grey water, which can be used in conjunction with the WHO guideline, and provides data for this urban farm to set up a future water treatment system for grey-water reuse in irrigation.

  14. Critical tests for determination of microbiological quality and biological activity in commercial vermicompost samples of different origins.

    PubMed

    Grantina-Ievina, Lelde; Andersone, Una; Berkolde-Pīre, Dace; Nikolajeva, Vizma; Ievinsh, Gederts

    2013-12-01

    The aim of the present paper was to show that differences in biological activity among commercially produced vermicompost samples can be found by using a relatively simple test system consisting of microorganism tests on six microbiological media and soilless seedling growth tests with four vegetable crop species. Significant differences in biological properties among analyzed samples were evident both at the level of microbial load as well as plant growth-affecting activity. These differences were mostly manufacturer- and feedstock-associated, but also resulted from storage conditions of vermicompost samples. A mature vermicompost sample that was produced from sewage sludge still contained considerable number of Escherichia coli. Samples from all producers contained several potentially pathogenic fungal species such as Aspergillus fumigatus, Pseudallescheria boidii, Pseudallescheria fimeti, Pseudallescheria minutispora, Scedosporium apiospermum, Scedosporium prolificans, Scopulariopsis brevicaulis, Stachybotrys chartarum, Geotrichum spp., Aphanoascus terreus, and Doratomyces columnaris. In addition, samples from all producers contained plant growth-promoting fungi from the genera Trichoderma and Mortierella. The described system can be useful both for functional studies aiming at understanding of factors affecting quality characteristics of vermicompost preparations and for routine testing of microbiological quality and biological activity of organic waste-derived composts and vermicomposts.

  15. 77 FR 26162 - Amendments to Sterility Test Requirements for Biological Products

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-03

    ... clarify and update the sterility test requirements. On March 11, 1976 (41 FR 10427) and March 2, 1979 (44... provide greater consistency with the test methods of USP XXI. Finally, on September 15, 1997 (62 FR 48174... CGMP, and is supported by sterility testing using validated and verified test methods,'' (76 FR...

  16. Membrane materials for storing biological samples intended for comparative nanotoxicological testing

    NASA Astrophysics Data System (ADS)

    Metelkin, A.; Kuznetsov, D.; Kolesnikov, E.; Chuprunov, K.; Kondakov, S.; Osipov, A.; Samsonova, J.

    2015-11-01

    The study is aimed at identifying the samples of most promising membrane materials for storing dry specimens of biological fluids (Dried Blood Spots, DBS technology). Existing sampling systems using cellulose fiber filter paper have a number of drawbacks such as uneven distribution of the sample spot, dependence of the spot spreading area on the individual biosample properties, incomplete washing-off of the sample due to partially inconvertible sorption of blood components on cellulose fibers, etc. Samples of membrane materials based on cellulose, polymers and glass fiber with applied biosamples were studied using methods of scanning electron microscopy, FT-IR spectroscopy and surface-wetting measurement. It was discovered that cellulose-based membrane materials sorb components of biological fluids inside their structure, while membranes based on glass fiber display almost no interaction with the samples and biological fluid components dry to films in the membrane pores between the structural fibers. This characteristic, together with the fact that membrane materials based on glass fiber possess sufficient strength, high wetting properties and good storage capacity, attests them as promising material for dry samples of biological fluids storage systems.

  17. Testing Effect and Complex Comprehension in a Large Introductory Undergraduate Biology Course

    ERIC Educational Resources Information Center

    Pagliarulo, Christopher L.

    2011-01-01

    Traditional undergraduate biology courses are content intensive, requiring students to understand and remember large amounts of information in short periods of time. Yet most students maintain little of the material encountered during their education. Poor knowledge retention is a main cause of academic failure and high undergraduate attrition…

  18. The Use of Application Test, a Novel Type of Problem-solving Exercise as a Tool of Teaching and Assessment of Competence in Medical Biology.

    ERIC Educational Resources Information Center

    Szeberenyi, Jozsef; Tigyi, Andras

    1987-01-01

    A new type of multiple-choice test was developed and used in the teaching and assessment of knowledge of medical biology at a university in Hungary. The test includes experimental data and requires students to interpret data and to draw conclusions from results. A description of the test, experiences with the test, and one test are included. (RH)

  19. Cosmic radiation exposure of biological test systems during the EXPOSE-E mission.

    PubMed

    Berger, Thomas; Hajek, Michael; Bilski, Pawel; Körner, Christine; Vanhavere, Filip; Reitz, Günther

    2012-05-01

    In the frame of the EXPOSE-E mission on the Columbus external payload facility EuTEF on board the International Space Station, passive thermoluminescence dosimeters were applied to measure the radiation exposure of biological samples. The detectors were located either as stacks next to biological specimens to determine the depth dose distribution or beneath the sample carriers to determine the dose levels for maximum shielding. The maximum mission dose measured in the upper layer of the depth dose part of the experiment amounted to 238±10 mGy, which relates to an average dose rate of 408±16 μGy/d. In these stacks of about 8 mm height, the dose decreased by 5-12% with depth. The maximum dose measured beneath the sample carriers was 215±16 mGy, which amounts to an average dose rate of 368±27 μGy/d. These values are close to those assessed for the interior of the Columbus module and demonstrate the high shielding of the biological experiments within the EXPOSE-E facility. Besides the shielding by the EXPOSE-E hardware itself, additional shielding was experienced by the external structures adjacent to EXPOSE-E, such as EuTEF and Columbus. This led to a dose gradient over the entire exposure area, from 215±16 mGy for the lowest to 121±6 mGy for maximum shielding. Hence, the doses perceived by the biological samples inside EXPOSE-E varied by 70% (from lowest to highest dose). As a consequence of the high shielding, the biological samples were predominantly exposed to galactic cosmic heavy ions, while electrons and a significant fraction of protons of the radiation belts and solar wind did not reach the samples.

  20. Cosmic Radiation Exposure of Biological Test Systems During the EXPOSE-E Mission

    PubMed Central

    Hajek, Michael; Bilski, Pawel; Körner, Christine; Vanhavere, Filip; Reitz, Günther

    2012-01-01

    Abstract In the frame of the EXPOSE-E mission on the Columbus external payload facility EuTEF on board the International Space Station, passive thermoluminescence dosimeters were applied to measure the radiation exposure of biological samples. The detectors were located either as stacks next to biological specimens to determine the depth dose distribution or beneath the sample carriers to determine the dose levels for maximum shielding. The maximum mission dose measured in the upper layer of the depth dose part of the experiment amounted to 238±10 mGy, which relates to an average dose rate of 408±16 μGy/d. In these stacks of about 8 mm height, the dose decreased by 5–12% with depth. The maximum dose measured beneath the sample carriers was 215±16 mGy, which amounts to an average dose rate of 368±27 μGy/d. These values are close to those assessed for the interior of the Columbus module and demonstrate the high shielding of the biological experiments within the EXPOSE-E facility. Besides the shielding by the EXPOSE-E hardware itself, additional shielding was experienced by the external structures adjacent to EXPOSE-E, such as EuTEF and Columbus. This led to a dose gradient over the entire exposure area, from 215±16 mGy for the lowest to 121±6 mGy for maximum shielding. Hence, the doses perceived by the biological samples inside EXPOSE-E varied by 70% (from lowest to highest dose). As a consequence of the high shielding, the biological samples were predominantly exposed to galactic cosmic heavy ions, while electrons and a significant fraction of protons of the radiation belts and solar wind did not reach the samples. Key Words: Space radiation—Dosimetry—Passive radiation detectors—Thermoluminescence—EXPOSE-E. Astrobiology 12, 387–392. PMID:22680685

  1. Mortality follow-up of veterans who participated in military chemical and biological warfare agent testing between 1962 and 1972.

    PubMed

    Kang, Han K; Bullman, Tim

    2009-01-01

    Between 1962 and 1972, several thousand U.S. Navy personnel participated in Project SHAD (Shipboard Hazard and Defense). These tests potentially exposed participants to either active chemical or biological warfare agents or their simulants. This study examined mortality risk associated with participating in SHAD tests by comparing the cause-specific mortality of 4927 SHAD veterans to that of 10,927 other Navy veterans. Compared to other Navy veterans, SHAD veterans had an increased risk of overall mortality, which was due primarily to heart disease deaths.

  2. A versatile system for biological and soil chemical tests on a planetary landing craft. I - Scientific objectives

    NASA Technical Reports Server (NTRS)

    Radmer, R. J.; Kok, B.; Martin, J. P.

    1976-01-01

    We describe an approach for the remote detection and characterization of life in planetary soil samples. A mass spectrometer is used as the central sensor to monitor changes in the gas phase in eleven test cells filled with soil. Many biological assays, ranging from general 'in situ' assays to specific metabolic processes (such as photosynthesis, respiration, denitrification, etc.) can be performed by appropriate additions to the test cell via attached preloaded injector capsules. The system is also compatible with a number of chemical assays such as the analysis of atmospheric composition (both chemical and isotopic), the status of soil water, and the determination of compounds of carbon, nitrogen and sulfur in the soil.

  3. A material combination principle for highly efficient polymer solar cells investigated by mesoscopic phase heterogeneity.

    PubMed

    Yan, Han; Li, Denghua; He, Chang; Wei, Zhixiang; Yang, Yanlian; Li, Yongfang

    2013-12-01

    Organic solar cells have become a promising energy conversion candidate because of their unique advantages. Novel fullerene derivatives, as a common acceptor, can increase power conversion efficiency (PCE) by increasing the open-circuit voltage. As a representative acceptor, Indene-C60 bisadduct (ICBA) can reach high efficiency with poly(3-hexylthiophene) (P3HT). On the other hand, the novel synthesized polymers mainly aimed to broaden the optical absorption range have steadily promoted efficiency to higher than 9%. However, it is challenging to obtain the desired result by simply combining ICBA with other high-efficiency donors. Thus, P3HT or a high-efficiency polymer PBDTTT-C-T (copolymer of thienyl-substituted BDT with substituted TT) is used as donor and PCBM or ICBA as acceptor in this article to clarify the mechanism behind these materials. The optical and photovoltaic properties of the materials are studied for pair-wise combination. Among these four material groups, the highest PCE of 6.2% is obtained for the PBDTTT-C-T/PCBM combination while the lowest PCE of 3.5% is obtained for the PBDTTT-C-T/ICBA combination. The impact of the mesoscopic heterogeneity on the local mesoscopic photoelectric properties is identified by photo-conductive AFM (pc-AFM), and the consistence between the mesoscopic properties and the macroscopic device performances is also observed. Based on these results, an interface combined model is proposed based on the mesoscopic phase heterogeneity. This study provides a new view on the rational selection of photovoltaic materials, where, aside from the traditional energy level and absorption spectrum matching, the matching of mesoscopic heterogeneity must also be considered.

  4. Acoustic energy dissipation and thermalization in carbon nanotubes: Atomistic modeling and mesoscopic description

    NASA Astrophysics Data System (ADS)

    Jacobs, William M.; Nicholson, David A.; Zemer, Hagit; Volkov, Alexey N.; Zhigilei, Leonid V.

    2012-10-01

    The exchange of energy between low-frequency mechanical oscillations and high-frequency vibrational modes in carbon nanotubes (CNTs) is a process that plays an important role in a range of dynamic phenomena involving the dissipation of mechanical energy in both individual CNTs and CNT-based materials. The rates and channels through which acoustic energy deposited instantaneously in individual CNTs is dissipated are investigated in a series of atomistic molecular dynamics simulations. Several distinct regimes of energy dissipation, dependent on the initial stretching or bending deformations, are established. The onset of axial or bending buckling marks the transition from a regime of slow thermalization to a regime in which the energy associated with longitudinal and bending oscillations is rapidly damped. In the case of stretching vibrations, an intermediate regime is revealed in which dynamic coupling between longitudinal vibrational modes and the radial “squash” mode causes delayed axial buckling followed by a rapid transfer of energy to high-frequency vibrations. The results of the atomistic simulations are used in the design and parameterization of a “heat bath” description of thermal energy in a mesoscopic model, which is capable of simulating systems consisting of thousands of interacting CNTs. Two complementary methods for the description of mechanical energy dissipation in the mesoscopic model are developed. The relatively slow dissipation of acoustic vibrations in the absence of buckling is described by adding a damping force to the equations of motion of the dynamic elements of the mesoscopic model. The sharp increase in the energy dissipation rate at the onset of buckling is reproduced by incorporating a hysteresis loop into the strain energy that accounts for localized thermalization in the vicinity of buckling kinks. The ability of the mesoscopic model to reproduce the complex multistep processes of acoustic energy dissipation predicted by the

  5. From the microscopic to the mesoscopic properties of lyotropic reverse hexagonal liquid crystals.

    PubMed

    Libster, Dima; Ishai, Paul Ben; Aserin, Abraham; Shoham, Gil; Garti, Nissim

    2008-03-01

    In the present study we aimed to explore a correlation between the microstructural properties of the lyotropic reverse hexagonal phase (HII) of the GMO/tricaprylin/phosphatidylcholine/water system and its mesoscopic structure. The mesoscopic organization of discontinuous and anisotropic domains was examined, in the native state, using environmental scanning electron microscopy. The topography of the HII mesophases was imaged directly in their hydrated state, as a function of aqueous-phase concentration and composition, when a proline amino acid was solubilized into the systems as a kosmotropic (water-structure maker) guest molecule. The domain structures of several dozen micrometers in size, visualized in the environmental scanning electron microscopy, were found to possess fractal characteristics, indicating a discontinuous and disordered alignment of the corresponding internal water rods on the mesoscale. On the microstructural level, SAXS measurements revealed that as water content (Cw) increases the characteristic lattice parameter of the mesophases increases as well. Using the water concentration as the mass measure of the mixtures, a scaling relationship between the lattice parameter and the concentration was found to obey a power law whereby the derived fractal dimension was the relevant exponent, confirming the causal link between the microscopic and mesoscopic organizations. The topography of the HII mesophase was found to be affected by the microstructural parameters and the composition of the samples. Thermal analysis experiments involving these systems further confirmed that the behavior of water underpins both microscopical and mesoscopic features of the systems. It was shown that both the swelling of the lattice parameter and the mesoscopic domains is correlated to the bulk water concentration in the water rods.

  6. The stability of the reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) tests on stored horse blood.

    PubMed

    Celi, P; Sullivan, M; Evans, D

    2010-02-01

    Increasing interest in the role of oxidative stress (OS) in equine medicine has highlighted the need to develop reliable methods to quantify it. In this study we describe the effect of refrigeration (at 4 degrees C) on the stability of the reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) tests carried out on 15 healthy horses. Blood samples, collected from the jugular vein, were immediately placed on ice and analysed using both the d-ROMs and BAP tests. Samples were also refrigerated at 4 degrees C and tested after 3, 7 and 24 h. The average results were similar for up to 24 h and minimal variations were found for each horse. The findings suggest that refrigeration is suitable for preserving equine blood samples for these assays and this approach will provide veterinarians with a technically simple, reliable test to measure OS under field conditions.

  7. Instrument for controlling the application of mechanical loads to biological and bicompatible test subjects

    DOEpatents

    Lintilhac, Phillip M.; Vesecky, Thompson B.

    1995-01-01

    Apparatus and methods are disclosed facilitating the application of forces and measurement of dimensions of a test subject. In one arrangement the test subject is coupled to a forcing frame and controlled forces applied thereto. Force applied to the test subject is measured and controlled. A dimensional characteristic of the test subject, such as growth, is measured by a linear variable differential transformer. The growth measurement data can be used to control the force applied. The transducer module receives force and dimensional data from the forcing frame. The transducer module is a separate, microprocessor-based unit that communicates the test data to a controller unit that controls the application of force to the test subject and receives the test data from the transducer module for force control, storage, and/or communication to the user.

  8. Instrument for controlling the application of mechanical loads to biological and bicompatible test subjects

    DOEpatents

    Lintilhac, P.M.; Vesecky, T.B.

    1995-09-19

    An apparatus and methods are disclosed facilitating the application of forces and measurement of dimensions of a test subject. In one arrangement the test subject is coupled to a forcing frame and controlled forces applied thereto. Force applied to the test subject is measured and controlled. A dimensional characteristic of the test subject, such as growth, is measured by a linear variable differential transformer. The growth measurement data can be used to control the force applied. The transducer module receives force and dimensional data from the forcing frame. The transducer module is a separate, microprocessor-based unit that communicates the test data to a controller unit that controls the application of force to the test subject and receives the test data from the transducer module for force control, storage, and/or communication to the user. 8 figs.

  9. Protozoan parasites in group-living primates: testing the biological island hypothesis.

    PubMed

    Chapman, Colin A; Bowman, Dwight D; Ghai, Ria R; Gogarten, Jan F; Goldberg, Tony L; Rothman, Jessica M; Twinomugisha, Dennis; Walsh, Chesley

    2012-06-01

    A series of articles by W.J. Freeland published in the 1970s proposed that social organization and behavioral processes were heavily influenced by parasitic infections, which led to a number of intriguing hypotheses concerning how natural selection might act on social factors because of the benefits of avoiding parasite infections. For example, Freeland [1979] showed that all individuals within a given group harbored identical gastrointestinal protozoan faunas, which led him to postulate that social groups were akin to "biological islands" and suggest how this isolation could select specific types of ranging and dispersal patterns. Here, we reexamine the biological island hypothesis by quantifying the protozoan faunas of the same primate species examined by Freeland in the same location; our results do not support this hypothesis. In contrast, we quantified two general changes in protozoan parasite community of primates in the study area of Kibale National Park, Uganda, over the nearly 35 years between sample collections: (1) the colobines found free of parasites in the early 1970s are now infected with numerous intestinal protozoan parasites and (2) groups are no longer biological islands in terms of their protozoan parasites. Whatever the ultimate explanation for these changes, our findings have implications for studies proposing selective forces shaping primate behavior and social organization.

  10. Directed self-assembly of mesoscopic components for led applications

    NASA Astrophysics Data System (ADS)

    Tkachenko, Anton

    Light-emitting diodes (LEDs) constitute a rapidly evolving and fast growing technology that promises to replace incandescent bulbs and compact fluorescent lights in many illumination applications. Large-area LED luminaires have a capability to transform lighting by providing a venue for development of smart lighting systems with additional benefits, such as visible light communications, sensing, health and productivity improvement through color temperature control, capability of creating "virtual sky" ceiling, and many others. The objective of this work is to explore directed self-assembly (DSA) approaches suitable for cost-effective assembly of large amount of LEDs and other mesoscopic (i.e. millimeter and sub-millimeter) electronic components and thus to enable manufacturing of smart lighting luminaires. Existing alternative approaches for assembly of semiconductor dies are examined including transfer printing, laser-assisted die transfer, and various directed self-assembly approaches using shape-recognition, magnetic and capillary forces, etc. After comparing their advantages and limitations, we developed two approaches to magnetic force-assisted DSA of LEDs on a large-area substrate in liquid and air medium. The first approach involves pick-up of buoyant and magnetic dies from the liquid surface onto the flexible substrate in a roll-to-roll process. The possibility of high-speed assembly of LED dies is demonstrated, but with a low yield due to the influence of the capillary force of the carrier liquid and the difficulty in ensuring reliable supply of dies to the assembly interface. To overcome the aforementioned challenges this process was modified to assemble the dies by sinking them onto the receiving substrate with a stencil mask on top, demonstrating LED assembly with a very low error rate but at a lower speed. A solder-assisted self-alignment is used to further improve placement precision and to ensure the proper orientation of the dies. The second

  11. Theory of FID NMR Signal Dephasing Induced by Mesoscopic Magnetic Field Inhomogeneities in Biological Systems

    NASA Astrophysics Data System (ADS)

    Sukstanskii, Alexander L.; Yablonskiy, Dmitriy A.

    2001-07-01

    A theory of the NMR signal dephasing due to the presence of tissue-specific magnetic field inhomogeneities is developed for a two-compartment model. Randomly distributed magnetized objects of finite size embedded in a given media are modeled by ellipsoids of revolution (prolate and oblate spheroids). The model can be applied for describing blood vessels in a tissue, red blood cells in the blood, marrow within trabecular bones, etc. The time dependence of the dephasing function connected with the spins inside of the objects, si, is shown to be expressed by Fresnel functions and creates a powder-type signal in the frequency domain. The short-time regime of the dephasing function for spins outside the objects, se, is always characterized by Gaussian time dependence, se∼exp[-ζk(t/tc)2], with ζ being a volume fraction occupied by the objects, tc being a characteristic dephasing time, and the coefficient k depending on the ellipsoid's shape through the aspect ratio of its axes (a/c). The long-time asymptotic behavior of se is always "quasispherical"-linear exponential in time, se∼ exp(-ζCt/tc), with the same "spherical" decay rate for any ellipsoidal shape. For long prolate spheroids (a/c)«1, there exists an intermediate characteristic regime with a linear exponential time behavior and an aspect-ratio-dependent decay rate smaller than (ζC/tc).

  12. Biological testing of sediment for the Olympia Harbor Navigation Improvement Project, 1988: Geoduck, amphipod, and echinoderm bioassays

    SciTech Connect

    Ward, J.A.; Word, J.Q.; Antrim, L.D.

    1989-05-01

    The Olympia Harbor Navigation Improvement Project requires the dredging of approximately 330,000 cubic yards (cy) of sediment from the harbor entrance channel and 205,185 cy from the turning basin. Puget Sound Dredged Disposal Analysis (PSDDA) partial characterization studies were used to plan a full sediment characterization in which chemical analyses and biological testing of sediments evaluated the suitability of the dredged material for unconfined, open-water disposal. The US Army Corps of Engineers (COE), Seattle District, contracted with NOAA/NMFS, Environmental Conservation Division, to perform the chemical analysis and Microtox bioassay tests, and with the Battelle/Marine Sciences Laboratory (MSL) in Sequim to perform flow-through solid-phase bioassays utilizing juvenile (8 to 10 mm) geoduck clams, Panopea generosa, and static solid phase bioassays using the phoxocephalid amphipod, Rhepoxynius abronius, developing embryos and gametes of the purple sea urchin, Strongylocentrotus purpuratus, and the larvae of the Pacific oyster Crassostrea gigas. When the results of the biological tests were evaluated under PSDDA guidelines, it was found that all the tested sediment treatments from Olympia Harbor are suitable for unconfined open-water disposal. 14 refs., 12 figs., 3 tabs.

  13. Biological alternatives to chemical identification for the ecotoxicological assessment of industrial effluents: The RTG-2 in vitro cytotoxicity test

    SciTech Connect

    Castano, A. . Centro de Sanidad Ambiental); Vega, M.; Blazquez, T.; Tarazona, J.V. )

    1994-10-01

    Ecotoxicology is concerned with the effects of chemicals on biological systems. Identifying components of complex aqueous effluents poses special problems, and can be useless if there is a lack of information on the biological effects of the identified chemicals. Toxicity-based (bioassay-directed) sample fractionation can be very useful, but the small amount of fractioned material is a constraint that can be solved by using in vitro tests. The RTG-2 in vitro cytotoxicity test has been used to assess (a) the efficacy of a treatment plant in the aeronautics industry and (b) the exposure of fish and molluscs cultured in Esteiro Bay to the effluent of a fish-processing factory. Ecotoxicological assessments could be done without identifying the responsible chemicals. The RTG-2 test was used in combination with concentration/fractionation procedures. It proved that the toxicity of the liquid wastes from the aeronautics industry was eliminated by the treatment, and that molluscs and fish reared in Esteiro Bay had accumulated toxic chemicals dumped by the fish-processing factory. A combination of the RTG-2 cytotoxicity test and HPLC proved to give useful information even for chemicals not identified by GC-MS.

  14. Planar biaxial testing of soft biological tissue using rakes: A critical analysis of protocol and fitting process.

    PubMed

    Fehervary, Heleen; Smoljkić, Marija; Vander Sloten, Jos; Famaey, Nele

    2016-08-01

    Mechanical characterization of soft biological tissue is becoming more and more prevalent. Despite the growing use of planar biaxial testing for soft tissue characterization, testing conditions and subsequent data analysis have not been standardized and vary widely. This also influences the quality of the result of the parameter fitting. Moreover, the testing conditions and data analysis are often not or incompletely reported, which impedes the proper comparison of parameters obtained from different studies. With a focus on planar biaxial tests using rakes, this paper investigates varying testing conditions and varying data analysis methods and their effect on the quality of the parameter fitting results. By means of a series of finite element simulations, aspects such as number of rakes, rakes׳ width, loading protocol, constitutive model, material stiffness and anisotropy are evaluated based on the degree of homogeneity of the stress field, and on the correlation between the experimentally obtained stress and the stress derived from the constitutive model. When calculating the aforementioned stresses, different definitions of the section width and deformation gradient are used in literature, each of which are looked into. Apart from this degree of homogeneity and correlation, also the effect on the quality of the parameter fitting result is evaluated. The results show that inhomogeneities can be reduced to a minimum for wise choices of testing conditions and analysis methods, but never completely eliminated. Therefore, a new parameter optimization procedure is proposed that corrects for the inhomogeneities in the stress field and induces significant improvements to the fitting results. Recommendations are made for best practice in rake-based planar biaxial testing of soft biological tissues and subsequent parameter fitting, and guidelines are formulated for reporting thereof in publications.

  15. Experimental Work in Biology: Book 1, Food Tests; Book 2, Enzymes; Book 3, Soil.

    ERIC Educational Resources Information Center

    Mackean, D. G.

    Laboratory experiments are presented in these first three manuals of a six-volume series for use at the 12- to 16-year-old, or British CSE, level. On the subject of food tests, 17 exercises are prepared in connection with Biuret reactions, starch and emulsion tests, Millon's and Benedict's reagents, reagent sensitivity, and calorific values and…

  16. Alignment between High School Biology Curriculum Standard and the Standardised Tests of Four Provinces in China

    ERIC Educational Resources Information Center

    Lu, Qun; Liu, Enshan

    2012-01-01

    With the development and implementation of new curriculum standards, the field tests of education reform in senior high schools began in 2004 in four pilot provinces in mainland China. After five years of the reform, it is necessary to know how and to what extent the curriculum standard guides test classroom instruction. The present study was…

  17. 40 CFR 230.61 - Chemical, biological, and physical evaluation and testing.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... be obtained from bioassays in lieu of chemical tests. (2) Water column effects. (i) Sediments... locations within the sediment. An elutriate test may be used to predict the effect on water quality due to release of contaminants from the sediment to the water column. However, in the case of fill...

  18. 40 CFR 230.61 - Chemical, biological, and physical evaluation and testing.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... be obtained from bioassays in lieu of chemical tests. (2) Water column effects. (i) Sediments... locations within the sediment. An elutriate test may be used to predict the effect on water quality due to release of contaminants from the sediment to the water column. However, in the case of fill...

  19. 40 CFR 230.61 - Chemical, biological, and physical evaluation and testing.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... be obtained from bioassays in lieu of chemical tests. (2) Water column effects. (i) Sediments... locations within the sediment. An elutriate test may be used to predict the effect on water quality due to release of contaminants from the sediment to the water column. However, in the case of fill...

  20. Proposed biological testing methods for the United States incineration-at-sea research program

    SciTech Connect

    Strobel, C.J.; Gentile, J.H.; Schimmel, S.C.; Carr, R.S.; Williams, J.W.

    1988-01-01

    As part of the United States Environmental Protection Agency's Incineration-at-Sea research program, a suite of toxicity tests has been selected for assessing the toxicity of incinerator emissions generated during the combustion of chlorinated wastes. The test organisms for the five short-term chronic tests are the inland silverside, Menidia beryllina, the myside Mysidopsis bahia, the red macroalga Champia parvula, the polychaete Dinophilus gyrociliatus, and gametes from the sea urchin Arbacia punctulata. The durations of individual tests range from 2 hours to 7 days. The endpoints include survival, growth and reproductive effects. The results have demonstrated that the proposed methodologies can be used to test the toxicity of gaseous emissions, and that there appears to be no significant toxicity associated with the combustion products of a carrier fuel oil.

  1. Effect of chemical and biological surfactants on activated sludge of MBR system: microscopic analysis and foam test.

    PubMed

    Capodici, Marco; Di Bella, Gaetano; Nicosia, Salvatore; Torregrossa, Michele

    2015-02-01

    A bench-scale MBR unit was operated, under stressing condition, with the aim of stimulating the onset of foaming in the activated sludge. Possible synergies between synthetic surfactants in the wastewater and biological surfactants (Extra-Cellular Polymeric Substances, EPSs) were investigated by changing C/N ratio. The growth of filamentous bacteria was also discussed. The MBR unit provided satisfactory overall carbon removal overall efficiencies: in particular, synthetic surfactants were removed with efficiency higher than 90% and 95% for non-ionic and ionic surfactants, respectively. Lab investigation suggested also the importance to reduce synthetic surfactants presence entering into mixed liquor: otherwise, their presence can significantly worsen the natural foaming caused by biological surfactants (EPSs) produced by bacteria. Finally, a new analytic method based on "ink test" has been proposed as a useful tool to achieve a valuation of EPSs bound fraction.

  2. Radiotoxicity of gadolinium-148 and radium-223 in mouse testes: Relative biological effectiveness of alpha-particle emitters in vivo

    SciTech Connect

    Howell, R.W.; Goddu, S.M.; Narra, V.R.

    1997-03-01

    The biological effects of radionuclides that emit {alpha} particles are of considerable interest in view of their potential for therapy and their presence in the environment. The present work is a continuation of our ongoing effort to study the radiotoxicity of {alpha}-particle emitters in vivo using the survival of murine testicular sperm heads as the biological end point. Specifically, the relative biological effectiveness (RBE) of very low-energy {alpha} particles (3.2 MeV) emitted by {sup 148}Gd is investigated and determined to be 7.4 {+-} 2.4 when compared to the effects of acute external 120 kVp X rays. This datum, in conjunction with our earlier results for {sup 210}Po and {sup 212}Pb in equilibrium with its daughters, is used to revise and extend the range of validity of our previous RBE-energy relationship for {alpha} particles emitted by tissue-incorporated radionuclides. The new empirical relationship is given by RBE{sub {alpha}} = 9.14 - 0.510 E{sub {alpha}}, where 3 < E{sub {alpha}} < 9 MeV. The validity of this empirical relationship is tested by determining the RBE of the prolific {alpha}-particle emitter {sup 223}Ra (in equilibrium with its daughters) experimentally in the same biological model and comparing the value obtained experimentally with the predicted value. The resulting RBE values are 5.4 {+-} 0.9 and 5.6, respectively. This close agreement strongly supports the adequacy of the empirical RBE-E{sub {alpha}} relationship to predict the biological effects of {alpha}-particle emitters in vivo. 42 refs., 5 figs., 1 tab.

  3. Radiotoxicity of Gadolinium-148 and Radium-223 in Mouse Testes: Relative Biological Effectiveness of Alpha-Particle Emitters In Vivo

    PubMed Central

    Howell, Roger W.; Goddu, S. Murty; Narra, Venkat R.; Fisher, Darrell R.; Schenter, Robert E.; Rao, Dandamudi V.

    2012-01-01

    The biological effects of radionuclides that emit α particles are of considerable interest in view of their potential for therapy and their presence in the environment. The present work is a continuation of our ongoing effort to study the radiotoxicity of α-particle emitters in vivo using the survival of murine testicular sperm heads as the biological end point. Specifically, the relative biological effectiveness (RBE) of very low-energy α particles (3.2 MeV) emitted by 148Gd is investigated and determined to be 7.4 ± 2.4 when compared to the effects of acute external 120 kVp X rays. This datum, in conjunction with our earlier results for 210Po and 212Pb in equilibrium with its daughters, is used to revise and extend the range of validity of our previous RBE–energy relationship for α particles emitted by tissue-incorporated radionuclides. The new empirical relationship is given by RBEα = 9.14 − 0.510 Eα, where 3 < Eα < 9 MeV. The validity of this empirical relationship is tested by determining the RBE of the prolific α-particle emitter 223Ra (in equilibrium with its daughters) experimentally in the same biological model and comparing the value obtained experimentally with the predicted value. The resulting RBE values are 5.4 ± 0.9 and 5.6, respectively. This close agreement strongly supports the adequacy of the empirical RBE-Eα relationship to predict the biological effects of α-particle emitters in Vivo. PMID:9052681

  4. Single and multiple streamer DBD micro-discharges for testing inactivation of biologically contaminated surfaces

    NASA Astrophysics Data System (ADS)

    Prukner, Vaclav; Dolezalova, Eva; Simek, Milan

    2014-10-01

    Highly reactive environment produced by atmospheric-pressure, non-equilibrium plasmas generated by surface dielectric barrier discharges (SDBDs) may be used for inactivation of biologically contaminated surfaces. We investigated decontamination efficiency of reactive environment produced by single/multiple surface streamer micro-discharge driven by amplitude-modulated AC power in coplanar electrode geometry on biologically contaminated surface by Escherichia coli. The discharges were fed by synthetic air with water vapor admixtures at atmospheric pressure, time of treatment was set from 10 second to 10 minutes, diameters of used SDBD electrodes (single and multiple streamer) and homogeneously contaminated disc samples were equal (25 mm), the distance between the electrode and contaminated surface was 2 mm. Both a conventional cultivation and fluorescent method LIVE/DEAD Bacterial Viability kit were applied to estimate counts of bacteria after the plasma treatment. Inactivation was effective and bacteria partly lost ability to grow and became injured and viable/active but non-cultivable (VBNC/ABNC). Work was supported by the MEYS under Project LD13010, VES13 COST CZ (COST Action MP 1101).

  5. Dispersed oil toxicity tests with biological species indigenous to the Gulf of Mexico. Final report

    SciTech Connect

    Fucik, K.W.; Carr, K.A.; Balcom, B.J.

    1994-08-01

    Static and flowthrough aquatic acute toxicity testing protocols were utilized on eggs and larvae of seven commercially important invertebrates and fishes from the Gulf of Mexico. Test organisms were exposed to Central and Western Gulf oils, dispersed oil, and Corexit 9527. Species included brown shrimp (Penaeus aztecus), white shrimp (Penaeus setiferus), blue crab (Callinectes sapidus), eastern oyster (Crassostrea virginica), red drum (Sciaenops ocellatus), inland silverside (Menidia berylina), and spot (Leiosomus xanthurus). Atlantic menhaden (Brevoortia tyrannus) was also tested because gulf menhaden were not available. Mysids (Mysidopsis bahia) were evaluated as part of a chronic toxicity assessment.

  6. Fully printable transparent monolithic solid-state dye-sensitized solar cell with mesoscopic indium tin oxide counter electrode.

    PubMed

    Yang, Ying; Ri, Kwangho; Rong, Yaoguang; Liu, Linfeng; Liu, Tongfa; Hu, Min; Li, Xiong; Han, Hongwei

    2014-09-01

    We present a new transparent monolithic mesoscopic solid-state dye-sensitized solar cell based on trilamellar films of mesoscopic TiO2 nanocrystalline photoanode, a ZrO2 insulating layer and an indium tin oxide counter electrode (ITO-CE), which were screen-printed layer by layer on a single substrate. When the thickness of the ITO-CE was optimized to 2.1 μm, this very simple and fully printable solid-state DSSC with D102 dye and spiro-OMeTAD hole transport materials presents efficiencies of 1.73% when irradiated from the front side and 1.06% when irradiated from the rear side under a standard simulated sunlight condition (AM 1.5 Global, 100 mW cm(-2)). Higher parameters could be expected with a better transparent mesoscopic counter electrode and hole conductor for the printable monolithic mesoscopic solid-state DSSC.

  7. Biological and analytical variations of 16 parameters related to coagulation screening tests and the activity of coagulation factors.

    PubMed

    Chen, Qian; Shou, Weiling; Wu, Wei; Guo, Ye; Zhang, Yujuan; Huang, Chunmei; Cui, Wei

    2015-04-01

    To accurately estimate longitudinal changes in individuals, it is important to take into consideration the biological variability of the measurement. The few studies available on the biological variations of coagulation parameters are mostly outdated. We confirmed the published results using modern, fully automated methods. Furthermore, we added data for additional coagulation parameters. At 8:00 am, 12:00 pm, and 4:00 pm on days 1, 3, and 5, venous blood was collected from 31 healthy volunteers. A total of 16 parameters related to coagulation screening tests as well as the activity of coagulation factors were analyzed; these included prothrombin time, fibrinogen (Fbg), activated partial thromboplastin time, thrombin time, international normalized ratio, prothrombin time activity, activated partial thromboplastin time ratio, fibrin(-ogen) degradation products, as well as the activity of factor II, factor V, factor VII, factor VIII, factor IX, and factor X. All intraindividual coefficients of variation (CVI) values for the parameters of the screening tests (except Fbg) were less than 5%. Conversely, the CVI values for the activity of coagulation factors were all greater than 5%. In addition, we calculated the reference change value to determine whether a significant difference exists between two test results from the same individual.

  8. Mesoscopic modeling of cancer photothermal therapy using single-walled carbon nanotubes and near infrared radiation: insights through an off-lattice Monte Carlo approach.

    PubMed

    Gong, Feng; Hongyan, Zhang; Papavassiliou, Dimitrios V; Bui, Khoa; Lim, Christina; Duong, Hai M

    2014-05-23

    Single-walled carbon nanotubes (SWNTs) are promising heating agents in cancer photothermal therapy when under near infrared radiation, yet few efforts have been focused on the quantitative understanding of the photothermal energy conversion in biological systems. In this article, a mesoscopic study that takes into account SWNT morphologies (diameter and aspect ratio) and dispersions (orientation and concentration), as well as thermal boundary resistance, is performed by means of an off-lattice Monte Carlo simulation. Results indicate that SWNTs with orientation perpendicular to the laser, smaller diameter and better dispersion have higher heating efficiency in cancer photothermal therapy. Thermal boundary resistances greatly inhibit thermal energy transfer away from SWNTs, thereby affecting their heating efficiency. Through appropriate interfacial modification around SWNTs, compared to the surrounding healthy tissue, a higher temperature of the cancer cell can be achieved, resulting in more effective cancer photothermal therapy. These findings promise to bridge the gap between macroscopic and microscopic computational studies of cancer photothermal therapy.

  9. Ecological evaluation of proposed dredged material from the John F. Baldwin Ship Channel: Phase 3 -- biological testing

    SciTech Connect

    Kohn, N.P.; Karle, L.M.; Pinza, M.R.; Mayhew, H.L.; White, P.J.; Gruendell, B.D.; Word, J.Q.

    1993-10-01

    The John F. Baldwin Ship Channel is a 28-mile-long portion of the San Francisco Bay to Stockton Ship Channel, the primary shipping lane through San Francisco Bay and Delta. The San Francisco District of the US Army Corps of Engineers (USACE) is responsible for construction of the John F. Baldwin Ship Channel, which is authorized to be deepened to a project depth of {minus}45 ft relative to mean lower low water (MLLW). Approximately 8.5 million cubic yards (mcy) of sediment will be removed from the channel to reach this project depth. The USACE requested Battelle/Marine Sciences Laboratory (MSL) to conduct testing for ocean disposal under the guidelines in Evaluation of Dredged Material Proposed for Ocean Disposal-Testing Manual (EPA/USACE 1991). This testing manual contains a tiered evaluation approach developed specifically for ocean disposal of dredged material at a selected site. In this study, John F. Baldwin Ship Channel sediments were evaluated under the Tier III (biological) testing guidance, which is considered to be highly stringent and protective of the environment. The Tier III guidance for ocean disposal testing requires tests of water column effects, (following dredged material disposal), deposited sediment toxicity, and bioaccumulation of contaminants from deposited sediment (dredged material).

  10. Solubilization of poorly soluble lichen metabolites for biological testing on cell lines.

    PubMed

    Kristmundsdóttir, Thórdís; Jónsdóttir, Elsa; Ogmundsdóttir, Helga M; Ingólfsdóttir, Kristín

    2005-04-01

    The depside atranorin and depsidone fumarprotocetraric acid, isolated from the lichens Stereocaulon alpinum and Cetraria islandica, respectively, were chosen as prototypes for poorly soluble natural compounds in an effort to facilitate testing in pharmacological models. Solubilizing agents previously identified as being non-toxic towards a malignant leukemic (K-562) cell line and suitable for testing of anti-proliferative activity of the dibenzofuran lichen metabolite (+)-usnic acid were used in solubilization studies of the depside and depsidone. Cyclodextrin derivatives were found to be most suitable for solubilizing the lichen compounds, the greatest rise in solubility being witnessed for fumarprotocetraric acid, increasing almost 300-fold from 0.03 mg/ml in water to 8.98 mg/ml in 10% 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD). Subsequently, the lichen compounds, including (+)-usnic acid, were solubilized in 10% HPbetaCD and tested for effects on three malignant human cell lines; T-47D (breast), Panc-1 (pancreas) and PC-3 (prostate) in a standard proliferation assay. Atranorin and fumarprotocetraric acid did not exhibit anti-proliferative effects but usnic acid was active against all test cell lines with EC50 values of 4.3-8.2 microg/ml. The non-toxic solubilizing agents used in this study could prove useful for pharmacological testing of other poorly soluble natural products. PMID:15784343

  11. 40 CFR 230.61 - Chemical, biological, and physical evaluation and testing.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... potential effects on the water column and on communities of aquatic organisms. (1) Evaluation of chemical... further analyses and how the results of the analyses will be of value in evaluating potential... be obtained from bioassays in lieu of chemical tests. (2) Water column effects. (i)...

  12. 40 CFR 230.61 - Chemical, biological, and physical evaluation and testing.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... potential effects on the water column and on communities of aquatic organisms. (1) Evaluation of chemical... further analyses and how the results of the analyses will be of value in evaluating potential... be obtained from bioassays in lieu of chemical tests. (2) Water column effects. (i)...

  13. Development and testing of new biologically-based polymers as advanced biocompatible contact lenses

    SciTech Connect

    Bertozzi, Carolyn R.

    2000-06-01

    Nature has evolved complex and elegant materials well suited to fulfill a myriad of functions. Lubricants, structural scaffolds and protective sheaths can all be found in nature, and these provide a rich source of inspiration for the rational design of materials for biomedical applications. Many biological materials are based in some fashion on hydrogels, the crosslinked polymers that absorb and hold water. Biological hydrogels contribute to processes as diverse as mineral nucleation during bone growth and protection and hydration of the cell surface. The carbohydrate layer that coats all living cells, often referred to as the glycocalyx, has hydrogel-like properties that keep cell surfaces well hydrated, segregated from neighboring cells, and resistant to non-specific protein deposition. With the molecular details of cell surface carbohydrates now in hand, adaptation of these structural motifs to synthetic materials is an appealing strategy for improving biocompatibility. The goal of this collaborative project between Prof. Bertozzi's research group, the Center for Advanced Materials at Lawrence Berkeley National Laboratory and Sunsoft Corporation was the design, synthesis and characterization of novel hydrogel polymers for improved soft contact lens materials. Our efforts were motivated by the urgent need for improved materials that allow extended wear, and essential feature for those whose occupation requires the use of contact lenses rather than traditional spectacles. Our strategy was to transplant the chemical features of cell surface molecules into contact lens materials so that they more closely resemble the tissue in which they reside. Specifically, we integrated carbohydrate molecules similar to those found on cell surfaces, and sulfoxide materials inspired by the properties of the carbohydrates, into hydrogels composed of biocompatible and manufacturable substrates. The new materials were characterized with respect to surface and bulk hydrophilicity, and

  14. Mesoscopic Hamiltonian for the fluctuations of adsorbed Lennard-Jones liquid films.

    PubMed

    Fernández, Eva M; Chacón, Enrique; MacDowell, Luis G; Tarazona, Pedro

    2015-06-01

    We use Monte Carlo simulations of a Lennard-Jones fluid adsorbed on a short-range planar wall substrate to study the fluctuations in the thickness of the wetting layer, and we get a quantitative and consistent characterization of their mesoscopic Hamiltonian, H[ξ]. We have observed important finite-size effects, which were hampering the analysis of previous results obtained with smaller systems. The results presented here support an appealing simple functional form for H[ξ], close but not exactly equal to the theoretical nonlocal proposal made on the basis a generic density-functional analysis by Parry and coworkers. We have analyzed systems under different wetting conditions, as a proof of principle for a method that provides a quantitative bridge between the molecular interactions and the phenomenology of wetting films at mesoscopic scales. PMID:26172722

  15. Local transport measurements at mesoscopic length scales using scanning tunneling potentiometry.

    PubMed

    Wang, Weigang; Munakata, Ko; Rozler, Michael; Beasley, Malcolm R

    2013-06-01

    Under mesoscopic conditions, the transport potential on a thin film carrying a current is theoretically expected to bear spatial variation due to quantum interference. Scanning tunneling potentiometry is the ideal tool to investigate such variation, by virtue of its high spatial resolution. We report in this Letter the first detailed measurement of transport potential under mesoscopic conditions. Epitaxial graphene at a temperature of 17 K was chosen as the initial system for study because the characteristic transport length scales in this material are relatively large. Tip jumping artifacts are a major possible contribution to systematic errors; and we mitigate such problems by using custom-made slender and sharp tips manufactured by focused ion beam. In our data, we observe residual resistivity dipoles associated with topographical defects, and local peaks and dips in the potential that are not associated with topographical defects.

  16. Multiparticle Correlations in Mesoscopic Scattering: Boson Sampling, Birthday Paradox, and Hong-Ou-Mandel Profiles

    NASA Astrophysics Data System (ADS)

    Urbina, Juan-Diego; Kuipers, Jack; Matsumoto, Sho; Hummel, Quirin; Richter, Klaus

    2016-03-01

    The interplay between single-particle interference and quantum indistinguishability leads to signature correlations in many-body scattering. We uncover these with a semiclassical calculation of the transmission probabilities through mesoscopic cavities for systems of noninteracting particles. For chaotic cavities we provide the universal form of the first two moments of the transmission probabilities over ensembles of random unitary matrices, including weak localization and dephasing effects. If the incoming many-body state consists of two macroscopically occupied wave packets, their time delay drives a quantum-classical transition along a boundary determined by the bosonic birthday paradox. Mesoscopic chaotic scattering of Bose-Einstein condensates is, then, a realistic candidate to build a boson sampler and to observe the macroscopic Hong-Ou-Mandel effect.

  17. Local Transport Measurements at Mesoscopic Length Scales Using Scanning Tunneling Potentiometry

    NASA Astrophysics Data System (ADS)

    Wang, Weigang; Munakata, Ko; Rozler, Michael; Beasley, Malcolm R.

    2013-06-01

    Under mesoscopic conditions, the transport potential on a thin film carrying a current is theoretically expected to bear spatial variation due to quantum interference. Scanning tunneling potentiometry is the ideal tool to investigate such variation, by virtue of its high spatial resolution. We report in this Letter the first detailed measurement of transport potential under mesoscopic conditions. Epitaxial graphene at a temperature of 17 K was chosen as the initial system for study because the characteristic transport length scales in this material are relatively large. Tip jumping artifacts are a major possible contribution to systematic errors; and we mitigate such problems by using custom-made slender and sharp tips manufactured by focused ion beam. In our data, we observe residual resistivity dipoles associated with topographical defects, and local peaks and dips in the potential that are not associated with topographical defects.

  18. Some biological aspects of Mysidopsis juniae (Crustacea:Mysidacea) and its use in chronic toxicity tests

    SciTech Connect

    Badaro-Pedroso, C. Nipper, M.G.

    1995-12-31

    As part of the joint effort to develop marine toxicity tests with organisms abundant at the Brazilian coast, some aspects for the laboratory culture of M. juniae and its sensitivity to single chemicals were studied. Organisms fed a mixture of brine shrimp (Artemia sp.) nauplii and the microalgae Isochrysis galbana reached sexual maturity 10 days before animals fed brine shrimp nauplii only. Under best conditions, sexual maturity was reached on the 9th--11th day and newborn mysids hatched on the 16th--18th day, Short-term chronic toxicity tests were initiated with 7-day old mysids and exposure time was 11 days, with growth (length and dry weight) as test endpoints. Experiments were undertaken with zinc, copper, and ammonia. Zinc did not affect the organisms at concentrations between 0.018 and 0.1 mg/L, which were one order of magnitude lower than the average 96-h; LC50 value. The NOEC and LOEC values were the same for length and weight in some tests with copper and ammonia (Cu: 0.006 and 0.015 mg/L; NH{sub 3}: 0.32 and 0.87 mg/L, respectively), but revealed length as a more sensitive endpoint than weight in others (length NOEC and LOEC: 0.23 and 0.53 mgNH{sub 3}/L; weight: 0.53 and 0.99 mgNH{sub 3}/L, respectively). The authors speculate that this could be caused by time-dependent variations in the lipid content of the organisms. Length would be a steadier and more reliable endpoint for chronic toxicity tests with M. juniae. The results show that the method has potential applications for the evaluation and monitoring of contaminated marine systems along the Brazilian coast.

  19. Determining Biology Student Teachers' Cognitive Structure on the Concept of "Diffusion" through the Free Word-Association Test and the Drawing-Writing Technique

    ERIC Educational Resources Information Center

    Kurt, Hakan; Ekici, Gülay; Aktas, Murat; Aksu, Özlem

    2013-01-01

    The aim of the current study is to investigate student biology teachers' cognitive structures related to "diffusion" through the free word-association test and the drawing-writing technique. As the research design of the study, the qualitative research method was applied. The data were collected from 44 student biology teachers. The free…

  20. Effects of activated carbon amended sediment on biological responses in Chironomus riparius multi-generation testing.

    PubMed

    Nybom, Inna; Abel, Sebastian; Mäenpää, Kimmo; Akkanen, Jarkko

    2016-11-15

    The biological effects of activated carbon (AC) amendments in sediments were studied with the midge Chironomus riparius. The effects on larvae growth were studied using three different AC particles sizes (PAC: 90% <63μm, MAC: ø 63-200μm and GAC: ø 420-1700μm). The long- term effects of MAC were studied in an emergence experiment over two generations (P, F1), together with larvae growth experiment over three generations (P, F1, F2). Retarded growth and development of the larvae were observed in the two smallest particle sizes (PAC and MAC), as well as morphological changes in the gut wall microvilli layer studied from transmission electron micrographs. In addition, at high AC treatments the larvae reaching fourth instar stage were of a smaller size compared to the controls. With PAC treatment AC amendment dosages higher than 1% of sediment dry weight induced mortality. In the emergence experiment there was an indication of a delay in F1 generation emergence. Male dry weight (dw) in P generation was significantly reduced in the 2.5% MAC treatment. The effects of AC amendments were more obvious in the C. riparius larvae compared to the effects seen in emerging adults exposed to AC-amended sediment during the larval stage. PMID:27450330

  1. Testing Foundations of Biological Scaling Theory Using Automated Measurements of Vascular Networks

    PubMed Central

    Newberry, Mitchell G; Ennis, Daniel B; Savage, Van M

    2015-01-01

    Scientists have long sought to understand how vascular networks supply blood and oxygen to cells throughout the body. Recent work focuses on principles that constrain how vessel size changes through branching generations from the aorta to capillaries and uses scaling exponents to quantify these changes. Prominent scaling theories predict that combinations of these exponents explain how metabolic, growth, and other biological rates vary with body size. Nevertheless, direct measurements of individual vessel segments have been limited because existing techniques for measuring vasculature are invasive, time consuming, and technically difficult. We developed software that extracts the length, radius, and connectivity of in vivo vessels from contrast-enhanced 3D Magnetic Resonance Angiography. Using data from 20 human subjects, we calculated scaling exponents by four methods—two derived from local properties of branching junctions and two from whole-network properties. Although these methods are often used interchangeably in the literature, we do not find general agreement between these methods, particularly for vessel lengths. Measurements for length of vessels also diverge from theoretical values, but those for radius show stronger agreement. Our results demonstrate that vascular network models cannot ignore certain complexities of real vascular systems and indicate the need to discover new principles regarding vessel lengths. PMID:26317654

  2. The Acid Test for Biological Science: STAP Cells, Trust, and Replication.

    PubMed

    Lancaster, Cheryl

    2016-02-01

    In January 2014, a letter and original research article were published in Nature describing a process whereby somatic mouse cells could be converted into stem cells by subjecting them to stress. These "stimulus-triggered acquisition of pluripotency" (STAP) cells were shown to be capable of contributing to all cell types of a developing embryo, and extra-embryonic tissues. The lead author of the publications, Haruko Obokata, became an overnight celebrity in Japan, where she was dubbed the new face of Japanese science. However, in the weeks that followed publication of the research, issues arose. Other laboratories and researchers (including authors on the original papers) found that they were unable to replicate Obokata et al.'s work. Closer scrutiny of the papers by the scientific community also suggested that there was manipulation of images that had been published, and Obokata was accused of misconduct. Those who should have been supervising her work (also her co-authors on the publications) were also heavily criticised. The STAP cell saga of 2014 is used as an example to highlight the importance of trust and replication in twenty-first century biological science. The role of trust in the scientific community is highlighted, and the effects on interactions between science and the public examined. Similarly, this essay aims to highlight the importance of replication, and how this is understood by researchers, the media, and the public. The expected behaviour of scientists in the twenty-first century is now more closely scrutinised.

  3. 1994 Baseline biological studies for the Device Assembly Facility at the Nevada Test Site

    SciTech Connect

    Townsend, Y.E.; Woodward, B.D.; Hunter, R.B.; Greger, P.D.; Saethre, M.B.

    1995-02-01

    This report describes environmental work performed at the Device Assembly Facility (DAF) in 1994 by the Basic Environmental Monitoring and Compliance Program (BECAMP). The DAF is located near the Mojave-Great Basin desert transition zone 27 km north of Mercury. The area immediately around the DAF building complex is a gentle slope cut by 1 to 3 m deep arroyos, and occupied by transitional vegetation. In 1994, construction activities were largely limited to work inside the perimeter fence. The DAF was still in a preoperational mode in 1994, and no nuclear materials were present. The DAF facilities were being occupied so there was water in the sewage settling pond, and the roads and lights were in use. Sampling activities in 1994 represent the first year in the proposed monitoring scheme. The proposed biological monitoring plan gives detailed experimental protocols. Plant, lizard, tortoise, small mammal, and bird surveys were performed in 1994. The authors briefly outline procedures employed in 1994. Studies performed on each taxon are reviewed separately then summarized in a concluding section.

  4. Biological process design and pilot testing for a carbon oxidation, nitrification, and denitrification system

    SciTech Connect

    Givens, S.W.; Brown, E.V. ); Gelman, S.R. ); Grady, C.P.L. Jr. ); Skedsvold, D.A. )

    1991-05-01

    In response to a new NPDES permit incorporating Organic Chemical, Plastic, and Synthetic Fiber (OCPSF) effluent limits for BOD (carbonaceous and nitrogenous), TSS, and priority pollutants, a treatability study was conducted to establish design criteria for a new process wastewater treatment plant for DSM Chemicals North America, Inc. The permit also requires partial removal of total nitrogen. Based on the discharge criteria, a two-stage biological process configuration was selected. The configuration consisted of an anoxic followed by an aerobic reactor with mixed liquor recirculation. To establish design criteria, a two-phase study was conducted. The first phase involved determining wastewater characteristics and kinetic and stoichiometric coefficients. These values were used as input to Simulation of Single-Sludge Processes (SSSP), a computer model that was used to evaluate potential process configurations. In the second phase, a pilot-scale system was operated to verify performance. With a volume distribution of 40% anoxic and 60% aerobic and recirculation ratio of 2, BOD, COD, and total nitrogen removal efficiencies of 99, 88, and 80% were obtained, respectively. Approximately 84% of the biodegradable COD was removed through denitrification.

  5. Effects of activated carbon amended sediment on biological responses in Chironomus riparius multi-generation testing.

    PubMed

    Nybom, Inna; Abel, Sebastian; Mäenpää, Kimmo; Akkanen, Jarkko

    2016-11-15

    The biological effects of activated carbon (AC) amendments in sediments were studied with the midge Chironomus riparius. The effects on larvae growth were studied using three different AC particles sizes (PAC: 90% <63μm, MAC: ø 63-200μm and GAC: ø 420-1700μm). The long- term effects of MAC were studied in an emergence experiment over two generations (P, F1), together with larvae growth experiment over three generations (P, F1, F2). Retarded growth and development of the larvae were observed in the two smallest particle sizes (PAC and MAC), as well as morphological changes in the gut wall microvilli layer studied from transmission electron micrographs. In addition, at high AC treatments the larvae reaching fourth instar stage were of a smaller size compared to the controls. With PAC treatment AC amendment dosages higher than 1% of sediment dry weight induced mortality. In the emergence experiment there was an indication of a delay in F1 generation emergence. Male dry weight (dw) in P generation was significantly reduced in the 2.5% MAC treatment. The effects of AC amendments were more obvious in the C. riparius larvae compared to the effects seen in emerging adults exposed to AC-amended sediment during the larval stage.

  6. Fractal Tomlinson model for mesoscopic friction: from microscopic velocity-dependent damping to macroscopic Coulomb friction.

    PubMed

    Filippov, A E; Popov, V L

    2007-02-01

    A modified Tomlinson equation with fractal potential is studied. The effective potential is numerically generated and its mesoscopic structure is gradually adjusted to different scales by a number of Fourier modes. It is shown that with the change of scale the intensity of velocity-dependent damping in an effective Langevin equation can be gradually substituted by an equivalent constant "dry friction." For smooth macrosopic surfaces the effective equation completely reduces to the well known Coulomb law. PMID:17358452

  7. The influence of society's mesoscopic structure on the rate of epidemic spreading

    NASA Astrophysics Data System (ADS)

    Kashisaz, Hadi; Darooneh, Amir H.

    2016-06-01

    In this study, we investigate the role of the mesoscopic structural properties of a scale-free social network on the contagion spreading. We focus on both the exponent of power-law community size distribution function (β) and the mixing parameter (μ). Findings show that increasing β reduces the rate of epidemic spreading. On the other hand, increasing μ increases the rate of epidemic spreading. Two innovating parameters, Temperature and cos θ , are introduced here to analyze these effects.

  8. Mesoscopic tomography imaging of reporter genes in thick printed tissue constructs

    NASA Astrophysics Data System (ADS)

    Ozturk, Mehmet S.; Lee, Vivian K.; Zhao, Lingling; Dai, Guohoa; Intes, Xavier

    2013-06-01

    We report an application of Mesoscopic Fluorescence Molecular Tomography to 3D tissue engineering construct. Engineered thick tissue was hosting two 3D printed vasculatures. The channels were formed by live cells, expressing GFP and mCherry reporter genes, embedded in 3mm turbid media. Tissue and cells kept in a 3mm thick perfusion chamber during the entire imaging process which took less than 5 minutes.

  9. Wide bandwidth SIN tunnel junction thermometers for mesoscopic calorimetry and bolometry

    NASA Astrophysics Data System (ADS)

    Schmidt, D. R.; Yung, C. S.; Cleland, A. N.

    2003-03-01

    Thermodynamic measurements of mesoscopic devices require sensitive thermometers which are small enough to allow integration with nanostructures. Superconductor-insulator-normal metal (SIN) tunnel junctions meet these stringent requirements. We have achieved high bandwidth ( ˜10 MHz) readout of the inherently resistive SIN thermometer by embedding the junction in an LC resonator (f_res ˜ 350 MHz). We will discuss our implementation of this new technology and the implications for radio-frequency calorimetry of mesocopic devices and bolometetry.

  10. Observation of Paramagnetic Supercurrent in Mesoscopic Superconducting Rings and Disks Using Multiple-Small Method

    NASA Astrophysics Data System (ADS)

    Kanda, A.; Baelus, B. J.; Peeters, F. M.; Kadowaki, K.; Ootuka, Y.

    2005-08-01

    Responses of mesoscopic superconducting rings and disks to perpendicular magnetic fields are studied by using the multiple-small-tunnel-junction method, in which transport properties of several small tunnel junctions attached to the sample are measured simultaneously. This allows us for a direct experimental observation of the paramagnetic supercurrent, which is closely related to the paramagnetic Meissner effect. The results are compared with numerical results based on the nonlinear Ginzburg-Landau theory.

  11. The influence of society's mesoscopic structure on the rate of epidemic spreading.

    PubMed

    Kashisaz, Hadi; Darooneh, Amir H

    2016-06-01

    In this study, we investigate the role of the mesoscopic structural properties of a scale-free social network on the contagion spreading. We focus on both the exponent of power-law community size distribution function (β) and the mixing parameter (μ). Findings show that increasing β reduces the rate of epidemic spreading. On the other hand, increasing μ increases the rate of epidemic spreading. Two innovating parameters, Temperature and cos θ, are introduced here to analyze these effects. PMID:27368779

  12. Biologic surveys for the Sandia National Laboratories, Coyote Canyon Test Complex, Kirtland Air Force Base, Albuquerque, New Mexico

    SciTech Connect

    Sullivan, R.M.; Knight, P.J.

    1994-05-25

    This report provides results of a comprehensive biologic survey performed in Coyote Canyon Test Complex (CCTC), Sandia National Laboratories (SNL), Bernalillo County, New Mexico, which was conducted during the spring and summer of 1992 and 1993. CCTC is sited on land owned by the Department of Energy (DOE) and Kirtland Air Force Base and managed by SNL. The survey covered 3,760 acres of land, most of which is rarely disturbed by CCTC operations. Absence of grazing by livestock and possibly native ungulates, and relative to the general condition of private range lands throughout New Mexico, and relative to other grazing lands in central New Mexico. Widely dispersed, low intensity use by SNL as well as prohibition of grazing has probably contributed to abundance of special status species such as grama grass cactus within the CCTC area. This report evaluates threatened and endangered species found in the area, as well as comprehensive assessment of biologic habitats. Included are analyses of potential impacts and mitigative measures designed to reduce or eliminate potential impacts. Included is a summary of CCTC program and testing activities.

  13. Testing evolutionary hypotheses about human biological adaptation using cross-cultural comparison.

    PubMed

    Mace, Ruth; Jordan, Fiona; Holden, Clare

    2003-09-01

    Physiological data from a range of human populations living in different environments can provide valuable information for testing evolutionary hypotheses about human adaptation. By taking into account the effects of population history, phylogenetic comparative methods can help us determine whether variation results from selection due to particular environmental variables. These selective forces could even be due to cultural traits-which means that gene-culture co-evolution may be occurring. In this paper, we outline two examples of the use of these approaches to test adaptive hypotheses that explain global variation in two physiological traits: the first is lactose digestion capacity in adults, and the second is population sex-ratio at birth. We show that lower than average sex ratio at birth is associated with high fertility, and argue that global variation in sex ratio at birth has evolved as a response to the high physiological costs of producing boys in high fertility populations. PMID:14527632

  14. Engineering aspects of the experiment and results of animal tests. [Apollo 17 Biological Cosmic Ray Experiment

    NASA Technical Reports Server (NTRS)

    Look, B. C.; Tremor, J. W.; Barrows, W. F.; Zabower, H. R.; Suri, K.; Park, E. G., Jr.; Durso, J. A.; Leon, H. A.; Haymaker, W.; Lindberg, R. G.

    1975-01-01

    A closed passive system independent of support from the spacecraft or its crew was developed to house five pocket mice for their flight on Apollo XVII. The reaction of potassium superoxide with carbon dioxide and water vapor to produce oxygen provided a habitable atmosphere within the experiment package. The performance of the system and the ability of the mice to survive the key preflight tests gave reasonable assurance that the mice would also withstand the Apollo flight.-

  15. ``Test kit'' for detection of biologically important anions: A salicylidene-hydrazine based Schiff base

    NASA Astrophysics Data System (ADS)

    Dalapati, Sasanka; Alam, Md Akhtarul; Jana, Sankar; Karmakar, Saswati; Guchhait, Nikhil

    2013-02-01

    Test paper coated with Schiff base [(N,N/-bis(5-nitro-salicylidene)hydrazine] receptor 1 (host) can selectively detect fluoride and acetate ions (guest) by developing yellow color which can be detected by naked-eye both in aqueous-acetonitrile solution and in solid supported test kit. UV-vis spectral analysis shows that the absorption peaks at 288 and 345 nm of receptor 1 gradually decrease its initial intensity and new red shifted absorption bands at 397 nm and 455 nm gradually appear upon addition of increasing amount of F- and AcO- ions over several tested anions such as HPO4-, Cl, Br, I, NO3-, NO2-, HSO4-, HSO3-, and ClO4- in aqueous-acetonitrile solvent. The colorimetric test results and UV-vis spectral analysis are in well agreement with 1H NMR titration results in d6-DMSO solvent. The receptor 1 forms 1:2 stable complexes with F- and AcO- ions. However, similar kind of observation obtained from UV-vis titrations in presence of AcOH corresponds to 1:1 complexation ratio indicating the formation of H-bonding interaction between the receptor and anions (F- and AcO- ions). So, the observed 1:2 complexation ratio can only be explained on the basis of deprotonation (˜1 eqv.) and H-bonding (˜1 eqv.) interactions [1]. The ratiometric analysis of host-guest complexes corroborates well with the proposed theoretical model optimization at Density Functional Theory (DFT) level.

  16. System development and early biological tests in NASA's biomass production chamber

    NASA Technical Reports Server (NTRS)

    Wheeler, R. M.; Mackowiak, C. L.; Dreschel, T. W.; Sager, J. C.; Prince, R. P.; Knott, W. M.; Hinkle, C. R.; Strayer, R. F.

    1990-01-01

    The Biomass Production Chamber at Kennedy Space Center was constructed to conduct large scale plant growth studies for NASA's CELSS program. Over the past four years, physical systems and computer control software have been continually upgraded and the degree of atmospheric leakage from the chamber has decreased from about 40 to 5 percent of the total volume per day. Early tests conducted with a limited degree of closure showed that total crop (wheat) growth from the best trays was within 80 percent of reported optimal yields for similar light levels. Yields from subsequent tests under more tightly closed conditions have not been as good--up to only 65 percent of optimal yields. Yields appear to have decreased with increasing closure, yet potential problems exist in cultural techniques and further studies are warranted. With the ability to tightly seal the chamber, quantitative data were gathered on CO2 and water exchange rates. Results showed that stand photosynthesis and transpiration reached a peak near 25 days after planting, soon after full vegetative ground cover was established. In the final phase of testing when atmospheric closure was the highest, ethylene gas levels in the chamber rose from about 10 to nearly 120 ppb. Evidence suggests that the ethylene originated from the wheat plants themselves and may have caused an epinastic rolling of the leaves, but no apparent detrimental effects on whole plant function.

  17. Hardy-Weinberg Equilibrium Testing of Biological Ascertainment for Mendelian Randomization Studies

    PubMed Central

    Rodriguez, Santiago; Gaunt, Tom R.

    2009-01-01

    Mendelian randomization (MR) permits causal inference between exposures and a disease. It can be compared with randomized controlled trials. Whereas in a randomized controlled trial the randomization occurs at entry into the trial, in MR the randomization occurs during gamete formation and conception. Several factors, including time since conception and sampling variation, are relevant to the interpretation of an MR test. Particularly important is consideration of the “missingness” of genotypes that can be originated by chance, genotyping errors, or clinical ascertainment. Testing for Hardy-Weinberg equilibrium (HWE) is a genetic approach that permits evaluation of missingness. In this paper, the authors demonstrate evidence of nonconformity with HWE in real data. They also perform simulations to characterize the sensitivity of HWE tests to missingness. Unresolved missingness could lead to a false rejection of causality in an MR investigation of trait-disease association. These results indicate that large-scale studies, very high quality genotyping data, and detailed knowledge of the life-course genetics of the alleles/genotypes studied will largely mitigate this risk. The authors also present a Web program (http://www.oege.org/software/hwe-mr-calc.shtml) for estimating possible missingness and an approach to evaluating missingness under different genetic models. PMID:19126586

  18. Primary thermometry triad at 6 mK in mesoscopic circuits

    PubMed Central

    Iftikhar, Z.; Anthore, A.; Jezouin, S.; Parmentier, F. D.; Jin, Y.; Cavanna, A.; Ouerghi, A.; Gennser, U.; Pierre, F.

    2016-01-01

    Quantum physics emerge and develop as temperature is reduced. Although mesoscopic electrical circuits constitute an outstanding platform to explore quantum behaviour, the challenge in cooling the electrons impedes their potential. The strong coupling of such micrometre-scale devices with the measurement lines, combined with the weak coupling to the substrate, makes them extremely difficult to thermalize below 10 mK and imposes in situ thermometers. Here we demonstrate electronic quantum transport at 6 mK in micrometre-scale mesoscopic circuits. The thermometry methods are established by the comparison of three in situ primary thermometers, each involving a different underlying physics. The employed combination of quantum shot noise, quantum back action of a resistive circuit and conductance oscillations of a single-electron transistor covers a remarkably broad spectrum of mesoscopic phenomena. The experiment, performed in vacuum using a standard cryogen-free dilution refrigerator, paves the way towards the sub-millikelvin range with additional thermalization and refrigeration techniques. PMID:27659941

  19. Confined Mesoscopic Fluid-like Films Analyzed with Frequency Modulation and Acoustic Detection

    NASA Astrophysics Data System (ADS)

    Fernandez Rodriguez, Rodolfo

    Complete understanding of the physics underlying the changes in viscoelasticity, relaxation time, and phase transitions that mesoscopic fluid-like systems undergo at solid-liquid interfaces or under confinement remains one of the major challenges in condensed matter physics. Moreover, studies of confined mesoscopic fluid films are relevant to technological areas like adhesion, wetting processes and nanotribology. This thesis addresses the interaction between two sliding solids interfaces separated by a nanometer sized gap, with emphasis on the role of the mesoscopic fluid film trapped between them. For this purpose we integrated two acoustic techniques, recently introduced by our group, into a sub-nanometer precision and thermal drift corrected scanning probe microscope (SPM): the shear-force/acoustic near-field Microscope (SANM) and the whispering gallery acoustic sensing (WGAS). The SANM monitors the sound waves originating in the probe-layer interaction while the motion of the probe is monitored by the WGAS. Additionally, we decouple the interaction forces by using frequency modulation and measure the local tunneling current to help establish the location of the substrate. Our results show a strong correlation between the elastic component of the probe's interaction and the SANM amplitude, as well as between the phase lag response of the fluid relative to the probe's excitation (represented by the SANM phase) and the onset of the probe-sample contact region. Frequency modulation SANM-WGAS brings a new acoustic sensing mechanism to the challenging characterization of fluid-like physical systems at the nanometer scale.

  20. Mesoscopic interactions and species coexistence in evolutionary game dynamics of cyclic competitions.

    PubMed

    Cheng, Hongyan; Yao, Nan; Huang, Zi-Gang; Park, Junpyo; Do, Younghae; Lai, Ying-Cheng

    2014-12-15

    Evolutionary dynamical models for cyclic competitions of three species (e.g., rock, paper, and scissors, or RPS) provide a paradigm, at the microscopic level of individual interactions, to address many issues in coexistence and biodiversity. Real ecosystems often involve competitions among more than three species. By extending the RPS game model to five (rock-paper-scissors-lizard-Spock, or RPSLS) mobile species, we uncover a fundamental type of mesoscopic interactions among subgroups of species. In particular, competitions at the microscopic level lead to the emergence of various local groups in different regions of the space, each involving three species. It is the interactions among the groups that fundamentally determine how many species can coexist. In fact, as the mobility is increased from zero, two transitions can occur: one from a five- to a three-species coexistence state and another from the latter to a uniform, single-species state. We develop a mean-field theory to show that, in order to understand the first transition, group interactions at the mesoscopic scale must be taken into account. Our findings suggest, more broadly, the importance of mesoscopic interactions in coexistence of great many species.

  1. Mesoscopic Framework Enables Facile Ionic Transport in Solid Electrolytes for Li Batteries

    DOE PAGES

    Ma, Cheng; Cheng, Yongqiang; Chen, Kai; Li, Juchuan; Sumpter, Bobby G.; Nan, Ce-Wen; More, Karren L.; Dudney, Nancy J.; Chi, Miaofang

    2016-03-29

    In Li-ion-conducting solid electrolytes can simultaneously overcome two grand challenges for Li-ion batteries: the severe safety concerns that limit the large-scale application and the poor electrolyte stability that forbids the use of high-voltage cathodes. Nevertheless, the ionic conductivity of solid electrolytes is typically low, compromising the battery performances. Precisely determining the ionic transport mechanism(s) is a prerequisite for the rational design of highly conductive solid electrolytes. For decades, the research on this subject has primarily focused on the atomic and microscopic scales, where the main features of interest are unit cells and microstructures, respectively. We show that the largely overlookedmore » mesoscopic scale lying between these extremes could be the key to fast ionic conduction. In a prototype system, (Li0.33La0.56)TiO3, a mesoscopic framework is revealed for the first time by state-of-the-art scanning transmission electron microscopy. Corroborated by theoretical calculations and impedance measurements, it is demonstrated that such a unique configuration maximizes the number of percolation directions and thus most effectively improves the ionic conductivity. Finally, this discovery reconciles the long-standing structure–property inconsistency in (Li0.33La0.56)TiO3 and also identifies mesoscopic ordering as a promising general strategy for optimizing Li+ conduction.« less

  2. Analytical methods to determine the effective mesoscopic and macroscopic elastic properties of cortical bone.

    PubMed

    Parnell, William J; Vu, M B; Grimal, Q; Naili, S

    2012-07-01

    We compare theoretical predictions of the effective elastic moduli of cortical bone at both the meso- and macroscales. We consider the efficacy of three alternative approaches: the method of asymptotic homogenization, the Mori-Tanaka scheme and the Hashin-Rosen bounds. The methods concur for specific engineering moduli such as the axial Young's modulus but can vary for others. In a past study, the effect of porosity alone on mesoscopic properties of cortical bone was considered, taking the matrix to be isotropic. Here, we consider the additional influence of the transverse isotropy of the matrix. We make the point that micromechanical approaches can be used in two alternative ways to predict either the macroscopic (size of cortical bone sample) or mesoscopic (in between micro- and macroscales) effective moduli, depending upon the choice of representative volume element size. It is widely accepted that the mesoscale behaviour is an important aspect of the mechanical behaviour of bone but models incorporating its effect have started to appear only relatively recently. Before this only macroscopic behaviour was addressed. Comparisons are drawn with experimental data and simulations from the literature for macroscale predictions with particularly good agreement in the case of dry bone. Finally, we show how predictions of the effective mesoscopic elastic moduli can be made which retain dependence on the well-known porosity gradient across the thickness of cortical bone.

  3. Analytical methods to determine the effective mesoscopic and macroscopic elastic properties of cortical bone.

    PubMed

    Parnell, William J; Vu, M B; Grimal, Q; Naili, S

    2012-07-01

    We compare theoretical predictions of the effective elastic moduli of cortical bone at both the meso- and macroscales. We consider the efficacy of three alternative approaches: the method of asymptotic homogenization, the Mori-Tanaka scheme and the Hashin-Rosen bounds. The methods concur for specific engineering moduli such as the axial Young's modulus but can vary for others. In a past study, the effect of porosity alone on mesoscopic properties of cortical bone was considered, taking the matrix to be isotropic. Here, we consider the additional influence of the transverse isotropy of the matrix. We make the point that micromechanical approaches can be used in two alternative ways to predict either the macroscopic (size of cortical bone sample) or mesoscopic (in between micro- and macroscales) effective moduli, depending upon the choice of representative volume element size. It is widely accepted that the mesoscale behaviour is an important aspect of the mechanical behaviour of bone but models incorporating its effect have started to appear only relatively recently. Before this only macroscopic behaviour was addressed. Comparisons are drawn with experimental data and simulations from the literature for macroscale predictions with particularly good agreement in the case of dry bone. Finally, we show how predictions of the effective mesoscopic elastic moduli can be made which retain dependence on the well-known porosity gradient across the thickness of cortical bone. PMID:22109098

  4. Combining molecular dynamics with mesoscopic Green’s function reaction dynamics simulations

    SciTech Connect

    Vijaykumar, Adithya; Bolhuis, Peter G.; Rein ten Wolde, Pieter

    2015-12-07

    In many reaction-diffusion processes, ranging from biochemical networks, catalysis, to complex self-assembly, the spatial distribution of the reactants and the stochastic character of their interactions are crucial for the macroscopic behavior. The recently developed mesoscopic Green’s Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. We propose a novel approach that combines GFRD for simulating the system at the mesoscopic scale where particles are far apart, with a microscopic technique such as Langevin dynamics or Molecular Dynamics (MD), for simulating the system at the microscopic scale where reactants are in close proximity. This scheme defines the regions where the particles are close together and simulated with high microscopic resolution and those where they are far apart and simulated with lower mesoscopic resolution, adaptively on the fly. The new multi-scale scheme, called MD-GFRD, is generic and can be used to efficiently simulate reaction-diffusion systems at the particle level.

  5. Non-equilibrium phase transition in mesoscopic biochemical systems: from stochastic to nonlinear dynamics and beyond.

    PubMed

    Ge, Hao; Qian, Hong

    2011-01-01

    A theory for an non-equilibrium phase transition in a driven biochemical network is presented. The theory is based on the chemical master equation (CME) formulation of mesoscopic biochemical reactions and the mathematical method of large deviations. The large deviations theory provides an analytical tool connecting the macroscopic multi-stability of an open chemical system with the multi-scale dynamics of its mesoscopic counterpart. It shows a corresponding non-equilibrium phase transition among multiple stochastic attractors. As an example, in the canonical phosphorylation-dephosphorylation system with feedback that exhibits bistability, we show that the non-equilibrium steady-state (NESS) phase transition has all the characteristics of classic equilibrium phase transition: Maxwell construction, a discontinuous first-derivative of the 'free energy function', Lee-Yang's zero for a generating function and a critical point that matches the cusp in nonlinear bifurcation theory. To the biochemical system, the mathematical analysis suggests three distinct timescales and needed levels of description. They are (i) molecular signalling, (ii) biochemical network nonlinear dynamics, and (iii) cellular evolution. For finite mesoscopic systems such as a cell, motions associated with (i) and (iii) are stochastic while that with (ii) is deterministic. Both (ii) and (iii) are emergent properties of a dynamic biochemical network.

  6. Non-equilibrium phase transition in mesoscopic biochemical systems: from stochastic to nonlinear dynamics and beyond

    PubMed Central

    Ge, Hao; Qian, Hong

    2011-01-01

    A theory for an non-equilibrium phase transition in a driven biochemical network is presented. The theory is based on the chemical master equation (CME) formulation of mesoscopic biochemical reactions and the mathematical method of large deviations. The large deviations theory provides an analytical tool connecting the macroscopic multi-stability of an open chemical system with the multi-scale dynamics of its mesoscopic counterpart. It shows a corresponding non-equilibrium phase transition among multiple stochastic attractors. As an example, in the canonical phosphorylation–dephosphorylation system with feedback that exhibits bistability, we show that the non-equilibrium steady-state (NESS) phase transition has all the characteristics of classic equilibrium phase transition: Maxwell construction, a discontinuous first-derivative of the ‘free energy function’, Lee–Yang's zero for a generating function and a critical point that matches the cusp in nonlinear bifurcation theory. To the biochemical system, the mathematical analysis suggests three distinct timescales and needed levels of description. They are (i) molecular signalling, (ii) biochemical network nonlinear dynamics, and (iii) cellular evolution. For finite mesoscopic systems such as a cell, motions associated with (i) and (iii) are stochastic while that with (ii) is deterministic. Both (ii) and (iii) are emergent properties of a dynamic biochemical network. PMID:20466813

  7. Lattices of ultracold atom traps over arrays of nano- and mesoscopic superconducting disks

    NASA Astrophysics Data System (ADS)

    Sokolovsky, Vladimir; Prigozhin, Leonid

    2016-04-01

    A lattice of traps for ultracold neutral atoms is a promising tool for experimental investigation in quantum physics and quantum information processing. We consider regular arrays of thin film type-II superconducting nanodisks, with only one pinned vortex in each of them, and also arrays of mesoscopic disks, each containing many vortices whose distribution is characterized by the superconducting current density. In both cases we show theoretically that the induced magnetic field can create a 3D lattice of magnetic traps for cold atoms without any additional bias field. Applying a bias DC field parallel to the superconductor surface, one can control the depth and sizes of the traps, their heights above the chip surface, potential barriers between the traps, as well as the structure and dimension of the lattices. In the adiabatic approximation the atom cloud shape is represented by the shape of a closed iso-surface of the magnetic field magnitude chosen in accordance with the atom cloud temperature. The computed trap sizes, heights and the distances between the neighboring traps are typically from tens to hundreds nanometers for nanodisks and of the order of 1 μm for mesoscopic disks. Our calculations show that the depth of magnetic traps on mesoscopic disks is, typically, between 0.3 G and 7.6 G; for the nanodisks the depth is about 0.3 G.

  8. Mesoscopic Interactions and Species Coexistence in Evolutionary Game Dynamics of Cyclic Competitions

    NASA Astrophysics Data System (ADS)

    Cheng, Hongyan; Yao, Nan; Huang, Zi-Gang; Park, Junpyo; Do, Younghae; Lai, Ying-Cheng

    2014-12-01

    Evolutionary dynamical models for cyclic competitions of three species (e.g., rock, paper, and scissors, or RPS) provide a paradigm, at the microscopic level of individual interactions, to address many issues in coexistence and biodiversity. Real ecosystems often involve competitions among more than three species. By extending the RPS game model to five (rock-paper-scissors-lizard-Spock, or RPSLS) mobile species, we uncover a fundamental type of mesoscopic interactions among subgroups of species. In particular, competitions at the microscopic level lead to the emergence of various local groups in different regions of the space, each involving three species. It is the interactions among the groups that fundamentally determine how many species can coexist. In fact, as the mobility is increased from zero, two transitions can occur: one from a five- to a three-species coexistence state and another from the latter to a uniform, single-species state. We develop a mean-field theory to show that, in order to understand the first transition, group interactions at the mesoscopic scale must be taken into account. Our findings suggest, more broadly, the importance of mesoscopic interactions in coexistence of great many species.

  9. Mesoscopic Interactions and Species Coexistence in Evolutionary Game Dynamics of Cyclic Competitions

    PubMed Central

    Cheng, Hongyan; Yao, Nan; Huang, Zi-Gang; Park, Junpyo; Do, Younghae; Lai, Ying-Cheng

    2014-01-01

    Evolutionary dynamical models for cyclic competitions of three species (e.g., rock, paper, and scissors, or RPS) provide a paradigm, at the microscopic level of individual interactions, to address many issues in coexistence and biodiversity. Real ecosystems often involve competitions among more than three species. By extending the RPS game model to five (rock-paper-scissors-lizard-Spock, or RPSLS) mobile species, we uncover a fundamental type of mesoscopic interactions among subgroups of species. In particular, competitions at the microscopic level lead to the emergence of various local groups in different regions of the space, each involving three species. It is the interactions among the groups that fundamentally determine how many species can coexist. In fact, as the mobility is increased from zero, two transitions can occur: one from a five- to a three-species coexistence state and another from the latter to a uniform, single-species state. We develop a mean-field theory to show that, in order to understand the first transition, group interactions at the mesoscopic scale must be taken into account. Our findings suggest, more broadly, the importance of mesoscopic interactions in coexistence of great many species. PMID:25501627

  10. Host range testing and biology of Abia sericea (Cimbicidae), a candidate for biological control of invasive teasels (Dipsacus spp.) in North America

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Invasive teasels (Dipsacus spp., Dipsacaceae) are widespread in the USA, being present in 43 states and listed as noxious in five. The cimbicid sawfly Abia sericea (L.) is under evaluation as a potential agent for biological control of teasels. The host range, biology, and life history of this ins...

  11. Testing the effectiveness of problem-based learning with learning-disabled students in biology

    NASA Astrophysics Data System (ADS)

    Guerrera, Claudia Patrizia

    The purpose of the present study was to investigate the effects of problem-based learning (PBL) with learning-disabled (LD) students. Twenty-four students (12 dyads) classified as LD and attending a school for the learning-disabled participated in the study. Students engaged in either a computer-based environment involving BioWorld, a hospital simulation designed to teach biology students problem-solving skills, or a paper-and-pencil version based on the computer program. A hybrid model of learning was adopted whereby students were provided with direct instruction on the digestive system prior to participating in a problem-solving activity. Students worked in dyads and solved three problems involving the digestive system in either a computerized or a paper-and-pencil condition. The experimenter acted as a coach to assist students throughout the problem-solving process. A follow-up study was conducted, one month later, to measure the long-term learning gains. Quantitative and qualitative methods were used to analyze three types of data: process data, outcome data, and follow-up data. Results from the process data showed that all students engaged in effective collaboration and became more systematic in their problem solving over time. Findings from the outcome and follow-up data showed that students in both treatment conditions, made both learning and motivational gains and that these benefits were still evident one month later. Overall, results demonstrated that the computer facilitated students' problem solving and scientific reasoning skills. Some differences were noted in students' collaboration and the amount of assistance required from the coach in both conditions. Thus, PBL is an effective learning approach with LD students in science, regardless of the type of learning environment. These results have implications for teaching science to LD students, as well as for future designs of educational software for this population.

  12. Trait-Based Representation of Biological Nitrification: Model Development, Testing, and Predicted Community Composition

    PubMed Central

    Bouskill, Nicholas J.; Tang, Jinyun; Riley, William J.; Brodie, Eoin L.

    2012-01-01

    Trait-based microbial models show clear promise as tools to represent the diversity and activity of microorganisms across ecosystem gradients. These models parameterize specific traits that determine the relative fitness of an “organism” in a given environment, and represent the complexity of biological systems across temporal and spatial scales. In this study we introduce a microbial community trait-based modeling framework (MicroTrait) focused on nitrification (MicroTrait-N) that represents the ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) using traits related to enzyme kinetics and physiological properties. We used this model to predict nitrifier diversity, ammonia (NH3) oxidation rates, and nitrous oxide (N2O) production across pH, temperature, and substrate gradients. Predicted nitrifier diversity was predominantly determined by temperature and substrate availability, the latter was strongly influenced by pH. The model predicted that transient N2O production rates are maximized by a decoupling of the AOB and NOB communities, resulting in an accumulation and detoxification of nitrite to N2O by AOB. However, cumulative N2O production (over 6 month simulations) is maximized in a system where the relationship between AOB and NOB is maintained. When the reactions uncouple, the AOB become unstable and biomass declines rapidly, resulting in decreased NH3 oxidation and N2O production. We evaluated this model against site level chemical datasets from the interior of Alaska and accurately simulated NH3 oxidation rates and the relative ratio of AOA:AOB biomass. The predicted community structure and activity indicate (a) parameterization of a small number of traits may be sufficient to broadly characterize nitrifying community structure and (b) changing decadal trends in climate and edaphic conditions could impact nitrification rates in ways that are not captured by extant biogeochemical models. PMID

  13. From particle to powder properties - A mesoscopic approach combining micro-scale experiments and X-ray microtomography

    NASA Astrophysics Data System (ADS)

    Strege, S.; Zetzener, H.; Kwade, A.

    2013-06-01

    The detailed understanding of particle flow is of special interest from the academic point of view and crucial for a safe and reliable process design. Due to poor flowability and heterogeneous bulk structures, the handling of fine and cohesive powders is particularly challenging. Recently, high resolution X-ray microtomography (XMT) has proved to be a reliable tool for analysing powder structures on bulk and particle level. This study now presents a complementary approach of micro-scale experiments and XMT analysis to improve the general understanding of particle flow. Centrepiece of the experimental investigation is a novel micro shear tester (μST) for very small powder samples (volumes from 0.005 to 0.1 mL), which has been integrated into a high resolution XMT system. By combining μST and XMT it is possible to extract detailed 3D images of precisely compacted and sheared powder samples. A SiO2 powder consisting of spherical, adhesive particles (x50,3 ≈ 11,2 μm) and a limestone powder consisting of irregular shaped particles (x50,3 ≈ 4,8 μm) are scanned before and after various shear and compaction tests. A detailed analysis of the sample microstructure reveals important information on the particle network and the bulk structure. The impact of the test procedure on mesoscopic heterogeneities and shear zones inside the sample is discussed. Moreover, the measurement of yield loci in the novel μST is presented.

  14. Biological induced corrosion of materials II: New test methods and experiences from mir station

    NASA Astrophysics Data System (ADS)

    Klintworth, R.; Reher, H. J.; Viktorov, A. N.; Bohle, D.

    1999-09-01

    During previous long-term manned missions, more than 100 species of microorganisms have been identified on surfaces of materials (bacteria and fungi). Among them were potentially pathogenic ones (saprophytes) which are capable of active growth on artificial substrates, as well as technophilic bacteria and fungi causing damages (destruction and degradation) to various materials (metals and polymers), resulting in failures and disruptions in the functioning of equipment and hardware. Aboard a space vehicle some microclimatic parameters are optimal for microorganism growth: the atmospheric fluid condensate with its specific composition, chemical and/or antropogenic contaminants (human metobolic products, etc.) all are stimulating factors for the development of bacteria and mould fungi on materials of the interior and equipment of an orbital station during its operational phase(s). Especially Russian long-term missions (SALJUT, MIR) have demonstrated that uncontrolled interactions of microorganisms with materials will ultimately lead to the appearence of technological and medical risks, significantly influencing safety and reliability characteristics of individual as well as whole systems and/ or subsystems. For a first conclusion, it could be summarized, that countermeasures and anti-strategies focussing on Microbial Contamination Management (MCM) for the International Space Station (ISS, next long-term manned mission) at least require a new materials test approach. Our respective concept includes a combined age-ing/biocorrosion test sequence. It is represented here, as well as current status of MCM program, e.g. continuous monitoring (microbiological analyses), long-term disinfection, frequent cleaning methods, mathematical modeling of ISS, etc.

  15. Photodegradation of fluorene in aqueous solution: Identification and biological activity testing of degradation products.

    PubMed

    Kinani, Said; Souissi, Yasmine; Kinani, Aziz; Vujović, Svetlana; Aït-Aïssa, Sélim; Bouchonnet, Stéphane

    2016-04-15

    Degradation of fluorene under UV-vis irradiation in water was investigated and structural elucidation of the main photoproducts was achieved using gas chromatography coupled with mass spectrometry. Twenty-six photoproducts were structurally identified, mainly on the basis of electron ionization mass spectra interpretation. The main generated transformation products are hydroxy derivatives. Some secondary photoproducts including fluorenone, hydroxy fluorenone, 2-biphenyl carboxylic acid, biphenylene, methanol fluorene congeners and hydroxy fluorene dimers were also observed. A photodegradation pathway was suggested on the basis of the chemical structures of photoproducts. Fluorene as well as its main photoproducts for which chemical standards were commercially available were tested for their ability to elicit cytotoxic, estrogenic and dioxin-like activity by using in vitro cell-based bioassays. None of the tested compounds was cytotoxic at concentrations up to 100 μM. However, 2-hydroxyfluorene and 3-hydroxyfluorene exerted significant estrogenic and dioxin-like activity on a concentration range of 3-30 μM, while fluorene and 9-hydroxyfluorene were weakly or not active, respectively, in our assays. This supports the view that photodegradation processes can generate by-products of higher toxicological concern than the parent compound and strengthens the need to further identify transformation products in the aquatic environment.

  16. Relationships among sediment chemistry, toxicity testing, and biology: What can large-scale monitoring teach us?

    SciTech Connect

    Summers, J.K.; Macauley, J.M.; Engle, V.D.; Malaeb, Z.

    1995-12-31

    The Environmental Monitoring and Assessment Program for Estuarine Resources has collected sediments from over 1,000 varying locations in the estuaries of the United States. At each of these sites, sediments are analyzed for bulk chemistry, tested for toxicity to Ampelisca abdita, and enumerated regarding benthic community structure and abundance. In addition, tissue residues have been examined for selected fish and shellfish species and toxicity testing has been completed at selected sites for alternative species. The statistical and ecological relationships among these indicators have been examined with regard to how they can used to identify the overall ecological condition of a site, an estuary, or populations of estuaries. Comparisons of these relationships among different regions of the country show major differences in the modes of exposure and response being prevalent in the Southeast and Gulf Coasts as compared to the Mid-Atlantic and West Coasts. While the extent of sediment contamination in the Southeast and Gulf estuaries appears to be similar to that of the Mid-Atlantic and California Coasts, the degree of contamination at contaminated sites is much greater in Mid-Atlantic estuaries. An examination of the primary contaminants suggests that the primary sources of contamination in the Mid-Atlantic are industrial and urban while the Southeast and Gulf estuaries are dominated by agricultural contaminants.

  17. Herpes Murine Model as a Biological Assay to Test Dialyzable Leukocyte Extracts Activity

    PubMed Central

    Salinas-Jazmín, Nohemí; Estrada-Parra, Sergio; Becerril-García, Miguel Angel; Limón-Flores, Alberto Yairh; Vázquez-Leyva, Said; Pavón, Lenin; Velasco-Velázquez, Marco Antonio; Pérez-Tapia, Sonia Mayra

    2015-01-01

    Human dialyzable leukocyte extracts (DLEs) are heterogeneous mixtures of low-molecular-weight peptides that are released on disruption of peripheral blood leukocytes from healthy donors. DLEs improve clinical responses in infections, allergies, cancer, and immunodeficiencies. Transferon is a human DLE that has been registered as a hemoderivate by Mexican health authorities and commercialized nationally. To develop an animal model that could be used routinely as a quality control assay for Transferon, we standardized and validated a murine model of cutaneous HSV-1 infection. Using this model, we evaluated the activity of 27 Transferon batches. All batches improved the survival of HSV-1-infected mice, wherein average survival rose from 20.9% in control mice to 59.6% in Transferon-treated mice. The activity of Transferon correlated with increased serum levels of IFN-γ and reduced IL-6 and TNF-α concentrations. Our results demonstrate that (i) this mouse model of cutaneous herpes can be used to examine the activity of DLEs, such as Transferon; (ii) the assay can be used as a routine test for batch release; (iii) Transferon is produced with high homogeneity between batches; (iv) Transferon does not have direct virucidal, cytoprotective, or antireplicative effects; and (v) the protective effect of Transferon in vivo correlates with changes in serum cytokines. PMID:25984538

  18. Herpes murine model as a biological assay to test dialyzable leukocyte extracts activity.

    PubMed

    Salinas-Jazmín, Nohemí; Estrada-Parra, Sergio; Becerril-García, Miguel Angel; Limón-Flores, Alberto Yairh; Vázquez-Leyva, Said; Medina-Rivero, Emilio; Pavón, Lenin; Velasco-Velázquez, Marco Antonio; Pérez-Tapia, Sonia Mayra

    2015-01-01

    Human dialyzable leukocyte extracts (DLEs) are heterogeneous mixtures of low-molecular-weight peptides that are released on disruption of peripheral blood leukocytes from healthy donors. DLEs improve clinical responses in infections, allergies, cancer, and immunodeficiencies. Transferon is a human DLE that has been registered as a hemoderivate by Mexican health authorities and commercialized nationally. To develop an animal model that could be used routinely as a quality control assay for Transferon, we standardized and validated a murine model of cutaneous HSV-1 infection. Using this model, we evaluated the activity of 27 Transferon batches. All batches improved the survival of HSV-1-infected mice, wherein average survival rose from 20.9% in control mice to 59.6% in Transferon-treated mice. The activity of Transferon correlated with increased serum levels of IFN-γ and reduced IL-6 and TNF-α concentrations. Our results demonstrate that (i) this mouse model of cutaneous herpes can be used to examine the activity of DLEs, such as Transferon; (ii) the assay can be used as a routine test for batch release; (iii) Transferon is produced with high homogeneity between batches; (iv) Transferon does not have direct virucidal, cytoprotective, or antireplicative effects; and (v) the protective effect of Transferon in vivo correlates with changes in serum cytokines.

  19. Field scale testing of a hyperfiltration unit for removal of creosote and pentachlorophenol from ground water: Chemical and biological assessment

    SciTech Connect

    Middaugh, D.P.; Thomas, R.L.; Lantz, S.E.; Heard, C.S.; Mueller, J.G.

    1994-01-01

    Chemical analyses and biological response data were used to assess the efficacy of a field-scale hyperfiltration unit in the removal of polycyclic aromatic hydrocarbons (PAHs) and other organic compounds from creosote- and pentachlorophenol (PCP)-contaminated ground water recovered from the former American Creosote Works in Escambia County, Pensacola, Florida. The hyperfiltration unit consisted of 4 modules containing porous stainless steel tubes which were coated with a formed-in-place zirconium hydrous oxide-polyacrylic acid (ZOPA) membrane. A 5-fold concentration of the feedwater (80% volume reduction) with up to 97% removal of high molecular weight PAHs was achieved during pre-demonstration and field-demonstration runs of the hyperfiltration unit. Toxicological and teratogenic data for embryonic inland silversides, Menidia beryllina, indicated that 100, 10 and 1% solutions of the ground water sample used in the pre-demonstration run caused statistically significant (p < or - 0.05) biological responses when compared to controls. Permeates from both runs, diluted to 1%, met the pre-condition of non-toxic responses in 48h tests with Ceriodaphnia dubia. Meeting this requirement allowed for discharge of diluted permeate into the county's sanitary sewerage collector system.

  20. Environmental Technology Verification: Supplement to Test/QA Plan for Biological and Aerosol Testing of General Ventilation Air Cleaners; Bioaerosol Inactivation Efficiency by HVAC In-Duct Ultraviolet Light Air Cleaners

    EPA Science Inventory

    The Air Pollution Control Technology Verification Center has selected general ventilation air cleaners as a technology area. The Generic Verification Protocol for Biological and Aerosol Testing of General Ventilation Air Cleaners is on the Environmental Technology Verification we...

  1. Biologic overview for the Nevada Nuclear Waste Storage Investigations, Nevada Test Site, Nye County, Nevada

    SciTech Connect

    Collins, E.; O`Farrell, T.P.; Rhoads, W.A.

    1982-01-01

    The Nevada Nuclear Waste Storage Investigations project study area includes five major vegetation associations characteristic of the transition between the northern extent of the Mojave Desert and the southern extent of the Great Basin Desert. A total of 32 species of reptiles, 66 species of birds, and 46 species of mammals are known to occur within these associations elsewhere on the Nevada Test Site. Ten species of plants, and the mule deer, wild horse, feral burro, and desert tortoise were defined as possible sensitive species because they are protected by federal and state regulations, or are being considered for such protection. The major agricultural resources of southern Nye County included 737,000 acres of public grazing land managed by the Bureau of Land Management, and 9500 acres of irrigated crop land located in the Beatty/Oasis valleys, the Amargosa Valley, and Ash Meadows. Range lands are of poor quality. Alfalfa and cotton are the major crops along with small amounts of grains, Sudan grass, turf, fruits, and melons. The largest impacts to known ecosystems are expected to result from: extensive disturbances associated with construction of roads, seismic lines, drilling pads, and surface facilities; storage and leaching of mined spoils; disposal of water; off-road vehicle travel; and, over several hundred years, elevated soil temperatures. Significant impacts to off-site areas such as Ash Meadows are anticipated if new residential developments are built there to accommodate an increased work force. Several species of concern and their essential habitats are located at Ash Meadows. Available literature contained sufficient baseline information to assess potential impacts of the proposed project on an area-wide basis. It was inadequate to support analysis of potential impacts on specific locations selected for site characterization studies, mining an exploratory shaft, or the siting and operation of a repository.

  2. Multifrequency acoustics as a probe of mesoscopic blood coagulation dynamics

    NASA Astrophysics Data System (ADS)

    Ganesan, Adarsh; Rajendran, Gokulnath; Ercole, Ari; Seshia, Ashwin

    2016-08-01

    Coagulation is a complex enzymatic polymerisation cascade. Disordered coagulation is common in medicine and may be life-threatening yet clinical assays are typically bulky and/or provide an incomplete picture of clot mechanical evolution. We present the adaptation of an in-plane acoustic wave device: quartz crystal microbalance with dissipation at multiple harmonics to determine the time-evolution of mesoscale mechanical properties of clot formation in vitro. This approach is sensitive to changes in surface and bulk clot structure in various models of induced coagulopathy. Furthermore, we are able to show that clot formation at surfaces has different kinetics and mechanical strength to that in the bulk, which may have implications for the design of bioprosthetic materials. The "Multifrequency acoustics" approach thus enables unique capability to portray biological processes concerning blood coagulation.

  3. A mathematical model for the interpretation of nuclear bomb test derived 14C incorporation in biological systems

    NASA Astrophysics Data System (ADS)

    Bernard, Samuel; Frisén, Jonas; Spalding, Kirsty L.

    2010-04-01

    Human tissues continually replace dying cells with newborn cells. However, the rate of renewal varies by orders of magnitudes between blood cells, which are renewed every day and neurons, for which renewal is non-existent or limited to specific regions of the brain. Between those extreme are many tissues that turnover on a time scale of years, although no direct measurements have been done. We present here a mathematical method to estimate cell turnover in slowly renewing biological systems. Age distribution of DNA can be estimated from the integration of radiocarbon derived from nuclear bomb-testing during the cold war (1955-1963). For slowly renewing tissues, this method provides a better estimate of the average age of the tissue than direct estimates from the bomb-curve. Moreover, death, birth and turnover rates can be estimated. We highlight this method with data from human fat cells.

  4. DNA Fingerprinting To Improve Data Collection Efficiency and Yield in a Host-Specificity Test of a Weed Biological Control Candidate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An open-field test was conducted in southern France to assess the host-specificity of Ceratapion basicorne, a candidate for biological control of yellow starthistle (Centaurea solstitialis; YST). Test plants were infested by naturally occurring populations of C. basicorne but were also exposed to s...

  5. Biology Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1983

    1983-01-01

    Describes laboratory procedures, demonstrations, and classroom activities/materials, including chi-square tests on a microcomputer, an integrated biology game, microscope slides of leaf stomata, culturing soil nematodes, technique for watering locust egg-laying tubes, hazards of biological chemicals (such as benzene, benzidene, calchicine,…

  6. Critical behavior of a two-dimensional complex fluid: Macroscopic and mesoscopic views

    NASA Astrophysics Data System (ADS)

    Choudhuri, Madhumita; Datta, Alokmay

    2016-04-01

    Liquid disordered (Ld) to liquid ordered (Lo) phase transition in myristic acid [MyA, CH3(CH2) 12COOH ] Langmuir monolayers was studied macroscopically as well as mesoscopically to locate the critical point. Macroscopically, isotherms of the monolayer were obtained across the 20 ∘C-38 ∘Ctemperature (T ) range and the critical point was estimated, primarily from the vanishing of the order parameter, at ≈38 ∘C. Mesoscopically, domain morphology in the Ld-Lo coexistence regime was imaged using the technique of Brewster angle microscopy (BAM) as a function of T and the corresponding power spectral density function (PSDF) obtained. Monolayer morphology passed from stable circular domains and a sharp peak in PSDF to stable dendritic domains and a divergence of the correlation length as the critical point was approached from below. The critical point was found to be consistent at ≈38 ∘Cfrom both isotherm and BAM results. In the critical regime the scaling behavior of the transition followed the two-dimensional Ising model. Additionally, we obtained a precritical regime, over a temperature range of ≈8 ∘C below Tc, characterized by fluctuations in the order parameter at the macroscopic scale and at the mesoscopic scale characterized by unstable domains of fingering or dendritic morphology as well as proliferation of a large number of small sized domains, multiple peaks in the power spectra, and a corresponding fluctuation in the peak q values with T . Further, while comparing temperature studies on an ensemble of MyA monolayers with those on a single monolayer, the system was found to be not strictly ergodic in that the ensemble development did not strictly match with the time development in the system. In particular, the critical temperature was found to be lowered in the latter. These results clearly show that the critical behavior in fatty acid monolayer phase transitions have features of both complex and nonequilibrium systems.

  7. Convergence of methods for coupling of microscopic and mesoscopic reaction-diffusion simulations

    PubMed Central

    Flegga, Mark B.; Hellander, Stefan; Erban, Radek

    2015-01-01

    In this paper, three multiscale methods for coupling of mesoscopic (compartment-based) and microscopic (molecular-based) stochastic reaction-diffusion simulations are investigated. Two of the three methods that will be discussed in detail have been previously reported in the literature; the two-regime method (TRM) and the compartment-placement method (CPM). The third method that is introduced and analysed in this paper is called the ghost cell method (GCM), since it works by constructing a “ghost cell” in which molecules can disappear and jump into the compartment-based simulation. Presented is a comparison of sources of error. The convergent properties of this error are studied as the time step Δt (for updating the molecular-based part of the model) approaches zero. It is found that the error behaviour depends on another fundamental computational parameter h, the compartment size in the mesoscopic part of the model. Two important limiting cases, which appear in applications, are considered: (i) Δt → 0 and h is fixed; (ii) Δt → 0 and h → 0 such that √Δt/h is fixed. The error for previously developed approaches (the TRM and CPM) converges to zero only in the limiting case (ii), but not in case (i). It is shown that the error of the GCM converges in the limiting case (i). Thus the GCM is superior to previous coupling techniques if the mesoscopic description is much coarser than the microscopic part of the model. PMID:26568640

  8. Bottle Biology.

    ERIC Educational Resources Information Center

    CSTA Journal, 1995

    1995-01-01

    Provides hands-on biology activities using plastic bottles that allow students to become engaged in asking questions, creating experiments, testing hypotheses, and generating answers. Activities explore terrestrial and aquatic systems. (MKR)

  9. Thermal Design, Test and Analysis of PharmaSat, a Small Class D Spacecraft with a Biological Experiment

    NASA Technical Reports Server (NTRS)

    Diaz-Aguado, Millan F.; VanOutryve, Cassandra; Ghassemiah, Shakib; Beasley, Christopher; Schooley, Aaron

    2009-01-01

    Small spacecraft have been increasing in popularity because of their low cost, short turnaround and relative efficiency. In the past, small spacecraft have been primarily used for technology demonstrations, but advances in technology have made the miniaturization of space science possible [1,2]. PharmaSat is a low cost, small three cube size spacecraft, with a biological experiment on board, built at NASA (National Aeronautics and Space Administration) Ames Research Center. The thermal design of small spacecraft presents challenges as their smaller surface areas translate into power and thermal constraints. The spacecraft is thermally designed to run colder in the Low Earth Orbit space environment, and heated to reach the temperatures required by the science payload. The limited power supply obtained from the solar panels on small surfaces creates a constraint in the power used to heat the payload to required temperatures. The pressurized payload is isolated with low thermally conductance paths from the large ambient temperature changes. The thermal design consists of different optical properties of section surfaces, Multi Layer Insulation (MLI), low thermal conductance materials, flexible heaters and thermal spreaders. The payload temperature is controlled with temperature sensors and flexible heaters. Finite Element Analysis (FEA) and testing were used to aid the thermal design of the spacecraft. Various tests were conducted to verify the thermal design. An infrared imager was used on the electronic boards to find large heat sources and eliminate any possible temperature runaways. The spacecraft was tested in a thermal vacuum chamber to optimize the thermal and power analysis and qualify the thermal design of the spacecraft for the mission.

  10. Long-range thermoelectric effects in mesoscopic superconductor-normal metal structures

    NASA Astrophysics Data System (ADS)

    Volkov, A. F.; Pavlovskii, V. V.

    2005-07-01

    We consider a mesoscopic four-terminal superconductor-normal metal structure in the presence of a temperature gradient along the N wire. A thermoemf arises in this system even in the absence of the thermoelectric quasiparticle current if the phase difference between the superconductors is not zero. We show that the thermoemf is not small in the case of a negligible Josephson coupling between two superconductors. It is also shown that the thermoelectric voltage has two maxima: one at a low temperature and another at a temperature close to the critical temperature. The obtained temperature dependence of the thermoemf describes qualitatively experimental data.

  11. Structure and rheology of star polymers in confined geometries: a mesoscopic simulation study.

    PubMed

    Zheng, Feiwo; Goujon, Florent; Mendonça, Ana C F; Malfreyt, Patrice; Tildesley, Dominic J

    2015-11-28

    Mesoscopic simulations of star polymer melts adsorbed onto solid surfaces are performed using the dissipative particle dynamics (DPD) method. A set of parameters is developed to study the low functionality star polymers under shear. The use of a new bond-angle potential between the arms of the star creates more rigid chains and discriminates between different functionalities at equilibrium, but still allows the polymers to deform appropriately under shear. The rheology of the polymer melts is studied by calculating the kinetic friction and viscosity and there is good agreement with experimental properties of these systems. The study is completed with predictive simulations of star polymer solutions in an athermal solvent. PMID:26435466

  12. Intensity correlations and mesoscopic fluctuations of diffusing photons in cold atoms.

    PubMed

    Assaf, O; Akkermans, E

    2007-02-23

    We study the angular correlation function of speckle patterns that result from multiple scattering of photons by cold atomic clouds. We show that this correlation function becomes larger than the value given by Rayleigh law for classical scatterers. These large intensity fluctuations constitute a new mesoscopic effect specific to atom-photon interactions, that could not be observed in other systems such as weakly disordered metals. We provide a complete description of this behavior and expressions that allow for a quantitative comparison with experiments.

  13. Charged, dipolar soft matter systems from a combined microscopic-mesoscopic viewpoint

    NASA Astrophysics Data System (ADS)

    Schröder, Christian; Steinhauser, Othmar

    2016-09-01

    As an example of charged, dipolar soft matter, the ionic liquid 1-ethyl-3-methyl-imidazolium dicyanamide is studied by coarse-grained molecular dynamics simulations. We focus on the link between microscopic and mesoscopic properties for both structure and dynamics. Thereby, the generalized Kirkwood g K-factor plays a central role in establishing this link which is not possible on the basis of molecular hydrodynamics. The decoupling between translational and rotational motion is indicative of the dynamical heterogeneity in ionic liquids.

  14. Mesoscopic Correlation of Supramolecular Chirality in One-Dimensional Hydrogen-Bonded Assemblies

    SciTech Connect

    Weckesser, J.; De Vita, A.; Barth, J. V.; Cai, C.; Kern, K.

    2001-08-27

    The ordering of 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid, a two-dimensional chiral species, was studied by scanning tunneling microscopy at noble metal surfaces. Homochiral molecules self-assemble in supramolecular chiral hydrogen-bonded twin chains, which order in nanogratings where the supramolecular chirality is strictly correlated over the entire {mu}m domains without intimate molecular contact. Model simulations indicate that the underlying mesoscopic chiral resolution is associated with twin chains acting as chiroselective templates for transient molecular attachment, which process mediates the gratings' evolution.

  15. Mesoscopic structural analysis of bedrock exposures at the Oak Ridge K-25 Site, Oak Ridge, Tennessee

    SciTech Connect

    Lemiszki, P.J.

    1995-07-01

    This document presents the detailed study of outcrop of mesoscopic structures during the geologic mapping completed in 1992-1993. The purpose of this study was to document the geometry and style of outcrop scale structures, such as fractures and faults and relate them to map scale structures present in the Oak Ridge K-25 Area. This report was prepared to document site characterization data collected during the scoping phase investigations in accordance with the requirements of the Comprehensive Environmental Response, Compensation, and Liability Act.

  16. On the dynamics of a time-dependent mesoscopic LC circuit with a negative inductance

    NASA Astrophysics Data System (ADS)

    Pedrosa, I. A.; Nogueira, E.; Guedes, I.

    2016-05-01

    We discuss the problem of a mesoscopic LC circuit with a negative inductance ruled by a time-dependent Hermitian Hamiltonian. Classically, we find unusual expressions for the Faraday’s law and for the inductance of a solenoid. Quantum mechanically, we solve exactly the time-dependent Schrödinger equation through the Lewis and Riesenfeld invariant operator method and construct Gaussian wave packet solutions for this time-dependent LC circuit. We also evaluate the expectation values of the charge and the magnetic flux in these Gaussian states, their quantum fluctuations and the corresponding uncertainty product.

  17. A single Abrikosov vortex trapped in a mesoscopic superconducting cylindrical surface.

    PubMed

    Carapella, G; Sabatino, P; Costabile, G

    2011-11-01

    We investigate the behaviour of a single Abrikosov vortex trapped in a mesoscopic superconducting cylindrical surface with a magnetic field applied transverse to its axis. In the framework of the time-dependent Ginzburg-Landau formalism we show that, provided the transport current and the magnetic field are not large, the vortex behaves as an overdamped quasi-particle in a tilted washboard potential. The cylindrical thin strip with the trapped vortex exhibits E(J) curves and time-dependent electric fields very similar to the ones exhibited by a resistively shunted Josephson weak link.

  18. Mesoscopic strain fields in woven composites: Experiments vs. finite element modeling

    NASA Astrophysics Data System (ADS)

    Nicoletto, Gianni; Anzelotti, Giancarlo; Riva, Enrica

    2009-03-01

    Detailed determination of strain in woven composite materials is fundamental for understanding their mechanics and for validating sophisticated computational models. The digital image correlation technique is briefly presented and applied to the full-field strain determination in a twill-weave carbon-fiber-reinforced-plastic (CFRP) composite under in-plane loading. The experimental results are used to assess companion results obtained with an ad hoc finite element-based model. The DIC vs. FEM comparison is carried out at the mesoscopic scale.

  19. Statistical model of dephasing in mesoscopic devices introduced in the scattering matrix formalism

    NASA Astrophysics Data System (ADS)

    Pala, Marco G.; Iannaccone, Giuseppe

    2004-06-01

    We propose a phenomenological model of dephasing in mesoscopic transport, based on the introduction of random-phase fluctuations in the computation of the scattering matrix of the system. A Monte Carlo averaging procedure allows us to extract electrical and microscopic device properties. We show that, in this picture, scattering matrix properties enforced by current conservation and time-reversal invariance still hold. In order to assess the validity of the proposed approach, we present simulations of conductance and magnetoconductance of Aharonov-Bohm rings that reproduce the behavior observed in experiments, in particular as far as aspects related to decoherence are concerned.

  20. Mesoscopic superposition and sub-Planck-scale structure in molecular wave packets

    SciTech Connect

    Ghosh, Suranjana; Banerji, J.; Panigrahi, P. K.; Chiruvelli, Aravind

    2006-01-15

    We demonstrate the possibility of realizing sub-Planck-scale structures in the mesoscopic superposition of molecular wave packets involving vibrational levels. The time evolution of the wave packet, taken here as the SU(2) coherent state of the Morse potential describing hydrogen iodide molecules, produces macroscopic-quantum-superposition-like states, responsible for the above phenomenon. We investigate the phase-space dynamics of the coherent state through the Wigner function approach and identify the interference phenomena behind the sub-Planck-scale structures. The optimal parameter ranges are specified for observing these features.

  1. Mesoscopic modeling of multi-physicochemical transport phenomena in porous media

    SciTech Connect

    Kang, Qinjin; Wang, Moran; Mukherjee, Partha P; Lichtner, Peter C

    2009-01-01

    We present our recent progress on mesoscopic modeling of multi-physicochemical transport phenomena in porous media based on the lattice Boltzmann method. Simulation examples include injection of CO{sub 2} saturated brine into a limestone rock, two-phase behavior and flooding phenomena in polymer electrolyte fuel cells, and electroosmosis in homogeneously charged porous media. It is shown that the lattice Boltzmann method can account for multiple, coupled physicochemical processes in these systems and can shed some light on the underlying physics occuning at the fundamental scale. Therefore, it can be a potential powerful numerical tool to analyze multi-physicochemical processes in various energy, earth, and environmental systems.

  2. Fully printable mesoscopic perovskite solar cells with organic silane self-assembled monolayer.

    PubMed

    Liu, Linfeng; Mei, Anyi; Liu, Tongfa; Jiang, Pei; Sheng, Yusong; Zhang, Lijun; Han, Hongwei

    2015-02-11

    By the introduction of an organic silane self-assembled monolayer, an interface-engineering approach is demonstrated for hole-conductor-free, fully printable mesoscopic perovskite solar cells based on a carbon counter electrode. The self-assembled silane monolayer is incorporated between the TiO2 and CH3NH3PbI3, resulting in optimized interface band alignments and enhanced charge lifetime. The average power conversion efficiency is improved from 9.6% to 11.7%, with a highest efficiency of 12.7%, for this low-cost perovskite solar cell.

  3. Charged, dipolar soft matter systems from a combined microscopic–mesoscopic viewpoint

    NASA Astrophysics Data System (ADS)

    Schröder, Christian; Steinhauser, Othmar

    2016-09-01

    As an example of charged, dipolar soft matter, the ionic liquid 1-ethyl-3-methyl-imidazolium dicyanamide is studied by coarse-grained molecular dynamics simulations. We focus on the link between microscopic and mesoscopic properties for both structure and dynamics. Thereby, the generalized Kirkwood g K-factor plays a central role in establishing this link which is not possible on the basis of molecular hydrodynamics. The decoupling between translational and rotational motion is indicative of the dynamical heterogeneity in ionic liquids.

  4. Magnetic field profile of a mesoscopic SQUID-shaped superconducting film

    NASA Astrophysics Data System (ADS)

    Rogeri, F.; Zadorosny, R.; Lisboa-Filho, P. N.; Sardella, E.; Ortiz, W. A.

    2013-07-01

    Using a genuinely tridimensional approach to the time-dependent Ginzburg-Landau theory, we have studied the local magnetic field profile of a mesoscopic superconductor in the so-called SQUID geometry, i.e., a square with a hole at the center connected to the outside vacuum through a very thin slit. Our investigation was carried out in both the Meissner and the mixed state. We have also studied the influence of the temperature on the space distribution of the local magnetic field.

  5. Physics-based statistical learning approach to mesoscopic model selection.

    PubMed

    Taverniers, Søren; Haut, Terry S; Barros, Kipton; Alexander, Francis J; Lookman, Turab

    2015-11-01

    In materials science and many other research areas, models are frequently inferred without considering their generalization to unseen data. We apply statistical learning using cross-validation to obtain an optimally predictive coarse-grained description of a two-dimensional kinetic nearest-neighbor Ising model with Glauber dynamics (GD) based on the stochastic Ginzburg-Landau equation (sGLE). The latter is learned from GD "training" data using a log-likelihood analysis, and its predictive ability for various complexities of the model is tested on GD "test" data independent of the data used to train the model on. Using two different error metrics, we perform a detailed analysis of the error between magnetization time trajectories simulated using the learned sGLE coarse-grained description and those obtained using the GD model. We show that both for equilibrium and out-of-equilibrium GD training trajectories, the standard phenomenological description using a quartic free energy does not always yield the most predictive coarse-grained model. Moreover, increasing the amount of training data can shift the optimal model complexity to higher values. Our results are promising in that they pave the way for the use of statistical learning as a general tool for materials modeling and discovery.

  6. Physics-based statistical learning approach to mesoscopic model selection

    NASA Astrophysics Data System (ADS)

    Taverniers, Søren; Haut, Terry S.; Barros, Kipton; Alexander, Francis J.; Lookman, Turab

    2015-11-01

    In materials science and many other research areas, models are frequently inferred without considering their generalization to unseen data. We apply statistical learning using cross-validation to obtain an optimally predictive coarse-grained description of a two-dimensional kinetic nearest-neighbor Ising model with Glauber dynamics (GD) based on the stochastic Ginzburg-Landau equation (sGLE). The latter is learned from GD "training" data using a log-likelihood analysis, and its predictive ability for various complexities of the model is tested on GD "test" data independent of the data used to train the model on. Using two different error metrics, we perform a detailed analysis of the error between magnetization time trajectories simulated using the learned sGLE coarse-grained description and those obtained using the GD model. We show that both for equilibrium and out-of-equilibrium GD training trajectories, the standard phenomenological description using a quartic free energy does not always yield the most predictive coarse-grained model. Moreover, increasing the amount of training data can shift the optimal model complexity to higher values. Our results are promising in that they pave the way for the use of statistical learning as a general tool for materials modeling and discovery.

  7. Analysis of the properties of the molecular-cluster xenon mixture in the mesoscopic phase transition region

    NASA Astrophysics Data System (ADS)

    Kurlapov, L. I.; Kassymov, A. B.

    2016-04-01

    We report on the results of calculation of the concentrations of cluster subcomponents in a molecular-cluster xenon mixture at temperatures and pressures at which the gas experiences a mesoscopic phase transition. The existence of such a transition follows from singularities of the temperature dependence of viscosity, from the behavior of the cluster thermodiffusion coefficient, and from the features of the distributions of cluster subcomponents in the centrifuge. The mesoscopic phase transition is manifested in the intermediate position of the molecular-cluster mixture between the gas and the liquid judging from its properties in the transition region.

  8. A new transport phenomenon in nanostructures: a mesoscopic analog of the Braess paradox encountered in road networks.

    PubMed

    Pala, Marco; Sellier, Hermann; Hackens, Benoit; Martins, Frederico; Bayot, Vincent; Huant, Serge

    2012-01-01

    The Braess paradox, known for traffic and other classical networks, lies in the fact that adding a new route to a congested network in an attempt to relieve congestion can degrade counterintuitively the overall network performance. Recently, we have extended the concept of the Braess paradox to semiconductor mesoscopic networks, whose transport properties are governed by quantum physics. In this paper, we demonstrate theoretically that, alike in classical systems, congestion plays a key role in the occurrence of a Braess paradox in mesoscopic networks.

  9. A new transport phenomenon in nanostructures: a mesoscopic analog of the Braess paradox encountered in road networks

    NASA Astrophysics Data System (ADS)

    Pala, Marco; Sellier, Hermann; Hackens, Benoit; Martins, Frederico; Bayot, Vincent; Huant, Serge

    2012-08-01

    The Braess paradox, known for traffic and other classical networks, lies in the fact that adding a new route to a congested network in an attempt to relieve congestion can degrade counterintuitively the overall network performance. Recently, we have extended the concept of the Braess paradox to semiconductor mesoscopic networks, whose transport properties are governed by quantum physics. In this paper, we demonstrate theoretically that, alike in classical systems, congestion plays a key role in the occurrence of a Braess paradox in mesoscopic networks.

  10. Universality and quantized response in bosonic mesoscopic tunneling

    NASA Astrophysics Data System (ADS)

    Yin, Shaoyu; Béri, Benjamin

    2016-06-01

    We show that tunneling involving bosonic wires and/or boson integer quantum Hall (bIQH) edges is characterized by features that are far more universal than those in their fermionic counterpart. Considering a pair of minimal geometries, we examine the tunneling conductance as a function of energy (e.g., chemical potential bias) at high and low energy limits, finding a low energy enhancement and a universal high versus zero energy relation that hold for all wire/bIQH edge combinations. Beyond this universality present in all the different topological (bIQH-edge) and nontopological (wire) setups, we also discover a number of features distinguishing the topological bIQH edges, which include a current imbalance to chemical potential bias ratio that is quantized despite the lack of conductance quantization in the bIQH edges themselves. The predicted phenomena require only initial states to be thermal and thus are well suited for tests with ultracold bosons forming wires and bIQH states. For the latter, we highlight a potential realization based on single component bosons in the recently observed Harper-Hofstadter band structure.

  11. Fabrication techniques for microfluidic paper-based analytical devices and their applications for biological testing: A review.

    PubMed

    Xia, Yanyan; Si, Jin; Li, Zhiyang

    2016-03-15

    Paper is increasingly recognized as a user-friendly and ubiquitous substrate for construction of microfluidic devices. Microfluidic paper-based analytical devices (μPADs) provide an alternative technology for development of affordable, portable, disposable and low-cost diagnostic tools for improving point of care testing (POCT) and disease screening in the developing world, especially in those countries with no- or low-infrastructure and limited trained medical and health professionals. We in this review present fabrication techniques for microfluidic devices and their respective applications for biological detection as reported to date. These include: (i) fabrication techniques: examples of devices fabricated by using two-dimensional (2D) and three-dimensional (3D) methods; (ii) detection application: biochemical, immunological and molecular detection by incorporating efficient detection methods such as, colorimetric detection, electrochemical detection, fluorescence detection, chemiluminescence (CL) detection, electrochemiluninescence (ECL) detection, photoelectrochemi (PEC) detection and so on. In addition, main advantages, disadvantages and future trends for the devices are also discussed in this review.

  12. Analysis of eight oil spill dispersants using rapid, in vitro tests for endocrine and other biological activity.

    PubMed

    Judson, Richard S; Martin, Matthew T; Reif, David M; Houck, Keith A; Knudsen, Thomas B; Rotroff, Daniel M; Xia, Menghang; Sakamuru, Srilatha; Huang, Ruili; Shinn, Paul; Austin, Christopher P; Kavlock, Robert J; Dix, David J

    2010-08-01

    The Deepwater Horizon oil spill has led to the use of >1 M gallons of oil spill dispersants, which are mixtures of surfactants and solvents. Because of this large scale use there is a critical need to understand the potential for toxicity of the currently used dispersant and potential alternatives, especially given the limited toxicity testing information that is available. In particular, some dispersants contain nonylphenol ethoxylates (NPEs), which can degrade to nonylphenol (NP), a known endocrine disruptor. Given the urgent need to generate toxicity data, we carried out a series of in vitro high-throughput assays on eight commercial dispersants. These assays focused on the estrogen and androgen receptors (ER and AR), but also included a larger battery of assays probing other biological pathways. Cytotoxicity in mammalian cells was also quantified. No activity was seen in any AR assay. Two dispersants showed a weak ER signal in one assay (EC50 of 16 ppm for Nokomis 3-F4 and 25 ppm for ZI-400). NPs and NPEs also had a weak signal in this same ER assay. Note that Corexit 9500, the currently used product, does not contain NPEs and did not show any ER activity. Cytotoxicity values for six of the dispersants were statistically indistinguishable, with median LC50 values approximately 100 ppm. Two dispersants, JD 2000 and SAF-RON GOLD, were significantly less cytotoxic than the others with LC50 values approaching or exceeding 1000 ppm. PMID:20602530

  13. Analysis of eight oil spill dispersants using rapid, in vitro tests for endocrine and other biological activity.

    PubMed

    Judson, Richard S; Martin, Matthew T; Reif, David M; Houck, Keith A; Knudsen, Thomas B; Rotroff, Daniel M; Xia, Menghang; Sakamuru, Srilatha; Huang, Ruili; Shinn, Paul; Austin, Christopher P; Kavlock, Robert J; Dix, David J

    2010-08-01

    The Deepwater Horizon oil spill has led to the use of >1 M gallons of oil spill dispersants, which are mixtures of surfactants and solvents. Because of this large scale use there is a critical need to understand the potential for toxicity of the currently used dispersant and potential alternatives, especially given the limited toxicity testing information that is available. In particular, some dispersants contain nonylphenol ethoxylates (NPEs), which can degrade to nonylphenol (NP), a known endocrine disruptor. Given the urgent need to generate toxicity data, we carried out a series of in vitro high-throughput assays on eight commercial dispersants. These assays focused on the estrogen and androgen receptors (ER and AR), but also included a larger battery of assays probing other biological pathways. Cytotoxicity in mammalian cells was also quantified. No activity was seen in any AR assay. Two dispersants showed a weak ER signal in one assay (EC50 of 16 ppm for Nokomis 3-F4 and 25 ppm for ZI-400). NPs and NPEs also had a weak signal in this same ER assay. Note that Corexit 9500, the currently used product, does not contain NPEs and did not show any ER activity. Cytotoxicity values for six of the dispersants were statistically indistinguishable, with median LC50 values approximately 100 ppm. Two dispersants, JD 2000 and SAF-RON GOLD, were significantly less cytotoxic than the others with LC50 values approaching or exceeding 1000 ppm.

  14. Analysis of Eight Oil Spill Dispersants Using Rapid, In Vitro Tests for Endocrine and Other Biological Activity

    PubMed Central

    Judson, Richard S.; Martin, Matthew T.; Reif, David M.; Houck, Keith A.; Knudsen, Thomas B.; Rotroff, Daniel M.; Xia, Menghang; Sakamuru, Srilatha; Huang, Ruili; Shinn, Paul; Austin, Christopher P.; Kavlock, Robert J.; Dix, David J.

    2010-01-01

    The Deepwater Horizon oil spill has led to the use of >1 M gallons of oil spill dispersants, which are mixtures of surfactants and solvents. Because of this large scale use there is a critical need to understand the potential for toxicity of the currently used dispersant and potential alternatives, especially given the limited toxicity testing information that is available. In particular, some dispersants contain nonylphenol ethoxylates (NPEs), which can degrade to nonylphenol (NP), a known endocrine disruptor. Given the urgent need to generate toxicity data, we carried out a series of in vitro high-throughput assays on eight commercial dispersants. These assays focused on the estrogen and androgen receptors (ER and AR), but also included a larger battery of assays probing other biological pathways. Cytotoxicity in mammalian cells was also quantified. No activity was seen in any AR assay. Two dispersants showed a weak ER signal in one assay (EC50 of 16 ppm for Nokomis 3-F4 and 25 ppm for ZI-400). NPs and NPEs also had a weak signal in this same ER assay. Note that Corexit 9500, the currently used product, does not contain NPEs and did not show any ER activity. Cytotoxicity values for six of the dispersants were statistically indistinguishable, with median LC50 values ∼100 ppm. Two dispersants, JD 2000, SAF-RON GOLD, were significantly less cytotoxic than the others with LC50 values approaching or exceeding 1000 ppm. PMID:20602530

  15. Mesoscopic bar magnet based on ε-Fe2O3 hard ferrite.

    PubMed

    Ohkoshi, Shin-Ichi; Namai, Asuka; Yamaoka, Takehiro; Yoshikiyo, Marie; Imoto, Kenta; Nasu, Tomomichi; Anan, Shizuka; Umeta, Yoshikazu; Nakagawa, Kosuke; Tokoro, Hiroko

    2016-01-01

    Ferrite magnets have a long history. They are used in motors, magnetic fluids, drug delivery systems, etc. Herein we report a mesoscopic ferrite bar magnet based on rod-shaped ε-Fe2O3 with a large coercive field (>25 kOe). The ε-Fe2O3-based bar magnet is a single crystal with a single magnetic domain along the longitudinal direction. A wide frequency range spectroscopic study shows that the crystallographic a-axis of ε-Fe2O3, which corresponds to the longitudinal direction of the bar magnet, plays an important role in linear and non-linear magneto-optical transitions, phonon modes, and the magnon (Kittel mode). Due to its multiferroic property, a magnetic-responsive non-linear optical sheet is manufactured as an application using an ε-Fe2O3-based bar magnet, resin, and polyethylene terephthalate. Furthermore, from the viewpoint of the large coercive field property, we demonstrate that a mesoscopic ε-Fe2O3 bar magnet can be used as a magnetic force microscopy probe. PMID:27273575

  16. Mesoscopic turbulence and local order in Janus particles self-propelling under an ac electric field.

    PubMed

    Nishiguchi, Daiki; Sano, Masaki

    2015-11-01

    To elucidate mechanisms of mesoscopic turbulence exhibited by active particles, we experimentally study turbulent states of nonliving self-propelled particles. We realize an experimental system with dense suspensions of asymmetrical colloidal particles (Janus particles) self-propelling on a two-dimensional surface under an ac electric field. Velocity fields of the Janus particles in the crowded situation can be regarded as a sort of turbulence because it contains many vortices and their velocities change abruptly. Correlation functions of their velocity field reveal the coexistence of polar alignment and antiparallel alignment interactions, which is considered to trigger mesoscopic turbulence. Probability distributions of local order parameters for polar and nematic orders indicate the formation of local clusters with particles moving in the same direction. A broad peak in the energy spectrum of the velocity field appears at the spatial scales where the polar alignment and the cluster formation are observed. Energy is injected at the particle scale and conserved quantities such as energy could be cascading toward the larger clusters. PMID:26651697

  17. Thermodynamics of the mesoscopic thermoelectric heat engine beyond the linear-response regime.

    PubMed

    Yamamoto, Kaoru; Hatano, Naomichi

    2015-10-01

    Mesoscopic thermoelectric heat engine is much anticipated as a device that allows us to utilize with high efficiency wasted heat inaccessible by conventional heat engines. However, the derivation of the heat current in this engine seems to be either not general or described too briefly, even inappropriately in some cases. In this paper, we give a clear-cut derivation of the heat current of the engine with suitable assumptions beyond the linear-response regime. It resolves the confusion in the definition of the heat current in the linear-response regime. After verifying that we can construct the same formalism as that of the cyclic engine, we find the following two interesting results within the Landauer-Büttiker formalism: the efficiency of the mesoscopic thermoelectric engine reaches the Carnot efficiency if and only if the transmission probability is finite at a specific energy and zero otherwise; the unitarity of the transmission probability guarantees the second law of thermodynamics, invalidating Benenti et al.'s argument in the linear-response regime that one could obtain a finite power with the Carnot efficiency under a broken time-reversal symmetry [Phys. Rev. Lett. 106, 230602 (2011)]. These results demonstrate how quantum mechanics constrains thermodynamics.

  18. A mesoscopic reaction rate model for shock initiation of multi-component PBX explosives.

    PubMed

    Liu, Y R; Duan, Z P; Zhang, Z Y; Ou, Z C; Huang, F L

    2016-11-01

    The primary goal of this research is to develop a three-term mesoscopic reaction rate model that consists of a hot-spot ignition, a low-pressure slow burning and a high-pressure fast reaction terms for shock initiation of multi-component Plastic Bonded Explosives (PBX). Thereinto, based on the DZK hot-spot model for a single-component PBX explosive, the hot-spot ignition term as well as its reaction rate is obtained through a "mixing rule" of the explosive components; new expressions for both the low-pressure slow burning term and the high-pressure fast reaction term are also obtained by establishing the relationships between the reaction rate of the multi-component PBX explosive and that of its explosive components, based on the low-pressure slow burning term and the high-pressure fast reaction term of a mesoscopic reaction rate model. Furthermore, for verification, the new reaction rate model is incorporated into the DYNA2D code to simulate numerically the shock initiation process of the PBXC03 and the PBXC10 multi-component PBX explosives, and the numerical results of the pressure histories at different Lagrange locations in explosive are found to be in good agreements with previous experimental data.

  19. Thermodynamics of the mesoscopic thermoelectric heat engine beyond the linear-response regime.

    PubMed

    Yamamoto, Kaoru; Hatano, Naomichi

    2015-10-01

    Mesoscopic thermoelectric heat engine is much anticipated as a device that allows us to utilize with high efficiency wasted heat inaccessible by conventional heat engines. However, the derivation of the heat current in this engine seems to be either not general or described too briefly, even inappropriately in some cases. In this paper, we give a clear-cut derivation of the heat current of the engine with suitable assumptions beyond the linear-response regime. It resolves the confusion in the definition of the heat current in the linear-response regime. After verifying that we can construct the same formalism as that of the cyclic engine, we find the following two interesting results within the Landauer-Büttiker formalism: the efficiency of the mesoscopic thermoelectric engine reaches the Carnot efficiency if and only if the transmission probability is finite at a specific energy and zero otherwise; the unitarity of the transmission probability guarantees the second law of thermodynamics, invalidating Benenti et al.'s argument in the linear-response regime that one could obtain a finite power with the Carnot efficiency under a broken time-reversal symmetry [Phys. Rev. Lett. 106, 230602 (2011)]. These results demonstrate how quantum mechanics constrains thermodynamics. PMID:26565226

  20. Thermodynamics of the mesoscopic thermoelectric heat engine beyond the linear-response regime

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kaoru; Hatano, Naomichi

    2015-10-01

    Mesoscopic thermoelectric heat engine is much anticipated as a device that allows us to utilize with high efficiency wasted heat inaccessible by conventional heat engines. However, the derivation of the heat current in this engine seems to be either not general or described too briefly, even inappropriately in some cases. In this paper, we give a clear-cut derivation of the heat current of the engine with suitable assumptions beyond the linear-response regime. It resolves the confusion in the definition of the heat current in the linear-response regime. After verifying that we can construct the same formalism as that of the cyclic engine, we find the following two interesting results within the Landauer-Büttiker formalism: the efficiency of the mesoscopic thermoelectric engine reaches the Carnot efficiency if and only if the transmission probability is finite at a specific energy and zero otherwise; the unitarity of the transmission probability guarantees the second law of thermodynamics, invalidating Benenti et al.'s argument in the linear-response regime that one could obtain a finite power with the Carnot efficiency under a broken time-reversal symmetry [Phys. Rev. Lett. 106, 230602 (2011), 10.1103/PhysRevLett.106.230602]. These results demonstrate how quantum mechanics constrains thermodynamics.

  1. Detecting weak coupling in mesoscopic systems with a nonequilibrium Fano resonance

    NASA Astrophysics Data System (ADS)

    Xiao, S.; Yoon, Y.; Lee, Y.-H.; Bird, J. P.; Ochiai, Y.; Aoki, N.; Reno, J. L.; Fransson, J.

    2016-04-01

    A critical aspect of quantum mechanics is the nonlocal nature of the wave function, a characteristic that may yield unexpected coupling of nominally isolated systems. The capacity to detect this coupling can be vital in many situations, especially those in which its strength is weak. In this work, we address this problem in the context of mesoscopic physics, by implementing an electron-wave realization of a Fano interferometer using pairs of coupled quantum point contacts (QPCs). Within this scheme, the discrete level required for a Fano resonance is provided by pinching off one of the QPCs, thereby inducing the formation of a quasibound state at the center of its self-consistent potential barrier. Using this system, we demonstrate a form of nonequilibrium Fano resonance (NEFR), in which nonlinear electrical biasing of the interferometer gives rise to pronounced distortions of its Fano resonance. Our experimental results are captured well by a quantitative theoretical model, which considers a system in which a standard two-path Fano interferometer is coupled to an additional, intruder, continuum. According to this theory, the observed distortions in the Fano resonance arise only in the presence of coupling to the intruder, indicating that the NEFR provides a sensitive means to infer the presence of weak coupling between mesoscopic systems.

  2. Mesoscopic segregation of excitation and inhibition in a brain network model.

    PubMed

    Malagarriga, Daniel; Villa, Alessandro E P; Garcia-Ojalvo, Jordi; Pons, Antonio J

    2015-02-01

    Neurons in the brain are known to operate under a careful balance of excitation and inhibition, which maintains neural microcircuits within the proper operational range. How this balance is played out at the mesoscopic level of neuronal populations is, however, less clear. In order to address this issue, here we use a coupled neural mass model to study computationally the dynamics of a network of cortical macrocolumns operating in a partially synchronized, irregular regime. The topology of the network is heterogeneous, with a few of the nodes acting as connector hubs while the rest are relatively poorly connected. Our results show that in this type of mesoscopic network excitation and inhibition spontaneously segregate, with some columns acting mainly in an excitatory manner while some others have predominantly an inhibitory effect on their neighbors. We characterize the conditions under which this segregation arises, and relate the character of the different columns with their topological role within the network. In particular, we show that the connector hubs are preferentially inhibitory, the more so the larger the node's connectivity. These results suggest a potential mesoscale organization of the excitation-inhibition balance in brain networks. PMID:25671573

  3. Mesoscopic turbulence and local order in Janus particles self-propelling under an ac electric field

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Daiki; Sano, Masaki

    2015-11-01

    To elucidate mechanisms of mesoscopic turbulence exhibited by active particles, we experimentally study turbulent states of nonliving self-propelled particles. We realize an experimental system with dense suspensions of asymmetrical colloidal particles (Janus particles) self-propelling on a two-dimensional surface under an ac electric field. Velocity fields of the Janus particles in the crowded situation can be regarded as a sort of turbulence because it contains many vortices and their velocities change abruptly. Correlation functions of their velocity field reveal the coexistence of polar alignment and antiparallel alignment interactions, which is considered to trigger mesoscopic turbulence. Probability distributions of local order parameters for polar and nematic orders indicate the formation of local clusters with particles moving in the same direction. A broad peak in the energy spectrum of the velocity field appears at the spatial scales where the polar alignment and the cluster formation are observed. Energy is injected at the particle scale and conserved quantities such as energy could be cascading toward the larger clusters.

  4. Diffuse phase transition in ferroelectrics with mesoscopic heterogeneity: Mean-field theory

    SciTech Connect

    Li, S.; Eastman, J.A.; Newnham, R.E.; Cross, L.E.

    1997-05-01

    The diffuse phase transition in ferroelectrics with mesoscopic heterogeneity has been discussed within the context of a superparaelectric model by using the Ginzburg-Landau formalism. In the Curie region ferroelectrics with mesoscopic heterogeneity are treated as {open_quotes}superparaelectrics{close_quotes} consisting of a mass of polar clusters, each of which has Ising character. Based on the mean-field theory, the influence of the finite-size effects of polar clusters on their structural instability has been discussed by considering a coherent lattice coupling between two structurally different regions. In particular, we have analytically derived the explicit solutions of the distribution of local polarizations. In turn, the processes of polar nanophase precipitation and coarsening have been also discussed in conjunction with the local chemical or structural inhomogeneity. Moreover, we have also analyzed the relationship between the local polarization distribution and the static dielectric susceptibility in ferroelectrics with the nanometric scale heterogeneity. The width of the Curie region is dependent upon the distribution of the sum of localized correlation length, which reflects the size distribution of heterogeneity. The presented analysis reveals that the diffuse phase transition is closely associated with the existence of nanometric polar clusters and their physical size distribution. Intriguingly, our theoretical results bear a very close resemblance to most experimental observations. {copyright} {ital 1997} {ital The American Physical Society}

  5. Phonon mechanisms of nonlinear decay and dephasing of mesoscopic vibrational systems

    NASA Astrophysics Data System (ADS)

    Atalaya, Juan; Kenny, Thomas W.; Dykman, Mark I.

    2015-03-01

    The frequencies and the decay rates of mesoscopic oscillators depend on vibration amplitudes. Nonlinear decay has been seen recently in various nano- and micro-mechanical systems. Here we consider a microscopic mechanism of nonlinear decay, the nonlinear coupling of the vibrational mode of interest, for example, a flexural mode, to other vibrations. Typically, the modes of interest have low eigenfrequencies ω0. Their decay comes from the coupling to acoustic-phonon type vibrations with much higher frequency and density of states. Thus, nonlinear decay requires quartic anharmonic coupling or cubic anharmonicity in the higher order. We find the decay rate for the inverse lifetime of the involved phonons, which is determined by the internal nonlinearity and the boundary scattering, being either much larger or smaller than ω0. The results extend the thermo-elastic, Akhiezer, and Landau-Rumer decay theory to nonlinear decay of mesoscopic modes and make specific predictions on the temperature and frequency dependence of the decay rate for different types of systems. We show that nonlinear decay is invariably accompanied by dephasing. We also show that in nano-electro-mechanical systems the decay rate can be electrostatically controlled.

  6. Mesoscopic bar magnet based on ɛ-Fe2O3 hard ferrite

    NASA Astrophysics Data System (ADS)

    Ohkoshi, Shin-Ichi; Namai, Asuka; Yamaoka, Takehiro; Yoshikiyo, Marie; Imoto, Kenta; Nasu, Tomomichi; Anan, Shizuka; Umeta, Yoshikazu; Nakagawa, Kosuke; Tokoro, Hiroko

    2016-06-01

    Ferrite magnets have a long history. They are used in motors, magnetic fluids, drug delivery systems, etc. Herein we report a mesoscopic ferrite bar magnet based on rod-shaped ɛ-Fe2O3 with a large coercive field (>25 kOe). The ɛ-Fe2O3-based bar magnet is a single crystal with a single magnetic domain along the longitudinal direction. A wide frequency range spectroscopic study shows that the crystallographic a-axis of ɛ-Fe2O3, which corresponds to the longitudinal direction of the bar magnet, plays an important role in linear and non-linear magneto-optical transitions, phonon modes, and the magnon (Kittel mode). Due to its multiferroic property, a magnetic-responsive non-linear optical sheet is manufactured as an application using an ɛ-Fe2O3-based bar magnet, resin, and polyethylene terephthalate. Furthermore, from the viewpoint of the large coercive field property, we demonstrate that a mesoscopic ɛ-Fe2O3 bar magnet can be used as a magnetic force microscopy probe.

  7. Mesoscopic analysis of online social networks: The role of negative ties

    NASA Astrophysics Data System (ADS)

    Esmailian, Pouya; Abtahi, Seyed Ebrahim; Jalili, Mahdi

    2014-10-01

    A class of networks are those with both positive and negative links. In this manuscript, we studied the interplay between positive and negative ties on mesoscopic level of these networks, i.e., their community structure. A community is considered as a tightly interconnected group of actors; therefore, it does not borrow any assumption from balance theory and merely uses the well-known assumption in the community detection literature. We found that if one detects the communities based on only positive relations (by ignoring the negative ones), the majority of negative relations are already placed between the communities. In other words, negative ties do not have a major role in community formation of signed networks. Moreover, regarding the internal negative ties, we proved that most unbalanced communities are maximally balanced, and hence they cannot be partitioned into k nonempty sub-clusters with higher balancedness (k ≥2 ). Furthermore, we showed that although the mediator triad ++- (hostile-mediator-hostile) is underrepresented, it constitutes a considerable portion of triadic relations among communities. Hence, mediator triads should not be ignored by community detection and clustering algorithms. As a result, if one uses a clustering algorithm that operates merely based on social balance, mesoscopic structure of signed networks significantly remains hidden.

  8. Breakdown of conductance quantization and mesoscopic fluctuations in the quasiballistic regime

    SciTech Connect

    Glazman, L.I. ); Jonson, M. Solid State Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee Institute of Theoretical Physics, Chalmers University of Technology, S-412 96 Goeteborg )

    1991-08-15

    We present an analytical theory of corrections to the quantum ballistic conductance of a channel formed in a two-dimensional electron gas (2D EG). Backscattering that causes the corrections occurs inside the channel and is due to a random potential produced by charged donors. The spatial separation of the donors from the 2D EG implies that the scattering potential is smooth and hence gives a natural scale for the width of the channel. We derive the necessary conditions for conductance quantization in both cases of narrow and wide channels. These conditions determine how many quantized steps of the conductance can be observed at a given channel length. An analysis based on our results shows that in existing experiments breakdown of the conductance quantization and a crossover to mesoscopic fluctuations occurs in the narrow-channel limit. The dominating mechanism of breakdown is backscattering within the propagating mode with the largest mode number. This conclusion is validated by a comparison with experimental data. We determine the amplitude of mesoscopic conductance fluctuations in the ballistic regime and derive the minimum temperature for which they are smeared out.

  9. Mesoscopic bar magnet based on ε-Fe2O3 hard ferrite

    PubMed Central

    Ohkoshi, Shin-ichi; Namai, Asuka; Yamaoka, Takehiro; Yoshikiyo, Marie; Imoto, Kenta; Nasu, Tomomichi; Anan, Shizuka; Umeta, Yoshikazu; Nakagawa, Kosuke; Tokoro, Hiroko

    2016-01-01

    Ferrite magnets have a long history. They are used in motors, magnetic fluids, drug delivery systems, etc. Herein we report a mesoscopic ferrite bar magnet based on rod-shaped ε-Fe2O3 with a large coercive field (>25 kOe). The ε-Fe2O3–based bar magnet is a single crystal with a single magnetic domain along the longitudinal direction. A wide frequency range spectroscopic study shows that the crystallographic a-axis of ε-Fe2O3, which corresponds to the longitudinal direction of the bar magnet, plays an important role in linear and non-linear magneto-optical transitions, phonon modes, and the magnon (Kittel mode). Due to its multiferroic property, a magnetic-responsive non-linear optical sheet is manufactured as an application using an ε-Fe2O3–based bar magnet, resin, and polyethylene terephthalate. Furthermore, from the viewpoint of the large coercive field property, we demonstrate that a mesoscopic ε-Fe2O3 bar magnet can be used as a magnetic force microscopy probe. PMID:27273575

  10. Physics Characterization of TLD-600 and TLD-700 and Acceptance Testing of New XRAD 160 Biological X-Ray Irradiator

    NASA Astrophysics Data System (ADS)

    Cao, Yanan

    2: Acceptance testing of new X-RAD 160 Biological X-Ray Irradiator. Purpose: An X-RAD 160 Biological X-Ray Irradiator was recently installed at Duke University to serve as a key device for cellular radiobiology research. The purpose of this study is to perform acceptance testing on the new irradiator for operator radiation safety and irradiation specifications. Methods: The acceptance testing included tests of the following components: (1) Leakage radiation survey, (2) Half-value layer (beam quality), (3) Uniformity, (4) KVp accuracy, (5) Exposure at varying mA (linearity of mA), (6) Exposure at varying kVp, (7) Inverse square measurements, (8) Field size measurement, (9) Exposure constancy. The irradiation parameters for each components of first round of acceptance testing performed on September 21, 2012 were: Leakage radiation survey (none, 160 kVp, 18 mA, 200s), Beam quality (40cm, 50-140 kVp in 10 kVp incensement, 1 mA, 10s, none), Uniformity (40cm, 160 kVp, 18 mA, 15s, F1), KVp accuracy (40cm, 50-150 kVp in 10 kVp incensement, 10 mA, 15s, none), Linearity of mA (40cm, 160 kVp, 2-18 mA, 15s, none), Inverse square measurements (20-63cm, 160 kVp, 1mA, 30s, none), Field size measurement (40cm, 160 kVp, 10 mA, 15s, none), Exposure constancy (40cm, 160 kVp, 18 mA, 20s, none). The irradiation parameters for each components for each components of second round of acceptance testing performed on November 18, 2012 were: Beam quality (40cm, 35-150 kVp, 1 mA, 10s, F1), KVp accuracy (40cm, 35-150 kVp, 1 mA, 10s, F1), Variation of kVp (40cm, 160 kVp, 18 mA, 30s, F1), Linearity of mA (40cm, 160 kVp, 1-18 mA, 30s, F1), Uniformity (40cm, 160 kVp, 18 mA, 30s, F1), Inverse square measurements (20-63cm, 160 kVp, 18 mA, 30s, F1). Results: The first round of acceptance testing performed on September 21, 2012 failed due to the fact that the measured exposure along the X-axis was significantly non-uniform; the exposure greatly decreases going in the left direction, which is a clear

  11. Factors in seventh grade academics associated with performance levels on the tenth grade biology end of course test in selected middle and high schools in northwest Georgia

    NASA Astrophysics Data System (ADS)

    Ward, Jennifer Henry

    This study attempted to identify factors in seventh grade academics that are associated with overall success in tenth grade biology. The study addressed the following research questions: Are there significant differences in performance levels in seventh grade Criterion Referenced Competency Test (CRCT) scores in science, math, reading, and language arts associated with performance categories in tenth grade biology End of Course Test (EOCT) and the following demographic variables : gender, ethnicity, socioeconomic status, disability category, and English language proficiency level? Is there a relationship among the categorical variables on the tenth grade biology EOCT and the same five demographic variables? Retrospective causal comparative research was used on a representative sample from the middle schools in three North Georgia counties who took the four CRCTs in the 2006-2007 school year, and took the biology EOCT in the 2009-2010 school year. Chi square was used to determine the relationships of the various demographic variables on three biology EOCT performance categories. Twoway ANOVA determined relationships between the seventh grade CRCT scores of students in the various demographic groups and their performance levels on the biology EOCT. Students' performance levels on the biology EOCT matched their performance levels on the seventh grade CRCTs consistently. Females performed better than males on all seventh grade CRCTs. Black and Hispanic students did worse than White and Asian/Asian Indian students on the math CRCT. Students living in poverty did worse on reading and language arts CRCTs than students who were better off. Special education students did worse on science, reading, and language arts CRCTs than students not receiving special education services. English language learners did worse than native English speakers on all seventh grade CRCTs. These findings suggest that remedial measures may be taken in the seventh grade that could impact

  12. Assessing Students' Abilities in Processes of Scientific Inquiry in Biology Using a Paper-and-Pencil Test

    ERIC Educational Resources Information Center

    Nowak, Kathrin Helena; Nehring, Andreas; Tiemann, Rüdiger; Upmeier zu Belzen, Annette

    2013-01-01

    The aim of the study was to describe, categorise and analyse students' (aged 14-16) processes of scientific inquiry in biology and chemistry education. Therefore, a theoretical structure for scientific inquiry for both biology and chemistry, the VerE model, was developed. This model consists of nine epistemological acts, which combine…

  13. Using Models at the Mesoscopic Scale in Teaching Physics: Two Experimental Interventions in Solid Friction and Fluid Statics

    ERIC Educational Resources Information Center

    Besson, Ugo; Viennot, Laurence

    2004-01-01

    This article examines the didactic suitability of introducing models at an intermediate (i.e. mesoscopic) scale in teaching certain subjects, at an early stage. The design and evaluation of two short sequences based on this rationale will be outlined: one bears on propulsion by solid friction, the other on fluid statics in the presence of gravity.…

  14. Development and Application of a Two-Tier Diagnostic Test Measuring College Biology Students' Understanding of Diffusion and Osmosis after a Course of Instruction.

    ERIC Educational Resources Information Center

    Odom, Arthur Louis; Barrow, Lloyd H.

    1995-01-01

    Presents a diagnostic test for measuring college biology students' understanding of diffusion. Three general steps were used: (1) defining the content boundaries; (2) collecting information on students' misconceptions; and (3) instrument development. The split half reliability was 0.74, difficulty indices ranged from 0.23 to 0.95, and the…

  15. Biological testing and chemical analysis of process materials from an integrated two stage coal liquefaction: a status report

    SciTech Connect

    Wilson, B.W.; Buhl, P.; Moroni, E.C.

    1983-07-01

    Samples for chemical characterization and biological testing were obtained from ITSL runs 3LCF7, 3LCF8 and 3LCF9. Chemical analysis of these materials showed that SCT products were composed of fewer compounds than analogous materials from Solvent Refined Coal (SRC) processes. Major components in the SCT materials were three-, four-, five- and six-ring neutral polycyclic aromatic hydrocarbons (PAH). Methyl(C/sub 1/) and C/sub 2/ homologs of these compounds were present in relatively low concentrations, compared to their non-alkylated homologs. Organic nitrogen was primarily in the form of tertiary polycyclic aromatic nitrogen heterocycles and carbazoles. Little or no amino PAH (APAH) or cyano PAH were detected in samples taken during normal PDU operations, however, mutagenic APAH were produced during off-normal operation. Microbial mutagenicity appeared to be due mainly to the presence of APAH which were probably formed in the LC finer due to failure of the catalyst to promote deamination following carbon-nitrogen bond scission of nitrogen-containing hydroaromatics. This failure was observed for the off-normal runs where it was likely that the catalyst had been deactivated. Carcinogenic activity of ITSL materials as assessed by (tumors per animal) in the initiation/promotion mouse skin painting assay was slightly reduced for materials produced with good catalyst under normal operation compared to those collected during recycle of the LC Finer feed. Initiation activity of the latter samples did not appear to be significantly different from that of other coal derived materials with comparable boiling ranges. The observed initiation activity was not unexpected, considering analytical data which showed the presence of four-, five- and six-ring PAH in ITSL materials.

  16. Using daily satellite observations to estimate emissions of short-lived air pollutants on a mesoscopic scale

    NASA Astrophysics Data System (ADS)

    Mijling, B.; van der A, R. J.

    2012-09-01

    Emission inventories of air pollutants are crucial information for policy makers and form important input data for air quality models. Using satellite observations for emission estimates has important advantages over bottom-up emission inventories: they are spatially consistent, have high temporal resolution, and enable updates shortly after the satellite data become available. We present a new algorithm specifically designed to use daily satellite observations of column concentrations for fast updates of emission estimates of short-lived atmospheric constituents on a mesoscopic scale (˜25 × 25 km2). The algorithm needs only one forward model run from a chemical transport model to calculate the sensitivity of concentration to emission, using trajectory analysis to account for transport away from the source. By using a Kalman filter in the inverse step, optimal use of the a priori knowledge and the newly observed data is made. We apply the algorithm for NOx emission estimates of East China, using the CHIMERE model on a 0.25 degree resolution together with tropospheric NO2column retrievals of the OMI and GOME-2 satellite instruments. Closed loop tests show that the algorithm is capable of reproducing new emission scenarios. Applied with real satellite data, the algorithm is able to detect emerging sources (e.g., new power plants), and improves emission information for areas where proxy data are not or badly known (e.g., shipping emissions). Chemical transport model runs with the daily updated emission estimates provide better spatial and temporal agreement between observed and simulated concentrations, facilitating improved air quality forecasts.

  17. Development and application of a two-tier diagnostic test measuring college biology students' understanding of diffusion and osmosis after a course of instruction

    NASA Astrophysics Data System (ADS)

    Odom, Arthur Louis; Barrow, Lloyd H.

    This study involved the development and application of a two-tier diagnostic test measuring college biology students' understanding of diffusion and osmosis after a course of instruction. The development procedure had three general steps: defining the content boundaries of the test, collecting information on students' misconceptions, and instrument development. Misconception data were collected from interviews and multiple-choice questions with free response answers. The data were used to develop 12 two-tier multiple choice items in which the first tier examined content knowledge and the second examined understanding of that knowledge. The conceptual knowledge examined was the particulate and random nature of matter, concentration and tonicity, the influence of life forces on diffusion and osmosis, membranes, kinetic energy of matter, the process of diffusion, and the process of osmosis. The diagnostic instrument was administered to 240 students (123 non-biology majors and 117 biology majors) enrolled in a college freshman biology laboratory course. The students had completed a unit on diffusion and osmosis. The content taught was carefully defined by propositional knowledge statements, and was the same content that defined the content boundaries of the test. The split-half reliability was .74. Difficulty indices ranged from 0.23 to 0.95, and discrimination indices ranged from 0.21 to 0.65. Each item was analyzed to determine student understanding of, and identify misconceptions about, diffusion and osmosis.Received: 18 June 1993; Revised: 16 February 1994;

  18. Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic 2D Coulomb Crystal of ^9Be^+

    NASA Astrophysics Data System (ADS)

    Sawyer, Brian; Britton, Joseph; Teale, Carson; Keith, Adam; Wang, Joseph; Freericks, James; Bollinger, John

    2013-04-01

    We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglement between ion valence electron spins and collective motion. Our system is a ˜400 μm-diameter planar crystal of several hundred ^9Be^+ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the ^9Be^+ valence electron spins, we apply a homogeneous spin-dependent optical dipole force to excite arbitrary transverse modes with wavelengths ranging from the array diameter to the interparticle spacing of ˜20 μm. In addition to temperature measurements, this spin-motion entanglement induced by the spin-dependent optical dipole force allows for extremely sensitive detection of external forces (˜100 yN) acting on the ion crystal. Characterization of mode frequencies and temperatures is critical for quantum simulation experiments that make use of the ion spins.

  19. Mesoscopic Simulation Study of Wall Roughness Effects in Micro-channel Flows of Dense Emulsions

    NASA Astrophysics Data System (ADS)

    Scagliarini, Andrea; Sbragaglia, Mauro; Bernaschi, Massimo

    2015-12-01

    We study the Poiseuille flow of a soft-glassy material above the jamming point, where the material flows like a complex fluid with Herschel-Bulkley rheology. Microscopic plastic rearrangements and the emergence of their spatial correlations induce cooperativity flow behavior whose effect is pronounced in presence of confinement. With the help of lattice Boltzmann numerical simulations of confined dense emulsions, we explore the role of geometrical roughness in providing activation of plastic events close to the boundaries. We probe also the spatial configuration of the fluidity field, a continuum quantity which can be related to the rate of plastic events, thereby allowing us to establish a link between the mesoscopic plastic dynamics of the jammed material and the macroscopic flow behaviour.

  20. Superposition and entanglement of mesoscopic squeezed vacuum states in cavity QED

    SciTech Connect

    Chen Changyong; Feng Mang; Gao Kelin

    2006-03-15

    We propose a scheme to generate superposition and entanglement between the mesoscopic squeezed vacuum states by considering the two-photon interaction of N two-level atoms in a cavity with high quality factor, assisted by a strong driving field. By virtue of specific choices of the cavity detuning, a number of multiparty entangled states can be prepared, including the entanglement between the atomic and the squeezed vacuum cavity states and between the squeezed vacuum states and the coherent states of the cavities. We also present how to prepare entangled states and 'Schroedinger cats' states regarding the squeezed vacuum states of the cavity modes. The possible extension and application of our scheme are discussed. Our scheme is close to the reach with current cavity QED techniques.

  1. Mesoscopic simulation of phase behaviors and structures in an amphiphile-solvent system

    NASA Astrophysics Data System (ADS)

    Yamada, Kohtaro; Yasuno, Emiko; Kawabata, Youhei; Okuzono, Tohru; Kato, Tadashi

    2014-06-01

    We have performed a three-dimensional simulation of mesoscopic structures in a mixture of AB amphiphilic molecule and C solvent by employing the density-functional theory under the conditions that (i) the size of the AB is much larger than C and (ii) the affinity between A and B is much larger than the affinity between B and C. First, we have calculated the free energy of five periodic structures, i.e., the lamellar phase, hexagonally packed cylinders, body-centered-cubic spheres, face-centered-cubic spheres, and gyroid phase for different sets of the concentration of AB (ϕ¯AB) and the χ parameter (χAC). By comparing the free energies for these structures, the χAC-ϕ ¯AB phase diagram has been obtained. In addition to these periodic structures, it has been shown that nonperiodic structures such as spherical and rodlike micelles can be obtained although they might be metastable phase.

  2. Balanced double-loop mesoscopic interferometer based on Josephson proximity nanojunctions

    SciTech Connect

    Ronzani, Alberto Altimiras, Carles; Giazotto, Francesco

    2014-01-20

    We report on the fabrication and characterization of a two-terminal mesoscopic interferometer based on three V/Cu/V Josephson junctions having nanoscale cross-section. The junctions have been arranged in a double-ring geometry realized by metallic thin film deposition through a suspended mask defined by electron beam lithography. Although a significant amount of asymmetry between the critical current of each junction is observed, we show that the interferometer is able to suppress the supercurrent to a level lower than 6 parts per thousand, being here limited by measurement resolution. The present nano-device is suitable for low-temperature magnetometric and gradiometric measurements over the micrometric scale.

  3. Mesoscopic modeling of liquid water transport in polymer electrolyte fuel cells

    SciTech Connect

    Mukherjee, Partha P; Wang, Chao Yang

    2008-01-01

    A key performance limitation in polymer electrolyte fuel cells (PEFC), manifested in terms of mass transport loss, originates from liquid water transport and resulting flooding phenomena in the constituent components. Liquid water leads to the coverage of the electrochemically active sites in the catalyst layer (CL) rendering reduced catalytic activity and blockage of the available pore space in the porous CL and fibrous gas diffusion layer (GDL) resulting in hindered oxygen transport to the active reaction sites. The cathode CL and the GDL therefore playa major role in the mass transport loss and hence in the water management of a PEFC. In this article, we present the development of a mesoscopic modeling formalism coupled with realistic microstructural delineation to study the profound influence of the pore structure and surface wettability on liquid water transport and interfacial dynamics in the PEFC catalyst layer and gas diffusion layer.

  4. A Coarse Estimation of Cell Size Region from a Mesoscopic Stochastic Cell Cycle Model

    NASA Astrophysics Data System (ADS)

    Yi, Ming; Jia, Ya; Liu, Quan; Zhu, Chun-Lian; Yang, Li-Jian

    2007-07-01

    Based on a deterministic cell cycle model of fission yeast, the effects of the finite cell size on the cell cycle regulation in wee1- cdc25Δ double mutant type are numerically studied by using of the chemical Langevin equations. It is found that at a certain region of cell size, our numerical results from the chemical Langevin equations are in good qualitative agreement with the experimental observations. The two resettings to the G2 phase from early stages of mitosis can be induced under the moderate cell size. The quantized cycle times can be observed during such a cell size region. Therefore, a coarse estimation of cell size is obtained from the mesoscopic stochastic cell cycle model.

  5. Bohm-Aharonov and Kondo effects on tunneling currents in a mesoscopic ring

    SciTech Connect

    Davidovich, M.A.; Anda, E.V.; Chiappe, G.

    1997-03-01

    We present an analysis of the Kondo effect on the Bohm-Aharonov oscillations of the tunneling currents in a mesoscopic ring with a quantum dot inserted in one of its arms. The system is described by an Anderson-impurity tight-binding Hamiltonian where the electron-electron interaction is restricted to the dot. The currents are obtained using nonequilibrium Green functions calculated through a cumulant diagrammatic expansion in the chain approximation. It is shown that at low temperature, even with the system out of resonance, the Kondo peak provides a channel for the electron to tunnel through the dot, giving rise to the Bohm-Aharonov oscillations of the current. At high temperature these oscillations are important only if the dot level is aligned to the Fermi level, when the resonance condition is satisfied. {copyright} {ital 1997} {ital The American Physical Society}

  6. Revealing the flux: Using processed Husimi maps to visualize dynamics of bound systems and mesoscopic transport

    NASA Astrophysics Data System (ADS)

    Mason, Douglas J.; Borunda, Mario F.; Heller, Eric J.

    2015-04-01

    We elaborate upon the "processed Husimi map" representation for visualizing quantum wave functions using coherent states as a measurement of the local phase space to produce a vector field related to the probability flux. Adapted from the Husimi projection, the processed Husimi map is mathematically related to the flux operator under certain limits but offers a robust and flexible alternative since it can operate away from these limits and in systems that exhibit zero flux. The processed Husimi map is further capable of revealing the full classical dynamics underlying a quantum wave function since it reverse engineers the wave function to yield the underlying classical ray structure. We demonstrate the capabilities of processed Husimi maps on bound systems with and without electromagnetic fields, as well as on open systems on and off resonance, to examine the relationship between closed system eigenstates and mesoscopic transport.

  7. Four-terminal resistances in mesoscopic networks of metallic wires: Weak localisation and correlations

    NASA Astrophysics Data System (ADS)

    Texier, Christophe; Montambaux, Gilles

    2016-01-01

    We consider the electronic transport in multi-terminal mesoscopic networks of weakly disordered metallic wires. After a brief description of the classical transport, we analyse the weak localisation (WL) correction to the four-terminal resistances, which involves an integration of the Cooperon over the wires with proper weights. We provide an interpretation of these weights in terms of classical transport properties. We illustrate the formalism on examples and show that weak localisation to four-terminal conductances may become large in some situations. In a second part, we study the correlations of four-terminal resistances and show that integration of Diffuson and Cooperon inside the network involves the same weights as the WL. The formulae are applied to multiconnected wire geometries.

  8. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  9. Ex situ elaborated proximity mesoscopic structures for ultrahigh vacuum scanning tunneling spectroscopy

    SciTech Connect

    Stolyarov, V. S.; Cren, T. Debontridder, F.; Brun, C.; Veshchunov, I. S.; Skryabina, O. V.; Rusanov, A. Yu.; Roditchev, D.

    2014-04-28

    We apply ultrahigh vacuum Scanning Tunneling Spectroscopy (STS) at ultra-low temperature to study proximity phenomena in metallic Cu in contact with superconducting Nb. In order to solve the problem of Cu-surface contamination, Cu(50 nm)/Nb(100 nm) structures are grown by respecting the inverted order of layers on SiO{sub 2}/Si substrate. Once transferred into vacuum, the samples are cleaved at the structure-substrate interface. As a result, a contamination-free Cu-surface is exposed in vacuum. It enables high-resolution STS of superconducting correlations induced by proximity from the underlying superconducting Nb layer. By applying magnetic field, we generate unusual proximity-induced superconducting vortices and map them with a high spatial and energy resolution. The suggested method opens a way to access local electronic properties of complex electronic mesoscopic devices by performing ex situ STS under ultrahigh vacuum.

  10. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-30

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

  11. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    NASA Astrophysics Data System (ADS)

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

  12. Reprint of: Four-terminal resistances in mesoscopic networks of metallic wires: Weak localisation and correlations

    NASA Astrophysics Data System (ADS)

    Texier, Christophe; Montambaux, Gilles

    2016-08-01

    We consider the electronic transport in multi-terminal mesoscopic networks of weakly disordered metallic wires. After a brief description of the classical transport, we analyse the weak localisation (WL) correction to the four-terminal resistances, which involves an integration of the Cooperon over the wires with proper weights. We provide an interpretation of these weights in terms of classical transport properties. We illustrate the formalism on examples and show that weak localisation to four-terminal conductances may become large in some situations. In a second part, we study the correlations of four-terminal resistances and show that integration of Diffuson and Cooperon inside the network involves the same weights as the WL. The formulae are applied to multiconnected wire geometries.

  13. Gate-tunable indirect exchange interaction in spin-orbit-coupled mesoscopic rings

    NASA Astrophysics Data System (ADS)

    Nikoofard, H.; Heidari Semiromi, E.

    2015-05-01

    We study the carrier-mediated exchange interaction, the so-called Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling, between two magnetic impurity moments embedded in a semiconductor mesoscopic ring. We treat the ring in the presence of an Aharonov-Bohm-type magnetic flux and the Rashba and Dresselhaus spin-orbit interactions (RSOI and DSOI). Energy eigenvalues of the system are obtained within a tight-binding framework and the strength of the indirect exchange interaction vs. RSOI strengths are plotted for different values of DSOI strength. The results show that the type of the impurity magnetic order, ferromagnetic (F) or antiferromagnetic (AF), depends on the RSOI and DSOI strengths. This leads to a full electrical control on the magnetic alignment of the system through, e.g., an external gate voltage.

  14. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    PubMed Central

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  15. Verification of mesoscopic models of viscoelastic fluids with a non-monotonic flow curve

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Julia L.; Skul'skiy, Oleg I.

    2016-02-01

    The non-monotonic flow curve of a 1 wt.% polyacrylonitrile solution in dimethyl sulfoxide is described by two mesoscopic models: the modified Vinogradov-Pokrovsky model and the model proposed by Remmelgas, Harrison and Leal. To obtain an adequate description of the experimental curve, we have selected suitable internal parameters for these models. Analytical solutions for the Couette-Poiseuille flow problems are determined in parametric form, which allows us to plot the distribution of stress components and anisotropy tensor as well as the velocity profiles containing closed loops and weak tangential discontinuities. It is shown that both models predict a similar qualitative picture of structure evolution, but exhibit a significant discrepancy in the quantitative description of the magnitude of molecular chain stretching.

  16. 3. QUANTUM DOTS AND WELLS, MESOSCOPIC NETWORKS : Submicron charge-density-wave devices

    NASA Astrophysics Data System (ADS)

    van der Zant, H. J. S.; Markovic, N.; Slot, E.

    2001-10-01

    We review our fabrication methods to produce submicron charge-density-wave (CDW) structures and present measurements of CDW dynamics on a microscopic scale. Our data show that mesoscopic CDW dynamics is different from bulk behavior. We have studied current-conversion and found a size-effect that can not be accounted for by existing models. An explanation might be that the removal and addition of wave fronts becomes correlated in time when probe spacing is reduced below a few µm. On small segments we occasionally observe negative differential resistance in the I(V) characteristics and sometimes the resistance may even become negative. We believe that the interplay between CDW deformations (strain) and quasi-particles may yield non-equilibrium effects that play a crucial role in this new phenomenon. No detailed theoretical calculations are available. Our measurements clearly show the need of a microscopic model for CDW dynamics.

  17. Whispering-gallery acoustic sensing: Characterization of mesoscopic films and scanning probe microscopy applications

    NASA Astrophysics Data System (ADS)

    La Rosa, Andres H.; Li, Nan; Fernandez, Rodolfo; Wang, Xiaohua; Nordstrom, Richard; Padigi, S. K.

    2011-09-01

    Full understanding of the physics underlying the striking changes in viscoelasticity, relaxation time, and phase transitions that mesoscopic fluid-like films undergo at solid-liquid interfaces, or under confinement between two sliding solid boundaries, constitutes one of the major challenges in condensed matter physics. Their role in the imaging process of solid substrates by scanning probe microscopy (SPM) is also currently controversial. Aiming at improving the reliability and versatility of instrumentation dedicated to characterize mesoscopic films, a noninvasive whispering-gallery acoustic sensing (WGAS) technique is introduced; its application as feedback control in SPM is also demonstrated. To illustrate its working principle and potential merits, WGAS has been integrated into a SPM that uses a sharp tip attached to an electrically driven 32-kHz piezoelectric tuning fork (TF), the latter also tighten to the operating microscope's frame. Such TF-based SPMs typically monitor the TF's state of motion by electrical means, hence subjected to the effects caused by the inherent capacitance of the device (i.e., electrical resonance differing from the probe's mechanical resonance). Instead, the novelty of WGAS resides in exploiting the already existent microscope's frame as an acoustic cavity (its few centimeter-sized perimeter closely matching the operating acoustic wavelength) where standing-waves (generated by the nanometer-sized oscillations of the TF's tines) are sensitively detected by an acoustic transducer (the latter judiciously placed around the microscope's frame perimeter for attaining maximum detection). This way, WGAS is able to remote monitoring, via acoustic means, the nanometer-sized amplitude motion of the TF's tines. (This remote-detection method resembles the ability to hear faint, but still clear, levels of sound at the galleries of a cathedral, despite the extraordinary distance location of the sound source.) In applications aiming at

  18. Current Status and Recommendations for the Future of Research, Teaching, and Testing in the Biological Sciences of Radiation Oncology: Report of the American Society for Radiation Oncology Cancer Biology/Radiation Biology Task Force, Executive Summary

    SciTech Connect

    Wallner, Paul E.; Anscher, Mitchell S.; Barker, Christopher A.; Bassetti, Michael; Bristow, Robert G.; Dicker, Adam P.; Formenti, Silvia C.; Graves, Edward E.; Hahn, Stephen M.; Hei, Tom K.; Kimmelman, Alec C.; Kirsch, David G.; Kozak, Kevin R.; Lawrence, Theodore S.; Marples, Brian; and others

    2014-01-01

    In early 2011, a dialogue was initiated within the Board of Directors (BOD) of the American Society for Radiation Oncology (ASTRO) regarding the future of the basic sciences of the specialty, primarily focused on the current state and potential future direction of basic research within radiation oncology. After consideration of the complexity of the issues involved and the precise nature of the undertaking, in August 2011, the BOD empanelled a Cancer Biology/Radiation Biology Task Force (TF). The TF was charged with developing an accurate snapshot of the current state of basic (preclinical) research in radiation oncology from the perspective of relevance to the modern clinical practice of radiation oncology as well as the education of our trainees and attending physicians in the biological sciences. The TF was further charged with making suggestions as to critical areas of biological basic research investigation that might be most likely to maintain and build further the scientific foundation and vitality of radiation oncology as an independent and vibrant medical specialty. It was not within the scope of service of the TF to consider the quality of ongoing research efforts within the broader radiation oncology space, to presume to consider their future potential, or to discourage in any way the investigators committed to areas of interest other than those targeted. The TF charge specifically precluded consideration of research issues related to technology, physics, or clinical investigations. This document represents an Executive Summary of the Task Force report.

  19. Current status and recommendations for the future of research, teaching, and testing in the biological sciences of radiation oncology: report of the American Society for Radiation Oncology Cancer Biology/Radiation Biology Task Force, executive summary.

    PubMed

    Wallner, Paul E; Anscher, Mitchell S; Barker, Christopher A; Bassetti, Michael; Bristow, Robert G; Cha, Yong I; Dicker, Adam P; Formenti, Silvia C; Graves, Edward E; Hahn, Stephen M; Hei, Tom K; Kimmelman, Alec C; Kirsch, David G; Kozak, Kevin R; Lawrence, Theodore S; Marples, Brian; McBride, William H; Mikkelsen, Ross B; Park, Catherine C; Weidhaas, Joanne B; Zietman, Anthony L; Steinberg, Michael

    2014-01-01

    In early 2011, a dialogue was initiated within the Board of Directors (BOD) of the American Society for Radiation Oncology (ASTRO) regarding the future of the basic sciences of the specialty, primarily focused on the current state and potential future direction of basic research within radiation oncology. After consideration of the complexity of the issues involved and the precise nature of the undertaking, in August 2011, the BOD empanelled a Cancer Biology/Radiation Biology Task Force (TF). The TF was charged with developing an accurate snapshot of the current state of basic (preclinical) research in radiation oncology from the perspective of relevance to the modern clinical practice of radiation oncology as well as the education of our trainees and attending physicians in the biological sciences. The TF was further charged with making suggestions as to critical areas of biological basic research investigation that might be most likely to maintain and build further the scientific foundation and vitality of radiation oncology as an independent and vibrant medical specialty. It was not within the scope of service of the TF to consider the quality of ongoing research efforts within the broader radiation oncology space, to presume to consider their future potential, or to discourage in any way the investigators committed to areas of interest other than those targeted. The TF charge specifically precluded consideration of research issues related to technology, physics, or clinical investigations. This document represents an Executive Summary of the Task Force report.

  20. Phase Competition and Magnetotransport Phenomena in Manganite Films and Mesoscopic Structures

    NASA Astrophysics Data System (ADS)

    Wu, Tom

    2006-03-01

    The importance of competition between ferromagnetic metallic (FMM) and charge-ordered insulating (COI) phases in the physics of bulk manganites has been established through a wide variety of techniques. One exotic consequence of this phase competition is step-like features in magnetotransport observed in bulk and single-crystals of Pr0.65(CaySr1-y)0.35MnO3 (PCSMO) with 0.7<=y<=0.8. The length-scale of the phase coexistence is ˜1 micron, motivating a study of structures with dimensions similar to this natural length scale where phenomenology distinct from that of bulk counterparts is expected. Toward that end, we have synthesized films and laterally confined mesoscopic bridges of PCSMO and studied their magnetotransport properties. In particular, we observed: (1) Intrinsic ultrasharp magnetization steps below 5 K in both bulk and film samples and their dependence on the extrinsic measurement protocols; (2) Spontaneous jumps of resistance during both the ramping of magnetic field and the relaxation after the field cycle; (3) I-V curves exhibiting negative differential resistance (NDR) in certain ranges of temperature and magnetic field. All of these phenomena can be explained in the context of interconversion between the COI phase and the FMM phase. As expected, this interconversion can be triggered by external magnetic field, as found in the case of the magnetization and resistance steps. Alternatively, in the mesoscopic structures with dimensions similar to the size of the competing FMM and COI domains, a local Joule heating-induced annihilation of conducting filaments causes the anomalous NDR.

  1. Localization and elasticity in entangled polymer liquids as a mesoscopic glass transition

    NASA Astrophysics Data System (ADS)

    Schweizer, Kenneth

    2010-03-01

    The reptation-tube model is widely viewed as the correct zeroth order model for entangled linear polymer dynamics under quiescent conditions. Its key ansatz is the existence of a mesoscopic dynamical length scale that prohibits transverse chain motion beyond a tube diameter of order 3-10 nm. However, the theory is phenomenological and lacks a microscopic foundation, and many fundamental questions remain unanswered. These include: (i) where does the confining tube field come from and can it be derived from statistical mechanics? (ii) what is the microscopic origin of the magnitude, and power law scaling with concentration and packing length, of the plateau shear modulus? (iii) is the tube diameter time-dependent? (iv) does the confinement field contribute to elasticity ? (v) do entanglement constraints have a finite strength? Building on our new force-level theories for the dynamical crossover and activated barrier hopping in glassy colloidal suspensions and polymer melts, a first principles self-consistent theory has been developed for entangled polymers. Its basic physical elements, and initial results that address the questions posed above, will be presented. The key idea is that beyond a critical degree of polymerization, the chain connectivity and excluded volume induced intermolecular correlation hole drives temporary localization on an intermediate length scale resulting in a mesoscopic ``ideal kinetic glass transition.'' Large scale isotropic motion is effectively quenched due to the emergence of chain length dependent entropic barriers. However, the barrier height is not infinite, resulting in softening of harmonic localization at large displacements, temporal increase of the confining length scale, and a finite strength of entanglement constraints which can be destroyed by applied stress.

  2. Fractionally distilled SRC-I, SRC-II, EDS, H-Coal and ITSL direct coal liquefaction process materials: a comparative summary of chemical analysis and biological testing

    SciTech Connect

    Wright, C.W.; Later, D.W.; Dauble, D.D.; Wilson, B.W.

    1985-07-01

    This document reports and compares the results compiled from chemical analyses and biological testing of coal liquefaction process materials which were fractionally distilled, after production, into various comparable boiling-point range cuts. Comparative analyses were performed on solvent refined coal (SRC)-I, SRC-II, H-Coal, EDS an integrated two-stage liquefaction (ITSL) distillate materials. Mutagenicity and carcinogenicity assays were conducted in conjunction with chromatographic and mass spectrometric analyses to provide detailed, comparative, chemical and biological assessments. Where possible, results obtained from the distillate cuts are compared to those from coal liquefaction materials with limited boiling ranges. Work reported here was conducted by investigators in the Biology and Chemistry Department at the Pacific Northwest Laboratory (PNL), Richland, WA. 38 refs., 16 figs., 27 tabs.

  3. Decommissioning samples from the Ft. Lewis, WA, solvent refined coal pilot plant: chemical analysis and biological testing

    SciTech Connect

    Weimer, W.C.; Wright, C.W.

    1985-10-01

    This report presents the results from chemical analyses and limited biological assays of three sets of samples from the Ft. Lewis, WA solvent refined coal (SRC) pilot plant. The samples were collected during the process of decommissioning this facility. Chemical composition was determined for chemical class fractions of the samples by using high-resolution gas chromatography (GC), high-resolution GC/mass spectrometry (MS) and high-resolution MS. Biological activity was measuring using both the histidine reversion microbial mutagenicity assay with Salmonella typhimurium, TA98 and an initiation/promotion mouse-skin tumorigenicity assay. 19 refs., 7 figs., 27 tabs.

  4. Core-shell heterostructured metal oxide arrays enable superior light-harvesting and hysteresis-free mesoscopic perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Mahmood, Khalid; Swain, Bhabani Sankar; Amassian, Aram

    2015-07-01

    To achieve highly efficient mesoscopic perovskite solar cells (PSCs), the structure and properties of an electron transport layer (ETL) or material (ETM) have been shown to be of supreme importance. Particularly, the core-shell heterostructured mesoscopic ETM architecture has been recognized as a successful electrode design, because of its large internal surface area, superior light-harvesting efficiency and its ability to achieve fast charge transport. Here we report the successful fabrication of a hysteresis-free, 15.3% efficient PSC using vertically aligned ZnO nanorod/TiO2 shell (ZNR/TS) core-shell heterostructured ETMs for the first time. We have also added a conjugated polyelectrolyte polymer into the growth solution to promote the growth of high aspect ratio (AR) ZNRs and substantially improve the infiltration of the perovskite light absorber into the ETM. The PSCs based on the as-synthesized core-shell ZnO/TiO2 heterostructured ETMs exhibited excellent performance enhancement credited to the superior light harvesting capability, larger surface area, prolonged charge-transport pathways and lower recombination rate. The unique ETM design together with minimal hysteresis introduces core-shell ZnO/TiO2 heterostructures as a promising mesoscopic electrode approach for the fabrication of efficient PSCs.To achieve highly efficient mesoscopic perovskite solar cells (PSCs), the structure and properties of an electron transport layer (ETL) or material (ETM) have been shown to be of supreme importance. Particularly, the core-shell heterostructured mesoscopic ETM architecture has been recognized as a successful electrode design, because of its large internal surface area, superior light-harvesting efficiency and its ability to achieve fast charge transport. Here we report the successful fabrication of a hysteresis-free, 15.3% efficient PSC using vertically aligned ZnO nanorod/TiO2 shell (ZNR/TS) core-shell heterostructured ETMs for the first time. We have also added a

  5. Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode

    PubMed Central

    Ku, Zhiliang; Rong, Yaoguang; Xu, Mi; Liu, Tongfa; Han, Hongwei

    2013-01-01

    A mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 heterojunction solar cell is developed with low-cost carbon counter electrode (CE) and full printable process. With carbon black/spheroidal graphite CE, this mesoscopic heterojunction solar cell presents high stability and power conversion efficiency of 6.64%, which is higher than that of the flaky graphite based device and comparable to the conventional Au version. PMID:24185501

  6. Testing Models: A Key Aspect to Promote Teaching Activities Related to Models and Modelling in Biology Lessons?

    ERIC Educational Resources Information Center

    Krell, Moritz; Krüger, Dirk

    2016-01-01

    This study investigated biology teachers' (N = 148) understanding of models and modelling (MoMo), their model-related teaching activities and relations between the two. A framework which distinguishes five aspects of MoMo in science ("nature of models," "multiple models," "purpose of models," "testing…

  7. Otoconia as test masses in biological accelerometers: what can we learn about their formation from evolutionary studies and from work in microgravity?

    NASA Technical Reports Server (NTRS)

    Ross, M. D.; Donovan, K. M.

    1986-01-01

    This paper reviews previous findings and introduces new material about otolith end organs that help us to understand their functioning and development. In particular, we consider the end organs as biological accelerometers. The otoconia are dealt with as test masses whose substructure and evolutionary trend toward calcite may prove significant in understanding formation requirements. Space-flight helps illuminate the influence of gravity, while right-left asymmetry is suggested by study of certain rat strains.

  8. Concepts and Tests for the Remote-Controlled Dismantling of the Biological Shield and Form work of the KNK Reactor - 13425

    SciTech Connect

    Neff, Sylvia; Graf, Anja; Petrick, Holger; Rothschmitt, Stefan; Klute, Stefan

    2013-07-01

    The compact sodium-cooled nuclear reactor facility Karlsruhe (KNK), a prototype Fast Breeder, is currently in an advanced stage of dismantling. Complete dismantling is based on 10 partial licensing steps. In the frame of the 9. decommissioning permit, which is currently ongoing, the dismantling of the biological shield is foreseen. The biological shield consists of heavy reinforced concrete with built-in steel fitments, such as form-work of the reactor tank, pipe sleeves, ventilation channels, and measuring devices. Due to the activation of the inner part of the biological shield, dismantling has to be done remote-controlled. During a comprehensive basic design phase a practical dismantling strategy was developed. Necessary equipment and tools were defined. Preliminary tests revealed that hot wire plasma cutting is the most favorable cutting technology due to the geometrical boundary conditions, the varying distance between cutter and material, and the heavy concrete behind the steel form-work. The cutting devices will be operated remotely via a carrier system with an industrial manipulator. The carrier system has expandable claws to adjust to the varying diameter of the reactor shaft during dismantling progress. For design approval of this prototype development, interaction between manipulator and hot wire plasma cutting was tested in a real configuration. For the demolition of the concrete structure, an excavator with appropriate tools, such as a hydraulic hammer, was selected. Other mechanical cutting devices, such as a grinder or rope saw, were eliminated because of concrete containing steel spheres added to increase the shielding factor of the heavy concrete. Dismantling of the biological shield will be done in a ring-wise manner due to static reasons. During the demolition process, the excavator is positioned on its tripod in three concrete recesses made prior to the dismantling of the separate concrete rings. The excavator and the manipulator carrier system

  9. Nano-light-emitting-diodes based on InGaN mesoscopic structures for energy saving optoelectronics

    NASA Astrophysics Data System (ADS)

    Mikulics, M.; Winden, A.; Marso, M.; Moonshiram, A.; Lüth, H.; Grützmacher, D.; Hardtdegen, H.

    2016-07-01

    Vertically integrated III-nitride based nano-LEDs (light emitting diodes) were designed and fabricated for operation in the telecommunication wavelength range in the (p-GaN/InGaN/n-GaN/sapphire) material system. The band edge luminescence energy of the nano-LEDs could be engineered by tuning the composition and size of the InGaN mesoscopic structures. Narrow band edge photoluminescence and electroluminescence were observed. Our mesoscopic InGaN structures (depending on diameter) feature a very low power consumption in the range between 2 nW and 30 nW. The suitability of the technological process for the long-term operation of LEDs is demonstrated by reliability measurements. The optical and electrical characterization presented show strong potential for future low energy consumption optoelectronics.

  10. Influence of electron-electron interactions on pair tunneling through a mesoscopic N-S tunnel junction.

    NASA Astrophysics Data System (ADS)

    Huck, A. K.; Hekking, F. W. J.

    1997-03-01

    At low temperatures and voltages, smaller than the superconducting gap, transport through a normal metal - superconductor (N-S) tunnel barrier is due to tunneling of electrons in pairs. For a mesoscopic N-S tunnel junction, this process is very sensitive to quantum interference effects: pair tunneling is determined by particle-particle diffusion (Cooperon propagation) near the junction (F.W.J. Hekking, Yu.V. Nazarov, Phys. Rev. Lett. 70, 1625 (1993)). On the other hand it is well-known that electron-electron interactions in a disordered metal lead to significant corrections to particle-particle diffusion (Yu.N. Ovchinnikov, Sov. Phys. JETP 37, 366 (1973)). We explore the effect of the interplay between disorder and interactions on the subgap conductivity of a mesoscopic N-S tunnel junction.

  11. Efficiency of biological activator formulated material (BAFM) for volatile organic compounds removal--preliminary batch culture tests with activated sludge.

    PubMed

    Corre, Charline; Couriol, Catherine; Amrane, Abdeltif; Dumont, Eric; Andrès, Yves; Le Cloirec, Pierre

    2012-01-01

    During biological degradation, such as biofiltration of air loaded with volatile organic compounds, the pollutant is passed through a bed packed with a solid medium acting as a biofilm support. To improve microorganism nutritional equilibrium and hence to enhance the purification capacities, a Biological Activator Formulated Material (BAFM) was developed, which is a mixture of solid nutrients dissolving slowly in a liquid phase. This solid was previously validated on mineral pollutants: ammonia and hydrogen sulphide. To evaluate the efficiency of such a material for biodegradation of some organic compounds, a simple experiment using an activated sludge batch reactor was carried out. The pollutants (sodium benzoate, phenol, p-nitrophenol and 2-4-dichlorophenol) were in the concentration range 100 to 1200 mg L(-1). The positive impact of the formulated material was shown. The improvement of the degradation rates was in the range 10-30%. This was the consequence of the low dissolution of the nutrients incorporated during material formulation, followed by their consumption by the biomass, as shown for urea used as a nitrogen source. Owing to its twofold interest (mechanical resistance and nutritional supplementation), the Biological Activator Formulated Material seems to be a promising material. Its addition to organic or inorganic supports should be investigated to confirm its relevance for implementation in biofilters. PMID:22988627

  12. Periodic order and defects in Ni-based inverse opal-like crystals on the mesoscopic and atomic scale

    NASA Astrophysics Data System (ADS)

    Chumakova, A. V.; Valkovskiy, G. A.; Mistonov, A. A.; Dyadkin, V. A.; Grigoryeva, N. A.; Sapoletova, N. A.; Napolskii, K. S.; Eliseev, A. A.; Petukhov, A. V.; Grigoriev, S. V.

    2014-10-01

    The structure of inverse opal crystals based on nickel was probed on the mesoscopic and atomic levels by a set of complementary techniques such as scanning electron microscopy and synchrotron microradian and wide-angle diffraction. The microradian diffraction revealed the mesoscopic-scale face-centered-cubic (fcc) ordering of spherical voids in the inverse opal-like structure with unit cell dimension of 750±10nm. The diffuse scattering data were used to map defects in the fcc structure as a function of the number of layers in the Ni inverse opal-like structure. The average lateral size of mesoscopic domains is found to be independent of the number of layers. 3D reconstruction of the reciprocal space for the inverse opal crystals with different thickness provided an indirect study of original opal templates in a depth-resolved way. The microstructure and thermal response of the framework of the porous inverse opal crystal was examined using wide-angle powder x-ray diffraction. This artificial porous structure is built from nickel crystallites possessing stacking faults and dislocations peculiar for the nickel thin films.

  13. Mesoscopic aspects of root water uptake modeling - Hydraulic resistances and root geometry interpretations in plant transpiration analysis

    NASA Astrophysics Data System (ADS)

    Vogel, Tomas; Votrubova, Jana; Dusek, Jaromir; Dohnal, Michal

    2016-02-01

    In the context of soil water flow modeling, root water uptake is often evaluated based on water potential difference between the soil and the plant (the water potential gradient approach). Root water uptake rate is modulated by hydraulic resistance of both the root itself, and the soil in the root vicinity. The soil hydraulic resistance is a function of actual soil water content and can be assessed assuming radial axisymmetric water flow toward a single root (at the mesoscopic scale). In the present study, three approximate solutions of mesoscopic root water uptake - finite difference approximation, steady-state solution, and steady-rate solution - are examined regarding their ability to capture the pressure head variations in the root vicinity. Insignificance of their differences when implemented in the macroscopic soil water flow model is demonstrated using the critical root water uptake concept. Subsequently, macroscopic simulations of coupled soil water flow and root water uptake are presented for a forest site under temperate humid climate. Predicted soil water pressure heads and actual transpiration rates are compared with observed data. Scenario simulations illustrate uncertainties associated with estimates of root geometrical and hydraulic properties. Regarding the actual transpiration prediction, the correct characterization of active root system geometry and hydraulic properties seems far more important than the choice of a particular mesoscopic model.

  14. Circuit theory and full counting statistics of charge transfer through mesoscopic systems: A random-matrix approach

    NASA Astrophysics Data System (ADS)

    Duarte-Filho, G. C.; Macedo-Junior, A. F.; Macêdo, A. M. S.

    2007-08-01

    We introduce a random-matrix description of full counting statistics of charge transfer through a quantum mesoscopic system at finite temperature in the presence two nonideal contacts. Using the exact map between random-matrix theory and the supersymmetric nonlinear σ model, we demonstrate, via explicit calculations, that the saddle-point equation, derived by applying the variational principle to the supersymmetric action, can be cast in the form of the two-terminal version of Nazarov’s circuit theory, thus giving it the status of a controlled approximation. For the case in which the mesoscopic system is a quantum dot at zero temperature, this circuit theory has recently been shown [A. L. R. Barbosa and A. M. S. Macêdo, Phys. Rev. B 71, 235307 (2005)] to reproduce exactly the asymptotic semiclassical limit of the Poisson kernel in perfect agreement with a diagrammatic approach for averaging over the unitary group. We report applications of our formalism to the description of charge transfer through a quantum dot, a quantum chain, and a quantum wire. We also discuss the role of different symmetry classes (orthogonal, unitary, and symplectic) and show how to use known exact connections between the supersymmetric nonlinear σ model and random scattering matrix theories to perform both perturbative and nonperturbative calculations. We believe that our results will help unify the various approaches being currently used in mesoscopic physics of hybrid devices within a single physically sound and mathematically rigorous theoretical scheme.

  15. Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%

    NASA Astrophysics Data System (ADS)

    Kim, Hui-Seon; Lee, Chang-Ryul; Im, Jeong-Hyeok; Lee, Ki-Beom; Moehl, Thomas; Marchioro, Arianna; Moon, Soo-Jin; Humphry-Baker, Robin; Yum, Jun-Ho; Moser, Jacques E.; Grätzel, Michael; Park, Nam-Gyu

    2012-08-01

    We report on solid-state mesoscopic heterojunction solar cells employing nanoparticles (NPs) of methyl ammonium lead iodide (CH3NH3)PbI3 as light harvesters. The perovskite NPs were produced by reaction of methylammonium iodide with PbI2 and deposited onto a submicron-thick mesoscopic TiO2 film, whose pores were infiltrated with the hole-conductor spiro-MeOTAD. Illumination with standard AM-1.5 sunlight generated large photocurrents (JSC) exceeding 17 mA/cm2, an open circuit photovoltage (VOC) of 0.888 V and a fill factor (FF) of 0.62 yielding a power conversion efficiency (PCE) of 9.7%, the highest reported to date for such cells. Femto second laser studies combined with photo-induced absorption measurements showed charge separation to proceed via hole injection from the excited (CH3NH3)PbI3 NPs into the spiro-MeOTAD followed by electron transfer to the mesoscopic TiO2 film. The use of a solid hole conductor dramatically improved the device stability compared to (CH3NH3)PbI3 -sensitized liquid junction cells.

  16. Testing for HIV

    MedlinePlus

    ... Medical Devices Radiation-Emitting Products Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco Products Vaccines, Blood & Biologics Home Vaccines, Blood & Biologics Safety & Availability (Biologics) HIV Home Test Kits Testing for HIV Share Tweet Linkedin Pin it More ...

  17. Analytical theory of mesoscopic Bose-Einstein condensation in an ideal gas

    SciTech Connect

    Kocharovsky, Vitaly V.; Kocharovsky, Vladimir V.

    2010-03-15

    We find the universal structure and scaling of the Bose-Einstein condensation (BEC) statistics and thermodynamics (Gibbs free energy, average energy, heat capacity) for a mesoscopic canonical-ensemble ideal gas in a trap with an arbitrary number of atoms, any volume, and any temperature, including the whole critical region. We identify a universal constraint-cutoff mechanism that makes BEC fluctuations strongly non-Gaussian and is responsible for all unusual critical phenomena of the BEC phase transition in the ideal gas. The main result is an analytical solution to the problem of critical phenomena. It is derived by, first, calculating analytically the universal probability distribution of the noncondensate occupation, or a Landau function, and then using it for the analytical calculation of the universal functions for the particular physical quantities via the exact formulas which express the constraint-cutoff mechanism. We find asymptotics of that analytical solution as well as its simple analytical approximations which describe the universal structure of the critical region in terms of the parabolic cylinder or confluent hypergeometric functions. The obtained results for the order parameter, all higher-order moments of BEC fluctuations, and thermodynamic quantities perfectly match the known asymptotics outside the critical region for both low and high temperature limits. We suggest two- and three-level trap models of BEC and find their exact solutions in terms of the cutoff negative binomial distribution (which tends to the cutoff gamma distribution in the continuous limit) and the confluent hypergeometric distribution, respectively. Also, we present an exactly solvable cutoff Gaussian model of BEC in a degenerate interacting gas. All these exact solutions confirm the universality and constraint-cutoff origin of the strongly non-Gaussian BEC statistics. We introduce a regular refinement scheme for the condensate statistics approximations on the basis of the

  18. Two-stage coal liquefaction process materials from the Wilsonville Facility operated in the nonintegrated and integrated modes: chemical analyses and biological testing

    SciTech Connect

    Later, D.W.

    1985-01-01

    This document reports the results from chemical analyses and biological testing of process materials sampled during operation of the Wilsonville Advanced Coal Liquefaction Research and Development Facility (Wilsonville, Alabama) in both the noncoupled or nonintegrated (NTSL Run 241) and coupled or integrated (ITSL Run 242) two-stage liquefaction operating modes. Mutagenicity and carcinogenicity assays were conducted in conjunction with chromatographic and mass spectrometric analyses to provide detailed, comparative chemical and biological assessments of several NTSL and ITSL process materials. In general, the NTSL process materials were biologically more active and chemically more refractory than analogous ITSL process materials. To provide perspective, the NTSL and ITSL results are compared with those from similar testing and analyses of other direct coal liquefaction materials from the solvent refined coal (SRC) I, SRC II and EDS processes. Comparisons are also made between two-stage coal liquefaction materials from the Wilsonville pilot plant and the C.E. Lummus PDU-ITSL Facility in an effort to assess scale-up effects in these two similar processes. 36 references, 26 figures, 37 tables.

  19. Non-invasive tests in animal models and humans: a new paradigm for assessing efficacy of biologics including prebiotics and probiotics.

    PubMed

    Butler, R N

    2008-01-01

    Newer biological agents that are designed to have multiple effects on a host require better ways to determine both their safety and toxicity. Indeed ecologically potent factors such as agents that can alter the gut milieu and change host responses are now being realized as a viable alternative to more focused pharmaceuticals. Even in the pharmaceutical arena there is a growing awareness of the preventative and therapeutic potential of alternative agents. Probiotics and prebiotics amongst other agents fall into this category and can have both direct and indirect effects on the pathogenesis and progress of disease. This review details some of the new approaches using non-invasive tests to enable firstly a better definition of a stressed through to a damaged gastrointestinal mucosa. They constitute ways to apply dynamic function testing in animal models and humans to provide reference points to which other measurements can be related e.g. altered circulating cytokines, altered gene expression. As such this phenotypic scaffold, alone and combined with newer molecular parameters, will improve our understanding of the interaction of luminal factors within the alimentary tract and the impact that these have on physiologically challenged mucosa and in disease both at the gastrointestinal level and also in remote organs. Practically, the dynamic function tests, primarily breath tests, can now be used as diagnostic and prognostic indicators of the efficacy of new biologics such as probiotics and prebiotics that in part elicit their effects by altering the ecology of particular regions of the intestine. PMID:18537657

  20. The use of mathematical modeling and pilot plant testing to develop a new biological phosphorus and nitrogen removal process

    SciTech Connect

    Nolasco, D.A.; Daigger, G.T.; Stafford, D.R.; Kaupp, D.M.; Stephenson, J.P.

    1998-09-01

    A mechanistic mathematical model for carbon oxidation, nitrogen removal, and enhanced biological phosphorus removal was used to develop the Step Bio-P process, a new biological phosphorus and nitrogen removal process with a step-feed configuration. A 9,000-L pilot plant with diurnally varying influent process loading rates was operated to verify the model results and to optimize the Step Bio-P process for application at the lethbridge, Alberta, Canada, wastewater treatment plant. The pilot plant was operated for 10 months. An automatic on-line data acquisition system with multiple sampling and metering points for dissolved oxygen, mixed liquor suspended solids, ammonia-nitrogen, nitrate-nitrogen, ortho-phosphate, and flow rates was used. A sampling program to obtain off-line data was carried out to verify the information from the on-line system and monitor additional parameters. The on-line and off-line data were used to recalibrate the model, which was used as an experimental design and process optimization tool.

  1. Simplified pulse reactor for real-time long-term in vitro testing of biological heart valves.

    PubMed

    Schleicher, Martina; Sammler, Günther; Schmauder, Michael; Fritze, Olaf; Huber, Agnes J; Schenke-Layland, Katja; Ditze, Günter; Stock, Ulrich A

    2010-05-01

    Long-term function of biological heart valve prostheses (BHV) is limited by structural deterioration leading to failure with associated arterial hypertension. The objective of this work was development of an easy to handle real-time pulse reactor for evaluation of biological and tissue engineered heart valves under different pressures and long-term conditions. The pulse reactor was made of medical grade materials for placement in a 37 degrees C incubator. Heart valves were mounted in a housing disc moving horizontally in culture medium within a cylindrical culture reservoir. The microprocessor-controlled system was driven by pressure resulting in a cardiac-like cycle enabling competent opening and closing of the leaflets with adjustable pulse rates and pressures between 0.25 to 2 Hz and up to 180/80 mmHg, respectively. A custom-made imaging system with an integrated high-speed camera and image processing software allow calculation of effective orifice areas during cardiac cycle. This simple pulse reactor design allows reproducible generation of patient-like pressure conditions and data collection during long-term experiments.

  2. A versatile system for biological and soil chemical tests on a planetary landing craft. II - Hardware development

    NASA Technical Reports Server (NTRS)

    Martin, J. P.; Kok, B.; Radmer, R.

    1976-01-01

    A system has been under development which is designed to seek remotely for clues to life in planetary soil samples. The basic approach is a set of experiments, all having a common sensor, a gas analysis mass spectrometer which monitors gas composition in the head spaces above sealed, temperature controlled soil samples. Versatility is obtained with up to three preloaded, sealed fluid injector capsules for each of eleven soil test cells. Tests results with an engineering model has demonstrated performance capability of subsystem components such as soil distribution, gas sampling valves, injector mechanisms, temperature control, and test cell seal.

  3. Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

    NASA Astrophysics Data System (ADS)

    Magee, N. B.; Miller, A.; Amaral, M.; Cumiskey, A.

    2014-11-01

    Here we show high-magnification images of hexagonal ice crystals acquired by environmental scanning electron microscopy (ESEM). Most ice crystals were grown and sublimated in the water vapor environment of an FEI-Quanta-200 ESEM, but crystals grown in a laboratory diffusion chamber were also transferred intact and imaged via ESEM. All of these images display prominent mesoscopic topography including linear striations, ridges, islands, steps, peaks, pits, and crevasses; the roughness is not observed to be confined to prism facets. The observations represent the most highly magnified images of ice surfaces yet reported and expand the range of conditions in which rough surface features are known to be conspicuous. Microscale surface topography is seen to be ubiquitously present at temperatures ranging from -10 °C to -40 °C, in supersaturated and subsaturated conditions, on all crystal facets, and irrespective of substrate. Despite the constant presence of surface roughness, the patterns of roughness are observed to be dramatically different between growing and sublimating crystals, and transferred crystals also display qualitatively different patterns of roughness. Crystals are also demonstrated to sometimes exhibit inhibited growth in moderately supersaturated conditions following exposure to near-equilibrium conditions, a phenomenon interpreted as evidence of 2-D nucleation. New knowledge about the characteristics of these features could affect the fundamental understanding of ice surfaces and their physical parameterization in the context of satellite retrievals and cloud modeling. Links to supplemental videos of ice growth and sublimation are provided.

  4. Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

    NASA Astrophysics Data System (ADS)

    Magee, N. B.; Miller, A.; Amaral, M.; Cumiskey, A.

    2014-03-01

    Here we show high-magnification images of hexagonal ice crystals acquired by Environmental Scanning Electron Microscopy (ESEM). Most ice crystals were grown and sublimated in the water vapor environment of an FEI-Quanta-200 ESEM, but crystals grown in a laboratory diffusion chamber were also transferred intact and imaged via ESEM. All of these images display prominent mesoscopic topography including linear striations, ridges, islands, steps, peaks, pits, and crevasses; the roughness is not observed to be confined to prism facets. The observations represent the most highly magnified images of ice surfaces yet reported and expand the range of conditions where the rough surface features are known to be conspicuous. Microscale surface topography is seen to be ubiquitously present at temperatures ranging from -10 °C to -40 °C, at super-saturated and sub-saturated conditions, on all crystal facets, and irrespective of substrate. Despite the constant presence of surface roughness, the patterns of roughness are observed to be dramatically different between growing and sublimating crystals, and transferred crystals also display qualitatively different patterns of roughness. Crystals are also demonstrated to sometimes exhibit inhibited growth in moderately supersaturated conditions following exposure to near-equilibrium conditions, a phenomena interpreted as evidence of 2-D nucleation. New knowledge of the characteristics of these features could affect the fundamental understanding of ice surfaces and their physical parameterization in the context of satellite retrievals and cloud modeling. Links to Supplement videos of ice growth and sublimation are provided.

  5. Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors.

    PubMed

    Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V

    2015-07-03

    The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm(2) cross-section. The impurities suppress superconductivity in a three-dimensional 'Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities.

  6. Interaction of Heparins and Dextran Sulfates with a Mesoscopic Protein Nanopore

    PubMed Central

    Teixeira, Luciana R.; Merzlyak, Petr G.; Valeva, Angela; Krasilnikov, Oleg V.

    2009-01-01

    Abstract A mechanism of how polyanions influence the channel formed by Staphylococcus aureus α-hemolysin is described. We demonstrate that the probability of several types of polyanions to block the ion channel depends on the presence of divalent cations and the polyanion molecular weight and concentration. For heparins, a 10-fold increase in molecular weight decreases the half-maximal inhibitory concentration, IC50, nearly 104-fold. Dextran sulfates were less effective at blocking the channel. The polyanions are significantly more effective at reducing the conductance when added to the trans side of this channel. Lastly, the effectiveness of heparins on the channel conductance correlated with their influence on the ζ-potential of liposomes. A model that includes the binding of polyanions to the channel-membrane complex via Ca2+-bridges and the asymmetry of the channel structure describes the data adequately. Analysis of the single channel current noise of wild-type and site-directed mutant versions of α-hemolysin channels suggests that a single polyanion enters the pore due to electrostatic forces and physically blocks the ion conduction path. The results might be of interest for pharmacology, biomedicine, and research aiming to design mesoscopic pore blockers. PMID:19948118

  7. Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J.; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F.; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V.

    2015-07-01

    The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm2 cross-section. The impurities suppress superconductivity in a three-dimensional `Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ~1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities.

  8. Redox entropy of plastocyanin: Developing a microscopic view of mesoscopic polar solvation

    NASA Astrophysics Data System (ADS)

    LeBard, David N.; Matyushov, Dmitry V.

    2008-04-01

    We report applications of analytical formalisms and molecular dynamics (MD) simulations to the calculation of redox entropy of plastocyanin metalloprotein in aqueous solution. The goal of our analysis is to establish critical components of the theory required to describe polar solvation at the mesoscopic scale. The analytical techniques include a microscopic formalism based on structure factors of the solvent dipolar orientations and density and continuum dielectric theories. The microscopic theory employs the atomistic structure of the protein with force-field atomic charges and solvent structure factors obtained from separate MD simulations of the homogeneous solvent. The MD simulations provide linear response solvation free energies and reorganization energies of electron transfer in the temperature range of 280-310K. We found that continuum models universally underestimate solvation entropies, and a more favorable agreement is reported between the microscopic calculations and MD simulations. The analysis of simulations also suggests that difficulties of extending standard formalisms to protein solvation are related to the inhomogeneous structure of the solvation shell at the protein-water interface combining islands of highly structured water around ionized residues along with partial dewetting of hydrophobic patches. Quantitative theories of electrostatic protein hydration need to incorporate realistic density profile of water at the protein-water interface.

  9. Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films.

    PubMed

    Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

    2016-02-25

    Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions.

  10. Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

    PubMed Central

    Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

    2016-01-01

    Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions. PMID:26911529

  11. Reading valley-hybridization and universal symmetry of graphene with mesoscopic conductance fluctuations

    NASA Astrophysics Data System (ADS)

    Kochat, Vidya; Pal, Atindra Nath; Ghosh, Arindam

    2014-03-01

    In graphene, the K and K' valleys act as spin-like entities, and can form the basis of valley-based electronics, having applications ranging from valley-based quantum computation, to valley filters or polarizers. The valleys hybridize to form new quantum states, such as the valley singlet and triplets, that lead to anti-localized quantum transport, non-locality and flavour Hall effect. Here we demonstrate a direct route for reading and manipulating the valley coherent states of disordered graphene by measuring the mesoscopic conductance fluctuations. We observe that the conductance fluctuations in graphene at low temperatures are reduced by a factor of four at high carrier densities, due to the gapping out of valley triplet states by short-range disorder. We also show that this results in a gate-tunable universal symmetry class, which is yet another unique and fundamental feature of the 2D honeycomb lattice of graphene. We acknowledge the Department of Science and Technology (DST) for a funded project. A. N. P. and V. K. thank CSIR for financial support.

  12. Mesoscopic hydrogel molding to control the 3D geometry of bioartificial muscle tissues

    PubMed Central

    Bian, Weining; Liau, Brian; Badie, Nima

    2010-01-01

    This protocol describes a cell/hydrogel molding method for precise and reproducible biomimetic fabrication of three-dimensional (3D) muscle tissue architectures in vitro. Using a high aspect ratio soft lithography technique, we fabricate polydimethylsiloxane (PDMS) molds containing arrays of mesoscopic posts with defined size, elongation and spacing. On cell/hydrogel molding, these posts serve to enhance the diffusion of nutrients to cells by introducing elliptical pores in the cell-laden hydrogels and to guide local 3D cell alignment by governing the spatial pattern of mechanical tension. Instead of ultraviolet or chemical cross-linking, this method utilizes natural hydrogel polymerization and topographically constrained cell-mediated gel compaction to create the desired 3D tissue structures. We apply this method to fabricate several square centimeter large, few hundred micron-thick bioartificial muscle tissues composed of viable, dense, uniformly aligned and highly differentiated cardiac or skeletal muscle fibers. The protocol takes 4–5 d to fabricate PDMS molds followed by 2 weeks of cell culture. PMID:19798085

  13. Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors

    PubMed Central

    Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J.; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F.; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V.

    2015-01-01

    The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm2 cross-section. The impurities suppress superconductivity in a three-dimensional ‘Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities. PMID:26139568

  14. Mesoscopic simulation of phase behaviors and structures in an amphiphile-solvent system.

    PubMed

    Yamada, Kohtaro; Yasuno, Emiko; Kawabata, Youhei; Okuzono, Tohru; Kato, Tadashi

    2014-06-01

    We have performed a three-dimensional simulation of mesoscopic structures in a mixture of AB amphiphilic molecule and C solvent by employing the density-functional theory under the conditions that (i) the size of the AB is much larger than C and (ii) the affinity between A and B is much larger than the affinity between B and C. First, we have calculated the free energy of five periodic structures, i.e., the lamellar phase, hexagonally packed cylinders, body-centered-cubic spheres, face-centered-cubic spheres, and gyroid phase for different sets of the concentration of AB (ϕ[over ¯]_{AB}) and the χ parameter (χ_{AC}). By comparing the free energies for these structures, the χ_{AC}-ϕ[over ¯]_{AB} phase diagram has been obtained. In addition to these periodic structures, it has been shown that nonperiodic structures such as spherical and rodlike micelles can be obtained although they might be metastable phase. PMID:25019779

  15. High-throughput automated home-cage mesoscopic functional imaging of mouse cortex

    PubMed Central

    Murphy, Timothy H.; Boyd, Jamie D.; Bolaños, Federico; Vanni, Matthieu P.; Silasi, Gergely; Haupt, Dirk; LeDue, Jeff M.

    2016-01-01

    Mouse head-fixed behaviour coupled with functional imaging has become a powerful technique in rodent systems neuroscience. However, training mice can be time consuming and is potentially stressful for animals. Here we report a fully automated, open source, self-initiated head-fixation system for mesoscopic functional imaging in mice. The system supports five mice at a time and requires minimal investigator intervention. Using genetically encoded calcium indicator transgenic mice, we longitudinally monitor cortical functional connectivity up to 24 h per day in >7,000 self-initiated and unsupervised imaging sessions up to 90 days. The procedure provides robust assessment of functional cortical maps on the basis of both spontaneous activity and brief sensory stimuli such as light flashes. The approach is scalable to a number of remotely controlled cages that can be assessed within the controlled conditions of dedicated animal facilities. We anticipate that home-cage brain imaging will permit flexible and chronic assessment of mesoscale cortical function. PMID:27291514

  16. Unconventional superconductivity at mesoscopic point contacts on the 3D Dirac semimetal Cd3As2.

    PubMed

    Aggarwal, Leena; Gaurav, Abhishek; Thakur, Gohil S; Haque, Zeba; Ganguli, Ashok K; Sheet, Goutam

    2016-01-01

    Three-dimensional (3D) Dirac semimetals exist close to topological phase boundaries which, in principle, should make it possible to drive them into exotic new phases, such as topological superconductivity, by breaking certain symmetries. A practical realization of this idea has, however, hitherto been lacking. Here we show that the mesoscopic point contacts between pure silver (Ag) and the 3D Dirac semimetal Cd3As2 (ref. ) exhibit unconventional superconductivity with a critical temperature (onset) greater than 6 K whereas neither Cd3As2 nor Ag are superconductors. A gap amplitude of 6.5 meV is measured spectroscopically in this phase that varies weakly with temperature and survives up to a remarkably high temperature of 13 K, indicating the presence of a robust normal-state pseudogap. The observations indicate the emergence of a new unconventional superconducting phase that exists in a quantum mechanically confined region under a point contact between a Dirac semimetal and a normal metal.

  17. Direct observation of mesoscopic phase separation in KxFeySe2 by scanning microwave microscopy

    NASA Astrophysics Data System (ADS)

    Maeda, Atsutaka; Takahashi, Hideyuki; Imai, Yoshinori

    2015-03-01

    KxFeySe2 is isostructural to 122-FeAs compounds. However, its electronic structure is unique among Fe-based superconductors in the sense that hole Fermi pocket is absent at the center of the Brillouin zone. Therefore, it is important to study this compounds in terms of the mechanism of superconductivity since some pairing (for example, s +/- -wave) needs the interaction between hole and electron Fermi pockets. However, the phase separation in this material makes studies using conventional macroscopic measurement techniques very difficult. Scanning near-field microwave microscope (SMM), which can measure local electric property of inhomogeneous conducting samples, should be a powerful tool. Recently we developed the combined instrument of STM and SMM with high sensitivity, and investigated the local electric property of KxFeySe2 (x = 0.8, y = 1.6 ~2, Tc = 31 K) using this scanning tunneling/microwave microscope. The characteristic pattern of mesoscopic phase separation of the metallic and the semiconducting phase was observed. From the comparison with previously reported SEM/EDS result we identified the metallic phase and the semiconducting phase as the minor Fe-rich phase and the major K2Fe4Se5 phase, respectively.

  18. Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors.

    PubMed

    Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V

    2015-01-01

    The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm(2) cross-section. The impurities suppress superconductivity in a three-dimensional 'Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities. PMID:26139568

  19. Reprint of : Scattering theory approach to bosonization of non-equilibrium mesoscopic systems

    NASA Astrophysics Data System (ADS)

    Sukhorukov, Eugene V.

    2016-08-01

    Between many prominent contributions of Markus Büttiker to mesoscopic physics, the scattering theory approach to the electron transport and noise stands out for its elegance, simplicity, universality, and popularity between theorists working in this field. It offers an efficient way to theoretically investigate open electron systems far from equilibrium. However, this method is limited to situations where interactions between electrons can be ignored, or considered perturbatively. Fortunately, this is the case in a broad class of metallic systems, which are commonly described by the Fermi liquid theory. Yet, there exist another broad class of electron systems of reduced dimensionality, the so-called Tomonaga-Luttinger liquids, where interactions are effectively strong and cannot be neglected even at low energies. Nevertheless, strong interactions can be accounted exactly using the bosonization technique, which utilizes the free-bosonic character of collective excitations in these systems. In the present work, we use this fact in order to develop the scattering theory approach to the bosonization of open quasi-one dimensional electron systems far from equilibrium.

  20. Formation of mesoscopic metallic filaments in manganite thin films imaged by microwave impedance microscopy

    NASA Astrophysics Data System (ADS)

    Kundhikanjana, Worasom; Lai, Keji; Yang, Yongliang; Ma, Yue; Kelly, Michael; Shen, Zhi-Xun; Nakamura, Masao; Sheng, Zhigao; Kawasaki, Masashi; Tokura, Yoshi

    2012-02-01

    We study the ferromagnetic metallic domains from the charge-order insulating background at mesoscopic length scale in a Pr0.55Ca0.75Sr0.25MnO3 thin film using a variable temperature microwave impedance microscope (MIM). The metallic state in this compound can be easily induced at a moderate magnetic field as low as 2 T observed by both the transport and MIM. The temperature dependent transport under 1.2 T shows a large hysteresis loop. MIM allows us to observe the formation and melting of metallic domains at different temperatures during the cooling and warming processes. At higher temperatures, the metallic domains first emerge in small isolated filaments along certain crystal axes of the LSAT(110) substrate, suggesting that the local strain plays an important role. Surprisingly, small insulating islands remain in the metallic ground state and persist up to very high magnetic fields, indicating strong pining sites. Lastly, the sizes of the insulating islands at the ground state increase when the film is field cooled at lower speeds, suggesting s glassy order in this compound.

  1. Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces.

    PubMed

    Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Gama Goicochea, Armando

    2015-10-21

    The interfacial and structural properties of fluids confined by surfaces of different geometries are studied at the mesoscopic scale using dissipative particle dynamics simulations in the grand canonical ensemble. The structure of the surfaces is modeled by a simple function, which allows us to simulate readily different types of surfaces through the choice of three parameters only. The fluids we have modeled are confined either by two smooth surfaces or by symmetrically and asymmetrically structured walls. We calculate structural and thermodynamic properties such as the density, temperature and pressure profiles, as well as the interfacial tension profiles for each case and find that a structural order-disorder phase transition occurs as the degree of surface roughness increases. However, the magnitude of the interfacial tension is insensitive to the structuring of the surfaces and depends solely on the magnitude of the solid-fluid interaction. These results are important for modern nanotechnology applications, such as in the enhanced recovery of oil, and in the design of porous materials with specifically tailored properties.

  2. Parameterization of a mesoscopic model for the self-assembly of linear sodium alkyl sulfates

    NASA Astrophysics Data System (ADS)

    Mai, Zhaohuan; Couallier, Estelle; Rakib, Mohammed; Rousseau, Bernard

    2014-05-01

    A systematic approach to develop mesoscopic models for a series of linear anionic surfactants (CH3(CH2)n - 1OSO3Na, n = 6, 9, 12, 15) by dissipative particle dynamics (DPD) simulations is presented in this work. The four surfactants are represented by coarse-grained models composed of the same head group and different numbers of identical tail beads. The transferability of the DPD model over different surfactant systems is carefully checked by adjusting the repulsive interaction parameters and the rigidity of surfactant molecules, in order to reproduce key equilibrium properties of the aqueous micellar solutions observed experimentally, including critical micelle concentration (CMC) and average micelle aggregation number (Nag). We find that the chain length is a good index to optimize the parameters and evaluate the transferability of the DPD model. Our models qualitatively reproduce the essential properties of these surfactant analogues with a set of best-fit parameters. It is observed that the logarithm of the CMC value decreases linearly with the surfactant chain length, in agreement with Klevens' rule. With the best-fit and transferable set of parameters, we have been able to calculate the free energy contribution to micelle formation per methylene unit of -1.7 kJ/mol, very close to the experimentally reported value.

  3. Intact skull chronic windows for mesoscopic wide-field imaging in awake mice

    PubMed Central

    Silasi, Gergely; Xiao, Dongsheng; Vanni, Matthieu P.; Chen, Andrew C. N.; Murphy, Timothy H.

    2016-01-01

    Background Craniotomy-based window implants are commonly used for microscopic imaging, in head-fixed rodents, however their field of view is typically small and incompatible with mesoscopic functional mapping of cortex. New Method We describe a reproducible and simple procedure for chronic through-bone wide-field imaging in awake head-fixed mice providing stable optical access for chronic imaging over large areas of the cortex for months. Results The preparation is produced by applying clear-drying dental cement to the intact mouse skull, followed by a glass coverslip to create a partially transparent imaging surface. Surgery time takes about 30 minutes. A single set-screw provides a stable means of attachment for mesoscale assessment without obscuring the cortical field of view. Comparison with Existing Methods We demonstrate the utility of this method by showing seed-pixel functional connectivity maps generated from spontaneous cortical activity of GCAMP6 signals in both awake and anesthetized mice. Conclusions We propose that the intact skull preparation described here may be used for most longitudinal studies that do not require micron scale resolution and where cortical neural or vascular signals are recorded with intrinsic sensors. PMID:27102043

  4. On-chip terahertz spectroscopic techniques for measuring mesoscopic quantum systems.

    PubMed

    Wood, C D; Mistry, D; Li, L H; Cunningham, J E; Linfield, E H; Davies, A G

    2013-08-01

    We present the self-aligned fabrication of on-chip devices in which waveguides, incorporating integrated photoconductive switches, are combined with two-dimensional electron systems to allow probing of the ultrafast (terahertz frequency range) properties of confined semiconductor systems, both at cryogenic temperatures and in high magnetic fields. We demonstrate the direct injection of on-chip terahertz pulses into the mesoscopic system by femtosecond, near infra-red laser excitation of in-plane photoconductive switches formed on an epitaxially grown, low-temperature GaAs layer, which is integrated monolithically with a GaAs∕AlGaAs heterostructure containing a two-dimensional electron system. Both the input and output terahertz signals of an on-chip waveguide are sampled by altering dynamically the photoconductive excitation∕detection arrangement in situ on a single device. We also demonstrate a new method for sub-Kelvin excitation and detection of on-chip terahertz frequency radiation in a (3)He∕(4)He dilution refrigerator that allows the photocurrent and detected terahertz transient to be mapped as function of the near-infrared excitation position at the emitter and the detector, respectively. Furthermore, we demonstrate transmission of terahertz transients through a two-dimensional electron system in a coplanar waveguide under magnetic field at temperatures as low as 200 mK.

  5. Growth of monodisperse mesoscopic metal-oxide colloids under constant monomer supply.

    PubMed

    Nozawa, Koh; Delville, Marie-Hélène; Ushiki, Hideharu; Panizza, Pascal; Delville, Jean-Pierre

    2005-07-01

    In closed systems, control over the size of monodisperse metal-oxide colloids is generally limited to submicrometric dimensions. To overcome this difficulty, we explore the formation and growth of silica particles under constant monomer supply. The monomer source is externally driven by the progressive addition into the system of one of the precursors. Monodisperse spherical particles are produced up to a mesoscopic size. We analyze their growth versus the monomer addition rate at different temperatures. Our results show that in the presence of a continuous monomer addition, growth is limited by diffusion over the investigated temporal window. Using the temperature variation of the growth rate, we prove that rescaling leads to a data reduction onto a single master curve. Contrary to the growth process, the final particle's size reached after the end of the reagent supply strongly depends on the addition rate. The variation of the final particle size versus addition rate can be deduced from an analogy with crystal formation in jet precipitation. Within this framework, and using the temperature dependences of both the particle growth law and the final size, we determine the value of the molecular heat of dissolution associated to the silica solubility. These observations support the fact that classical theories of phase-ordering dynamics can be extended to the synthesis of inorganic particles. The emergence of a master behavior in the presence of continuous monomer addition also suggests the extension of these theories to open systems.

  6. Mesoscopic modeling of the response of human dental enamel to mid-infrared radiation

    NASA Astrophysics Data System (ADS)

    Vila Verde, Ana; Ramos, Marta; Stoneham, A. M.

    2006-03-01

    Ablation of human dental enamel, a composite biomaterial with water pores, is of significant importance in minimally invasive laser dentistry but progress in the area is hampered by the lack of optimal laser parameters. We use mesoscopic finite element models of this material to study its response to mid-infrared radiation. Our results indicate that the cost-effective, off-the-shelf CO2 laser at λ = 10.6 μm may in fact ablate enamel precisely, reproducibly and with limited unwanted side effects such as cracking or heating, provided that a pulse duration of 10 μs is used. Furthermore, our results also indicate that the Er:YAG laser (λ = 2.94 μm), currently popular for laser dentistry, may in fact cause unwanted deep cracking in the enamel when regions with unusually high water content are irradiated, and also provide an explanation for the large range of ablation threshold values observed for this material. The model may be easily adapted to study the response of any composite material to infrared radiation and thus may be useful for the scientific community.

  7. High Yield Synthesis of Mesoscopic Conductive and Dispersible Carbon Nanostructures via Ultrasonication of Commercial Precursors

    SciTech Connect

    Srivastava, Vikram K; Quinlan, Ronald; Agapov, Alexander L; Kisliuk, Alexander; Bhat, Gajanan; Mays, Jimmy

    2014-01-01

    The need to produce large quantities of graphenic materials displaying excellent conductivity, thermal resistance, and tunable properties for industrial applications has spurred interest in new techniques for exfoliating graphite. In this paper, sonication-assisted exfoliation of graphitic precursors in the presence of chloroform is shown to produce chemically and structurally unique exfoliated graphitic materials in high yields. These exfoliated graphites, referred to as mesographite and mesographene, respectively, exhibit unique properties which depend on the number of layers and exfoliation conditions. Structural characterization of mesographene reveals the presence of nanoscale two-dimensional graphene layers, and threedimensional carbon nanostructures sandwiched between layers, similar to those found in ball-milled and intercalated graphites. The conductivities of mesographite and mesographene are 2700 and 2000 S/m, respectively, indicating high conductivity despite flake damage. Optical absorption measurements of mesographite sonicated in various solvents showed significant changes in dispersion characteristics, and also indicated significant changes to mesoscopic colloidal behavior. A mechanism for functionalization and formation of capped carbon nanostructures is proposed by integrating the chemical and structural characterization in relation to the various carbon structures observed by electron microscopy. Composites based on common polymers were prepared by solution processing, and changes in thermal properties indicate improved dispersion of mesographite in polar polymers.

  8. Mesoscopic modeling of DNA denaturation rates: Sequence dependence and experimental comparison

    SciTech Connect

    Dahlen, Oda Erp, Titus S. van

    2015-06-21

    Using rare event simulation techniques, we calculated DNA denaturation rate constants for a range of sequences and temperatures for the Peyrard-Bishop-Dauxois (PBD) model with two different parameter sets. We studied a larger variety of sequences compared to previous studies that only consider DNA homopolymers and DNA sequences containing an equal amount of weak AT- and strong GC-base pairs. Our results show that, contrary to previous findings, an even distribution of the strong GC-base pairs does not always result in the fastest possible denaturation. In addition, we applied an adaptation of the PBD model to study hairpin denaturation for which experimental data are available. This is the first quantitative study in which dynamical results from the mesoscopic PBD model have been compared with experiments. Our results show that present parameterized models, although giving good results regarding thermodynamic properties, overestimate denaturation rates by orders of magnitude. We believe that our dynamical approach is, therefore, an important tool for verifying DNA models and for developing next generation models that have higher predictive power than present ones.

  9. Identify the diversity of mesoscopic structures in networks: A mixed random walk approach

    NASA Astrophysics Data System (ADS)

    Ma, Yifang; Jiang, Xin; Li, Meng; Shen, Xin; Guo, Quantong; Lei, Yanjun; Zheng, Zhiming

    2013-10-01

    Community or cluster structure, which can provide insight into the natural partitions and inner connections of a network, is a key feature in studying the mesoscopic structure of complex systems. Although numerous methods for community detection have been proposed ever since, there is still a lack of understanding on how to quantify the diversity of pre-divided community structures, or rank the roles of communities in participating in specific dynamic processes. Inspired by the Law of Mass Action in chemical kinetics, we introduce here the community random walk energy (CRWE), which reflects a potential based on the diffusion phase of a mixed random walk process taking place on the network, to identify the configuration of community structures. The difference of CRWE allows us to distinguish the intrinsic topological diversity between individual communities, on condition that all the communities are pre-arranged in the network. We illustrate our method by performing numerical simulations on constructive community networks and a real social network with distinct community structures. As an application, we apply our method to characterize the diversity of human genome communities, which provides a possible use of our method in inferring the genetic similarity between human populations.

  10. Four dimensional chaos and intermittency in a mesoscopic model of the electroencephalogram

    NASA Astrophysics Data System (ADS)

    Dafilis, Mathew P.; Frascoli, Federico; Cadusch, Peter J.; Liley, David T. J.

    2013-06-01

    The occurrence of so-called four dimensional chaos in dynamical systems represented by coupled, nonlinear, ordinary differential equations is rarely reported in the literature. In this paper, we present evidence that Liley's mesoscopic theory of the electroencephalogram (EEG), which has been used to describe brain activity in a variety of clinically relevant contexts, possesses a chaotic attractor with a Kaplan-Yorke dimension significantly larger than three. This accounts for simple, high order chaos for a physiologically admissible parameter set. Whilst the Lyapunov spectrum of the attractor has only one positive exponent, the contracting dimensions are such that the integer part of the Kaplan-Yorke dimension is three, thus giving rise to four dimensional chaos. A one-parameter bifurcation analysis with respect to the parameter corresponding to extracortical input is conducted, with results indicating that the origin of chaos is due to an inverse period doubling cascade. Hence, in the vicinity of the high order, strange attractor, the model is shown to display intermittent behavior, with random alternations between oscillatory and chaotic regimes. This phenomenon represents a possible dynamical justification of some of the typical features of clinically established EEG traces, which can arise in the case of burst suppression in anesthesia and epileptic encephalopathies in early infancy.

  11. On-chip terahertz spectroscopic techniques for measuring mesoscopic quantum systems.

    PubMed

    Wood, C D; Mistry, D; Li, L H; Cunningham, J E; Linfield, E H; Davies, A G

    2013-08-01

    We present the self-aligned fabrication of on-chip devices in which waveguides, incorporating integrated photoconductive switches, are combined with two-dimensional electron systems to allow probing of the ultrafast (terahertz frequency range) properties of confined semiconductor systems, both at cryogenic temperatures and in high magnetic fields. We demonstrate the direct injection of on-chip terahertz pulses into the mesoscopic system by femtosecond, near infra-red laser excitation of in-plane photoconductive switches formed on an epitaxially grown, low-temperature GaAs layer, which is integrated monolithically with a GaAs∕AlGaAs heterostructure containing a two-dimensional electron system. Both the input and output terahertz signals of an on-chip waveguide are sampled by altering dynamically the photoconductive excitation∕detection arrangement in situ on a single device. We also demonstrate a new method for sub-Kelvin excitation and detection of on-chip terahertz frequency radiation in a (3)He∕(4)He dilution refrigerator that allows the photocurrent and detected terahertz transient to be mapped as function of the near-infrared excitation position at the emitter and the detector, respectively. Furthermore, we demonstrate transmission of terahertz transients through a two-dimensional electron system in a coplanar waveguide under magnetic field at temperatures as low as 200 mK. PMID:24007101

  12. Short, intermediate and mesoscopic range order in sulfur-rich binary glasses

    SciTech Connect

    Bychkov, E.; Miloshova, M.; Price, D.L.; Benmore, C.J.; Lorriaux, A.

    2008-09-29

    Pulsed neutron and high-energy X-ray diffraction, small-angle neutron scattering, Raman spectroscopy and DSC were used to study structural changes on the short, intermediate and mesoscopic range scale for sulfur-rich AsS{sub x} (x {ge} 1.5) and GeS{sub x} (x {ge} 2) glasses. Two structural regions were found in the both systems. (1) Between stoichiometric (As{sub 2}S{sub 3} and GeS{sub 2}) and 'saturated' (AsS{sub 2.2} and GeS{sub 2.7}) compositions, excessive sulfur atoms form sulfur dimers and/or short chains, replacing bridging sulfur in corner-sharing AsS{sub 3/2} and GeS{sub 4/2} units. (2) Above the 'saturated' compositions at [As] < 30.5 at.% and [Ge] < 27 at.%, sulfur rings and longer sulfur chains (especially in the AsS{sub x} system) appear in the glass network. The glasses become phase separated with the domains of 20-50 {angstrom}, presumably enriched with sulfur rings. The longer chains Sn are not stable and crystallize to c-S{sub 8} on ageing of a few days to several months, depending on composition.

  13. Fabrication and characterization of large arrays of mesoscopic gold rings on large-aspect-ratio cantilevers

    NASA Astrophysics Data System (ADS)

    Ngo, D. Q.; Petković, I.; Lollo, A.; Castellanos-Beltran, M. A.; Harris, J. G. E.

    2014-10-01

    We have fabricated large arrays of mesoscopic metal rings on ultrasensitive cantilevers. The arrays are defined by electron beam lithography and contain up to 105 rings. The rings have a circumference of 1 μm, and are made of ultrapure (6N) Au that is deposited onto a silicon-on-insulator wafer without an adhesion layer. Subsequent processing of the SOI wafer results in each array being supported at the end of a free-standing cantilever. To accommodate the large arrays while maintaining a low spring constant, the cantilevers are nearly 1 mm in both lateral dimensions and 100 nm thick. The extreme aspect ratio of the cantilevers, the large array size, and the absence of a sticking layer are intended to enable measurements of the rings' average persistent current ⟨I⟩ in the presence of relatively small magnetic fields. We describe the motivation for these measurements, the fabrication of the devices, and the characterization of the cantilevers' mechanical properties. We also discuss the devices' expected performance in measurements of ⟨I⟩.

  14. Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films.

    PubMed

    Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

    2016-01-01

    Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions. PMID:26911529

  15. Self-assembly of mesoscopically ordered chromatic polydiacetylene/silica nanocomposites

    NASA Technical Reports Server (NTRS)

    Lu, Y.; Yang, Y.; Sellinger, A.; Lu, M.; Huang, J.; Fan, H.; Haddad, R.; Lopez, G.; Burns, A. R.; Sasaki, D. Y.; Shelnutt, J.; Brinker, C. J.

    2001-01-01

    Nature abounds with intricate composite architectures composed of hard and soft materials synergistically intertwined to provide both useful functionality and mechanical integrity. Recent synthetic efforts to mimic such natural designs have focused on nanocomposites, prepared mainly by slow procedures like monomer or polymer infiltration of inorganic nanostructures or sequential deposition. Here we report the self-assembly of conjugated polymer/silica nanocomposite films with hexagonal, cubic or lamellar mesoscopic order using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. Polymerization results in polydiacetylene/silica nanocomposites that are optically transparent and mechanically robust. Compared to ordered diacetylene-containing films prepared as Langmuir monolayers or by Langmuir-Blodgett deposition, the nanostructured inorganic host alters the diacetylene polymerization behaviour, and the resulting nanocomposite exhibits unusual chromatic changes in response to thermal, mechanical and chemical stimuli. The inorganic framework serves to protect, stabilize, and orient the polymer, and to mediate its function. The nanocomposite architecture also provides sufficient mechanical integrity to enable integration into devices and microsystems.

  16. Mesoscopic Community Structure of Financial Markets Revealed by Price and Sign Fluctuations

    PubMed Central

    Almog, Assaf; Besamusca, Ferry; MacMahon, Mel; Garlaschelli, Diego

    2015-01-01

    The mesoscopic organization of complex systems, from financial markets to the brain, is an intermediate between the microscopic dynamics of individual units (stocks or neurons, in the mentioned cases), and the macroscopic dynamics of the system as a whole. The organization is determined by “communities” of units whose dynamics, represented by time series of activity, is more strongly correlated internally than with the rest of the system. Recent studies have shown that the binary projections of various financial and neural time series exhibit nontrivial dynamical features that resemble those of the original data. This implies that a significant piece of information is encoded into the binary projection (i.e. the sign) of such increments. Here, we explore whether the binary signatures of multiple time series can replicate the same complex community organization of the financial market, as the original weighted time series. We adopt a method that has been specifically designed to detect communities from cross-correlation matrices of time series data. Our analysis shows that the simpler binary representation leads to a community structure that is almost identical with that obtained using the full weighted representation. These results confirm that binary projections of financial time series contain significant structural information. PMID:26226226

  17. A large field of view two-photon mesoscope with subcellular resolution for in vivo imaging

    PubMed Central

    Sofroniew, Nicholas James; Flickinger, Daniel; King, Jonathan; Svoboda, Karel

    2016-01-01

    Imaging is used to map activity across populations of neurons. Microscopes with cellular resolution have small (<1 millimeter) fields of view and cannot simultaneously image activity distributed across multiple brain areas. Typical large field of view microscopes do not resolve single cells, especially in the axial dimension. We developed a 2-photon random access mesoscope (2p-RAM) that allows high-resolution imaging anywhere within a volume spanning multiple brain areas (∅ 5 mm x 1 mm cylinder). 2p-RAM resolution is near diffraction limited (lateral, 0.66 μm, axial 4.09 μm at the center; excitation wavelength = 970 nm; numerical aperture = 0.6) over a large range of excitation wavelengths. A fast three-dimensional scanning system allows efficient sampling of neural activity in arbitrary regions of interest across the entire imaging volume. We illustrate the use of the 2p-RAM by imaging neural activity in multiple, non-contiguous brain areas in transgenic mice expressing protein calcium sensors. DOI: http://dx.doi.org/10.7554/eLife.14472.001 PMID:27300105

  18. Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

    NASA Astrophysics Data System (ADS)

    Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

    2016-02-01

    Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions.

  19. Fabrication and characterization of large arrays of mesoscopic gold rings on large-aspect-ratio cantilevers

    SciTech Connect

    Ngo, D. Q.; Petković, I. Lollo, A.; Castellanos-Beltran, M. A.; Harris, J. G. E.

    2014-10-15

    We have fabricated large arrays of mesoscopic metal rings on ultrasensitive cantilevers. The arrays are defined by electron beam lithography and contain up to 10{sup 5} rings. The rings have a circumference of 1 μm, and are made of ultrapure (6N) Au that is deposited onto a silicon-on-insulator wafer without an adhesion layer. Subsequent processing of the SOI wafer results in each array being supported at the end of a free-standing cantilever. To accommodate the large arrays while maintaining a low spring constant, the cantilevers are nearly 1 mm in both lateral dimensions and 100 nm thick. The extreme aspect ratio of the cantilevers, the large array size, and the absence of a sticking layer are intended to enable measurements of the rings' average persistent current in the presence of relatively small magnetic fields. We describe the motivation for these measurements, the fabrication of the devices, and the characterization of the cantilevers' mechanical properties. We also discuss the devices' expected performance in measurements of .

  20. Mesoscopic Effects in an Agent-Based Bargaining Model in Regular Lattices

    PubMed Central

    Poza, David J.; Santos, José I.; Galán, José M.; López-Paredes, Adolfo

    2011-01-01

    The effect of spatial structure has been proved very relevant in repeated games. In this work we propose an agent based model where a fixed finite population of tagged agents play iteratively the Nash demand game in a regular lattice. The model extends the multiagent bargaining model by Axtell, Epstein and Young [1] modifying the assumption of global interaction. Each agent is endowed with a memory and plays the best reply against the opponent's most frequent demand. We focus our analysis on the transient dynamics of the system, studying by computer simulation the set of states in which the system spends a considerable fraction of the time. The results show that all the possible persistent regimes in the global interaction model can also be observed in this spatial version. We also find that the mesoscopic properties of the interaction networks that the spatial distribution induces in the model have a significant impact on the diffusion of strategies, and can lead to new persistent regimes different from those found in previous research. In particular, community structure in the intratype interaction networks may cause that communities reach different persistent regimes as a consequence of the hindering diffusion effect of fluctuating agents at their borders. PMID:21408019

  1. Spontaneous formation of permanent shear bands in a mesoscopic model of flowing disordered matter

    NASA Astrophysics Data System (ADS)

    Martens, Kirsten; Bocquet, Lydéric; Barrat, Jean-Louis

    2012-02-01

    In this presentation we propose a coherent scenario of the formation of permanent shear bands in the flow of yield stress materials. Within a minimalistic mesoscopic model we investigate the spatial organisation of plasticity. The most important parameter is the typical time needed to regain the original structure after a local rearrangement. In agreement with a recent mean field study [Coussot et al., Eur. Phys. J. E, 2010, 33, 183] we observe a spontaneous formation of permanent shear bands, when this restructuring time is large compared to the typical stress release time in a rearrangement. This heterogeneous flow behaviour is different in nature from the transient dynamical heterogeneities that one observes in the small shear rate limit in flow without shear-banding [Martens et al., Phys. Rev. Lett., 2011, 106, 156001]. We analyse the dependence of the shear bands on system size, shear rate and restructuring time. Further we rationalise the scenario within a mean field version of the model, that explains the instability of the homogeneous flow below a critical shear rate. Our study therefore strongly supports the idea that the characteristic time scales involved in the local dynamics are at the physical origin of permanent shear bands.

  2. Study of vortex states and dynamics in mesoscopic superconducting samples with MFM

    NASA Astrophysics Data System (ADS)

    Polshyn, Gregory; Naibert, Tyler; Chua, Victor; Budakian, Raffi

    Vortex states in superconducting (SC) structures, their dynamics and ways to manipulate them are topics of great interest. We report a new method of magnetic force microscopy (MFM) that allows the study of vortex states in mesoscopic SC samples. For the case of a SC ring, which is biased to a half-integer flux quantum, the flux modulation through the ring caused by the motion of the magnetic tip drives the ring between two consecutive fluxoid states. The corresponding current switching in the ring produces strong position-dependent forces on the cantilever. In the regime where the frequency of the thermally activated jumps between fluxoid states is close to the frequency of the cantilever, large changes in the cantilever frequency and dissipation are observed. This effect may be understood as a stochastic resonance (SR) process. These changes in the cantilever's mechanical properties are used to ``image'' the barrier energies between fluxoid states. Additionally, SR imaging of the barrier energies are used to study the effect of the locally applied magnetic field from the MFM tip on the barrier heights. We report the results of measurements for Al rings. Further, the same imaging technique can be applied to more sophisticated SC structures such as arrays of Josephson junctions.

  3. High-throughput automated home-cage mesoscopic functional imaging of mouse cortex.

    PubMed

    Murphy, Timothy H; Boyd, Jamie D; Bolaños, Federico; Vanni, Matthieu P; Silasi, Gergely; Haupt, Dirk; LeDue, Jeff M

    2016-01-01

    Mouse head-fixed behaviour coupled with functional imaging has become a powerful technique in rodent systems neuroscience. However, training mice can be time consuming and is potentially stressful for animals. Here we report a fully automated, open source, self-initiated head-fixation system for mesoscopic functional imaging in mice. The system supports five mice at a time and requires minimal investigator intervention. Using genetically encoded calcium indicator transgenic mice, we longitudinally monitor cortical functional connectivity up to 24 h per day in >7,000 self-initiated and unsupervised imaging sessions up to 90 days. The procedure provides robust assessment of functional cortical maps on the basis of both spontaneous activity and brief sensory stimuli such as light flashes. The approach is scalable to a number of remotely controlled cages that can be assessed within the controlled conditions of dedicated animal facilities. We anticipate that home-cage brain imaging will permit flexible and chronic assessment of mesoscale cortical function. PMID:27291514

  4. Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces.

    PubMed

    Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Gama Goicochea, Armando

    2015-10-21

    The interfacial and structural properties of fluids confined by surfaces of different geometries are studied at the mesoscopic scale using dissipative particle dynamics simulations in the grand canonical ensemble. The structure of the surfaces is modeled by a simple function, which allows us to simulate readily different types of surfaces through the choice of three parameters only. The fluids we have modeled are confined either by two smooth surfaces or by symmetrically and asymmetrically structured walls. We calculate structural and thermodynamic properties such as the density, temperature and pressure profiles, as well as the interfacial tension profiles for each case and find that a structural order-disorder phase transition occurs as the degree of surface roughness increases. However, the magnitude of the interfacial tension is insensitive to the structuring of the surfaces and depends solely on the magnitude of the solid-fluid interaction. These results are important for modern nanotechnology applications, such as in the enhanced recovery of oil, and in the design of porous materials with specifically tailored properties. PMID:26387742

  5. Mesoscopic Impurities Expose a Nucleation-Limited Regime of Crystal Growth

    NASA Astrophysics Data System (ADS)

    Sleutel, Mike; Lutsko, James F.; Maes, Dominique; Van Driessche, Alexander E. S.

    2015-06-01

    Nanoscale self-assembly is naturally subject to impediments at the nanoscale. The recently developed ability to follow processes at the molecular level forces us to resolve older, coarse-grained concepts in terms of their molecular mechanisms. In this Letter, we highlight one such example. We present evidence based on experimental and simulation data that one of the cornerstones of crystal growth theory, the Cabrera-Vermilyea model of step advancement in the presence of impurities, is based on incomplete physics. We demonstrate that the piercing of an impurity fence by elementary steps is not solely determined by the Gibbs-Thomson effect, as assumed by Cabrera-Vermilyea. Our data show that for conditions leading up to growth cessation, step retardation is dominated by the formation of critically sized fluctuations. The growth recovery of steps is counter to what is typically assumed, not instantaneous. Our observations on mesoscopic impurities for lysozyme expose a nucleation-dominated regime of growth that has not been hitherto considered, where the system alternates between zero and near-pure velocity. The time spent by the system in arrest is the nucleation induction time required for the step to amass a supercritical fluctuation that pierces the impurity fence.

  6. Collaborative study for the establishment of two European Pharmacopoeia Biological Reference Preparations for serological potency testing of tetanus vaccines for veterinary use.

    PubMed

    Lensing, H H; Behr-Gross, M E; Daas, A; Spieser, J M

    2002-01-01

    The European Directorate for the Quality of Medicines (EDQM) has organised an international collaborative study, divided into two phases, aimed at producing and establishing two suitable reference sera for serological potency testing of tetanus vaccines for veterinary use for batch consistency demonstration. In phase I pools of sera were produced by immunising guinea pigs and rabbits with tetanus toxoid using the immunisation schedule prescribed by the European Pharmacopoeia (Ph. Eur.) for potency testing of tenanus vaccines for veterinary use. Following aliquoting and freeze-drying, characterization of the materials by immunochemical and biological assays enabled us to conclude that the sera should be suitable reference materials in respect of in-vitro assay methods for Clostridium (C.) tetani. The candidate (c) Ph. Eur. Biological Reference Preparations (BRP) were calibrated by Toxin Binding Inhibition test (ToBI) in phase II of the study by a large group of laboratories, including both manufacturers and official medicines control laboratories (OMCL). The activity of the proposed reference sera was determined by comparison with the existing equine monovalent World Health Organization (WHO) International Standard (IS). This study enabled us to provide a definitive value for the antitoxin activity of the reference preparations in respect of their anti-tetanus antibody content.

  7. Host range testing of Tamarixia radiata (Hymenoptera: Eulophidae) sourced from the Punjab of Pakistan for classical biological control of Diaphorina citri (Hemiptera: Liviidae: Euphyllurinae: Diaphorinini) in California.

    PubMed

    Hoddle, Mark S; Pandey, Raju

    2014-02-01

    ABSTRACT Tests evaluating the host range of Tamarixia radiata (Waterson) (Hymenoptera: Eulophidae), a parasitoid of the pestiferous Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), sourced from the Punjab of Pakistan, were conducted in quarantine at the University of California, Riverside, CA. Seven nontarget psyllid species (five native and two self-introduced species) representing five families were exposed to T radiata under the following three different exposure scenarios: 1) sequential no-choice tests, 2) static no-choice tests, and 3) choice tests. Nontarget species were selected for testing based on the following criteria: 1) taxonomic relatedness to the target, D. citri; 2) native psyllids inhabiting native host plants related to citrus that could release volatiles attractive to T. radiata; 3) native psyllids with a high probability of occurrence in native vegetation surrounding commercial citrus groves that could be encountered by T. radiata emigrating from D. citri-infested citrus orchards; 4) a common native pest psyllid species; and 5) a beneficial psyllid attacking a noxious weed. The results of host range testing were unambiguous; T radiata exhibited a narrow host range and high host specificity, with just one species of nontarget psyllid, the abundant native pest Bactericera cockerelli Sulc, being parasitized at low levels (< 5%). These results suggest that the likelihood of significant nontarget impacts is low, and the establishment of T. radiata in southern California for the classical biological control of D. citri poses negligible environmental risk.

  8. Host range testing of Tamarixia radiata (Hymenoptera: Eulophidae) sourced from the Punjab of Pakistan for classical biological control of Diaphorina citri (Hemiptera: Liviidae: Euphyllurinae: Diaphorinini) in California.

    PubMed

    Hoddle, Mark S; Pandey, Raju

    2014-02-01

    ABSTRACT Tests evaluating the host range of Tamarixia radiata (Waterson) (Hymenoptera: Eulophidae), a parasitoid of the pestiferous Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), sourced from the Punjab of Pakistan, were conducted in quarantine at the University of California, Riverside, CA. Seven nontarget psyllid species (five native and two self-introduced species) representing five families were exposed to T radiata under the following three different exposure scenarios: 1) sequential no-choice tests, 2) static no-choice tests, and 3) choice tests. Nontarget species were selected for testing based on the following criteria: 1) taxonomic relatedness to the target, D. citri; 2) native psyllids inhabiting native host plants related to citrus that could release volatiles attractive to T. radiata; 3) native psyllids with a high probability of occurrence in native vegetation surrounding commercial citrus groves that could be encountered by T. radiata emigrating from D. citri-infested citrus orchards; 4) a common native pest psyllid species; and 5) a beneficial psyllid attacking a noxious weed. The results of host range testing were unambiguous; T radiata exhibited a narrow host range and high host specificity, with just one species of nontarget psyllid, the abundant native pest Bactericera cockerelli Sulc, being parasitized at low levels (< 5%). These results suggest that the likelihood of significant nontarget impacts is low, and the establishment of T. radiata in southern California for the classical biological control of D. citri poses negligible environmental risk. PMID:24665694

  9. The relative utility of health-related fitness tests and skilled motor performance tests as measures of biological age in Japanese men.

    PubMed

    Lee, M S; Tanaka, K; Nakagaichi, M; Nakadomo, F; Watanabe, K; Takeshima, N; Hiyama, T; Chodzko-Zaiko, W

    1996-05-01

    In the present paper we report the results of a study in which we compared 2 different approaches to the computation of biological age (BA) in a sample of 322 Japanese men (age range 20 to 79 years). In the first approach, 4 commonly used measures of health-related fitness (VO2peak, trunk flexion from a standing position, body fat, and grip strength) were reduced to a single BA score (HRF Age) using principal component analysis. In contrast, in the second approach, 3 commonly used measures of skilled motor performance and agility (vertical jump, stepping side-to-side, and balancing on one leg with eyes closed) were reduced to a single BA score (SMP Age) using similar multivariate procedures. The criterion-related validity of both of the BA measures was examined by assessing each measure's ability to discriminate between healthy and active groups of subjects. This was achieved by classifying the original subject pool into regularly active (ACT; n = 108) and healthy (HLTH; n = 169) subgroups on the basis of self-reported activity levels. Analyses revealed that HRF Age was a more powerful discriminator between the two activity groups than SMP Age. While HRF Age of HLTH subjects was very close to their chronological age (CA), in the ACT group, HRF Age was on average 15 years less than their CA (P < 0.05). In a separate analysis, we assessed the HRF Age of patients with ischemic heart disease, hypertension, obesity, or diabetes (PAT; n = 45). The HRF Age of these subjects averaged 10 years above their CA. Our data suggest that commonly used measures of health-related fitness can be usefully employed as indices of BA which differentiate between individuals of similar ages but differing health and physical activity status. In contrast, measures of skilled motor performance were found to be less valuable measures of BA. The implication of our findings for future experimental design in exercise and aging research is discussed.

  10. Biological Science: An Ecological Approach. BSCS Green Version. Teacher's Resource Book and Test Item Bank. Sixth Edition.

    ERIC Educational Resources Information Center

    Biological Sciences Curriculum Study, Colorado Springs.

    This book consists of four sections: (1) "Supplemental Materials"; (2) "Supplemental Investigations"; (3) "Test Item Bank"; and (4) "Blackline Masters." The first section provides additional background material related to selected chapters and investigations in the student book. Included are a periodic table of the elements, genetics problems and…

  11. Tested Studies for Laboratory Teaching. Proceedings of the Workshop/Conference of the Association for Biology Laboratory Education (ABLE) (13th, Laramie, Wyoming, June 11-15, 1991). Volume 13.

    ERIC Educational Resources Information Center

    Goldman, Corey A., Ed.

    The focus of the Association for Biology Laboratory Education (ABLE) is to improve the undergraduate biology laboratory experience by promoting the development and dissemination of interesting, innovative, and reliable laboratory exercises. This proceedings volume contains 10 papers: "Testing Issues of Foraging and Flocking Behavior" (C. C.…

  12. Testing the museum versus cradle tropical biological diversity hypothesis: phylogeny, diversification, and ancestral biogeographic range evolution of the ants.

    PubMed

    Moreau, Corrie S; Bell, Charles D

    2013-08-01

    Ants are one of the most ecologically and numerically dominant group of terrestrial organisms with most species diversity currently found in tropical climates. Several explanations for the disparity of biological diversity in the tropics compared to temperate regions have been proposed including that the tropics may act as a "museum" where older lineages persist through evolutionary time or as a "cradle" where new species continue to be generated. We infer the molecular phylogenetic relationships of 295 ant specimens including members of all 21 extant subfamilies to explore the evolutionary diversification and biogeography of the ants. By constraining the topology and age of the root node while using 45 fossils as minimum constraints, we converge on an age of 139-158 Mya for the modern ants. Further diversification analyses identified 10 periods with a significant change in the tempo of diversification of the ants, although these shifts did not appear to correspond to ancestral biogeographic range shifts. Likelihood-based historical biogeographic reconstructions suggest that the Neotropics were important in early ant diversification (e.g., Cretaceous). This finding coupled with the extremely high-current species diversity suggests that the Neotropics have acted as both a museum and cradle for ant diversity.

  13. A specific method for measurement of equine active myeloperoxidase in biological samples and in in vitro tests.

    PubMed

    Franck, Thierry; Kohnen, S; Deby-Dupont, G; Grulke, S; Deby, C; Serteyn, D

    2006-07-01

    An original method called SIEFED (specific immunological extraction followed by enzymatic detection) was developed for the specific detection of the activity of equine myeloperoxidase (MPO). The method consists of the extraction of MPO from aqueous solutions by immobilized anti-MPO antibodies followed by washing (to eliminate proteins and interfering molecules) and measurement of MPO activity using a detection system containing a fluorogenic substrate, hydrogen peroxide, and nitrite as reaction enhancer. The SIEFED technique was applied to study active MPO in horse biological fluids and the effects of 2 polyphenolic molecules, curcumin and resveratrol, on MPO activity. The detection limit of the SIEFED was 0.23 mU/ml. The SIEFED exhibited good precision with intra-assay and interassay coefficients of variation below 10% and 20%, respectively, for MPO activities ranging from 0.25 to 6.4 mU/ml. The activity of MPO was generally higher than 1 mU/ml in the fluids collected from horses with inflammatory diseases. Curcumin and resveratrol exerted a dose-dependent inhibition on MPO activity and, as they were removed before the enzymatic detection of MPO, the results suggest a direct drug-nzyme interaction or an enzyme structure modification by the drug. The SIEFED is a new tool that would be useful for specific detection of active MPO in complex media and for selection of MPO activity modulators.

  14. Apparatus for measuring the finite load-deformation behavior of a sheet of epithelial cells cultured on a mesoscopic freestanding elastomer membrane

    SciTech Connect

    Selby, John C.; Shannon, Mark A.

    2007-09-15

    Details are given for the design, calibration, and operation of an apparatus for measuring the finite load-deformation behavior of a sheet of living epithelial cells cultured on a mesoscopic freestanding elastomer membrane, 10 {mu}m thick and 5 mm in diameter. Although similar in concept to bulge tests used to investigate the mechanical properties of micromachined thin films, cell-elastomer composite diaphragm inflation tests pose a unique set of experimental challenges. Composite diaphragm (CD) specimens are extremely compliant (E<50 kPa), experience large displacements when subject to small inflation pressures ({approx}100 Pa), and must be continuously immersed in a bath of liquid culture medium during the acquisition of load-deformation measurements. Given these considerations, we have constructed an inflation apparatus consisting of an air-piston-cylinder pump integrated with a modular specimen mounting fixture that constitutes a horizontally semi-infinite reservoir of liquid culture medium. In a deformation-controlled inflation test, pressurized air is used to inflate a CD specimen into the liquid reservoir with minimum disturbance of the liquid-air interface. Piston displacements and absolute pump chamber air pressures are utilized as feedback to cycle the displaced (or inflated) CD volume V in a 0.05 Hz triangular or sinusoidal wave form (V{sub MIN}=0 {mu}l, V{sub MAX}{<=}40 {mu}l) while simultaneously recording the inflation pressure acting at the fixed boundary of the specimen, p(r=a). Using a carefully prescribed six-cycle inflation test protocol, the apparatus is shown to be capable of measuring the [V,p(r=a)] inflation response of a cell-elastomer CD with random uncertainties estimated at {+-}0.45 {mu}l and {+-}2.5 Pa, respectively.

  15. Apparatus for measuring the finite load-deformation behavior of a sheet of epithelial cells cultured on a mesoscopic freestanding elastomer membrane

    NASA Astrophysics Data System (ADS)

    Selby, John C.; Shannon, Mark A.

    2007-09-01

    Details are given for the design, calibration, and operation of an apparatus for measuring the finite load-deformation behavior of a sheet of living epithelial cells cultured on a mesoscopic freestanding elastomer membrane, 10μm thick and 5mm in diameter. Although similar in concept to bulge tests used to investigate the mechanical properties of micromachined thin films, cell-elastomer composite diaphragm inflation tests pose a unique set of experimental challenges. Composite diaphragm (CD) specimens are extremely compliant (E<50kPa), experience large displacements when subject to small inflation pressures (˜100Pa), and must be continuously immersed in a bath of liquid culture medium during the acquisition of load-deformation measurements. Given these considerations, we have constructed an inflation apparatus consisting of an air-piston-cylinder pump integrated with a modular specimen mounting fixture that constitutes a horizontally semi-infinite reservoir of liquid culture medium. In a deformation-controlled inflation test, pressurized air is used to inflate a CD specimen into the liquid reservoir with minimum disturbance of the liquid-air interface. Piston displacements and absolute pump chamber air pressures are utilized as feedback to cycle the displaced (or inflated) CD volume V in a 0.05Hz triangular or sinusoidal wave form (VMIN=0μl, VMAX⩽40μl) while simultaneously recording the inflation pressure acting at the fixed boundary of the specimen, p(r =a). Using a carefully prescribed six-cycle inflation test protocol, the apparatus is shown to be capable of measuring the [V,p(r=a)] inflation response of a cell-elastomer CD with random uncertainties estimated at ±0.45μl and ±2.5Pa, respectively.

  16. Amphibian embryos as a biological test for environmental pollutants in leachates, industrial effluents, surface and ground water

    SciTech Connect

    Herkovits, J.; Perez-Coll, C.S.; Herkovits, F.D.; Tarlato, M.

    1995-12-31

    Test of early life stages are very sensitive to toxic effects and moreover a good predictive correlation between embryo-larval survival and independent ecological parameters such as species richness and diversity have been established. The main purpose of this preliminary study is to report that Bufo arenarum embryos are very sensitive to contaminants from a variety of sources such as leachates, industrial effluents, surface and ground water. The toxicity of 30 samples (five from each category plus controls of surface and ground water from reference places) was evaluated during a 14 day renewal toxicity test at 20 C, conducted with 10 embryos (by triplicate) from stage 23--25 onwards using six concentrations (V/V) of each sample of Holtfreter`s solution. For industrial effluents and leachates the results range from a concentration of 0.6% resulting in 24hs LC100 up to a sample which exert 20% of lethality after 14 days of treatment. The survival of controls and in samples from reference places was over 90% for 7 days and over 80% for 14 days. The results with Bufo arenarum embryos confirm that a 7 day Short-term Chronic Toxicity Test is appropriate for toxicity screening of industrial effluents (as it was established by EPA for whole effluent toxicity test for aquatic life protection performed with other species) as well as for leachates. On the other hand, for freshwater (surface and ground), it is convenient to extend the exposure period until 14 days in order to record situations of low, but significant levels of toxicity, which could be of particular value for surface as well as ground water quality criteria.

  17. A Novel Malaria Pf/Pv Ab Rapid Diagnostic Test Using a Differential Diagnostic Marker Identified by Network Biology.

    PubMed

    Cho, Sung Jin; Lee, Jihoo; Lee, Hyun Jae; Jo, Hyun-Young; Sinniah, Mangalam; Kim, Hak-Yong; Chong, Chom-Kyu; Song, Hyun-Ok

    2016-01-01

    Rapid diagnostic tests (RDTs) can detect anti-malaria antibodies in human blood. As they can detect parasite infection at the low parasite density, they are useful in endemic areas where light infection and/or re-infection of parasites are common. Thus, malaria antibody tests can be used for screening bloods in blood banks to prevent transfusion-transmitted malaria (TTM), an emerging problem in malaria endemic areas. However, only a few malaria antibody tests are available in the microwell-based assay format and these are not suitable for field application. A novel malaria antibody (Ab)-based RDT using a differential diagnostic marker for falciparum and vivax malaria was developed as a suitable high-throughput assay that is sensitive and practical for blood screening. The marker, merozoite surface protein 1 (MSP1) was discovered by generation of a Plasmodium-specific network and the hierarchical organization of modularity in the network. Clinical evaluation revealed that the novel Malaria Pf/Pv Ab RDT shows improved sensitivity (98%) and specificity (99.7%) compared with the performance of a commercial kit, SD BioLine Malaria P.f/P.v (95.1% sensitivity and 99.1% specificity). The novel Malaria Pf/Pv Ab RDT has potential for use as a cost-effective blood-screening tool for malaria and in turn, reduces TTM risk in endemic areas. PMID:27313496

  18. A Novel Malaria Pf/Pv Ab Rapid Diagnostic Test Using a Differential Diagnostic Marker Identified by Network Biology

    PubMed Central

    Cho, Sung Jin; Lee, Jihoo; Lee, Hyun Jae; Jo, Hyun-Young; Sinniah, Mangalam; Kim, Hak-Yong; Chong, Chom-Kyu; Song, Hyun-Ok

    2016-01-01

    Rapid diagnostic tests (RDTs) can detect anti-malaria antibodies in human blood. As they can detect parasite infection at the low parasite density, they are useful in endemic areas where light infection and/or re-infection of parasites are common. Thus, malaria antibody tests can be used for screening bloods in blood banks to prevent transfusion-transmitted malaria (TTM), an emerging problem in malaria endemic areas. However, only a few malaria antibody tests are available in the microwell-based assay format and these are not suitable for field application. A novel malaria antibody (Ab)-based RDT using a differential diagnostic marker for falciparum and vivax malaria was developed as a suitable high-throughput assay that is sensitive and practical for blood screening. The marker, merozoite surface protein 1 (MSP1) was discovered by generation of a Plasmodium-specific network and the hierarchical organization of modularity in the network. Clinical evaluation revealed that the novel Malaria Pf/Pv Ab RDT shows improved sensitivity (98%) and specificity (99.7%) compared with the performance of a commercial kit, SD BioLine Malaria P.f/P.v (95.1% sensitivity and 99.1% specificity). The novel Malaria Pf/Pv Ab RDT has potential for use as a cost-effective blood-screening tool for malaria and in turn, reduces TTM risk in endemic areas. PMID:27313496

  19. Electrodynamic soil plate oscillator: Modeling nonlinear mesoscopic elastic behavior and hysteresis in nonlinear acoustic landmine detection

    NASA Astrophysics Data System (ADS)

    Korman, M. S.; Duong, D. V.; Kalsbeck, A. E.

    2015-10-01

    An apparatus (SPO), designed to study flexural vibrations of a soil loaded plate, consists of a thin circular elastic clamped plate (and cylindrical wall) supporting a vertical soil column. A small magnet attached to the center of the plate is driven by a rigid AC coil (located coaxially below the plate) to complete the electrodynamic soil plate oscillator SPO design. The frequency dependent mechanical impedance Zmech (force / particle velocity, at the plate's center) is inversely proportional to the electrical motional impedance Zmot. Measurements of Zmot are made using the complex output to input response of a Wheatstone bridge that has an identical coil element in one of its legs. Near resonance, measurements of Zmot (with no soil) before and after a slight point mass loading at the center help determine effective mass, spring, damping and coupling constant parameters of the system. "Tuning curve" behavior of real{ Zmot } and imaginary{ Zmot } at successively higher vibration amplitudes of dry sifted masonry sand are measured. They exhibit a decrease "softening" in resonance frequency along with a decrease in the quality Q factor. In soil surface vibration measurements a bilinear hysteresis model predicts the tuning curve shape for this nonlinear mesoscopic elastic SPO behavior - which also models the soil vibration over an actual plastic "inert" VS 1.6 buried landmine. Experiments are performed where a buried 1m cube concrete block supports a 12 inch deep by 30 inch by 30 inch concrete soil box for burying a VS 1.6 in dry sifted masonry sand for on-the-mine and off-the-mine soil vibration experiments. The backbone curve (a plot of the peak amplitude vs. corresponding resonant frequency from a family of tuning curves) exhibits mostly linear behavior for "on target" soil surface vibration measurements of the buried VS 1.6 or drum-like mine simulants for relatively low particle velocities of the soil. Backbone curves for "on target" measurements exhibit

  20. On the microscopic and mesoscopic perturbations of lipid bilayers upon interaction with the MPER domain of the HIV glycoprotein gp41.

    PubMed

    Oliva, Rosario; Emendato, Alessandro; Vitiello, Giuseppe; De Santis, Augusta; Grimaldi, Manuela; D'Ursi, Anna Maria; Busi, Elena; Del Vecchio, Pompea; Petraccone, Luigi; D'Errico, Gerardino

    2016-08-01

    The effect of the 665-683 fragment of the HIV fusion glycoprotein 41, corresponding to the MPER domain of the protein and named gp41MPER, on the microscopic structure and mesoscopic arrangement of palmitoyl oleoyl phosphatidylcholine (POPC) and POPC/sphingomyelin (SM)/cholesterol (CHOL) lipid bilayers is analyzed. The microscopic structuring of the bilayers has been studied by Electron Spin Resonance (ESR) spectroscopy, using glycerophosphocholines spin-labelled in different positions along the acyl chain. Transitions of the bilayer liquid crystalline state have been also monitored by Differential Scanning Calorimetry (DSC). Changes of the bilayers morphology have been studied by determining the dimension of the liposomes through Dynamic Light Scattering (DLS) measurements. The results converge in showing that the sample preparation procedure, the bilayer composition and the peptide/lipid ratio critically tune the lipid response to the peptide/membrane interaction. When gp41MPER is added to preformed liposomes, it positions at the bilayer interface and the lipid perturbation is limited to the more external segments. In contrast, if the peptide is mixed with the lipids during the liposome preparation, it assumes a trans-membrane topology. This happens at all peptide/lipid ratios for fluid POPC bilayers, while in the case of rigid POPC/SM/CHOL membranes a minimum ratio has to be reached, thus suggesting peptide self-aggregation to occur. Peptide insertion results in a dramatic increase of the lipid ordering and bilayer stiffening, which reflect in significant changes in liposome average dimension and distribution. The biological implications of these findings are discussed. PMID:27179640