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Sample records for porous matrices constituted

  1. Sericin-carboxymethyl cellulose porous matrices as cellular wound dressing material.

    PubMed

    Nayak, Sunita; Kundu, S C

    2014-06-01

    In this study, porous three-dimensional (3D) hydrogel matrices are fabricated composed of silk cocoon protein sericin of non-mulberry silkworm Antheraea mylitta and carboxymethyl cellulose. The matrices are prepared via freeze-drying technique followed by dual cross-linking with glutaraldehyde and aluminum chloride. The microstructure of the hydrogel matrices is assessed using scanning electron microscopy and biophysical characterization are carried out using Fourier transform infrared spectroscopy and X-ray diffraction. The transforming growth factor β1 release from the cross-linked matrices as a growth factor is evaluated by immunosorbent assay. Live dead assay and 3-[4,5-dimethylthiazolyl-2]-2,5-diphenyl tetrazolium bromide assay show no cytotoxicity of blended matrices toward human keratinocytes. The matrices support the cell attachment and proliferation of human keratinocytes as observed through scanning electron microscope and confocal images. Gelatin zymography demonstrates the low levels of matrix metalloproteinase 2 (MMP-2) and insignificant amount of MMP-9 in the culture media of cell seeded matrices. Low inflammatory response of the matrices is indicated through tumor necrosis factor alpha release assay. The results indicate that the fabricated matrices constitute 3D cell-interactive environment for tissue engineering applications and its potential use as a future cellular biological wound dressing material. PMID:23853114

  2. NMR studies of metallic tin confined within porous matrices

    SciTech Connect

    Charnaya, E. V.; Tien, Cheng; Lee, M. K.; Kumzerov, Yu. A.

    2007-04-01

    {sup 119}Sn NMR studies were carried out for metallic tin confined within synthetic opal and porous glass. Tin was embedded into nanoporous matrices in the melted state under pressure. The Knight shift for liquid confined tin was found to decrease with decreasing pore size. Correlations between NMR line shapes, Knight shift, and pore filling were observed. The melting and freezing phase transitions of tin under confinement were studied through temperature dependences of NMR signals upon warming and cooling. Melting of tin within the opal matrix agreed well with the liquid skin model suggested for small isolated particles. The influence of the pore filling on the melting process was shown.

  3. Optical properties of Ge nanostructures embedded into porous alumina matrices

    NASA Astrophysics Data System (ADS)

    Beltiukov, A.; Valeev, R.; Zakirova, R.

    2016-04-01

    The effect of structural properties and the morphology of Ge@PAA nanocomposites synthesized by thermal deposition of Ge on porous anodic alumina matrices with different porosity on the band gap value and PL properties is investigated. PL in the range of 330–520 nm may be due to F and F2 luminescent centers in the surface of nanopores of PAA matrices. The density of electronic states in this interface depends on the temperature of matrices during deposition and on the surface morphology. The role of radiative recombination centers is played by the broken bonds in a thin intermediate Ge x –Al y –O z layer in the Ge/oxide matrix interface. No obvious effect of the crystalline structure of germanium nanoparticles on the PL maximum position is observed, but the spatial localization of electron–hole pairs of small-sized Ge crystallites of which nanoparticles consist leads to an increase in the optical band gap.

  4. A variational constitutive model for porous metal plasticity

    NASA Astrophysics Data System (ADS)

    Weinberg, K.; Mota, A.; Ortiz, M.

    2006-01-01

    This paper presents a variational formulation of viscoplastic constitutive updates for porous elastoplastic materials. The material model combines von Mises plasticity with volumetric plastic expansion as induced, e.g., by the growth of voids and defects in metals. The finite deformation theory is based on the multiplicative decomposition of the deformation gradient and an internal variable formulation of continuum thermodynamics. By the use of logarithmic and exponential mappings the stress update algorithms are extended from small strains to finite deformations. Thus the time-discretized version of the porous-viscoplastic constitutive updates is described in a fully variational manner. The range of behavior predicted by the model and the performance of the variational update are demonstrated by its application to the forced expansion and fragmentation of U-6%Nb rings.

  5. Upscaling of Constitutive Relations I Unsaturated Heterogeneous Porous Media

    SciTech Connect

    H. H. Liu; G. S. Bodvarsson

    2001-05-31

    When numerical model are used for modeling field scale flow and transport processes in the subsurface, the problem of ''upscaling'' arises. Typical scales, corresponding to spatial resolutions of subsurface heterogeneity in numerical models, are generally much larger than the measurement scale of the parameters and physical processes involved. The upscaling problems is, then, one of assigning parameters to gridblock scale based on parameter values measured on small scales. The focus of this study is to develop an approach to determine large-scale (upscaled) constitutive relations (relationships among relative permeability, capillary pressure and saturation) from small-scale measurements for porous media for a range of air entry values that are typical for the tuff matrix in the unsaturated zone of Yucca Mountain. For porous media with large air entry values, capillary forces play a key role in determining spatial water distribution at large-scales. Therefore, a relatively uniform capillary pressure approximately exists even for a large gridblock scale under steady state flow conditions. Based on these reasoning, we developed formulations that relate upscaled constitutive relations to ones measured at core-scale. Numerical experiments with stochastically generated heterogeneous porous media were used to evaluate the upscaling formulations.

  6. An Experimental Study and Constitutive Modeling of Saturated Porous Rocks

    NASA Astrophysics Data System (ADS)

    Xie, S. Y.; Shao, J. F.

    2015-01-01

    This paper is devoted to the experimental characterization and constitutive modeling of saturated porous rocks. A typical porous chalk is investigated. Drained hydrostatic and triaxial compression tests are first performed to characterize the basic mechanical behavior of chalk. Drained triaxial tests with constant interstitial pressure are then carried out to study the effects of interstitial pressure on the plastic deformation and failure criterion. Finally, undrained triaxial compression tests are performed to investigate poromechanical coupling in saturated conditions. Based on the experimental data and some relevant micromechanical considerations, a micromechanics-based plastic model is proposed and extended to poroplastic coupling using the effective stress concept. The proposed model is verified through comparisons between the numerical results and experimental data for both drained and undrained tests.

  7. Immobilization of plutonium from solutions on porous matrices by the method of high temperature sorption

    SciTech Connect

    Nardova, A.K.; Filippov, E.A.; Glagolenko, Y.B.

    1996-05-01

    This report presents the results of investigations of plutonium immobilization from solutions on inorganic matrices with the purpose of producing a solid waste form. High-temperature sorption is described which entails the adsorption of radionuclides from solutions on porous, inorganic matrices, as for example silica gel. The solution is brought to a boil with additional thermal process (calcination) of the saturated granules.

  8. Compaction localization and constitutive behavior of weak porous sandstone.

    SciTech Connect

    Holcomb, David Joseph; Dewers, Thomas A.; Issen, Kathleen

    2009-06-01

    A combined experimental and constitutive modeling program for weak porous sandstone deformation is described. A series of axisymmetric compression tests were performed over a range of mean stresses to study dilatational, compactional and transitional regimes. Experimental results were used both to derive constitutive parameters for testing localization theory and to parameterize a poroelastic-plastic model. Observed strain localization, imaged syn-deformationally using acoustic emissions, includes high- and low-angle shear and low angle compactional features or 'bands'. Isotropic elastic moduli measured via unloading loops show a progressive degradation pre-failure as decreasing functions of work-conjugate plastic strains and increasing functions of stress magnitude. The degradation pathway is unique for samples which underwent localization versus those that underwent spatially pervasive pore collapse. Total shear and volume strains are partitioned into elastic and plastic portions including the ''coupling'' strain associated with modulus degradation. Plastic strain calculated with and without the coupling term is compared with regard to localization predictions. Both coupled and uncoupled cases predict high angle shear bands for uniaxial and low mean stress conditions on the dilatational side of the yield surface. Uncoupled predictions show progressively lower angle shear bands approaching the transitional regime (stress conditions approaching the 'cap' surface). When elastic-plastic coupling is accounted for, compaction bands are predicted for the transitional regime, as are observed in the experiments. Finite element modeling efforts are described using a 3-invariant, mixed-hardening, continuous yield surface, elasto-plasticity model that includes several features important for porous sandstone constitutive behavior and observed experimentally, including non-associativity, nonlinear elasticity, elastic-plastic coupling, and kinematic hardening. Modeled

  9. Preparation, characterization, and in vivo evaluation of valsartan porous matrices using emulsion solvent evaporation technique

    PubMed Central

    Babu, Govada Kishore; Babu, Puttagunta Srinivasa; Khagga, Mukkanti

    2016-01-01

    Introduction: Valsartan is a type II Biopharmaceutics Classification System (BCS) classified drug. The poor aqueous solubility restricts its use in developing sustained or controlled release systems for the treatment of chronic hypertensive conditions. The present investigation was conducted with an objective to formulate porous matrices (PMs) of valsartan in order to enhance aqueous solubility. Materials and Methods: Polyvinylpyrrolidone (PVP) K30 and poloxamer 407 were used as hydrophilic carriers; hexane was used as a pore-forming agent, ethanol was used as a solvent, and tween 20 was used as an emulgent. The prepared porous matrices were characterized and based on the maximum slope obtained from the Washburn method and other characterization results; the drug PVP K30 (1:1.5) was selected and further evaluated in vivo by the rat gut method. Results: The prepared porous matrices are white, free-flowing powders. Among prepared formulations drug PVP K30 (1:1.5) showed maximum Washburn slope of 0.0103. The mean particle size was found to be 0.82 μ and D50 (median) value was found to be 0.55 μ. The scanning of particles at various magnifications by scanning electron microscopy (SEM) analysis revealed that the method had effectively induced porosity. The Q value of valsartan from porous matrices was observed at 20 min with a first order regression value of 0.917. The calculated difference factor (F1) when compared with pure valsartan was observed to be 63.32%. From the values obtained, it was evident that the method amplifies the percentage of drug dissolution between sixfold and eightfold when compared to pure drug. From the absorption studies by the rat gut method, the absorption of porous matrices increased threefold. Conclusion: Porous matrices of valsartan: PVP K30 (1:1.5 ratio) hold promise for the enhancement of solubility and consecutive formulation of controlled release systems even with poorly soluble drugs. PMID:27606260

  10. Numerical Modelling of The Response of Porous Sensors of The Matric Potential of Soil Water

    NASA Astrophysics Data System (ADS)

    Ferraris, S.; Whalley, R.

    Porous sensors are used to give an indirect estimate of the matric potential of soil water. In these sensors the water content of a porous matrix in equilibrium with the soil can be used to calculate the matric potential, provided that moisture retention characteristic of the porous matrix is known. The original design of these sensors used a plaster of Paris matrix and AC resistance electrodes to estimate its water content. More recently a ceramic matrix has been used with a dielectric measurement of its water content (e.g. Or and Wraith 1999; Whalley et al. 2001). The advantage of the more recent designs is that they can be used at relatively high water potentials in comparison with plaster of Paris based sensors which have application in dry soils. However, the development of the sensors that are designed to be used in wetter soils, raises the question of the sensor response time. In this paper we use an axial-symmetric 3D numerical solution of the Richards equation to investigate the effect of sensor geometry on the time taken for it to equilibrate with the potential of the soil water. We consider the sensor to have a cylindrical ceramic porous matrix. The effect of the shape of the porous matrix on the equilibration time after changes in soil water potential is modelled. We view the shape of the porous matrix in terms of the ratio of diameter to length and also the volume. The results are discussed in terms of the design requirements of a porous sensor for soil water matric potential. Or, D. &Wraith, J.M. 1999. A new soil matric-potential sensor based on time-domain- reflectometry. Water Resources Research, 35: 3399-3407. Whalley W.R., Watts C.W., Hilhorst M.A., Bird N.R.A., Balendonck J. &Longstaff D. J. 2001. The design of porous material sensors to measure matric potential of water in soil. European Journal of Soil Science, 53: 511-519.

  11. Cell colonization in degradable 3D porous matrices

    PubMed Central

    Lawrence, Benjamin J

    2008-01-01

    Cell colonization is an important in a wide variety of biological processes and applications including vascularization, wound healing, tissue engineering, stem cell differentiation and biosensors. During colonization porous 3D structures are used to support and guide the ingrowth of cells into the matrix. In this review, we summarize our understanding of various factors affecting cell colonization in three-dimensional environment. The structural, biological and degradation properties of the matrix all play key roles during colonization. Further, specific scaffold properties such as porosity, pore size, fiber thickness, topography and scaffold stiffness as well as important cell material interactions such as cell adhesion and mechanotransduction also influence colonization. PMID:19262124

  12. Porous media matric potential and water content measurements during parabolic flight.

    PubMed

    Norikane, Joey H; Jones, Scott B; Steinberg, Susan L; Levine, Howard G; Or, Dani

    2005-01-01

    Control of water and air in the root zone of plants remains a challenge in the microgravity environment of space. Due to limited flight opportunities, research aimed at resolving microgravity porous media fluid dynamics must often be conducted on Earth. The NASA KC-135 reduced gravity flight program offers an opportunity for Earth-based researchers to study physical processes in a variable gravity environment. The objectives of this study were to obtain measurements of water content and matric potential during the parabolic profile flown by the KC-135 aircraft. The flight profile provided 20-25 s of microgravity at the top of the parabola, while pulling 1.8 g at the bottom. The soil moisture sensors (Temperature and Moisture Acquisition System: Orbital Technologies, Madison, WI) used a heat-pulse method to indirectly estimate water content from heat dissipation. Tensiometers were constructed using a stainless steel porous cup with a pressure transducer and were used to measure the matric potential of the medium. The two types of sensors were placed at different depths in a substrate compartment filled with 1-2 mm Turface (calcined clay). The ability of the heat-pulse sensors to monitor overall changes in water content in the substrate compartment decreased with water content. Differences in measured water content data recorded at 0, 1, and 1.8 g were not significant. Tensiometer readings tracked pressure differences due to the hydrostatic force changes with variable gravity. The readings may have been affected by changes in cabin air pressure that occurred during each parabola. Tensiometer porous membrane conductivity (function of pore size) and fluid volume both influence response time. Porous media sample height and water content influence time-to-equilibrium, where shorter samples and higher water content achieve faster equilibrium. Further testing is needed to develop these sensors for space flight applications. PMID:15751144

  13. Porous media matric potential and water content measurements during parabolic flight

    NASA Technical Reports Server (NTRS)

    Norikane, Joey H.; Jones, Scott B.; Steinberg, Susan L.; Levine, Howard G.; Or, Dani

    2005-01-01

    Control of water and air in the root zone of plants remains a challenge in the microgravity environment of space. Due to limited flight opportunities, research aimed at resolving microgravity porous media fluid dynamics must often be conducted on Earth. The NASA KC-135 reduced gravity flight program offers an opportunity for Earth-based researchers to study physical processes in a variable gravity environment. The objectives of this study were to obtain measurements of water content and matric potential during the parabolic profile flown by the KC-135 aircraft. The flight profile provided 20-25 s of microgravity at the top of the parabola, while pulling 1.8 g at the bottom. The soil moisture sensors (Temperature and Moisture Acquisition System: Orbital Technologies, Madison, WI) used a heat-pulse method to indirectly estimate water content from heat dissipation. Tensiometers were constructed using a stainless steel porous cup with a pressure transducer and were used to measure the matric potential of the medium. The two types of sensors were placed at different depths in a substrate compartment filled with 1-2 mm Turface (calcined clay). The ability of the heat-pulse sensors to monitor overall changes in water content in the substrate compartment decreased with water content. Differences in measured water content data recorded at 0, 1, and 1.8 g were not significant. Tensiometer readings tracked pressure differences due to the hydrostatic force changes with variable gravity. The readings may have been affected by changes in cabin air pressure that occurred during each parabola. Tensiometer porous membrane conductivity (function of pore size) and fluid volume both influence response time. Porous media sample height and water content influence time-to-equilibrium, where shorter samples and higher water content achieve faster equilibrium. Further testing is needed to develop these sensors for space flight applications.

  14. A 3-D constitutive model for pressure-dependent phase transformation of porous shape memory alloys.

    PubMed

    Ashrafi, M J; Arghavani, J; Naghdabadi, R; Sohrabpour, S

    2015-02-01

    Porous shape memory alloys (SMAs) exhibit the interesting characteristics of porous metals together with shape memory effect and pseudo-elasticity of SMAs that make them appropriate for biomedical applications. In this paper, a 3-D phenomenological constitutive model for the pseudo-elastic behavior and shape memory effect of porous SMAs is developed within the framework of irreversible thermodynamics. Comparing to micromechanical and computational models, the proposed model is computationally cost effective and predicts the behavior of porous SMAs under proportional and non-proportional multiaxial loadings. Considering the pressure dependency of phase transformation in porous SMAs, proper internal variables, free energy and limit functions are introduced. With the aim of numerical implementation, time discretization and solution algorithm for the proposed model are also presented. Due to lack of enough experimental data on multiaxial loadings of porous SMAs, we employ a computational simulation method (CSM) together with available experimental data to validate the proposed constitutive model. The method is based on a 3-D finite element model of a representative volume element (RVE) with random pores pattern. Good agreement between the numerical predictions of the model and CSM results is observed for elastic and phase transformation behaviors in various thermomechanical loadings. PMID:25528691

  15. Modeling thermochemical heat storage in porous media with local thermal nonequilibrium - From constitutive theory to application

    NASA Astrophysics Data System (ADS)

    Nagel, T.; Shao, H.; Linder, M.; Wörner, A.; Kolditz, O.

    2013-12-01

    Heat processes in industry and for power generation can be made more cost-efficient and climate friendly by the integration of thermal energy storage devices. Due to high storage densities and superior long term storage characteristics, systems relying on thermochemical reactions are of great interest and often based on porous or granular media. As such, they share characteristic features in terms of mass and heat transport that are strongly coupled by physical and chemical phenomena. We have employed the theory of porous media to establish a model featuring reactive multicomponent compressible fluid mass transport through solid particle bed coupled to local thermal nonequilibrium heat transport. The model development has been based on an extensive evaluation of the Clausius-Duhem inequality to derive thermodynamically consistent constitutive relations for secondary variables as well as direct and indirect coupling terms. The model has then been implemented into the open source scientific simulation code OpenGeoSys using the finite element method. Lab and pilot scale thermochemical heat storage reactors with different reaction systems (oxidation reactions, hydration reactions) have been simulated successfully using axisymmetric geometries. The simulations show the strong coupling of pressure, concentration and temperature fields as well as the gas-solid reactions occurring inside the reactors. The effect of certain process parameters, such as mass flow and particle size, on the occurrence of local thermal nonequilibrium is illustrated. It is shown that the reactors can be used in a number of operating modes such as the extraction or release of heat accompanied by significant temperature drops or raises; the buffering or smoothing of temperature fluctuations at the inlet; the up- or downgrading of heat. The developed model therefore represents a useful tool to understand reactor behavior, optimize operating parameters, estimate thermal and parasitic losses, and

  16. Encapsulation of protein molecules in transparent porous silica matrices via an aqueous colloidal sol-gel process

    SciTech Connect

    Liu, D.M.; Chen, I.W.

    1999-12-10

    Encapsulation of several biologically important proteins, cytochrome c, catalase, myoglobin, and hemoglobin, into transparent porous silica matrices by an aqueous colloidal sol-gel process that requires no alcohol is reported. Optical characterization indicates a successful retention of protein conformation after encapsulation. The conformation retention is strongly correlated to both the rate of gelation and the subsequent drying speed. Using hemoglobin as a model protein, a higher colloidal solid concentration and a lower synthesis pH were found, both causing faster gelation, resulting in a better retention of conformation. Hemoglobin encapsulated in a thin film, which dries faster, also showed a better retention than in the bulk. This is attributed to the fact that when a protein is isolated, and especially when it is confined to a space close to its own dimensions, conformational changes are sterically hindered, hence the structural stability. Enzymatic activity of bovine liver catalase was also monitored and showed a remarkable improvement when encapsulated using the aqueous colloidal process, compared to using the conventional alkoxide-based process. Thus, the aqueous colloidal sol-gel process offers a promising alternative to the conventional sol-gel process for encapsulating biomolecules into transparent, porous matrices.

  17. The Pressurized Porous Surface Model: an improved tool to study bacterial behavior under a wide range of environmentally relevant matric potentials.

    PubMed

    Gülez, Gamze; Dechesne, Arnaud; Smets, Barth F

    2010-09-01

    To study bacterial behavior under varying hydration conditions similar to surface soil, we have developed a system called the Pressurized Porous Surface Model (PPSM). Thin liquid films created by imposing a matric potential of -0.4 MPa impact gene expression and colony development in Pseudomonas putida. PMID:20599568

  18. Computer-Aided Process Planning for the Layered Fabrication of Porous Scaffold Matrices

    NASA Astrophysics Data System (ADS)

    Starly, Binil

    Rapid Prototyping (RP) technology promises to have a tremendous impact on the design and fabrication of porous tissue replacement structures for applications in tissue engineering and regenerative medicine. The layer-by-layer fabrication technology enables the design of patient-specific medical implants and complex structures for diseased tissue replacement strategies. Combined with advancements in imaging modalities and bio-modeling software, physicians can engage themselves in advanced solutions for craniofacial and mandibular reconstruction. For example, prior to the advancement of RP technologies, solid titanium parts used as implants for mandibular reconstruction were fashioned out of molding or CNC-based machining processes (Fig. 3.1). Titanium implants built using this process are often heavy, leading to increased patient discomfort. In addition, the Young's modulus of titanium is almost five times that of healthy cortical bone resulting in stress shielding effects [1,2]. With the advent of CAD/CAM-based tools, the virtual reconstruction of the implants has resulted in significant design improvements. The new generation of implants can be porous, enabling the in-growth of healthy bone tissue for additional implant fixation and stabilization. Newer implants would conform to the external shape of the defect site that is intended to be filled in. More importantly, the effective elastic modulus of the implant can be designed to match that of surrounding tissue. Ideally, the weight of the implant can be designed to equal the weight of the tissue that is being replaced resulting in increased patient comfort. Currently, such porous structures for reconstruction can only be fabricated using RP-based metal fabrication technologies such as Electron Beam Melting (EBM), Selective Laser Sintering (SLS®), and 3D™ Printing processes.

  19. Development and assessment of two-phase porous matrices for use in all-oxide ceramic composites

    NASA Astrophysics Data System (ADS)

    Fujita, Hiroki

    The study focuses on a class of all-oxide continuous-fiber ceramic composite (CFCC) in which damage tolerance is derived from a highly-porous matrix, without an interphase at the fiber-matrix boundary. It includes experiments and analyses on both a representative oxide CFCC (developed earlier at UCSB) and a series of alumina-mullite matrices. The first part of the thesis addresses the stability of the porosity against densification and the associated implications for long-term durability at elevated temperatures. For this purpose, changes in the mechanical properties of the CFCC following 1000 hour exposure at 1000--1200°C were examined. Despite evidence of some strengthening of the matrix, the tensile properties in the 0°/90° orientation, including strength and failure strain, are unchanged. This strengthening is manifested to a more significant extent in the composite properties in the +/-45° orientation. The remainder of the thesis focuses on the assessment of weakly bonded mixtures of mullite and alumina as candidate matrices. Stability against densification is accomplished by using mullite particles as the major phase. This stability arises from the sluggish sintering kinetics of mullite. The matrix is strengthened by adding alumina, either as small particulates in the starting slurry or by subsequent impregnation and pyrolysis of a precursor solution. The modulus and the toughness of both types of mixtures as well as the changes in these properties following aging at 1200°C are examined. Models based on bonded particle aggregates are presented, assessed and calibrated. When coupled with a crack deflection parameter, the models are useful in determining the conditions under which damage tolerance is lost, because of excessive strengthening of the matrix. The implications of these results in matrix design are discussed.

  20. PARAMETRIC MODEL FOR CONSTITUTIVE PROPERTIES GOVERNING MULTIPHASE FLOW IN POROUS MEDIA

    EPA Science Inventory

    A parametric model is developed to describe relative permeability-saturation-fluid pressure functional relationships in two- or three-fluid phase porous media systems subject to monotonic saturation paths. All functions are obtained as simple closed-form expressions convenient fo...

  1. Encapsulation of biomaterials in porous glass-like matrices prepared via an aqueous colloidal sol-gel process

    DOEpatents

    Liu, Dean-Mo; Chen, I-Wei

    2001-01-01

    The present invention provides a process for the encapsulation of biologically important proteins into transparent, porous silica matrices by an alcohol-free, aqueous, colloidal sol-gel process, and to the biological materials encapsulated thereby. The process is exemplified by studies involving encapsulated cytochrome c, catalase, myoglobin, and hemoglobin, although non-proteinaceous biomaterials, such as active DNA or RNA fragments, cells or even tissues, may also be encapsulated in accordance with the present methods. Conformation, and hence activity of the biomaterial, is successfully retained after encapsulation as demonstrated by optical characterization of the molecules, even after long-term storage. The retained conformation of the biomaterial is strongly correlated to both the rate of gelation and the subsequent drying speed of the encapsulatng matrix. Moreover, in accordance with this process, gelation is accelerated by the use of a higher colloidal solid concentration and a lower synthesis pH than conventional methods, thereby enhancing structural stability and retained conformation of the biomaterials. Thus, the invention also provides a remarkable improvement in retaining the biological activity of the encapsulated biomaterial, as compared with those involved in conventional alkoxide-based processes. It further provides new methods for the quantitative and qualitative detection of test substances that are reactive to, or catalyzed by, the active, encapsulated biological materials.

  2. Constitutive model for geological and other porous materials under dynamic loading

    SciTech Connect

    Dey, T.N.

    1991-01-01

    An effective stress model is described for use in numerical calculations on porous materials which are partially or fully saturated with water. The flow rule chosen for the shear failure portion of the model is examined and shown to have significant influence on wave propagation results. A flow rule which produces dilatancy results in less attenuation than a rule producing shear-enhanced void collapse. The dilatancy producing rule is less prone to producing liquefaction and results in significantly higher stress levels behind the wave front. 8 refs., 6 figs.

  3. Lower-bound and Upper-bound Rigid-plastic Constitutive Models for Porous Materials:Comparison and Examination

    NASA Astrophysics Data System (ADS)

    Yin, Yajun; Xue, Mingde; Yu, Shouwen

    A lower bound rigid plastic constitutive model for porous materials has been published recently, but its reliability and accuracy is still kept unknown. Therefore, this paper is confined to examine this model by comparing it with other ones such as the upper bound one and experimental-based one. Under three loading states (i.e. uniaxial stress condition, biaxial equal stress condition and uniaxial strain condition), the sintered copper’s ductility, compressibility, strength property, deformation characteristics, stress˜strain curves and damage evolution process predicted by these models are systematically compared. The advantage of the lower bound model in describing the yield property and its limitations in evaluating the ductility, compressibility, strength variation and damage evolution process of porous materials are clarified. Systematical analysis reveals that these limitations may be attributed to the short of void interaction mechanism in the lower bound model. This discovery lays the foundation for further improvement and modification of the lower bound model in the future research.

  4. Electroluminescent layers based on ZnS:Cu deposited into matrices of porous anodic Al2O3

    NASA Astrophysics Data System (ADS)

    Valeev, R. G.; Petukhov, D. I.; Chukavin, A. I.; Bel'tyukov, A. N.

    2016-02-01

    It is suggested to use a new nanocomposite material—nanostructures of copper-doped zinc sulfide in a matrix of porous aluminum oxide—as a light-emitting layer of electroluminescent sources of light. The material was deposited by thermal evaporation in a vacuum. The microstructure of the layers, impurity distribution in the electroluminescent-phosphor layer, and electroluminescence spectra at various copper concentrations in ZnS:Cu were studied.

  5. An injection molding process for manufacturing highly porous and interconnected biodegradable polymer matrices for use as tissue engineering scaffolds.

    PubMed

    Kramschuster, Adam; Turng, Lih-Sheng

    2010-02-01

    In this research, injection molding was combined with a novel material combination, supercritical fluid processing, and particulate leaching techniques to produce highly porous and interconnected structures that have the potential to act as scaffolds for tissue engineering applications. The foamed structures, molded with polylactide (PLA) and polyvinyl alcohol (PVOH) with salt as the particulate, were processed without the aid of organic solvents, which can be detrimental to tissue growth. The pore size in the scaffolds is controlled by salt particulates and interconnectivity is achieved by the co-continuous blending morphology of biodegradable PLA matrix with water-soluble PVOH. Carbon dioxide (CO(2)) at the supercritical state is used to serve as a plasticizer, thereby imparting moldability of blends even with an ultra high salt particulate content, and allows the use of low processing temperatures, which are desirable for temperature-sensitive biodegradable polymers. Interconnected pores of approximately 200 microm in diameter and porosities of approximately 75% are reported and discussed. PMID:19957359

  6. Constitution and in vivo test of micro-porous tubular scaffold for esophageal tissue engineering.

    PubMed

    Hou, Lei; Jin, Jiachang; Lv, Jingjing; Chen, Ling; Zhu, Yabin; Liu, Xingyu

    2015-11-01

    Current clinical techniques in treating long-gap esophageal defects often lead to complications and high morbidity. Aiming at long-gap synthetic esophageal substitute, we had synthesized a biodegradable copolymer, poly(L-lactide-co-caprolactone) (PLLC), with low glass transition temperature. In this work, we developed a tubular PLLC porous scaffold using a self-designed tubular mold and thermal induced phase separation (TIPS) method. In order to enhance the interaction between tissue and scaffold, fibrin, a natural fibrous protein derived from blood fibrinogen, was coated on the scaffold circumferential surface. The fibrin density was measured to be 1.23 ± 0.04 mg/cm(2). Primary epithelial cell culture demonstrated the improved in vitro biocompatibility. In animal study with partial scaffold implantation, in situ mucosa regeneration was observed along the degradation of the scaffold. These indicate that fibrin incorporated PLLC scaffold can greatly improve epithelial regeneration in esophagus repair, therefore serve as a good candidate for long-term evaluation of post-implantation at excision site. PMID:26208515

  7. Compound matrices

    NASA Astrophysics Data System (ADS)

    Kravvaritis, Christos; Mitrouli, Marilena

    2009-02-01

    This paper studies the possibility to calculate efficiently compounds of real matrices which have a special form or structure. The usefulness of such an effort lies in the fact that the computation of compound matrices, which is generally noneffective due to its high complexity, is encountered in several applications. A new approach for computing the Singular Value Decompositions (SVD's) of the compounds of a matrix is proposed by establishing the equality (up to a permutation) between the compounds of the SVD of a matrix and the SVD's of the compounds of the matrix. The superiority of the new idea over the standard method is demonstrated. Similar approaches with some limitations can be adopted for other matrix factorizations, too. Furthermore, formulas for the n - 1 compounds of Hadamard matrices are derived, which dodge the strenuous computations of the respective numerous large determinants. Finally, a combinatorial counting technique for finding the compounds of diagonal matrices is illustrated.

  8. A constitutive model for air-NAPL-water flow in the vadose zone accounting for immobile, non-occluded (residual) NAPL in strongly water-wet porous media

    SciTech Connect

    Lenhard, Robert J.; Oostrom, Mart; Dane, J H.

    2004-07-01

    A hysteretic constitutive model describing relations among relative permeabilities, saturations, and pressures in fluid systems consisting of air, nonaqueous-phase liquid (NAPL), and water is modified to account for NAPL that is postulated to be immobile in small pores and pore wedges and as films or lenses on water surfaces. A direct outcome of the model is prediction of the NAPL saturation that remains in the vadose zone after long drainage periods (residual NAPL). Using the modified model, water and NAPL (free, trapped by water, and residual) saturations can be predicted from the capillary pressures and the water and total-liquid saturation-path histories. Relations between relative permeabilities and saturations are modified to account for the residual NAPL by adjusting the limits of integration in the integral expression used for predicting the NAPL relative permeability. When all of the NAPL is either residual or trapped (i.e., no free NAPL), then the NAPL relative permeability will be zero. We model residual NAPL using concepts similar to those used to model residual water. As an initial test of the constitutive model, we compare predictions to published measurements of residual NAPL. Furthermore, we present results using the modified constitutive theory for a scenario involving NAPL imbibition and drainage.

  9. A Constitutive Model for Air-NAPL-Water Flow in the Vadose Zone Accounting for Immobile, Non-Occluded (Residual) NAPL in Strongly Water-Wet Porous Media

    SciTech Connect

    R. J. Lenhard; M. Oostrom; J. H. Dane

    2004-07-01

    A hysteretic constitutive model describing relations among relative permeabilities, saturations, and pressures in fluid systems consisting of air, nonaqueous-phase liquid (NAPL), and water is modified to account for NAPL that is postulated to be immobile in small pores and pore wedges and as films or lenses on water surfaces. A direct outcome of the model is prediction of the NAPL saturation that remains in the vadose zone after long drainage periods (residual NAPL). Using the modified model, water and NAPL (free, entrapped by water, and residual) saturations can be predicted from the capillary pressures and the water and total-liquid saturation-path histories. Relations between relative permeabilities and saturations are modified to account for the residual NAPL by adjusting the limits of integration in the integral expression used for predicting the NAPL relative permeability. When all of the NAPL is either residual or entrapped (i.e., no free NAPL), then the NAPL relative permeability will be zero. We model residual NAPL using concepts similar to those used to model residual water. As an initial test of the constitutive model, we compare predictions to published measurements of residual NAPL. Furthermore, we present results using the modified constitutive theory for a scenario involving NAPL imbibition and drainage.

  10. A constitutive model for air-NAPL-water flow in the vadose zone accounting for immobile, non-occluded (residual) NAPL in strongly water-wet porous media

    SciTech Connect

    Lenhard, Robert J.; Oostrom, Mart; Dane, J H.

    2004-09-01

    A hysteretic constitutive model describing relations among relative permeabilities, saturations, and pressures in fluid systems consisting of air, nonaqueous-phase liquid (NAPL), and water is modified to account for NAPL that is postulated to be immobile in small pores and pore wedges and as films or lenses on water surfaces. A direct outcome of the model is prediction of the NAPL saturation that remains in the vadose zone after long drainage periods (residual NAPL). Using the modified model, water and NAPL (free, entrapped by water, and residual) saturations can be predicted from the capillary pressures and the water and total-liquid saturation-path histories. Relations between relative permeabilities and saturations are modified to account for the residual NAPL by adjusting the limits of integration in the integral expression used for predicting the NAPL relative permeability. When all of the NAPL is either residual or entrapped (i.e., no free NAPL), then the NAPL relative permeability will be zero. We model residual NAPL using concepts similar to those used to model residual water. As an initial test of the constitutive model, we compare predictions to published measurements of residual NAPL. Furthermore, we present results using the modified constitutive theory for a scenario involving NAPL imbibition and drainage.

  11. Stiffness and mass matrices for shells of revolution (SAMMSOR II)

    NASA Technical Reports Server (NTRS)

    Tillerson, J. R.; Haisler, W. E.

    1974-01-01

    Utilizing element properties, structural stiffness and mass matrices are generated for as many as twenty harmonics and stored on magnetic tape. Matrices generated constitute input data to be used by other stiffness of revolution programs. Variety of boundary and loading conditions can be employed without having to create new mass and stiffness matrices for each case.

  12. Synbiotic matrices derived from plant oligosaccharides and polysaccharides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A porous synbiotic matrix was prepared by lyophilization of alginate and pectin or fructan oligosaccharides and polysaccharides cross-linked with calcium. These synbiotic matrices were excellent physical structures to support the growth of Lactobacillus acidophilus (1426) and Lactobacillus reuteri (...

  13. Constitutional Conservatism

    ERIC Educational Resources Information Center

    Berkowitz, Peter

    2009-01-01

    After their dismal performance in election 2008, conservatives are taking stock. As they examine the causes that have driven them into the political wilderness and as they explore paths out, they should also take heart. After all, election 2008 shows that America's constitutional order is working as designed. Indeed, while sorting out their errors…

  14. Surface enhanced fluorescence of anti-tumoral drug emodin adsorbed on silver nanoparticles and loaded on porous silicon

    PubMed Central

    2012-01-01

    Fluorescence spectra of anti-tumoral drug emodin loaded on nanostructured porous silicon have been recorded. The use of colloidal nanoparticles allowed embedding of the drug without previous porous silicon functionalization and leads to the observation of an enhancement of fluorescence of the drug. Mean pore size of porous silicon matrices was 60 nm, while silver nanoparticles mean diameter was 50 nm. Atmospheric and vacuum conditions at room temperature were used to infiltrate emodin-silver nanoparticles complexes into porous silicon matrices. The drug was loaded after adsorption on metal surface, alone, and bound to bovine serum albumin. Methanol and water were used as solvents. Spectra with 1 μm spatial resolution of cross-section of porous silicon layers were recorded to observe the penetration of the drug. A maximum fluorescence enhancement factor of 24 was obtained when protein was loaded bound to albumin, and atmospheric conditions of inclusion were used. A better penetration was obtained using methanol as solvent when comparing with water. Complexes of emodin remain loaded for 30 days after preparation without an apparent degradation of the drug, although a decrease in the enhancement factor is observed. The study reported here constitutes the basis for designing a new drug delivery system with future applications in medicine and pharmacy. PMID:22748115

  15. Higher dimensional Hadamard matrices

    NASA Technical Reports Server (NTRS)

    Schlichta, P. J.

    1979-01-01

    The paper defines higher dimensional Hadamard matrices and enumerates on some of the simplest three-, four-, and five-dimensional cases and procedures for generating them. Special emphasis is given to proper matrices that have a dimensional hierarchy of orthogonalities. It is determined that this property lends itself primarily to the application of higher dimensional Hadamard matrices to error-correcting codes. A list of derived statements for n-dimensional Hadamard matrices are given, as well as a definition of Hadamard matrix families, such as minimal, Petrie polygon, antipodal (n-2)-dimensional sections, and double proximity shells.

  16. What Is a Constitution?

    ERIC Educational Resources Information Center

    OAH Magazine of History, 1988

    1988-01-01

    Provides a lesson plan designed to help students better understand the concept of a constitution, distinguish constitutional law from statutory law, and recognize examples of constitutional government. (BSR)

  17. Optical detection of parasitic protozoa in sol-gel matrices

    NASA Astrophysics Data System (ADS)

    Livage, Jacques; Barreau, J. Y.; Da Costa, J. M.; Desportes, I.

    1994-10-01

    Whole cell parasitic protozoa have been entrapped within sol-gel porous silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silica sol before gelation occurs. They remain trapped within the growing oxide network and their cellular organization appears to be well preserved. Moreover protozoa retain their antigenic properties in the porous gel. They are still able to detect parasite specific antibodies in serum samples from infected patients via an enzyme linked immunosorbent assay (ELISA). Antigen- antibody associations occurring in the gel are optically detected via the reactions of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. A clear-cut difference in optical density is measured between positive and negative sera. Such an entrapment of antigenic species into porous sol-gel matrices avoids the main problems due to non specific binding and could be advantageously used in diagnostic kits.

  18. Calibration and temperature correction of heat dissipation matric potential sensors

    USGS Publications Warehouse

    Flint, A.L.; Campbell, G.S.; Ellett, K.M.; Calissendorff, C.

    2002-01-01

    This paper describes how heat dissipation sensors, used to measure soil water matric potential, were analyzed to develop a normalized calibration equation and a temperature correction method. Inference of soil matric potential depends on a correlation between the variable thermal conductance of the sensor's porous ceramic and matric poten-tial. Although this correlation varies among sensors, we demonstrate a normalizing procedure that produces a single calibration relationship. Using sensors from three sources and different calibration methods, the normalized calibration resulted in a mean absolute error of 23% over a matric potential range of -0.01 to -35 MPa. Because the thermal conductivity of variably saturated porous media is temperature dependent, a temperature correction is required for application of heat dissipation sensors in field soils. A temperature correction procedure is outlined that reduces temperature dependent errors by 10 times, which reduces the matric potential measurement errors by more than 30%. The temperature dependence is well described by a thermal conductivity model that allows for the correction of measurements at any temperature to measurements at the calibration temperature.

  19. Enzymatic Biofuel Cells on Porous Nanostructures.

    PubMed

    Wen, Dan; Eychmüller, Alexander

    2016-09-01

    Biofuel cells (BFCs) that utilize enzymes as catalysts represent a new sustainable and renewable energy technology. Numerous efforts have been directed to improve the performance of the enzymatic BFCs (EBFCs) with respect to power output and operational stability for further applications in portable power sources, self-powered electrochemical sensing, implantable medical devices, etc. The latest advances in EBFCs based on porous nanoarchitectures over the past 5 years are detailed here. Porous matrices from carbon, noble metals, and polymers promote the development of EBFCs through the electron transfer and mass transport benefits. Some key issues regarding how these nanostructured porous media improve the performance of EBFCs are also discussed. PMID:27377976

  20. The Constitutional Amendment Process

    ERIC Educational Resources Information Center

    Chism, Kahlil

    2005-01-01

    This article discusses the constitutional amendment process. Although the process is not described in great detail, Article V of the United States Constitution allows for and provides instruction on amending the Constitution. While the amendment process currently consists of six steps, the Constitution is nevertheless quite difficult to change.…

  1. Frequency filtering decompositions for unsymmetric matrices and matrices with strongly varying coefficients

    SciTech Connect

    Wagner, C.

    1996-12-31

    In 1992, Wittum introduced the frequency filtering decompositions (FFD), which yield a fast method for the iterative solution of large systems of linear equations. Based on this method, the tangential frequency filtering decompositions (TFFD) have been developed. The TFFD allow the robust and efficient treatment of matrices with strongly varying coefficients. The existence and the convergence of the TFFD can be shown for symmetric and positive definite matrices. For a large class of matrices, it is possible to prove that the convergence rate of the TFFD and of the FFD is independent of the number of unknowns. For both methods, schemes for the construction of frequency filtering decompositions for unsymmetric matrices have been developed. Since, in contrast to Wittums`s FFD, the TFFD needs only one test vector, an adaptive test vector can be used. The TFFD with respect to the adaptive test vector can be combined with other iterative methods, e.g. multi-grid methods, in order to improve the robustness of these methods. The frequency filtering decompositions have been successfully applied to the problem of the decontamination of a heterogeneous porous medium by flushing.

  2. Singular Mueller matrices

    NASA Astrophysics Data System (ADS)

    Gil, José J.; Ossikovski, Razvigor; José, Ignacio San

    2016-04-01

    Singular Mueller matrices play an important role in polarization algebra and have peculiar properties that stem from the fact that either the medium exhibits maximum diattenuation and/or polarizance, or because its associated canonical depolarizer has the property of fully randomizing, the circular component (at least) of the states of polarization of light incident on it. The formal reasons for which the Mueller matrix M of a given medium is singular are systematically investigated, analyzed and interpreted in the framework of the serial decompositions and the characteristic ellipsoids of M. The analysis allows for a general classification and geometric representation of singular Mueller matrices, of potential usefulness to experimentalists dealing with such media.

  3. Singular Mueller matrices.

    PubMed

    Gil, José J; Ossikovski, Razvigor; José, Ignacio San

    2016-04-01

    Singular Mueller matrices play an important role in polarization algebra and have peculiar properties that stem from the fact that either the medium exhibits maximum diattenuation and/or polarizance or because its associated canonical depolarizer has the property of fully randomizing the circular component (at least) of the states of polarization of light incident on it. The formal reasons for which the Mueller matrix M of a given medium is singular are systematically investigated, analyzed, and interpreted in the framework of the serial decompositions and the characteristic ellipsoids of M. The analysis allows for a general classification and geometric representation of singular Mueller matrices, which are of potential usefulness to experimentalists dealing with such media. PMID:27140769

  4. Shear representations of beam transfer matrices.

    PubMed

    Başkal, S; Kim, Y S

    2001-05-01

    The beam transfer matrix, often called the ABCD matrix, is one of the essential mathematical instruments in optics. It is a unimodular matrix whose determinant is 1. If all the elements are real with three independent parameters, this matrix is a 2 x 2 representation of the group Sp(2). It is shown that a real ABCD matrix can be generated by two shear transformations. It is then noted that, in para-axial lens optics, the lens and translation matrices constitute two shear transformations. It is shown that a system with an arbitrary number of lenses can be reduced to a system consisting of three lenses. PMID:11415030

  5. Porous bioactive materials

    NASA Astrophysics Data System (ADS)

    Zhang, Kai

    Bioactive materials chemically bond to tissues through the development of biologically active apatite. Porous structures in biomaterials are designed to enhance bioactivity, grow artificial tissues and achieve better integration with host tissues in the body. The goal of this research is to design, fabricate and characterize novel porous bioactive materials. 3D ordered macroporous bioactive glasses (3DOM-BGs, pore size: 200--1000 nm) were prepared using a sol-gel process and colloidal crystal templates. 3DOM-BGs are more bioactive and degradable than mesoporous (pore size <50 nm) sol-gel BGs in simulated body fluid (SBF). Apatite formation and 3DOM-BG degradation rates increased with the decrease of soaking ratio. Apatite induction time in SBF increased with 3DOM-BG calcination temperature (600--800°C). Apatite formation and 3DOMBG degradation were slightly enhanced for a phosphate containing composition. Large 3DOM-BG particles formed less apatite and degraded less completely as compared with small particles. An increase in macropore size slowed down 3DOM-BG degradation and apatite formation processes. After heating the converted apatite at a temperature higher than 700°C, highly crystalline hydroxyapatite and a minor tri-calcium phosphate phase formed. 3DOM-BGs have potential applications as bone/periodontal fillers, and drugs and biological factors delivery agents. Anchoring artificial soft tissues (e.g., cartilage) to native bone presents a challenge. Porous polymer/bioactive glass composites are candidate materials for engineering artificial soft tissue/bone interfaces. Porous composites consisting of polymer matrices (e.g., polysulfone, polylactide, and polyurethane) and bioactive glass particles were prepared by polymer phase separation techniques adapted to include ceramic particles. Composites (thickness: 200--500 mum) have asymmetric structures with dense top layers and porous structures beneath. Porous structures consist of large pores (>100 mum) in a

  6. The porous surface model, a novel experimental system for online quantitative observation of microbial processes under unsaturated conditions.

    PubMed

    Dechesne, Arnaud; Or, Dani; Gülez, Gamze; Smets, Barth F

    2008-08-01

    Water is arguably the most important constituent of microbial microhabitats due to its control of physical and physiological processes critical to microbial activity. In natural environments, bacteria often live on unsaturated surfaces, in thin (micrometric) liquid films. Nevertheless, no experimental systems are available that allow real-time observation of bacterial processes in liquid films of controlled thickness. We propose a novel, inexpensive, easily operated experimental platform, termed the porous surface model (PSM) that enables quantitative real-time microscopic observations of bacterial growth and activity under controlled unsaturated conditions. Bacteria are inoculated on a porous ceramic plate, wetted by a liquid medium. The thickness of the liquid film at the surface of the plate is set by imposing suction, corresponding to soil matric potential, to the liquid medium. The utility of the PSM was demonstrated using Pseudomonas putida KT2440 tagged with gfp as a model bacterium. Single cells were inoculated at the surface of the PSM, and the rate at which colonies expanded laterally was measured for three matric potentials (-0.5, -1.2, and -3.6 kPa). The matric potential exerted significant influence on colony expansion rates, with a faster rate of spreading at -0.5 than at -1.2 or -3.6 kPa (diameter increase rate, ca. 1,000, 200, and 17 microm h(-1), respectively). These differences can be attributed to cell motility, strongly limited under the most negative matric potential. The PSM constitutes a tool uniquely adapted to study the influence of liquid film geometry on microbial processes. It should therefore contribute to uncovering mechanisms of microbial adaptation to unsaturated environments. PMID:18586968

  7. The Porous Surface Model, a Novel Experimental System for Online Quantitative Observation of Microbial Processes under Unsaturated Conditions ▿ †

    PubMed Central

    Dechesne, Arnaud; Or, Dani; Gülez, Gamze; Smets, Barth F.

    2008-01-01

    Water is arguably the most important constituent of microbial microhabitats due to its control of physical and physiological processes critical to microbial activity. In natural environments, bacteria often live on unsaturated surfaces, in thin (micrometric) liquid films. Nevertheless, no experimental systems are available that allow real-time observation of bacterial processes in liquid films of controlled thickness. We propose a novel, inexpensive, easily operated experimental platform, termed the porous surface model (PSM) that enables quantitative real-time microscopic observations of bacterial growth and activity under controlled unsaturated conditions. Bacteria are inoculated on a porous ceramic plate, wetted by a liquid medium. The thickness of the liquid film at the surface of the plate is set by imposing suction, corresponding to soil matric potential, to the liquid medium. The utility of the PSM was demonstrated using Pseudomonas putida KT2440 tagged with gfp as a model bacterium. Single cells were inoculated at the surface of the PSM, and the rate at which colonies expanded laterally was measured for three matric potentials (−0.5, −1.2, and −3.6 kPa). The matric potential exerted significant influence on colony expansion rates, with a faster rate of spreading at −0.5 than at −1.2 or −3.6 kPa (diameter increase rate, ca. 1,000, 200, and 17 μm h−1, respectively). These differences can be attributed to cell motility, strongly limited under the most negative matric potential. The PSM constitutes a tool uniquely adapted to study the influence of liquid film geometry on microbial processes. It should therefore contribute to uncovering mechanisms of microbial adaptation to unsaturated environments. PMID:18586968

  8. Intermittency and random matrices

    NASA Astrophysics Data System (ADS)

    Sokoloff, Dmitry; Illarionov, E. A.

    2015-08-01

    A spectacular phenomenon of intermittency, i.e. a progressive growth of higher statistical moments of a physical field excited by an instability in a random medium, attracted the attention of Zeldovich in the last years of his life. At that time, the mathematical aspects underlying the physical description of this phenomenon were still under development and relations between various findings in the field remained obscure. Contemporary results from the theory of the product of independent random matrices (the Furstenberg theory) allowed the elaboration of the phenomenon of intermittency in a systematic way. We consider applications of the Furstenberg theory to some problems in cosmology and dynamo theory.

  9. Porous liquids: A promising class of media for gas separation

    DOE PAGESBeta

    Zhang, Jinshui; Chai, Song -Hai; Qiao, Zhen -An; Mahurin, Shannon M.; Chen, Jihua; Fang, Youxing; Wan, Shun; Nelson, Kimberly; Zhang, Pengfei; Dai, Sheng

    2014-11-17

    In porous liquids with empty cavities we successfully has been successfully fabricated by surface engineering of hollow structures with suitable corona and canopy species. By taking advantage of the liquid-like polymeric matrices as a separation medium and the empty cavities as gas transport pathway, this unique porous liquid can function as a promising candidate for gas separation. A facile synthetic strategy can be further extended to other types of nanostructure-based porous liquid fabrication, opening up new opportunities for preparation of porous liquids with attractive properties for specific tasks.

  10. Novel Factor-loaded Polyphosphazene Matrices

    PubMed Central

    Oredein-McCoy, Olugbemisola; Krogman, Nicholas R.; Weikel, Arlin L.; Hindenlang, Mark D.; Allcock, Harry R.; Laurencin, Cato T.

    2009-01-01

    Currently employed bone tissue engineered scaffolds often lack the potential for vascularization, which may be enhanced through the incorporation of and regulated release of angiogenic factors. For this reason, our objective was to fabricate and characterize protein-loaded amino acid ester polyphosphazene (Pphos)-based scaffolds and evaluate the novel sintering method used for protein incorporation, a method which will ultimately allow for the incorporation of proangiogenic agents. To test the hypothesis, Pphos and their composite microspheres with nanocrystalline hydroxyapatite (Pphos-HAp) were fabricated via the emulsion solvent evaporation method. Next, bovine serum albumin (BSA)-containing microsphere matrices were created using a novel solvent-non solvent approach for protein loading. The resulting protein (BSA) loaded-circular porous microsphere based scaffolds were characterized for morphology, porosity, protein structure, protein distribution, and subsequent protein release pattern. Scanning electron microscopy revealed porous microsphere scaffolds with a smooth surface and sufficient level of sintering, illustrated by fusion of adjacent microspheres. The porosity measured for the PNPhGly and PNPhGly-HAp scaffolds were 23 +/- 0.11% and 18+/- 4.02%, respectively, and within the range of trabecular bone. Circular dichroism confirmed an intact secondary protein structure for BSA following the solvent sintering method used for loading, and confocal microscopy verified that FITC-BSA was successfully entrapped both between adjacent microspheres and within the surface of the microspheres while sintering. For both Pphos and their composite microsphere scaffolds, BSA was released at a steady rate over a 21day time period, following a zero order release profile. HAp particles in the composite scaffolds served to improve the release profile pattern, underscoring the potential of HAp for growth factor delivery. Moreover, the results of this work suggests that the

  11. Interpreting the Constitution.

    ERIC Educational Resources Information Center

    Brennan, William J., Jr.

    1987-01-01

    Discusses constitutional interpretations relating to capital punishment and protection of human dignity. Points out the document's effectiveness in creating a new society by adapting its principles to current problems and needs. Considers two views of the Constitution that lead to controversy over the legitimacy of judicial decisions. (PS)

  12. Teaching the Constitution.

    ERIC Educational Resources Information Center

    Weatherman, Donald V.

    1987-01-01

    Courses on the Constitution must focus on the principles of government. Those principles and how the understanding of those principles shaped the document are appropriate subjects for consideration. The best sources for an examination of the Constitution are "The Records of the Federal Convention of 1787" and "The Federalist." (MLW)

  13. Constitution of the AFT.

    ERIC Educational Resources Information Center

    American Federation of Teachers, Washington, DC.

    This document contains the constitution and the bylaws of the American Federation of Teachers. The constitution is comprised of 12 articles which deal with the name and objectives of the organization, membership, chartering of state and local units, federation officers, the Executive Council, conventions, representation of state and local units at…

  14. The Constitution by Cell

    ERIC Educational Resources Information Center

    Greenhut, Stephanie; Jones, Megan

    2010-01-01

    On their visit to the National Archives Experience in Washington, D.C., students in Jenni Ashley and Gay Brock's U.S. history classes at the Potomac School in McLean, Virginia, participated in a pilot program called "The Constitution by Cell." Armed with their cell phones, a basic understanding of the Constitution, and a willingness to participate…

  15. Enhancing Understanding of Transformation Matrices

    ERIC Educational Resources Information Center

    Dick, Jonathan; Childrey, Maria

    2012-01-01

    With the Common Core State Standards' emphasis on transformations, teachers need a variety of approaches to increase student understanding. Teaching matrix transformations by focusing on row vectors gives students tools to create matrices to perform transformations. This empowerment opens many doors: Students are able to create the matrices for…

  16. Micromechanical analysis of porous SMA

    NASA Astrophysics Data System (ADS)

    Sepe, V.; Auricchio, F.; Marfia, S.; Sacco, E.

    2015-08-01

    The present paper deals with computational micromechanical analyses of porous shape memory alloy (SMA). Porous SMAs are considered composite materials made of a dense SMA matrix including voids. A three-dimensional constitutive law is presented for the dense SMA able to reproduce the pseudo-elastic as well as the shape memory effects and, moreover, to account for the different elastic properties of the austenite and martensite phases. Furthermore, a numerical procedure is developed and the overall behavior of the porous SMA is recovered studying a representative volume element. Comparisons between the numerical results, recovered using the proposed modeling, and experimental data available in the literature are presented. The case of closed and open porosity is investigated. Parametric studies have been conducted in order to investigate the influence of the porosity, the shape and orientation of the pores on the overall mechanical response and, mainly, on the energy absorption dissipation capability.

  17. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-08-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/sqrt{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/sqrt{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example, we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  18. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-05-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/√{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/√{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  19. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-08-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/√{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/√{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example, we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  20. Numerical inversion of finite Toeplitz matrices and vector Toeplitz matrices

    NASA Technical Reports Server (NTRS)

    Bareiss, E. H.

    1969-01-01

    Numerical technique increases the efficiencies of the numerical methods involving Toeplitz matrices by reducing the number of multiplications required by an N-order Toeplitz matrix from N-cubed to N-squared multiplications. Some efficient algorithms are given.

  1. What's wrong with risk matrices?

    PubMed

    Cox, Louis Anthony

    2008-04-01

    Risk matrices-tables mapping "frequency" and "severity" ratings to corresponding risk priority levels-are popular in applications as diverse as terrorism risk analysis, highway construction project management, office building risk analysis, climate change risk management, and enterprise risk management (ERM). National and international standards (e.g., Military Standard 882C and AS/NZS 4360:1999) have stimulated adoption of risk matrices by many organizations and risk consultants. However, little research rigorously validates their performance in actually improving risk management decisions. This article examines some mathematical properties of risk matrices and shows that they have the following limitations. (a) Poor Resolution. Typical risk matrices can correctly and unambiguously compare only a small fraction (e.g., less than 10%) of randomly selected pairs of hazards. They can assign identical ratings to quantitatively very different risks ("range compression"). (b) Errors. Risk matrices can mistakenly assign higher qualitative ratings to quantitatively smaller risks. For risks with negatively correlated frequencies and severities, they can be "worse than useless," leading to worse-than-random decisions. (c) Suboptimal Resource Allocation. Effective allocation of resources to risk-reducing countermeasures cannot be based on the categories provided by risk matrices. (d) Ambiguous Inputs and Outputs. Categorizations of severity cannot be made objectively for uncertain consequences. Inputs to risk matrices (e.g., frequency and severity categorizations) and resulting outputs (i.e., risk ratings) require subjective interpretation, and different users may obtain opposite ratings of the same quantitative risks. These limitations suggest that risk matrices should be used with caution, and only with careful explanations of embedded judgments. PMID:18419665

  2. Computer-Access-Code Matrices

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1990-01-01

    Authorized users respond to changing challenges with changing passwords. Scheme for controlling access to computers defeats eavesdroppers and "hackers". Based on password system of challenge and password or sign, challenge, and countersign correlated with random alphanumeric codes in matrices of two or more dimensions. Codes stored on floppy disk or plug-in card and changed frequently. For even higher security, matrices of four or more dimensions used, just as cubes compounded into hypercubes in concurrent processing.

  3. Nanocomposites obtained by embedding of conjugated polymers in porous silicon and silica

    NASA Astrophysics Data System (ADS)

    Errien, N.; Vellutini, L.; Froyer, G.; Louarn, G.; Simos, C.; Skarka, V.; Haesaert, S.; Joubert, P.

    2005-06-01

    Porous silicon and porous silica matrices are filled up by conjugated polymers in order to obtain nanocomposite with enhanced third order optical nonlinearity. The active component is either PDA-TS thermally polymerized in situ or PT12 electropolymerized in porous silicon. The first measurements of the nonlinear properties of these nanocomposites give evidence of a significant increase of the nonlinear refractive index with respect to the standard optical materials.

  4. Constructions of Factorizable Multilevel Hadamard Matrices

    NASA Astrophysics Data System (ADS)

    Matsufuji, Shinya; Fan, Pingzhi

    Factorization of Hadamard matrices can provide fast algorithm and facilitate efficient hardware realization. In this letter, constructions of factorizable multilevel Hadamard matrices, which can be considered as special case of unitary matrices, are inverstigated. In particular, a class of ternary Hadamard matrices, together with its application, is presented.

  5. The Constitution in Action

    ERIC Educational Resources Information Center

    Potter, Lee Ann

    2007-01-01

    In this article, the author describes the experiences middle school students on a field trip to the new Constitution in Action Learning Lab in the Boeing Learning Center at the National Archives can expect. There, middle school students take on the roles of archivists and researchers collecting and analyzing primary sources from the holdings of…

  6. Constituting children's bodily integrity.

    PubMed

    Hill, B Jessie

    2015-04-01

    Children have a constitutional right to bodily integrity. Courts do not hesitate to vindicate that right when children are abused by state actors. Moreover, in at least some cases, a child's right to bodily integrity applies within the family, giving the child the right to avoid unwanted physical intrusions regardless of the parents' wishes. Nonetheless, the scope of this right vis-à-vis the parents is unclear; the extent to which it applies beyond the narrow context of abortion and contraception has been almost entirely unexplored and untheorized. This Article is the first in the legal literature to analyze the constitutional right of minors to bodily integrity within the family by spanning traditionally disparate doctrinal categories such as abortion rights; corporal punishment; medical decisionmaking; and nontherapeutic physical interventions such as tattooing, piercing, and circumcision. However, the constitutional right of minors to bodily integrity raises complex philosophical questions concerning the proper relationship between family and state, as well as difficult doctrinal and theoretical issues concerning the ever-murky idea of state action. This Article canvasses those issues with the ultimate goal of delineating a constitutional right of bodily security and autonomy for children. PMID:26016017

  7. Crushed Salt Constitutive Model

    SciTech Connect

    Callahan, G.D.

    1999-02-01

    The constitutive model used to describe the deformation of crushed salt is presented in this report. Two mechanisms -- dislocation creep and grain boundary diffusional pressure solution -- are combined to form the basis for the constitutive model governing the deformation of crushed salt. The constitutive model is generalized to represent three-dimensional states of stress. Upon complete consolidation, the crushed-salt model reproduces the Multimechanism Deformation (M-D) model typically used for the Waste Isolation Pilot Plant (WIPP) host geological formation salt. New shear consolidation tests are combined with an existing database that includes hydrostatic consolidation and shear consolidation tests conducted on WIPP and southeastern New Mexico salt. Nonlinear least-squares model fitting to the database produced two sets of material parameter values for the model -- one for the shear consolidation tests and one for a combination of the shear and hydrostatic consolidation tests. Using the parameter values determined from the fitted database, the constitutive model is validated against constant strain-rate tests. Shaft seal problems are analyzed to demonstrate model-predicted consolidation of the shaft seal crushed-salt component. Based on the fitting statistics, the ability of the model to predict the test data, and the ability of the model to predict load paths and test data outside of the fitted database, the model appears to capture the creep consolidation behavior of crushed salt reasonably well.

  8. President's Report: Constitutional Legacy.

    ERIC Educational Resources Information Center

    Tucker, Jan L.

    1987-01-01

    States that the proper business of social studies is civic education and contends that civic education must take into account the way in which global connections and uncertainties will affect citizenship in the Constitution's third century. Cites the problems associated with AIDS and the Iran-Contra affair as examples. (JDH)

  9. Sexuality and the Constitution.

    ERIC Educational Resources Information Center

    Copelon, Rhonda

    1987-01-01

    Argues for abortion rights and protection of intimate decisions and relationships. Describes the role and position of women in eighteenth century American society as a means of exposing the fallacy of the anti-abortion movement's insistence on adherence to constitutional text. Discusses the recent attempts to overturn the Roe v. Wade ruling. (PS)

  10. The Constitutional Heritage.

    ERIC Educational Resources Information Center

    Baxter, Maurice

    Changing political, social, economic, and intellectual conditions over the past two hundred years have demanded innovation and adjustment of legal doctrine, thus giving the United States Constitution a character which the framers of the document could not have predicted. Historically, one must not only understand developments since 1787 but also…

  11. Disputing the Constitution.

    ERIC Educational Resources Information Center

    Pyle, Christopher H.

    1987-01-01

    Constitutional law is a good way to introduce students to fundamental debates over means and ends, over what means work and at what costs, and over what ends are not merely desirable, but may be legitimately achieved even through the application of collective force. It also offers an exciting way to teach logic. (MLW)

  12. Constitutional Law--Elective.

    ERIC Educational Resources Information Center

    Gallagher, Joan; Wood, Robert J.

    The elective unit on Constitutional Law is intended for 11th and 12th grade students. The unit is designed around major course goals which are to develop those concepts whereby students recognize and understand the following three topic areas: 1) Role of the Federal Judicial Branch of Government, 2) Supreme Court Cases Involving the Three Branches…

  13. Biaxial constitutive equation development

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.; Walker, K. P.

    1984-01-01

    In developing the constitutive equations an interdisciplinary approach is being pursued. Specifically, both metallurgical and continuum mechanics considerations are recognized in the formulation. Experiments will be utilized to both explore general qualitative features of the material behavior that needs to be modeled and to provide a means of assessing the validity of the equations being developed. The model under development explicitly recognizes crystallographic slip on the individual slip systems. This makes possible direct representation of specific slip system phenomena. The present constitutive formulation takes the anisotropic creep theory and incorporates two state variables into the model to account for the effect of prior inelastic deformation history on the current rate-dependent response of the material.

  14. [Constitutional requirements of rationing].

    PubMed

    Kluth, Winfried

    2008-01-01

    Rationing is an emotive issue in the field of public health. This complicates the rational discourse, which is indispensable for analyzing the rationing conditions as set out by constitutional law and which requires manifold differentiation and consideration that shall briefly be outlined in the following short contribution. Of central significance is the distinction between indirect and direct rationing as well as the reference to the essential responsibility of legislators for rationing decisions. PMID:19004184

  15. Constitution, 29 March 1987.

    PubMed

    1987-01-01

    This document contains provisions of Haiti's 1987 Constitution relating to the family; the protection of children, aliens, and refugees; and individual rights. The age of majority in Haiti is 18, and political and civil rights are attained at age 21 regardless of sex or marital status. Haitians are equal before the law but native-born Haitians who have never renounced their nationality have special advantages. Human rights are guaranteed in conformity with the Universal Declaration of the Rights of Man. Every citizen has the right to decent housing, education, food, and social security. The state is obligated to provide citizens with appropriate means to protect, maintain, and restore their health. Primary schooling is compulsory and free. Aliens in Haiti enjoy the protection offered citizens, including a limited right to own real property. Political refugees have a right to asylum. The family is considered the foundation of society and enjoys state protection regardless of whether the family is constituted within the bonds of marriage. Legal protection is afforded mothers, children, and the aged. The Constitution also calls for creation of a Family Code to ensure protection and respect for the rights of the family. PMID:12346668

  16. Iterative methods for Toeplitz-like matrices

    SciTech Connect

    Huckle, T.

    1994-12-31

    In this paper the author will give a survey on iterative methods for solving linear equations with Toeplitz matrices, Block Toeplitz matrices, Toeplitz plus Hankel matrices, and matrices with low displacement rank. He will treat the following subjects: (1) optimal (w)-circulant preconditioners is a generalization of circulant preconditioners; (2) Optimal implementation of circulant-like preconditioners in the complex and real case; (3) preconditioning of near-singular matrices; what kind of preconditioners can be used in this case; (4) circulant preconditioning for more general classes of Toeplitz matrices; what can be said about matrices with coefficients that are not l{sub 1}-sequences; (5) preconditioners for Toeplitz least squares problems, for block Toeplitz matrices, and for Toeplitz plus Hankel matrices.

  17. Shrinking mechanism of a porous collagen matrix immersed in solution.

    PubMed

    Chen, Po-Yang; Hsieh, Hsyue-Jen; Huang, Lynn L H

    2014-12-01

    The porous structure of collagen-based matrices enables the infiltration of cells both in in vitro and clinical applications. Reconstituted porous collagen matrices often collapse when they are in contact with aqueous solutions; however, the mechanism for the collapse of the pores is not understood. We, therefore, investigated the interactions between the collagen matrix and different solutions, and discuss the mechanisms for the change in microstructure of the matrix on immersing it in solution. When a dried collagen matrix was immersed in aqueous solutions, the matrix shrunk and pores close to the surface closed. The shrinkage ratio and thickness of the compact microstructure close to the superficial area decreased with increasing ethanol content in the solution. The original porous structure of the collagen matrix was preserved when the matrix was immersed in absolute ethanol. The shrinkage of a porous collagen matrix in contact with aqueous solutions was attributed to the liquid/gas interfacial tension. The average pore diameter of the matrix also significantly affected the shrinkage of the matrix. The shrinkage of the matrix, explained using the Young-Laplace equation, was found to result from the pressure drop, and especially in the pores located superficially, leading to the collapse of the matrix microstructure. The integrity of the porous microstructure allows better penetration of cells in medical applications. The numbers of NIH/3T3 fibroblasts penetrated through the hydrated Col/PBS porous collagen matrices pre-immersed in absolute ethanol with subsequent water and DMEM culture medium replacements were significantly higher than those through matrices hydrated directly in DMEM. PMID:24678021

  18. The Bicentennial and State Constitutions.

    ERIC Educational Resources Information Center

    Clay, Henry

    1988-01-01

    Illustrates how the Bicentennial of the U.S. Constitution provides an opportunity to teach about the broader concept of constitutionalism through study of the state constitutions. Presents an argument for teaching about state constitutions, their role in the federal system, and the values they convey. (LS)

  19. Thomas Jefferson and the Constitution.

    ERIC Educational Resources Information Center

    Peterson, Merrill D.

    1987-01-01

    Examines Thomas Jefferson's role in the making and interpretation of the United States Constitution. Discusses the dominant features of Jefferson's constitutional theory; the character of Jefferson's presidency; and Jefferson's ongoing concern about constitutional preservation and change. Lists important dates in the history of the constitution.…

  20. Outstanding properties of bistochastic matrices

    NASA Astrophysics Data System (ADS)

    Brugia, O.; Wolfowicz, W.

    1981-10-01

    The statistical properties of many devices used in communication systems, such as scramblers and line coding and decoding devices, are described by mathematical models in which the transition probability matrix is bistochastic. To facilitate the analysis of systems response, the specific properties of the bistochastic matrices are described in six theorems which are demonstrated.

  1. Fibonacci Identities, Matrices, and Graphs

    ERIC Educational Resources Information Center

    Huang, Danrun

    2005-01-01

    General strategies used to help discover, prove, and generalize identities for Fibonacci numbers are described along with some properties about the determinants of square matrices. A matrix proof for identity (2) that has received immense attention from many branches of mathematics, like linear algebra, dynamical systems, graph theory and others…

  2. Making almost commuting matrices commute

    SciTech Connect

    Hastings, Matthew B

    2008-01-01

    Suppose two Hermitian matrices A, B almost commute ({parallel}[A,B]{parallel} {<=} {delta}). Are they close to a commuting pair of Hermitian matrices, A', B', with {parallel}A-A'{parallel},{parallel}B-B'{parallel} {<=} {epsilon}? A theorem of H. Lin shows that this is uniformly true, in that for every {epsilon} > 0 there exists a {delta} > 0, independent of the size N of the matrices, for which almost commuting implies being close to a commuting pair. However, this theorem does not specifiy how {delta} depends on {epsilon}. We give uniform bounds relating {delta} and {epsilon}. The proof is constructive, giving an explicit algorithm to construct A' and B'. We provide tighter bounds in the case of block tridiagonal and tridiagnonal matrices. Within the context of quantum measurement, this implies an algorithm to construct a basis in which we can make a projective measurement that approximately measures two approximately commuting operators simultaneously. Finally, we comment briefly on the case of approximately measuring three or more approximately commuting operators using POVMs (positive operator-valued measures) instead of projective measurements.

  3. Photoisomerization of azobenzenes isolated in cryogenic matrices.

    PubMed

    Duarte, Luís; Khriachtchev, Leonid; Fausto, Rui; Reva, Igor

    2016-06-22

    2,2'-Dihydroxyazobenzene (DAB), 2,2'-azotoluene (AT) and azobenzene (AB) were isolated in argon and xenon matrices and their molecular structures and photochemical transformations were characterized by infrared spectroscopy and theoretical calculations. All these compounds can adopt the E and Z isomeric forms around the central CNNC moiety, which can be enriched by several conformational and tautomeric modifications for DAB and AT. A number of DAB and AT isomeric forms were identified for the first time. For DAB, the E azo-enol isomer with two intramolecular six-membered quasi-rings formed via OHN hydrogen bonds was found after deposition. Irradiation with UV light generated a different E azo-enol form with two intramolecular H-bonded five-membered quasi-rings. Phototransformation was shown to be reversible and the forms could be interconverted by irradiation at different wavelengths. The isomerization between these two forms constitutes a direct experimental observation of an E → E isomerization in azobenzene-type molecules. Further irradiation generated a form(s) bearing both OH and NH groups. For AT, two E isomers with the CH3 groups forming five-membered and five/six-membered quasi-rings with the azo group were observed in the as-deposited matrices. Irradiation of AT with UV light generated a Z form that can be converted back to the E form at different irradiation wavelengths. E-AB was deposited in a xenon matrix and both E → Z and Z → E phototransformations were observed (contrary to what was previously reported in an argon matrix where only the Z → E conversion occurred). AB photoisomerization becomes more pronounced at elevated temperatures, thus indicating that the matrix effects responsible for hindering the AB photoisomerization are essentially due to steric restrictions. The different photoisomerization channels observed for these compounds are discussed in terms of a small-amplitude pedal motion. PMID:27279432

  4. A constitutive law for degrading bioresorbable polymers.

    PubMed

    Samami, Hassan; Pan, Jingzhe

    2016-06-01

    This paper presents a constitutive law that predicts the changes in elastic moduli, Poisson's ratio and ultimate tensile strength of bioresorbable polymers due to biodegradation. During biodegradation, long polymer chains are cleaved by hydrolysis reaction. For semi-crystalline polymers, the chain scissions also lead to crystallisation. Treating each scission as a cavity and each new crystal as a solid inclusion, a degrading semi-crystalline polymer can be modelled as a continuum solid containing randomly distributed cavities and crystal inclusions. The effective elastic properties of a degrading polymer are calculated using existing theories for such solid and the tensile strength of the degrading polymer is predicted using scaling relations that were developed for porous materials. The theoretical model for elastic properties and the scaling law for strength form a complete constitutive relation for the degrading polymers. It is shown that the constitutive law can capture the trend of the experimental data in the literature for a range of biodegradable polymers fairly well. PMID:26971070

  5. Constitution, 30 September 1987.

    PubMed

    1987-01-01

    This document reprints provisions of Suriname's 1987 Constitution relating to freedom of movement, equality of the sexes, the right to life, the right to physical integrity, equal opportunity in employment, the family, children, maternity benefits, the right to health care, parental responsibilities, free and compulsory education, illiteracy, and housing. All citizens enjoy freedom of movement within the bounds of the law. All people within the territory may claim protection of their person and property, and discrimination is forbidden on the basis of birth, sex, race, language, religion, education, political beliefs, economic position, or other status. Torture or inhuman treatment and punishment is banned, and the right to life is protected by the law. The state guarantees the right to work, and all employees have the right to equal remuneration for equal work, safe working conditions, and sufficient rest and recreation. The family is protected, and husbands and wives are equal before the law. Children have the right to protection, and working women are entitled to paid maternity leave. The state promotes the right to good health by systematic improvements in living and working conditions and dissemination of health education. The right to education is protected by the provision of free general primary education and efforts of the state to enable all citizens to achieve the highest educational levels possible. The Constitution also calls for the institution of a plan to allow the state to create public housing. PMID:12346681

  6. Ethics and constitutional government.

    PubMed

    Albright, James A

    2007-01-01

    The term ethics refers to a set of principles that govern acceptable, proper conduct. Attacks on the Constitution of the United States pose the most serious breach of ethics today. Our country was founded as a republic, not as a democracy. Our Founding Fathers' main concern was to protect citizens from the power of the federal government, so constitutionally, the central government has little or no authority over individual citizens except on federal property. One of the major problems today is the fact that we now have professional politicians. This is due in large part to the lure of financial gain from countless special interest groups. This would change under constitutional law because the federal budget would decrease drastically. Article 1 states that all legislative power is vested in Congress. Congress has only 18 enumerated powers, and almost half of these pertain to defense of the country. Many of our current problems are due to regulatory agencies that have become independent fiefdoms with unconstitutional legislative, as well as executive and judicial, powers. The regulatory agency most relevant to medicine, both clinical care and research, is the FDA. It is now obvious that its basic structure needs to be changed or abolished because its actions are identical to those inherent in authoritarian systems. Constructive change could come from Congress, but it would be most desirable if the Supreme Court would take the lead and reestablish the authority of the Constitution as the Supreme Law of the Land. The FDA's function could be limited to the determination of safety, but preferably its mission would be altered to that of product certification. Defenders of the current system claim that such a drastic change would be too dangerous and their prime example is thalidomide. But it is now known that the market has already solved that problem prior to the government-imposed sanctions. Realistically, market forces and their ramifications, including our legal

  7. Constitution, 5 May 1989.

    PubMed

    1989-01-01

    This document contains provisions of Cambodia's Constitution of May 5, 1989. Article 7 gives men and women equal rights in marriage and the family, calls for monogamous marriages, and affords social protection to mothers and children. Article 8 guides parent-child relationships. The 14th article defines state property, and the 15th gives citizens full rights to own, use, and inherit land. The use of agricultural and forested land can only be changed with permission. Article 22 assigns educational responsibilities to the state, including free elementary education and a gradual expansion of higher education. Adult literacy classes are also promoted. Article 26 guarantees free medical consultations, and article 27 gives women a 90-day paid maternity leave. Breast-feeding women are also given special privileges. Article 33 guarantees the right to pay equity and to social security benefits. Article 36 grants the freedom to travel, the inviolability of homes, and privacy in correspondence of all types. PMID:12344287

  8. Constitution, 5 October 1988.

    PubMed

    1989-01-01

    This document contains major provisions of the constitution adopted by Brazil on 5 October 1988. This constitution seeks to promote the welfare of all citizens without discrimination. The equality of all citizens is guaranteed, and the equal rights of women are specifically mentioned. Property rights are also guaranteed and defined. Female inmates are granted the right to remain with their children while breast feeding. Workers are guaranteed a minimum wage, a family allowance for dependents, maternity/paternity leave, specific incentives to protect the labor market for women, retirement benefits, free day care for preschool-age children, pay equity, and equal rights between tenured and sporadically employed workers. Agrarian reform provisions are given, including the authority to expropriate land. Social and economic policies to promote health are called for, and public health services are to be decentralized, to be integrated, and to foster community participation. Pension plan and social assistance provisions are outlined as are duties of the state in regard to education. The amount of money to be dedicated to education is set out, and a national educational plan is called for to achieve such goals as the eradication of illiteracy, the universalization of school attendance, the improvement of instruction, and the provision of vocational training. Specific measures are set out to protect and preserve the environment. Family policy deals with issues of marriage, the definition of a family, divorce, the right to family planning services, and the deterrence of domestic violence. Social protection provisions cover mothers and children, handicapped persons, and protection of minors. Finally, the customs and rights of Indians are protected, with special provisions given to protect land tenure and to protect the rights of Indians in water resource development and prospecting and mining activities. PMID:12344286

  9. S-matrices and integrability

    NASA Astrophysics Data System (ADS)

    Bombardelli, Diego

    2016-08-01

    In these notes we review the S-matrix theory in (1+1)-dimensional integrable models, focusing mainly on the relativistic case. Once the main definitions and physical properties are introduced, we discuss the factorization of scattering processes due to integrability. We then focus on the analytic properties of the two-particle scattering amplitude and illustrate the derivation of the S-matrices for all the possible bound states using the so-called bootstrap principle. General algebraic structures underlying the S-matrix theory and its relation with the form factors axioms are briefly mentioned. Finally, we discuss the S-matrices of sine-Gordon and SU(2), SU(3) chiral Gross–Neveu models. In loving memory of Lilia Grandi.

  10. Householder factorizations of unitary matrices

    NASA Astrophysics Data System (ADS)

    Urías, Jesús

    2010-07-01

    A method to construct all representations of finite dimensional unitary matrices as the product of Householder reflections is given. By arbitrarily severing the state space into orthogonal subspaces, the method may, e.g., identify the entangling and single-component quantum operations that are required in the engineering of quantum states of composite (multipartite) systems. Earlier constructions are shown to be extreme cases of the unifying scheme that is presented here.

  11. Threaded Operations on Sparse Matrices

    SciTech Connect

    Sneed, Brett

    2015-09-01

    We investigate the use of sparse matrices and OpenMP multi-threading on linear algebra operations involving them. Several sparse matrix data structures are presented. Implementation of the multi- threading primarily occurs in the level one and two BLAS functions used within the four algorithms investigated{the Power Method, Conjugate Gradient, Biconjugate Gradient, and Jacobi's Method. The bene ts of launching threads once per high level algorithm are explored.

  12. Compliance matrices for cracked bodies

    NASA Technical Reports Server (NTRS)

    Ballarini, R.

    1986-01-01

    An algorithm is presented which can be used to develop compliance matrices for cracked bodies. The method relies on the numerical solution of singular integral equations with Cauchy-type kernels and provides an efficient and accurate procedure for relating applied loadings to crack opening displacements. The algorithm should be of interest to those performing repetitive calculations in the analysis of experimental results obtained from fracture specimens.

  13. Making Porous Luminescent Regions In Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W.; Jones, Eric W.

    1994-01-01

    Regions damaged by ion implantation stain-etched. Porous regions within single-crystal silicon wafers fabricated by straightforward stain-etching process. Regions exhibit visible photoluminescence at room temperature and might constitute basis of novel class of optoelectronic devices. Stain-etching process has advantages over recently investigated anodic-etching process. Process works on both n-doped and p-doped silicon wafers. Related development reported in article, "Porous Si(x)Ge(1-x) Layers Within Single Crystals of Si," (NPO-18836).

  14. Constitutive models in LAME.

    SciTech Connect

    Hammerand, Daniel Carl; Scherzinger, William Mark

    2007-09-01

    The Library of Advanced Materials for Engineering (LAME) provides a common repository for constitutive models that can be used in computational solid mechanics codes. A number of models including both hypoelastic (rate) and hyperelastic (total strain) constitutive forms have been implemented in LAME. The structure and testing of LAME is described in Scherzinger and Hammerand ([3] and [4]). The purpose of the present report is to describe the material models which have already been implemented into LAME. The descriptions are designed to give useful information to both analysts and code developers. Thus far, 33 non-ITAR/non-CRADA protected material models have been incorporated. These include everything from the simple isotropic linear elastic models to a number of elastic-plastic models for metals to models for honeycomb, foams, potting epoxies and rubber. A complete description of each model is outside the scope of the current report. Rather, the aim here is to delineate the properties, state variables, functions, and methods for each model. However, a brief description of some of the constitutive details is provided for a number of the material models. Where appropriate, the SAND reports available for each model have been cited. Many models have state variable aliases for some or all of their state variables. These alias names can be used for outputting desired quantities. The state variable aliases available for results output have been listed in this report. However, not all models use these aliases. For those models, no state variable names are listed. Nevertheless, the number of state variables employed by each model is always given. Currently, there are four possible functions for a material model. This report lists which of these four methods are employed in each material model. As far as analysts are concerned, this information is included only for the awareness purposes. The analyst can take confidence in the fact that model has been properly implemented

  15. The Constitution and American Diversity.

    ERIC Educational Resources Information Center

    Glazer, Nathan

    1987-01-01

    Diversity in American constitutional law refers to differences among the laws of the states. However, key phrases in the Constitution have been used to ensure individual rights. The expansion of those rights has led to conflict between community needs and those of the individual, with each side referring to the Constitution for support. (PS)

  16. How Democratic Is the Constitution?

    ERIC Educational Resources Information Center

    Goldwin, Robert A., Ed.; Schambra, William A., Ed.

    Designed to help prepare the nation for a thoughtful observance of the Constitutional bicentennial, this publication contains seven essays on the topic of democracy and the Constitution. "Democracy and the Constitution" (Gordon S. Wood) looks at the popular and democratic rhetoric used to justify the federalist system in the late 1700's. "Decent,…

  17. Rotationally invariant ensembles of integrable matrices

    NASA Astrophysics Data System (ADS)

    Yuzbashyan, Emil A.; Shastry, B. Sriram; Scaramazza, Jasen A.

    2016-05-01

    We construct ensembles of random integrable matrices with any prescribed number of nontrivial integrals and formulate integrable matrix theory (IMT)—a counterpart of random matrix theory (RMT) for quantum integrable models. A type-M family of integrable matrices consists of exactly N -M independent commuting N ×N matrices linear in a real parameter. We first develop a rotationally invariant parametrization of such matrices, previously only constructed in a preferred basis. For example, an arbitrary choice of a vector and two commuting Hermitian matrices defines a type-1 family and vice versa. Higher types similarly involve a random vector and two matrices. The basis-independent formulation allows us to derive the joint probability density for integrable matrices, similar to the construction of Gaussian ensembles in the RMT.

  18. Socialist Constitution [1992].

    PubMed

    1992-12-15

    This document contains the text of the Constitution of the Democratic People's Republic of Korea. Chapter 1 sets out the political principles which govern the existence of the state. Chapter 2 outlines the principles of the socialist economy as they apply to the collective and private ownership of property, to meeting the needs of working people, to the technological revolution, to labor regulations (including a minimum working age of 16 years), to development plans, and to external trade. Chapter 3 covers aspects of culture including education, which involves 11-years of compulsory schooling, scholarships to universities and professional schools, and social education. Children of preschool age are enrolled in nurseries and kindergartens at the state's expense. Other issues dealt with in this chapter are the advancement of science and technology, the work of writers and artists, the provision of cultural facilities, protection of the language, the availability of physical fitness facilities, a universal free medical system, and environmental protection. Chapter 4 outlines national defense measures, and chapter 5 sets out the fundamental rights and duties of citizens. This chapter accords women equal social status and rights as men and protects marriage and the family. State institutions (such as the Supreme People's Assembly, the presidency, the National Defense Committee, the Central People's Committee, the Administrative Council, local assemblies and committees, and the court and procurator's office) are discussed in chapter 6. Chapter 7 describes the national emblem and flag and designates Pyongyang as the capital. PMID:12347140

  19. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2002-01-01

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  20. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2003-12-23

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  1. Constitutive equations for an electroactive polymer

    NASA Astrophysics Data System (ADS)

    Tixier, Mireille; Pouget, Joël

    2016-07-01

    Ionic electroactive polymers can be used as sensors or actuators. For this purpose, a thin film of polyelectrolyte is saturated with a solvent and sandwiched between two platinum electrodes. The solvent causes a complete dissociation of the polymer and the release of small cations. The application of an electric field across the thickness results in the bending of the strip and vice versa. The material is modeled by a two-phase continuous medium. The solid phase, constituted by the polymer backbone inlaid with anions, is depicted as a deformable porous media. The liquid phase is composed of the free cations and the solvent (usually water). We used a coarse grain model. The conservation laws of this system have been established in a previous work. The entropy balance law and the thermodynamic relations are first written for each phase and then for the complete material using a statistical average technique and the material derivative concept. One deduces the entropy production. Identifying generalized forces and fluxes provides the constitutive equations of the whole system: the stress-strain relations which satisfy a Kelvin-Voigt model, generalized Fourier's and Darcy's laws and the Nernst-Planck equation.

  2. Constitutive equations for an electroactive polymer

    NASA Astrophysics Data System (ADS)

    Tixier, Mireille; Pouget, Joël

    2015-07-01

    Ionic electroactive polymers can be used as sensors or actuators. For this purpose, a thin film of polyelectrolyte is saturated with a solvent and sandwiched between two platinum electrodes. The solvent causes a complete dissociation of the polymer and the release of small cations. The application of an electric field across the thickness results in the bending of the strip and vice versa. The material is modeled by a two-phase continuous medium. The solid phase, constituted by the polymer backbone inlaid with anions, is depicted as a deformable porous media. The liquid phase is composed of the free cations and the solvent (usually water). We used a coarse grain model. The conservation laws of this system have been established in a previous work. The entropy balance law and the thermodynamic relations are first written for each phase and then for the complete material using a statistical average technique and the material derivative concept. One deduces the entropy production. Identifying generalized forces and fluxes provides the constitutive equations of the whole system: the stress-strain relations which satisfy a Kelvin-Voigt model, generalized Fourier's and Darcy's laws and the Nernst-Planck equation.

  3. Superalgebraic representation of Dirac matrices

    NASA Astrophysics Data System (ADS)

    Monakhov, V. V.

    2016-01-01

    We consider a Clifford extension of the Grassmann algebra in which operators are constructed from products of Grassmann variables and derivatives with respect to them. We show that this algebra contains a subalgebra isomorphic to a matrix algebra and that it additionally contains operators of a generalized matrix algebra that mix states with different numbers of Grassmann variables. We show that these operators are extensions of spin-tensors to the case of superspace. We construct a representation of Dirac matrices in the form of operators of a generalized matrix algebra.

  4. Porous Shape Memory Polymers

    PubMed Central

    Hearon, Keith; Singhal, Pooja; Horn, John; Small, Ward; Olsovsky, Cory; Maitland, Kristen C.; Wilson, Thomas S.; Maitland, Duncan J.

    2013-01-01

    Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use. PMID:23646038

  5. Tailored Porous Materials

    SciTech Connect

    BARTON,THOMAS J.; BULL,LUCY M.; KLEMPERER,WALTER G.; LOY,DOUGLAS A.; MCENANEY,BRIAN; MISONO,MAKOTO; MONSON,PETER A.; PEZ,GUIDO; SCHERER,GEORGE W.; VARTULI,JAMES C.; YAGHI,OMAR M.

    1999-11-09

    Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form of fibers, thin films and monoliths. These issues are addressed in the context of five specific classes of porous materials: oxide molecular sieves, porous coordination solids, porous carbons, sol-gel derived oxides, and porous heteropolyanion salts. Reviews of these specific areas are preceded by a presentation of background material and review of current theoretical approaches to adsorption phenomena. A concluding section outlines current research needs and opportunities.

  6. Constitutional Issues--Watergate and the Constitution. Teaching with Documents.

    ERIC Educational Resources Information Center

    National Archives and Records Administration, Washington, DC.

    When U.S. President Richard Nixon resigned in 1974 in the wake of the Watergate scandal, it was only the second time that impeachment of a president had been considered. Although the U.S. Constitution has provisions for a person removed from office to be indicted, there are no guidelines in the Constitution about a President who has resigned. The…

  7. Constitutive Theory for Velocity Dispersion in Rock with Dual Porosity

    SciTech Connect

    Wang, H F; Berryman, J G

    2002-03-28

    The high frequency behavior of the bulk modulus of fluid-saturated rock can be obtained from a double-porosity constitutive model, which is a direct conceptual extension of Biot's (1941) constitutive equations and which provides additional stiffening due to unrelaxed induced pore pressures in the soft porosity phase. Modeling the stiffening of the shear modulus at high frequency requires an effective medium average over the unequal induced pore pressures in cracks of different orientations. The implicit assumptions are that pore fluid equilibration does not occur between cracks of different orientations and between cracks and porous matrix. The correspondence between the constitutive equations of Berryman and Wang (1995) and Mavko and Jizba (1991) is explicitly noted.

  8. Characterization of a new heat dissipation matric potential sensor.

    PubMed

    Matile, Luzius; Berger, Roman; Wächter, Daniel; Krebs, Rolf

    2013-01-01

    Soil moisture sensors can help to reduce the amount of water needed for irrigation. In this paper we describe the PlantCare soil moisture sensor as a new type of heat dissipation sensor, its calibration and the correction for temperature changes. With the PlantCare sensor it is possible to measure the matric potential indirectly to monitor or control irrigation. This sensor is based on thermal properties of a synthetic felt. After a defined heating phase the cooling time to a threshold temperature is a function of the water content in the synthetic felt. The water content in this porous matrix is controlled by the matric potential in the surrounding soil. Calibration measurements have shown that the sensor is most sensitive to -400 hPa and allows lower sensitivity measurements to -800 hPa. The disturbing effect of the temperature change during the measurement on the cooling time can be corrected by a linear function and the differences among sensors are minimized by a two point calibration. PMID:23344384

  9. The Constitution and Citizenship Education.

    ERIC Educational Resources Information Center

    Shoemaker, Rebecca S.

    The paper takes the position that the study and understanding of the United States Constitution should be a critical part of citizenship education, especially as its Bicentennial approaches. Several factors suggest that the Constitution has become the most durable document of its kind in history, and that its teaching should be centered in both…

  10. The Constitution and American Radicalism.

    ERIC Educational Resources Information Center

    Lobel, Jules

    1987-01-01

    Discusses the history of the following movements' attitudes towards the Constitution: (1) abolition; (2) feminism; (3) trade unions; (4) socialism and communism; and (5) civil rights and anti-war. Maintains that the tensions in these movements' towards the Constitution represent basic contradictions in the document itself. (PS)

  11. How Capitalistic Is the Constitution?

    ERIC Educational Resources Information Center

    Goldwin, Robert A., Ed.; Schambra, William A., Ed.

    Second in a three-part series designed to help prepare the nation for a thoughtful observance of the Constitutional bicentennial, this publication contains seven essays on the topic of capitalism and the Constitution. "American Democracy and the Acquisitive Spirit" (Marc F. Plattner) supports the argument that the framers of the Constitution…

  12. The Constitution and Its Critics

    ERIC Educational Resources Information Center

    Main, Thomas J.

    2011-01-01

    In planning a freshman undergraduate curriculum with colleagues recently, the question arose as to what type of understanding educators wanted to impart to their students about the Constitution. The alleged defects of the Constitution that these books point to are wide-ranging and can be classified into various categories. Some problems--such as…

  13. Reordering American Constitutional Law Teaching.

    ERIC Educational Resources Information Center

    Gerber, Scott D.

    1994-01-01

    Maintains that constitutional law is the cornerstone of an undergraduate public law curriculum. Asserts that there is a welcome trend toward teaching the subject over a two-semester sequence, instead of only one. Describes course content and teaching strategies used in a college constitutional law course. (CFR)

  14. Constitutional Law and Liberal Education.

    ERIC Educational Resources Information Center

    Clor, Harry

    1985-01-01

    By studying constitutional law, students learn about the relationship between democratic theory and practice, one of the main concerns of liberal education. The mind is enlarged when it must apply ethical standards and political ideas to real human problems. How a political science professor teaches constitutional law is discussed. (RM)

  15. Engineered matrices for bone regeneration

    NASA Astrophysics Data System (ADS)

    Winn, Shelley R.; Hu, Yunhua; Pugh, Amy; Brown, Leanna; Nguyen, Jesse T.; Hollinger, Jeffrey O.

    2000-06-01

    Traditional therapies of autografts and allogeneic banked bone can promote reasonable clinical outcome to repair damaged bone. However, under certain conditions the success of these traditional approaches plummets, providing the incentive for researchers to develop clinical alternatives. The evolving field of tissue engineering in the musculoskeletal system attempts to mimic many of the components from the intact, healthy subject. Those components consist of a biologic scaffold, cells, extracellular matrix, and signaling molecules. The bone biomimetic, i.e., an engineered matrix, provides a porous structural architecture for the regeneration and ingrowth of osseous tissue at the site of injury. To further enhance the regenerative cascade, our strategy has involved porous biodegradable scaffolds containing and releasing signaling molecules and providing a suitable environment for cell attachment, growth and differentiation. In addition, the inclusion of genetically modified osteogenic precursor cells has brought the technology closer to developing a tissue-engineered equivalent. The presentation will describe various formulations and the methods utilized to evaluate the clinical utility of these biomimetics.

  16. Quasiperiodic tilings generated by matrices

    NASA Astrophysics Data System (ADS)

    Rao, Nagaraja S.; Suryanarayan, E. R.

    1994-02-01

    Using the inflation method, Watanabe, Ito and Soma [3], Clark and Suryanarayan [4] and Balagurusamy, Ramesh and Gopal [5] have obtained nonperiodic tilings of the plane with n-fold rotational symmetry, n = 2, 3, 4, 5, 8, using two unit prototiles. Fortunately, there is an easier way to generate a more general class of nonperiodic tilings which contains the above-mentioned tilings as special cases. We do this by specifying two matrices of order two which define the two classes of tilings; thus, our approach uses the basic techniques from linear algebra in the study of quasiperiodic tilings and the method can be generalized to obtain tilings that have more than two prototiles. The tilings generated are fractals and their dimensions and the rate of growth are determined.

  17. Shrinkage estimators for covariance matrices.

    PubMed

    Daniels, M J; Kass, R E

    2001-12-01

    Estimation of covariance matrices in small samples has been studied by many authors. Standard estimators, like the unstructured maximum likelihood estimator (ML) or restricted maximum likelihood (REML) estimator, can be very unstable with the smallest estimated eigenvalues being too small and the largest too big. A standard approach to more stably estimating the matrix in small samples is to compute the ML or REML estimator under some simple structure that involves estimation of fewer parameters, such as compound symmetry or independence. However, these estimators will not be consistent unless the hypothesized structure is correct. If interest focuses on estimation of regression coefficients with correlated (or longitudinal) data, a sandwich estimator of the covariance matrix may be used to provide standard errors for the estimated coefficients that are robust in the sense that they remain consistent under misspecification of the covariance structure. With large matrices, however, the inefficiency of the sandwich estimator becomes worrisome. We consider here two general shrinkage approaches to estimating the covariance matrix and regression coefficients. The first involves shrinking the eigenvalues of the unstructured ML or REML estimator. The second involves shrinking an unstructured estimator toward a structured estimator. For both cases, the data determine the amount of shrinkage. These estimators are consistent and give consistent and asymptotically efficient estimates for regression coefficients. Simulations show the improved operating characteristics of the shrinkage estimators of the covariance matrix and the regression coefficients in finite samples. The final estimator chosen includes a combination of both shrinkage approaches, i.e., shrinking the eigenvalues and then shrinking toward structure. We illustrate our approach on a sleep EEG study that requires estimation of a 24 x 24 covariance matrix and for which inferences on mean parameters critically

  18. Proper Values of Matrices and Some Applications.

    ERIC Educational Resources Information Center

    Amir-Moez, Ali R.

    1992-01-01

    Presents a short study of proper values of two-by-two matrices with real entries. Gives examples of symmetric matrices and applications to systems of linear equations of perpendicular lines intersecting at the origin and central conics rotated about the origin to eliminate the xy term from its equation. (MDH)

  19. Biocompatibility of Experimental Polymeric Tracheal Matrices.

    PubMed

    Kiselevskii, M V; Chikileva, I O; Vlasenko, R Ya; Sitdikova, S M; Tenchurin, T Kh; Mamagulashvili, V G; Shepelev, A D; Grigoriev, T A; Chvalun, S N

    2016-08-01

    Biocompatibility of a new tracheal matrix is studied. The new matrix is based on polymeric ultra-fiber material colonized by mesenchymal multipotent stromal cells. The experiments demonstrate cytoconductivity of the synthetic matrices and no signs of their degradation within 2 months after their implantation to recipient mice. These data suggest further studies of the synthetic tracheal matrices on large laboratory animals. PMID:27591876

  20. Harmonic balance calculations by using matrices

    NASA Astrophysics Data System (ADS)

    Fergusson, N. J.; Leung, A. Y. T.

    1995-05-01

    The computation of the total and tangential stiffness matrices associated with the harmonic balance method for non-linear ordinary differential equations requires some complicated calculations involving double sums. Some matrix results are presented here that ease the associated book-keeping and allow the matrices to be programmed easily.

  1. Products of Independent Elliptic Random Matrices

    NASA Astrophysics Data System (ADS)

    O'Rourke, Sean; Renfrew, David; Soshnikov, Alexander; Vu, Van

    2015-07-01

    For fixed , we study the product of independent elliptic random matrices as tends to infinity. Our main result shows that the empirical spectral distribution of the product converges, with probability , to the -th power of the circular law, regardless of the joint distribution of the mirror entries in each matrix. This leads to a new kind of universality phenomenon: the limit law for the product of independent random matrices is independent of the limit laws for the individual matrices themselves. Our result also generalizes earlier results of Götze-Tikhomirov (On the asymptotic spectrum of products of independent random matrices, available at http://arxiv.org/abs/1012.2710) and O'Rourke-Soshnikov (J Probab 16(81):2219-2245, 2011) concerning the product of independent iid random matrices.

  2. Dispersion and attenuation of acoustic guided waves in layered fluid-filled porous media

    SciTech Connect

    Parra, J.O.; Xu, P. )

    1994-01-01

    The analysis of acoustic wave propagation in fluid-filled porous media based on Biot and homogenization theories has been adapted to calculate dispersion and attenuation of guided waves trapped in low-velocity layered media. Constitutive relations, the balance equation, and the generalized Darcy law of the modified Biot theory yield a coupled system of differential equations which governs the wave motion in each layer. The displacement and stress fields satisfy the boundary conditions of continuity of displacements and tractions across each interface, and the radiation condition at infinity. To avoid precision problems caused by the growing exponential in individual matrices for large wave numbers, the global matrix method was implemented as an alternative to the traditional propagation approach to determine the periodic equations. The complex wave numbers of the guided wave modes were determined using a combination of two-dimensional bracketing and minimization techniques. The results of this work indicate that the acoustic guided wave attenuation is sensitive to the [ital in] [ital situ] permeability. In particular, the attenuation changes significantly as the [ital in] [ital situ] permeability of the low-velocity layer is varied at the frequency corresponding to the minimum group velocity (Airy phase). Alternatively, the attenuation of the wave modes are practically unaffected by those permeability variations in the layer at the frequency corresponding to the maximum group velocity.

  3. Remarks on turbulent constitutive relations

    NASA Technical Reports Server (NTRS)

    Shih, Tsan-Hsing; Lumley, John L.

    1993-01-01

    The paper demonstrates that the concept of turbulent constitutive relations can be used to construct general models for various turbulent correlations. Some of the Generalized Cayley-Hamilton formulas for relating tensor products of higher extension to tensor products of lower extension are introduced. The combination of dimensional analysis and invariant theory can lead to 'turbulent constitutive relations' (or general turbulence models) for, in principle, any turbulent correlations. As examples, the constitutive relations for Reynolds stresses and scalar fluxes are derived. The results are consistent with ones from Renormalization Group (RNG) theory and two-scale Direct-Interaction Approximation (DIA) method, but with a more general form.

  4. Abnormal human sex chromosome constitutions

    SciTech Connect

    1993-12-31

    Chapter 22, discusses abnormal human sex chromosome constitution. Aneuploidy of X chromosomes with a female phenotype, sex chromosome aneuploidy with a male phenotype, and various abnormalities in X chromosome behavior are described. 31 refs., 2 figs.

  5. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Lindholm, U. S.

    1984-01-01

    A state-of-the-art review of applicable constitutive models with selection of two for detailed comparison with a wide range of experimental tests was conducted. The experimental matrix contained uniaxial and biaxial tensile, creep, stress relaxation, and cyclic fatigue tests at temperatures to 1093 C and strain rates from .0000001 to .001/sec. Some nonisothermal cycles will also be run. The constitutive models will be incorporated into the MARC finite element structural analysis program with a demonstration computation made for advanced turbine blade configuration. In the code development work, particular emphasis is being placed on developing efficient integration algorithms for the highly nonlinear and stiff constitutive equations. Another area of emphasis is the appropriate and efficient methodology for determing constitutive constants from a minimum extent of experimental data.

  6. The Constitution's Prescription for Freedom.

    ERIC Educational Resources Information Center

    Peach, Lucinda

    1986-01-01

    Examines how the framers of the Constitution came to choose our system of government, how that system was designed to function, and how the separation of powers has served to maintain our democracy despite attempts to violate it. (JDH)

  7. Are Sanctions on Employers Constitutional?

    ERIC Educational Resources Information Center

    Gollobin, Ira

    1988-01-01

    Questions the constitutional validity of employer sanctions used to deter illegal immigration under the Immigration Reform and Control Act. Points out the anomaly of using criminal penalties to deter a civil, administrative violation. (FMW)

  8. Rotationally invariant ensembles of integrable matrices

    NASA Astrophysics Data System (ADS)

    Scaramazza, Jasen; Yuzbashyan, Emil; Shastry, Sriram

    We construct ensembles of random integrable matrices with any prescribed number of nontrivial integrals and formulate integrable matrix theory (IMT) - a counterpart of random matrix theory (RMT) for quantum integrable models. A type- M family of integrable matrices consists of exactly N - M independent commuting N × N matrices linear in a real parameter. We first develop a rotationally invariant parameterization of such matrices, previously only constructed in a preferred basis. For example, an arbitrary choice of a vector and two commuting Hermitian matrices defines a type-1 family and vice-versa. Higher types similarly involve a random vector and two matrices. The basis-independent formulation allows us to derive the joint probability density for integrable matrices, in a manner similar to the construction of Gaussian ensembles in the RMT. This work was supported in part by the David and Lucille Packard Foundation. The work at UCSC was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award # FG02-06ER46319.

  9. Community Detection for Correlation Matrices

    NASA Astrophysics Data System (ADS)

    MacMahon, Mel; Garlaschelli, Diego

    2015-04-01

    A challenging problem in the study of complex systems is that of resolving, without prior information, the emergent, mesoscopic organization determined by groups of units whose dynamical activity is more strongly correlated internally than with the rest of the system. The existing techniques to filter correlations are not explicitly oriented towards identifying such modules and can suffer from an unavoidable information loss. A promising alternative is that of employing community detection techniques developed in network theory. Unfortunately, this approach has focused predominantly on replacing network data with correlation matrices, a procedure that we show to be intrinsically biased because of its inconsistency with the null hypotheses underlying the existing algorithms. Here, we introduce, via a consistent redefinition of null models based on random matrix theory, the appropriate correlation-based counterparts of the most popular community detection techniques. Our methods can filter out both unit-specific noise and system-wide dependencies, and the resulting communities are internally correlated and mutually anticorrelated. We also implement multiresolution and multifrequency approaches revealing hierarchically nested subcommunities with "hard" cores and "soft" peripheries. We apply our techniques to several financial time series and identify mesoscopic groups of stocks which are irreducible to a standard, sectorial taxonomy; detect "soft stocks" that alternate between communities; and discuss implications for portfolio optimization and risk management.

  10. Ventilation of porous media

    DOEpatents

    Neeper, Donald A.

    1994-01-01

    Methods for distributing gases throughout the interstices of porous materials and removing volatile substances from the interstices of porous materials. Continuous oscillation of pressures and flows results in increased penetration of the interstices by flowing gases and increased transport of gaseous components out of the interstices. The invention is particularly useful in soil vapor extraction.

  11. Ventilation of porous media

    DOEpatents

    Neeper, D.A.

    1994-02-22

    Methods are presented for distributing gases throughout the interstices of porous materials and removing volatile substances from the interstices of porous materials. Continuous oscillation of pressures and flows results in increased penetration of the interstices by flowing gases and increased transport of gaseous components out of the interstices. The invention is particularly useful in soil vapor extraction. 10 figures.

  12. LU decompositions of generalized diagonally dominant matrices

    SciTech Connect

    Funderlic, R.E.; Neumann, M.; Plemmons, R.J.

    1982-02-01

    Using the simple vehicle of M-matrices, the existence and stability of LU decompositions of matrices A which can be scaled to diagonally dominant (possibly singular) matrices are investigated. Bounds on the growth factor for Gaussian elimination on A are derived. Motivation for this study is provided in part by applications to solving homogeneous systems of linear equations Ax = 0, arising in Markov queuing networks, input-output models in economics and compartmental systems, where A or -A is an irreducible, singular M-matrix.

  13. Kerov's interlacing sequences and random matrices

    NASA Astrophysics Data System (ADS)

    Bufetov, Alexey

    2013-11-01

    To a N × N real symmetric matrix Kerov assigns a piecewise linear function whose local minima are the eigenvalues of this matrix and whose local maxima are the eigenvalues of its (N - 1) × (N - 1) submatrix. We study the scaling limit of Kerov's piecewise linear functions for Wigner and Wishart matrices. For Wigner matrices the scaling limit is given by the Verhik-Kerov-Logan-Shepp curve which is known from asymptotic representation theory. For Wishart matrices the scaling limit is also explicitly found, and we explain its relation to the Marchenko-Pastur limit spectral law.

  14. Kerov's interlacing sequences and random matrices

    SciTech Connect

    Bufetov, Alexey

    2013-11-15

    To a N × N real symmetric matrix Kerov assigns a piecewise linear function whose local minima are the eigenvalues of this matrix and whose local maxima are the eigenvalues of its (N − 1) × (N − 1) submatrix. We study the scaling limit of Kerov's piecewise linear functions for Wigner and Wishart matrices. For Wigner matrices the scaling limit is given by the Verhik-Kerov-Logan-Shepp curve which is known from asymptotic representation theory. For Wishart matrices the scaling limit is also explicitly found, and we explain its relation to the Marchenko-Pastur limit spectral law.

  15. Porous silicon gettering

    SciTech Connect

    Tsuo, Y.S.; Menna, P.; Al-Jassim, M.

    1995-08-01

    We have studied a novel extrinsic gettering method that utilizes the very large surface areas, produced by porous silicon etch on both front and back surfaces of the silicon wafer, as gettering sites. In this method, a simple and low-cost chemical etching is used to generate the porous silicon layers. Then, a high-flux solar furnace (HFSF) is used to provide high-temperature annealing and the required injection of silicon interstitials. The gettering sites, along with the gettered impurities, can be easily removed at the end the process. The porous silicon removal process consists of oxidizing the porous silicon near the end the gettering process followed by sample immersion in HF acid. Each porous silicon gettering process removes up to about 10 {mu}m of wafer thickness. This gettering process can be repeated so that the desired purity level is obtained.

  16. Speciation of nanoscale objects by nanoparticle imprinted matrices

    NASA Astrophysics Data System (ADS)

    Hitrik, Maria; Pisman, Yamit; Wittstock, Gunther; Mandler, Daniel

    2016-07-01

    The toxicity of nanoparticles is not only a function of the constituting material but depends largely on their size, shape and stabilizing shell. Hence, the speciation of nanoscale objects, namely, their detection and separation based on the different species, similarly to heavy metals, is of outmost importance. Here we demonstrate the speciation of gold nanoparticles (AuNPs) and their electrochemical detection using the concept of ``nanoparticles imprinted matrices'' (NAIM). Negatively charged AuNPs are adsorbed as templates on a conducting surface previously modified with polyethylenimine (PEI). The selective matrix is formed by the adsorption of either oleic acid (OA) or poly(acrylic acid) (PAA) on the non-occupied areas. The AuNPs are removed by electrooxidation to form complementary voids. These voids are able to recognize the AuNPs selectively based on their size. Furthermore, the selectivity could be improved by adsorbing an additional layer of 1-hexadecylamine, which deepened the voids. Interestingly, silver nanoparticles (AgNPs) were also recognized if their size matched those of the template AuNPs. The steps in assembling the NAIMs and the reuptake of the nanoparticles were characterized carefully. The prospects for the analytical use of NAIMs, which are simple, of small dimension, cost-efficient and portable, are in the sensing and separation of nanoobjects.The toxicity of nanoparticles is not only a function of the constituting material but depends largely on their size, shape and stabilizing shell. Hence, the speciation of nanoscale objects, namely, their detection and separation based on the different species, similarly to heavy metals, is of outmost importance. Here we demonstrate the speciation of gold nanoparticles (AuNPs) and their electrochemical detection using the concept of ``nanoparticles imprinted matrices'' (NAIM). Negatively charged AuNPs are adsorbed as templates on a conducting surface previously modified with polyethylenimine (PEI). The

  17. ESTIMATION OF FUNCTIONALS OF SPARSE COVARIANCE MATRICES

    PubMed Central

    Fan, Jianqing; Rigollet, Philippe; Wang, Weichen

    2016-01-01

    High-dimensional statistical tests often ignore correlations to gain simplicity and stability leading to null distributions that depend on functionals of correlation matrices such as their Frobenius norm and other ℓr norms. Motivated by the computation of critical values of such tests, we investigate the difficulty of estimation the functionals of sparse correlation matrices. Specifically, we show that simple plug-in procedures based on thresholded estimators of correlation matrices are sparsity-adaptive and minimax optimal over a large class of correlation matrices. Akin to previous results on functional estimation, the minimax rates exhibit an elbow phenomenon. Our results are further illustrated in simulated data as well as an empirical study of data arising in financial econometrics. PMID:26806986

  18. A Computer Program for Clustering Large Matrices

    ERIC Educational Resources Information Center

    Koch, Valerie L.

    1976-01-01

    A Fortran V program is described derived for the Univac 1100 Series Computer for clustering into hierarchical structures large matrices, up to 1000 x 1000 and larger, of interassociations between objects. (RC)

  19. Synchronous correlation matrices and Connes' embedding conjecture

    NASA Astrophysics Data System (ADS)

    Dykema, Kenneth J.; Paulsen, Vern

    2016-01-01

    In the work of Paulsen et al. [J. Funct. Anal. (in press); preprint arXiv:1407.6918], the concept of synchronous quantum correlation matrices was introduced and these were shown to correspond to traces on certain C*-algebras. In particular, synchronous correlation matrices arose in their study of various versions of quantum chromatic numbers of graphs and other quantum versions of graph theoretic parameters. In this paper, we develop these ideas further, focusing on the relations between synchronous correlation matrices and microstates. We prove that Connes' embedding conjecture is equivalent to the equality of two families of synchronous quantum correlation matrices. We prove that if Connes' embedding conjecture has a positive answer, then the tracial rank and projective rank are equal for every graph. We then apply these results to more general non-local games.

  20. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Lindholm, Ulric S.

    1985-01-01

    The objective is to develop a unified constitutive model for finite element structural analysis of turbine engine hot-section components. This effort constitutes a different approach for non-linear finite-element computer codes which have heretofore been based on classical inelastic methods. The unified constitutive theory to be developed will avoid the simplifying assumptions of classical theory and should more accurately represent the behavior of superalloy materials under cyclic loading conditions and high temperature environments. During the first two years of the program, extensive experimental correlations were made with two representative unified models. The experiments were both uniaxial and biaxial at temperatures up to 1093 C (2000 F). In addition, the unified models were adopted to the MARC finite element code and used for stress analysis of notched bar and turbine blade geometries.

  1. Fermion masses from SO(10) Hermitian matrices

    SciTech Connect

    Moorhouse, R. G.

    2008-03-01

    Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126 scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.

  2. Fermion masses from SO(10) Hermitian matrices

    NASA Astrophysics Data System (ADS)

    Moorhouse, R. G.

    2008-03-01

    Masses of fermions in the SO(10) 16-plet are constructed using only the 10, 120, and 126¯ scalar multiplets. The mass matrices are restricted to be Hermitian and the theory is constructed to have certain assumed quark masses, charged lepton masses, and Cabibbo-Kobayashi-Maskawa (CKM) matrix in accord with data. The remaining free parameters are found by fitting to light neutrino masses and Maki-Nakagawa-Sakata (MNS) matrices result as predictions.

  3. Preparation of asymmetric porous materials

    DOEpatents

    Coker, Eric N.

    2012-08-07

    A method for preparing an asymmetric porous material by depositing a porous material film on a flexible substrate, and applying an anisotropic stress to the porous media on the flexible substrate, where the anisotropic stress results from a stress such as an applied mechanical force, a thermal gradient, and an applied voltage, to form an asymmetric porous material.

  4. Fabricating porous silicon carbide

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1994-01-01

    The formation of porous SiC occurs under electrochemical anodization. A sample of SiC is contacted electrically with nickel and placed into an electrochemical cell which cell includes a counter electrode and a reference electrode. The sample is encapsulated so that only a bare semiconductor surface is exposed. The electrochemical cell is filled with an HF electrolyte which dissolves the SiC electrochemically. A potential is applied to the semiconductor and UV light illuminates the surface of the semiconductor. By controlling the light intensity, the potential and the doping level, a porous layer is formed in the semiconductor and thus one produces porous SiC.

  5. Take Advantage of Constitution Day

    ERIC Educational Resources Information Center

    McCune, Bonnie F.

    2008-01-01

    The announcement of the mandate for Constitution and Citizenship Day shortly before September, 2005, probably led to groans of dismay. Not another "must-do" for teachers and schools already stressed by federal and state requirements for standardized tests, increasingly rigid curricula, and scrutiny from the public and officials. But the idea and…

  6. Lazy Elephants and the Constitution.

    ERIC Educational Resources Information Center

    Hantula, James

    1989-01-01

    Depicts an eighth grade unit utilizing the production of a newspaper to teach U.S. history, 1787 to 1791, in a combined social studies and language arts class at Malcolm Price Laboratory School (Iowa). Two teachers used both large- and small-group instruction to focus on the development of the U.S. Constitution. (LS)

  7. Constitutional Reform of School Finance.

    ERIC Educational Resources Information Center

    Alexander, Kern, Ed.; Jordan, K. Forbis, Ed.

    This book contains conference papers by experts in educational administration, law, and economics. Six of the papers are devoted to a legal analysis of fiscal inequality among school attendance units, school districts, and States. These contributions are: (1) K. Forbis Jordan and Kern Alexander, "Constitutional Methods of Financing Public…

  8. A Venture in Constitutional Law.

    ERIC Educational Resources Information Center

    Cole, W. Graham; Dillon, Dorothy H.

    1980-01-01

    Senior high girls and boys from two single-sex schools undertook a study of a Supreme Court case that provided insight not only into constitutional law and history but also into how men and women can work together and relate in other ways than dating. (DS)

  9. A Brief Historical Introduction to Matrices and Their Applications

    ERIC Educational Resources Information Center

    Debnath, L.

    2014-01-01

    This paper deals with the ancient origin of matrices, and the system of linear equations. Included are algebraic properties of matrices, determinants, linear transformations, and Cramer's Rule for solving the system of algebraic equations. Special attention is given to some special matrices, including matrices in graph theory and electrical…

  10. Developmental Differences in Strategies for Solving Figural Matrices.

    ERIC Educational Resources Information Center

    Foorman, Barbara R.; And Others

    In order to study children's strategies for solving geometric matrices similar to those in the Raven's Progressive Matrices, ninety 7-, 10-, and 13-year-old boys and girls were administered tests of auditory and visual memory, the Raven's, and geometric matrices. The matrices varied in number of elements (1 to 3) and number of transformations (0…

  11. Porous Organic Molecular Materials

    SciTech Connect

    Tian, Jian; Thallapally, Praveen K.; McGrail, B. Peter

    2012-01-01

    Most nanoporous materials with molecular-scale pores are extended frameworks composed of directional covalent or coordination bonding, such as porous metal-organic frameworks and organic network polymers. By contrast, nanoporous materials comprised of discrete organic molecules, between which there are only weak non-covalent interactions, are seldom encountered. Indeed, most organic molecules pack efficiently in the solid state to minimize the void volume, leading to non-porous materials. In recent years, a significant number of nanoporous organic molecular materials, which may be either crystalline or amorphous, have been confirmed by the studies of gas adsorption and they are surveyed in this Highlight. In addition, the possible advantages of porous organic molecular materials over porous networks are discussed.

  12. Condition number estimation of preconditioned matrices.

    PubMed

    Kushida, Noriyuki

    2015-01-01

    The present paper introduces a condition number estimation method for preconditioned matrices. The newly developed method provides reasonable results, while the conventional method which is based on the Lanczos connection gives meaningless results. The Lanczos connection based method provides the condition numbers of coefficient matrices of systems of linear equations with information obtained through the preconditioned conjugate gradient method. Estimating the condition number of preconditioned matrices is sometimes important when describing the effectiveness of new preconditionerers or selecting adequate preconditioners. Operating a preconditioner on a coefficient matrix is the simplest method of estimation. However, this is not possible for large-scale computing, especially if computation is performed on distributed memory parallel computers. This is because, the preconditioned matrices become dense, even if the original matrices are sparse. Although the Lanczos connection method can be used to calculate the condition number of preconditioned matrices, it is not considered to be applicable to large-scale problems because of its weakness with respect to numerical errors. Therefore, we have developed a robust and parallelizable method based on Hager's method. The feasibility studies are curried out for the diagonal scaling preconditioner and the SSOR preconditioner with a diagonal matrix, a tri-daigonal matrix and Pei's matrix. As a result, the Lanczos connection method contains around 10% error in the results even with a simple problem. On the other hand, the new method contains negligible errors. In addition, the newly developed method returns reasonable solutions when the Lanczos connection method fails with Pei's matrix, and matrices generated with the finite element method. PMID:25816331

  13. Condition Number Estimation of Preconditioned Matrices

    PubMed Central

    Kushida, Noriyuki

    2015-01-01

    The present paper introduces a condition number estimation method for preconditioned matrices. The newly developed method provides reasonable results, while the conventional method which is based on the Lanczos connection gives meaningless results. The Lanczos connection based method provides the condition numbers of coefficient matrices of systems of linear equations with information obtained through the preconditioned conjugate gradient method. Estimating the condition number of preconditioned matrices is sometimes important when describing the effectiveness of new preconditionerers or selecting adequate preconditioners. Operating a preconditioner on a coefficient matrix is the simplest method of estimation. However, this is not possible for large-scale computing, especially if computation is performed on distributed memory parallel computers. This is because, the preconditioned matrices become dense, even if the original matrices are sparse. Although the Lanczos connection method can be used to calculate the condition number of preconditioned matrices, it is not considered to be applicable to large-scale problems because of its weakness with respect to numerical errors. Therefore, we have developed a robust and parallelizable method based on Hager’s method. The feasibility studies are curried out for the diagonal scaling preconditioner and the SSOR preconditioner with a diagonal matrix, a tri-daigonal matrix and Pei’s matrix. As a result, the Lanczos connection method contains around 10% error in the results even with a simple problem. On the other hand, the new method contains negligible errors. In addition, the newly developed method returns reasonable solutions when the Lanczos connection method fails with Pei’s matrix, and matrices generated with the finite element method. PMID:25816331

  14. Metal filled porous carbon

    DOEpatents

    Gross, Adam F.; Vajo, John J.; Cumberland, Robert W.; Liu, Ping; Salguero, Tina T.

    2011-03-22

    A porous carbon scaffold with a surface and pores, the porous carbon scaffold containing a primary metal and a secondary metal, where the primary metal is a metal that does not wet the surface of the pores of the carbon scaffold but wets the surface of the secondary metal, and the secondary metal is interspersed between the surface of the pores of the carbon scaffold and the primary metal.

  15. Porous airfoil and process

    NASA Technical Reports Server (NTRS)

    Hartwich, Peter M. (Inventor)

    1992-01-01

    A porous airfoil having venting cavities with contoured barrier walls, formed by a core piece, placed beneath a porous upper and lower surface area that stretches over the nominal chord of an airfoil is employed, to provide an airfoil configuration that becomes self-adaptive to very dissimilar flow conditions to thereby improve the lift and drag characteristics of the airfoil at both subcritical and supercritical conditions.

  16. Bayesian Nonparametric Clustering for Positive Definite Matrices.

    PubMed

    Cherian, Anoop; Morellas, Vassilios; Papanikolopoulos, Nikolaos

    2016-05-01

    Symmetric Positive Definite (SPD) matrices emerge as data descriptors in several applications of computer vision such as object tracking, texture recognition, and diffusion tensor imaging. Clustering these data matrices forms an integral part of these applications, for which soft-clustering algorithms (K-Means, expectation maximization, etc.) are generally used. As is well-known, these algorithms need the number of clusters to be specified, which is difficult when the dataset scales. To address this issue, we resort to the classical nonparametric Bayesian framework by modeling the data as a mixture model using the Dirichlet process (DP) prior. Since these matrices do not conform to the Euclidean geometry, rather belongs to a curved Riemannian manifold,existing DP models cannot be directly applied. Thus, in this paper, we propose a novel DP mixture model framework for SPD matrices. Using the log-determinant divergence as the underlying dissimilarity measure to compare these matrices, and further using the connection between this measure and the Wishart distribution, we derive a novel DPM model based on the Wishart-Inverse-Wishart conjugate pair. We apply this model to several applications in computer vision. Our experiments demonstrate that our model is scalable to the dataset size and at the same time achieves superior accuracy compared to several state-of-the-art parametric and nonparametric clustering algorithms. PMID:27046838

  17. Sex Differences in Constitutive Autophagy

    PubMed Central

    Oliván, Sara; Calvo, Ana Cristina; Manzano, Raquel; Zaragoza, Pilar

    2014-01-01

    Sex bias has been described nowadays in biomedical research on animal models, although sexual dimorphism has been confirmed widely under pathological and physiological conditions. The main objective of our work was to study the sex differences in constitutive autophagy in spinal cord and skeletal muscle tissue from wild type mice. To examine the influence of sex on autophagy, mRNA and proteins were extracted from male and female mice tissues. The expressions of microtubule-associated protein 1 light chain 3 (LC3) and sequestosome 1 (p62), markers to monitor autophagy, were analyzed at 40, 60, 90, and 120 days of age. We found significant sex differences in the expression of LC3 and p62 in both tissues at these ages. The results indicated that sex and tissue specific differences exist in constitutive autophagy. These data underlined the need to include both sexes in the experimental groups to minimize any sex bias. PMID:24719882

  18. [Women, gender, and the Constitution].

    PubMed

    1993-12-01

    Although all the constitutions of Latin America directly or indirectly acknowledge the juridical equality of the sexes, these patriarchal societies continue to maintain institutional power in male hands and to neutralize legal actions favoring women. International instruments such as the Convention on Elimination of All Forms of Discrimination Against Women, approved by the UN in 1979, have given a firmer basis to policies and actions to improve the status of women. Obstacles to full equality of Latin American women are rooted in economic and sociopolitical factors, but lack of true political will also plays a significant role. A number of new laws in the past several years as well as the new Constitution have improved the legal position of Colombian women. The new Constitution recognizes fundamental rights that may be claimed directly before a judge, and social, economic, and collective rights requiring legislative development. Article 43 of the new Constitution states that women will not be subjected to any form of discrimination. Another norm states that women will enjoy special assistance and protection before and after childbirth, in recognition of the social functions of maternity. Article 43 also states that women who are heads of households will receive special assistance, but the corresponding regulations have not yet been promulgated. The mechanism of tutelage has become an important recourse that has been used in several cases in which fundamental rights of women have been violated or threatened because of their sex. The order of tutelage has been used in cases of adolescents expelled from school for pregnancy and of abused wives, as well as to force recognition of the social and economic contributions of housework. PMID:12287889

  19. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Lindholm, U. S.; Bodner, S. R.

    1988-01-01

    The third and fourth years of a 4-year research program, part of the NASA HOST Program, are described. The program goals were: (1) to develop and validate unified constitutive models for isotropic materials, and (2) to demonstrate their usefulness for structural analysis of hot section components of gas turbine engines. The unified models selected for development and evaluation were those of Bodner-Partom and of Walker. The unified approach for elastic-viscoplastic constitutive equations is a viable method for representing and predicting material response characteristics in the range where strain rate and temperature dependent inelastic deformations are experienced. This conclusion is reached by extensive comparison of model calculations against the experimental results of a test program of two high temperature Ni-base alloys, B1900+Hf and Mar-M247, over a wide temperature range for a variety of deformation and thermal histories including uniaxial, multiaxial, and thermomechanical loading paths. The applicability of the Bodner-Partom and the Walker models for structural applications has been demonstrated by implementing these models into the MARC finite element code and by performing a number of analyses including thermomechanical histories on components of hot sections of gas turbine engines and benchmark notch tensile specimens. The results of the 4-year program have been published in four annual reports. The results of the base program are summarized in this report. The tasks covered include: (1) development of material test procedures, (2) thermal history effects, and (3) verification of the constitutive model for an alternative material.

  20. Porous matrix structures for alkaline electrolyte fuel cells

    NASA Technical Reports Server (NTRS)

    Vine, R. W.; Narsavage, S. T.

    1975-01-01

    A number of advancements have been realized by a continuing research program to develop higher chemically stable porous matrix structures with high bubble pressure (crossover resistance) for use as separators in potassium hydroxide electrolyte fuel cells. More uniform, higher-bubble-pressure asbestos matrices were produced by reconstituting Johns-Manville asbestos paper; Fybex potassium titanate which was found compatible with 42% KOH at 250 F for up to 3000 hr; good agreement was found between bubble pressures predicted by an analytical study and those measured with filtered structures; Teflon-bonded Fybex matrices with bubble pressures greater than 30 psi were obtained by filtering a water slurry of the mixture directly onto fuel cell electrodes; and PBI fibers have satisfactory compatibility with 42% KOH at 250 F.

  1. Hysteresis of liquid adsorption in porous media by coarse-grained Monte Carlo with direct experimental validation

    NASA Astrophysics Data System (ADS)

    Zeidman, Benjamin D.; Lu, Ning; Wu, David T.

    2016-05-01

    The effects of path-dependent wetting and drying manifest themselves in many types of physical systems, including nanomaterials, biological systems, and porous media such as soil. It is desirable to better understand how these hysteretic macroscopic properties result from a complex interplay between gasses, liquids, and solids at the pore scale. Coarse-Grained Monte Carlo (CGMC) is an appealing approach to model these phenomena in complex pore spaces, including ones determined experimentally. We present two-dimensional CGMC simulations of wetting and drying in two systems with pore spaces determined by sections from micro X-ray computed tomography: a system of randomly distributed spheres and a system of Ottawa sand. Results for the phase distribution, water uptake, and matric suction when corrected for extending to three dimensions show excellent agreement with experimental measurements on the same systems. This supports the hypothesis that CGMC can generate metastable configurations representative of experimental hysteresis and can also be used to predict hysteretic constitutive properties of particular experimental systems, given pore space images.

  2. Hysteresis of liquid adsorption in porous media by coarse-grained Monte Carlo with direct experimental validation.

    PubMed

    Zeidman, Benjamin D; Lu, Ning; Wu, David T

    2016-05-01

    The effects of path-dependent wetting and drying manifest themselves in many types of physical systems, including nanomaterials, biological systems, and porous media such as soil. It is desirable to better understand how these hysteretic macroscopic properties result from a complex interplay between gasses, liquids, and solids at the pore scale. Coarse-Grained Monte Carlo (CGMC) is an appealing approach to model these phenomena in complex pore spaces, including ones determined experimentally. We present two-dimensional CGMC simulations of wetting and drying in two systems with pore spaces determined by sections from micro X-ray computed tomography: a system of randomly distributed spheres and a system of Ottawa sand. Results for the phase distribution, water uptake, and matric suction when corrected for extending to three dimensions show excellent agreement with experimental measurements on the same systems. This supports the hypothesis that CGMC can generate metastable configurations representative of experimental hysteresis and can also be used to predict hysteretic constitutive properties of particular experimental systems, given pore space images. PMID:27155649

  3. Advanced incomplete factorization algorithms for Stiltijes matrices

    SciTech Connect

    Il`in, V.P.

    1996-12-31

    The modern numerical methods for solving the linear algebraic systems Au = f with high order sparse matrices A, which arise in grid approximations of multidimensional boundary value problems, are based mainly on accelerated iterative processes with easily invertible preconditioning matrices presented in the form of approximate (incomplete) factorization of the original matrix A. We consider some recent algorithmic approaches, theoretical foundations, experimental data and open questions for incomplete factorization of Stiltijes matrices which are {open_quotes}the best{close_quotes} ones in the sense that they have the most advanced results. Special attention is given to solving the elliptic differential equations with strongly variable coefficients, singular perturbated diffusion-convection and parabolic equations.

  4. Origin of symmetric PMNS and CKM matrices

    NASA Astrophysics Data System (ADS)

    Rodejohann, Werner; Xu, Xun-Jie

    2015-03-01

    The Pontecorvo-Maki-Nakagawa-Sakata and Cabibbo-Kobayashi-Maskawa matrices are phenomenologically close to symmetric, and a symmetric form could be used as zeroth-order approximation for both matrices. We study the possible theoretical origin of this feature in flavor symmetry models. We identify necessary geometric properties of discrete flavor symmetry groups that can lead to symmetric mixing matrices. Those properties are actually very common in discrete groups such as A4 , S4 , or Δ (96 ) . As an application of our theorem, we generate a symmetric lepton mixing scheme with θ12=θ23=36.21 ° ; θ13=12.20 ° , and δ =0 , realized with the group Δ (96 ) .

  5. Octonion generalization of Pauli and Dirac matrices

    NASA Astrophysics Data System (ADS)

    Chanyal, B. C.

    2015-10-01

    Starting with octonion algebra and its 4 × 4 matrix representation, we have made an attempt to write the extension of Pauli's matrices in terms of division algebra (octonion). The octonion generalization of Pauli's matrices shows the counterpart of Pauli's spin and isospin matrices. In this paper, we also have obtained the relationship between Clifford algebras and the division algebras, i.e. a relation between octonion basis elements with Dirac (gamma), Weyl and Majorana representations. The division algebra structure leads to nice representations of the corresponding Clifford algebras. We have made an attempt to investigate the octonion formulation of Dirac wave equations, conserved current and weak isospin in simple, compact, consistent and manifestly covariant manner.

  6. The Constitution: Perspectives on Contemporary American Democracy.

    ERIC Educational Resources Information Center

    Close Up Foundation, Arlington, VA.

    Four articles expressing the views of nine prominent United States citizens about the Constitution provide a context for reflecting on the meaning of the Constitution in present-day America. In "Why Has the Constitution Endured So Long?" Don Edwards, chairman of the House Civil and Constitutional Rights Subcommittee, discusses why the Constitution…

  7. Fast transforms: Banded matrices with banded inverses

    PubMed Central

    Strang, Gilbert

    2010-01-01

    It is unusual for both A and A-1 to be banded—but this can be a valuable property in applications. Block-diagonal matrices F are the simplest examples; wavelet transforms are more subtle. We show that every example can be factored into A = F1…FN where N is controlled by the bandwidths of A and A-1 (but not by their size, so this extends to infinite matrices and leads to new matrix groups). PMID:20615937

  8. Sparse Matrices in MATLAB: Design and Implementation

    NASA Technical Reports Server (NTRS)

    Gilbert, John R.; Moler, Cleve; Schreiber, Robert

    1992-01-01

    The matrix computation language and environment MATLAB is extended to include sparse matrix storage and operations. The only change to the outward appearance of the MATLAB language is a pair of commands to create full or sparse matrices. Nearly all the operations of MATLAB now apply equally to full or sparse matrices, without any explicit action by the user. The sparse data structure represents a matrix in space proportional to the number of nonzero entries, and most of the operations compute sparse results in time proportional to the number of arithmetic operations on nonzeros.

  9. Spectral properties of ghost Neumann matrices

    SciTech Connect

    Bonora, L.; Santos, R. J. Scherer; Tolla, D. D.

    2008-05-15

    We continue the analysis of the ghost wedge states in the oscillator formalism by studying the spectral properties of the ghost matrices of Neumann coefficients. We show that the traditional spectral representation is not valid for these matrices and propose a new heuristic formula that allows one to reconstruct them from the knowledge of their eigenvalues and eigenvectors. It turns out that additional data, which we call boundary data, are needed in order to actually implement the reconstruction. In particular our result lends support to the conjecture that there exists a ghost three strings vertex with properties parallel to those of the matter three strings vertex.

  10. Cryogenic cooling of x-ray crystals using porous matrix

    SciTech Connect

    Kuzay, T.M.

    1991-01-01

    It is well established that Si and SiC have very desirable thermophysical properties at cryogenic temperatures. This feature makes cryo-cooled optics potentially a good candidate for the first optical crystal of the presently built third generation synchrotron machines with very high heat flux levels. Currently, there is a great deal of interest in such cryo-cooled crystals pursued both experimentally and analytically. The analytical studies involve cut micro or capillary channel crystals. As opposed to the machined channels, porous matrices provide significant advantages. They operate very quietly. Such matrices are known to affect superior heat transfer enhancement. Data available in open literature suggest that surface heat flux levels up to {approximately}8 kW/cm{sup 2} are possible. For cryogens for which the boiling heat transfer heat flux is rather a low value in conventional geometries, the enhancement available with such matrices is a very significant characteristic. Cryogens are poor thermal conductors themselves. The fact that at the cryogenic temperatures the Si and/or SiC matrix itself becomes highly conductive, the matrix distributes the surface heat flux into the full volume effectively offsetting the poor conductivity of the coolant. In addition the tortuous path of the coolant through the matrix increases the dwell time for better heat transfer, however, at the expense of increased pressure drop. In this study, thermal conductivity of such composite matrices and the effective heat transfer coefficient obtainable using them are investigated. A first optics crystal model of Si with Si and/or Sic porous matrix as its heat exchanger and subject to prototype synchrotron level heat flux is analyzed and limits of the cooling possible with liquid nitrogen in single phase and subcooled boiling heat transfer modes are delineated.

  11. Constitutive upscaling of MR fluids

    NASA Astrophysics Data System (ADS)

    Nika, Grigor; Vernescu, Bogdan

    2015-11-01

    We consider a suspension of solid magnetizable particles in a viscous fluid with an applied external magnetic field. We assume the fluid to be electrically non-conducting. Thus, we use the quasi-static Maxwell equations coupled with the Stokes equations to capture the magnetorheological effect. We upscale using two scale asymptotic expansions to obtain the effective equations consisting of a coupled nonlinear system in a connected phase domain as well as the new constitutive laws. Qualitative properties of the solution of this nonlinear system are studied.

  12. A probabilistic model of a porous heat exchanger

    NASA Technical Reports Server (NTRS)

    Agrawal, O. P.; Lin, X. A.

    1995-01-01

    This paper presents a probabilistic one-dimensional finite element model for heat transfer processes in porous heat exchangers. The Galerkin approach is used to develop the finite element matrices. Some of the submatrices are asymmetric due to the presence of the flow term. The Neumann expansion is used to write the temperature distribution as a series of random variables, and the expectation operator is applied to obtain the mean and deviation statistics. To demonstrate the feasibility of the formulation, a one-dimensional model of heat transfer phenomenon in superfluid flow through a porous media is considered. Results of this formulation agree well with the Monte-Carlo simulations and the analytical solutions. Although the numerical experiments are confined to parametric random variables, a formulation is presented to account for the random spatial variations.

  13. Foams in porous media

    SciTech Connect

    Marsden, S.S.

    1986-07-01

    In 1978 a literature search on selective blocking of fluid flow in porous media was done by Professor S.S. Marsden and two of his graduate students, Tom Elson and Kern Huppy. This was presented as SUPRI Report No. TR-3 entitled ''Literature Preview of the Selected Blockage of Fluids in Thermal Recovery Projects.'' Since then a lot of research on foam in porous media has been done on the SUPRI project and a great deal of new information has appeared in the literature. Therefore we believed that a new, up-to-date search should be done on foam alone, one which would be helpful to our students and perhaps of interest to others. This is a chronological survey showing the development of foam flow, blockage and use in porous media, starting with laboratory studies and eventually getting into field tests and demonstrations. It is arbitrarily divided into five-year time periods. 81 refs.

  14. Porous material neutron detector

    DOEpatents

    Diawara, Yacouba; Kocsis, Menyhert

    2012-04-10

    A neutron detector employs a porous material layer including pores between nanoparticles. The composition of the nanoparticles is selected to cause emission of electrons upon detection of a neutron. The nanoparticles have a maximum dimension that is in the range from 0.1 micron to 1 millimeter, and can be sintered with pores thereamongst. A passing radiation generates electrons at one or more nanoparticles, some of which are scattered into a pore and directed toward a direction opposite to the applied electrical field. These electrons travel through the pore and collide with additional nanoparticles, which generate more electrons. The electrons are amplified in a cascade reaction that occurs along the pores behind the initial detection point. An electron amplification device may be placed behind the porous material layer to further amplify the electrons exiting the porous material layer.

  15. FLUID TRANSPORT THROUGH POROUS MEDIA

    EPA Science Inventory

    Fluid transport through porous media is a relevant topic to many scientific and engineering fields. Soil scientists, civil engineers, hydrologists and hydrogeologists are concerned with the transport of water, gases and nonaqueous phase liquid contaminants through porous earth m...

  16. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Ramaswamy, V. G.; Vanstone, R. H.; Dame, L. T.; Laflen, J. H.

    1985-01-01

    The first year of progress on a NASA-Lewis contract with the General Electric Co is documented. The purpose of this contract (NAS3-23927) is to develop and evaluate unified constitutive equations for applications to hot-path components of aircraft gas turbine engines such as high pressure turbine blades and vanes. To accomplish this goal, uniaxial, notched, and multiaxial specimens made of conventionally cast Rene 80 are being tested under conditions that simulate engine operating conditions. To reduce the raw data, automated data reduction techniques are being developed that produce computer files containing the information needed to analyze proposed constitutive theories. Described are the analytical methods being developed to determine the parameters for these nonlinear unified theories by using the reduced data files. In another activity, a dedicated finite-element computer code is being developed to use unified theories in the structural analysis of hot-section components. This code was extensively verified for one such theory by successfully predicting the strain histories measured experimentally at the notch root of complex specimens taken from complex laboratory specimens.

  17. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Lindholm, Ulric S.; Chan, Kwai S.

    1986-01-01

    The objective of the program is to evaluate and develop existing constitutive models for use in finite-element structural analysis of turbine engine hot section components. The class of constitutive equation studied is considered unified in that all inelastic deformation including plasticity, creep, and stress relaxation are treated in a single term rather than a classical separation of plasticity (time independent) and creep (time dependent) behavior. The unified theories employed also do not utilize the classical yield surface or plastic potential concept. The models are constructed from an appropriate flow law, a scalar kinetic relation between strain rate, temperature and stress, and evolutionary equations for internal variables describing strain or work hardening, both isotropic and directional (kinematic). This and other studies have shown that the unified approach is particularly suited for determining the cyclic behavior of superalloy type blade and vane materials and is entirely compatible with three-dimensional inelastic finite-element formulations. The behavior was examined of a second nickel-base alloy, MAR-M247, and compared it with the Bodner-Partom model, further examined procedures for determining the material-specific constants in the models, and exercised the MARC code for a turbine blade under simulated flight spectrum loading. Results are summarized.

  18. Parameterized BLOSUM Matrices for Protein Alignment.

    PubMed

    Song, Dandan; Chen, Jiaxing; Chen, Guang; Li, Ning; Li, Jin; Fan, Jun; Bu, Dongbo; Li, Shuai Cheng

    2015-01-01

    Protein alignment is a basic step for many molecular biology researches. The BLOSUM matrices, especially BLOSUM62, are the de facto standard matrices for protein alignments. However, after widely utilization of the matrices for 15 years, programming errors were surprisingly found in the initial version of source codes for their generation. And amazingly, after bug correction, the "intended" BLOSUM62 matrix performs consistently worse than the "miscalculated" one. In this paper, we find linear relationships among the eigenvalues of the matrices and propose an algorithm to find optimal unified eigenvectors. With them, we can parameterize matrix BLOSUMx for any given variable x that could change continuously. We compare the effectiveness of our parameterized isentropic matrix with BLOSUM62. Furthermore, an iterative alignment and matrix selection process is proposed to adaptively find the best parameter and globally align two sequences. Experiments are conducted on aligning 13,667 families of Pfam database and on clustering MHC II protein sequences, whose improved accuracy demonstrates the effectiveness of our proposed method. PMID:26357279

  19. Malware Analysis Using Visualized Image Matrices

    PubMed Central

    Im, Eul Gyu

    2014-01-01

    This paper proposes a novel malware visual analysis method that contains not only a visualization method to convert binary files into images, but also a similarity calculation method between these images. The proposed method generates RGB-colored pixels on image matrices using the opcode sequences extracted from malware samples and calculates the similarities for the image matrices. Particularly, our proposed methods are available for packed malware samples by applying them to the execution traces extracted through dynamic analysis. When the images are generated, we can reduce the overheads by extracting the opcode sequences only from the blocks that include the instructions related to staple behaviors such as functions and application programming interface (API) calls. In addition, we propose a technique that generates a representative image for each malware family in order to reduce the number of comparisons for the classification of unknown samples and the colored pixel information in the image matrices is used to calculate the similarities between the images. Our experimental results show that the image matrices of malware can effectively be used to classify malware families both statically and dynamically with accuracy of 0.9896 and 0.9732, respectively. PMID:25133202

  20. Malware analysis using visualized image matrices.

    PubMed

    Han, KyoungSoo; Kang, BooJoong; Im, Eul Gyu

    2014-01-01

    This paper proposes a novel malware visual analysis method that contains not only a visualization method to convert binary files into images, but also a similarity calculation method between these images. The proposed method generates RGB-colored pixels on image matrices using the opcode sequences extracted from malware samples and calculates the similarities for the image matrices. Particularly, our proposed methods are available for packed malware samples by applying them to the execution traces extracted through dynamic analysis. When the images are generated, we can reduce the overheads by extracting the opcode sequences only from the blocks that include the instructions related to staple behaviors such as functions and application programming interface (API) calls. In addition, we propose a technique that generates a representative image for each malware family in order to reduce the number of comparisons for the classification of unknown samples and the colored pixel information in the image matrices is used to calculate the similarities between the images. Our experimental results show that the image matrices of malware can effectively be used to classify malware families both statically and dynamically with accuracy of 0.9896 and 0.9732, respectively. PMID:25133202

  1. Spectral averaging techniques for Jacobi matrices

    SciTech Connect

    Rio, Rafael del; Martinez, Carmen; Schulz-Baldes, Hermann

    2008-02-15

    Spectral averaging techniques for one-dimensional discrete Schroedinger operators are revisited and extended. In particular, simultaneous averaging over several parameters is discussed. Special focus is put on proving lower bounds on the density of the averaged spectral measures. These Wegner-type estimates are used to analyze stability properties for the spectral types of Jacobi matrices under local perturbations.

  2. Multifunctional matrices for oral peptide delivery.

    PubMed

    Bernkop-Schnürch, A; Walker, G

    2001-01-01

    The oral administration of peptide drugs represents one of the greatest challenges in pharmaceutical technology. To gain a sufficient bioavailability of these therapeutic agents, various barriers including the mucus-layer barrier, the enzymatic barrier, and the membrane barrier have to be overcome. A promising strategy for achieving this goal is the use of multifunctional matrices. These matrices are based on polymers that display mucoadhesive properties, a permeation-enhancing effect, enzyme-inhibiting properties, and/or a high buffer capacity. Moreover, a sustained or delayed drug release can be provided by delivery systems that contain such polymers. Among them, polyacrylates, cellulose derivatives, and chitosan are promising excipients that can also be customized by chemical modification to improve certain properties. For example, the covalent attachment of thiol moieties on these polymers leads to improved mucoadhesive and permeation-enhancing properties, and the conjugation of enzyme inhibitors enables the matrices to provide protection for peptide drugs against enzymatic degradation. The efficacy of multifunctional matrices in oral peptide delivery has been verified by various in vivo studies that could pave the way for the development of commercially viable formulations. PMID:11763498

  3. SPECIATION OF ARSENIC IN EXPOSURE ASSESSMENT MATRICES

    EPA Science Inventory

    The speciaton of arsenic in water, food and urine are analytical capabilities which are an essential part in arsenic risk assessment. The cancer risk associated with arsenic has been the driving force in generating the analytical research in each of these matrices. This presentat...

  4. Constructing random matrices to represent real ecosystems.

    PubMed

    James, Alex; Plank, Michael J; Rossberg, Axel G; Beecham, Jonathan; Emmerson, Mark; Pitchford, Jonathan W

    2015-05-01

    Models of complex systems with n components typically have order n(2) parameters because each component can potentially interact with every other. When it is impractical to measure these parameters, one may choose random parameter values and study the emergent statistical properties at the system level. Many influential results in theoretical ecology have been derived from two key assumptions: that species interact with random partners at random intensities and that intraspecific competition is comparable between species. Under these assumptions, community dynamics can be described by a community matrix that is often amenable to mathematical analysis. We combine empirical data with mathematical theory to show that both of these assumptions lead to results that must be interpreted with caution. We examine 21 empirically derived community matrices constructed using three established, independent methods. The empirically derived systems are more stable by orders of magnitude than results from random matrices. This consistent disparity is not explained by existing results on predator-prey interactions. We investigate the key properties of empirical community matrices that distinguish them from random matrices. We show that network topology is less important than the relationship between a species' trophic position within the food web and its interaction strengths. We identify key features of empirical networks that must be preserved if random matrix models are to capture the features of real ecosystems. PMID:25905510

  5. Noisy covariance matrices and portfolio optimization

    NASA Astrophysics Data System (ADS)

    Pafka, S.; Kondor, I.

    2002-05-01

    According to recent findings [#!bouchaud!#,#!stanley!#], empirical covariance matrices deduced from financial return series contain such a high amount of noise that, apart from a few large eigenvalues and the corresponding eigenvectors, their structure can essentially be regarded as random. In [#!bouchaud!#], e.g., it is reported that about 94% of the spectrum of these matrices can be fitted by that of a random matrix drawn from an appropriately chosen ensemble. In view of the fundamental role of covariance matrices in the theory of portfolio optimization as well as in industry-wide risk management practices, we analyze the possible implications of this effect. Simulation experiments with matrices having a structure such as described in [#!bouchaud!#,#!stanley!#] lead us to the conclusion that in the context of the classical portfolio problem (minimizing the portfolio variance under linear constraints) noise has relatively little effect. To leading order the solutions are determined by the stable, large eigenvalues, and the displacement of the solution (measured in variance) due to noise is rather small: depending on the size of the portfolio and on the length of the time series, it is of the order of 5 to 15%. The picture is completely different, however, if we attempt to minimize the variance under non-linear constraints, like those that arise e.g. in the problem of margin accounts or in international capital adequacy regulation. In these problems the presence of noise leads to a serious instability and a high degree of degeneracy of the solutions.

  6. On reduced density matrices for disjoint subsystems

    NASA Astrophysics Data System (ADS)

    Iglói, F.; Peschel, I.

    2010-02-01

    We show that spin and fermion representations for solvable quantum chains lead in general to different reduced density matrices if the subsystem is not singly connected. We study the effect for two sites in XX and XY chains as well as for sublattices in XX and transverse Ising chains.

  7. Chemically Layered Porous Solids

    NASA Technical Reports Server (NTRS)

    Koontz, Steve

    1991-01-01

    Aerogels and other porous solids in which surfaces of pores have chemical properties varying with depth below macroscopic surfaces prepared by sequences of chemical treatments. Porous glass or silica bead treated to make two depth zones having different chemical properties. Beads dropped along tube filled with flowing gas containing atomic oxygen, generated in microwave discharge. General class of materials treatable include oxides of aluminum, silicon, zirconium, tin, titanium, and nickel, and mixtures of these oxides. Potential uses of treated materials include chromatographic separations, membrane separations, controlled releases of chemicals, and catalysis.

  8. Porous silicon gettering

    SciTech Connect

    Tsuo, Y.S.; Menna, P.; Pitts, J.R.

    1996-05-01

    The authors have studied a novel extrinsic gettering method that uses the large surface areas produced by a porous-silicon etch as gettering sites. The annealing step of the gettering used a high-flux solar furnace. They found that a high density of photons during annealing enhanced the impurity diffusion to the gettering sites. The authors used metallurgical-grade Si (MG-Si) prepared by directional solidification casing as the starting material. They propose to use porous-silicon-gettered MG-Si as a low-cost epitaxial substrate for polycrystalline silicon thin-film growth.

  9. Porous block nanofiber composite filters

    DOEpatents

    Ginley, David S.; Curtis, Calvin J.; Miedaner, Alexander; Weiss, Alan J.; Paddock, Arnold

    2016-08-09

    Porous block nano-fiber composite (110), a filtration system (10) and methods of using the same are disclosed. An exemplary porous block nano-fiber composite (110) includes a porous block (100) having one or more pores (200). The porous block nano-fiber composite (110) also includes a plurality of inorganic nano-fibers (211) formed within at least one of the pores (200).

  10. Porous metal for orthopedics implants

    PubMed Central

    Matassi, Fabrizio; Botti, Alessandra; Sirleo, Luigi; Carulli, Christian; Innocenti, Massimo

    2013-01-01

    Summary Porous metal has been introduced to obtain biological fixation and improve longevity of orthopedic implants. The new generation of porous metal has intriguing characteristics that allows bone healing and high osteointegration of the metallic implants. This article gives an overview about biomaterials properties of the contemporary class of highly porous metals and about the clinical use in orthopaedic surgery. PMID:24133527

  11. Porous silicon biosensor: current status.

    PubMed

    Dhanekar, Saakshi; Jain, Swati

    2013-03-15

    Biosensing technologies cater to modern day diagnostics and point of care multi-specialty clinics, hospitals and laboratories. Biosensors aggregate the sensitivity of detection methodologies and constitutional selectivity of biomolecules. Endeavors to develop highly sensitive, fast, stable and low cost biosensors have been made possible by extensive and arduous research. Immense research work is going on for detection of molecules using various materials as immobilization substrate and sensing elements. Amongst materials being used as bio-sensing substrates, nano-porous silicon (PS) has amassed attention and gained popularity in recent years. It has captivating and tunable features like ease of fabrication, special optico-physico properties, tailored morphological structure and versatile surface chemistry enhancing its prospects as transducer for fabricating biosensors. The present review describes the fabrication of PS and its biosensing capabilities for detection of various analytes including, but not limited to, glucose, DNA, antibodies, bacteria and viruses. Attention has been consecrated on the various methodologies such as electrical, electrochemical, optical and label free techniques along with the performances of these biosensors. It concludes with some future prospects and challenges of PS based biosensors. PMID:23122704

  12. Unborn children as constitutional persons.

    PubMed

    Roden, Gregory J

    2010-01-01

    In Roe v. Wade, the state of Texas argued that "the fetus is a 'person' within the language and meaning of the Fourteenth Amendment." To which Justice Harry Blackmun responded, "If this suggestion of personhood is established, the appellant's case, of course, collapses, for the fetus' right to life would then be guaranteed specifically by the Amendment." However, Justice Blackmun then came to the conclusion "that the word 'person,' as used in the Fourteenth Amendment, does not include the unborn." In this article, it is argued that unborn children are indeed "persons" within the language and meaning of the Fourteenth and Fifth Amendments. As there is no constitutional text explicitly holding unborn children to be, or not to be, "persons," this argument will be based on the "historical understanding and practice, the structure of the Constitution, and thejurisprudence of [the Supreme] Court." Specifically, it is argued that the Constitution does not confer upon the federal government a specifically enumerated power to grant or deny "personhood" under the Fourteenth Amendment. Rather, the power to recognize or deny unborn children as the holders of rights and duties has been historically exercised by the states. The Roe opinion and other Supreme Court cases implicitly recognize this function of state sovereignty. The states did exercise this power and held unborn children to be persons under the property, tort, and criminal law of the several states at the time Roe was decided. As an effect of the unanimity of the states in holding unborn children to be persons under criminal, tort, and property law, the text of the Equal Protection Clause of the Fourteenth Amendment compels federal protection of unborn persons. Furthermore, to the extent Justice Blackmun examined the substantive law in these disciplines, his findings are clearly erroneous and as a whole amount to judicial error. Moreover, as a matter of procedure, according to the due process standards recognized in

  13. Porous metallic bodies

    DOEpatents

    Landingham, R.L.

    1984-03-13

    Porous metallic bodies having a substantially uniform pore size of less than about 200 microns and a density of less than about 25 percent theoretical, as well as the method for making them, are disclosed. Group IIA, IIIB, IVB, VB, and rare earth metal hydrides a

  14. Hydrophobic, Porous Battery Boxes

    NASA Technical Reports Server (NTRS)

    Bragg, Bobby J.; Casey, John E., Jr.

    1995-01-01

    Boxes made of porous, hydrophobic polymers developed to contain aqueous potassium hydroxide electrolyte solutions of zinc/air batteries while allowing air to diffuse in as needed for operation. Used on other types of batteries for in-cabin use in which electrolytes aqueous and from which gases generated during operation must be vented without allowing electrolytes to leak out.

  15. POROUS DIKE INTAKE EVALUATION

    EPA Science Inventory

    The report gives results of an evaluation of a porous dike intake. A small-scale test facility was constructed and continuously operated for 2 years under field conditions. Two stone dikes of gabion construction were tested: one consisted of 7.5 cm stones; and the other, 20 cm st...

  16. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301,...

  17. Improved Separability Criteria Based on Bloch Representation of Density Matrices.

    PubMed

    Shen, Shu-Qian; Yu, Juan; Li, Ming; Fei, Shao-Ming

    2016-01-01

    The correlation matrices or tensors in the Bloch representation of density matrices are encoded with entanglement properties. In this paper, based on the Bloch representation of density matrices, we give some new separability criteria for bipartite and multipartite quantum states. Theoretical analysis and some examples show that the proposed criteria can be more efficient than the previous related criteria. PMID:27350031

  18. Improved Separability Criteria Based on Bloch Representation of Density Matrices

    PubMed Central

    Shen, Shu-Qian; Yu, Juan; Li, Ming; Fei, Shao-Ming

    2016-01-01

    The correlation matrices or tensors in the Bloch representation of density matrices are encoded with entanglement properties. In this paper, based on the Bloch representation of density matrices, we give some new separability criteria for bipartite and multipartite quantum states. Theoretical analysis and some examples show that the proposed criteria can be more efficient than the previous related criteria. PMID:27350031

  19. Written Constitution or None: Which Works Better?

    ERIC Educational Resources Information Center

    Cowen, Zelman

    1987-01-01

    Explores the differences between the U.S. Constitution and British constitutional law. Specifically examines the concept of the U.S. Bill of Rights in relation to the United Kingdom common law doctrine of parliamentary sovereignty. (BSR)

  20. Mössbauer Investigation of Highly Dispersed Iron Particles in Crazed Porous Polymers

    NASA Astrophysics Data System (ADS)

    Trofimchuk, E. S.; Nikonorova, N. I.; Dedushenko, S. K.; Perfiliev, Y. D.

    2004-12-01

    Formation and stability of highly dispersed iron particles in crazed porous polymer matrices were studied. The iron polymer composites obtained were characterized by different morphologies and dimensions of iron particles. The phase content of the iron constituent in a composite studied by Mössbauer spectroscopy was shown to depend on the type of the iron salt and the method of introduction of the initial reagents into a polymer.

  1. 17 CFR 200.54 - Constitutional obligations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 2 2010-04-01 2010-04-01 false Constitutional obligations... ORGANIZATION; CONDUCT AND ETHICS; AND INFORMATION AND REQUESTS Canons of Ethics § 200.54 Constitutional... against any infringement of the constitutional rights, privileges, or immunities of those who are...

  2. The Constitutional Politics of Charitable Choice.

    ERIC Educational Resources Information Center

    Knippenberg, Joseph M.

    2003-01-01

    Clarifies the constitutional issue raised by government efforts to cooperate with faith-based organizations, noting that while programs can be constitutional without necessarily being good public policy, too frequently political and constitutional controversies mix these two considerations, thus confusing those trying to understand and resolve…

  3. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Constitutional torts. 536.42 Section 536.42... AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim... any subpart. A constitutional claim will be scrutinized in order to determine whether it is totally...

  4. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to implement... this section. The constitution and identification of land as a farm for the first time and...

  5. American Focus on World Constitutions. Teacher's Guide.

    ERIC Educational Resources Information Center

    Holmes, Stanley T., III

    This curriculum project was designed to familiarize high school students with their own constitutional roots while gaining a better understanding of governmental systems developed by other nations. The project uses the U.S. Constitution as a baseline for analyzing the constitutions of other nations, and is intended to supplement courses in such…

  6. About Our Constitution: 1787-1987.

    ERIC Educational Resources Information Center

    National Council for the Social Studies, Washington, DC.

    Designed to assist elementary school teachers, these materials present a series of lessons about the United States Constitution. Ten lesson plans and appropriate work sheets are included for grades K-3. The topics covered include the age of the Constitution, a constitutional convention, elected representatives, majority rule, voting, law making,…

  7. State Constitutional Law: Teaching and Scholarship.

    ERIC Educational Resources Information Center

    Williams, Robert F.

    1991-01-01

    State constitutional law is an emerging area for legal education, partly because of state supreme court decisions relying on state rather than federal constitutional law. Studying state constitutional law highlights similarities and diversity of legal and governmental systems. Interest in establishment of curricula and materials in state law is…

  8. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  9. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  10. Antithetical Ethics: Kenneth Burke and the Constitution.

    ERIC Educational Resources Information Center

    Anderson, Virginia

    1995-01-01

    Shows how the textuality of the United States Constitution, the most venerable of classic democratic icons, might be exploited to nurture postmodern ethics. Shows how Kenneth Burke's reading of the Constitution accords with and augments the postmodern theories of J.-F. Lyotard and S. Jarratt. Discusses a postmodern Constitution and the…

  11. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  12. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  13. Bioisosteric matrices for ligands of serotonin receptors.

    PubMed

    Warszycki, Dawid; Mordalski, Stefan; Staroń, Jakub; Bojarski, Andrzej J

    2015-04-01

    The concept of bioisosteric replacement matrices is applied to explore the chemical space of serotonin receptor ligands, aiming to determine the most efficient ways of manipulating the affinity for all 5-HT receptor subtypes. Analysis of a collection of over 1 million bioisosteres of compounds with measured activity towards serotonin receptors revealed that an average of 31 % of the ligands for each target are mutual bioisosteres. In addition, the collected dataset allowed the development of bioisosteric matrices-qualitative and quantitative descriptions of the biological effects of each predefined type of bioisosteric substitution, providing favored paths of modifying the compounds. The concept exemplified here for serotonin receptor ligands can likely be more broadly applied to other target classes, thus representing a useful guide for medicinal chemists designing novel ligands. PMID:25772514

  14. Evolutionary Games with Randomly Changing Payoff Matrices

    NASA Astrophysics Data System (ADS)

    Yakushkina, Tatiana; Saakian, David B.; Bratus, Alexander; Hu, Chin-Kun

    2015-06-01

    Evolutionary games are used in various fields stretching from economics to biology. In most of these games a constant payoff matrix is assumed, although some works also consider dynamic payoff matrices. In this article we assume a possibility of switching the system between two regimes with different sets of payoff matrices. Potentially such a model can qualitatively describe the development of bacterial or cancer cells with a mutator gene present. A finite population evolutionary game is studied. The model describes the simplest version of annealed disorder in the payoff matrix and is exactly solvable at the large population limit. We analyze the dynamics of the model, and derive the equations for both the maximum and the variance of the distribution using the Hamilton-Jacobi equation formalism.

  15. Approximate inverse preconditioners for general sparse matrices

    SciTech Connect

    Chow, E.; Saad, Y.

    1994-12-31

    Preconditioned Krylov subspace methods are often very efficient in solving sparse linear matrices that arise from the discretization of elliptic partial differential equations. However, for general sparse indifinite matrices, the usual ILU preconditioners fail, often because of the fact that the resulting factors L and U give rise to unstable forward and backward sweeps. In such cases, alternative preconditioners based on approximate inverses may be attractive. We are currently developing a number of such preconditioners based on iterating on each column to get the approximate inverse. For this approach to be efficient, the iteration must be done in sparse mode, i.e., we must use sparse-matrix by sparse-vector type operatoins. We will discuss a few options and compare their performance on standard problems from the Harwell-Boeing collection.

  16. Hydraulic properties of adsorbed water films in unsaturated porous media

    SciTech Connect

    Tokunaga, Tetsu K.

    2009-03-01

    Adsorbed water films strongly influence residual water saturations and hydraulic conductivities in porous media at low saturations. Hydraulic properties of adsorbed water films in unsaturated porous media were investigated through combining Langmuir's film model with scaling analysis, without use of any adjustable parameters. Diffuse double layer influences are predicted to be important through the strong dependence of adsorbed water film thickness (f) on matric potential ({Psi}) and ion charge (z). Film thickness, film velocity, and unsaturated hydraulic conductivity are predicted to vary with z{sup -1}, z{sup -2}, and z{sup -3}, respectively. In monodisperse granular media, the characteristic grain size ({lambda}) controls film hydraulics through {lambda}{sup -1} scaling of (1) the perimeter length per unit cross sectional area over which films occur, (2) the critical matric potential ({Psi}{sub c}) below which films control flow, and (3) the magnitude of the unsaturated hydraulic conductivity when {Psi} < {Psi}{sub c}. While it is recognized that finer textured sediments have higher unsaturated hydraulic conductivities than coarser sands at intermediate {Psi}, the {lambda}{sup -1} scaling of hydraulic conductivity predicted here extends this understanding to very low saturations where all pores are drained. Extremely low unsaturated hydraulic conductivities are predicted under adsorbed film-controlled conditions (generally < 0.1 mm y{sup -1}). On flat surfaces, the film hydraulic diffusivity is shown to be constant (invariant with respect to {Psi}).

  17. Porous silicon microcavities: synthesis, characterization, and application to photonic barcode devices

    NASA Astrophysics Data System (ADS)

    Ramiro-Manzano, Fernando; Fenollosa, Roberto; Xifré-Pérez, Elisabet; Garín, Moises; Meseguer, Francisco

    2012-09-01

    We have recently developed a new type of porous silicon we name as porous silicon colloids. They consist of almost perfect spherical silicon nanoparticles with a very smooth surface, able to scatter (and also trap) light very efficiently in a large-span frequency range. Porous silicon colloids have unique properties because of the following: (a) they behave as optical microcavities with a high refractive index, and (b) the intrinsic photoluminescence (PL) emission is coupled to the optical modes of the microcavity resulting in a unique luminescence spectrum profile. The PL spectrum constitutes an optical fingerprint identifying each particle, with application for biosensing. In this paper, we review the synthesis of silicon colloids for developing porous nanoparticles. We also report on the optical properties with special emphasis in the PL emission of porous silicon microcavities. Finally, we present the photonic barcode concept.

  18. Porous silicon microcavities: synthesis, characterization, and application to photonic barcode devices

    PubMed Central

    2012-01-01

    We have recently developed a new type of porous silicon we name as porous silicon colloids. They consist of almost perfect spherical silicon nanoparticles with a very smooth surface, able to scatter (and also trap) light very efficiently in a large-span frequency range. Porous silicon colloids have unique properties because of the following: (a) they behave as optical microcavities with a high refractive index, and (b) the intrinsic photoluminescence (PL) emission is coupled to the optical modes of the microcavity resulting in a unique luminescence spectrum profile. The PL spectrum constitutes an optical fingerprint identifying each particle, with application for biosensing. In this paper, we review the synthesis of silicon colloids for developing porous nanoparticles. We also report on the optical properties with special emphasis in the PL emission of porous silicon microcavities. Finally, we present the photonic barcode concept. PMID:22943136

  19. Determination of W states equivalent under stochastic local operations and classical communication by their bipartite reduced density matrices with tree form

    NASA Astrophysics Data System (ADS)

    Wu, Xia; Tian, Guo-Jing; Huang, Wei; Wen, Qiao-Yan; Qin, Su-Juan; Gao, Fei

    2014-07-01

    It has been known that, among pure states, N-qubit W states cannot be uniquely determined by their arbitrary (N-1) bipartite reduced density matrices. Parashar and Rana proved that among arbitrary states, (N-1) bipartite reduced density matrices that the pairs of qubits constitute a star graph or a line graph can uniquely determine stochastic local operations and classical communication (SLOCC) equivalent W states, and we generalize this conclusion into tree graph. In this paper, we show that all SLOCC equivalent W states can be uniquely determined (among pure, mixed states) by their (N-1) bipartite reduced density matrices, if the (N-1) pairs of qubits constitute a tree graph on N vertices, where each pair of qubits represents an edge.

  20. Some physical applications of random hierarchical matrices

    SciTech Connect

    Avetisov, V. A.; Bikulov, A. Kh.; Vasilyev, O. A.; Nechaev, S. K.; Chertovich, A. V.

    2009-09-15

    The investigation of spectral properties of random block-hierarchical matrices as applied to dynamic and structural characteristics of complex hierarchical systems with disorder is proposed for the first time. Peculiarities of dynamics on random ultrametric energy landscapes are discussed and the statistical properties of scale-free and polyscale (depending on the topological characteristics under investigation) random hierarchical networks (graphs) obtained by multiple mapping are considered.

  1. Analysis of thematic map classification error matrices.

    USGS Publications Warehouse

    Rosenfield, G.H.

    1986-01-01

    The classification error matrix expresses the counts of agreement and disagreement between the classified categories and their verification. Thematic mapping experiments compare variables such as multiple photointerpretation or scales of mapping, and produce one or more classification error matrices. This paper presents a tutorial to implement a typical problem of a remotely sensed data experiment for solution by the linear model method.-from Author

  2. Photochromic Behavior of Spiropyran in Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Tork, Amir; Boudreault, Francois; Roberge, Mathieu; Ritcey, Anna M.; Lessard, Roger A.; Galstian, Tigran V.

    2001-03-01

    The photoexcitation, relaxation, and optical erasure regimes of spiropyran- (SP-) doped polymer films were studied. Cellulose acetate, poly(vinyl acetate), and poly(methyl methacrylate) (PMMA) were used as host polymer matrices. We studied the character of the photoreaction for both coloring and bleaching processes. Reversible holographic recording in SP -PMMA films and the origin of the photochemical fatigue was studied upon repeated UV -visible irradiation cycles.

  3. Preconditioning matrices for Chebyshev derivative operators

    NASA Technical Reports Server (NTRS)

    Rothman, Ernest E.

    1986-01-01

    The problem of preconditioning the matrices arising from pseudo-spectral Chebyshev approximations of first order operators is considered in both one and two dimensions. In one dimension a preconditioner represented by a full matrix which leads to preconditioned eigenvalues that are real, positive, and lie between 1 and pi/2, is already available. Since there are cases in which it is not computationally convenient to work with such a preconditioner, a large number of preconditioners were studied which were more sparse (in particular three and four diagonal matrices). The eigenvalues of such preconditioned matrices are compared. The results were applied to the problem of finding the steady state solution to an equation of the type u sub t = u sub x + f, where the Chebyshev collocation is used for the spatial variable and time discretization is performed by the Richardson method. In two dimensions different preconditioners are proposed for the matrix which arises from the pseudo-spectral discretization of the steady state problem. Results are given for the CPU time and the number of iterations using a Richardson iteration method for the unpreconditioned and preconditioned cases.

  4. Quark flavor mixings from hierarchical mass matrices

    NASA Astrophysics Data System (ADS)

    Verma, Rohit; Zhou, Shun

    2016-05-01

    In this paper, we extend the Fritzsch ansatz of quark mass matrices while retaining their hierarchical structures and show that the main features of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V, including |V^{}_{us}| ˜eq |V^{}_{cd}|, |V^{}_{cb}| ˜eq |V^{}_{ts}| and |V^{}_{ub}|/|V^{}_{cb}| < |V^{}_{td}|/|V^{}_{ts}|, can be well understood. This agreement is observed especially when the mass matrices have non-vanishing (1, 3) and (3, 1) off-diagonal elements. The phenomenological consequences of these for the allowed texture content and gross structural features of `hierarchical' quark mass matrices are addressed from a model-independent prospective under the assumption of factorizable phases in these. The approximate and analytical expressions of the CKM matrix elements are derived and a detailed analysis reveals that such structures are in good agreement with the observed quark flavor mixing angles and the CP-violating phase at the 1σ level and call upon a further investigation of the realization of these structures from a top-down prospective.

  5. Continuum description of quasi-static intrusion of non-wetting liquid into a porous body

    NASA Astrophysics Data System (ADS)

    Cieszko, M.; Czapla, E.; Kempiński, M.

    2015-01-01

    This paper proposes a continuum description of the quasi-static processes of non-wetting liquid intrusion into a porous body. The description of such processes is important in the interpretation of mercury porosimetry data, which is commonly used to determine the pore space structure parameters of porous materials. A new macroscopic model of capillary transport of non-wetting liquid in porous material is proposed. It is assumed that a quasi-static process of liquid intrusion takes place in the pore space-pressure continuum and that liquid filling an undeformable porous material forms a macroscopic continuum constituted by a mobile and a capillary liquid which exchange mass and energy. The capillary liquid forms a thin layer on the surface of the liquid filling the porous material that is in contact with the internal surface of the pores. It is immoveable and contains the whole capillary energy. Mass balance equations for both constituents and constitutive relations describing capillary transport in the pore space-pressure continuum are formulated, and a boundary condition on the surface of the porous body is proposed. The equations obtained are solved for the special case of liquid intrusion into a ball of porous material. Analytical expressions are obtained for the saturation distribution of non-wetting liquid in the ball and for the capillary potential curve. Their dependence on parameters of the system is analyzed.

  6. Aerodynamic Synthesis of Biocompatible Matrices and their Functionalization by Nanoparticles Obtained by the Method of Laser Ablation

    NASA Astrophysics Data System (ADS)

    Bol'basov, E. N.; Lapin, I. N.; Tverdokhlebov, S. I.; Svetlichnyi, V. A.

    2014-07-01

    For applications in tissue engineering, three-dimensional biodegradable polymeric matrices, whose surface is functionalized by nanoparticles obtained in the liquid phase by the method of laser ablation from bulk metal (Ag or Zn) targets, are synthesized by the method of aerodynamic synthesis from a solution of poly-l-lactide acid. Their properties are investigated. It is demonstrated that the matrices represent a very porous spatial fibrous structure consisting of polymorphic fibers with diameters from 0.25 to 2.5 μm. It is established that functional coatings consisting of agglomerates of semiconductor (ZnO) or metal (Ag) nanoparticles can be produced on the surface of structural matrix elements by repeated matrix impregnation.

  7. Special paraunitary matrices, Cayley transform, and multidimensional orthogonal filter banks.

    PubMed

    Zhou, Jianping; Do, Minh N; Kovaĉević, Jelena

    2006-02-01

    We characterize and design multidimensional (MD) orthogonal filter banks using special paraunitary matrices and the Cayley transform. Orthogonal filter banks are represented by paraunitary matrices in the polyphase domain. We define special paraunitary matrices as paraunitary matrices with unit determinant. We show that every paraunitary matrix can be characterized by a special paraunitary matrix and a phase factor. Therefore, the design of paraunitary matrices (and thus of orthogonal filter banks) becomes the design of special paraunitary matrices, which requires a smaller set of nonlinear equations. Moreover, we provide a complete characterization of special paraunitary matrices in the Cayley domain, which converts nonlinear constraints into linear constraints. Our method greatly simplifies the design of MD orthogonal filter banks and leads to complete characterizations of such filter banks. PMID:16479821

  8. Porous electrode preparation method

    DOEpatents

    Arons, R.M.; Dusek, J.T.

    1983-10-18

    A porous sintered plaque is provided with a bimodal porosity that is especially well suited for use as an electrode within a molten carbonate fuel cell. The coarse porosity is sufficient for admitting gases into contact with the reaction surfaces while the fine porosity is wetted with and retains molten electrolyte on the reaction sites. The electrode structure is prepared by providing a very fine powder of such as nickel oxide and blending the powder with a suitable decomposable binder to form a solid mass. The mass is comminuted into agglomerate size particles substantially larger than the fine oxide particles and formed into a cohesive compact for subsequent sintering. Sintering is carried out at sufficient conditions to bind the agglomerates together into a porous structure having both coarse and fine porosity. Where lithiated nickel oxide cathodes are prepared, the sintering conditions can be moderate enough to retain substantial quantities of lithium within the electrode for adequate conductivity. 2 figs.

  9. Porous electrode preparation method

    DOEpatents

    Arons, Richard M.; Dusek, Joseph T.

    1983-01-01

    A porous sintered plaque is provided with a bimodal porosity that is especially well suited for use as an electrode within a molten carbonate fuel cell. The coarse porosity is sufficient for admitting gases into contact with the reaction surfaces while the fine porosity is wetted with and retains molten electrolyte on the reaction sites. The electrode structure is prepared by providing a very fine powder of such as nickel oxide and blending the powder with a suitable decomposable binder to form a solid mass. The mass is comminuted into agglomerate size particles substantially larger than the fine oxide particles and formed into a cohesive compact for subsequent sintering. Sintering is carried out at sufficient conditions to bind the agglomerates together into a porous structure having both coarse and fine porosity. Where lithiated nickel oxide cathodes are prepared, the sintering conditions can be moderate enough to retain substantial quantities of lithium within the electrode for adequate conductivity.

  10. Porous polymer media

    DOEpatents

    Shepodd, Timothy J.

    2002-01-01

    Highly crosslinked monolithic porous polymer materials for chromatographic applications. By using solvent compositions that provide not only for polymerization of acrylate monomers in such a fashion that a porous polymer network is formed prior to phase separation but also for exchanging the polymerization solvent for a running buffer using electroosmotic flow, the need for high pressure purging is eliminated. The polymer materials have been shown to be an effective capillary electrochromatographic separations medium at lower field strengths than conventional polymer media. Further, because of their highly crosslinked nature these polymer materials are structurally stable in a wide range of organic and aqueous solvents and over a pH range of 2-12.

  11. Strong, Lightweight, Porous Materials

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Meador, Mary Ann B.; Johnston, James C.; Fabrizio, Eve F.; Ilhan, Ulvi

    2007-01-01

    A new class of strong, lightweight, porous materials has been invented as an outgrowth of an effort to develop reinforced silica aerogels. The new material, called X-Aerogel is less hygroscopic, but no less porous and of similar density to the corresponding unmodified aerogels. However, the property that sets X-Aerogels apart is their mechanical strength, which can be as much as two and a half orders of magnitude stronger that the unmodified aerogels. X-Aerogels are envisioned to be useful for making extremely lightweight, thermally insulating, structural components, but they may also have applications as electrical insulators, components of laminates, catalyst supports, templates for electrode materials, fuel-cell components, and filter membranes.

  12. Deterministic matrices matching the compressed sensing phase transitions of Gaussian random matrices

    PubMed Central

    Monajemi, Hatef; Jafarpour, Sina; Gavish, Matan; Donoho, David L.; Ambikasaran, Sivaram; Bacallado, Sergio; Bharadia, Dinesh; Chen, Yuxin; Choi, Young; Chowdhury, Mainak; Chowdhury, Soham; Damle, Anil; Fithian, Will; Goetz, Georges; Grosenick, Logan; Gross, Sam; Hills, Gage; Hornstein, Michael; Lakkam, Milinda; Lee, Jason; Li, Jian; Liu, Linxi; Sing-Long, Carlos; Marx, Mike; Mittal, Akshay; Monajemi, Hatef; No, Albert; Omrani, Reza; Pekelis, Leonid; Qin, Junjie; Raines, Kevin; Ryu, Ernest; Saxe, Andrew; Shi, Dai; Siilats, Keith; Strauss, David; Tang, Gary; Wang, Chaojun; Zhou, Zoey; Zhu, Zhen

    2013-01-01

    In compressed sensing, one takes samples of an N-dimensional vector using an matrix A, obtaining undersampled measurements . For random matrices with independent standard Gaussian entries, it is known that, when is k-sparse, there is a precisely determined phase transition: for a certain region in the (,)-phase diagram, convex optimization typically finds the sparsest solution, whereas outside that region, it typically fails. It has been shown empirically that the same property—with the same phase transition location—holds for a wide range of non-Gaussian random matrix ensembles. We report extensive experiments showing that the Gaussian phase transition also describes numerous deterministic matrices, including Spikes and Sines, Spikes and Noiselets, Paley Frames, Delsarte-Goethals Frames, Chirp Sensing Matrices, and Grassmannian Frames. Namely, for each of these deterministic matrices in turn, for a typical k-sparse object, we observe that convex optimization is successful over a region of the phase diagram that coincides with the region known for Gaussian random matrices. Our experiments considered coefficients constrained to for four different sets , and the results establish our finding for each of the four associated phase transitions. PMID:23277588

  13. Reciprocating magnetic refrigerator employing tandem porous matrices within a reciprocating displacer

    NASA Technical Reports Server (NTRS)

    Johnson, D. L. (Inventor)

    1985-01-01

    Disclosed is a method and apparatus for a magnetic refrigeration system. A continuously reciprocating displacer houses at least a pair of paramagnetic substances each of which is alternately driven into and out of a magnetic field. Two separate bidirectional pumping systems flow helium gas through the displacer and through both paramagnetic substances to create heat exchange conditions at two separate temperature extremes.

  14. Osteoblast growth and function in porous poly epsilon -caprolactone matrices for bone repair: a preliminary study.

    PubMed

    Ciapetti, G; Ambrosio, L; Savarino, L; Granchi, D; Cenni, E; Baldini, N; Pagani, S; Guizzardi, S; Causa, F; Giunti, A

    2003-09-01

    Current methods for the replacement of skeletal tissue involve the use of autografts, allografts and, recently, synthetic substitutes, which provide a proper amount of material to repair large bone defects. Engineered bone seems a promising approach, but a number of variables have to be set prior to any clinical application. In this study, four different poly caprolactone-based polymers (PCL) were prepared and tested in vitro using osteoblast-like Saos-2 cells. Differences among three-dimensional polymers include porosity, addition of hydroxyapatite (HA) particles, and treatment with simulated body fluid. Biochemical parameters to assess cell/material interactions include viability, growth, alkaline phosphatase release, and mineralization of osteoblastic cells seeded onto three-dimensional samples, while their morphology was observed using light microscopy and SEM. Preliminary results show that the polymers, though degrading in the medium, have a positive interaction with cells, as they support cell growth and functions. In the short-term culture (3-7 days) of Saos-2 on polymers, little differences were found among PCL samples, with the presence of HA moderately improving the number of cells onto the surfaces. In the long term (3-4 weeks), it was found that the HA-added polymers obtained the best colonization by cells, and more mineral formation was observed after coating with SBF. It can be concluded that PCL is a promising material for three-dimensional scaffold for bone formation, and the presence of bone-like components improves osteoblast activity. PMID:12818554

  15. Modeling structure-function relationships for diffusive drug transport in inert porous geopolymer matrices.

    PubMed

    Jämstorp, Erik; Strømme, Maria; Frenning, Göran

    2011-10-01

    A unique structure-function relationship investigation of mechanically strong geopolymer drug delivery vehicles for sustained release of potent substances is presented. The effect of in-synthesis water content on geopolymer pore structure and diffusive drug transport is investigated. Scanning electron microscopy, N2 gas adsorption, mercury intrusion porosimetry, compression strength test, drug permeation, and release experiments are performed. Effective diffusion coefficients are measured and compared with corresponding theoretical values as derived from pore size distribution and connectivity via pore-network modeling. By solely varying the in-synthesis water content, mesoporous and mechanically strong geopolymers with porosities of 8%-45% are obtained. Effective diffusion coefficients of the model drugs Saccharin and Zolpidem are observed to span two orders of magnitude (∼1.6-120 × 10(-8) cm(2) /s), comparing very well to theoretical estimations. The ability to predict drug permeation and release from geopolymers, and materials alike, allows future formulations to be tailored on a structural and chemical level for specific applications such as controlled drug delivery of highly potent substances. PMID:21656516

  16. Speciation of nanoscale objects by nanoparticle imprinted matrices.

    PubMed

    Hitrik, Maria; Pisman, Yamit; Wittstock, Gunther; Mandler, Daniel

    2016-08-01

    The toxicity of nanoparticles is not only a function of the constituting material but depends largely on their size, shape and stabilizing shell. Hence, the speciation of nanoscale objects, namely, their detection and separation based on the different species, similarly to heavy metals, is of outmost importance. Here we demonstrate the speciation of gold nanoparticles (AuNPs) and their electrochemical detection using the concept of "nanoparticles imprinted matrices" (NAIM). Negatively charged AuNPs are adsorbed as templates on a conducting surface previously modified with polyethylenimine (PEI). The selective matrix is formed by the adsorption of either oleic acid (OA) or poly(acrylic acid) (PAA) on the non-occupied areas. The AuNPs are removed by electrooxidation to form complementary voids. These voids are able to recognize the AuNPs selectively based on their size. Furthermore, the selectivity could be improved by adsorbing an additional layer of 1-hexadecylamine, which deepened the voids. Interestingly, silver nanoparticles (AgNPs) were also recognized if their size matched those of the template AuNPs. The steps in assembling the NAIMs and the reuptake of the nanoparticles were characterized carefully. The prospects for the analytical use of NAIMs, which are simple, of small dimension, cost-efficient and portable, are in the sensing and separation of nanoobjects. PMID:26955908

  17. State Constitutionalism: Completing the Interdisciplinary Study of Constitutional Law and Political Theory.

    ERIC Educational Resources Information Center

    Williams, Robert F.

    1993-01-01

    Argues that a complete and accurate understanding of constitutional history and constitutional law requires the study of state constitutions. Maintains that state constitutions contain a coherent political theory that is, in important respects, at variance with the concept of federalism. (CFR)

  18. Constitutional and Non-Constitutional Governments...Similarities and Differences throughout History. Resource Packet.

    ERIC Educational Resources Information Center

    Pallasch, Brian Thomas

    This civic education resource packet is designed to provide teachers, community leaders, and other civic educators with an understanding of the differences between constitutional and non-constitutional governments. Six papers discussing the topic are included: "The Differences bewteen Constitutional and Non-Constitutional Governments" (John…

  19. 3 CFR 8418 - Proclamation 8418 of September 16, 2009. Constitution Day and Citizenship Day, Constitution Week...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 3 The President 1 2010-01-01 2010-01-01 false Proclamation 8418 of September 16, 2009. Constitution Day and Citizenship Day, Constitution Week, 2009 8418 Proclamation 8418 Presidential Documents Proclamations Proclamation 8418 of September 16, 2009 Proc. 8418 Constitution Day and Citizenship Day, Constitution Week, 2009By the President of...

  20. Natural convection in porous media

    SciTech Connect

    Prasad, V.; Hussain, N.A.

    1986-01-01

    This book presents the papers given at a conference on free convection in porous materials. Topics considered at the conference included heat transfer, nonlinear temperature profiles and magnetic fields, boundary conditions, concentrated heat sources in stratified porous media, free convective flow in a cavity, heat flux, laminar mixed convection flow, and the onset of convection in a porous medium with internal heat generation and downward flow.

  1. Porous microsphere and its applications

    PubMed Central

    Cai, Yunpeng; Chen, Yinghui; Hong, Xiaoyun; Liu, Zhenguo; Yuan, Weien

    2013-01-01

    Porous microspheres have drawn great attention in the last two decades for their potential applications in many fields, such as carriers for drugs, absorption and desorption of substances, pulmonary drug delivery, and tissue regeneration. The application of porous microspheres has become a feasible way to address existing problems. In this essay, we give a brief introduction of the porous microsphere, its characteristics, preparation methods, applications, and a brief summary of existing problems and research tendencies. PMID:23515359

  2. Selective formation of porous silicon

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W. (Inventor); Jones, Eric W. (Inventor)

    1993-01-01

    A pattern of porous silicon is produced in the surface of a silicon substrate by forming a pattern of crystal defects in said surface, preferably by applying an ion milling beam through openings in a photoresist layer to the surface, and then exposing said surface to a stain etchant, such as HF:HNO3:H2O. The defected crystal will preferentially etch to form a pattern of porous silicon. When the amorphous content of the porous silicon exceeds 70 percent, the porous silicon pattern emits visible light at room temperature.

  3. Selective formation of porous silicon

    NASA Technical Reports Server (NTRS)

    Fathauer, Jones (Inventor)

    1993-01-01

    A pattern of porous silicon is produced in the surface of a silicon substrate by forming a pattern of crystal defects in said surface, preferably by applying an ion milling beam through openings in a photoresist layer to the surface, and then exposing said surface to a stain etchant, such as HF:HNO3:H20. The defected crystal will preferentially etch to form a pattern of porous silicon. When the amorphous content of the porous silicon exceeds 70 percent, the porous silicon pattern emits visible light at room temperature.

  4. Blood-brain barrier properties in vitro depend on composition and assembly of endogenous extracellular matrices.

    PubMed

    Zobel, Kathrin; Hansen, Uwe; Galla, Hans-Joachim

    2016-08-01

    Brain capillary endothelial cells, which constitute the blood-brain barrier (BBB), are enveloped by the extracellular matrix (ECM) produced by endothelial cells, pericytes and astrocytes. The contribution of matrix components secreted by the various cell types at the neurovascular unit, however, remains unclear with respect to their effect on endothelial barrier function. In this study, a new in vitro model was established by growing endothelial cells on an ECM produced by pericytes, astrocytes or a serial combination of both. The last-mentioned was found to be more in vivo-like. We investigated the role of the composition and morphology of ECM supra-structures in maintaining BBB function. The composition was analysed by protein analysis (enzyme-linked immunosorbent assay) and the ultrastructure of generated matrices was analysed by transmission electron microscopy including immunogold labelling. We could show by electric cell-substrate impedance sensing measurements that pericytes and combined matrices significantly improved the barrier tightness of porcine brain capillary endothelial cells (PBCEC). The increase of the resistance was verified by enhanced expression of tight junction proteins. Thus, for the first time, we have shown that barrier integrity is strictly controlled by the ECM, which is a product of all cells involved in the secretion of ECM components and their modification by corresponding cells. Moreover, we have demonstrated that complex matrices by the various cells of the BBB induce barrier marker enzymes in PBCEC, such as alkaline phosphatase. PMID:27053246

  5. A new metric of analyzing the surface optical characteristic based on the measurement of Mueller matrices

    NASA Astrophysics Data System (ADS)

    Zhou, Xiao-jun; Wang, Xiu-qin; Gu, Guo-hua; Yang, Wei; Qian, Wei-xian

    2014-12-01

    In this paper, we propose to obtain the optical characteristics on material surface by Mueller calculus. In our research, a new metric for Mueller matrices, named R(M) , is defined to describe the polarization and depolarization characteristics on material surface by analyzing the constitute of Mueller matrices. The definition of R(M) is derived from the definition of the depolarization scalar metric for Mueller matrices named Q (M ) which can show the diattenuation and depolarization characteristics. With the advantage of Q (M ) , we assumed and proved the advantage of R(M) against the traditional metrics, the polarizance parameter P(M) and the depolarization index DI (M ) . This comparison can fully illustrate the value of R(M) . It is considered that P(M) and DI (M ) which cannot analyze the optical characteristics commonly to give a comprehensive evaluation. However, composed of P(M) and DI (M ) , R(M) can comprehensively reflect the optical signification which P(M) and DI (M ) represent. R(M) can be used to analyze different optical polarized characteristics on material surface with five bounds as totally depolarizing, partially depolarizing, totally polarizing, partially polarizing, nondepolarizing nonpolarizing. This means that R(M) can enable us to distinguish different materials by their different polarized characteristic on surface. With the definition of R(M) , it can be known that how the optical polarized characteristics work to change the polarized state of incident light on material surface.

  6. Quantum groups, braiding matrices and coset models

    SciTech Connect

    Itoyama, H.

    1989-07-01

    We discuss a few results on quantum groups in the context of rational conformal field theory with underlying affine Lie algebras. A vertex-height correspondence - a well-known procedure in solvable lattice models - is introduced in the WZW theory. This leads to a new definition of chiral vertex operator in which the zero mode is given by the q-Clebsch Gordan coefficients. Braiding matrices of coset models are found to factorize into those of the WZW theories. We briefly discuss the construction of the generators of the universal enveloping algebra in Toda field theories. 21 refs., 2 figs.

  7. Decontamination of matrices containing actinide oxides

    SciTech Connect

    Villarreal, Robert

    1997-12-01

    There is provided a method for removing actinides and actinide oxides, particularly fired actinides, from soil and other contaminated matrices, comprising: (a) contacting a contaminated material with a solution of at least one inhibited fluoride and an acid to form a mixture; (b) heating the mixture of contaminated material and solution to a temperature in the range from about 30 C to about 90 C while stirring; (c) separating the solution from any undissolved matrix material in the mixture; (d) washing the undissolved matrix material to remove any residual materials; and (e) drying and returning the treated matrix material to the environment.

  8. Defining the criteria for identifying constitutional epimutations.

    PubMed

    Sloane, Mathew A; Ward, Robyn L; Hesson, Luke B

    2016-01-01

    In the January 2016 issue of Clinical Epigenetics, Quiñonez-Silva et al. (Clin Epigenetics 8:1, 2016) described a possible constitutional epimutation of the RB1 gene as a cause of hereditary predisposition to retinoblastoma. The term constitutional epimutation describes an epigenetic aberration in normal tissues that predisposes to disease. The data presented by Quiñonez-Silva et al. are interesting, but further analysis is required to demonstrate a constitutional epimutation in this family. Here, we define the criteria and describe the experimental approach necessary to identify an epigenetic aberration as a constitutional epimutation. PMID:27096027

  9. Testing of constitutive models in LAME.

    SciTech Connect

    Hammerand, Daniel Carl; Scherzinger, William Mark

    2007-09-01

    Constitutive models for computational solid mechanics codes are in LAME--the Library of Advanced Materials for Engineering. These models describe complex material behavior and are used in our finite deformation solid mechanics codes. To ensure the correct implementation of these models, regression tests have been created for constitutive models in LAME. A selection of these tests is documented here. Constitutive models are an important part of any solid mechanics code. If an analysis code is meant to provide accurate results, the constitutive models that describe the material behavior need to be implemented correctly. Ensuring the correct implementation of constitutive models is the goal of a testing procedure that is used with the Library of Advanced Materials for Engineering (LAME) (see [1] and [2]). A test suite for constitutive models can serve three purposes. First, the test problems provide the constitutive model developer a means to test the model implementation. This is an activity that is always done by any responsible constitutive model developer. Retaining the test problem in a repository where the problem can be run periodically is an excellent means of ensuring that the model continues to behave correctly. A second purpose of a test suite for constitutive models is that it gives application code developers confidence that the constitutive models work correctly. This is extremely important since any analyst that uses an application code for an engineering analysis will associate a constitutive model in LAME with the application code, not LAME. Therefore, ensuring the correct implementation of constitutive models is essential for application code teams. A third purpose of a constitutive model test suite is that it provides analysts with example problems that they can look at to understand the behavior of a specific model. Since the choice of a constitutive model, and the properties that are used in that model, have an enormous effect on the results of an

  10. Characterization of porous hydroxyapatite.

    PubMed

    Hing, K A; Best, S M; Bonfield, W

    1999-03-01

    Hydroxyapatite has been considered for use in the repair of osseous defects for the last 20 years. Recent developments have led to interest in the potential of porous hydroxyapatite as a synthetic bone graft. However, despite considerable activity in this field, regarding assessment of the biological response to such materials, the basic materials characterization is often inadequate. This paper documents the characterization of the chemical composition, mechanical integrity, macro- and microstructure of a porous hydroxyapatite, Endobon (E. Merck GmbH), intended for the bone-graft market. Specimens possesed a range of apparent densities from 0.35 to 1.44 g cm(-3). Chemical analysis demonstrated that the natural apatite precursor of Endobon was not converted to pure hydroxyapatite, but retained many of the ionic substituents found in bone mineral, notably carbonate, sodium and magnesium ions. Investigation of the microstructure illustrated that the struts of the material were not fully dense, but had retained some traces of the network of osteocyte lacunae. Macrostructural analysis demonstrated the complex inter-relationship between the structural features of an open pore structure. Both pore size and connectivity were found to be inversely dependent on apparent density. Furthermore, measurement of pore aspect ratio and orientation demonstrated a relationship between apparent density and the degree of macrostructural anisotropy within the specimens, while, it was also noted that pore connectivity was sensitive to anisotropy. Compression testing demonstrated the effect of apparent density and macrostructural anisotropy on the mechanical properties. An increase in apparent density from 0.38 to 1.25 g cm(-3) resulted in increases in ultimate compressive stress and compressive modulus of 1 to 11 MPa and 0.2 to 3.1 GPa, respectively. Furthermore, anisotropic high density (> 0.9 g cm(-3)) specimens were found to possess lower compressive moduli than isotropic specimens

  11. The Approximation of Two-Mode Proximity Matrices by Sums of Order-Constrained Matrices.

    ERIC Educational Resources Information Center

    Hubert, Lawrence; Arabie, Phipps

    1995-01-01

    A least-squares strategy is proposed for representing a two-mode proximity matrix as an approximate sum of a small number of matrices that satisfy certain simple order constraints on their entries. The primary class of constraints considered defines Q-forms for particular conditions in a two-mode matrix. (SLD)

  12. Small, porous polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

    1976-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  13. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

    1976-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  14. Rigid porous filter

    DOEpatents

    Chiang, Ta-Kuan; Straub, Douglas L.; Dennis, Richard A.

    2000-01-01

    The present invention involves a porous rigid filter including a plurality of concentric filtration elements having internal flow passages and forming external flow passages there between. The present invention also involves a pressure vessel containing the filter for the removal of particulates from high pressure particulate containing gases, and further involves a method for using the filter to remove such particulates. The present filter has the advantage of requiring fewer filter elements due to the high surface area-to-volume ratio provided by the filter, requires a reduced pressure vessel size, and exhibits enhanced mechanical design properties, improved cleaning properties, configuration options, modularity and ease of fabrication.

  15. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

    1977-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree. C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  16. Compressed Sampling of Spectrally Sparse Signals Using Sparse Circulant Matrices

    NASA Astrophysics Data System (ADS)

    Xu, Guangjie; Wang, Huali; Sun, Lei; Zeng, Weijun; Wang, Qingguo

    2014-11-01

    Circulant measurement matrices constructed by partial cyclically shifts of one generating sequence, are easier to be implemented in hardware than widely used random measurement matrices; however, the diminishment of randomness makes it more sensitive to signal noise. Selecting a deterministic sequence with optimal periodic autocorrelation property (PACP) as generating sequence, would enhance the noise robustness of circulant measurement matrix, but this kind of deterministic circulant matrices only exists in the fixed periodic length. Actually, the selection of generating sequence doesn't affect the compressive performance of circulant measurement matrix but the subspace energy in spectrally sparse signals. Sparse circulant matrices, whose generating sequence is a sparse sequence, could keep the energy balance of subspaces and have similar noise robustness to deterministic circulant matrices. In addition, sparse circulant matrices have no restriction on length and are more suitable for the compressed sampling of spectrally sparse signals at arbitrary dimensionality.

  17. Median Approximations for Genomes Modeled as Matrices.

    PubMed

    Zanetti, Joao Paulo Pereira; Biller, Priscila; Meidanis, Joao

    2016-04-01

    The genome median problem is an important problem in phylogenetic reconstruction under rearrangement models. It can be stated as follows: Given three genomes, find a fourth that minimizes the sum of the pairwise rearrangement distances between it and the three input genomes. In this paper, we model genomes as matrices and study the matrix median problem using the rank distance. It is known that, for any metric distance, at least one of the corners is a [Formula: see text]-approximation of the median. Our results allow us to compute up to three additional matrix median candidates, all of them with approximation ratios at least as good as the best corner, when the input matrices come from genomes. We also show a class of instances where our candidates are optimal. From the application point of view, it is usually more interesting to locate medians farther from the corners, and therefore, these new candidates are potentially more useful. In addition to the approximation algorithm, we suggest a heuristic to get a genome from an arbitrary square matrix. This is useful to translate the results of our median approximation algorithm back to genomes, and it has good results in our tests. To assess the relevance of our approach in the biological context, we ran simulated evolution tests and compared our solutions to those of an exact DCJ median solver. The results show that our method is capable of producing very good candidates. PMID:27072561

  18. Cl2 deposition on soil matrices.

    PubMed

    Hearn, John; Eichler, Jeffery; Hare, Christopher; Henley, Michael

    2012-10-30

    Deposition of chlorine gas, Cl(2), on synthetic soil sample matrices was examined in a small chamber to ascertain its potential significance as a chemical sink during large-scale releases. The effects of organic matter, clay and sand mass fractions of the soil matrix, soil packing, and exposure to ultraviolet (UV) light on the observed Cl(2) deposition were examined. Organic matter content was found to be the dominant soil variable investigated that affected Cl(2) deposition; all other variables exhibited no measurable effect. Analytical results from the top 8.5mm of soil columns exposed to Cl(2) were fit to a simple kinetic model with six adjustable parameters. The kinetic model included two reactive bins to account for fast- and slow-reacting material in the soil matrices. The resulting empirical equation agreed with the data to within a factor of two and accurately predicted results from soil mixes not used to optimize the adjustable parameters. Total Cl(2) deposition, assuming a penetration depth of 8.5mm, was calculated to be as high as 160 metric tons per square kilometer for soil with an organic content of 10%, and inferred deposition velocities were as high as 0.5 cm/s for organically rich soil. PMID:22975257

  19. Semihumid gels as matrices for laser media

    NASA Astrophysics Data System (ADS)

    Larrue, Denis; Zarzycki, J.; Canva, Michael; Georges, Patrick M.; Brun, Alain

    1992-12-01

    Laser dyes were trapped in SiO2 xerogel host matrices to obtain a solid state dye laser. The evolution of the mechanical properties of two kinds of matrices, 'classic' and 'sono' gels, was followed during drying. A new impregnation process was performed on these xerogels: impregnation with a 'sono' sol. The influence of this treatment on certain physical and mechanical properties of the resulting impregnated gels was studied. The results indicate that impregnation substantially improves hardness, elastic modulus and fracture stress. The samples can then be easily polished to obtain optical quality surfaces and be used in a laser cavity. Moreover, optical properties related to laser emission of these materials such as efficiency, lifetime and longevity are better when the laser dye doped xerogels are impregnated. The organic dye molecule used was sulforhodamine 640, and results were obtained six months after their synthesis, with a pump beam working at a 5 Hz repetition rate with 450 (mu) J/pulse energy level. With the first pump shot on a fixed point of the samples, tunability from 600 to 650 nm, 60 (mu) J threshold, 2600 pump shots lifetime and a 10.5% slope efficiency were achieved using an impregnated 'sono' gel matrix.

  20. Hydrodynamical spectral evolution for random matrices

    NASA Astrophysics Data System (ADS)

    Forrester, Peter J.; Grela, Jacek

    2016-02-01

    The eigenvalues of the matrix structure X+{X}(0), where X is a random Gaussian Hermitian matrix and {X}(0) is non-random or random independent of X, are closely related to Dyson Brownian motion. Previous works have shown how an infinite hierarchy of equations satisfied by the dynamical correlations become triangular in the infinite density limit, and give rise to the complex Burgers equation for the Green’s function of the corresponding one-point density function. We show how this and analogous partial differential equations, for chiral, circular and Jacobi versions of Dyson Brownian motion follow from a macroscopic hydrodynamical description involving the current density and continuity equation. The method of characteristics gives a systematic approach to solving the PDEs, and in the chiral case we show how this efficiently reclaims the characterization of the global eigenvalue density for non-central Wishart matrices due to Dozier and Silverstein. Collective variables provide another approach to deriving the complex Burgers equation in the Gaussian case, and we show that this approach applies equally as well to chiral matrices. We relate both the Gaussian and chiral cases to the asymptotics of matrix integrals.

  1. Tensor Dictionary Learning for Positive Definite Matrices.

    PubMed

    Sivalingam, Ravishankar; Boley, Daniel; Morellas, Vassilios; Papanikolopoulos, Nikolaos

    2015-11-01

    Sparse models have proven to be extremely successful in image processing and computer vision. However, a majority of the effort has been focused on sparse representation of vectors and low-rank models for general matrices. The success of sparse modeling, along with popularity of region covariances, has inspired the development of sparse coding approaches for these positive definite descriptors. While in earlier work, the dictionary was formed from all, or a random subset of, the training signals, it is clearly advantageous to learn a concise dictionary from the entire training set. In this paper, we propose a novel approach for dictionary learning over positive definite matrices. The dictionary is learned by alternating minimization between sparse coding and dictionary update stages, and different atom update methods are described. A discriminative version of the dictionary learning approach is also proposed, which simultaneously learns dictionaries for different classes in classification or clustering. Experimental results demonstrate the advantage of learning dictionaries from data both from reconstruction and classification viewpoints. Finally, a software library is presented comprising C++ binaries for all the positive definite sparse coding and dictionary learning approaches presented here. PMID:26054070

  2. FIBROBLAST MECHANICS IN 3D COLLAGEN MATRICES

    PubMed Central

    Rhee, Sangmyung; Grinnell, Frederick

    2007-01-01

    Connective tissues provide mechanical support and frameworks for the other tissues of the body. Type 1 collagen is the major protein component of ordinary connective tissue, and fibroblasts are the cell type primarily responsible for its biosynthesis and remodeling. Research on fibroblasts interacting with collagen matrices explores all four quadrants of cell mechanics: pro-migratory vs. pro-contractile growth factor environments on one axis; high tension vs. low tension cell-matrix interactions on the other. The dendritic fibroblast – probably equivalent to the resting tissue fibroblast – can be observed only in the low tension quadrant and generally has not been appreciated from research on cells incubated with planar culture surfaces. Fibroblasts in the low tension quadrant require microtubules for formation of dendritic extensions, whereas fibroblasts in the high tension quadrant require microtubules for polarization but not for spreading. Ruffling of dendritic extensions rather than their overall protrusion or retraction provides the mechanism for remodeling of floating collagen matrices, and floating matrix remodeling likely reflects a model of tissue mechanical homeostasis. PMID:17825456

  3. Bromination of selected pharmaceuticals in water matrices.

    PubMed

    Benitez, F Javier; Acero, Juan L; Real, Francisco J; Roldan, Gloria; Casas, Francisco

    2011-11-01

    The bromination of five selected pharmaceuticals (metoprolol, naproxen, amoxicillin, phenacetin, and hydrochlorothiazide) was studied with these compounds individually dissolved in ultra-pure water. The apparent rate constants for the bromination reaction were determined as a function of the pH, obtaining the sequence amoxicillin>naproxen>hydrochlorothiazide≈phenacetin≈metoprolol. A kinetic mechanism specifying the dissociation reactions and the species formed for each compound according to its pK(a) value and the pH allowed the intrinsic rate constants to be determined for each elementary reaction. There was fairly good agreement between the experimental and calculated values of the apparent rate constants, confirming the goodness of the proposed reaction mechanism. In a second stage, the bromination of the selected pharmaceuticals simultaneously dissolved in three water matrices (a groundwater, a surface water from a public reservoir, and a secondary effluent from a WWTP) was investigated. The pharmaceutical elimination trend agreed with the previously determined rate constants. The influence of the main operating conditions (pH, initial bromine dose, and characteristics of the water matrix) on the degradation of the pharmaceuticals was established. An elimination concentration profile for each pharmaceutical in the water matrices was proposed based on the use of the previously evaluated apparent rate constants, and the theoretical results agreed satisfactorily with experiment. Finally, chlorination experiments performed in the presence of bromide showed that low bromide concentrations slightly accelerate the oxidation of the selected pharmaceuticals during chlorine disinfection. PMID:21906777

  4. Electron-transfer reactions in polymer matrices

    NASA Astrophysics Data System (ADS)

    Vannikov, Anatolii V.; Grishina, Antonina D.

    1989-12-01

    This paper discusses the dark reactions and photoreactions that occur with transfer of an electron from a donor to an acceptor in polymer matrices under electron tunnelling conditions and when forming change-transfer complexes. The main emphasis is on an analysis of the factors that determine the rate of electron transfer, which, in accordance with the advanced theory of electron transfer, are the magnitude of the exchange interaction, the free energy of the process, and the reorganisation energies of the medium and the reacting donor and acceptor molecules. The existing models for the movement of charge carriers between single-type transport sites are discussed. The limits of applicability of the different models have been determined. The reorganisation energy of a polymer matrix is shown to have a considerable effect on the rate of movement of charge carriers on introduced transport molecules. The effect of the dielectric properties and free volume of polymer matrices on the characteristics of electron phototransfer in donor-acceptor complexes is discussed. The bibliography includes 126 references.

  5. Disintegration of porous polyethylene prostheses.

    PubMed

    Kerr, A G; Riley, D N

    1999-06-01

    A Plastipore (porous polyethylene) Total Ossicular Replacement Prosthesis gave an excellent initial hearing result which was maintained for 14 years. Hearing then began to deteriorate and revision surgery showed disintegration of the prosthesis and a defect in the stapes footplate. Histological examination confirmed previous findings in porous polyethylene with multinucleated foreign body giant cells and breakdown of the material. PMID:10384839

  6. Racah matrices and hidden integrability in evolution of knots

    NASA Astrophysics Data System (ADS)

    Mironov, A.; Morozov, A.; Morozov, An.; Sleptsov, A.

    2016-09-01

    We construct a general procedure to extract the exclusive Racah matrices S and S bar from the inclusive 3-strand mixing matrices by the evolution method and apply it to the first simple representations R = [ 1 ], [2], [3] and [ 2 , 2 ]. The matrices S and S bar relate respectively the maps (R ⊗ R) ⊗ R bar ⟶ R with R ⊗ (R ⊗ R bar) ⟶ R and (R ⊗ R bar) ⊗ R ⟶ R with R ⊗ (R bar ⊗ R) ⟶ R. They are building blocks for the colored HOMFLY polynomials of arbitrary arborescent (double fat) knots. Remarkably, the calculation realizes an unexpected integrability property underlying the evolution matrices.

  7. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 7 2012-01-01 2012-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to implement... operated as a single farming unit as set forth in § 718.202; or (iii) Because of a change in...

  8. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 7 2014-01-01 2014-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to implement... operated as a single farming unit as set forth in § 718.202; or (iii) Because of a change in...

  9. Studying the Constitution: Capitalizing on Two Bicentennials.

    ERIC Educational Resources Information Center

    Turner, Mary Jane; and Others

    1987-01-01

    This report addresses the long-term educational responsibility of helping young people become more knowledgeable about the meaning and values of the U.S. Constitution in their personal and civic life. The Bicentennial of the U.S. Constitution and the upcoming Bicentennial of the U.S. Bill of Rights in 1991 present the opportunity to refocus…

  10. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 7 2013-01-01 2013-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture Regulations of the Department of Agriculture (Continued) FARM SERVICE AGENCY, DEPARTMENT OF AGRICULTURE FARM... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to...

  11. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture Regulations of the Department of Agriculture (Continued) FARM SERVICE AGENCY, DEPARTMENT OF AGRICULTURE FARM... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to...

  12. From Confederation to Constitution: 1781-1789.

    ERIC Educational Resources Information Center

    Urofsky, Melvin I.; Cox, Nancy

    Students should achieve a higher level of understanding and appreciation of the evolving nature of the U.S. Constitution and its relevance to contemporary societal issues by studying historical documents from the period of time between the Articles of Confederation and the Constitution. This document begins with a history of that period and of the…

  13. Contragate, Covert Action, and the Constitution.

    ERIC Educational Resources Information Center

    Ratner, Michael

    1987-01-01

    The "Iran-Contragate" hearings were indicative of serious constitutional crisis. Analyzes and disputes following three defenses used by President Reagan to justify his actions in affair: he did not know or approve; it was not a violation of law; and his authority over foreign affairs is given in war powers clause of the Constitution--Congress…

  14. The Five Great Ideas of Our Constitution.

    ERIC Educational Resources Information Center

    Starr, Isidore

    1987-01-01

    Identifies five great ideas of the U.S. Constitution as power, liberty, justice, equality, and property. The first of two installments, article focuses on how ideas of power and liberty are presented in the Constitution. It also discusses how people may exercise power through voting and public protest and liberty through their First Amendment…

  15. The United States and the Indian Constitution.

    ERIC Educational Resources Information Center

    Weil, Jonathan S.

    India, a huge land with the second largest population in the world, socially and economically poor, and culturally and linguistically diverse, became the largest democracy in the world on November 26, 1949 with the adoption of the Indian Constitution. The goals of that constitution are: (1) the achievement of national unity and stability; (2) the…

  16. Constitutional Provisions for Community Junior Colleges.

    ERIC Educational Resources Information Center

    McLeod, Marshall W.

    1983-01-01

    Examines the role of the federal and state constitutions in community college law. Discusses the lack of state constitutional law pertaining explicitly to these institutions and suggests a probable reason for this void. Gives examples of extant state laws and discusses implications for the community college field. (AYC)

  17. The Constitution in the Twentieth Century.

    ERIC Educational Resources Information Center

    Murphy, Paul L.

    1987-01-01

    Investigates the development of the United States Constitution in the twentieth century up to and including the Burger Court. Contends that interpreting the Constitution is an important issue of our times. Consequently argues that we should teach students about the development of this document. (RKM)

  18. An Internet Guide to Teaching the Constitution

    ERIC Educational Resources Information Center

    Risinger, C. Frederick

    2005-01-01

    In 2004, Congress passed and President Bush signed legislation designating every September 17 as Constitution Day and suggesting that all schools teach about the Constitution on that day. There are innumerable websites, countless lesson plans and a multitude of other teaching resources on the topic. Teachers were inundated with brochures,…

  19. Resources for Teaching about the Constitution.

    ERIC Educational Resources Information Center

    Cohen, Cheryl B.

    1987-01-01

    Describes eight resources for teaching about the United States Constitution available from ERIC. Described are instructional materials for junior and senior high school students on such topics as (1) the role of the U.S. Supreme Court, (2) freedom of the press, (3) the history of the United States Constitution, and (4) problems of the…

  20. Alternative CHCA-based matrices for the analysis of low molecular weight compounds by UV-MALDI-tandem mass spectrometry.

    PubMed

    Porta, Tiffany; Grivet, Chantal; Knochenmuss, Richard; Varesio, Emmanuel; Hopfgartner, Gérard

    2011-02-01

    Analysis of low molecular weight compounds (LMWC) in complex matrices by vacuum matrix-assisted laser desorption/ionization (MALDI) often suffers from matrix interferences, which can severely degrade limits of quantitation. It is, therefore, useful to have available a range of suitable matrices, which exhibit complementary regions of interference. Two newly synthesized α-cyanocinnamic acid derivatives are reported here; (E)-2-cyano-3-(naphthalen-2-yl)acrylic acid (NpCCA) and (2E)-3-(anthracen-9-yl)-2-cyanoprop-2enoic acid (AnCCA). Along with the commonly used α-cyano-4-hydroxycinnamic acid (CHCA), and the recently developed 4-chloro-α-cyanocinnamic acid (Cl-CCA) matrices, these constitute a chemically similar series of matrices covering a range of molecular weights, and with correspondingly differing ranges of spectral interference. Their performance was compared by measuring the signal-to-noise ratios (S/N) of 47 analytes, mostly pharmaceuticals, with the different matrices using the selected reaction monitoring (SRM) mode on a triple quadrupole instrument equipped with a vacuum MALDI source. AnCCA, NpCCA and Cl-CCA were found to offer better signal-to-noise ratios in SRM mode than CHCA, but Cl-CCA yielded the best results for 60% of the compounds tested. To better understand the relative performance of this matrix series, the proton affinities (PAs) were measured using the kinetic method. Their relative values were: AnCCA > CHCA > NpCCA > Cl-CCA. This ordering is consistent with the performance data. The synthesis of the new matrices is straightforward and they provide (1) tunability of matrix background interfering ions and (2) enhanced analyte response for certain classes of compounds. PMID:21259393

  1. Porous metallic bodies

    DOEpatents

    Landingham, Richard L.

    1985-01-01

    Porous metallic bodies having a substantially uniform pore size of less than about 200 microns and a density of less than about 25 percent theoretical, as well as the method for making them, are disclosed. Group IIA, IIIB, IVB, VB, and rare earth metal hydrides are heated in a confining container at a controlled rate to a temperature of about greater than the temperature at which the hydride decomposes. Hydrogen is removed from the container and the remaining metal is heated during a second stage to a temperature greater than the temperature at which it was previously heated but not greater than the temperature of 1/2 to 2/3 the temperature at which the metal melts at a controlled rate. The resulting porous metallic body produced has a density less than about 25 percent theoretical and a pore size of less than about 200 microns. The metallic particles of the present invention have high inner surface area and possess minimum resistance to gas flow.

  2. Spectroscopic studies of chemical reactions and dynamics in sol-gel matrices

    SciTech Connect

    Akbarian, F.; Dunn, B.; Fuqua, P.D.; McKiernan, J.; Simoni, E.; Zink, J.I.

    1994-12-31

    The synthesis of sol-gel glasses containing organic and organometallic molecular dopants has been well established as an approach for creating new optical materials. Some of these properties are dependent upon chemical reactions which occur in porous xerogel matrices during the sol-gel process or when encapsulated molecules are exposed to other molecules in solution. In this paper, the study of two different types of chemical reactions in the pores of xerogel matrices is reported. In one case copper phthalocyanine is used to characterize dimerization within the pores. The results show that dimer formation is most likely to occur towards the end of the drying stage as the dye concentration in the pores increases from solvent evaporation. A second example involves the use of a pump-probe technique to determine the rate of proton recombination inside the pores of silica monoliths. The behavior of sols and gels is similar to aqueous solution while recombination of protons in the xerogel seems to be affected by the walls of the pores.

  3. Constitutive modeling of inelastic anisotropic material response

    NASA Technical Reports Server (NTRS)

    Stouffer, D. C.

    1984-01-01

    A constitutive equation was developed to predict the inelastic thermomechanical response of single crystal turbine blades. These equations are essential for developing accurate finite element models of hot section components and contribute significantly to the understanding and prediction of crack initiation and propagation. The method used was limited to unified state variable constitutive equations. Two approaches to developing an anisotropic constitutive equation were reviewed. One approach was to apply the Stouffer-Bodner representation for deformation induced anisotropy to materials with an initial anisotropy such as single crystals. The second approach was to determine the global inelastic strain rate from the contribution of the slip in each of the possible crystallographic slip systems. A three dimensional finite element is being developed with a variable constitutive equation link that can be used for constitutive equation development and to predict the response of an experiment using the actual specimen geometry and loading conditions.

  4. Modeling added compressibility of porosity and the thermomechanical response of wet porous rock

    SciTech Connect

    Rubin, M.B.; Elata, D.; Attia, A.V.

    1995-06-01

    This paper concerned with modeling the response of a porous brittle solid whose pores may be dry or partially filled with fluid. A form for the Helmholtz free energy is proposed which incorporated known Mie-Grueneisen constitutive equations for the nonporous solid and for the fluid, and which uses an Eilnstein formulation with variable specific heat. In addition, a functional form for porosity is postulated which porous rock. Restrictions on constitutive assumptions for the composite of porous solid ad fluid are obtained which ensure thermodynamic consistency. Examples show that although the added compressibility of porosity is determined by fitting data for dry Mt. Helen Tuff, the predicted responses of saturated and partially saturated tuff agree well with experimental data.

  5. 3 CFR 8562 - Proclamation 8562 of September 16, 2010. Constitution Day and Citizenship Day, Constitution Week...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., Constitution Week, 2010By the President of the United States of America A Proclamation The summer of 1787 was a... charter on September 17, 1787. With their signatures, and subsequent ratification of the Constitution...

  6. Granulation and infiltration processes for the fabrication of minor actinide fuels, targets and conditioning matrices

    NASA Astrophysics Data System (ADS)

    Nästren, C.; Fernandez, A.; Haas, D.; Somers, J.; Walter, M.

    2007-05-01

    The impact of Pu and Am, two elements that potentially pose a long term hazard for the disposal of spent nuclear fuel, can be abated by their reintroduction into the fuel cycle for transmutation. Such transmutation targets can be fabricated by a sol gel method for the production of porous inactive beads, which are then infiltrated by Am solutions. Following calcination, compaction into pellets and sintering, the product is obtained. At its heart, the sol gel process relies on an ammonia precipitation, so that it is not universally applicable. Therefore, an alternative is sought not just to overcome this chemical limitation, but also to simplify the process and reduce waste streams. The new concept utilises powder metallurgy routes (compaction, crushing and sieving) to produce porous, almost, dust free granules, which are infiltrated with the actinide nitrate. The method has been developed using yttria stabilised zirconia and alumina, and has been demonstrated for the production of Al2O3-AmO2 targets for neutron capture investigations. The results are very promising and meet light water reactor fuel specifications. In addition, the process is ideally suited for the production of ceramic matrices for conditioning actinides for geological disposal.

  7. Asphaltene multilayer growth in porous medium probed by SANS

    NASA Astrophysics Data System (ADS)

    Gummel, J.; Corvis, Y.; Jestin, J.; M'hamdi, J.; Barré, L.

    2009-02-01

    Presence of suspended particles such as asphaltene in crude oils could significantly affect the production by means of deposition in porous media especially near the well bore. We investigate this phenomenon using the ability of Small Angle Neutron Scattering technique to probe directly the asphaltene adsorption process in a porous medium at the nanometer length scale under flow conditions. A device based on a quartz tube filled with SiC particles constitute the porous medium in which an asphaltene solution in a mixture of good (toluene)/bad (heptane) solvent is injected under controlled flow. The contrast matching technique enables to match the porous medium scattering contributions and to measure the signal of the deposit. Such a device can be used for curves surface measurements on a setup originally designed for bulk studies and permit thus the direct comparison with measurements on flat surfaces (neutron reflectivity) and indirect adsorption measurements (adsorption isotherm). We show here that asphaltene in good solvent leads to a monolayer whereas addition of bad solvent results in a multilayer growth which is consistent with the deposition behaviour described in the literature.

  8. Closing in on the constitution of consciousness

    PubMed Central

    Miller, Steven M.

    2014-01-01

    The science of consciousness is a nascent and thriving field of research that is founded on identifying the minimally sufficient neural correlates of consciousness. However, I have argued that it is the neural constitution of consciousness that science seeks to understand and that there are no evident strategies for distinguishing the correlates and constitution of (phenomenal) consciousness. Here I review this correlation/constitution distinction problem and challenge the existing foundations of consciousness science. I present the main analyses from a longer paper in press on this issue, focusing on recording, inhibition, stimulation, and combined inhibition/stimulation strategies, including proposal of the Jenga analogy to illustrate why identifying the minimally sufficient neural correlates of consciousness should not be considered the ultimate target of consciousness science. Thereafter I suggest that while combined inhibition and stimulation strategies might identify some constitutive neural activities—indeed minimally sufficient constitutive neural activities—such strategies fail to identify the whole neural constitution of consciousness and thus the correlation/constitution distinction problem is not fully solved. Various clarifications, potential objections and related scientific and philosophical issues are also discussed and I conclude by proposing new foundational claims for consciousness science. PMID:25452738

  9. Electrokinetic coupling in unsaturated porous media

    SciTech Connect

    Revil, A.; Linde, N.; Cerepi, A.; Jougnot, D.; Matthai, S.; Finsterle, S.

    2007-02-27

    We consider a charged porous material that is saturated bytwo fluid phases that are immiscible and continuous on the scale of arepresentative elementary volume. The wetting phase for the grains iswater and the nonwetting phase is assumed to be an electricallyinsulating viscous fluid. We use a volume-averaging approach to derivethe linear constitutive equations for the electrical current density aswell as the seepage velocities of the wetting and nonwetting phases onthe scale of a representative elementary volume. These macroscopicconstitutive equations are obtained by volume-averaging Ampere's lawtogether with the Nernst Planck equation and the Stokes equations. Thematerial properties entering the macroscopic constitutive equations areexplicitly described as functions of the saturation of the water phase,the electrical formation factor, and parameters that describe thecapillary pressure function, the relative permeability function, and thevariation of electrical conductivity with saturation. New equations arederived for the streaming potential and electro-osmosis couplingcoefficients. A primary drainage and imbibition experiment is simulatednumerically to demonstrate that the relative streaming potential couplingcoefficient depends not only on the water saturation, but also on thematerial properties of the sample, as well as the saturation history. Wealso compare the predicted streaming potential coupling coefficients withexperimental data from four dolomite core samples. Measurements on thesesamples include electrical conductivity, capillary pressure, thestreaming potential coupling coefficient at various level of saturation,and the permeability at saturation of the rock samples. We found verygood agreement between these experimental data and the modelpredictions.

  10. Photochromic reaction of spiropyran in polymer matrices

    NASA Astrophysics Data System (ADS)

    Tork, Amir; Boudreault, Francois; Roberge, Mathieu; Galstian, Tigran V.; Lessard, Roger A.; Ritcey, Anna-Marie R.

    2000-12-01

    The photo excitations of Spiropyran-doped polymer films were studied. Cellulose acetate (CA), commercial ploy(methyl methacrylate) (PMMA) and PMMA prepared by radical polymerisation of MMA, were used as host polymer matrices. The open form of SP presents a maximum of absorption cantered at about 600 nm upon UV irradiation. We have determined the photoreaction rate constants, kuv and k15, for the coloring and bleaching processes. Reversible holographic recording in SPIPMMA films was studied and photochemical fatigue resistance was evaluated upon repeated UVfVisible irradiation cycles. We found a loss of 42, 53 and 74% respectively in PMMA by gravity deposition, PMMA (by polymerisation of MMA) and cellulose acetate films.

  11. Carbon nanomaterials in silica aerogel matrices

    SciTech Connect

    Hamilton, Christopher E; Chavez, Manuel E; Duque, Juan G; Gupta, Gautam; Doorn, Stephen K; Dattelbaum, Andrew M; Obrey, Kimberly A D

    2010-01-01

    Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

  12. Investigation of degradation mechanisms in composite matrices

    NASA Technical Reports Server (NTRS)

    Giori, C.; Yamauchi, T.

    1982-01-01

    Degradation mechanisms were investigated for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiations in vacuum up to 960 equivalent sun hours and 10 to the ninth power rads respectively. Based on GC and combined GC/MS analysis of volatile by-products evolved during irradiation, several free radical mechanisms of composite degradation were identified. The radiation resistance of different matrices was compared in terms of G values and quantum yields for gas formation. All the composite materials evaluated show high electron radiation stability and relatively low ultraviolet stability as indicated by low G values and high quantum for gas formation. Mechanical property measurements of irradiated samples did not reveal significant changes, with the possible exception of UV exposed polysulfone laminates. Hydrogen and methane were identified as the main by-products of irradiation, along with unexpectedly high levels of CO and CO2.

  13. Association of scattering matrices in quantum networks

    SciTech Connect

    Almeida, F.A.G.; Macêdo, A.M.S.

    2013-06-15

    Algorithms based on operations that associate scattering matrices in series or in parallel (analogous to impedance association in a classical circuit) are developed here. We exemplify their application by calculating the total scattering matrix of several types of quantum networks, such as star graphs and a chain of chaotic quantum dots, obtaining results with good agreement with the literature. Through a computational-time analysis we compare the efficiency of two algorithms for the simulation of a chain of chaotic quantum dots based on series association operations of (i) two-by-two centers and (ii) three-by-three ones. Empirical results point out that the algorithm (ii) is more efficient than (i) for small number of open scattering channels. A direct counting of floating point operations justifies quantitatively the superiority of the algorithm (i) for large number of open scattering channels.

  14. An In-Depth Tutorial on Constitutive Equations for Elastic Anisotropic Materials

    NASA Technical Reports Server (NTRS)

    Nemeth, Michael P.

    2011-01-01

    An in-depth tutorial on the constitutive equations for elastic, anisotropic materials is presented. Basic concepts are introduced that are used to characterize materials, and notions about how anisotropic material deform are presented. Hooke s law and the Duhamel-Neuman law for isotropic materials are presented and discussed. Then, the most general form of Hooke s law for elastic anisotropic materials is presented and symmetry requirements are given. A similar presentation is also given for the generalized Duhamel-Neuman law for elastic, anisotropic materials that includes thermal effects. Transformation equations for stress and strains are presented and the most general form of the transformation equations for the constitutive matrices are given. Then, specialized transformation equations are presented for dextral rotations about the coordinate axes. Next, concepts of material symmetry are introduced and criteria for material symmetries are presented. Additionally, engineering constants of fully anisotropic, elastic materials are derived from first principles and the specialized to several cases of practical importance.

  15. Robust Generalized Low Rank Approximations of Matrices

    PubMed Central

    Shi, Jiarong; Yang, Wei; Zheng, Xiuyun

    2015-01-01

    In recent years, the intrinsic low rank structure of some datasets has been extensively exploited to reduce dimensionality, remove noise and complete the missing entries. As a well-known technique for dimensionality reduction and data compression, Generalized Low Rank Approximations of Matrices (GLRAM) claims its superiority on computation time and compression ratio over the SVD. However, GLRAM is very sensitive to sparse large noise or outliers and its robust version does not have been explored or solved yet. To address this problem, this paper proposes a robust method for GLRAM, named Robust GLRAM (RGLRAM). We first formulate RGLRAM as an l1-norm optimization problem which minimizes the l1-norm of the approximation errors. Secondly, we apply the technique of Augmented Lagrange Multipliers (ALM) to solve this l1-norm minimization problem and derive a corresponding iterative scheme. Then the weak convergence of the proposed algorithm is discussed under mild conditions. Next, we investigate a special case of RGLRAM and extend RGLRAM to a general tensor case. Finally, the extensive experiments on synthetic data show that it is possible for RGLRAM to exactly recover both the low rank and the sparse components while it may be difficult for previous state-of-the-art algorithms. We also discuss three issues on RGLRAM: the sensitivity to initialization, the generalization ability and the relationship between the running time and the size/number of matrices. Moreover, the experimental results on images of faces with large corruptions illustrate that RGLRAM obtains the best denoising and compression performance than other methods. PMID:26367116

  16. Dirac matrices for Chern-Simons gravity

    SciTech Connect

    Izaurieta, Fernando; Ramirez, Ricardo; Rodriguez, Eduardo

    2012-10-06

    A genuine gauge theory for the Poincare, de Sitter or anti-de Sitter algebras can be constructed in (2n- 1)-dimensional spacetime by means of the Chern-Simons form, yielding a gravitational theory that differs from General Relativity but shares many of its properties, such as second order field equations for the metric. The particular form of the Lagrangian is determined by a rank n, symmetric tensor invariant under the relevant algebra. In practice, the calculation of this invariant tensor can be reduced to the computation of the trace of the symmetrized product of n Dirac Gamma matrices {Gamma}{sub ab} in 2n-dimensional spacetime. While straightforward in principle, this calculation can become extremely cumbersome in practice. For large enough n, existing computer algebra packages take an inordinate long time to produce the answer or plainly fail having used up all available memory. In this talk we show that the general formula for the trace of the symmetrized product of 2n Gamma matrices {Gamma}{sub ab} can be written as a certain sum over the integer partitions s of n, with every term being multiplied by a numerical cofficient {alpha}{sub s}. We then give a general algorithm that computes the {alpha}-coefficients as the solution of a linear system of equations generated by evaluating the general formula for different sets of tensors B{sup ab} with random numerical entries. A recurrence relation between different coefficients is shown to hold and is used in a second, 'minimal' algorithm to greatly speed up the computations. Runtime of the minimal algorithm stays below 1 min on a typical desktop computer for up to n = 25, which easily covers all foreseeable applications of the trace formula.

  17. Racetrack micro-resonators based on ridge waveguides made of porous silica

    NASA Astrophysics Data System (ADS)

    Girault, P.; Lorrain, N.; Lemaitre, J.; Poffo, L.; Guendouz, M.; Hardy, I.; Gadonna, M.; Gutierrez, A.; Bodiou, L.; Charrier, J.

    2015-12-01

    The fabrication of micro-resonators, made from porous silica ridge waveguides by using an electrochemical etching method of silicon substrate followed by thermal oxidation and then by a standard photolithography process, is reported. The design and fabrication process are described including a study of waveguide dimensions that provide single mode propagation and calculation of the coupling ratio between a straight access waveguide and the racetrack resonator. Scanning electronic microscopy observations and optical characterizations clearly show that the micro-resonator based on porous silica ridge waveguides has been well implemented. This porous micro-resonator is destined to be used as an optical sensor. The porous nature of the ridge waveguide constitutes the detection medium which will enhance the sensor sensitivity compared to usual micro-resonators based on the evanescent wave detection. A theoretical sensitivity of 1170 nm per refractive index unit has been calculated, taking into consideration experimental data obtained from the optical characterizations.

  18. Combustion in porous media

    SciTech Connect

    Dillon, J.

    1999-09-01

    A 2.8-liter tube-shaped combustion vessel was constructed to study flame propagation and quenching in porous media. For this experiment, hydrogen-air flames propagating horizontally into abed of 6 mm diameter glass beads were studied. Measurements of pressure and temperature along the length of the tube were used to observe flame propagation of quenching. The critical hydrogen concentration for Hz-air mixtures was found to be 11.5%, corresponding to a critical Peclet number of Pe* = 37. This value is substantially less than the value of Pe* = 65 quoted in the literature, for example Babkin et al. (1991). It is hypothesized that buoyancy and a dependence of Pe on the Lewis number account for the discrepancy between these two results.

  19. ABCD matrices as similarity transformations of Wigner matrices and periodic systems in optics.

    PubMed

    Başkal, S; Kim, Y S

    2009-09-01

    It is shown that every ray transfer matrix, often called the ABCD matrix, can be written as a similarity transformation of one of the Wigner matrices that dictate the internal space-time symmetries of relativistic particles, while the transformation matrix is a rotation preceded by a squeeze. The implementation of this mathematical procedure is described, and how it facilitates the calculations for scattering processes in periodic systems is explained. Multilayer optics and resonators such as laser cavities are discussed in detail. For both cases, the one-cycle transfer matrix is written as a similarity transformation of one of the Wigner matrices, rendering the computation of the ABCD matrix for an arbitrary number of cycles tractable. PMID:19721691

  20. Biogenic Cracks in Porous Rock

    NASA Astrophysics Data System (ADS)

    Hemmerle, A.; Hartung, J.; Hallatschek, O.; Goehring, L.; Herminghaus, S.

    2014-12-01

    Microorganisms growing on and inside porous rock may fracture it by various processes. Some of the mechanisms of biofouling and bioweathering are today identified and partially understood but most emphasis is on chemical weathering, while mechanical contributions have been neglected. However, as demonstrated by the perseverance of a seed germinating and cracking up a concrete block, the turgor pressure of living organisms can be very significant. Here, we present results of a systematic study of the effects of the mechanical forces of growing microbial populations on the weathering of porous media. We designed a model porous medium made of glass beads held together by polydimethylsiloxane (PDMS), a curable polymer. The rheological properties of the porous medium, whose shape and size are tunable, can be controlled by the ratio of crosslinker to base used in the PDMS (see Fig. 1). Glass and PDMS being inert to most chemicals, we are able to focus on the mechanical processes of biodeterioration, excluding any chemical weathering. Inspired by recent measurements of the high pressure (~0.5 Mpa) exerted by a growing population of yeasts trapped in a microfluidic device, we show that yeast cells can be cultured homogeneously within porous medium until saturation of the porous space. We investigate then the effects of such an inner pressure on the mechanical properties of the sample. Using the same model system, we study also the complex interplay between biofilms and porous media. We focus in particular on the effects of pore size on the penetration of the biofilm within the porous sample, and on the resulting deformations of the matrix, opening new perspectives into the understanding of life in complex geometry. Figure 1. Left : cell culture growing in a model porous medium. The white spheres represent the grains, bonds are displayed in grey, and microbes in green. Right: microscopy picture of glass beads linked by PDMS bridges, scale bar: 100 μm.

  1. The Modern Origin of Matrices and Their Applications

    ERIC Educational Resources Information Center

    Debnath, L.

    2014-01-01

    This paper deals with the modern development of matrices, linear transformations, quadratic forms and their applications to geometry and mechanics, eigenvalues, eigenvectors and characteristic equations with applications. Included are the representations of real and complex numbers, and quaternions by matrices, and isomorphism in order to show…

  2. Some Interesting Characteristics of Markov Chain Transition Matrices.

    ERIC Educational Resources Information Center

    Egelston, Richard L.

    A Monte Carlo investigation of Markov chain matrices was conducted to create empirical distributions for two statistics created from the transition matrices. Curve fitting techniques developed by Karl Pearson were used to deduce if theoretical equations could be fit to the two sets of distributions. The set of distributions which describe the…

  3. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Master records and metal matrices. 10.90 Section 10.90 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. General Provisions Master Records, and Metal Matrices § 10.90...

  4. Introduction to the QIAT Self-Evaluation Matrices

    ERIC Educational Resources Information Center

    Zabala, Joy Smiley; Carl, Diana F.

    2004-01-01

    The QIAT Self-Evaluation Matrices (QILT, 2001) were developed in response to formative evaluation data indicating a need for a model that could assist in the application of the Quality Indicators for Assistive Technology Services in Schools (Zabala, et al, 2000). The QIAT Matrices are based on the idea that change does not happen immediately, but…

  5. Component Identification and Item Difficulty of Raven's Matrices Items.

    ERIC Educational Resources Information Center

    Green, Kathy E.; Kluever, Raymond C.

    Item components that might contribute to the difficulty of items on the Raven Colored Progressive Matrices (CPM) and the Standard Progressive Matrices (SPM) were studied. Subjects providing responses to CPM items were 269 children aged 2 years 9 months to 11 years 8 months, most of whom were referred for testing as potentially gifted. A second…

  6. Efficient quantum circuits for Toeplitz and Hankel matrices

    NASA Astrophysics Data System (ADS)

    Mahasinghe, A.; Wang, J. B.

    2016-07-01

    Toeplitz and Hankel matrices have been a subject of intense interest in a wide range of science and engineering related applications. In this paper, we show that quantum circuits can efficiently implement sparse or Fourier-sparse Toeplitz and Hankel matrices. This provides an essential ingredient for solving many physical problems with Toeplitz or Hankel symmetry in the quantum setting with deterministic queries.

  7. A Real Quaternion Spherical Ensemble of Random Matrices

    NASA Astrophysics Data System (ADS)

    Mays, Anthony

    2013-10-01

    One can identify a tripartite classification of random matrix ensembles into geometrical universality classes corresponding to the plane, the sphere and the anti-sphere. The plane is identified with Ginibre-type (iid) matrices and the anti-sphere with truncations of unitary matrices. This paper focusses on an ensemble corresponding to the sphere: matrices of the form Y= A -1 B, where A and B are independent N× N matrices with iid standard Gaussian real quaternion entries. By applying techniques similar to those used for the analogous complex and real spherical ensembles, the eigenvalue joint probability density function and correlation functions are calculated. This completes the exploration of spherical matrices using the traditional Dyson indices β=1,2,4. We find that the eigenvalue density (after stereographic projection onto the sphere) has a depletion of eigenvalues along a ring corresponding to the real axis, with reflective symmetry about this ring. However, in the limit of large matrix dimension, this eigenvalue density approaches that of the corresponding complex ensemble, a density which is uniform on the sphere. This result is in keeping with the spherical law (analogous to the circular law for iid matrices), which states that for matrices having the spherical structure Y= A -1 B, where A and B are independent, iid matrices the (stereographically projected) eigenvalue density tends to uniformity on the sphere.

  8. A coupled problem of finite deformation and flow in porous media

    NASA Astrophysics Data System (ADS)

    Moussa, A. B.

    1980-06-01

    A theory for deformation and two phase flow in porous media was developed. Equations of balance of mass, momentum, moment of momentum and energy for each constituent were postulated. These led to equivalent balance equations for the mixture as a whole to which an entropy production inequality was also postulated. The formulation was then applied to the silage material. A constitutive theory was developed for the mixture. General appropriate constitutive assumptions were suggested and made to satisfy the axiom of material objectivity and entropy production inequality. Material incompressibility was defined and introduced into the general form of constitutive relations.

  9. Influence of wettability on constitutive relations and its role in upscaling

    SciTech Connect

    Soll, W.E.; Gray, W.G.; Tompson, A.F.B.

    1998-07-01

    The lattice Boltzmann (LB) method is applied to simulating multifluid flow in porous media at sub-pore resolution to determine constitutive behaviors. The authors address the importance of the LB technique for identifying process based constitutive relationships, and demonstrate its application through analysis of the influence of wettability on interfacial areas and constitutive relationships. Porous media surface wettability is varied from uniformly strongly wetted by the resident fluid through strongly wetted by the displacing fluid. Spatially variable wettability is also demonstrated. Primary imbibition and drainage displacements are run, and interfacial areas (IFA) as a function of time are determined and compared. Results indicate that wettability is an important factor in displacement behavior and resulting interfacial area. Primary imbibition in a strongly wet material under capillary dominated flows produces film flow, resulting in high IFAs that decrease with increasing saturation and viscous forces. Primary drainage produces initially high IFA that decreases slightly with increasing saturation or pressure drop. Surfaces with spatially variable wetting can have a strong influence on resulting fluid distributions and fluid flow.

  10. Regeneratively Cooled Porous Media Jacket

    NASA Technical Reports Server (NTRS)

    Mungas, Greg (Inventor); Fisher, David J. (Inventor); London, Adam Pollok (Inventor); Fryer, Jack Merrill (Inventor)

    2013-01-01

    The fluid and heat transfer theory for regenerative cooling of a rocket combustion chamber with a porous media coolant jacket is presented. This model is used to design a regeneratively cooled rocket or other high temperature engine cooling jacket. Cooling jackets comprising impermeable inner and outer walls, and porous media channels are disclosed. Also disclosed are porous media coolant jackets with additional structures designed to transfer heat directly from the inner wall to the outer wall, and structures designed to direct movement of the coolant fluid from the inner wall to the outer wall. Methods of making such jackets are also disclosed.

  11. Light emission from porous silicon

    NASA Astrophysics Data System (ADS)

    Penczek, John

    The continuous evolution of silicon microelectronics has produced significant gains in electronic information processing. However, greater improvements in performance are expected by utilizing optoelectronic techniques. But these techniques have been severely limited in silicon- based optoelectronics due to the lack of an efficient silicon light emitter. The recent observation of efficient light emission from porous silicon offer a promising opportunity to develop a suitable silicon light source that is compatible with silicon microelectronics. This dissertation examined the porous silicon emission mechanism via photoluminescence, and by a novel device structure for porous silicon emitters. The investigation first examined the correlation between porous silicon formation conditions (and subsequent morphology) with the resulting photoluminescence properties. The quantum confinement theory for porous silicon light emission contends that the morphology changes induced by the different formation conditions determine the optical properties of porous silicon. The photoluminescence spectral shifts measured in this study, in conjunction with TEM analysis and published morphological data, lend support to this theory. However, the photoluminescence spectral broadening was attributed to electronic wavefunction coupling between adjacent silicon nanocrystals. An novel device structure was also investigated in an effort to improve current injection into the porous silicon layer. The selective etching properties of porous silicon were used to create a p-i-n structure with crystalline silicon contacts to the porous silicon layer. The resulting device was found to have unique characteristics, with a negative differential resistance region and current-induced emission that spanned from 400 nm to 5500 nm. The negative differential resistance was correlated to resistive heating effects in the device. A numerical analysis of thermal emission spectra from silicon films, in addition to

  12. Time series, correlation matrices and random matrix models

    SciTech Connect

    Vinayak; Seligman, Thomas H.

    2014-01-08

    In this set of five lectures the authors have presented techniques to analyze open classical and quantum systems using correlation matrices. For diverse reasons we shall see that random matrices play an important role to describe a null hypothesis or a minimum information hypothesis for the description of a quantum system or subsystem. In the former case various forms of correlation matrices of time series associated with the classical observables of some system. The fact that such series are necessarily finite, inevitably introduces noise and this finite time influence lead to a random or stochastic component in these time series. By consequence random correlation matrices have a random component, and corresponding ensembles are used. In the latter we use random matrices to describe high temperature environment or uncontrolled perturbations, ensembles of differing chaotic systems etc. The common theme of the lectures is thus the importance of random matrix theory in a wide range of fields in and around physics.

  13. Almost Commuting Unitary Matrices Related to Time Reversal

    NASA Astrophysics Data System (ADS)

    Loring, Terry A.; Sørensen, Adam P. W.

    2013-11-01

    The behavior of fermionic systems depends on the geometry of the system and the symmetry class of the Hamiltonian and observables. Almost commuting matrices arise from band-projected position observables in such systems. One expects the mathematical behavior of almost commuting Hermitian matrices to depend on two factors. One factor will be the approximate polynomial relations satisfied by the matrices. The other factor is what algebra the matrices are in, either for , or , the algebra of quaternions. There are potential obstructions keeping k-tuples of almost commuting operators from being close to a commuting k-tuple.We consider two-dimensional geometries and so this obstruction lives in . This obstruction corresponds to either the Chern number or spin Chern number in physics. We show that if this obstruction is the trivial element in K-theory then the approximation by commuting matrices is possible.

  14. Proton conduction in crystalline and porous covalent organic frameworks.

    PubMed

    Xu, Hong; Tao, Shanshan; Jiang, Donglin

    2016-07-01

    Progress over the past decades in proton-conducting materials has generated a variety of polyelectrolytes and microporous polymers. However, most studies are still based on a preconception that large pores eventually cause simply flow of proton carriers rather than efficient conduction of proton ions, which precludes the exploration of large-pore polymers for proton transport. Here, we demonstrate proton conduction across mesoporous channels in a crystalline covalent organic framework. The frameworks are designed to constitute hexagonally aligned, dense, mesoporous channels that allow for loading of N-heterocyclic proton carriers. The frameworks achieve proton conductivities that are 2-4 orders of magnitude higher than those of microporous and non-porous polymers. Temperature-dependent and isotopic experiments revealed that the proton transport in these channels is controlled by a low-energy-barrier hopping mechanism. Our results reveal a platform based on porous covalent organic frameworks for proton conduction. PMID:27043780

  15. The Constitution and the Black Experiences

    ERIC Educational Resources Information Center

    Miles, E. W.

    1973-01-01

    A review of the constitutional promises to black people, early congressional efforts to fulfill these promises, early court cases construing the Fourteenth Amendment and the impact of these decisions along with their subsequent overruling. (Author/JB)

  16. Capturing the Essence of the Constitution.

    ERIC Educational Resources Information Center

    McMorrow, Catherine

    1987-01-01

    Offers three sample lesson plans for elementary grades designed to demonstrate the religious values inherent in the United States Constitution. Each lesson plan focuses on one amendment and includes a discussion of class activities. (DMM)

  17. Fabrication and characterization of porous silicon nanowires

    NASA Astrophysics Data System (ADS)

    Jung, Daeyoon; Cho, Soo Gyeong; Moon, Taeho; Sohn, Honglae

    2016-01-01

    We report the synthesis of porous silicon nanowires through the metalassisted chemical etching of porous silicon in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of porous silicon nanowires was characterized by scanning electron microscopy and transmission electron microscopy. The etch rate of the porous silicon nanowires was faster than that of silicon nanowires, but slower than that of porous silicon. The porous silicon nanowires distributed uniformly on the entire porous silicon layer and the tips of the porous silicon nanowires congregated together. The single crystalline and sponge-like porous structure with the pore diameters of less than 5 nm was confirmed for the porous silicon nanowires. [Figure not available: see fulltext.

  18. Synthesis and properties of porous SiC ceramics

    NASA Astrophysics Data System (ADS)

    Kiselov, V. S.; Lytvyn, P. M.; Yukhymchuk, V. O.; Belyaev, A. E.; Vitusevich, S. A.

    2010-05-01

    Porous silicon carbide (SiC) ceramics are produced using carbon matrices derived from natural wood. Such material is especially promising as it is environmentally friendly with attractive physical properties, including a high level of biocompatibility, chemical inertness, and mechanical strength. We have developed a forced impregnation process with further synthesis of SiC using natural wood as well as a variety of industrial carbon materials and compared the properties of these ceramics. The structure and composition of the materials obtained were investigated by Raman scattering spectroscopy. The hardness of the samples was estimated using the Vickers technique. It was shown that the phase composition and mechanical properties of synthesized SiC ceramics can be effectively controlled by the initial Si contents and temperature of the synthesis process. A large variety of options are demonstrated for materials development taking into account an optimal porosity selection for various practical applications.

  19. Environmental behavior of engineered nanomaterials in porous media: a review.

    PubMed

    Park, Chang Min; Chu, Kyoung Hoon; Heo, Jiyong; Her, Namguk; Jang, Min; Son, Ahjeong; Yoon, Yeomin

    2016-05-15

    A pronounced increase in the use of nanotechnology has resulted in nanomaterials being released into the environment. Environmental exposure to the most common engineered nanomaterials (ENMs), such as carbon-based and metal-based nanomaterials, can occur directly via intentional injection for remediation purposes, release during the use of nanomaterial-containing consumer goods, or indirectly via different routes. Recent reviews have outlined potential risks assessments, toxicity, and life cycle analyses regarding ENM emission. In this review, inevitable release of ENMs and their environmental behaviors in aqueous porous media are discussed with an emphasis on influencing factors, including the physicochemical properties of ENMs, solution chemistry, soil hydraulic properties, and soil matrices. Major findings of laboratory column studies and numerical approaches for the transport of ENMs are addressed, and studies on the interaction between ENMs and heavy metal ions in aqueous soil environments are examined. Future research is also presented with specific research directions and outlooks. PMID:26882524

  20. Rate constitutive theories for ordered thermofluids

    NASA Astrophysics Data System (ADS)

    Surana, K. S.; Nunez, D.; Reddy, J. N.; Romkes, A.

    2013-09-01

    The paper considers developments of constitutive theories in Eulerian description for compressible as well as incompressible ordered homogeneous and isotropic thermofluids in which the deviatoric Cauchy stress tensor and the heat vector are functions of density, temperature, temperature gradient, and the convected time derivatives of the strain tensors of up to a desired order. The fluids described by these constitutive theories are called ordered thermofluids due to the fact that the constitutive theories for the deviatoric Cauchy stress tensor and heat vector are dependent on the convected time derivatives of the strain tensor up to a desired order, the highest order of the convected time derivative of the strain tensor in the argument tensors defines the `order of the fluid'. The admissibility requirement necessitates that the constitutive theories for the stress tensor and heat vector satisfy conservation laws, hence, in addition to conservation of mass, balance of momenta, and conservation of energy, the second law of thermodynamics, that is, Clausius-Duhem inequality must also be satisfied by the constitutive theories or be used in their derivations. If we decompose the total Cauchy stress tensor into equilibrium and deviatoric components, then Clausius-Duhem inequality and Helmholtz free energy density can be used to determine the equilibrium stress in terms of thermodynamic pressure for compressible fluids and in terms of mechanical pressure for incompressible fluids, but the second law of thermodynamics provides no mechanism for deriving the constitutive theories for the deviatoric Cauchy stress tensor. In the development of the constitutive theories in Eulerian description, the covariant and contravariant convected coordinate systems, and Jaumann measures are natural choices. Furthermore, the mathematical models for fluids require Eulerian description in which material point displacements are not measurable. This precludes the use of displacement

  1. Porous substrates filled with nanomaterials

    DOEpatents

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael

    2014-08-19

    A composition comprising: at least one porous carbon monolith, such as a carbon aerogel, comprising internal pores, and at least one nanomaterial, such as carbon nanotubes, disposed uniformly throughout the internal pores. The nanomaterial can be disposed in the middle of the monolith. In addition, a method for making a monolithic solid with both high surface area and good bulk electrical conductivity is provided. A porous substrate having a thickness of 100 microns or more and comprising macropores throughout its thickness is prepared. At least one catalyst is deposited inside the porous substrate. Subsequently, chemical vapor deposition is used to uniformly deposit a nanomaterial in the macropores throughout the thickness of the porous substrate. Applications include electrical energy storage, such as batteries and capacitors, and hydrogen storage.

  2. Laser-induced growth of nanocrystals embedded in porous materials

    NASA Astrophysics Data System (ADS)

    Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed

    2013-06-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  3. Laser-induced growth of nanocrystals embedded in porous materials

    PubMed Central

    2013-01-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  4. Porous light-emitting compositions

    DOEpatents

    Burrell, Anthony K.; McCleskey, Thomas Mark; Jia, Quanxi; Bauer, Eve; Mueller, Alexander H.

    2012-04-17

    Light-emitting devices are prepared by coating a porous substrate using a polymer-assisted deposition process. Solutions of metal precursor and soluble polymers having binding properties for metal precursor were coated onto porous substrates. The coated substrates were heated at high temperatures under a suitable atmosphere. The result was a substrate with a conformal coating that did not substantially block the pores of the substrate.

  5. Additively manufactured porous tantalum implants.

    PubMed

    Wauthle, Ruben; van der Stok, Johan; Amin Yavari, Saber; Van Humbeeck, Jan; Kruth, Jean-Pierre; Zadpoor, Amir Abbas; Weinans, Harrie; Mulier, Michiel; Schrooten, Jan

    2015-03-01

    The medical device industry's interest in open porous, metallic biomaterials has increased in response to additive manufacturing techniques enabling the production of complex shapes that cannot be produced with conventional techniques. Tantalum is an important metal for medical devices because of its good biocompatibility. In this study selective laser melting technology was used for the first time to manufacture highly porous pure tantalum implants with fully interconnected open pores. The architecture of the porous structure in combination with the material properties of tantalum result in mechanical properties close to those of human bone and allow for bone ingrowth. The bone regeneration performance of the porous tantalum was evaluated in vivo using an orthotopic load-bearing bone defect model in the rat femur. After 12 weeks, substantial bone ingrowth, good quality of the regenerated bone and a strong, functional implant-bone interface connection were observed. Compared to identical porous Ti-6Al-4V structures, laser-melted tantalum shows excellent osteoconductive properties, has a higher normalized fatigue strength and allows for more plastic deformation due to its high ductility. It is therefore concluded that this is a first step towards a new generation of open porous tantalum implants manufactured using selective laser melting. PMID:25500631

  6. Mechanically implementable accommodation matrices for passive force control

    SciTech Connect

    Goswami, A.; Peshkin, M.

    1999-08-01

    Robot force control implemented by means of passive mechanical devices has inherent advantages over active implementations with regard to stability, response rapidity, and physical robustness. The class of devices considered in this paper consists of a Stewart platform-type mechanism interconnected with a network of adjustable mechanical elements such as springs and dampers. The control law repertoire of such a device, imagined as a robot wrist, is given by the range of admittance matrices that it may be programmed to possess. This paper focuses on wrists incorporating damper networks for which the admittance matrices reduce to accommodation or inverse-damping matrices. The authors show that a hydraulic network of fully adjustable damper elements may attain any diagonally dominant accommodation matrix. They describe the technique of selecting the individual damping coefficients to design a desired matrix. They identify the set of dominant matrices as a polyhedral convex cone in the space of matrix entries, and show that each dominant matrix can be composed of a positive linear combination of a fixed set of basis matrices. The overall wrist-accommodation matrix is obtained by projecting the accommodation matrix of the damper network through the wrist kinematics. The linear combination of the dominant basis matrices projected through the wrist kinematics generates the entire space of mechanically implementable force-control laws. The authors quantify the versatility of mechanically implementable force-control laws by comparing this space to the space of all matrices.

  7. Diffusion model to describe osteogenesis within a porous titanium scaffold.

    PubMed

    Schmitt, M; Allena, R; Schouman, T; Frasca, S; Collombet, J M; Holy, X; Rouch, P

    2016-01-01

    In this study, we develop a two-dimensional finite element model, which is derived from an animal experiment and allows simulating osteogenesis within a porous titanium scaffold implanted in ewe's hemi-mandible during 12 weeks. The cell activity is described through diffusion equations and regulated by the stress state of the structure. We compare our model to (i) histological observations and (ii) experimental data obtained from a mechanical test done on sacrificed animal. We show that our mechano-biological approach provides consistent numerical results and constitutes a useful tool to predict osteogenesis pattern. PMID:25573031

  8. A POROUS, LAYERED HELIOPAUSE

    SciTech Connect

    Swisdak, M.; Drake, J. F.; Opher, M. E-mail: drake@umd.edu

    2013-09-01

    The picture of the heliopause (HP)-the boundary between the domains of the Sun and the local interstellar medium (LISM)-as a pristine interface with a large rotation in the magnetic field fails to describe recent Voyager 1 (V1) data. Magnetohydrodynamic (MHD) simulations of the global heliosphere reveal that the rotation angle of the magnetic field across the HP at V1 is small. Particle-in-cell simulations, based on cuts through the MHD model at V1's location, suggest that the sectored region of the heliosheath (HS) produces large-scale magnetic islands that reconnect with the interstellar magnetic field while mixing LISM and HS plasma. Cuts across the simulation reveal multiple, anti-correlated jumps in the number densities of LISM and HS particles, similar to those observed, at the magnetic separatrices. A model is presented, based on both the observations and simulations, of the HP as a porous, multi-layered structure threaded by magnetic fields. This model further suggests that contrary to the conclusions of recent papers, V1 has already crossed the HP.

  9. Decellularized matrices for cardiovascular tissue engineering

    PubMed Central

    Moroni, Francesco; Mirabella, Teodelinda

    2014-01-01

    Cardiovascular disease (CVD) is one of the leading causes of death in the Western world. The replacement of damaged vessels and valves has been practiced since the 1950’s. Synthetic grafts, usually made of bio-inert materials, are long-lasting and mechanically relevant, but fail when it comes to “biointegration”. Decellularized matrices, instead, can be considered biological grafts capable of stimulating in vivo migration and proliferation of endothelial cells (ECs), recruitment and differentiation of mural cells, finally, culminating in the formation of a biointegrated tissue. Decellularization protocols employ osmotic shock, ionic and non-ionic detergents, proteolitic digestions and DNase/RNase treatments; most of them effectively eliminate the cellular component, but show limitations in preserving the native structure of the extracellular matrix (ECM). In this review, we examine the current state of the art relative to decellularization techniques and biological performance of decellularized heart, valves and big vessels. Furthermore, we focus on the relevance of ECM components, native and resulting from decellularization, in mediating in vivo host response and determining repair and regeneration, as opposed to graft corruption. PMID:24660110

  10. On polynomial preconditioning for indefinite Hermitian matrices

    NASA Technical Reports Server (NTRS)

    Freund, Roland W.

    1989-01-01

    The minimal residual method is studied combined with polynomial preconditioning for solving large linear systems (Ax = b) with indefinite Hermitian coefficient matrices (A). The standard approach for choosing the polynomial preconditioners leads to preconditioned systems which are positive definite. Here, a different strategy is studied which leaves the preconditioned coefficient matrix indefinite. More precisely, the polynomial preconditioner is designed to cluster the positive, resp. negative eigenvalues of A around 1, resp. around some negative constant. In particular, it is shown that such indefinite polynomial preconditioners can be obtained as the optimal solutions of a certain two parameter family of Chebyshev approximation problems. Some basic results are established for these approximation problems and a Remez type algorithm is sketched for their numerical solution. The problem of selecting the parameters such that the resulting indefinite polynomial preconditioners speeds up the convergence of minimal residual method optimally is also addressed. An approach is proposed based on the concept of asymptotic convergence factors. Finally, some numerical examples of indefinite polynomial preconditioners are given.

  11. Osteogenic signaling on silk-based matrices.

    PubMed

    Midha, Swati; Murab, Sumit; Ghosh, Sourabh

    2016-08-01

    Bone tissue engineering has mainly focused on generating 3D grafts to repair bone defects. However, the underlying signaling mechanisms responsible for development of such 3D bone equivalents have largely been ignored. Here we describe the crucial aspects of embryonic osteogenesis and bone development including cell sources and general signaling cascades that guide mesenchymal progenitors towards osteogenic lineage. Drawing from the knowledge of developmental biology, we then review how silk biomaterial can regulate osteogenic signaling by focusing on the expression of cell surface markers, functional genomic information (mRNA) of stem cells cultured on silk matrices. In an attempt to recapitulate exact in vivo microenvironment of osteogenesis, role of scaffold architecture and material chemistry in regulating cellular differentiation is elaborated. The generated knowledge will not only improve our understanding of cell-material interactions but reveal newer strategies beyond a conventional tissue engineering paradigm and open new prospects for developing silk-based therapies against clinically relevant bone disorders. PMID:27163625

  12. Substituted amylose matrices for oral drug delivery

    NASA Astrophysics Data System (ADS)

    Moghadam, S. H.; Wang, H. W.; Saddar El-Leithy, E.; Chebli, C.; Cartilier, L.

    2007-03-01

    High amylose corn starch was used to obtain substituted amylose (SA) polymers by chemically modifying hydroxyl groups by an etherification process using 1,2-epoxypropanol. Tablets for drug-controlled release were prepared by direct compression and their release properties assessed by an in vitro dissolution test (USP XXIII no 2). The polymer swelling was characterized by measuring gravimetrically the water uptake ability of polymer tablets. SA hydrophilic matrix tablets present sequentially a burst effect, typical of hydrophilic matrices, and a near constant release, typical of reservoir systems. After the burst effect, surface pores disappear progressively by molecular association of amylose chains; this allows the creation of a polymer layer acting as a diffusion barrier and explains the peculiar behaviour of SA polymers. Several formulation parameters such as compression force, drug loading, tablet weight and insoluble diluent concentration were investigated. On the other hand, tablet thickness, scanning electron microscope analysis and mercury intrusion porosimetry showed that the high crushing strength values observed for SA tablets were due to an unusual melting process occurring during tabletting although the tablet external layer went only through densification, deformation and partial melting. In contrast, HPMC tablets did not show any traces of a melting process.

  13. Occam's razor in quark mass matrices

    NASA Astrophysics Data System (ADS)

    Tanimoto, Morimitsu; Yanagida, Tsutomu T.

    2016-04-01

    From the standpoint of the Occam's razor approach, we consider the minimum number of parameters in the quark mass matrices needed for successful CKM mixing and CP violation. We impose three zeros in the down-quark mass matrix while taking the diagonal up-quark mass matrix to reduce the number of free parameters. The three zeros are maximal zeros in order to have a CP-violating phase in the quark mass matrix. Then, there remain six real parameters and one CP-violating phase, which is the minimal number needed to reproduce the observed data of the down-quark masses and the CKM parameters. Twenty textures with three zeros are examined. Among these, thirteen textures are viable for the down-quark mass matrix. As a representative of these textures, we discuss a texture Md^{(1)} in detail. By using the experimental data on sin 2β , θ _{13}, and θ _{23}, together with the observed quark masses, the Cabibbo angle is predicted to be close to the experimental data. It is found that this surprising result remains unchanged in all other viable textures. We also investigate the correlations between |V_{ub}/V_{cb}|, sin 2β , and J_CP. For all textures, the maximal value of the ratio |V_{ub}/V_{cb}| is 0.09, which is smaller than the upper bound of the experimental data, 0.094. We hope that this prediction will be tested in future experiments.

  14. Generalized graph states based on Hadamard matrices

    SciTech Connect

    Cui, Shawn X.; Yu, Nengkun; Zeng, Bei

    2015-07-15

    Graph states are widely used in quantum information theory, including entanglement theory, quantum error correction, and one-way quantum computing. Graph states have a nice structure related to a certain graph, which is given by either a stabilizer group or an encoding circuit, both can be directly given by the graph. To generalize graph states, whose stabilizer groups are abelian subgroups of the Pauli group, one approach taken is to study non-abelian stabilizers. In this work, we propose to generalize graph states based on the encoding circuit, which is completely determined by the graph and a Hadamard matrix. We study the entanglement structures of these generalized graph states and show that they are all maximally mixed locally. We also explore the relationship between the equivalence of Hadamard matrices and local equivalence of the corresponding generalized graph states. This leads to a natural generalization of the Pauli (X, Z) pairs, which characterizes the local symmetries of these generalized graph states. Our approach is also naturally generalized to construct graph quantum codes which are beyond stabilizer codes.

  15. The Representation and Parametrization of Orthogonal Matrices.

    PubMed

    Shepard, Ron; Brozell, Scott R; Gidofalvi, Gergely

    2015-07-16

    Four representations and parametrizations of orthogonal matrices Q ∈ R(m×n) in terms of the minimal number of essential parameters {φ} are discussed: the exponential representation, the Householder reflector representation, the Givens rotation representation, and the rational Cayley transform representation. Both square n = m and rectangular n < m situations are considered. Two separate kinds of parametrizations are considered: one in which the individual columns of Q are distinct, the Stiefel manifold, and the other in which only span(Q) is significant, the Grassmann manifold. The practical issues of numerical stability, continuity, and uniqueness are discussed. The computation of Q in terms of the essential parameters {φ}, and also the extraction of {φ} for a given Q are considered for all of the parametrizations. The transformation of gradient arrays between the Q and {φ} variables is discussed for all representations. It is our hope that developers of new methods will benefit from this comparative presentation of an important but rarely analyzed subject. PMID:25946418

  16. Photochemistry of glycolaldehyde in cryogenic matrices.

    PubMed

    Chin, W; Chevalier, M; Thon, R; Pollet, R; Ceponkus, J; Crépin, C

    2014-06-14

    The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH3OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H2CO and HCO fragments are seen. Calculations of the potential energy surfaces of S0, S1, and T1 states--to analyse the torsional deformations which are involved in the isomerization process--and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH3OH molecular channel is a minor process, as in the gas phase. PMID:24929400

  17. Partitioning sparse matrices with eigenvectors of graphs

    NASA Technical Reports Server (NTRS)

    Pothen, Alex; Simon, Horst D.; Liou, Kang-Pu

    1990-01-01

    The problem of computing a small vertex separator in a graph arises in the context of computing a good ordering for the parallel factorization of sparse, symmetric matrices. An algebraic approach for computing vertex separators is considered in this paper. It is shown that lower bounds on separator sizes can be obtained in terms of the eigenvalues of the Laplacian matrix associated with a graph. The Laplacian eigenvectors of grid graphs can be computed from Kronecker products involving the eigenvectors of path graphs, and these eigenvectors can be used to compute good separators in grid graphs. A heuristic algorithm is designed to compute a vertex separator in a general graph by first computing an edge separator in the graph from an eigenvector of the Laplacian matrix, and then using a maximum matching in a subgraph to compute the vertex separator. Results on the quality of the separators computed by the spectral algorithm are presented, and these are compared with separators obtained from other algorithms for computing separators. Finally, the time required to compute the Laplacian eigenvector is reported, and the accuracy with which the eigenvector must be computed to obtain good separators is considered. The spectral algorithm has the advantage that it can be implemented on a medium-size multiprocessor in a straightforward manner.

  18. Photochemistry of glycolaldehyde in cryogenic matrices

    SciTech Connect

    Chin, W. Chevalier, M.; Thon, R.; Crépin, C.; Pollet, R.

    2014-06-14

    The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH{sub 3}OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H{sub 2}CO and HCO fragments are seen. Calculations of the potential energy surfaces of S{sub 0}, S{sub 1}, and T{sub 1} states – to analyse the torsional deformations which are involved in the isomerization process – and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH{sub 3}OH molecular channel is a minor process, as in the gas phase.

  19. Non-viral gene-activated matrices

    PubMed Central

    Tierney, Erica G.; Duffy, Garry P.; Cryan, Sally-Ann; Curtin, Caroline M.; O’Brien, Fergal J.

    2013-01-01

    In the context of producing enhanced therapeutics for regenerative medicine, our laboratory develops gene-activated matrices (GAMs) using non-viral gene therapy (GT) in combination with collagen-based scaffolds engineered specifically for tissue repair. Non-viral vectors have been referred to as a minority pursuit in GT but considering the concerns associated with viral vectors and as transient gene expression is such a key consideration, further research is clearly warranted for tissue engineering (TE) applications. Mesenchymal stem cells (MSCs) are well regarded for their capability in bone regeneration but as primary cells, they are difficult to transfect. We have recently optimised the non-viral vector, polyethyleneimine (PEI), to achieve high transfection efficiencies in MSCs. Subsequently, a series of PEI-based GAMs were developed using collagen, collagen-glycosaminoglycan and collagen-nanohydroxyapatite (collagen-nHa) scaffolds whereby transgene expression was detected up to 21 d with the collagen-nHa scaffold providing the most prolonged expression. Moreover, all PEI-based GAMs contained a low plasmid DNA dose of 2 µg which is far below doses often required in previous GAMs. Having successfully developed these GAMs, the ephrinB2 gene has recently been incorporated to produce a novel therapeutic GAM for bone repair. Herein, we discuss our recent investigations in the development and application of non-viral GAMs. PMID:23538777

  20. Automated building extraction using dense elevation matrices

    NASA Astrophysics Data System (ADS)

    Bendett, A. A.; Rauhala, Urho A.; Pearson, James J.

    1997-02-01

    The identification and measurement of buildings in imagery is important to a number of applications including cartography, modeling and simulation, and weapon targeting. Extracting large numbers of buildings manually can be time- consuming and expensive, so the automation of the process is highly desirable. This paper describes and demonstrates such an automated process for extracting rectilinear buildings from stereo imagery. The first step is the generation of a dense elevation matrix registered to the imagery. In the examples shown, this was accomplished using global minimum residual matching (GMRM). GMRM automatically removes y- parallax from the stereo imagery and produces a dense matrix of x-parallax values which are proportional to the local elevation, and, of course, registered to the imagery. The second step is to form a joint probability distribution of the image gray levels and the corresponding height values from the elevation matrix. Based on the peaks of that distribution, the area of interest is segmented into feature and non-feature areas. The feature areas are further refined using length, width and height constraints to yield promising building hypotheses with their corresponding vertices. The gray shade image is used in the third step to verify the hypotheses and to determine precise edge locations corresponding to the approximate vertices and satisfying appropriate orthogonality constraints. Examples of successful application of this process to imagery are presented, and extensions involving the use of dense elevation matrices from other sources are possible.

  1. A constitutive theory of reacting electrolyte mixtures

    NASA Astrophysics Data System (ADS)

    Costa Reis, Martina; Wang, Yongqi; Bono Maurizio Sacchi Bassi, Adalberto

    2013-11-01

    A constitutive theory of reacting electrolyte mixtures is formulated. The intermolecular interactions among the constituents of the mixture are accounted for through additional freedom degrees to each constituent of the mixture. Balance equations for polar reacting continuum mixtures are accordingly formulated and a proper set of constitutive equations is derived with basis in the Müller-Liu formulation of the second law of thermodynamics. Moreover, the non-equilibrium and equilibrium responses of the reacting mixture are investigated in detail by emphasizing the inner and reactive structures of the medium. From the balance laws and constitutive relations, the effects of molecular structure of constituents upon the fluid flow are studied. It is also demonstrated that the local thermodynamic equilibrium state can be reached without imposing that the set of independent constitutive variables is time independent, neither spatially homogeneous nor null. The resulting constitutive relations presented throughout this work are of relevance to many practical applications, such as swelling of clays, developing of bio and polymeric membranes, and use of electrorheological fluids in industrial processes. The first author acknowledges financial support from National Counsel of Technological and Scientific Development (CNPq) and German Academic Exchange Service (DAAD).

  2. Health care law versus constitutional law.

    PubMed

    Hall, Mark A

    2013-04-01

    National Federation of Independent Business v. Sebelius, the Supreme Court's ruling on the Patient Protection and Affordable Care Act, is a landmark decision - both for constitutional law and for health care law and policy. Others will study its implications for constitutional limits on a range of federal powers beyond health care. This article considers to what extent the decision is also about health care law, properly conceived. Under one view, health care law is the subdiscipline that inquires how courts and government actors take account of the special features of medicine that make legal or policy issues especially problematic - rather than regarding health care delivery and finance more generically, like most any other economic or social enterprise. Viewed this way, the opinions from the Court's conservative justices are mainly about general constitutional law principles. In contrast, Justice Ruth Bader Ginsburg's dissenting opinion for the four more liberal justices is just as much about health care law as it is about constitutional law. Her opinion gives detailed attention to the unique features of health care finance and delivery in order to inform her analysis of constitutional precedents and principles. Thus, the Court's multiple opinions give a vivid depiction of the compelling contrasts between communal versus individualistic conceptions of caring for those in need, and between health care and health insurance as ordinary commodities versus ones that merit special economic, social, and legal status. PMID:23262771

  3. Multiscale porous fuel cell electrodes

    NASA Astrophysics Data System (ADS)

    Wen, Hao

    Porous electrodes are widely used in fuel cells to enhance electrode performance due to their high surface area. Increasingly, such electrodes are designed with both micro-scale and nano-scale features. In the current work, carbon based porous materials have been synthesized and utilized as bioelectrode support for biofuel cells, analysis of such porous electrodes via rotating disk electrode has been enhanced by a numerical model that considers diffusion and convection within porous media. Finally, porous perovskite metal oxide cathodes for solid oxide fuel cell have been modeled to simulate impedance response data obtained from symmetric cells. Carbon fiber microelectrodes (CFME) were fabricated to mimic the microenvironment of carbon fiber paper based porous electrodes. They were also miniature electrodes for small-scale applications. As observed by scanning electron microscopy (SEM), carbon nanotubes (CNTs) formed a homogeneously intertwined matrix. Biocatalysts can fully infiltrate this matrix to form a composite, with a significantly enhanced glucose oxidation current---that is 6.4 fold higher than the bare carbon fiber electrodes. Based on the CNT based porous matrix, polystyrene beads of uniform diameter at 500 nm were used as template to tune the porous structure and enhance biomolecule transport. Focused ion beam (FIB) was used to observe the morphology both at the surface and the cross-section. It has been shown that the template macro-pores enhanced the fuel transport and the current density has been doubled due to the improvement. Like commonly used rotating disk electrode, the porous rotating disk electrode is a system with analytically solved flow field. Although models were proposed previously with first order kinetics and convection as the only mass transport at high rotations, some recent findings indicated that diffusion could play an important role at all disk rotation rates. In the current proposed model, enzymatic kinetics that follow a Ping

  4. Effective parameters for two-phase flow in a porous medium with periodic heterogeneities

    NASA Astrophysics Data System (ADS)

    Ataie-Ashtiani, B.; Hassanizadeh, S. M.; Oostrom, M.; Celia, M. A.; White, M. D.

    2001-05-01

    Computational simulations of two-phase flow in porous media are used to investigate the feasibility of replacing a porous medium containing heterogeneities with an equivalent homogeneous medium. Simulations are performed for the case of infiltration of a dense nonaqueous phase liquid (DNAPL) in a water-saturated, heterogeneous porous medium. For two specific porous media, with periodic and rather simple heterogeneity patterns, the existence of a representative elementary volume (REV) is studied. Upscaled intrinsic permeabilities and upscaled nonlinear constitutive relationships for two-phase flow systems are numerically calculated and the effects of heterogeneities are evaluated. Upscaled capillary pressure-saturation curves for drainage are found to be distinctly different from the lower-scale curves for individual regions of heterogeneity. Irreducible water saturation for the homogenized medium is found to be much larger than the corresponding lower-scale values. Numerical simulations for both heterogeneous and homogeneous representations of the considered porous media are carried out. Although the homogenized model simulates the spreading behavior of DNAPL reasonably well, it still fails to match completely the results form the heterogeneous simulations. This seems to be due, in part, to the nonlinearities inherent to multiphase flow systems. Although we have focussed on a periodic heterogeneous medium in this study, our methodology is applicable to other forms of heterogeneous media. In particular, the procedure for identification of a REV, and associated upscaled constitutive relations, can be used for randomly heterogeneous or layered media as well.

  5. Bunch-Kaufman factorization for real symmetric indefinite banded matrices

    NASA Technical Reports Server (NTRS)

    Jones, Mark T.; Patrick, Merrell L.

    1989-01-01

    The Bunch-Kaufman algorithm for factoring symmetric indefinite matrices was rejected for banded matrices because it destroys the banded structure of the matrix. Herein, it is shown that for a subclass of real symmetric matrices which arise in solving the generalized eigenvalue problem using Lanczos's method, the Bunch-Kaufman algorithm does not result in major destruction of the bandwidth. Space time complexities of the algorithm are given and used to show that the Bunch-Kaufman algorithm is a significant improvement over LU factorization.

  6. On the asymptotic distribution of block-modified random matrices

    NASA Astrophysics Data System (ADS)

    Arizmendi, Octavio; Nechita, Ion; Vargas, Carlos

    2016-01-01

    We study random matrices acting on tensor product spaces which have been transformed by a linear block operation. Using operator-valued free probability theory, under some mild assumptions on the linear map acting on the blocks, we compute the asymptotic eigenvalue distribution of the modified matrices in terms of the initial asymptotic distribution. Moreover, using recent results on operator-valued subordination, we present an algorithm that computes, numerically but in full generality, the limiting eigenvalue distribution of the modified matrices. Our analytical results cover many cases of interest in quantum information theory: we unify some known results and we obtain new distributions and various generalizations.

  7. Phase direct CP violations and general mixing matrices

    NASA Astrophysics Data System (ADS)

    Chau, Ling-Lie

    2007-08-01

    I formulate expressions for amplitudes suitable for quantifying both modulus and phase direct CP violations. They result in Möbius transformation (MT) relations, which provide encouraging information for the search of direct CP violations in general. I apply the formulation to calculate the measurements of phase direct CP violations and strong amplitudes in B∓ →K∓π±π∓ by the Belle Collaboration. For the formulation, I show a versatile construction procedure for N × N Cabibbo-Kobayashi-Maskawa (CKM) matrices, Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrices, and general unitary matrices. It clarifies the 3 × 3 cases and is useful for the beyond.

  8. Random transition-rate matrices for the master equation.

    PubMed

    Timm, Carsten

    2009-08-01

    Random-matrix theory is applied to transition-rate matrices in the Pauli master equation. We study the distribution and correlations of eigenvalues, which govern the dynamics of complex stochastic systems. Both the cases of identical and of independent rates of forward and backward transitions are considered. The first case leads to symmetric transition-rate matrices, whereas the second corresponds to general asymmetric matrices. The resulting matrix ensembles are different from the standard ensembles and show different eigenvalue distributions. For example, the fraction of real eigenvalues scales anomalously with matrix dimension in the asymmetric case. PMID:19792110

  9. Large Deformations of a Soft Porous Material

    NASA Astrophysics Data System (ADS)

    MacMinn, Christopher W.; Dufresne, Eric R.; Wettlaufer, John S.

    2016-04-01

    Compressing a porous material will decrease the volume of the pore space, driving fluid out. Similarly, injecting fluid into a porous material can expand the pore space, distorting the solid skeleton. This poromechanical coupling has applications ranging from cell and tissue mechanics to geomechanics and hydrogeology. The classical theory of linear poroelasticity captures this coupling by combining Darcy's law with Terzaghi's effective stress and linear elasticity in a linearized kinematic framework. Linear poroelasticity is a good model for very small deformations, but it becomes increasingly inappropriate for moderate to large deformations, which are common in the context of phenomena such as swelling and damage, and for soft materials such as gels and tissues. The well-known theory of large-deformation poroelasticity combines Darcy's law with Terzaghi's effective stress and nonlinear elasticity in a rigorous kinematic framework. This theory has been used extensively in biomechanics to model large elastic deformations in soft tissues and in geomechanics to model large elastoplastic deformations in soils. Here, we first provide an overview and discussion of this theory with an emphasis on the physics of poromechanical coupling. We present the large-deformation theory in an Eulerian framework to minimize the mathematical complexity, and we show how this nonlinear theory simplifies to linear poroelasticity under the assumption of small strain. We then compare the predictions of linear poroelasticity with those of large-deformation poroelasticity in the context of two uniaxial model problems: fluid outflow driven by an applied mechanical load (the consolidation problem) and compression driven by a steady fluid throughflow. We explore the steady and dynamical errors associated with the linear model in both situations, as well as the impact of introducing a deformation-dependent permeability. We show that the error in linear poroelasticity is due primarily to kinematic

  10. On optimal filtering of measured Mueller matrices

    NASA Astrophysics Data System (ADS)

    Gil, José J.

    2016-07-01

    While any two-dimensional mixed state of polarization of light can be represented by a combination of a pure state and a fully random state, any Mueller matrix can be represented by a convex combination of a pure component and three additional components whose randomness is scaled in a proper and objective way. Such characteristic decomposition constitutes the appropriate framework for the characterization of the polarimetric randomness of the system represented by a given Mueller matrix, and provides criteria for the optimal filtering of noise in experimental polarimetry.

  11. A survey of unified constitutive theories

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Lindholm, U. S.; Bodner, S. R.; Walker, K. P.

    1985-01-01

    The state of the art of time temperature dependent elastic viscoplastic constitutive theories which are based on the unified approach werre assessed. This class of constitutive theories is characterized by the use of kinetic equations and internal variables with appropriate evolutionary equations for treating all aspects of inelastic deformation including plasticity, creep, and stress relaxation. More than 10 such unified theories which are shown to satisfy the uniqueness and stability criteria imposed by Drucker's postulate and Ponter's inequalities are identified. The theories are compared for the types of flow law, kinetic equation, evolutionary equation of the internal variables, and treatment of temperature dependence. The similarities and differences of these theories are outlined in terms of mathematical formulations and illustrated by comparisons of theoretical calculations with experimental results which include monotonic stress-strain curves, cyclic hysteresis loops, creep and stress relaxation rates, and thermomechanical loops. Numerical methods used for integrating these stiff time temperature dependent constitutive equations are reviewed.

  12. Acoustomechanical constitutive theory for soft materials

    NASA Astrophysics Data System (ADS)

    Xin, Fengxian; Lu, Tian Jian

    2016-07-01

    Acoustic wave propagation from surrounding medium into a soft material can generate acoustic radiation stress due to acoustic momentum transfer inside the medium and material, as well as at the interface between the two. To analyze acoustic-induced deformation of soft materials, we establish an acoustomechanical constitutive theory by combining the acoustic radiation stress theory and the nonlinear elasticity theory for soft materials. The acoustic radiation stress tensor is formulated by time averaging the momentum equation of particle motion, which is then introduced into the nonlinear elasticity constitutive relation to construct the acoustomechanical constitutive theory for soft materials. Considering a specified case of soft material sheet subjected to two counter-propagating acoustic waves, we demonstrate the nonlinear large deformation of the soft material and analyze the interaction between acoustic waves and material deformation under the conditions of total reflection, acoustic transparency, and acoustic mismatch.

  13. Modeling the Impact of Alternative Immunization Strategies: Using Matrices as Memory Lanes

    PubMed Central

    Alonso, Wladimir J.; Rabaa, Maia A.; Giglio, Ricardo; Miller, Mark A.; Schuck-Paim, Cynthia

    2015-01-01

    Existing modeling approaches are divided between a focus on the constitutive (micro) elements of systems or on higher (macro) organization levels. Micro-level models enable consideration of individual histories and interactions, but can be unstable and subject to cumulative errors. Macro-level models focus on average population properties, but may hide relevant heterogeneity at the micro-scale. We present a framework that integrates both approaches through the use of temporally structured matrices that can take large numbers of variables into account. Matrices are composed of several bidimensional (time×age) grids, each representing a state (e.g. physiological, immunological, socio-demographic). Time and age are primary indices linking grids. These matrices preserve the entire history of all population strata and enable the use of historical events, parameters and states dynamically in the modeling process. This framework is applicable across fields, but particularly suitable to simulate the impact of alternative immunization policies. We demonstrate the framework by examining alternative strategies to accelerate measles elimination in 15 developing countries. The model recaptured long-endorsed policies in measles control, showing that where a single routine measles-containing vaccine is employed with low coverage, any improvement in coverage is more effective than a second dose. It also identified an opportunity to save thousands of lives in India at attractively low costs through the implementation of supplementary immunization campaigns. The flexibility of the approach presented enables estimating the effectiveness of different immunization policies in highly complex contexts involving multiple and historical influences from different hierarchical levels. PMID:26509976

  14. Long-Range Force Transmission in Fibrous Matrices Enabled by Tension-Driven Alignment of Fibers

    PubMed Central

    Wang, Hailong; Abhilash, A.S.; Chen, Christopher S.; Wells, Rebecca G.; Shenoy, Vivek B.

    2014-01-01

    Cells can sense and respond to mechanical signals over relatively long distances across fibrous extracellular matrices. Recently proposed models suggest that long-range force transmission can be attributed to the nonlinear elasticity or fibrous nature of collagen matrices, yet the mechanism whereby fibers align remains unknown. Moreover, cell shape and anisotropy of cellular contraction are not considered in existing models, although recent experiments have shown that they play crucial roles. Here, we explore all of the key factors that influence long-range force transmission in cell-populated collagen matrices: alignment of collagen fibers, responses to applied force, strain stiffening properties of the aligned fibers, aspect ratios of the cells, and the polarization of cellular contraction. A constitutive law accounting for mechanically driven collagen fiber reorientation is proposed. We systematically investigate the range of collagen-fiber alignment using both finite-element simulations and analytical calculations. Our results show that tension-driven collagen-fiber alignment plays a crucial role in force transmission. Small critical stretch for fiber alignment, large fiber stiffness and fiber strain-hardening behavior enable long-range interaction. Furthermore, the range of collagen-fiber alignment for elliptical cells with polarized contraction is much larger than that for spherical cells with diagonal contraction. A phase diagram showing the range of force transmission as a function of cell shape and polarization and matrix properties is presented. Our results are in good agreement with recent experiments, and highlight the factors that influence long-range force transmission, in particular tension-driven alignment of fibers. Our work has important relevance to biological processes including development, cancer metastasis, and wound healing, suggesting conditions whereby cells communicate over long distances. PMID:25468338

  15. Modeling the Impact of Alternative Immunization Strategies: Using Matrices as Memory Lanes.

    PubMed

    Alonso, Wladimir J; Rabaa, Maia A; Giglio, Ricardo; Miller, Mark A; Schuck-Paim, Cynthia

    2015-01-01

    Existing modeling approaches are divided between a focus on the constitutive (micro) elements of systems or on higher (macro) organization levels. Micro-level models enable consideration of individual histories and interactions, but can be unstable and subject to cumulative errors. Macro-level models focus on average population properties, but may hide relevant heterogeneity at the micro-scale. We present a framework that integrates both approaches through the use of temporally structured matrices that can take large numbers of variables into account. Matrices are composed of several bidimensional (time×age) grids, each representing a state (e.g. physiological, immunological, socio-demographic). Time and age are primary indices linking grids. These matrices preserve the entire history of all population strata and enable the use of historical events, parameters and states dynamically in the modeling process. This framework is applicable across fields, but particularly suitable to simulate the impact of alternative immunization policies. We demonstrate the framework by examining alternative strategies to accelerate measles elimination in 15 developing countries. The model recaptured long-endorsed policies in measles control, showing that where a single routine measles-containing vaccine is employed with low coverage, any improvement in coverage is more effective than a second dose. It also identified an opportunity to save thousands of lives in India at attractively low costs through the implementation of supplementary immunization campaigns. The flexibility of the approach presented enables estimating the effectiveness of different immunization policies in highly complex contexts involving multiple and historical influences from different hierarchical levels. PMID:26509976

  16. Thermoelastic constitutive equations for chemically hardening materials

    NASA Technical Reports Server (NTRS)

    Shaffer, B. W.; Levitsky, M.

    1974-01-01

    Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.

  17. Dielectric properties of porous aluminum and silicon oxides with inclusions of triglycine sulfate and its modified analogs

    NASA Astrophysics Data System (ADS)

    Golitsyna, O. M.; Drozhdin, S. N.; Nechaev, V. N.; Viskovatykh, A. V.; Kashkarov, V. M.; Gridnev, A. E.; Chernyshev, V. V.

    2013-03-01

    This paper reports on an investigation of the temperature dependences of the capacitance and conductance of composite materials prepared by incorporating the ferroelectric TGS and its analogs—TGS with addition of L,α-alanine and chromium—into porous Al2O3 and SiO2 matrices. It has been established that conduction of the structures under study involves charge transport predominantly through the ferroelectric embedded in the porous matrix. A mechanism is proposed to account for the displacement of the phase transition temperature of the ferroelectric inclusion under "restricted geometry" conditions, which is driven by the difference between the thermal expansion coefficients of the porous matrix and the embedded ferroelectric.

  18. Homogenized stiffness matrices for mineralized collagen fibrils and lamellar bone using unit cell finite element models.

    PubMed

    Vercher, Ana; Giner, Eugenio; Arango, Camila; Tarancón, José E; Fuenmayor, F Javier

    2014-04-01

    Mineralized collagen fibrils have been usually analyzed like a two-phase composite material where crystals are considered as platelets that constitute the reinforcement phase. Different models have been used to describe the elastic behavior of the material. In this work, it is shown that when Halpin-Tsai equations are applied to estimate elastic constants from typical constituent properties, not all crystal dimensions yield a model that satisfy thermodynamic restrictions. We provide the ranges of platelet dimensions that lead to positive definite stiffness matrices. On the other hand, a finite element model of a mineralized collagen fibril unit cell under periodic boundary conditions is analyzed. By applying six canonical load cases, homogenized stiffness matrices are numerically calculated. Results show a monoclinic behavior of the mineralized collagen fibril. In addition, a 5-layer lamellar structure is also considered where crystals rotate in adjacent layers of a lamella. The stiffness matrix of each layer is calculated applying Lekhnitskii transformations, and a new finite element model under periodic boundary conditions is analyzed to calculate the homogenized 3D anisotropic stiffness matrix of a unit cell of lamellar bone. Results are compared with the rule-of-mixtures showing in general good agreement. PMID:23793930

  19. Separation of traces of metal ions from sodium matrices

    NASA Technical Reports Server (NTRS)

    Korkisch, J.; Orlandini, K. A.

    1969-01-01

    Method for isolating metal ion traces from sodium matrices consists of two extractions and an ion exchange step. Extraction is accomplished by using 2-thenoyltrifluoracetone and dithizone followed by cation exchange.

  20. ALGORITHM FOR THE EVALUATION OF REDUCED WIGNER MATRICES

    SciTech Connect

    Prezeau, G.; Reinecke, M.

    2010-10-15

    Algorithms for the fast and exact computation of Wigner matrices are described and their application to a fast and massively parallel 4{pi} convolution code between a beam and a sky is also presented.

  1. Morphic images of binary words and Parikh matrices

    NASA Astrophysics Data System (ADS)

    Isawasan, Pradeep; Venkat, Ibrahim; Subramanian, K. G.; Sarmin, Nor Haniza

    2014-07-01

    A word is a finite sequence of symbols. Parikh matrix of a word, introduced by Mateescu et al (2000), has become an effective tool in the study of certain numerical properties of words based on subwords. There have been several investigations on various properties of Parikh matrices such as M-ambiguity, M-equivalence, subword equalities and inequalities, commutativity and so on. Recently, Parikh matrices of words that are images under certain morphisms have been studied for their properties. On the other hand, Parikh matrices of words involving a certain ratio property called weak-ratio property have been investigated by Subramanian et al (2009). Here we consider two special morphisms called Fibonacci and Tribonacci morphisms and obtain properties of Parikh matrices of images of binary words under these morphisms, utilizing the notion of weak-ratio property.

  2. Spectral density of a Wishart model for nonsymmetric correlation matrices

    NASA Astrophysics Data System (ADS)

    Vinayak

    2013-10-01

    The Wishart model for real symmetric correlation matrices is defined as W=AAt, where matrix A is usually a rectangular Gaussian random matrix and At is the transpose of A. Analogously, for nonsymmetric correlation matrices, a model may be defined for two statistically equivalent but different matrices A and B as ABt. The corresponding Wishart model, thus, is defined as C=ABtBAt. We study the spectral density of C for the case when A and B are not statistically independent. The ensemble average of such nonsymmetric matrices, therefore, does not simply vanishes to a null matrix. In this paper we derive a Pastur self-consistent equation which describes spectral density of C at large matrix dimension. We complement our analytic results with numerics.

  3. Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices

    ERIC Educational Resources Information Center

    Glaister, P.

    2008-01-01

    The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.

  4. Performance Properties of Graphite Reinforced Composites with Advanced Resin Matrices

    NASA Technical Reports Server (NTRS)

    Kourtides, Demetrius A.

    1980-01-01

    This article looks at the effect of different resin matrices on thermal and mechanical properties of graphite composites, and relates the thermal and flammability properties to the anaerobic char yield of the resins. The processing parameters of graphite composites utilizing graphite fabric and epoxy or other advanced resins as matrices are presented. Thermoset resin matrices studied were: aminecured polyfunctional glycidyl aminetype epoxy (baseline), phenolicnovolac resin based on condensation of dihydroxymethyl-xylene and phenol cured with hexamine, two types of polydismaleimide resins, phenolic resin, and benzyl resin. The thermoplastic matrices studied were polyethersulfone and polyphenylenesulfone. Properties evaluated in the study included anaerobic char yield, limiting oxygen index, smoke evolution, moisture absorption, and mechanical properties at elevated temperatures including tensile, compressive, and short-beam shear strengths. Generally, it was determined that graphite composites with the highest char yield exhibited optimum fire-resistant properties.

  5. Compressed Sensing for the Fast Computation of Matrices: Application to Molecular Vibrations

    PubMed Central

    2015-01-01

    This article presents a new method to compute matrices from numerical simulations based on the ideas of sparse sampling and compressed sensing. The method is useful for problems where the determination of the entries of a matrix constitutes the computational bottleneck. We apply this new method to an important problem in computational chemistry: the determination of molecular vibrations from electronic structure calculations, where our results show that the overall scaling of the procedure can be improved in some cases. Moreover, our method provides a general framework for bootstrapping cheap low-accuracy calculations in order to reduce the required number of expensive high-accuracy calculations, resulting in a significant 3× speed-up in actual calculations. PMID:27162943

  6. Silk matrices promote formation of insulin-secreting islet-like clusters.

    PubMed

    Shalaly, Nancy Dekki; Ria, Massimiliano; Johansson, Ulrika; Åvall, Karin; Berggren, Per-Olof; Hedhammar, My

    2016-06-01

    Ex vivo expansion of endocrine cells constitutes an interesting alternative to be able to match the unmet need of transplantable pancreatic islets. However, endocrine cells become fragile once removed from their extracellular matrix (ECM) and typically become senescent and loose insulin expression during conventional 2D culture. Herein we develop a protocol where 3D silk matrices functionalized with ECM-derived motifs are used for generation of insulin-secreting islet-like clusters from mouse and human primary cells. The obtained clusters were shown to attain an islet-like spheroid shape and to maintain functional insulin release upon glucose stimulation in vitro. Furthermore, in vivo imaging of transplanted murine clusters showed engraftment with increasing vessel formation during time. There was no sign of cell death and the clusters maintained or increased in size throughout the period, thus suggesting a suitable cluster size for transplantation. PMID:26986856

  7. P03-based precession-nutation matrices

    NASA Astrophysics Data System (ADS)

    Wallace, P.; Capitaine, N.

    2006-10-01

    The IAU WG on precession and the ecliptic has recommended the adoption of the P03 models of Capitaine et al. (2003). We discuss methods for generating the rotation matrices that transform celestial to terrestrial coordinates, taking into account frame bias (B), P03 precession (P), P03-adjusted IAU 2000A nutation (N) and Earth rotation. The NPB portion can refer either to the equinox or the celestial intermediate origin (CIO), requiring either the Greenwich sidereal time (GST) or the Earth rotation angle (ERA) as the measure of Earth rotation. The equinox based NPB transformation can be formed using various sequences of rotations, while the CIO based transformation can be formed using series for the X, Y coordinates of the celestial intermediate pole (CIP) and for the CIO locator s; also, either matrix can be computing using series for the x, y, z components of the "rotation vector". Common to both methods is the CIP, which forms the bottom row of the transformation matrix. In the case of the CIO based transformation, the CIO is the top row of the NPB matrix, whereas in the equinox based case it enters via the GST formulation in the form of the equation of the origins (EO). The EO is the difference between ERA and GST and equivalently the distance between the CIO and equinox. The choice of method is dictated by considerations of internal consistency, flexibility and ease of use; the different ways agree at the level of a few microarcseconds over several centuries, and consume similar computing resources.

  8. Comparison of eigensolvers for symmetric band matrices

    PubMed Central

    Moldaschl, Michael; Gansterer, Wilfried N.

    2014-01-01

    We compare different algorithms for computing eigenvalues and eigenvectors of a symmetric band matrix across a wide range of synthetic test problems. Of particular interest is a comparison of state-of-the-art tridiagonalization-based methods as implemented in Lapack or Plasma on the one hand, and the block divide-and-conquer (BD&C) algorithm as well as the block twisted factorization (BTF) method on the other hand. The BD&C algorithm does not require tridiagonalization of the original band matrix at all, and the current version of the BTF method tridiagonalizes the original band matrix only for computing the eigenvalues. Avoiding the tridiagonalization process sidesteps the cost of backtransformation of the eigenvectors. Beyond that, we discovered another disadvantage of the backtransformation process for band matrices: In several scenarios, a lot of gradual underflow is observed in the (optional) accumulation of the transformation matrix and in the (obligatory) backtransformation step. According to the IEEE 754 standard for floating-point arithmetic, this implies many operations with subnormal (denormalized) numbers, which causes severe slowdowns compared to the other algorithms without backtransformation of the eigenvectors. We illustrate that in these cases the performance of existing methods from Lapack and Plasma reaches a competitive level only if subnormal numbers are disabled (and thus the IEEE standard is violated). Overall, our performance studies illustrate that if the problem size is large enough relative to the bandwidth, BD&C tends to achieve the highest performance of all methods if the spectrum to be computed is clustered. For test problems with well separated eigenvalues, the BTF method tends to become the fastest algorithm with growing problem size. PMID:26594079

  9. Radiative Properties of Silica Nanoporous Matrices

    NASA Astrophysics Data System (ADS)

    Lallich, Sylvain; Enguehard, Franck; Baillis, Dominique

    2008-08-01

    Superinsulating materials are currently of much interest because of the price of energy on the one hand and CO2 emissions attributed to offices and houses cooling and heating on the other hand. In this work, we aim at understanding and modeling the radiative transfer within silica nanoporous matrices that are the principal components of nanoporous superinsulating materials. We first elaborate samples of various thicknesses from a pyrogenic silica powder. These samples are characterized using two spectrophotometers on the whole wavelength range [250 nm; 20 μm]. Using a parameter identification technique, we compute the radiative properties of the various samples. Then, our samples being made of packed quasi-spherical particles, we use the Mie theory to model the radiative properties of these materials. Due to the observed discrepancies between the experimental radiative properties and those computed from the Mie theory with a uniform value of 10 nm for the scatterer diameter (value derived from TEM images), we determine an effective scatterer diameter that allows a good agreement between the experimental radiative properties and the Mie results. Nevertheless, in the short wavelength range, the Mie theory gives results that significantly differ from the experimental radiative properties. This behavior is attributed to structure effects as the wavelength is of the same order of magnitude as the diameter of the scatterer that is now regarded as an aggregate of nanoparticles. Hence, to take into account these effects, we use the discrete dipole approximation (DDA). The DDA extinction coefficient spectra appear to be much closer to the experimental results than the Mie spectra, and these first results are quite encouraging.

  10. Estimating soil matric potential in Owens Valley, California

    USGS Publications Warehouse

    Sorenson, Stephen K.; Miller, R.F.; Welch, M.R.; Groeneveld, D.P.; Branson, F.A.

    1988-01-01

    Much of the floor of the Owens Valley, California, is covered with alkaline scrub and alkaline meadow plant communities, whose existence is dependent partly on precipitation and partly on water infiltrated into the rooting zone from the shallow water table. The extent to which these plant communities are capable of adapting to and surviving fluctuations in the water table depends on physiological adaptations of the plants and on the water content, matric potential characteristics of the soils. Two methods were used to estimate soil matric potential in test sites in Owens Valley. The first was the filter-paper method, which uses water content of filter papers equilibrated to water content of soil samples taken with a hand auger. The other method of estimating soil matric potential was a modeling approach based on data from this and previous investigations. These data indicate that the base 10 logarithm of soil matric potential is a linear function of gravimetric soil water content for a particular soil. Estimates of soil water characteristic curves were made at two sites by averaging the gravimetric soil water content and soil matric potential values from multiple samples at 0.1 m depths derived by using the hand auger and filter paper method and entering these values in the soil water model. The characteristic curves then were used to estimate soil matric potential from estimates of volumetric soil water content derived from neutron-probe readings. Evaluation of the modeling technique at two study sites indicated that estimates of soil matric potential within 0.5 pF units of the soil matric potential value derived by using the filter paper method could be obtained 90 to 95% of the time in soils where water content was less than field capacity. The greatest errors occurred at depths where there was a distinct transition between soils of different textures. (Lantz-PTT)

  11. Boundary transfer matrices and boundary quantum KZ equations

    SciTech Connect

    Vlaar, Bart

    2015-07-15

    A simple relation between inhomogeneous transfer matrices and boundary quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable systems with reflecting boundary conditions, analogous to an observation by Gaudin for periodic systems. Thus, the boundary quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin’s boundary transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.

  12. 77 FR 57981 - Constitution Day and Citizenship Day, Constitution Week, 2012

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-18

    ..., Constitution Week, 2012 #0; #0; #0; Presidential Documents #0; #0; #0;#0;Federal Register / Vol. 77 , No. 181... Citizenship Day, and September 17 through September 23, 2012, as Constitution Week. I encourage Federal, State... of the United States of America the two hundred and thirty- seventh. (Presidential Sig.) [FR...

  13. 75 FR 57835 - Constitution Day and Citizenship Day, Constitution Week, 2010

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-22

    ... two hundred and thirty-fifth. (Presidential Sig.) [FR Doc. 2010-23898 Filed 9-21-10; 11:15 am] Billing... Proclamation 8562--Constitution Day and Citizenship Day, Constitution Week, 2010 Proclamation 8563--National POW/MIA Recognition Day, 2010 #0; #0; #0; Presidential Documents #0; #0; #0;#0;Federal Register /...

  14. Crushed-salt constitutive model update

    SciTech Connect

    Callahan, G.D.; Loken, M.C.; Mellegard, K.D.

    1998-01-01

    Modifications to the constitutive model used to describe the deformation of crushed salt are presented in this report. Two mechanisms--dislocation creep and grain boundary diffusional pressure solutioning--defined previously but used separately are combined to form the basis for the constitutive model governing the deformation of crushed salt. The constitutive model is generalized to represent three-dimensional states of stress. New creep consolidation tests are combined with an existing database that includes hydrostatic consolidation and shear consolidation tests conducted on Waste Isolation Pilot Plant and southeastern New Mexico salt to determine material parameters for the constitutive model. Nonlinear least-squares model fitting to data from the shear consolidation tests and a combination of the shear and hydrostatic consolidation tests produced two sets of material parameter values for the model. The change in material parameter values from test group to test group indicates the empirical nature of the model but demonstrates improvement over earlier work with the previous models. Key improvements are the ability to capture lateral strain reversal and better resolve parameter values. To demonstrate the predictive capability of the model, each parameter value set was used to predict each of the tests in the database. Based on the fitting statistics and the ability of the model to predict the test data, the model appears to capture the creep consolidation behavior of crushed salt quite well.

  15. Constitution 200: A Bicentennial Collection of Essays.

    ERIC Educational Resources Information Center

    Hepburn, Mary A., Ed.; And Others

    Constitutional essays which formed the basis of public assemblies throughout three states are compiled in this book. The first three essays consider the U.S. government principles of federalism, judicial review, and the separation of powers. Michael L. Benedict proposes that the question of ultimate sovereignty has been answered differently by…

  16. Great Constitutional Ideas: Justice, Equality, and Property.

    ERIC Educational Resources Information Center

    Starr, Isidore

    1987-01-01

    Examines the ideas of justice, equality, and property as they are represented in the Declaration of Independence, the U.S. Constitution and the Bill of Rights. Discusses how these ideas affect the way public schools operate and the lessons educators teach or don't teach about our society. Includes ideas for classroom activities. (JDH)

  17. Rapping the 27 Amendments to the Constitution

    ERIC Educational Resources Information Center

    Knaresborough, Adam

    2009-01-01

    Early in the year, the students of history and government at Mountain View High School in Stafford, Virginia, began to devise hand motions to help memorize the 27 amendments to the Constitution for government class. Three students in the school who are interested in hip hop music then suggested composing a rap song about the topic. Working with…

  18. Student Perspectives on Behaviors That Constitute Cheating

    ERIC Educational Resources Information Center

    Higbee, Jeanne L.; Schultz, Jennifer L.; Sanford, Thomas

    2011-01-01

    A previous study conducted a decade ago determined that there can be considerable disagreement--not only between students and faculty, but also among students and among faculty--regarding behaviors that constitute cheating. This article reports the results of a research study that replicated the student survey administered for the previous study,…

  19. Celebrating the Constitution: A Bicentennial Retrospective.

    ERIC Educational Resources Information Center

    Walch, Timothy G., Ed.

    1988-01-01

    This commemorative document was published to celebrate the Bicentennial of the signing of the U.S. Constitution and to pay tribute to the bicentennial celebration efforts of the U.S. National Archives and Records Administration staff. The included articles are: (1) "Introduction: A Celebration at the National Archives" (F. Burke); (2) "The Odyssey…

  20. School Choice and State Constitutions' Religion Clauses

    ERIC Educational Resources Information Center

    Komer, Richard D.

    2009-01-01

    After the U.S. Supreme Court's decision in "Zelman v. Simmons-Harris," only state religion clauses represent a potential constitutional bar to the inclusion of religious options in properly designed school choice programs. The two most significant are compelled support clauses and Blaine Amendments. Both are frequently misinterpreted by state…

  1. Censorship of Obscenity: The Developing Constitutional Standards.

    ERIC Educational Resources Information Center

    Lockhart, William B.; McClure, Robert C.

    1960-01-01

    To demonstrate that substantial protection has been given to published material dealing with sex, an analysis of the constitutional criteria governing recent Supreme Court decisions in the area of obscenity censorship is presented. It is found that the Supreme Court uses "hard core pornography" as the foundation of a "constant" concept of…

  2. James Madison and the Constitutional Convention.

    ERIC Educational Resources Information Center

    Scanlon, Thomas M.

    1987-01-01

    Part 1 of this three-part article traces James Madison's life and focuses primarily on those events that prepared him for leadership in the U.S. Constitutional Convention of 1787. It describes his early love of learning, education, and public service efforts. Part 2 chronicles Madison's devotion to study and preparation prior to the Constitutional…

  3. Children's Constitutional Rights: Interpretations and Implications.

    ERIC Educational Resources Information Center

    Sametz, Lynn; And Others

    1983-01-01

    Discusses a brief historical overview of constitutional law as it applies to children, delineated in the First, Fourth, Fifth, Sixth, Eighth, and Fourteenth Amendments. Emphasizes the need for school psychologists and educators to have an understanding of children's developing legal rights. Specific court cases are cited. (Author/JAC)

  4. A New Perspective on Teaching Constitutional Law

    ERIC Educational Resources Information Center

    Rosenblum, Robert

    1977-01-01

    The author suggests that a major failure of most law schools and traditional undergraduate constitutional law courses is that they omit an adequate analysis of the political nature of the judicial process. Political influences on a variety of court cases are discussed. (LBH)

  5. Globalization of Constitutional Law and Civil Rights.

    ERIC Educational Resources Information Center

    Weissbrodt, David

    1993-01-01

    Two issues are discussed: (1) reasons for raising global and international human rights issues in constitutional law, civil rights, and administrative law courses in United States law schools; and (2) barriers to globalization of courses and ways to overcome them. (MSE)

  6. 29 CFR 452.18 - Constitutional officers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 2 2012-07-01 2012-07-01 false Constitutional officers. 452.18 Section 452.18 Labor Regulations Relating to Labor OFFICE OF LABOR-MANAGEMENT STANDARDS, DEPARTMENT OF LABOR LABOR-MANAGEMENT STANDARDS GENERAL STATEMENT CONCERNING THE ELECTION PROVISIONS OF THE LABOR-MANAGEMENT REPORTING AND DISCLOSURE ACT OF 1959 Coverage of...

  7. Constitutive behavior of reconsolidating crushed salt

    SciTech Connect

    Callahan, G.D.; Mellegard, K.D.

    1998-02-01

    The constitutive model used to describe deformation of crushed salt is presented in this paper. Two mechanisms--dislocation creep and grain boundary diffusional pressure solutioning--are combined to form the basis for the constitutive model governing deformation of crushed salt. The constitutive model is generalized to represent three-dimensional states of stress. Recently completed creep consolidation tests are combined with an existing database that includes hydrostatic consolidation and shear consolidation tests conducted on Waste Isolation Pilot Plant (WIPP) and southeastern New Mexico salt to determine material parameters for the constitutive model. Nonlinear least-squares model fitting to data from shear consolidation tests and a combination of shear and hydrostatic tests produces two sets of material parameter values for the model. Changes in material parameter values from test group to test group indicate the empirical nature of the model but show significant improvement over earlier work. To demonstrate the predictive capability of the model, each parameter value set was used to predict each of the tests in the database. Based on fitting statistics and ability of the model to predict test data, the model appears to capture the creep consolidation behavior of crushed salt quite well.

  8. On Fluctuations of Eigenvalues of Random Band Matrices

    NASA Astrophysics Data System (ADS)

    Shcherbina, M.

    2015-10-01

    We consider the fluctuations of linear eigenvalue statistics of random band matrices whose entries have the form with i.i.d. possessing the th moment, where the function u has a finite support , so that M has only nonzero diagonals. The parameter b (called the bandwidth) is assumed to grow with n in a way such that . Without any additional assumptions on the growth of b we prove CLT for linear eigenvalue statistics for a rather wide class of test functions. Thus we improve and generalize the results of the previous papers (Jana et al., arXiv:1412.2445; Li et al. Random Matrices 2:04, 2013), where CLT was proven under the assumption . Moreover, we develop a method which allows to prove automatically the CLT for linear eigenvalue statistics of the smooth test functions for almost all classical models of random matrix theory: deformed Wigner and sample covariance matrices, sparse matrices, diluted random matrices, matrices with heavy tales etc.

  9. Binary matrices, decomposition and multiply-add architectures

    NASA Astrophysics Data System (ADS)

    Sarukhanian, Hakob; Agaian, Sos S.; Astola, Jaakko T.; Egiazarian, Karen O.

    2003-05-01

    Binary matrices or (+/-1)-matrices have found numerous applications in coding, signal processing, and communications. In this paper, a general and efficient algorithm of decomposition of binary matrices is developed. As a special case, Hadamard matrices are considered. The proposed scheme requires no zero padding of the input data. The problem of the construction of 4n-point Hadamard transform is related to the Hadamard problem: the question of existence of Hadamard matrices. (It is not proved whether for every integer n, there exists an orthogonal 4n×4n matrix with elements +/-1). The number of real operation in developed algorithms is reduced from 0(N2) to 0(Nlog2N). Comparisons revealing the efficiency of the proposed algorithms with respect to the known ones are given. In particular, it is demonstrated that, in typical applications, the proposed algorithm I s more efficient than the conventional Walsh Hadamard transform. Note that for Hadamard matrices of orders >=96 the general algorithm is more efficient than the classical Walsh-Hadamard transform whose order is a power of two. The algorithm has a simple and symmetric structure. The results of numerical examples are presented.

  10. Action recognition from video using feature covariance matrices.

    PubMed

    Guo, Kai; Ishwar, Prakash; Konrad, Janusz

    2013-06-01

    We propose a general framework for fast and accurate recognition of actions in video using empirical covariance matrices of features. A dense set of spatio-temporal feature vectors are computed from video to provide a localized description of the action, and subsequently aggregated in an empirical covariance matrix to compactly represent the action. Two supervised learning methods for action recognition are developed using feature covariance matrices. Common to both methods is the transformation of the classification problem in the closed convex cone of covariance matrices into an equivalent problem in the vector space of symmetric matrices via the matrix logarithm. The first method applies nearest-neighbor classification using a suitable Riemannian metric for covariance matrices. The second method approximates the logarithm of a query covariance matrix by a sparse linear combination of the logarithms of training covariance matrices. The action label is then determined from the sparse coefficients. Both methods achieve state-of-the-art classification performance on several datasets, and are robust to action variability, viewpoint changes, and low object resolution. The proposed framework is conceptually simple and has low storage and computational requirements making it attractive for real-time implementation. PMID:23508265

  11. Electrode including porous particles with embedded active material for use in a secondary electrochemical cell

    DOEpatents

    Vissers, Donald R.; Nelson, Paul A.; Kaun, Thomas D.; Tomczuk, Zygmunt

    1978-04-25

    Particles of carbonaceous matrices containing embedded electrode active material are prepared for vibratory loading within a porous electrically conductive substrate. In preparing the particles, active materials such as metal chalcogenides, solid alloys of alkali or alkaline earth metals along with other metals and their oxides in powdered or particulate form are blended with a thermosetting resin and particles of a volatile to form a paste mixture. The paste is heated to a temperature at which the volatile transforms into vapor to impart porosity at about the same time as the resin begins to cure into a rigid, solid structure. The solid structure is then comminuted into porous, carbonaceous particles with the embedded active material.

  12. Constitutive modeling of aluminum foam and finite element implementation for crash simulations

    NASA Astrophysics Data System (ADS)

    Bi, Jing

    In the past decades metallic foams have been increasingly used as filler materials in crashworthiness applications due to their relatively low cost and high capacity of energy absorption. Due to the destructive nature of crashes, studies on the performance of metallic foams using physical testing have been limited to examining the crushing force histories and/or folding patterns that are insufficient for crashworthiness designs. For this reason, numerical simulations, particularly nonlinear finite element (FE) analyses, play an important role in designing crashworthy foam-filled structures. An effective and numerically stable model is needed for modeling metallic foams that are porous and encounter large nonlinear deformations in crashes. In this study a new constitutive model for metallic foams is developed to overcome the deficiency of existing models in commercial FE codes such as LS-DYNA. The new constitutive model accounts for volume changes under hydrostatic compression and combines the hydrostatic pressure and von Mises stress into one yield function. The change of the compressibility of the metallic foam is handled in the constitutive model by allowing for shape changes of the yield surface in the hydrostatic pressure-von Mises stress space. The backward Euler method is adopted to integrate the constitutive equations to achieve numerical accuracy and stability. The new foam model is verified and validated by existing experimental data before used in FE simulations of crushing of foam-filled columns that have square and hexagonal cross-sections.

  13. Steady flow through porous media

    SciTech Connect

    Greenkorn, R.A.

    1981-07-01

    The movement of materials through porous media is of interest in many disciplines: in chemical engineering - adsorption, chromatography, filtration, flow in packed columns, ion exchange, reactor-engineering; in petroleum engineering - displacement of oil with gas, water and miscible solvents including surface-active agent solutions and description of reservoirs; in hydrology - movement of trace pollutants in water systems, recovery of water for drinking and irrigation, saltwater encroachment into freshwater reservoirs; in soil physics - movement of water, nutrients, and pollutants into plants; and in biophysics. This work reviews the fundamentals of steady flow through porous media. It discusses the pseudotransport coefficients permeability, capillary pressure, and dispersion and relates these coefficients to the geometry of porous media. It discusses single-fluid flow, multifluid immiscible flow, and multifluid miscible flow including the effects of heterogeneity, nonuniformity, and anisotropy of media. 104 references.

  14. Acoustic Absorption in Porous Materials

    NASA Technical Reports Server (NTRS)

    Kuczmarski, Maria A.; Johnston, James C.

    2011-01-01

    An understanding of both the areas of materials science and acoustics is necessary to successfully develop materials for acoustic absorption applications. This paper presents the basic knowledge and approaches for determining the acoustic performance of porous materials in a manner that will help materials researchers new to this area gain the understanding and skills necessary to make meaningful contributions to this field of study. Beginning with the basics and making as few assumptions as possible, this paper reviews relevant topics in the acoustic performance of porous materials, which are often used to make acoustic bulk absorbers, moving from the physics of sound wave interactions with porous materials to measurement techniques for flow resistivity, characteristic impedance, and wavenumber.

  15. 78 FR 39721 - Constitution Pipeline Company, LLC; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-02

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Constitution Pipeline Company, LLC; Notice of Application Take notice that on June 13, 2013, Constitution Pipeline Company, LLC (Constitution), having its principal place...

  16. Direct atomic absorption determination of cadmium and lead in strongly interfering matrices by double vaporization with a two-step electrothermal atomizer

    NASA Astrophysics Data System (ADS)

    Grinshtein, Ilia L.; Vilpan, Yuri A.; Saraev, Alexei V.; Vasilieva, Lubov A.

    2001-03-01

    Thermal pretreatment of a sample using double vaporization in a two-step atomizer with a purged vaporizer makes possible the direct analysis of samples with strongly interfering matrices including solids. A porous-graphite capsule or a filter inserted into the vaporizer is used for solid sample analysis. The technique was used for the direct determination of Cd and Pb in human urine, potatoes, wheat, bovine liver, milk powder, grass-cereal mixtures, caprolactam, bituminous-shale and polyvinyl chloride plastic without chemical modification or any other sample pretreatment.

  17. Towards a porous media model of the human lung

    NASA Astrophysics Data System (ADS)

    DeGroot, Christopher T.; Straatman, Anthony G.

    2012-05-01

    In this article, progress towards building a complete porous media model of the human lung is discussed. While the recent trend in computational fluid dynamics studies of airflow in the human lung has been to continually increase the size and detail of the airway tree under consideration, it is proposed in this work that simulating flow in the human lung as a coupled fluid-porous system is an effective method to simulate the flow in the whole lung. Under the proposed modeling paradigm, a truncated airway tree constitutes a fluid region which is coupled to a porous region that represents the remainder of the lung volume, containing small airways and alveoli. The first part of this work describes pore-level simulations conducted in an alveolated duct geometry, which are present in large quantities in the human lung, to determine its permeability. Next, volume-averaged simulations incorporating the results of the pore-level simulations and using a realistic lung geometry based on computed tomography images are discussed along with future directions for this work.

  18. Microscale simulation of particle deposition in porous media.

    PubMed

    Boccardo, Gianluca; Marchisio, Daniele L; Sethi, Rajandrea

    2014-03-01

    In this work several geometries, each representing a different porous medium, are considered to perform detailed computational fluid dynamics simulation for fluid flow, particle transport and deposition. Only Brownian motions and steric interception are accounted for as deposition mechanisms. Firstly pressure drop in each porous medium is analyzed in order to determine an effective grain size, by fitting the results with the Ergun law. Then grid independence is assessed. Lastly, particle transport in the system is investigated via Eulerian steady-state simulations, where particle concentration is solved for, not following explicitly particles' trajectories, but solving the corresponding advection-diffusion equation. An assumption was made in considering favorable collector-particle interactions, resulting in a "perfect sink" boundary condition for the collectors. The gathered simulation data are used to calculate the deposition efficiency due to Brownian motions and steric interception. The original Levich law for one simple circular collector is verified; subsequently porous media constituted by a packing of collectors are scrutinized. Results show that the interactions between the different collectors result in behaviors which are not in line with the theory developed by Happel and co-workers, highlighting a different dependency of the deposition efficiency on the dimensionless groups involved in the relevant correlations. PMID:24407681

  19. The stress relaxation characteristics of composite matrices etched to produce nanoscale surface features.

    PubMed

    Mirani, Rahul D; Pratt, Jonathan; Iyer, Pooja; Madihally, Sundararajan V

    2009-02-01

    Many synthetic and xenogenic natural matrices have been explored in tissue regeneration, however, they lack either mechanical strength or cell colonization characteristics found in natural tissue. Moreover natural matrices such as small intestinal submucosa (SIS) lack sample to sample homogeneity, leading to unpredictable clinical outcomes. This work explored a novel fabrication technique by blending together the useful characteristics of synthetic and natural polymers to form a composite structure by using a NaOH etching process that produces nanoscale surface features. The composite scaffold was formed by sandwiching a thin layer of PLGA between porous layers of gelatin-chitosan. The etching process increased the surface roughness of PLGA membrane, allowing easy spreading of the hydrophilic gelatin-chitosan solution on its hydrophobic surface and reducing the scaffold thickness by nearly 50% than otherwise. The viscoelastic properties of the scaffold, an area of mechanical analysis which remains largely unexplored in tissue regeneration was assessed. Stress relaxation experiments of the "ramp and hold" type performed at variable ranges of temperature (25 degrees C and 37 degrees C), loading rates (3.125% s(-1) and 12.5% s(-1)) and relaxation times (60 s, 100 s and 200 s) found stress relaxation to be sensitive to temperature and the loading rate but less dependent on the relaxation time. Stress relaxation behavior of the composite matrix was compared with SIS structures at 25 degrees C (hydrated), 3.125% s(-1) loading rate and 100 s relaxation time which showed that the synthetic matrix was found to be strain softening as compared to the strain hardening behavior exhibited by SIS. Popularly used quasi-linear viscoelastic (QLV) model to describe biomechanics of soft tissues was utilized. The QLV model predicted the loading behavior with an average error of 3%. The parameters of the QLV model predicted using nonlinear regression analysis appear to be in concurrence

  20. Metal recovery from porous materials

    DOEpatents

    Sturcken, Edward F.

    1992-01-01

    A method for recovering plutonium and other metals from materials by leaching comprising the steps of incinerating the materials to form a porous matrix as the residue of incineration, immersing the matrix into acid in a microwave-transparent pressure vessel, sealing the pressure vessel, and applying microwaves so that the temperature and the pressure in the pressure vessel increase. The acid for recovering plutonium can be a mixture of HBF.sub.4 and HNO.sub.3 and preferably the pressure is increased to at least 100 PSI and the temperature to at least 200.degree. C. The porous material can be pulverized before immersion to further increase the leach rate.

  1. Porous pseudoalloy electrode gap inserts

    SciTech Connect

    Pustogarov, A.V.; Chernyshev, L.I.; Kostornov, A.G.; Mel'nikov, G.N.

    1985-06-01

    The authors make a comparative assessment of the service characteristics of porous electrode gap inserts (EGI) made of tungsten, molybdenum, and W-Cu and Mo-Cu pseudoalloys, tested using a high pressure apparatus. Charts present the data gathered on maximum thermal flux entering the EGI wall with specific nitrogen flow rates; variation of temperature of the inner surface of the EGI wall with thermal conductivity of the material; and variation of viscous and inertia coefficients of hydraulic resistance of pseudoalloys with duration of EGI operation. The authors conclude that porous EGIs made of W-Cu and Mo-Cu pseudoalloys are characterized by the same operating performance.

  2. Crystalline Colloidal Arrays in Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Sunkara, Hari B.; Penn, B. G.; Frazier, D. O.; Ramachandran, N.

    1997-01-01

    matrices, the factors which affect the optical diffraction qualities of resulting polymer films, and methods to improve the efficiencies of solid optical filters. Before this, we also present the experimental demonstration, of controlling the optical diffraction intensities from aqueous CCA dispersions by varying the temperature, which establishes the feasibility of fabricating all-optical switching devices with nonlinear periodic array structures.

  3. Inorganic Nanoparticle Nucleation on Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Kosteleski, Adrian John

    dressing applications. PAA's ability to nucleate nanoparticles in a solid matrix was displayed. Interestingly enough PAA retains its ability to nucleate nanoparticle even when its reactive functional groups are used in the crosslinking process. Silver nanoparticle composition and size on the solid polymer matrices was controlled by varying the composition of PAA. PAA and silver nanoparticles effect on the mechanical properties of the calcium alginate hydrogels were also studied. Physically crosslinking PAA with calcium alginate gels enables the development of intricate gel structures that are decorated with nucleated silver; yielding a composite biomaterial with improved and enhanced antimicrobial properties.

  4. Porous matrix of calcium alginate/gelatin with enhanced properties as scaffold for cell culture.

    PubMed

    Cuadros, Teresa R; Erices, Alejandro A; Aguilera, José M

    2015-06-01

    Hydrophilic polysaccharides can be used to prepare porous matrices with a range of possible applications. One such application involves acting as scaffolds for cell culture. A new homogeneous and highly porous biopolymeric porous matrix (BPM) of calcium alginate/gelatin was produced by following a simple process. The key to this process was the selection of the porogen (aerated gelatin). The preparation technique comprises the following steps: incorporating the porogen into the solution of alginate (3%), molding, cross-linking the alginate in 1.41% CaCl2 (maximum gel strength; Cuadros et al., 2012. Carbohydr. Polym. 89, 1198-1206), molding, leaching and lyophilization. Cylinders of BPM were shown to have a relative density of 0.0274 ± 0.002, porosity of 97.26 ± 0.18%, an average internal pore size of 204 ± 58 µm and enhanced mechanical properties, while imbibing more than 11 times their dry weight in water. In vitro cell culture testing within BPM using mesenchymal stem cells was demonstrated by MTT assays and expression of alkaline phosphatase. The BPM provided a suitable microenvironment for seeding, adhesion, proliferation and osteogenic differentiation of cells. The preparation technique and resulting porous matrix represent potential tools for future study and further applications. PMID:25661688

  5. Molecularly imprinted porous beads for the selective removal of copper ions.

    PubMed

    Younis, M Rizwan; Bajwa, Sadia Z; Lieberzeit, Peter A; Khan, Waheed S; Mujahid, Adnan; Ihsan, Ayesha; Rehman, Asma

    2016-02-01

    In the present work, novel molecularly imprinted polymer porous beads for the selective separation of copper ions have been synthesized by combining two material-structuring techniques, namely, molecular imprinting and oil-in-water-in-oil emulsion polymerization. This method produces monodisperse spherical beads with an average diameter of ∼2-3 mm, in contrast to adsorbents produced in the traditional way of grinding and sieving. Field-emission scanning electron microscopy indicates that the beads are porous in nature with interconnected pores of about 25-50 μm. Brunner-Emmett-Teller analysis shows that the ion-imprinted beads possess a high surface area (8.05 m(2) /g), and the total pore volume is determined to be 0.00823 cm(3) /g. As a result of the highly porous nature and ion-imprinting, the beads exhibit a superior adsorption capacity (84 mg/g) towards copper than the non-imprinted material (22 mg/g). Furthermore, selectivity studies indicate that imprinted beads show splendid recognizing ability, that is, nearly fourfold greater selective binding for Cu(2+) in comparison to the other bivalent ions such as Mn(2+) , Ni(2+) , Co(2+) , and Ca(2+) . The imprinted composite beads prepared in this study possess uniform porous morphology and may open up new possibilities for the selective removal of copper ions from waste water/contaminated matrices. PMID:26632078

  6. Process of preparing tritiated porous silicon

    DOEpatents

    Tam, S.W.

    1997-02-18

    A process of preparing tritiated porous silicon is described in which porous silicon is equilibrated with a gaseous vapor containing HT/T{sub 2} gas in a diluent for a time sufficient for tritium in the gas phase to replace hydrogen present in the pore surfaces of the porous silicon. 1 fig.

  7. Phase field modeling of partially saturated deformable porous media

    NASA Astrophysics Data System (ADS)

    Sciarra, Giulio

    2016-09-01

    A poromechanical model of partially saturated deformable porous media is proposed based on a phase field approach at modeling the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the porous skeleton, depending on the porous texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field model based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field model. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged model with that one endowed with the concept of average interfacial area. The considered poromechanical model is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).

  8. Mechanism of constitution liquid film migration

    SciTech Connect

    1999-06-01

    Liquid film migration (LFM) in liquid phase sintering classically involves a large metastable liquid volume adjacent to solid, and migration occurs at an isolated solid-liquid (S-L) interface. Constitutional liquid film migration (CLFM), discovered in alloy 718, has major characteristics similar to those of LFM, except that the metastable liquid is from the constitutional liquation of precipitates on the grain boundary. The similarity between LFM and CLFM has led to the theory that coherency lattice strain responsible for LFM is also responsible for CLFM. The coherency strain hypothesis was tested in this study by evaluating whether the Hillert model of LFM would also apply for CLFM. Experimental results of CLFM in alloy 718 showed that migration velocity followed the trend predicted by the Hillert model. This indicates that the coherency strain hypothesis of LFM also applies for CLFM and that the coherency lattice strain responsible for LFM is also the driving force for CLFM.

  9. In quest of constitutional principles of "neurolaw".

    PubMed

    Pizzetti, Federico Gustavo

    2011-01-01

    The growing use of brain imaging technology and the developing of cognitive neuroscience pose unaccustomed challenges to legal systems. Until now, the fields of Law much affected are the civil and criminal law and procedure, but the constitutional dimension of "neurolaw" cannot be easily underestimated. As the capacity to investigate and to trace brain mechanisms and functional neural activities increases, it becomes urgent the recognition and definition of the unalienable rights and fundamental values in respect of this new techno-scientific power, that must be protected and safeguard at "constitutional level" of norms such as: human dignity, personal identity, authenticity and the pursuit of individual "happiness". As the same as for the law regulating research and experimentation on human genome adopted in the past years, one may also argue if the above mentioned fundamental principles of "neurolaw" must be fixed and disciplined also at European and International level. PMID:23057208

  10. Probabilistic constitutive law for damage in ligaments.

    PubMed

    Guo, Zheying; De Vita, Raffaella

    2009-11-01

    A new constitutive equation is presented to describe the damage evolution process in parallel-fibered collagenous tissues such as ligaments. The model is formulated by accounting for the fibrous structure of the tissues. The tissue's stress is defined as the average of the collagen fiber's stresses. The fibers are assumed to be undulated and straightened out at different stretches that are randomly defined according to a Weibull distribution. After becoming straight, each collagen fiber is assumed to be linear elastic. Damage is defined as a reduction in collagen fiber's stiffness and occurs at different stretches that are also randomly defined by a Weibull distribution. Due to the lack of experimental data, the predictions of the constitutive equation are analyzed by varying the values of its structural parameters. Moreover, the results are compared with the available stress-strain data in the biomechanics literature that evaluate damage produced by subfailure stretches in rat medial collateral ligaments. PMID:19665914

  11. Constitutive Modeling of Crosslinked Nanotube Materials

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Frankland, S. J. V.; Herzog, M. N.; Gates, T. S.; Fay, C. C.

    2004-01-01

    A non-linear, continuum-based constitutive model is developed for carbon nanotube materials in which bundles of aligned carbon nanotubes have varying amounts of crosslinks between the nanotubes. The model accounts for the non-linear elastic constitutive behavior of the material in terms of strain, and is developed using a thermodynamic energy approach. The model is used to examine the effect of the crosslinking on the overall mechanical properties of variations of the crosslinked carbon nanotube material with varying degrees of crosslinking. It is shown that the presence of the crosslinks has significant effects on the mechanical properties of the carbon nanotube materials. An increase in the transverse shear properties is observed when the nanotubes are crosslinked. However, this increase is accompanied by a decrease in axial mechanical properties of the nanotube material upon crosslinking.

  12. Immobilization of Trametes hirsuta laccase into poly(3,4-ethylenedioxythiophene) and polyaniline polymer-matrices

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoju; Sjöberg-Eerola, Pia; Immonen, Kirsi; Bobacka, Johan; Bergelin, Mikael

    The immobilization of Trametes hirsuta laccase (ThL) in the poly(3,4-ethylenedioxythiophene) (PEDOT) and polyaniline (PANI) matrices was carried out in order to study the catalytic effect of ThL in different biocathode structures in a biofuel cell application. By using 2,2‧-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) as a mediator compound, the immobilized ThL in both polymer matrices, exhibited catalytic activity for the reduction of oxygen into water. The amount of ThL was adjustable in the PEDOT matrix by controlling the working parameters, such as the charge density used in the electropolymerization of EDOT monomer and the ThL concentration used in the electropolymerization electrolyte. In the PEDOT biocathode structure, the utilization of porous material as the PEDOT supporting template was studied in order to improve the current density generated per unit area/volume. Reticulated vitreous carbon foam (RVC foam) was chosen as the PEDOT supporting template material and the biocathodes were manufactured by in situ entrapment of ThL into PEDOT films polymerized on the RVC foam. These biocathodes possessed a high cathodic open circuit potential and produced a large current density, reaching 1 mA cm -3 at 0.45 V when 19.5 μg ml -1 of ThL was used in the electrolyte. The performance of these biocathodes was extremely sensitive to variations in pH and the optimal working pH was around 4.2. The biocathode reserved 80%, 50%, and 30% of the catalytic activity after storage in a +4 °C buffer solution for 1 day, 1 week, and 1 month, respectively. The PANI matrix was prepared in a form of printable ink where ThL was in situ entrapped in the PANI matrix during the laccase activated polymerization of aniline using a chemical batch reactor method. Different amounts of the ThL-containing printable PANI ink were then applied on carbon paper and the performance of the ink was subsequently electrochemically characterized. In this way, not only two different polymer

  13. Unified viscoplastic constitutive equations and their applications

    NASA Technical Reports Server (NTRS)

    Lindholm, U. S.

    1987-01-01

    Unified constitutive equations for time- and temperature-dependent metallic plastic deformation have been applied in FEM simulations of forming processes; increasingly powerful computational tools and physical models are being used to numerically model complex engineering problems. Once confidence has been gained through adequate verification, these numerical models will increasingly replace experimental models. Attention is presently given to the contributions made by physical metallurgy, continuum mechanics, and computational mechanics.

  14. Freedom and choice in constitutional law.

    PubMed

    Garvey, J H

    1981-06-01

    The constitutional rights of children, the mentally ill, and other legally incompetent persons have been the subject of much litigation in the past twenty years. In this Article, Professor Garvey develops a general theory to explain the different ways in which persons of diminished capacity can be said to enjoy constitutional protections. He first notes that, of the various constitutional provisions, only one kind - freedom, which protect the right to make choices - pose serious difficulties when applied to persons of diminished capacity. He then proposes a hierarchy of ways in which we can attribute freedoms to such persons: the laissez-faire notion that all persons (including incompetents) are to be treated identically, the instrumental idea that granting freedoms to incompetents achieves extrinsic goals such as training, and the surrogate notion that persons who cannot make choices for themselves should be able to have those closest to them choose on their behalf. Professor Garvey concludes that, when these options fail and the state takes an incompetent person under its control, the state owes to the incompetent the full package of duties owed by other guardians to those under their control, including treatment in the case of the mentally ill or education in the case of children. PMID:10251939

  15. Association of Sasang Constitutional Type with Sarcopenia.

    PubMed

    Lee, Seung Ku; Yoon, Dae Wui; Choi, Kyung-Mee; Lee, Si Woo; Kim, Jong Yeol; Kim, Jin Kwan; Shin, Chol

    2015-01-01

    Sasang constitutional medicine (SCM) is a unique Korean traditional medicine that classifies human beings as four distinct types named Sasang constitutional types (SCTs), based on physiologic, physical, and psychological traits. Accumulating evidence has demonstrated that specific constitutional types are associated with chronic diseases, but no study has investigated the relationship between SCTs and sarcopenia. The aim of this study was to examine the association in a large population-based study. Data from 1,204 participants who completed questionnaires for life style, anthropometric evaluation, and biochemical analysis were analyzed. Classification of the SCTs was done using an integrated diagnostic method. Sarcopenia was defined as appendicular skeletal muscle mass/height(2) less than one standard deviation below the gender-specific normal mean of a younger group. Dual-energy X-ray absorptiometry was used to assess whole body composition. The prevalence of sarcopenia was 8.6% in the Tae-eum (TE) type, 44.7% in the So-eum (SE) type, and 20.7% in the So-yang (SY) type. Multivariate analysis revealed that the SE and SY types had 9.22 (5.06-16.81; P < 0.0001) and 2.90 (1.76-4.76; P < 0.0001) greater odds of sarcopenia compared to the TE type, respectively. Our results show that the SE and SY types are significantly associated with increased prevalence of sarcopenia. PMID:26649062

  16. Association of Sasang Constitutional Type with Sarcopenia

    PubMed Central

    Lee, Seung Ku; Yoon, Dae Wui; Choi, Kyung-Mee; Lee, Si Woo; Kim, Jong Yeol; Kim, Jin Kwan; Shin, Chol

    2015-01-01

    Sasang constitutional medicine (SCM) is a unique Korean traditional medicine that classifies human beings as four distinct types named Sasang constitutional types (SCTs), based on physiologic, physical, and psychological traits. Accumulating evidence has demonstrated that specific constitutional types are associated with chronic diseases, but no study has investigated the relationship between SCTs and sarcopenia. The aim of this study was to examine the association in a large population-based study. Data from 1,204 participants who completed questionnaires for life style, anthropometric evaluation, and biochemical analysis were analyzed. Classification of the SCTs was done using an integrated diagnostic method. Sarcopenia was defined as appendicular skeletal muscle mass/height2 less than one standard deviation below the gender-specific normal mean of a younger group. Dual-energy X-ray absorptiometry was used to assess whole body composition. The prevalence of sarcopenia was 8.6% in the Tae-eum (TE) type, 44.7% in the So-eum (SE) type, and 20.7% in the So-yang (SY) type. Multivariate analysis revealed that the SE and SY types had 9.22 (5.06–16.81; P < 0.0001) and 2.90 (1.76–4.76; P < 0.0001) greater odds of sarcopenia compared to the TE type, respectively. Our results show that the SE and SY types are significantly associated with increased prevalence of sarcopenia. PMID:26649062

  17. A constitutive theory for rigid polyurethane foam

    SciTech Connect

    Neilsen, M.K.; Krieg, R.D.; Schreyer, H.L.

    1992-12-31

    Rigid, closed-cell, polyurethane foam consists of interconnected polyurethane plates which form cells. When this foam is compressed, it exhibits an initial elastic regime which is followed by a plateau regime in which the load required to compress the foam remains nearly constant. In the plateau regime, cell walls are damaged and large permanent volume changes are generated. As additional load is applied, cell walls are compressed against neighboring cell walls, and the stiffness of the foam increases and approaches a value equal to that of solid polyurethane. When the foam is loaded in tension, the cell walls are damaged and the foam fractures. A constitutive theory for rigid polyurethane foam has been developed. This theory is based on a decomposition of the foam into two parts: a skeleton and a nonlinear elastic continuum in parallel. The skeleton accounts for the foam behavior in the elastic and plateau regimes and is described using a coupled plasticity with continuum damage theory. The nonlinear elastic continuum accounts for the lock-up of the foam due to internal gas pressure and cell wall interactions. This new constitutive theory has been implemented in both static and dynamic finite element codes. Numerical simulations performed using the new constitutive theory are presented.

  18. Constitutive modeling for isotropic materials (HOST)

    NASA Technical Reports Server (NTRS)

    Lindholm, Ulric S.; Chan, Kwai S.; Bodner, S. R.; Weber, R. M.; Walker, K. P.; Cassenti, B. N.

    1984-01-01

    The results of the first year of work on a program to validate unified constitutive models for isotropic materials utilized in high temperature regions of gas turbine engines and to demonstrate their usefulness in computing stress-strain-time-temperature histories in complex three-dimensional structural components. The unified theories combine all inelastic strain-rate components in a single term avoiding, for example, treating plasticity and creep as separate response phenomena. An extensive review of existing unified theories is given and numerical methods for integrating these stiff time-temperature-dependent constitutive equations are discussed. Two particular models, those developed by Bodner and Partom and by Walker, were selected for more detailed development and evaluation against experimental tensile, creep and cyclic strain tests on specimens of a cast nickel base alloy, B19000+Hf. Initial results comparing computed and test results for tensile and cyclic straining for temperature from ambient to 982 C and strain rates from 10(exp-7) 10(exp-3) s(exp-1) are given. Some preliminary date correlations are presented also for highly non-proportional biaxial loading which demonstrate an increase in biaxial cyclic hardening rate over uniaxial or proportional loading conditions. Initial work has begun on the implementation of both constitutive models in the MARC finite element computer code.

  19. A constitutive mechanical model for energetic materials

    SciTech Connect

    Hobbs, M.L.; Baer, M.R.; Gross, R.J.

    1994-06-01

    Cookoff modeling of energetic materials has traditionally addressed reactive heat flow with the goal of defining the onset of runaway combustion behavior. Current modeling efforts are now aimed toward predicting the violence of the event. Combined thermal, chemical, and mechanical response must be modeled, since confinement results in pressure buildup which can breach confinement or enhance gas-phase combustion rates leading to runaway combustion behavior. Thermally induced stresses can also cause gaps which inhibit heat flow. These mechanical effects must also be included in cookoff modeling. A new reactive elastic-plastic constitutive model for micromechanical response has been developed which represents a stress-strain relation for reacting materials such as explosives, propellants, pyrotechnics, or burning foams. This micromechanical model is based on bubble mechanics. A local force balance, with mass continuity constraints, forms the basis of the constitutive model requiring input of temperature and reacted fraction. This constitutive material model has been incorporated into a quasistatic mechanics code, SANTOS. To provide temperature and reacted gas fraction, the thermal-chemical solver, XCHEM, has been coupled to SANTOS. This paper summarizes the development of the micromechanical model with material property estimates for conventional energetic materials. This study shows that large pressures can arise from small reacted fractions which implies that cookoff modeling must consider the strong interaction between thermochemistry and mechanics.

  20. Implicit constitutive relations for nonlinear magnetoelastic bodies

    PubMed Central

    Bustamante, R.; Rajagopal, K. R.

    2015-01-01

    Implicit constitutive relations that characterize the response of elastic bodies have greatly enhanced the arsenal available at the disposal of the analyst working in the field of elasticity. This class of models were recently extended to describe electroelastic bodies by the present authors. In this paper, we extend the development of implicit constitutive relations to describe the behaviour of elastic bodies that respond to magnetic stimuli. The models that are developed provide a rational way to describe phenomena that have hitherto not been adequately described by the classical models that are in place. After developing implicit constitutive relations for magnetoelastic bodies undergoing large deformations, we consider the linearization of the models within the context of small displacement gradients. We then use the linearized model to describe experimentally observed phenomena which the classical linearized magnetoelastic models are incapable of doing. We also solve several boundary value problems within the context of the models that are developed: extension and shear of a slab, and radial inflation and extension of a cylinder. PMID:25792968

  1. Hydrostatic testing of porous assemblies

    NASA Technical Reports Server (NTRS)

    Bigelow, W. L.

    1968-01-01

    Pores of the material were plugged with dust particles suspended in water. The plugging material used was a standard test dust prepared as a slurry in distilled water. This technique provides a permanent high-integrity seal for porous material without affecting its physical properties, yet permitting pressure testing to verify structural adequacy.

  2. Fabrication of porous electrospun nanofibres

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Z.; Feng, Y.; Huang, Z.-M.; Ramakrishna, S.; Lim, C. T.

    2006-02-01

    Immiscible biopolymers of gelatin (Gt) and polycaprolactone (PCL) were first electrospun into a biomimicking composite fibre of Gt/PCL. Based on a phase separation study of the electrospun fibres, a leaching method was employed to generate 3D porous nanofibres by selectively removing the water soluble component of gelatin in a 37 °C aqueous solution of phosphate buffered saline. It was found that leaching treatment gave rise to a unique nanotopography containing grooves, ridges and elliptical pores on the surface as well as inside of the resultant individual nanofibres. Brunauer-Emmett-Teller (BET) area measurement indicated that the formed 3D porous fibres also brought in a pronounced increase of the surface area of fibres. The BET surface area of the porous fibres was observed to be about 2.4 times that of the precursor fibres, up to 15.84 m2 g-1 at its relatively large size of 800 nm diameter. The 3D porous fibres herein prepared could have considerable value for uses in developing highly integrated cell-scaffold tissue complexes and other industrial applications.

  3. Neural Tissue as Porous Media

    SciTech Connect

    Basser, Peter J.

    2008-12-05

    The fields of MR in Porous Media and Neuroradiology have largely developed separately during the past two decades with little appreciation of the problems, challenges and methodologies of the other. However, this trend is clearly changing and possibilities for significant cross-fertilization and synergies are now being realized.

  4. Metal recovery from porous materials

    DOEpatents

    Sturcken, E.F.

    1991-01-01

    The present invention relates to recovery of metals. More specifically, the present invention relates to the recovery of plutonium and other metals from porous materials using microwaves. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR18035 between the US Department of Energy and Westinghouse Savannah River Company.

  5. Whey drying on porous carriers

    SciTech Connect

    Mitura, E.; Kaminski, W.

    1996-05-01

    Whey is treated very often as a waste which pollutes the natural environment. Whey which is a valuable source of protein, lacrose, vitamins and mineral salts should be utilized completely. The present paper is a proposal of whey drying on porous carriers. It is proved experimentally that the proposed drying method guarantees good product quality.

  6. A coupled deformation-diffusion theory for fluid-saturated porous solids

    NASA Astrophysics Data System (ADS)

    Henann, David; Kamrin, Ken; Anand, Lallit

    2012-02-01

    Fluid-saturated porous materials are important in several familiar applications, such as the response of soils in geomechanics, food processing, pharmaceuticals, and the biomechanics of living bone tissue. An appropriate constitutive theory describing the coupling of the mechanical behavior of the porous solid with the transport of the fluid is a crucial ingredient towards understanding the material behavior in these varied applications. In this work, we formulate and numerically implement in a finite-element framework a large-deformation theory for coupled deformation-diffusion in isotropic, fluid-saturated porous solids. The theory synthesizes the classical Biot theory of linear poroelasticity and the more-recent Coussy theory of poroplasticity in a large deformation framework. In this talk, we highlight several salient features of our theory and discuss representative examples of the application of our numerical simulation capability to problems of consolidation as well as deformation localization in granular materials.

  7. An Amorphous Network Model for Capillary Flow and Dispersion in a Partially Saturated Porous Medium

    NASA Astrophysics Data System (ADS)

    Simmons, C. S.; Rockhold, M. L.

    2013-12-01

    Network models of capillary flow are commonly used to represent conduction of fluids at pore scales. Typically, a flow system is described by a regular geometric lattice of interconnected tubes. Tubes constitute the pore throats, while connection junctions (nodes) are pore bodies. Such conceptualization of the geometry, however, is questionable for the pore scale, where irregularity clearly prevails, although prior published models using a regular lattice have demonstrated successful descriptions of the flow in the bulk medium. Here a network is allowed to be amorphous, and is not subject to any particular lattice structure. Few network flow models have treated partially saturated or even multiphase conditions. The research trend is toward using capillary tubes with triangular or square cross sections that have corners and always retain some fluid by capillarity when drained. In contrast, this model uses only circular capillaries, whose filled state is controlled by a capillary pressure rule for the junctions. The rule determines which capillary participate in the flow under an imposed matric potential gradient during steady flow conditions. Poiseuille's Law and Laplace equation are used to describe flow and water retention in the capillary units of the model. A modified conjugate gradient solution for steady flow that tracks which capillary in an amorphous network contribute to fluid conduction was devised for partially saturated conditions. The model thus retains the features of classical capillary models for determining hydraulic flow properties under unsaturated conditions based on distribution of non-interacting tubes, but now accounts for flow exchange at junctions. Continuity of the flow balance at every junction is solved simultaneously. The effective water retention relationship and unsaturated permeability are evaluated for an extensive enough network to represent a small bulk sample of porous medium. The model is applied for both a hypothetically

  8. Estimating soil matric potential in Owens Valley, California

    USGS Publications Warehouse

    Sorenson, Stephen K.; Miller, Reuben F.; Welch, Michael R.; Groeneveld, David P.; Branson, Farrel A.

    1989-01-01

    Much of the floor of Owens Valley, California, is covered with alkaline scrub and alkaline meadow plant communities, whose existence is dependent partly on precipitation and partly on water infiltrated into the rooting zone from the shallow water table. The extent to which these plant communities are capable of adapting to and surviving fluctuations in the water table depends on physiological adaptations of the plants and on the water content, matric potential characteristics of the soils. Two methods were used to estimate soil matric potential in test sites in Owens Valley. The first, the filter-paper method, uses water content of filter papers equilibrated to water content of soil samples taken with a hand auger. The previously published calibration relations used to estimate soil matric potential from the water content of the filter papers were modified on the basis of current laboratory data. The other method of estimating soil matric potential was a modeling approach based on data from this and previous investigations. These data indicate that the base-10 logarithm of soil matric potential is a linear function of gravimetric soil water content for a particular soil. The slope and intercepts of this function vary with the texture and saturation capacity of the soil. Estimates of soil water characteristic curves were made at two sites by averaging the gravimetric soil water content and soil matric potential values from multiple samples at 0.1-m depth intervals derived by using the hand auger and filter-paper method and entering these values in the soil water model. The characteristic curves then were used to estimate soil matric potential from estimates of volumetric soil water content derived from neutron-probe readings. Evaluation of the modeling technique at two study sites indicated that estimates of soil matric potential within 0.5 pF units of the soil matric potential value derived by using the filter-paper method could be obtained 90 to 95 percent of the

  9. Randomized Algorithms for Matrices and Data

    NASA Astrophysics Data System (ADS)

    Mahoney, Michael W.

    2012-03-01

    This chapter reviews recent work on randomized matrix algorithms. By “randomized matrix algorithms,” we refer to a class of recently developed random sampling and random projection algorithms for ubiquitous linear algebra problems such as least-squares (LS) regression and low-rank matrix approximation. These developments have been driven by applications in large-scale data analysis—applications which place very different demands on matrices than traditional scientific computing applications. Thus, in this review, we will focus on highlighting the simplicity and generality of several core ideas that underlie the usefulness of these randomized algorithms in scientific applications such as genetics (where these algorithms have already been applied) and astronomy (where, hopefully, in part due to this review they will soon be applied). The work we will review here had its origins within theoretical computer science (TCS). An important feature in the use of randomized algorithms in TCS more generally is that one must identify and then algorithmically deal with relevant “nonuniformity structure” in the data. For the randomized matrix algorithms to be reviewed here and that have proven useful recently in numerical linear algebra (NLA) and large-scale data analysis applications, the relevant nonuniformity structure is defined by the so-called statistical leverage scores. Defined more precisely below, these leverage scores are basically the diagonal elements of the projection matrix onto the dominant part of the spectrum of the input matrix. As such, they have a long history in statistical data analysis, where they have been used for outlier detection in regression diagnostics. More generally, these scores often have a very natural interpretation in terms of the data and processes generating the data. For example, they can be interpreted in terms of the leverage or influence that a given data point has on, say, the best low-rank matrix approximation; and this

  10. Mechanisms of drug release in citrate buffered HPMC matrices.

    PubMed

    Pygall, Samuel R; Kujawinski, Sarah; Timmins, Peter; Melia, Colin D

    2009-03-31

    Few studies report the effects of alkalizing buffers in HPMC matrices. These agents are incorporated to provide micro-environmental buffering, protection of acid-labile ingredients, or pH-independent release of weak acid drugs. In this study, the influence of sodium citrate on the release kinetics, gel layer formation, internal gel pH and drug release mechanism was investigated in HPMC 2910 and 2208 (Methocel E4M and K4M) matrices containing 10% felbinac 39% HPMC, dextrose and sodium citrate. Matrix dissolution at pH 1.2 and pH 7.5 resulted in complex release profiles. HPMC 2910 matrices exhibited biphasic release, with citrate increasing the immediate release phase (<60min) and reducing the extended release. HPMC 2208 matrices were accelerated, but without the loss of extended release characteristics. Studies of early gel layer formation suggested gel barrier disruption and enhanced liquid penetration. pH modification of the gel layer was transitory (<2h) and corresponded temporally with the immediate release phase. Results suggest that in HPMC 2910 matrices, high initial citrate concentrations within the gel layer suppress particle swelling, interfere with diffusion barrier integrity, but are lost rapidly whereupon drug solubility reduces and the diffusion barrier recovers. These Hofmeister or osmotic-mediated effects are better resisted by the less methoxylated HPMC 2208. PMID:19100822

  11. On pseudo-stochastic matrices and pseudo-positive maps

    NASA Astrophysics Data System (ADS)

    Chruściński, D.; Man'ko, V. I.; Marmo, G.; Ventriglia, F.

    2015-11-01

    Stochastic matrices and positive maps in matrix algebras have proved to be very important tools for analysing classical and quantum systems. In particular they represent a natural set of transformations for classical and quantum states, respectively. Here we introduce the notion of pseudo-stochastic matrices and consider their semigroup property. Unlike stochastic matrices, pseudo-stochastic matrices are permitted to have matrix elements which are negative while respecting the requirement that the sum of the elements of each column is one. They also allow for convex combinations, and carry a Lie group structure which permits the introduction of Lie algebra generators. The quantum analog of a pseudo-stochastic matrix exists and is called a pseudo-positive map. They have the property of transforming a subset of quantum states (characterized by maximal purity or minimal von Neumann entropy requirements) into quantum states. Examples of qubit dynamics connected with ‘diamond’ sets of stochastic matrices and pseudo-positive maps are dealt with.

  12. Efficient computer algebra algorithms for polynomial matrices in control design

    NASA Technical Reports Server (NTRS)

    Baras, J. S.; Macenany, D. C.; Munach, R.

    1989-01-01

    The theory of polynomial matrices plays a key role in the design and analysis of multi-input multi-output control and communications systems using frequency domain methods. Examples include coprime factorizations of transfer functions, cannonical realizations from matrix fraction descriptions, and the transfer function design of feedback compensators. Typically, such problems abstract in a natural way to the need to solve systems of Diophantine equations or systems of linear equations over polynomials. These and other problems involving polynomial matrices can in turn be reduced to polynomial matrix triangularization procedures, a result which is not surprising given the importance of matrix triangularization techniques in numerical linear algebra. Matrices with entries from a field and Gaussian elimination play a fundamental role in understanding the triangularization process. In the case of polynomial matrices, matrices with entries from a ring for which Gaussian elimination is not defined and triangularization is accomplished by what is quite properly called Euclidean elimination. Unfortunately, the numerical stability and sensitivity issues which accompany floating point approaches to Euclidean elimination are not very well understood. New algorithms are presented which circumvent entirely such numerical issues through the use of exact, symbolic methods in computer algebra. The use of such error-free algorithms guarantees that the results are accurate to within the precision of the model data--the best that can be hoped for. Care must be taken in the design of such algorithms due to the phenomenon of intermediate expressions swell.

  13. 29 CFR 402.1 - Labor organization constitution and bylaws.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 2 2010-07-01 2010-07-01 false Labor organization constitution and bylaws. 402.1 Section... constitution and bylaws. Every labor organization shall adopt a constitution and bylaws consistent with the... a constitution and bylaws which it has previously adopted and under which it is operating when...

  14. Power: Constitutional Update. Bar/School Partnership Programs Series.

    ERIC Educational Resources Information Center

    American Bar Association, Chicago, IL. Special Committee on Youth Education for Citizenship.

    The fourth in a special series of handbooks dealing with constitutional themes, this document looks at power in the context of the U.S. Constitution. "The Constitution's Prescription for Freedom" (L. Peach) examines the separation of powers provided for in the Constitution. "The Concept of Power" (C. Roach) is a series of strategies, some using…

  15. The Law of the Constitution: A Bicentennial Lecture.

    ERIC Educational Resources Information Center

    Meese, Edwin, III

    This paper discusses the distinction between the Constitution and constitutional law. The Constitution is the fundamental law of the United States. It creates the institutions of government, enumerates the powers of these institutions, and delineates areas government may not enter. The Constitution is the instrument by which the consent of the…

  16. Search, Seizure, and Privacy. Exploring the Constitution Series.

    ERIC Educational Resources Information Center

    McWhirter, Darien A., Ed.

    This book, part of the "Exploring the Constitution Series," provides a basic introduction to important areas of constitutional law. Each volume contains a general introduction to a particular constitutional issue combined with excerpts from significant Supreme Court decisions in that area. The text of the Constitution, a chronological listing of…

  17. Porous silicon carbide (SIC) semiconductor device

    NASA Technical Reports Server (NTRS)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1996-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  18. Combined Evaporation and Salt Precipitation in Porous Media

    NASA Astrophysics Data System (ADS)

    Weisbrod, N.; Dragila, M. I.; Nachshon, U.; Or, D.; Shaharani, E.; Grader, A.

    2012-12-01

    The vadose zone pore water contains dissolved salts and minerals; therefore, evaporation results in high rates of salt accumulation that may change the physical and chemical properties of the porous media. Here, a series of experiments, together with a mathematical model, are presented to shed new light on these processes. Experiments included: (1) long-term column evaporation experiments to quantify changes in evaporation rates due to salt precipitation; (2) CT scans of evaporated porous media samples saturated with salt solutions, to observe salt precipitation from micro to macro scales; and (3) Infrared thermography analysis to quantify evaporation rates from porous media surfaces for homogeneous and heterogeneous conditions and constant water table, in the presence of salt precipitation. As expected, the majority of salt crystallization occurs in the upper parts of the matrix, near the evaporation front. For heterogeneous porous matrices, salt precipitation will occur mainly in the fine pore regions as preferential evaporation takes place in these locations. In addition, it was found that the precipitated NaCl salt crust diffusion coefficient for water vapor is one to two orders of magnitude lower than the vapor diffusion coefficient in free air, depending on environmental conditions and salt crystallization rates. Three new stages of evaporation were defined for saline solutions: SS1, SS2 and SS3. SS1 exhibits a low and gradual decrease in the evaporation rate due to osmotic pressure. During SS2, the evaporation rate falls progressively due to salt precipitation; SS3 is characterized by a constant low evaporation rate and determined by the diffusion rate of water vapor through the precipitated salt layer. Even though phenomenologically similar to the classical evaporation stages of pure water, these stages correspond to different mechanisms and the transition between stages can occur regardless the hydraulic conditions. As well, it was shown that matrix

  19. Modified fibrin hydrogel matrices: both, 3D-scaffolds and local and controlled release systems to stimulate angiogenesis.

    PubMed

    Hall, Heike

    2007-01-01

    Sufficient blood perfusion is essential for all tissues to guarantee nutrient- and gas exchange. As many diseases are induced by the reduction of blood perfusion such that these tissues gradually loose their ability to function properly, therapeutic angiogenesis aims to increase blood flow in ischemic tissues by stimulating the patient's endogenous capacity to develop new blood vessels. These studies include application of angiogenesis stimulating (growth) factors and adhesion sequences as well as local gene therapy. One approach is to rationally design 3D-fibrin hydrogel matrices that provide specific adhesion sequences such as a receptor for alpha v beta 3-integrin expressed on angiogenic endothelial cells and that, in addition, are able to store and release angiogenic growth factors such as VEGF-A(165) and bFGF that target cell type-specific responses. Moreover, these matrices can be modified to release complexed plasmid DNA that transfect surrounding cells and improve angiogenesis. During wound healing, cells infiltrate into the scaffold and degrade it, thereby releasing entrapped growth factors or complexed plasmid DNA, and with the speed of tissue regeneration the scaffold is completely removed when tissue healing is achieved. The long-term aim is to develop biomimetic 3D-matrices for applications in a biomaterials context that can be applied directly at the site of injury by minimal invasive surgery. 3D-fibrin matrices constitute a scaffold and release system for single or combined therapeutic biomolecules and may therefore be able to contribute to the patients' endogenous healing response resulting in the functional recovery of a diseased tissue or organ. PMID:18220797

  20. Large N matrices from a nonlocal spin system

    NASA Astrophysics Data System (ADS)

    Anninos, Dionysios; Hartnoll, Sean A.; Huijse, Liza; Martin, Victoria L.

    2015-10-01

    Large N matrices underpin the best understood models of emergent spacetime. We suggest that large N matrices can themselves be emergent from simple quantum mechanical spin models with finite dimensional Hilbert spaces. We exhibit the emergence of large N matrices in a nonlocal statistical physics model of order N2 Ising spins. The spin partition function is shown to admit a large N saddle described by a matrix integral, which we solve. The matrix saddle is dominant at high temperatures, metastable at intermediate temperatures and ceases to exist below a critical order one temperature. The matrix saddle is disordered in a sense we make precise and competes with ordered low energy states. We verify our analytic results by Monte Carlo simulation of the spin system.

  1. Nano-Fiber Reinforced Enhancements in Composite Polymer Matrices

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2009-01-01

    Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional fiber volume ratios of 0.3 and 0.5 to obtain the composite properties. Results show that nano-fiber enhanced matrices of higher than 0.3 nano-fiber volume ratio are degrading the composite properties.

  2. Stable viscosity matrices for systems of conservation laws

    NASA Astrophysics Data System (ADS)

    Majda, Andrew; Pego, Robert L.

    A natural class of appropriate viscosity matrices for strictly hyperbolic systems of conservation laws in one space dimension, u1 + f( u) x = 0, uɛRm, is studied. These matrices are admissible in the sense that small-amplitude shock wave solutions of the hyperbolic system are shown to be limits of smooth traveling wave solutions of the parabolic system ut + f( u) x = v( Dux) x as ifv → 0 if D is in this class. The class is determined by a linearized stability requirement: The Cauchy problem for the equation u1 + f'( u0) ux = vDuxx should be well posed in L2 uniformly in v as v → 0. Previous examples of inadmissible viscosity matrices are accounted for through violation of the stability criterion.

  3. Parikh matrices of words under a generalized Thue morphism

    NASA Astrophysics Data System (ADS)

    Subramanian, K. G.; Isawasan, Pradeep; Venkat, Ibrahim; Khader, Ahamad Tajudin

    2013-10-01

    Parikh matrix of a word w, which is a sequence of symbols from an alphabet, was introduced by Mateescu et al. (2001) to count certain subwords in the word w. Subsequently, several investigations on various properties of Parikh matrices have been done. Parikh matrices of words that involve certain weak ratio-property are investigated by Subramanian et al (2009). On the other hand a morphism f is a mapping on words u,v whose images f(u), f(v) are also words with the property that f(uv) = f(u)f(v). Thue morphism on a binary alphabet is a special kind of morphism. Here we consider a generalization of Thue morphism, introduced by Seebold (2003) but restricting it to three symbols. We obtain certain properties of images of binary words under this generalized Thue morphism and also of their Parikh matrices, in the context of the weak ratio-property.

  4. Arrowheaded enhanced multivariance products representation for matrices (AEMPRM): Specifically focusing on infinite matrices and converting arrowheadedness to tridiagonality

    NASA Astrophysics Data System (ADS)

    Özdemir, Gizem; Demiralp, Metin

    2015-12-01

    In this work, Enhanced Multivariance Products Representation (EMPR) approach which is a Demiralp-and-his- group extension to the Sobol's High Dimensional Model Representation (HDMR) has been used as the basic tool. Their discrete form have also been developed and used in practice by Demiralp and his group in addition to some other authors for the decomposition of the arrays like vectors, matrices, or multiway arrays. This work specifically focuses on the decomposition of infinite matrices involving denumerable infinitely many rows and columns. To this end the target matrix is first decomposed to the sum of certain outer products and then each outer product is treated by Tridiagonal Matrix Enhanced Multivariance Products Representation (TMEMPR) which has been developed by Demiralp and his group. The result is a three-matrix- factor-product whose kernel (the middle factor) is an arrowheaded matrix while the pre and post factors are invertable matrices decomposed of the support vectors of TMEMPR. This new method is called as Arrowheaded Enhanced Multivariance Products Representation for Matrices. The general purpose is approximation of denumerably infinite matrices with the new method.

  5. Aptamer-functionalized porous phospholipid nanoshells for direct measurement of Hg(2+) in urine.

    PubMed

    Li, Zhen; Muhandiramlage, Thusitha P; Keogh, John P; Hall, Henry K; Aspinwall, Craig A

    2015-01-01

    A porous phospholipid nanoshell (PPN) sensor functionalized with a specific aptamer sensor agent was prepared for rapid detection of Hg(2+) in human urine with minimal sample preparation. Aptamer sensors provide an important class of optical transducers that can be readily and reproducibly synthesized. A key limitation of aptamer sensors, and many other optical sensors, is the potential of biofouling or biodegradation when used in complex biological matrices such as serum or urine, particularly when high levels of nucleases are present. We prepared Hg(2+)-responsive, PPN-encapsulated aptamer sensors that overcome these limitations. PPNs provide a protective barrier to encapsulate the aptamer sensor in an aqueous environment free of diffusional restrictions encountered with many polymer nanomaterials. The unique porous properties of the PPN membrane enable ready and rapid transfer of small molecular weight ions and molecules into the sensor interior while minimizing the macromolecular interactions between the transducer and degradants or interferents in the exterior milieu. Using Hg(2+)-responsive, PPN-encapsulated aptamer sensors, we were able to detect sub-100 ppb (chronic threshold limit from urine test) Hg(2+) in human urine with no sample preparation, whereas free aptamer sensors yielded inaccurate results due to interferences from the matrix. The PPN architecture provides a new platform for construction of aptamer-functionalized sensors that target low molecular weight species in complex matrices, beyond the Hg(2+) demonstrated here. PMID:25326888

  6. Image informatics for studying signal transduction in cells interacting with 3D matrices

    NASA Astrophysics Data System (ADS)

    Tzeranis, Dimitrios S.; Guo, Jin; Chen, Chengpin; Yannas, Ioannis V.; Wei, Xunbin; So, Peter T. C.

    2014-03-01

    Cells sense and respond to chemical stimuli on their environment via signal transduction pathways, complex networks of proteins whose interactions transmit chemical information. This work describes an implementation of image informatics, imaging-based methodologies for studying signal transduction networks. The methodology developed focuses on studying signal transduction networks in cells that interact with 3D matrices. It utilizes shRNA-based knock down of network components, 3D high-content imaging of cells inside the matrix by spectral multi-photon microscopy, and single-cell quantification using features that describe both cell morphology and cell-matrix adhesion pattern. The methodology is applied in a pilot study of TGFβ signaling via the SMAD pathway in fibroblasts cultured inside porous collagen-GAG scaffolds, biomaterials similar to the ones used clinically to induce skin regeneration. Preliminary results suggest that knocking down all rSMAD components affects fibroblast response to TGFβ1 and TGFβ3 isoforms in different ways, and suggest a potential role for SMAD1 and SMAD5 in regulating TGFβ isoform response. These preliminary results need to be verified with proteomic results that can provide solid evidence about the particular role of individual components of the SMAD pathway.

  7. Design of Lewis-acid centres in zeolitic matrices for the conversion of renewables.

    PubMed

    Dapsens, Pierre Y; Mondelli, Cecilia; Pérez-Ramírez, Javier

    2015-10-21

    The catalytic conversion of renewable feedstocks into chemicals is pursued as a means to sustainably fulfil future societal needs. Due to the oxygen-rich nature of bio-derived substrates, isomerisation, transfer-hydrogenation and retro-aldol reactions have emerged as relevant transformations to produce commodity chemicals and polymer building blocks. In this context, porous materials containing Lewis-acid metals (e.g., Al, Ga, Sn, Ti, Zr) play an important role. Among these, tin-containing zeolites have demonstrated superior catalytic properties which have mainly been attributed to their hydrophobicity and crystallinity. This review evaluates the versatility and the scalability of bottom-up and top-down approaches to introduce Lewis-acid functionalities in zeolitic matrices. A precise characterisation is shown to be crucial to determine the structure, acidity and environment of the sites introduced. In this regard, we highlight the limitations of conventional techniques and the advantages of analytical and modelling tools recently applied to gain an improved understanding of these solids. Thereafter, property-performance relations and important aspects for the industrial amenability of new synthetic routes are exemplified through case studies. Finally, we put forward the need for gathering deeper knowledge of the site location, surface properties and stability to aid the design of next-generation Lewis-acid catalysts. PMID:25917850

  8. Constitutional and thermal defects in nickel aluminides

    SciTech Connect

    Korzhavyi, P.A.; Abrikosov, I.A.; Johansson, B.

    1999-07-01

    The formation energies of intrinsic point defects and the interaction energies of possible defect pairs in NiAl are calculated from first principles within an order-N, locally self-consistent Green's function method in conjunction with the multipole electrostatic corrections to the atomic sphere approximation. The theory correctly reproduces the ground-state properties of the off-stoichiometric NiAl alloys. The constitutional defects (antisite Ni atoms in Ni-rich and Ni vacancies in Al-rich NiAl) are shown to form ordered structures in the ground state, in which the defects of the same kind tend to avoid each other at the shortest separation distance on their sublattice. A mean-field theory is applied to calculate the equilibrium concentrations of thermal defects. The statistics of thermal defects is interpreted in terms of dominant composition-conserving complex defects which are shown to be triple defects in Ni-rich and nearly stoichiometric NiAl. In the Al-rich region a novel thermal excitation dominates where two constitutional Ni vacancies are replaced by one antisite Al atom. The number of vacancies, as well as the total number of point defects decrease with temperature in Al-rich NiAl. The boundary between the two regions is treated analytically. The vacancy concentration exhibits a minimum in its temperature dependence at the boundary. Similar analysis is applied to study constitutional and thermal defects in Ni{sub 3}Al as a function of concentration is in excellent agreement with recent experimental data.

  9. Commutative law for products of infinitely large isotropic random matrices.

    PubMed

    Burda, Zdzislaw; Livan, Giacomo; Swiech, Artur

    2013-08-01

    Ensembles of isotropic random matrices are defined by the invariance of the probability measure under the left (and right) multiplication by an arbitrary unitary matrix. We show that the multiplication of large isotropic random matrices is spectrally commutative and self-averaging in the limit of infinite matrix size N→∞. The notion of spectral commutativity means that the eigenvalue density of a product ABC... of such matrices is independent of the order of matrix multiplication, for example, the matrix ABCD has the same eigenvalue density as ADCB. In turn, the notion of self-averaging means that the product of n independent but identically distributed random matrices, which we symbolically denote by AAA..., has the same eigenvalue density as the corresponding power A(n) of a single matrix drawn from the underlying matrix ensemble. For example, the eigenvalue density of ABCCABC is the same as that of A(2)B(2)C(3). We also discuss the singular behavior of the eigenvalue and singular value densities of isotropic matrices and their products for small eigenvalues λ→0. We show that the singularities at the origin of the eigenvalue density and of the singular value density are in one-to-one correspondence in the limit N→∞: The eigenvalue density of an isotropic random matrix has a power-law singularity at the origin ~|λ|(-s) with a power sε(0,2) when and only when the density of its singular values has a power-law singularity ~λ(-σ) with a power σ=s/(4-s). These results are obtained analytically in the limit N→∞. We supplement these results with numerical simulations for large but finite N and discuss finite-size effects for the most common ensembles of isotropic random matrices. PMID:24032775

  10. Universal microscopic correlation functions for products of truncated unitary matrices

    NASA Astrophysics Data System (ADS)

    Akemann, Gernot; Burda, Zdzislaw; Kieburg, Mario; Nagao, Taro

    2014-06-01

    We investigate the spectral properties of the product of M complex non-Hermitian random matrices that are obtained by removing L rows and columns of larger unitary random matrices uniformly distributed on the group U(N + L). Such matrices are called truncated unitary matrices or random contractions. We first derive the joint probability distribution for the complex eigenvalues of the product matrix for fixed N, L, and M, given by a standard determinantal point process in the complex plane. The weight however is non-standard and can be expressed in terms of the Meijer G-function. The explicit knowledge of all eigenvalue correlation functions and the corresponding kernel allows us to take various large N (and L) limits at fixed M. At strong non-unitarity, with L/N finite, the eigenvalues condense on a domain inside the unit circle. At the edge and in the bulk we find the same universal microscopic kernel as for a single complex non-Hermitian matrix from the Ginibre ensemble. At the origin we find the same new universality classes labeled by M as for the product of M matrices from the Ginibre ensemble. Keeping a fixed size of truncation, L, when N goes to infinity leads to weak non-unitarity, with most eigenvalues on the unit circle as for unitary matrices. Here we find a new microscopic edge kernel that generalizes the known results for M = 1. We briefly comment on the case when each product matrix results from a truncation of different size Lj.

  11. Constitutive modeling for isotropic materials (HOST)

    NASA Technical Reports Server (NTRS)

    Chan, Kwai S.; Lindholm, Ulric S.; Bodner, S. R.; Hill, Jeff T.; Weber, R. M.; Meyer, T. G.

    1986-01-01

    The results of the third year of work on a program which is part of the NASA Hot Section Technology program (HOST) are presented. The goals of this program are: (1) the development of unified constitutive models for rate dependent isotropic materials; and (2) the demonstration of the use of unified models in structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are those of Bodner-Partom and of Walker. A test procedure was developed for assisting the generation of a data base for the Bodner-Partom model using a relatively small number of specimens. This test procedure involved performing a tensile test at a temperature of interest that involves a succession of strain-rate changes. The results for B1900+Hf indicate that material constants related to hardening and thermal recovery can be obtained on the basis of such a procedure. Strain aging, thermal recovery, and unexpected material variations, however, preluded an accurate determination of the strain-rate sensitivity parameter is this exercise. The effects of casting grain size on the constitutive behavior of B1900+Hf were studied and no particular grain size effect was observed. A systematic procedure was also developed for determining the material constants in the Bodner-Partom model. Both the new test procedure and the method for determining material constants were applied to the alternate material, Mar-M247 . Test data including tensile, creep, cyclic and nonproportional biaxial (tension/torsion) loading were collected. Good correlations were obtained between the Bodner-Partom model and experiments. A literature survey was conducted to assess the effects of thermal history on the constitutive behavior of metals. Thermal history effects are expected to be present at temperature regimes where strain aging and change of microstructure are important. Possible modifications to the Bodner-Partom model to account for these effects are outlined

  12. Identification of constitutive parameters for fractional viscoelasticity

    NASA Astrophysics Data System (ADS)

    Xiao, Zhao; Haitian, Yang; Yiqian, He

    2014-01-01

    This paper develops a numerical model to identify constitutive parameters in the fractional viscoelastic field. An explicit semi-analytical numerical model and a finite difference (FD) method based numerical model are derived for solving the direct homogenous and regionally inhomogeneous fractional viscoelastic problems, respectively. A continuous ant colony optimization (ACO) algorithm is employed to solve the inverse problem of identification. The feasibility of the proposed approach is illustrated via the numerical verification of a two-dimensional identification problem formulated by the fractional Kelvin-Voigt model, and the noisy data and regional inhomogeneity etc. are taken into account.

  13. Constitutive equations of ageing polymeric materials

    NASA Technical Reports Server (NTRS)

    Peng, S. T. J.

    1985-01-01

    The constitutive equation for the relaxation behavior of time-dependent, chemically unstable materials developed by Valanis and Peng (1983), which used the irreversible thermodynamics of internal variables in Eyring's absolute reaction theory and yielded a theoretical expression for the effect of chemical crosslink density on the relaxation rate, is presently applied to the creep behavior of a network polymer which is undergoing a scission process. In particular, two equations are derived which may for the first time show the relations between mechanical models and internal variables in the creep expressions, using a three-element model with a Maxwell element.

  14. Civil and Constitutional Rights of Adjudicated Youth.

    PubMed

    Landess, Jacqueline

    2016-01-01

    Mental health clinicians serving child and adolescent patients are frequently asked to evaluate youth who have been arrested for various offenses or who are otherwise involved with the juvenile justice system. To help orient clinicians and other stakeholders involved with such cases, this article describes the evolution of the juvenile justice system and summarizes the history and current status of the civil and constitutional rights of youth involved in the adjudicatory process. This article also points out key areas in which due process rights are still evolving, particularly in the case of status offenders. PMID:26593115

  15. Evaluation of constitutive models for crushed salt

    SciTech Connect

    Callahan, G.D.; Loken, M.C. [RE Hurtado, L.D.; Hansen, F.D.

    1996-05-01

    Three constitutive models are recommended as candidates for describing the deformation of crushed salt. These models are generalized to three-dimensional states of stress to include the effects of mean and deviatoric stress and modified to include effects of temperature, grain size, and moisture content. A database including hydrostatic consolidation and shear consolidation tests conducted on Waste Isolation Pilot Plant (WIPP) and southeastern New Mexico salt is used to determine material parameters for the models. To evaluate the capability of the models, parameter values obtained from fitting the complete database are used to predict the individual tests. Finite element calculations of a WIPP shaft with emplaced crushed salt demonstrate the model predictions.

  16. Numerically abnormal chromosome constitutions in humans

    SciTech Connect

    1993-12-31

    Chapter 24, discusses numerically abnormal chromosome constitutions in humans. This involves abnormalities of human chromosome number, including polyploidy (when the number of sets of chromosomes increases) and aneuploidy (when the number of individual normal chromosomes changes). Chapter sections discuss the following chromosomal abnormalities: human triploids, imprinting and uniparental disomy, human tetraploids, hydatidiform moles, anomalies caused by chromosomal imbalance, 13 trisomy (D{sub 1} trisomy, Patau syndrome), 21 trisomy (Down syndrome), 18 trisomy syndrome (Edwards syndrome), other autosomal aneuploidy syndromes, and spontaneous abortions. The chapter concludes with remarks on the nonrandom participation of chromosomes in trisomy. 69 refs., 3 figs., 4 tabs.

  17. We the People: Indiana and the United States Constitution. Lectures in Observance of the Bicentennial of the Constitution.

    ERIC Educational Resources Information Center

    Furlong, Partick J.; And Others

    These lectures, presented in observance of the U.S. Constitution bicentennial celebration, consider selected constitutionally significant law cases that occurred in Indiana. These cases are representative of U.S. constitutional development and of the relationship of Indiana to the U.S. Constitution. Patrick Furlong, in "The South Bend Fugitive…

  18. SAXS study on myoglobin embedded in amorphous saccharide matrices.

    PubMed

    Giuffrida, S; Panzica, M; Giordano, F M; Longo, A

    2011-09-01

    We report on Small Angle X-ray Scattering (SAXS) measurements performed on samples of carboxy-myoglobin and met-myoglobin embedded in low hydrated matrices of four different saccharides (trehalose, sucrose, maltose and lactose). Results confirm the already reported occurrence of inhomogeneities, which are not peculiar of trehalose samples, but appear also in maltose and lactose, and in some cases also sucrose, being dependent on the sample hydration and on the presence of sodium dithionite. This behaviour confirms our previous interpretation about the nature of the inhomogeneities, and prompt it as a possible general behaviour for highly concentrated sugar matrices. PMID:21938613

  19. Computation of Dioptric and Magnification Matrices in Ophthalmic Lenses

    NASA Astrophysics Data System (ADS)

    Barbero, S.

    2014-06-01

    The diopter power and magnification matrices characterize the first-order properties of ophthalmic lenses for different gaze directions. Therefore an efficient method to compute them is highly valuable in ophthalmic lens design and optical performance simulations. I present a novel method to numerically compute these matrices in ophthalmic lenses comprising any set of arbitrary surfaces. The method is based on computing one base ray, along the gaze direction, and two rays close to it. These two rays are obtained varying a small parameter that indicates their separation from the base ray. The method was validated comparing the results with a single refractive surface where exact solutions are directly obtained.

  20. Random reverse-cyclic matrices and screened harmonic oscillator.

    PubMed

    Srivastava, Shashi C L; Jain, Sudhir R

    2012-04-01

    We have calculated the joint probability distribution function for random reverse-cyclic matrices and shown that it is related to an N-body exactly solvable model. We refer to this well-known model potential as a screened harmonic oscillator. The connection enables us to obtain all the correlations among the particle positions moving in a screened harmonic potential. The density of nontrivial eigenvalues of this ensemble is found to be of the Wigner form and admits a hole at the origin, in contrast to the semicircle law of the Gaussian orthogonal ensemble of random matrices. The spacing distributions assume different forms ranging from Gaussian-like to Wigner. PMID:22680453

  1. Synthesis of stiffness and mass matrices from experimental vibration modes.

    NASA Technical Reports Server (NTRS)

    Ross, R. G., Jr.

    1971-01-01

    With highly complex structures, it is sometimes desirable to derive a dynamic model of the system from experimental vibration data. This paper presents algorithms for synthesizing the mass and stiffness matrices from experimentally derived modal data in a way which preserves the physical significance of the individual mass and stiffness elements. The synthesizing procedures allow for the incorporation of other mass and stiffness data, whether empirical or based on the analyst's insight. The mass and stiffness matrices are derived for a cantilever beam example and are compared with those obtained using earlier techniques.

  2. Derivation of mass and stiffness matrices from dynamic test data.

    NASA Technical Reports Server (NTRS)

    Thoren, A. R.

    1972-01-01

    A technique is described by which orthonormal modal vectors, computed from dynamic test response data, are used to derive mass, stiffness, and damping matrices for a discrete model of the distributed elastic system. Matrices thus computed from subsystems tests may be readily incorporated into larger system models. The method has been applied to a test of the Saturn V S-II stage LOX tank-engine support system. The dynamic responses of the discrete model are shown to correlate well with test data throughout the frequency range tested.

  3. Model updating based on sensitivities of system matrices

    NASA Technical Reports Server (NTRS)

    Huang, Hsin-Hsen; Craig, Roy R., Jr.

    1993-01-01

    A new approach, which allows the physical parameters to be adjusted and preserves the structural connectivity condition, is developed in this paper. This approach is based on the sensitivities of the mass and stiffness matrices with respect to physical parameters in an attempt to use test data to correct the analytical model. The analytical mass and stiffness matrices can be corrected simultaneously. The modal data of the updated model dramatically converges to that of the test model. A numerical example is presented to illustrate the feasibility of this approach. Comparisons with the other methods are also given.

  4. Wavelet Multifractal Detrended Fluctuation Analysis of Encryption and Decryption Matrices

    NASA Astrophysics Data System (ADS)

    Murguía, J. S.; Mejía Carlos, M.; Vargas-Olmos, C.; Ramírez-Torres, M. T.; Rosu, H. C.

    2013-09-01

    In this paper, we study in detail the multifractal features of the main matrices of an encryption system based on a rule-90 cellular automaton. For this purpose, we consider the scaling method known as the wavelet transform multifractal detrended fluctuation analysis (WT-MFDFA). In addition, we analyze the multifractal structure of the matrices of different dimensions, and find that there are minimal differences in all the examined multifractal quantities such as the multifractal support, the most frequent singularity exponent, and the generalized Hurst exponent.

  5. Characterization of porous collagen/hyaluronic acid scaffold modified by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide cross-linking.

    PubMed

    Park, Si-Nae; Park, Jong-Chul; Kim, Hea Ok; Song, Min Jung; Suh, Hwal

    2002-02-01

    In order to develop a scaffolding material for tissue regeneration, porous matrices containing collagen and hyaluronic acid were fabricated by freeze drying at -20 degrees C, -70 degrees C or -196 degrees C. The fabricated porous membranes were cross-linked using 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) in a range of 1-100 mM concentrations for enhancing mechanical stability of the composite matrix. Scanning electron microscope (SEM) views of the matrices demonstrated that the matrices obtained before cross-linking process had interconnected pores with mean diameters of 40, 90 or 230 microm and porosity of 58-66% according to the freezing temperature, and also the porous structures after cross-linking process were retained. The swelling test and IR spectroscopic measurement of different cross-linked membranes were carried out as a measure of the extent of cross-linking. The swelling behavior of cross-linked membranes showed no significant differences as cross-linking degree increased. FT-IR spectra showed the increase of the intensity of the absorbencies at amide bonds (1655, 1546, 1458 cm(-1)) compared to that of CH bond (2930 cm(-1)). In enzymatic degradation test, EDC treated membranes showed significant enhancement of the resistance to collagenase activity in comparison with 0.625% glutaraldehyde treated membranes. In cytotoxicity test using L929 fibroblastic cells, the EDC-cross-linked membranes demonstrated no significant toxicity. PMID:11791924

  6. Advances in the study of mechanical properties and constitutive law in the field of wood research

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Zhao, J. X.; Han, G. Z.

    2016-07-01

    This paper presents an overview of mechanical properties and constitutive law for wood. Current research on the mechanical properties of wood have mostly focused on density, grain, moisture, and other natural factors. It has been established that high density, dense grain, and high moisture lead to higher strength. In most literature, wood has been regarded as an anisotropic material because of its fiber. A microscopic view is used in research of wood today, in this way, which has allowed for clear observation of anisotropy. In general, wood has higher strength under a dynamic load, and no densification. The constitutive model is the basis of numerical analysis. An anisotropic model of porous and composite materials has been used for wood, but results were poor, and new constitutions have been introduced. According to the literature, there is no single theory that is widely accepted for the dynamic load. Research has shown that grain and moisture are key factors in wood strength, but there has not been enough study on dynamic loads so far. Hill law has been the most common method of simulation. Models that consider high strain rate are attracting more and more attention.

  7. [Animal protection in constitutional law?--On the necessity of including animal protection in the constitution].

    PubMed

    Caspar, J

    1998-03-01

    The inclusion of animal protection in the constitution poses a lengthy legal-political demand, which is again being vehemently discussed at the present time. Under consideration of juristic aspects, the following treatise attempts to clarify the legal requirements which presently exist for anchoring animal protection in constitutional law. It is therefore necessary in the first instance to explain the present situation regarding animal protection law. The legal situation in this respect is marked by a fundamental collision between special democratic rights guaranteed by the constitution on the one hand, and the norms of animal protection law on the other hand, which tend to restrict these rights. Based on concrete examples taken from court decisions, it is shown that constitutional vacuum surrounding a major part of animal protection law greatly complicates or even renders impossible the application and enforcement of the latter in practice. A prerequisite for a proper legal framework for animal protection is that the different special basic democratic rights governing animal use must be counterpoised by animal protection laws backed up by the constitution. Only by this means it is possible to prevent the ineffectiveness of animal protection legislative norms in the long term. PMID:9581372

  8. Constitutive heterochromatin reorganization during somatic cell reprogramming

    PubMed Central

    Fussner, Eden; Djuric, Ugljesa; Strauss, Mike; Hotta, Akitsu; Perez-Iratxeta, Carolina; Lanner, Fredrik; Dilworth, F Jeffrey; Ellis, James; Bazett-Jones, David P

    2011-01-01

    Induced pluripotent stem (iPS) cell reprogramming is a gradual epigenetic process that reactivates the pluripotent transcriptional network by erasing and establishing repressive epigenetic marks. In contrast to loci-specific epigenetic changes, heterochromatin domains undergo epigenetic resetting during the reprogramming process, but the effect on the heterochromatin ultrastructure is not known. Here, we characterize the physical structure of heterochromatin domains in full and partial mouse iPS cells by correlative electron spectroscopic imaging. In somatic and partial iPS cells, constitutive heterochromatin marked by H3K9me3 is highly compartmentalized into chromocentre structures of densely packed chromatin fibres. In contrast, chromocentre boundaries are poorly defined in pluripotent embryonic stem and full iPS cells, and are characterized by unusually dispersed 10 nm heterochromatin fibres in high Nanog-expressing cells, including pluripotent cells of the mouse blastocyst before differentiation. This heterochromatin reorganization accompanies retroviral silencing during conversion of partial iPS cells by MEK/GSK3 2i inhibitor treatment. Thus, constitutive heterochromatin is compacted in partial iPS cells but reorganizes into dispersed 10 nm chromatin fibres as the fully reprogrammed iPS cell state is acquired. PMID:21468033

  9. Constitutive modelling of composite biopolymer networks.

    PubMed

    Fallqvist, B; Kroon, M

    2016-04-21

    The mechanical behaviour of biopolymer networks is to a large extent determined at a microstructural level where the characteristics of individual filaments and the interactions between them determine the response at a macroscopic level. Phenomena such as viscoelasticity and strain-hardening followed by strain-softening are observed experimentally in these networks, often due to microstructural changes (such as filament sliding, rupture and cross-link debonding). Further, composite structures can also be formed with vastly different mechanical properties as compared to the individual networks. In this present paper, we present a constitutive model presented in a continuum framework aimed at capturing these effects. Special care is taken to formulate thermodynamically consistent evolution laws for dissipative effects. This model, incorporating possible anisotropic network properties, is based on a strain energy function, split into an isochoric and a volumetric part. Generalisation to three dimensions is performed by numerical integration over the unit sphere. Model predictions indicate that the constitutive model is well able to predict the elastic and viscoelastic response of biological networks, and to an extent also composite structures. PMID:26851172

  10. Relationships among certain joint constitutive models.

    SciTech Connect

    Segalman, Daniel Joseph; Starr, Michael James

    2004-09-01

    In a recent paper, Starr and Segalman demonstrated that any Masing model can be represented as a parallel-series Iwan model. A preponderance of the constitutive models that have been suggested for simulating mechanical joints are Masing models, and the purpose of this discussion is to demonstrate how the Iwan representation of those models can yield insight into their character. In particular, this approach can facilitate a critical comparison among numerous plausible constitutive models. It is explicitly shown that three-parameter models such as Smallwood's (Ramberg-Osgood) calculate parameters in such a manner that macro-slip is not an independent parameter, yet the model admits macro-slip. The introduction of a fourth parameter is therefore required. It is shown that when a macro-slip force is specified for the Smallwood model the result is a special case of the Segalman four-parameter model. Both of these models admit a slope discontinuity at the inception of macro-slip. A five-parameter model that has the beneficial features of Segalman's four-parameter model is proposed. This model manifests a force-displacement curve having a continuous first derivative.

  11. Space shuttle propellant constitutive law verification tests

    NASA Technical Reports Server (NTRS)

    Thompson, James R.

    1995-01-01

    As part of the Propellants Task (Task 2.0) on the Solid Propulsion Integrity Program (SPIP), a database of material properties was generated for the Space Shuttle Redesigned Solid Rocket Motor (RSRM) PBAN-based propellant. A parallel effort on the Propellants Task was the generation of an improved constitutive theory for the PBAN propellant suitable for use in a finite element analysis (FEA) of the RSRM. The outcome of an analysis with the improved constitutive theory would be more reliable prediction of structural margins of safety. The work described in this report was performed by Materials Laboratory personnel at Thiokol Corporation/Huntsville Division under NASA contract NAS8-39619, Mod. 3. The report documents the test procedures for the refinement and verification tests for the improved Space Shuttle RSRM propellant material model, and summarizes the resulting test data. TP-H1148 propellant obtained from mix E660411 (manufactured February 1989) which had experienced ambient igloo storage in Huntsville, Alabama since January 1990, was used for these tests.

  12. Constitutive modeling for isotropic materials (HOST)

    NASA Technical Reports Server (NTRS)

    Lindholm, U. S.; Chan, K. S.; Bodner, S. R.; Weber, R. M.; Walker, K. P.; Cassenti, B. N.

    1985-01-01

    This report presents the results of the second year of work on a problem which is part of the NASA HOST Program. Its goals are: (1) to develop and validate unified constitutive models for isotropic materials, and (2) to demonstrate their usefulness for structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are that of Bodner-Partom and Walker. For model evaluation purposes, a large constitutive data base is generated for a B1900 + Hf alloy by performing uniaxial tensile, creep, cyclic, stress relation, and thermomechanical fatigue (TMF) tests as well as biaxial (tension/torsion) tests under proportional and nonproportional loading over a wide range of strain rates and temperatures. Systematic approaches for evaluating material constants from a small subset of the data base are developed. Correlations of the uniaxial and biaxial tests data with the theories of Bodner-Partom and Walker are performed to establish the accuracy, range of applicability, and integability of the models. Both models are implemented in the MARC finite element computer code and used for TMF analyses. Benchmark notch round experiments are conducted and the results compared with finite-element analyses using the MARC code and the Walker model.

  13. Porous-electrode preparation method

    DOEpatents

    Arons, R.M.; Dusek, J.T.

    1981-09-17

    A porous sintered plaque is provided with a bimodal porosity that is especially well suited for use as an electrode within a molten carbonate fuel cell. The coarse porosity is sufficient for admitting gases into contact with the reaction surfaces while the fine porosity is wetted with and retains molten electrolyte on the reaction sites. The electrode structure is prepared by providing a very fine powder such as nickel oxide and blending the powder with a suitable decomposable binder to form a solid mass. The mass is comminuted into agglomerate size particles substantially larger than the fine oxide particles and formed into a cohesive compact for subsequent sintering. Sintering is carried out at sufficient conditions to bind the agglomerates together into a porous structure having both coarse and fine porosity. Where lithiated nickel oxide cathodes are prepared, the sintering conditions can be moderate enough to retain substantial quantities of lithium within the electrode for adequate conductivity.

  14. Metal recovery from porous materials

    DOEpatents

    Sturcken, E.F.

    1992-10-13

    A method is described for recovering plutonium and other metals from materials by leaching comprising the steps of incinerating the materials to form a porous matrix as the residue of incineration, immersing the matrix into acid in a microwave-transparent pressure vessel, sealing the pressure vessel, and applying microwaves so that the temperature and the pressure in the pressure vessel increase. The acid for recovering plutonium can be a mixture of HBF[sub 4] and HNO[sub 3] and preferably the pressure is increased to at least 100 PSI and the temperature to at least 200 C. The porous material can be pulverized before immersion to further increase the leach rate.

  15. Novel hollow powder porous structures

    SciTech Connect

    Sypeck, D.J.; Parrish, P.A.; Wadley, H.N.G.

    1998-12-31

    Recent finite element calculations indicate that structures constructed from partially compacted hollow spheres exhibit a greater stiffness and strength than many other cellular structures at comparable density. It has been observed that gas atomization of metallic powders often leads to entrapment of the flow field gas. The resulting hollow powders are an unwanted by-product in the sense that they lead to porosity and future sites of defect in solid parts. Here a method is developed to separate the hollow powders according to their size, shape and density. They are then consolidated to a porous structure. Examples of this are given for both a titanium alloy and a nickel-base superalloy. The compressive mechanical properties are measured and compared to those of other porous structures.

  16. POROUS WALL, HOLLOW GLASS MICROSPHERES

    SciTech Connect

    Sexton, W.

    2012-06-30

    Hollow Glass Microspheres (HGM) is not a new technology. All one has to do is go to the internet and Google{trademark} HGM. Anyone can buy HGM and they have a wide variety of uses. HGM are usually between 1 to 100 microns in diameter, although their size can range from 100 nanometers to 5 millimeters in diameter. HGM are used as lightweight filler in composite materials such as syntactic foam and lightweight concrete. In 1968 a patent was issued to W. Beck of the 3M{trademark} Company for 'Glass Bubbles Prepared by Reheating Solid Glass Particles'. In 1983 P. Howell was issued a patent for 'Glass Bubbles of Increased Collapse Strength' and in 1988 H. Marshall was issued a patent for 'Glass Microbubbles'. Now Google{trademark}, Porous Wall, Hollow Glass Microspheres (PW-HGMs), the key words here are Porous Wall. Almost every article has its beginning with the research done at the Savannah River National Laboratory (SRNL). The Savannah River Site (SRS) where SRNL is located has a long and successful history of working with hydrogen and its isotopes for national security, energy, waste management and environmental remediation applications. This includes more than 30 years of experience developing, processing, and implementing special ceramics, including glasses for a variety of Department of Energy (DOE) missions. In the case of glasses, SRS and SRNL have been involved in both the science and engineering of vitreous or glass based systems. As a part of this glass experience and expertise, SRNL has developed a number of niches in the glass arena, one of which is the development of porous glass systems for a variety of applications. These porous glass systems include sol gel glasses, which include both xerogels and aerogels, as well as phase separated glass compositions, that can be subsequently treated to produce another unique type of porosity within the glass forms. The porous glasses can increase the surface area compared to 'normal glasses of a 1 to 2 order of

  17. Porous glasses for optical sensors

    NASA Astrophysics Data System (ADS)

    Dorosz, Dominik; Procyk, Bernadeta

    2006-03-01

    Microporous glasses from the Na II0-B II0 3-Si0 II system can be obtained by appropriate thermal and chemical treatment. During the thermal treatment the separation of the borate phase from the silicon skeleton has been occurred. The borates are in the form small drops joined to each other. In the course of chemical treatment the borates become leached in water, water solutions of acids or basis and the glass becomes porous. Microporous glasses may find application in many branches of science and engineering. The applications depend on the internal arrangement, size and shape of pores. These parameters may be in a wide range modified by a change of the chemical composition. The received porous glass was used as an element in optical fibre NO II sensor. The specific coloration reaction between organic reagents and NO II in the pores was occurred. It is possible to detection of 10-50 ppm NO II level.

  18. "G.P.S Matrices" programme: A method to improve the mastery level of social science students in matrices operations

    NASA Astrophysics Data System (ADS)

    Lee, Ken Voon

    2013-04-01

    The purpose of this action research was to increase the mastery level of Form Five Social Science students in Tawau II National Secondary School in the operations of addition, subtraction and multiplication of matrices in Mathematics. A total of 30 students were involved. Preliminary findings through the analysis of pre-test results and questionnaire had identified the main problem faced in which the students felt confused with the application of principles of the operations of matrices when performing these operations. Therefore, an action research was conducted using an intervention programme called "G.P.S Matrices" to overcome the problem. This programme was divided into three phases. 'Gift of Matrices' phase aimed at forming matrix teaching aids. The second and third phases were 'Positioning the Elements of Matrices' and 'Strenghtening the Concept of Matrices'. These two phases were aimed at increasing the level of understanding and memory of the students towards the principles of matrix operations. Besides, this third phase was also aimed at creating an interesting learning environment. A comparison between the results of pre-test and post-test had shown a remarkable improvement in students' performances after implementing the programme. In addition, the analysis of interview findings also indicated a positive feedback on the changes in students' attitude, particularly in the aspect of students' understanding level. Moreover, the level of students' memory also increased following the use of the concrete matrix teaching aids created in phase one. Besides, teachers felt encouraging when conducive learning environment was created through students' presentation activity held in third phase. Furthermore, students were voluntarily involved in these student-centred activities. In conclusion, this research findings showed an increase in the mastery level of students in these three matrix operations and thus the objective of the research had been achieved.

  19. Permeability of compacting porous lavas

    NASA Astrophysics Data System (ADS)

    Ashwell, P. A.; Kendrick, J. E.; Lavallée, Y.; Kennedy, B. M.; Hess, K.-U.; Aulock, F. W.; Wadsworth, F. B.; Vasseur, J.; Dingwell, D. B.

    2015-03-01

    The highly transient nature of outgassing commonly observed at volcanoes is in part controlled by the permeability of lava domes and shallow conduits. Lava domes generally consist of a porous outer carapace surrounding a denser lava core with internal shear zones of variable porosity. Here we examine densification using uniaxial compression experiments on variably crystalline and porous rhyolitic dome lavas from the Taupo Volcanic Zone. Experiments were conducted at 900°C and an applied stress of 3 MPa to 60% strain, while monitoring acoustic emissions to track cracking. The evolution of the porous network was assessed via X-ray computed tomography, He-pycnometry, and relative gas permeability. High starting connected porosities led to low apparent viscosities and high strain rates, initially accompanied by abundant acoustic emissions. As compaction ensued, the lavas evolved; apparent viscosity increased and strain rate decreased due to strain hardening of the suspensions. Permeability fluctuations resulted from the interplay between viscous flow and brittle failure. Where phenocrysts were abundant, cracks had limited spatial extent, and pore closure decreased axial and radial permeability proportionally, maintaining the initial anisotropy. In crystal-poor lavas, axial cracks had a more profound effect, and permeability anisotropy switched to favor axial flow. Irrespective of porosity, both crystalline samples compacted to a threshold minimum porosity of 17-19%, whereas the crystal-poor sample did not achieve its compaction limit. This indicates that unconfined loading of porous dome lavas does not necessarily form an impermeable plug and may be hindered, in part by the presence of crystals.

  20. Combustion synthesis of porous biomaterials.

    PubMed

    Ayers, Reed A; Burkes, Douglas E; Gottoli, Guglielmo; Yi, Hu-Chun; Zhim, Fouad; Yahia, L'hocine; Moore, John J

    2007-06-01

    This article discusses the unique material manufacturing process of self-propagating high temperature synthesis (SHS) as applied to the making of porous biomaterials. Porous materials have long been considered as the first step toward in-vivo bone tissue engineering and the creation of patient life-time implants. The authors have approached this challenge by utilizing combustion synthesis, to create novel materials such as NiTi + TiC as well as porous forms of materials that are commonly accepted for biomedical applications such as tricalcium phosphate and hydroxyapatite. In the SHS product, physico-chemical properties are controlled by, but not limited to, reactant stoichiometry; green density; particle size of the reactant mix; use or presence of a gasifying agent; heating rate of the reactants and gravity. By balancing these parameters, the energy of the reaction is controlled to create the desired product stoichiometry, porosity, and mechanical properties. SHS provides a means to rapidly manufacture materials, saving time and production costs as well as enabling the synthesis of custom devices through the use of individual molds. Mold materials can range from graphite to paper or paper machete. Combustion synthesis offers a method for the rapid manufacture of affordable, individual biomedical devices that will reduce patient recovery time. PMID:17187390

  1. Microscale transport in porous media

    SciTech Connect

    Rashidi, M.; Rinker, R.

    1996-04-01

    In-pore transport processes in homogeneous and heterogeneous porous media have been investigated using novel 3D imaging techniques. The experimental system consists of a clear column packed with clear particles and a refractive index-matched fluid seeded with fluorescent tracers and an organic solute dye. By illuminating the porous regions within the column with a planar sheet of laser beam, flow and transport processes through the porous medium can be observed microscopically, and qualitative and quantitative in-pore transport information can be obtained at a good resolution and a high accuracy. Fluorescent images are captured and recorded at every vertical plane location while sweeping back and forth across the test section. These digitized transport images are then analyzed and accumulated over a 3D volume within the column. This paper reports on pore-scale observations of velocity, chemical concentration, and fluxes. Tests were undertaken with two separate columns. One is a rectangular column for chemical transport and bioremediation studies in aqueous heterogeneous systems and the other is a cylindrical column for flow and transport investigations in nonaqueous homogeneous systems.

  2. Porous heat-insulation material

    SciTech Connect

    Chentemirov, M.G.; Dyachkovsky, F.S.; Enikolopov, N.S.; Gavrilov, J.A.; Gorbachev, J.G.; Kudinova, O.I.; Lukienko, E.P.; Maklakova, T.A.; Novokshonova, L.A.; Parsamian, L.O.; Poluyanov, A.F.

    1980-12-23

    A porous heat-insulation material comprising blocks molded from granules of a porous mineral filler with a polyolefin coating is described. The coating thickness is 1/1000 to 1/25 of the average granule diameter; in contact regions, said granules are spaced from each other at a distance of from 0.5 to 2.0 of the coating thickness, and the mass ratio between said porous mineral filler and said polyolefin is 80-98:20-2, respectively. The material of this invention has a volume mass of from 60 to 250 kg/m/sup 3/. The material features a high plasticity (its flexural strength is as high as 3-4 kgf/cm/sup 2/). The compression strength of the material is 9-1 kgf/cm/sup 2/. The material also has a low thermal conductivity; its thermal conductivity coefficient is 0.03-0.04 kcal/M/h//sup 0/C. The material is substantially non-combustible.

  3. Photophysical ablation of porous silicon

    NASA Astrophysics Data System (ADS)

    Aksenov, Valerii P.; Mikhailova, G. N.

    2004-07-01

    Laser ablation of porous silicon as a function of laser wavelength and width of silicon nanowires was studied in our experiments. The time-resolved evolution of the cloud of the porous silicon particles produced by laser ablation is studied in situ by the analysis of the kinetics of photoluminescence signal. The laser ablation of porous silicon produced by pulses of 532 nm or 337 nm radiation with addition of synchronized power pulses of 1064 nm radiation. The cloud of the nanometer-sized silicon crystallites had the high enhancement of luminescence quantum efficiency in the red region of spectra. The slow PL kinetics component, which is due to the localized carriers, decays on a millisecond time scale. The squeezed electron-hole plasma heating by IR-laser radiation may produce a damage of silicon nanowires. The fragments of nanowires in cloud must be smaller, than the critical length. The energy of excitation of e-h pair in fragment with contribution of longitude quantum modes must be lower than energy of the excited photons. Particles with lesser length don't absorb excited laser radiation and don't damage. For this case we may speak about the quantum mechanism of laser ablation of nanowires.

  4. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing... manufacture of sound records for export purposes, or upon satisfactory proof that the master records or metal matrices obtained therefrom have been exported or destroyed under Customs supervision, and that all...

  5. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing... manufacture of sound records for export purposes, or upon satisfactory proof that the master records or metal matrices obtained therefrom have been exported or destroyed under Customs supervision, and that all...

  6. 19 CFR 10.90 - Master records and metal matrices.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing... manufacture of sound records for export purposes, or upon satisfactory proof that the master records or metal matrices obtained therefrom have been exported or destroyed under Customs supervision, and that all...

  7. Extremal Positive Maps on M3(ℂ) and Idempotent Matrices

    NASA Astrophysics Data System (ADS)

    Miller, Marek; Olkiewicz, Robert

    2016-03-01

    A new method of analysing positive bistochastic maps on the algebra of complex matrices M3 has been proposed. By identifying the set of such maps with a convex set of linear operators on ℝ8, one can employ techniques from the theory of compact semigroups to obtain results concerning asymptotic properties of positive maps. It turns out that the idempotent elements play a crucial role in classifying the convex set into subsets, in which representations of extremal positive maps are to be found. It has been shown that all positive bistochastic maps, extremal in the set of all positive maps of M3, that are not Jordan isomorphisms of M3 are represented by matrices that fall into two possible categories, determined by the simplest idempotent matrices: one by the zero matrix, and the other by a one-dimensional orthogonal projection. Some norm conditions for matrices representing possible extremal maps have been specified and examples of maps from both categories have been brought up, based on the results published previously.

  8. DESI-MS Analysis of Mycotoxins from Grain Matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction – Determination of mycotoxins in grain matrices is a frequent need of growers and processors of cereal grains. Sample preparation for mycotoxin analysis is often laborious and time consuming. Here we demonstrate the application of desorption electrospray ionization – mass spectrometry...

  9. A Role for M-Matrices in Modelling Population Growth

    ERIC Educational Resources Information Center

    James, Glyn; Rumchev, Ventsi

    2006-01-01

    Adopting a discrete-time cohort-type model to represent the dynamics of a population, the problem of achieving a desired total size of the population under a balanced growth (contraction) and the problem of maintaining the desired size, once achieved, are studied. Properties of positive-time systems and M-matrices are used to develop the results,…

  10. Controlled growth factor release from synthetic extracellular matrices

    NASA Astrophysics Data System (ADS)

    Lee, Kuen Yong; Peters, Martin C.; Anderson, Kenneth W.; Mooney, David J.

    2000-12-01

    Polymeric matrices can be used to grow new tissues and organs, and the delivery of growth factors from these matrices is one method to regenerate tissues. A problem with engineering tissues that exist in a mechanically dynamic environment, such as bone, muscle and blood vessels, is that most drug delivery systems have been designed to operate under static conditions. We thought that polymeric matrices, which release growth factors in response to mechanical signals, might provide a new approach to guide tissue formation in mechanically stressed environments. Critical design features for this type of system include the ability to undergo repeated deformation, and a reversible binding of the protein growth factors to polymeric matrices to allow for responses to repeated stimuli. Here we report a model delivery system that can respond to mechanical signalling and upregulate the release of a growth factor to promote blood vessel formation. This approach may find a number of applications, including regeneration and engineering of new tissues and more general drug-delivery applications.

  11. Technological optimization of manufacture of probiotic whey cheese matrices.

    PubMed

    Madureira, Ana R; Brandão, Teresa; Gomes, Ana M; Pintado, Manuela E; Malcata, F Xavier

    2011-03-01

    In attempts to optimize their manufacture, whey cheese matrices obtained via thermal processing of whey (leading to protein precipitation) and inoculated with probiotic cultures were tested. A central composite, face-centered design was followed, so a total of 16 experiments were run using fractional addition of bovine milk to feedstock whey, homogenization time, and storage time of whey cheese as processing parameters. Probiotic whey cheese matrices were inoculated with Lactobacillus casei LAFTIL26 at 10% (v/v), whereas control whey cheese matrices were added with skim milk previously acidified with lactic acid to the same level. All whey cheeses were stored at 7 °C up to 14 d. Chemical and sensory analyses were carried out for all samples, as well as rheological characterization by oscillatory viscometry and textural profiling. As expected, differences were found between control and probiotic matrices: fractional addition of milk and storage time were the factors accounting for the most important effects. Estimation of the best operating parameters was via response surface analysis: milk addition at a rate of 10% to 15% (v/v), and homogenization for 5 min led to the best probiotic whey cheeses in terms of texture and organoleptic properties, whereas the best time for consumption was found to be by 9 d of storage following manufacture. PMID:21535760

  12. Dimensionality of Data Matrices with Applications to Gene Expression Profiles

    ERIC Educational Resources Information Center

    Feng, Xingdong

    2009-01-01

    Probe-level microarray data are usually stored in matrices. Take a given probe set (gene), for example, each row of the matrix corresponds to an array, and each column corresponds to a probe. Often, people summarize each array by the gene expression level. Is one number sufficient to summarize a whole probe set for a specific gene in an array?…

  13. Technologies for detecting botulinum neurotoxins in biological and environmental matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomonitoring of food and environmental matrices is critical for the rapid and sensitive diagnosis, treatment, and prevention of diseases caused by toxins. The United States Centers for Disease Control and Prevention (CDC) has noted that toxins from bacteria, fungi, algae, and plants present an ongo...

  14. Variation in Raven's Progressive Matrices Scores across Time and Place

    ERIC Educational Resources Information Center

    Brouwers, Symen A.; Van de Vijver, Fons J. R.; Van Hemert, Dianne A.

    2009-01-01

    The paper describes a cross-cultural and historical meta-analysis of Raven's Progressive Matrices. Data were analyzed of 798 samples from 45 countries (N = 244,316), which were published between 1944 and 2003. Country-level indicators of educational permeation (which involves a broad set of interrelated educational input and output factors that…

  15. Current technologies for detection of ricin in different matrices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ricin is a convenient, potent, and available toxin for terrorist acts. The importance of detecting it in various matrices is obvious. This chapter reviews methods for ricin detection based on the mechanisms used for assay development. Five detection approaches are reviewed: 1. Antibody-based metho...

  16. Validating Alternative Modes of Scoring for Coloured Progressive Matrices.

    ERIC Educational Resources Information Center

    Razel, Micha; Eylon, Bat-Sheva

    Conventional scoring of the Coloured Progressive Matrices (CPM) was compared with three methods of multiple weight scoring. The methods include: (1) theoretical weighting in which the weights were based on a theory of cognitive processing; (2) judged weighting in which the weights were given by a group of nine adult expert judges; and (3)…

  17. A minimax approach to spatial estimation using affinity matrices

    NASA Technical Reports Server (NTRS)

    Morris, C. N.

    1983-01-01

    Estimates made in the plane to improve on noisy unbiased estimates were combined. Only a small fraction of points in a giant grid were used to do this, those that are most like a given point. A component of this process defining an affinity matrix of values, indicating which points are relevant to others. Minimax rules are shown to be based on affinity matrices.

  18. Cluster Matrices for Health Occupations. Education for Employment Task Lists.

    ERIC Educational Resources Information Center

    Lathrop, Janice

    These cluster matrices provide duties and tasks that form the basis of instructional content for secondary, postsecondary, and adult training programs for health occupations. The eight clusters (and the job titles included in each cluster) are as follows: (1) dental assisting (dental assistant); (2) dental laboratory technology (dental laboratory…

  19. Automorphisms of semigroups of invertible matrices with nonnegative integer elements

    SciTech Connect

    Semenov, Pavel P

    2012-09-30

    Let G{sub n}(Z) be the subsemigroup of GL{sub n}(Z) consisting of the matrices with nonnegative integer coefficients. In the paper, the automorphisms of this semigroup are described for n{>=}2. Bibliography: 5 titles.

  20. Effect of an Interactive Courseware in the Learning of Matrices

    ERIC Educational Resources Information Center

    Hoon, Teoh Sian; Chong, Toh Seong; Binti Ngah, Nor Azilah

    2010-01-01

    The main aim of this study is to integrate cooperative learning strategies, mastery learning and interactive multimedia to improve students' performance in Mathematics, specifically in the topic of matrices. It involved a quasi-experimental design with gain scores and time-on-task as dependent variables. The independent variables were three…