Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al

NASA Astrophysics Data System (ADS)

Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin; Bickermann, Matthias

2018-03-01

We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1-1.5 at 7-24 vol% O2, while for Ce they are roughly below 0.01 at 1.5-34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5-21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1-x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV.

Differential Thermal Analysis of Hg(1-x)Mn(x)Te Alloys in the X=0 to 0.3 Range

NASA Technical Reports Server (NTRS)

Price, M. W.; Scripa, R. N.; Szofran, F. R.; Lehoczky, S. L.; Su, C-H

1998-01-01

Understanding the experimental conditions necessary for the development of radial and axial compositional homogeneity in directionally solidified Hg(0.89)Mn(0.11)Te(MMT) crystals has been difficult due to the lack of segregation coefficient data on the Hg(1-x)Mn(x)Te alloy system in the X = 0 to 0.3 composition range. Determining segregation coefficient data from the available Hg(1-x)Mn(x)Te alloy phase equilibria data is not practical due to discrepancies in the shape of the reported solidus and liquidus curves in the X = 0 to 0.3 range. To resolve these discrepancies and to obtain segregation coefficient data which can be used to understand homogeneity in directionally solidified MMT crystals, the solidus and liquidus temperatures of seven Hg(1-x)Mn(x)Te alloys in the X = 0 to 0.3 range were determined using differential thermal analysis (DTA). The Hg(1-x)Mn(x)Te phase diagram constructed for the X = 0 to 0.3 range of this alloy system from the DTA measurements clarifies the shape of the solidus and liquidus curves in this range. The segregation coefficient for the Hg(1-x)Mn(x)Te system was found to vary from 5 to 4.4 as the solidus composition increased from 0-30 atomic percent MnTe. This information will be useful in the analysis of axial and radial homogeneity of directionally solidified MMT crystals.

Racial residential segregation and preterm birth: built environment as a mediator.

PubMed

Anthopolos, Rebecca; Kaufman, Jay S; Messer, Lynne C; Miranda, Marie Lynn

2014-05-01

Racial residential segregation has been associated with preterm birth. Few studies have examined mediating pathways, in part because, with binary outcomes, indirect effects estimated from multiplicative models generally lack causal interpretation. We develop a method to estimate additive-scale natural direct and indirect effects from logistic regression. We then evaluate whether segregation operates through poor-quality built environment to affect preterm birth. To estimate natural direct and indirect effects, we derive risk differences from logistic regression coefficients. Birth records (2000-2008) for Durham, North Carolina, were linked to neighborhood-level measures of racial isolation and a composite construct of poor-quality built environment. We decomposed the total effect of racial isolation on preterm birth into direct and indirect effects. The adjusted total effect of an interquartile increase in racial isolation on preterm birth was an extra 27 preterm events per 1000 births (risk difference = 0.027 [95% confidence interval = 0.007 to 0.047]). With poor-quality built environment held at the level it would take under isolation at the 25th percentile, the direct effect of an interquartile increase in isolation was 0.022 (-0.001 to 0.042). Poor-quality built environment accounted for 35% (11% to 65%) of the total effect. Our methodology facilitates the estimation of additive-scale natural effects with binary outcomes. In this study, the total effect of racial segregation on preterm birth was partially mediated by poor-quality built environment.

Finite element analysis of the effect of a non-planar solid-liquid interface on the lateral solute segregation during unidirectional solidification

NASA Technical Reports Server (NTRS)

Carlson, F. M.; Chin, L.-Y.; Fripp, A. L.; Crouch, R. K.

1982-01-01

The effect of solid-liquid interface shape on lateral solute segregation during steady-state unidirectional solidification of a binary mixture is calculated under the assumption of no convection in the liquid. A finite element technique is employed to compute the concentration field in the liquid and the lateral segregation in the solid with a curved boundary between the liquid and solid phases. The computational model is constructed assuming knowledge of the solid-liquid interface shape; no attempt is made to relate this shape to the thermal field. The influence of interface curvature on the lateral compositional variation is investigated over a range of system parameters including diffusivity, growth speed, distribution coefficient, and geometric factors of the system. In the limiting case of a slightly nonplanar interface, numerical results from the finite element technique are in good agreement with the analytical solutions of Coriell and Sekerka obtained by using linear theory. For the general case of highly non-planar interface shapes, the linear theory fails and the concentration field in the liquid as well as the lateral solute segregation in the solid can be calculated by using the finite element method.

Molecular theory of smectic ordering in liquid crystals with nanoscale segregation of different molecular fragments

NASA Astrophysics Data System (ADS)

Gorkunov, M. V.; Osipov, M. A.; Kapernaum, N.; Nonnenmacher, D.; Giesselmann, F.

2011-11-01

A molecular statistical theory of the smectic A phase is developed taking into account specific interactions between different molecular fragments which enables one to describe different microscopic scenario of the transition into the smectic phase. The effects of nanoscale segregation are described using molecular models with different combinations of attractive and repulsive sites. These models have been used to calculate numerically coefficients in the mean filed potential as functions of molecular model parameters and the period of the smectic structure. The same coefficients are calculated also for a conventional smectic with standard Gay-Berne interaction potential which does not promote the segregation. The free energy is minimized numerically to calculate the order parameters of the smectic A phases and to study the nature of the smectic transition in both systems. It has been found that in conventional materials the smectic order can be stabilized only when the orientational order is sufficiently high, In contrast, in materials with nanosegregation the smectic order develops mainly in the form of the orientational-translational wave while the nematic order parameter remains relatively small. Microscopic mechanisms of smectic ordering in both systems are discussed in detail, and the results for smectic order parameters are compared with experimental data for materials of various molecular structure.

Effect of Sr Content and Strain on Sr Surface Segregation of La 1–x Sr x Co 0.2 Fe 0.8 O 3-δ as Cathode Material for Solid Oxide Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Yang; Ludwig, Karl F.; Woicik, Joseph C.

2016-10-12

Strontium doped lanthanum cobalt ferrite (LSCF) is a widely used cathode material due to its high electronic and ionic conductivity, and reasonable oxygen surface exchange coefficient. However, LSCF can have long-term stability issues such as surface segregation of Sr during solid oxide fuel cell (SOFC) operation, which can adversely affect the electrochemical performance. Thus, understanding the nature of the Sr surface segregation phenomenon, and how it is affected by the composition of LSCF and strain are critical. In this research, heteroepitaxial thin films of La 1-x Sr xCo 0.2Fe 0.8O 3 - with varying Sr content (x = 0.4, 0.3,more » 0.2) were deposited by pulsed laser deposition (PLD) on single crystal NdGaO 3, SrTiO 3 and GdScO 3 substrates, leading to different levels of strain in the films. The extent of Sr segregation at the film surface was quantified using synchrotron-based total reflection x-ray fluorescence (TXRF), and atomic force microscopy (AFM). The electronic structure of the Sr-rich phases formed on the surface was investigated by hard X-ray photoelectron spectroscopy (HAXPES). The extent of Sr segregation was found to be a function of the Sr content in bulk. Lowering the Sr content from 40% to 30% reduced the surface segregation, but further lowering the Sr content to 20% increased the segregation. The strain of LSCF thin films on various substrates was measured using high-resolution x-ray diffraction (HRXRD) and the Sr surface segregation was found to be reduced with compressive strain and enhanced with tensile strain present within the thin films. A model was developed correlating the Sr surface segregation with Sr content and strain effects to explain the experimental results.« less

Czochralski growth of NaNO3-LiNO3 solid solution single crystals using axial vibrational control technique

NASA Astrophysics Data System (ADS)

Avetissov, Igor; Sadovskiy, Andrei; Belov, Stanislav; Kong Khan, Chan; Mozhevitina, Elena; Sukhanova, Ekaterina; Zharikov, Eugeniy

2014-09-01

T-x diagram of LiNO3-NaNO3 quasi-binary system has been improved using an original technique based on Raman measurements of condense phase. (LiNO3)x(NaNO3)1-x solid solution single crystal has been grown at different regimes of axial vibrational control (AVC) technique. Significant difference in segregation coefficient behavior between AVC-CZ and conventional CZ grown crystals has appeared: with AVC intensity increase the segregation coefficient (SC) raises for light molecular weight elements, SC reduces for medium molecular weight elements, and SC remains practically unchangeable for heavy molecular weight elements. Effect of vibrational intensity on vibron and optical characteristics, microhardness of AVC-CZ (LiNO3)x(NaNO3)1-x solid solution single crystals has been studied. For the AVC-CZ crystals has been observed increases in microhardness as well as in optical transmission up to 10 rel% compare to conventional CZ grown crystals.

Microgravity Segregation in Binary Mixtures of Inelastic Spheres Driven by Velocity Fluctuation Gradients

NASA Technical Reports Server (NTRS)

Jenkins, James T.; Louge, Michel Y.

1996-01-01

We are interested in collisional granular flows of dry materials in reduced gravity. Because the particles interact through collisions, the energy of the particle velocity fluctuations plays an important role in the physics. Here we focus on the separation of grains by properties - size, for example - that is driven by spatial gradients in the fluctuation energy of the grains. The segregation of grains by size is commonly observed in geophysical flows and industrial processes. Segregation of flowing grains can also take place based on other properties, e.g. shape, mass, friction, and coefficient of restitution. Many mechanisms may be responsible for segregation; most of these are strongly influenced by gravity. Here, we outline a mechanism that is independent of gravity. This mechanism may be important but is often obscured in terrestrial grain flows. It is driven by gradients in fluctuation energy. In microgravity, the separation of grains by property will proceed slowly enough to permit flight observations to provide an unambiguous measurement of the transport coefficients associated with the segregation. In this context, we are planning a microgravity shear cell experiment that contains a mixture of two types of spherical grains. The grains will be driven to interact with two different types of boundaries on either sides of the cell. The resulting separation will be observed visually.

Feedback effect of base roughness on particle size segregation in bidisperse granular avalanche

NASA Astrophysics Data System (ADS)

Jing, L.; Kwok, F.

2017-12-01

Particle size segregation in a geophysical flow interplays with base roughness, leading to rich behaviors such as bouldery front formation and fingering instability. The interplay originates mainly from the fact that larger particles slip more easily on a slope, the slip affects the progress of segregation, and segregation changes the size of particles contacting the slope. Recent studies show that slip velocity scales with geometric roughness (which involves both the size and spacing of base particles), and the roughness becomes a function of time during segregation. However, at least two questions remain unanswered: 1) In addition to geometric roughness, what is the role of mechanical parameters at boundaries? 2) To what extent the findings from steady flows are valid in a transient system, which is more common in actual geophysical flows? Here we study two configurations using the discrete element method, the first being a steady flow with periodic boundaries, where we vary the size, spatial arrangement, and contact parameters of base particles. The second consists in dambreak-type bidisperse granular avalanches over inclined planes, where the degree of segregation, base roughness, flow thickness, and base velocity are measured locally as the flow evolves. We found that: 1) On a frictional plane in the absence of geometric roughness, the friction parameter μ controls the amount of basal slip. A lower μ leads to a slower segregation. 2) On a bumpy base with low geometric roughness (where slip still occurs), the effect of μ becomes marginal, while the coefficient of restitution e controls the slip velocity; this indicates the significance of normal collision in the working mechanism of a bumpy base. Upon sliding, large particles near the base may exhibit an ordered state where shear is poorly developed, which delays the onset of segregation. 3) Both μ and e have no influence when the geometric roughness is sufficient to sustain a nonslip condition. Our results suggest the feedback effect of base roughness on segregation, which has a theoretical significance in the boundary treatment when modeling geophysical flows. The study also shows the possibility to establish a universal scaling law correlating slip velocity, base roughness, and the degree of segregation in both steady and unsteady flows.

Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy

NASA Astrophysics Data System (ADS)

Wang, Changshuai; Su, Haijun; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang

2017-09-01

Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy, considered as boiler and turbine materials in 700 °C advanced ultra-supercritical coal-fired power plants, have been investigated by differential thermal analysis and directional solidification quenching technique. Results reveal that P decreases the solidus temperature, but only has negligible influence on liquidus temperature. After P was added, the solidification sequence has no apparent change, but the width of the mushy zone increases and dendritic structures become coarser. Moreover, P increases the amount and changes the morphology of MC carbide. Energy-dispersive spectroscopy analysis reveals that P has obvious influence on the segregation behavior of the constitute elements with equilibrium partition coefficients (ki) far away from unity, whereas has negligible effect on the constituent elements with ki close to unity and has more influence on the final stage of solidification than at early stage. The distribution profiles reveal that P atoms pile up ahead of the solid/liquid (S/L) interface and strongly segregate to the interdendritic liquid region. The influence of P on solidification characteristics and segregation behavior of Ni-Fe-Cr-based alloy could be attributed to the accumulation of P ahead of the S/L interface during solidification.

Computer Aided Design of Integrated Circuit Fabrication Processes for VLSI Devices

DTIC Science & Technology

1980-01-01

diffusion coefficient and surface conc,,tration of the chlorine as well as any field present; X is related to the ratio ol the diffusion coefficient to...with polysilicon gat(. .ed contacts, the interaction of oxidation, segregation and diffusion in all regions of the simulation space is a critical

Ultra-fast grain boundary diffusion and its contribution to surface segregation on a martensitic steel. Experiments and modeling

NASA Astrophysics Data System (ADS)

Christien, F.; Le Gall, R.

2011-09-01

Phosphorus surface segregation was measured by Auger Electron Spectroscopy on a 17-4 PH martensitic stainless steel at 450, 550 and 600 °C. Surface segregation was shown to be much faster than expected which was attributed to a high contribution of phosphorus diffusion along the former austenitic grain boundaries. A model of surface segregation was developed following the Darken-du Plessis approach and taking account of both bulk and grain boundary solute diffusion. The phosphorus grain boundary diffusion coefficient in 17-4 PH was estimated: DGB< = 6.2 10 4 exp(- 157 kJ mol - 1 /RT)cm 2 s - 1 . It is found to be more than three orders of magnitude higher in 17-4 PH steel than in α-iron.

Wood variables affecting the friction coefficient of spruce pine on steel

Treesearch

Truett J. Lemoine; Charles W. McMillin; Floyd G. Manwiller

1970-01-01

Wood of spruce pine, Pinus glabra Walk., was factorially segregated by moisture content (0, 10, and 18 percent), specific gravity (less than 0.45 and more than 0.45), and extractive content (unextracted and extractive-freE), and the kinetic coefficient of friction on steel (having surface roughness of 9 microinches RMS) determined for tangential...

A New Predictive Model of Centerline Segregation in Continuous Cast Steel Slabs by Using Multivariate Adaptive Regression Splines Approach

PubMed Central

García Nieto, Paulino José; González Suárez, Victor Manuel; Álvarez Antón, Juan Carlos; Mayo Bayón, Ricardo; Sirgo Blanco, José Ángel; Díaz Fernández, Ana María

2015-01-01

The aim of this study was to obtain a predictive model able to perform an early detection of central segregation severity in continuous cast steel slabs. Segregation in steel cast products is an internal defect that can be very harmful when slabs are rolled in heavy plate mills. In this research work, the central segregation was studied with success using the data mining methodology based on multivariate adaptive regression splines (MARS) technique. For this purpose, the most important physical-chemical parameters are considered. The results of the present study are two-fold. In the first place, the significance of each physical-chemical variable on the segregation is presented through the model. Second, a model for forecasting segregation is obtained. Regression with optimal hyperparameters was performed and coefficients of determination equal to 0.93 for continuity factor estimation and 0.95 for average width were obtained when the MARS technique was applied to the experimental dataset, respectively. The agreement between experimental data and the model confirmed the good performance of the latter.

Density Zoning and Class Segregation in U.S. Metropolitan Areas

PubMed Central

Rothwell, Jonathan T.; Massey, Douglas S.

2013-01-01

Objectives Socioeconomic segregation rose substantially in U.S. cities during the final decades of the 20th century and we argue zoning regulations are an important cause for this increase. Methods We measure neighborhood economic segregation using the Gini Coefficient for neighborhood income inequality and the poor-affluent exposure index. These outcomes are regressed on an index of density zoning developed from the work of Pendall for 50 U.S. metropolitan areas, while controlling for other metropolitan characteristics likely to affect urban housing markets and class segregation. Results For both 2000 and changes from 1990 to 2000, OLS estimates reveal a strong relationship between density zoning and income segregation, and replication using 2SLS suggests that the relationship is causal. We also show that zoning is associated with higher inter-jurisdictional inequality. Conclusions Metropolitan areas with suburbs that restrict the density of residential construction are more segregated on the basis of income than those with more permissive density zoning regimes. This arrangement perpetuates and exacerbates racial and class inequality in the United States. PMID:21117332

Solute boundary layer on a rotating crystal

NASA Astrophysics Data System (ADS)

Povinelli, Michelle L.; Korpela, Seppo A.; Chait, Arnon

1994-11-01

A perturbation analysis has been carried out for the solutal boundary layer next to a rotating crystal. Our aim is to extend the classical results of Burton, Prim and Slicher [1] in order to obtain higher order terms in asymptotic expansions for the concentration field and boundary-layer thickness. Expressions for the effective segregation coefficient are directly obtained from the concentration solution in the two limits that correspond to weak and strong rotation.

Highly siderophile elements were stripped from Earth’s mantle by iron sulfide segregation

NASA Astrophysics Data System (ADS)

Rubie, David C.; Laurenz, Vera; Jacobson, Seth A.; Morbidelli, Alessandro; Palme, Herbert; Vogel, Antje K.; Frost, Daniel J.

2016-09-01

Highly siderophile elements (HSEs) are strongly depleted in the bulk silicate Earth (BSE) but are present in near-chondritic relative abundances. The conventional explanation is that the HSEs were stripped from the mantle by the segregation of metal during core formation but were added back in near-chondritic proportions by late accretion, after core formation had ceased. Here we show that metal-silicate equilibration and segregation during Earth’s core formation actually increased HSE mantle concentrations because HSE partition coefficients are relatively low at the high pressures of core formation within Earth. The pervasive exsolution and segregation of iron sulfide liquid from silicate liquid (the “Hadean matte”) stripped magma oceans of HSEs during cooling and crystallization, before late accretion, and resulted in slightly suprachondritic palladium/iridium and ruthenium/iridium ratios.

A comparative study of quantitative microsegregation analyses performed during the solidification of the Ni-base superalloy CMSX-10

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seo, Seong-Moon, E-mail: castme@kims.re.kr; Jeong, Hi-Won; Ahn, Young-Keun

Quantitative microsegregation analyses were systematically carried out during the solidification of the Ni-base superalloy CMSX-10 to clarify the methodological effect on the quantification of microsegregation and to fully understand the solidification microstructure. Three experimental techniques, namely, mushy zone quenching (MZQ), planar directional solidification followed by quenching (PDSQ), and random sampling (RS), were implemented for the analysis of microsegregation tendency and the magnitude of solute elements by electron probe microanalysis. The microprobe data and the calculation results of the diffusion field ahead of the solid/liquid (S/L) interface of PDSQ samples revealed that the liquid composition at the S/L interface is significantlymore » influenced by quenching. By applying the PDSQ technique, it was also found that the partition coefficients of all solute elements do not change appreciably during the solidification of primary γ. All three techniques could reasonably predict the segregation behavior of most solute elements. Nevertheless, the RS approach has a tendency to overestimate the magnitude of segregation for most solute elements when compared to the MZQ and PDSQ techniques. Moreover, the segregation direction of Cr and Mo predicted by the RS approach was found to be opposite from the results obtained by the MZQ and PDSQ techniques. This conflicting segregation behavior of Cr and Mo was discussed intensively. It was shown that the formation of Cr-rich areas near the γ/γ′ eutectic in various Ni-base superalloys, including the CMSX-10 alloy, could be successfully explained by the results of microprobe analysis performed on a sample quenched during the planar directional solidification of γ/γ′ eutectic. - Highlights: • Methodological effect on the quantification of microsegregation was clarified. • The liquid composition at the S/L interface was influenced by quenching. • The segregation direction of Cr varied depending on the experimental techniques. • Cr and Mo segregation in Ni-base superalloys was fully understood.« less

Face-by-face growth of sucrose crystals from aqueous solutions in the presence of raffinose—II: Growth morphology and segregation

NASA Astrophysics Data System (ADS)

Sgualdino, G.; Aquilano, D.; Pastero, L.; Vaccari, G.

2007-10-01

Raffinose segregation into sucrose crystals is experimentally determined along with the modifications of the quantitative sucrose growth morphology, which are in turn related to the different growth conditions. ( Craff, σ) morphodromes nicely represent the conflict between the supersaturation and the raffinose concentration in the solution on the growth morphology, while the overall segregation rate is nearly proportional to the linear overall crystal growth rate. Chernov and Burton-Prim-Slichter models, checked to fit our keff and ln(keff-1-1) coefficients as a function of the supersaturation and of the mean linear overall growth rate, do not allow to know whether the segregation occurs either by a process dominated by surface integration, or by additive transfer dominated by volume diffusion within the boundary layer. The distribution of segregated raffinose strictly depends on the { h k l} growth sectors and doped crystals contain deformed lattice zones, as it comes out from X-ray powder diagrams.

Competing dopants grain boundary segregation and resultant seebeck coefficient and power factor enhancement of thermoelectric calcium cobaltite ceramics

DOE PAGES

Boyle, Cullen; Liang, Liang; Chen, Yun; ...

2017-06-06

Here, the present work demonstrates the feasibility of increasing the values of Seebeck coefficient S and power factor of calcium cobaltite Ca 3Co 4O 9 ceramics through competing dopant grain boundary segregation. The nominal chemistry of the polycrystalline material system investigated is Ca 3–xBi xBa yCo 4O 9 with simultaneous stoichiometric substitution of Bi for Ca and non-stoichiometric addition of minute amounts of Ba. There is continuous increase of S due to Bi substitution and Ba addition. The electrical resistivity also changes upon doping. Overall, the power factor of best performing Bi and Ba co-doped sample is about 0.93 mWmore » m –1 K –2, which is one of the highest power factor values ever reported for Ca 3Co 4O 9, and corresponds to a factor of 3 increase compared to that of the baseline composition Ca 3Co 4O 9. Systematic nanostructure and chemistry characterization was performed on the samples with different nominal compositions. When Bi is the only dopant in Ca 3Co 4O 9, it can be found at both the grain interior and the grain boundaries GBs as a result of segregation. When Bi and Ba are added simultaneously as dopants, competing processes lead to the segregation of Ba and depletion of Bi at the GBs, with Bi present only in the grain interior. Bi substitution in the lattice increases the S at both the low and high temperature regimes, while the segregation of Ba at the GBs dramatically increase the S at low temperature regime.« less

Competing dopants grain boundary segregation and resultant seebeck coefficient and power factor enhancement of thermoelectric calcium cobaltite ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyle, Cullen; Liang, Liang; Chen, Yun

Here, the present work demonstrates the feasibility of increasing the values of Seebeck coefficient S and power factor of calcium cobaltite Ca 3Co 4O 9 ceramics through competing dopant grain boundary segregation. The nominal chemistry of the polycrystalline material system investigated is Ca 3–xBi xBa yCo 4O 9 with simultaneous stoichiometric substitution of Bi for Ca and non-stoichiometric addition of minute amounts of Ba. There is continuous increase of S due to Bi substitution and Ba addition. The electrical resistivity also changes upon doping. Overall, the power factor of best performing Bi and Ba co-doped sample is about 0.93 mWmore » m –1 K –2, which is one of the highest power factor values ever reported for Ca 3Co 4O 9, and corresponds to a factor of 3 increase compared to that of the baseline composition Ca 3Co 4O 9. Systematic nanostructure and chemistry characterization was performed on the samples with different nominal compositions. When Bi is the only dopant in Ca 3Co 4O 9, it can be found at both the grain interior and the grain boundaries GBs as a result of segregation. When Bi and Ba are added simultaneously as dopants, competing processes lead to the segregation of Ba and depletion of Bi at the GBs, with Bi present only in the grain interior. Bi substitution in the lattice increases the S at both the low and high temperature regimes, while the segregation of Ba at the GBs dramatically increase the S at low temperature regime.« less

Segregation Coefficients of Impurities in Selenium by Zone Refining

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Sha, Yi-Gao

1998-01-01

The purification of Se by zone refining process was studied. The impurity solute levels along the length of a zone-refined Se sample were measured by spark source mass spectrographic analysis. By comparing the experimental concentration levels with theoretical curves the segregation coefficient, defined as the ratio of equilibrium concentration of a given solute in the solid to that in the liquid, k = x(sub s)/x(sub l) for most of the impurities in Se are found to be close to unity, i.e., between 0.85 and 1.15, with the k value for Si, Zn, Fe, Na and Al greater than 1 and that for S, Cl, Ca, P, As, Mn and Cr less than 1. This implies that a large number of passes is needed for the successful implementation of zone refining in the purification of Se.

Friction and wear of some ferrous-base metallic glasses

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1983-01-01

Sliding friction experiments, X-ray photoelectron spectroscopy (XPS) analysis, and electron microscopy and diffraction studies were conducted with ferrous base metallic glasses (amorphous alloys) in contact with aluminum oxide at temperatures to 750 C in a vacuum. Sliding friction experiments were also conducted in argon and air atmospheres. The results of the investigation indicate that the coefficient of friction increases with increasing temperature to 350 C in vacuum. The increase in friction is due to an increase in adhesion resulting from surface segregation of boric oxide and/or silicon oxide to the surface of the foil. Above 500 C the coefficient of friction decreased rapidly. The decrease correlates with the segregation of boron nitride to the surface. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and/or silicon oxide at 350 C and boron nitride above 500 C. The segregation of contaminants is responsible for the friction behavior. The amorphous alloys have superior wear resistance to crystalline 304 stainless steel. The relative concentrations of the various constituents at the surfaces of the amorphous alloys are very different from the nominal bulk compositions.

Friction and wear of some ferrous-base metallic glasses

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1984-01-01

Sliding friction experiments, X-ray photoelectron spectroscopy (XPS) analysis, and electron microscopy and diffraction studies were conducted with ferrous base metallic glasses (amorphous alloys) in contact with aluminium oxide at temperatures to 750 C in a vacuum. Sliding friction experiments were also conducted in argon and air atmospheres. The results of the investigation indicate that the coefficient of friction increases with increasing temperature to 350 C in vacuum. The increase in friction is due to an increase in adhesion resulting from surface segregation of boric oxide and/or silicon oxide to the surface of the foil. Above 500 C the coefficient of friction decreased rapidly. The decrease correlates with the segregation of boron nitride to the surface. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and/or silicon oxide at 350 C and boron nitride above 500 C. The segregation of contaminants is responsible for the friction behavior. The amorphous alloys have superior wear resistance to crystalline 304 stainless steel. The relative concentrations of the various constituents at the surfaces of the amorphous alloys are very different from the nominal bulk compositions.

Direct observation of interface instability during crystal growth

NASA Technical Reports Server (NTRS)

Tiller, W. A.; Feigelson, R. S.; Elwell, D.

1982-01-01

The general aim of this investigation was to study interface stability and solute segregation phenomena during crystallization of a model system. Emphasis was to be placed on direct observational studies partly because this offered the possibility at a later stage of performing related experiments under substantially convection-free conditions in the space shuttle. The major achievements described in this report are: (1) the development of a new model system for fundamental studies of crystal growth from the melt and the measurement of a range of material parameters necessary for comparison of experiment with theory. (2) The introduction of a new method of measuring segregation coefficient using absorption of a laser beam by the liquid phase. (3) The comparison of segregation in crystals grown by gradient freezing and by pulling from the melt. (4) The introduction into the theory of solute segregation of an interface field term and comparison with experiment. (5) The introduction of the interface field term into the theories of constitutional supercooling and morphological stability and assessment of its importance.

Kinetic theory-based numerical modeling and analysis of bi-disperse segregated mixture fluidized bed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konan, N. A.; Huckaby, E. D.

We discuss a series of continuum Euler-Euler simulations of an initially mixed bi-disperse fluidized bed which segregates under certain operating conditions. The simulations use the multi-phase kinetic theory-based description of the momentum and energy exchanges between the phases by Simonin’s Group [see e.g. Gourdel, Simonin and Brunier (1999). Proceedings of 6th International Conference on Circulating Fluidized Beds, Germany, pp. 205-210]. The discussion and analysis of the results focus on the fluid-particle momentum exchange (i.e. drag). Simulations using mono- and poly-disperse fluid-particle drag correlations are analyzed for the Geldart D-type size bi-disperse gas-solid experiments performed by Goldschmidt et al. [Powder Tech.,more » pp. 135-159 (2003)]. The poly-disperse gas-particle drag correlations account for the local particle size distribution by using an effective mixture diameter when calculating the Reynolds number and then correcting the resulting force coefficient. Simulation results show very good predictions of the segregation index for bidisperse beds with the mono-disperse drag correlations contrary to the poly-disperse drag correlations for which the segregation rate is systematically under-predicted. The statistical analysis of the results shows a clear separation in the distribution of the gas-particle mean relaxation times of the small and large particles with simulations using the mono-disperse drag. In contrast, the poly-disperse drag simulations have a significant overlap and also a smaller difference in the mean particle relaxation times. This results in the small and large particles in the bed to respond to the gas similarly without enough relative time lag. The results suggest that the difference in the particle response time induce flow dynamics favorable to a force imbalance which results in the segregation.« less

Kinetic theory-based numerical modeling and analysis of bi-disperse segregated mixture fluidized bed

DOE PAGES

Konan, N. A.; Huckaby, E. D.

2017-06-21

We discuss a series of continuum Euler-Euler simulations of an initially mixed bi-disperse fluidized bed which segregates under certain operating conditions. The simulations use the multi-phase kinetic theory-based description of the momentum and energy exchanges between the phases by Simonin’s Group [see e.g. Gourdel, Simonin and Brunier (1999). Proceedings of 6th International Conference on Circulating Fluidized Beds, Germany, pp. 205-210]. The discussion and analysis of the results focus on the fluid-particle momentum exchange (i.e. drag). Simulations using mono- and poly-disperse fluid-particle drag correlations are analyzed for the Geldart D-type size bi-disperse gas-solid experiments performed by Goldschmidt et al. [Powder Tech.,more » pp. 135-159 (2003)]. The poly-disperse gas-particle drag correlations account for the local particle size distribution by using an effective mixture diameter when calculating the Reynolds number and then correcting the resulting force coefficient. Simulation results show very good predictions of the segregation index for bidisperse beds with the mono-disperse drag correlations contrary to the poly-disperse drag correlations for which the segregation rate is systematically under-predicted. The statistical analysis of the results shows a clear separation in the distribution of the gas-particle mean relaxation times of the small and large particles with simulations using the mono-disperse drag. In contrast, the poly-disperse drag simulations have a significant overlap and also a smaller difference in the mean particle relaxation times. This results in the small and large particles in the bed to respond to the gas similarly without enough relative time lag. The results suggest that the difference in the particle response time induce flow dynamics favorable to a force imbalance which results in the segregation.« less

Boron diffusion in bcc-Fe studied by first-principles calculations

NASA Astrophysics Data System (ADS)

Xianglong, Li; Ping, Wu; Ruijie, Yang; Dan, Yan; Sen, Chen; Shiping, Zhang; Ning, Chen

2016-03-01

The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is D0 = 1.05 × 10-7 exp (-0.75 eV/kT) m2 · s-1, while the diffusion coefficients of the B-monovacancy and the B-divacancy complex mechanisms are D1 = 1.22 × 10-6 f1 exp (-2.27 eV/kT) m2 · s-1 and D2 ≈ 8.36 × 10-6 exp (-4.81 eV/kT) m2 · s-1, respectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe-3%Si-B alloy (bcc structure). Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments. Project supported by the National Natural Science Foundation of China (Grant No. 51276016) and the National Basic Research Program of China (Grant No. 2012CB720406).

Income inequality and income segregation.

PubMed

Reardon, Sean F; Bischoff, Kendra

2011-01-01

This article investigates how the growth in income inequality from 1970 to 2000 affected patterns of income segregation along three dimensions: the spatial segregation of poverty and affluence, race-specific patterns of income segregation, and the geographic scale of income segregation. The evidence reveals a robust relationship between income inequality and income segregation, an effect that is larger for black families than for white families. In addition, income inequality affects income segregation primarily through its effect on the large-scale spatial segregation of affluence rather than by affecting the spatial segregation of poverty or by altering small-scale patterns of income segregation.

Effect of impurities and processing on silicon solar cells. Volume 1: Characterization methods for impurities in silicon and impurity effects data base

NASA Technical Reports Server (NTRS)

Hopkins, R. H.; Davis, J. R.; Rohatgi, A.; Campbell, R. B.; Blais, P. D.; Rai-Choudhury, P.; Stapleton, R. E.; Mollenkopf, H. C.; Mccormick, J. R.

1980-01-01

Two major topics are treated: methods to measure and evaluate impurity effects in silicon and comprehensive tabulations of data derived during the study. Discussions of deep level spectroscopy, detailed dark I-V measurements, recombination lifetime determination, scanned laser photo-response, conventional solar cell I-V techniques, and descriptions of silicon chemical analysis are presented and discussed. The tabulated data include lists of impurity segregation coefficients, ingot impurity analyses and estimated concentrations, typical deep level impurity spectra, photoconductive and open circuit decay lifetimes for individual metal-doped ingots, and a complete tabulation of the cell I-V characteristics of nearly 200 ingots.

Mapping the neuropsychological profile of temporal lobe epilepsy using cognitive network topology and graph theory.

PubMed

Kellermann, Tanja S; Bonilha, Leonardo; Eskandari, Ramin; Garcia-Ramos, Camille; Lin, Jack J; Hermann, Bruce P

2016-10-01

Normal cognitive function is defined by harmonious interaction among multiple neuropsychological domains. Epilepsy has a disruptive effect on cognition, but how diverse cognitive abilities differentially interact with one another compared with healthy controls (HC) is unclear. This study used graph theory to analyze the community structure of cognitive networks in adults with temporal lobe epilepsy (TLE) compared with that in HC. Neuropsychological assessment was performed in 100 patients with TLE and 82 HC. For each group, an adjacency matrix was constructed representing pair-wise correlation coefficients between raw scores obtained in each possible test combination. For each cognitive network, each node corresponded to a cognitive test; each link corresponded to the correlation coefficient between tests. Global network structure, community structure, and node-wise graph theory properties were qualitatively assessed. The community structure in patients with TLE was composed of fewer, larger, more mixed modules, characterizing three main modules representing close relationships between the following: 1) aspects of executive function (EF), verbal and visual memory, 2) speed and fluency, and 3) speed, EF, perception, language, intelligence, and nonverbal memory. Conversely, controls exhibited a relative division between cognitive functions, segregating into more numerous, smaller modules consisting of the following: 1) verbal memory, 2) language, perception, and intelligence, 3) speed and fluency, and 4) visual memory and EF. Overall node-wise clustering coefficient and efficiency were increased in TLE. Adults with TLE demonstrate a less clear and poorly structured segregation between multiple cognitive domains. This panorama suggests a higher degree of interdependency across multiple cognitive domains in TLE, possibly indicating compensatory mechanisms to overcome functional impairments. Copyright © 2016 Elsevier Inc. All rights reserved.

43 CFR 2091.5-3 - Segregative effect and opening: Emergency withdrawals.

Code of Federal Regulations, 2011 CFR

2011-10-01

... RULES Segregation and Opening of Lands § 2091.5-3 Segregative effect and opening: Emergency withdrawals... withdrawal unless segregation is effected by the publication in the Federal Register of a notice of a...

36 CFR 254.6 - Segregative effect.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 36 Parks, Forests, and Public Property 2 2010-07-01 2010-07-01 false Segregative effect. 254.6... ADJUSTMENTS Land Exchanges § 254.6 Segregative effect. (a) If a proposal is made to exchange Federal lands... segregative effect terminates as follows: (1) Automatically, upon issuance of a patent or other document of...

Mesoscale modeling of vacancy-mediated Si segregation near an edge dislocation in Ni under irradiation

NASA Astrophysics Data System (ADS)

Li, Zebo; Trinkle, Dallas R.

2017-04-01

We use a continuum method informed by transport coefficients computed using self-consistent mean field theory to model vacancy-mediated diffusion of substitutional Si solutes in FCC Ni near an a/2 [1 1 ¯0 ] (111 ) edge dislocation. We perform two sequential simulations: first under equilibrium boundary conditions and then under irradiation. The strain field around the dislocation induces heterogeneity and anisotropy in the defect transport properties and determines the steady-state vacancy and Si distributions. At equilibrium both vacancies and Si solutes diffuse to form Cottrell atmospheres with vacancies accumulating in the compressive region above the dislocation core while Si segregates to the tensile region below the core. Irradiation raises the bulk vacancy concentration, driving vacancies to flow into the dislocation core. The out-of-equilibrium vacancy fluxes drag Si atoms towards the core, causing segregation to the compressive region, despite Si being an oversized solute in Ni.

The effect of particle morphology on the physical stability of pharmaceutical powder mixtures

NASA Astrophysics Data System (ADS)

Swaminathan, Vidya

Pharmaceutical powder mixtures are composed of particles that physically interact, precluding the formation of random mixtures. Mixtures based on particle interactions are termed ordered mixtures. The objective of this study was to determine the effect of the morphological characteristics of the components, surface texture and shape, along with size, on the formation of stable mixtures. Morphological parameters were obtained from image analysis measurements. Surface roughness was quantified using the ratio of the perimeter of the particle to that of an ideal shape (circle or square) having the same area; shape was described using the aspect ratio. The stability of mixtures of micronized aspirin with carriers of different surface roughness was determined by measuring the extent of drug adhering to the carrier after subjecting the mixtures to vibration. A lesser extent of segregation of drug from highly textured carriers relative to smoother textured carriers was observed. This was postulated to be due to a larger concentration of surface asperities on the coarser carriers which constitute potentially strong adhesion sites. The electrostatic charge on the powders was measured; differences in the response of the mixtures to the addition of magnesium stearate were attributed to electrostatic charge effects. The effect of varying the aspect ratio of the carrier and drug on segregation in polydisperse mixtures was determined from the coefficient of variation of the drug in the mixture as a function of mixing time. Reducing the size of the carrier resulted in poor homogeneity due to weak carrier-drug interactions. The variation in drug content resulting from a change in the shape of the carriers was smaller than that caused by size differences. The segregation rate constant in mixtures having dissimilarly shaped components was larger than in mixtures having components of similar shape. The effects of magnesium stearate concentration and lubrication time on the content uniformity of polydisperse mixtures were evaluated from a full factorial experiment. The segregation response of ordered and random mixtures to the addition of magnesium stearate was compared. The moisture sorption behavior of commercial magnesium stearate and the resulting morphological changes were evaluated.

The joint effect of ethnicity and gender on occupational segregation. An approach based on the Mutual Information Index.

PubMed

Guinea-Martin, Daniel; Mora, Ricardo; Ruiz-Castillo, Javier

2015-01-01

In this article, we study the effects of ethnicity and gender on occupational segregation. Traditionally, researchers have examined the two sources of segregation separately. In contrast, we measure their joint effect by applying a multigroup segregation index-the Mutual Information or M index-to the product of the seven ethnic groups and two genders distinguished in our 2001 Census data for England and Wales. We exploit M's additive decomposability property to pose the following two questions: (i) Is there an interaction effect? (ii) How much does each source contribute to occupational segregation, controlling for the effect of the other? Although the role of ethnicity is non-negligible in the areas where minorities are concentrated, our findings confirm the greater importance of gender over ethnicity as a source of segregation. Moreover, we find a small "dwindling" interaction effect between the two sources of segregation: ethnicity slightly weakens the segregating power of gender and vice versa. Copyright © 2014 Elsevier Inc. All rights reserved.

Segregation effects during solidification in weightless melts

NASA Technical Reports Server (NTRS)

Li, C.

1973-01-01

Two types of melt segregation effects were studied: (1) evaporative segregation, or segregation due to surface evaporation; and (2) freezing segregation, or segregation due to liquid-solid phase transformation. These segregation effects are closely related. In fact, evaporative segregation always precedes freezing segregation to some degree and must often be studied prior to performing meaningful solidification experiments. This is particularly true since evaporation may cause the melt composition, at least at the critical surface regions or layers to be affected manyfold within seconds so that the surface region or layer melting point and other thermophysical properties, nucleation characteristics, base for undercooling, and critical velocity to avoid constitutional supercooling, may be completely unexpected. An important objective was, therefore, to develop the necessary normal evaporation equations for predicting the compositional changes within specified times at temperature and to correlate these equations with actual experimental data collected from the literature.

43 CFR 2091.7-2 - Segregative effect and opening: Taylor Grazing Act.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Segregative effect and opening: Taylor Grazing Act. 2091.7-2 Section 2091.7-2 Public Lands: Interior Regulations Relating to Public Lands... LAWS AND RULES Segregation and Opening of Lands § 2091.7-2 Segregative effect and opening: Taylor...

Increased segregation of brain networks in focal epilepsy: An fMRI graph theory finding.

PubMed

Pedersen, Mangor; Omidvarnia, Amir H; Walz, Jennifer M; Jackson, Graeme D

2015-01-01

Focal epilepsy is conceived of as activating local areas of the brain as well as engaging regional brain networks. Graph theory represents a powerful quantitative framework for investigation of brain networks. Here we investigate whether functional network changes are present in extratemporal focal epilepsy. Task-free functional magnetic resonance imaging data from 15 subjects with extratemporal epilepsy and 26 age and gender matched healthy controls were used for analysis. Local network properties were calculated using local efficiency, clustering coefficient and modularity metrics. Global network properties were assessed with global efficiency and betweenness centrality metrics. Cost-efficiency of the networks at both local and global levels was evaluated by estimating the physical distance between functionally connected nodes, in addition to the overall numbers of connections in the network. Clustering coefficient, local efficiency and modularity were significantly higher in individuals with focal epilepsy than healthy control subjects, while global efficiency and betweenness centrality were not significantly different between the two groups. Local network properties were also highly efficient, at low cost, in focal epilepsy subjects compared to healthy controls. Our results show that functional networks in focal epilepsy are altered in a way that the nodes of the network are more isolated. We postulate that network regularity, or segregation of the nodes of the networks, may be an adaptation that inhibits the conversion of the interictal state to seizures. It remains possible that this may be part of the epileptogenic process or an effect of medications.

Increased segregation of brain networks in focal epilepsy: An fMRI graph theory finding

PubMed Central

Pedersen, Mangor; Omidvarnia, Amir H.; Walz, Jennifer M.; Jackson, Graeme D.

2015-01-01

Focal epilepsy is conceived of as activating local areas of the brain as well as engaging regional brain networks. Graph theory represents a powerful quantitative framework for investigation of brain networks. Here we investigate whether functional network changes are present in extratemporal focal epilepsy. Task-free functional magnetic resonance imaging data from 15 subjects with extratemporal epilepsy and 26 age and gender matched healthy controls were used for analysis. Local network properties were calculated using local efficiency, clustering coefficient and modularity metrics. Global network properties were assessed with global efficiency and betweenness centrality metrics. Cost-efficiency of the networks at both local and global levels was evaluated by estimating the physical distance between functionally connected nodes, in addition to the overall numbers of connections in the network. Clustering coefficient, local efficiency and modularity were significantly higher in individuals with focal epilepsy than healthy control subjects, while global efficiency and betweenness centrality were not significantly different between the two groups. Local network properties were also highly efficient, at low cost, in focal epilepsy subjects compared to healthy controls. Our results show that functional networks in focal epilepsy are altered in a way that the nodes of the network are more isolated. We postulate that network regularity, or segregation of the nodes of the networks, may be an adaptation that inhibits the conversion of the interictal state to seizures. It remains possible that this may be part of the epileptogenic process or an effect of medications. PMID:26110111

Gravitational Acceleration Effects on Macrosegregation: Experiment and Computational Modeling

NASA Technical Reports Server (NTRS)

Leon-Torres, J.; Curreri, P. A.; Stefanescu, D. M.; Sen, S.

1999-01-01

Experiments were performed under terrestrial gravity (1g) and during parabolic flights (10-2 g) to study the solidification and macrosegregation patterns of Al-Cu alloys. Alloys having 2% and 5% Cu were solidified against a chill at two different cooling rates. Microscopic and Electron Microprobe characterization was used to produce microstructural and macrosegregation maps. In all cases positive segregation occurred next to the chill because shrinkage flow, as expected. This positive segregation was higher in the low-g samples, apparently because of the higher heat transfer coefficient. A 2-D computational model was used to explain the experimental results. The continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the solidification phenomena, for a two-phase system. The model considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The solidification event was divided into two stages. In the first one, the liquid containing freely moving equiaxed grains was described through the relative viscosity concept. In the second stage, when a fixed dendritic network was formed after dendritic coherency, the mushy zone was treated as a porous medium. The macrosegregation maps and the cooling curves obtained during experiments were used for validation of the solidification and segregation model. The model can explain the solidification and macrosegregation patterns and the differences between low- and high-gravity results.

Altered Brain Network Segregation in Fragile X Syndrome Revealed by Structural Connectomics.

PubMed

Bruno, Jennifer Lynn; Hosseini, S M Hadi; Saggar, Manish; Quintin, Eve-Marie; Raman, Mira Michelle; Reiss, Allan L

2017-03-01

Fragile X syndrome (FXS), the most common inherited cause of intellectual disability and autism spectrum disorder, is associated with significant behavioral, social, and neurocognitive deficits. Understanding structural brain network topology in FXS provides an important link between neurobiological and behavioral/cognitive symptoms of this disorder. We investigated the connectome via whole-brain structural networks created from group-level morphological correlations. Participants included 100 individuals: 50 with FXS and 50 with typical development, age 11-23 years. Results indicated alterations in topological properties of structural brain networks in individuals with FXS. Significantly reduced small-world index indicates a shift in the balance between network segregation and integration and significantly reduced clustering coefficient suggests that reduced local segregation shifted this balance. Caudate and amygdala were less interactive in the FXS network further highlighting the importance of subcortical region alterations in the neurobiological signature of FXS. Modularity analysis indicates that FXS and typically developing groups' networks decompose into different sets of interconnected sub networks, potentially indicative of aberrant local interconnectivity in individuals with FXS. These findings advance our understanding of the effects of fragile X mental retardation protein on large-scale brain networks and could be used to develop a connectome-level biological signature for FXS. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

A phase field model for segregation and precipitation induced by irradiation in alloys

NASA Astrophysics Data System (ADS)

Badillo, A.; Bellon, P.; Averback, R. S.

2015-04-01

A phase field model is introduced to model the evolution of multicomponent alloys under irradiation, including radiation-induced segregation and precipitation. The thermodynamic and kinetic components of this model are derived using a mean-field model. The mobility coefficient and the contribution of chemical heterogeneity to free energy are rescaled by the cell size used in the phase field model, yielding microstructural evolutions that are independent of the cell size. A new treatment is proposed for point defect clusters, using a mixed discrete-continuous approach to capture the stochastic character of defect cluster production in displacement cascades, while retaining the efficient modeling of the fate of these clusters using diffusion equations. The model is tested on unary and binary alloy systems using two-dimensional simulations. In a unary system, the evolution of point defects under irradiation is studied in the presence of defect clusters, either pre-existing ones or those created by irradiation, and compared with rate theory calculations. Binary alloys with zero and positive heats of mixing are then studied to investigate the effect of point defect clustering on radiation-induced segregation and precipitation in undersaturated solid solutions. Lastly, irradiation conditions and alloy parameters leading to irradiation-induced homogeneous precipitation are investigated. The results are discussed in the context of experimental results reported for Ni-Si and Al-Zn undersaturated solid solutions subjected to irradiation.

43 CFR 2091.5-4 - Segregative effect and opening: Water power withdrawals.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Segregative effect and opening: Water power withdrawals. 2091.5-4 Section 2091.5-4 Public Lands: Interior Regulations Relating to Public Lands... LAWS AND RULES Segregation and Opening of Lands § 2091.5-4 Segregative effect and opening: Water power...

43 CFR 2091.5-4 - Segregative effect and opening: Water power withdrawals.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Segregative effect and opening: Water power withdrawals. 2091.5-4 Section 2091.5-4 Public Lands: Interior Regulations Relating to Public Lands... LAWS AND RULES Segregation and Opening of Lands § 2091.5-4 Segregative effect and opening: Water power...

43 CFR 2091.5-4 - Segregative effect and opening: Water power withdrawals.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Segregative effect and opening: Water power withdrawals. 2091.5-4 Section 2091.5-4 Public Lands: Interior Regulations Relating to Public Lands... LAWS AND RULES Segregation and Opening of Lands § 2091.5-4 Segregative effect and opening: Water power...

A new computer-aided simulation model for polycrystalline silicon film resistors

NASA Astrophysics Data System (ADS)

Ching-Yuan Wu; Weng-Dah Ken

1983-07-01

A general transport theory for the I-V characteristics of a polycrystalline film resistor has been derived by including the effects of carrier degeneracy, majority-carrier thermionic-diffusion across the space charge regions produced by carrier trapping in the grain boundaries, and quantum mechanical tunneling through the grain boundaries. Based on the derived transport theory, a new conduction model for the electrical resistivity of polycrystalline film resitors has been developed by incorporating the effects of carrier trapping and dopant segregation in the grain boundaries. Moreover, an empirical formula for the coefficient of the dopant-segregation effects has been proposed, which enables us to predict the dependence of the electrical resistivity of phosphorus-and arsenic-doped polycrystalline silicon films on thermal annealing temperature. Phosphorus-doped polycrystalline silicon resistors have been fabricated by using ion-implantation with doses ranged from 1.6 × 10 11 to 5 × 10 15/cm 2. The dependence of the electrical resistivity on doping concentration and temperature have been measured and shown to be in good agreement with the results of computer simulations. In addition, computer simulations for boron-and arsenic-doped polycrystalline silicon resistors have also been performed and shown to be consistent with the experimental results published by previous authors.

Effective search for stable segregation configurations at grain boundaries with data-mining techniques

NASA Astrophysics Data System (ADS)

Kiyohara, Shin; Mizoguchi, Teruyasu

2018-03-01

Grain boundary segregation of dopants plays a crucial role in materials properties. To investigate the dopant segregation behavior at the grain boundary, an enormous number of combinations have to be considered in the segregation of multiple dopants at the complex grain boundary structures. Here, two data mining techniques, the random-forests regression and the genetic algorithm, were applied to determine stable segregation sites at grain boundaries efficiently. Using the random-forests method, a predictive model was constructed from 2% of the segregation configurations and it has been shown that this model could determine the stable segregation configurations. Furthermore, the genetic algorithm also successfully determined the most stable segregation configuration with great efficiency. We demonstrate that these approaches are quite effective to investigate the dopant segregation behaviors at grain boundaries.

Multi-way multi-group segregation and diversity indices.

PubMed

Gorelick, Root; Bertram, Susan M

2010-06-01

How can we compute a segregation or diversity index from a three-way or multi-way contingency table, where each variable can take on an arbitrary finite number of values and where the index takes values between zero and one? Previous methods only exist for two-way contingency tables or dichotomous variables. A prototypical three-way case is the segregation index of a set of industries or departments given multiple explanatory variables of both sex and race. This can be further extended to other variables, such as disability, number of years of education, and former military service. We extend existing segregation indices based on Euclidean distance (square of coefficient of variation) and Boltzmann/Shannon/Theil index from two-way to multi-way contingency tables by including multiple summations. We provide several biological applications, such as indices for age polyethism and linkage disequilibrium. We also provide a new heuristic conceptualization of entropy-based indices. Higher order association measures are often independent of lower order ones, hence an overall segregation or diversity index should be the arithmetic mean of the normalized association measures at all orders. These methods are applicable when individuals self-identify as multiple races or even multiple sexes and when individuals work part-time in multiple industries. The policy implications of this work are enormous, allowing people to rigorously test whether employment or biological diversity has changed.

The role of foraging behaviour in the sexual segregation of the African elephant.

PubMed

Shannon, Graeme; Page, Bruce R; Duffy, Kevin J; Slotow, Rob

2006-11-01

Elephants (Loxodonta africana) exhibit pronounced sexual dimorphism, and in this study we test the prediction that the differences in body size and sociality are significant enough to drive divergent foraging strategies and ultimately sexual segregation. Body size influences the foraging behaviour of herbivores through the differential scaling coefficients of metabolism and gut size, with larger bodied individuals being able to tolerate greater quantities of low-quality, fibrous vegetation, whilst having lower mass-specific energy requirements. We test two distinct theories: the scramble competition hypothesis (SCH) and the forage selection hypothesis (FSH). Comprehensive behavioural data were collected from the Pongola Game Reserve and the Phinda Private Game Reserve in South Africa over a 2.5-year period. The data were analysed using sex as the independent variable. Adult females targeted a wider range of species, adopted a more selective foraging approach and exhibited greater bite rates as predicted by the body size hypothesis and the increased demands of reproductive investment (lactation and pregnancy). Males had longer feeding bouts, displayed significantly more destructive behaviour (31% of observations, 11% for females) and ingested greater quantities of forage during each feeding bout. The independent ranging behaviour of adult males enables them to have longer foraging bouts as they experience fewer social constraints than females. The SCH was rejected as a cause of sexual segregation due to the relative abundance of low quality forage, and the fact that feeding heights were similar for both males and females. However, we conclude that the differences in the foraging strategies of the sexes are sufficient to cause spatial segregation as postulated by the FSH. Sexual dimorphism and the associated behavioural differences have important implications for the management and conservation of elephant and other dimorphic species, with the sexes effectively acting as distinct "ecological species".

43 CFR 2440.4 - Specific criteria for segregative effect of classification for disposal.

Code of Federal Regulations, 2011 CFR

2011-10-01

... of classification for disposal. 2440.4 Section 2440.4 Public Lands: Interior Regulations Relating to... (2000) SEGREGATION BY CLASSIFICATION Criteria for Segregation § 2440.4 Specific criteria for segregative effect of classification for disposal. Public lands classified or proposed to be classified for disposal...

43 CFR 2440.3 - Specific criteria for segregative effect of classification for retention.

Code of Federal Regulations, 2011 CFR

2011-10-01

... of classification for retention. 2440.3 Section 2440.3 Public Lands: Interior Regulations Relating to... (2000) SEGREGATION BY CLASSIFICATION Criteria for Segregation § 2440.3 Specific criteria for segregative effect of classification for retention. (a) Public lands classified or proposed to be classified for...

Segregation of large granules from close-packed cluster of small granules due to buoyancy.

PubMed

Yang, Xian-qing; Zhou, Kun; Qiu, Kang; Zhao, Yue-min

2006-03-01

Segregation of large granules in a vibrofluidized granular bed with inhomogeneous granular number density distribution is studied by an event-driven algorithm. Simulation results show that the mean vertical position of large granules decreases with the increase of the density ration of the large granules to the small ones. This conclusion is consistent with the explanation that the net pressure due to the small surrounding particle impacts balances the large granular weight, and indict that the upward movement of the large granules is driven by the buoyancy. The values of temperature, density, and pressure of the systems are also computed by changing the conditions such as heating temperature on the bottom and restitution coefficient of particles. These results indicate that the segregation of large granules also happen in the systems with density inversion or even close-packed cluster of particles floating on a low-density fluid, due to the buoyancy. An equation of state is proposed to explain the buoyancy.

43 CFR 2091.7-1 - Segregative effect and opening: Classifications.

Code of Federal Regulations, 2011 CFR

2011-10-01

...: Classifications. 2091.7-1 Section 2091.7-1 Public Lands: Interior Regulations Relating to Public Lands (Continued... RULES Segregation and Opening of Lands § 2091.7-1 Segregative effect and opening: Classifications. (a)(1... authority of the Classification and Multiple Use Act (43 U.S.C. 1411-18) are segregated to the extent...

Quality-by-design (QbD): effects of testing parameters and formulation variables on the segregation tendency of pharmaceutical powder measured by the ASTM D 6940-04 segregation tester.

PubMed

Xie, Lin; Wu, Huiquan; Shen, Meiyu; Augsburger, Larry L; Lyon, Robbe C; Khan, Mansoor A; Hussain, Ajaz S; Hoag, Stephen W

2008-10-01

The objective of this study was to examine the effects of testing parameters and formulation variables on the segregation tendency of pharmaceutical powders measured by the ASTM D 6940-04 segregation tester using design of experiments (DOE) approaches. The test blends consisted of 4% aspirin (ASP) and 96% microcrystalline cellulose (MCC) with and without magnesium stearate (MgS). The segregation tendency of a blend was determined by measuring the last/first (L/F) ratio, the ratio of aspirin concentrations between the first and last samples discharged from the tester. A 2(2) factorial design was used to determine the effects of measurement parameters [amount of material loaded (W), number of segregation cycles] with number of replicates 6. ANOVA showed that W was a critical parameter for segregation testing. The L/F value deviated further from 1 (greater segregation tendency) with increasing W. A 2(3) full factorial design was used to assess the effects of formulation variables: grade of ASP (unmilled, milled), grade of MCC, and amount of lubricant, MgS. MLR and ANOVA showed that the grade of ASP was the main effect contributing to segregation tendency. Principal Component Regression Analysis established a correlation between L/F and the physical properties of the blend related to ASP and MCC, the ASP/MCC particle size ratio (PSR) and powder cohesion. The physical properties of the blend related to density and flow were not influenced by the grade of ASP and were not related to the segregation tendency of the blend. The direct relationship between L/F and PSR was determined by univariate analysis. Segregation tendency increased as the ASP to MCC particle size increased. This study highlighted critical test parameters for segregation testing and identified critical physical properties of the blends that influence segregation tendency. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

77 FR 7601 - Notice of Segregation of Public Lands for the Pattern Energy Group Ocotillo Express Wind Energy...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-13

... LVRWB10B3980] Notice of Segregation of Public Lands for the Pattern Energy Group Ocotillo Express Wind Energy...) application for the Ocotillo Express Wind Project. The public land contained in this segregation totals approximately 12,436 acres. DATES: Effective Date: This segregation is effective on February 13, 2012. FOR...

Development of a robust modeling tool for radiation-induced segregation in austenitic stainless steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ying; Field, Kevin G; Allen, Todd R.

2015-09-01

Irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels in Light Water Reactor (LWR) components has been linked to changes in grain boundary composition due to irradiation induced segregation (RIS). This work developed a robust RIS modeling tool to account for thermodynamics and kinetics of the atom and defect transportation under combined thermal and radiation conditions. The diffusion flux equations were based on the Perks model formulated through the linear theory of the thermodynamics of irreversible processes. Both cross and non-cross phenomenological diffusion coefficients in the flux equations were considered and correlated to tracer diffusion coefficients through Manning’s relation. Themore » preferential atomvacancy coupling was described by the mobility model, whereas the preferential atom-interstitial coupling was described by the interstitial binding model. The composition dependence of the thermodynamic factor was modeled using the CALPHAD approach. Detailed analysis on the diffusion fluxes near and at grain boundaries of irradiated austenitic stainless steels suggested the dominant diffusion mechanism for chromium and iron is via vacancy, while that for nickel can swing from the vacancy to the interstitial dominant mechanism. The diffusion flux in the vicinity of a grain boundary was found to be greatly influenced by the composition gradient formed from the transient state, leading to the oscillatory behavior of alloy compositions in this region. This work confirms that both vacancy and interstitial diffusion, and segregation itself, have important roles in determining the microchemistry of Fe, Cr, and Ni at irradiated grain boundaries in austenitic stainless steels.« less

Effect of accelerated crucible rotation on the segregation of impurities in vertical Bridgman growth of multi-crystalline silicon

NASA Astrophysics Data System (ADS)

Bellmann, M. P.; Meese, E. A.; Arnberg, L.

2011-03-01

We have performed axisymmetric, transient simulations of the vertical Bridgman growth of mc-silicon to study the effect of the accelerated crucible rotation technique (ACRT) on the melt flow and impurity segregation. A solute transport model has been applied to predict the final segregation pattern of impurities in a circular ingot. The sinusoidal ACRT rotation cycle considered here suppresses mixing in the melt near the center, resulting in diffusion-limited mass transport. Therefore the radial impurity segregation is increased towards the center. The effect of increased radial segregation is intensified for low values of the Ekman time scale.

Neighborhood residential segregation and mental health: a multilevel analysis on Hispanic Americans in Chicago.

PubMed

Lee, Min-Ah

2009-06-01

Compared with the relationship between neighborhood-level residential segregation and physical health of Hispanic Americans, less is known about how neighborhood residential segregation affects mental health. This study examines if, and how, neighborhood residential segregation is associated with the mental health of Puerto Rican and Mexican Americans in Chicago. Multilevel analyses reveal that neighborhood residential segregation is positively associated with depressive symptoms and anxiety in both groups. Neighborhood segregation, however, has more salient effects on the mental health of Mexican Americans. For Puerto Rican Americans, the effects of neighborhood segregation on mental health become nonsignificant after controlling for neighborhood-level income and individual-level covariates, whereas neighborhood segregation is strongly associated with the mental health of Mexican Americans even after controlling for other covariates. These findings show that living in a Mexican American-dominated community is not beneficial to mental health, in contrast to findings for physical health shown in previous studies.

Neighborhood residential segregation and physical health among Hispanic Americans: good, bad, or benign?

PubMed

Lee, Min-Ah; Ferraro, Kenneth F

2007-06-01

Although considerable evidence shows that residential segregation is deleterious to the health of African Americans, findings regarding segregation and health for Hispanic Americans are inconsistent. Competing hypotheses regarding the effects of neighborhood segregation on health are tested with data from Puerto Rican and Mexican American residents of Chicago. Multilevel analyses reveal that segregation is associated with more health problems for Puerto Rican Americans but not for Mexican Americans. In addition, the relationship between segregation and health was conditioned by generational status for Mexican Americans: Second- or later-generation Mexican Americans living in highly segregated neighborhoods had better health than first-generation Mexican Americans in such neighborhoods. These findings reveal that residential segregation has differential effects across Hispanic groups and suggest that a high degree of contact with Mexican Americans promotes health by facilitating flow of informal health resources and social support.

Analysis of Minor Component Segregation in Ternary Powder Mixtures

NASA Astrophysics Data System (ADS)

Asachi, Maryam; Hassanpour, Ali; Ghadiri, Mojtaba; Bayly, Andrew

2017-06-01

In many powder handling operations, inhomogeneity in powder mixtures caused by segregation could have significant adverse impact on the quality as well as economics of the production. Segregation of a minor component of a highly active substance could have serious deleterious effects, an example is the segregation of enzyme granules in detergent powders. In this study, the effects of particle properties and bulk cohesion on the segregation tendency of minor component are analysed. The minor component is made sticky while not adversely affecting the flowability of samples. The segregation extent is evaluated using image processing of the photographic records taken from the front face of the heap after the pouring process. The optimum average sieve cut size of components for which segregation could be reduced is reported. It is also shown that the extent of segregation is significantly reduced by applying a thin layer of liquid to the surfaces of minor component, promoting an ordered mixture.

Residential Segregation and Racial Cancer Disparities: A Systematic Review.

PubMed

Landrine, Hope; Corral, Irma; Lee, Joseph G L; Efird, Jimmy T; Hall, Marla B; Bess, Jukelia J

2017-12-01

This paper provides the first review of empirical studies of segregation and black-white cancer disparities. We searched all years of PubMed (through May 2016) using these terms: racial segregation, residential segregation, neighborhood racial composition (first terms) and (second terms) cancer incidence, mortality, survival, stage at diagnosis, screening. The 17 (of 668) articles that measured both segregation and a cancer outcome were retained. Segregation contributed significantly to cancer and to racial cancer disparities in 70% of analyses, even after controlling for socioeconomic status and health insurance. Residing in segregated African-American areas was associated with higher odds of later-stage diagnosis of breast and lung cancers, higher mortality rates and lower survival rates from breast and lung cancers, and higher cumulative cancer risks associated with exposure to ambient air toxics. There were no studies of many types of cancer (e.g., cervical). Studies differed in their measure of segregation, and 40% used an invalid measure. Possible mediators of the segregation effect usually were not tested. Empirical analysis of segregation and racial cancer disparities is a recent area of research. The literature is limited to 17 studies that focused primarily on breast cancer. Studies differed in their measure of segregation, yet segregation nonetheless contributed to cancer and to racial cancer disparities in 70% of analyses. This suggests the need for further research that uses valid measures of segregation, examines a variety of types of cancers, and explores the variables that may mediate the segregation effect.

Effect of steady crucible rotation on the segregation of impurities in vertical Bridgman growth of multi-crystalline silicon

NASA Astrophysics Data System (ADS)

Bellmann, M. P.; Meese, E. A.

2011-10-01

We have performed axisymmetric, transient simulations of the vertical Bridgman growth of multi-crystalline (mc) silicon to study the effect of the steady crucible rotation on the melt flow and impurity segregation. A solute transport model has been applied to predict the final segregation pattern of impurities in a circular ingot. Imposing rotation rates of 1-5 rpm on the system makes radial segregation much worse compared to the non-rotating case. Low rotation rates at 1-2 rpm increase radial segregation in the first half period of solidification, whereas at rotation rates above the effect is insignificantly small. Contrary behavior was observed for the second half period of solidification. Here radial segregation is increased at high rotation rates from 3 to 5 rpm with small impact at 1-2 rpm.

Advanced methods for preparation and characterization of infrared detector materials. [mercury cadmium tellurides

NASA Technical Reports Server (NTRS)

Lehoczky, S. L.; Szofran, F. R.; Martin, B. G.

1980-01-01

Mercury cadmium telluride crystals were prepared by the Bridgman method with a wide range of crystal growth rates and temperature gradients adequate to prevent constitutional supercooling under diffusion-limited, steady state, growth conditions. The longitudinal compositional gradients for different growth conditions and alloy compositions were calculated and compared with experimental data to develop a quantitative model of the crystal growth kinetics for the Hg(i-x)CdxTe alloys, and measurements were performed to ascertain the effect of growth conditions on radial compositional gradients. The pseudobinary HgTe-CdTe constitutional phase diagram was determined by precision differential thermal analysis measurements and used to calculate the segregation coefficient of Cd as a function of x and interface temperature. Computer algorithms specific to Hg(1-x)CdxTe were developed for calculations of the charge carrier concentrations, charge carrier mobilities, Hall coefficient, optical absorptance, and Fermi energy as functions of x, temperature, ionized donor and acceptor concentrations, and neutral defect concentrations.

Residential Segregation and School Integration.

ERIC Educational Resources Information Center

Rivkin, Steven G.

1994-01-01

Asserts that school districts' efforts to integrate schools have failed to ameliorate the racial isolation of black students. Finds that schools remain segregated primarily because of continued residential segregation and that school integration efforts have had little long-term effect on residential segregation. (CFR)

The Effect of Strict Segregation on Pseudomonas aeruginosa in Cystic Fibrosis Patients

PubMed Central

van Mansfeld, Rosa; de Vrankrijker, Angelica; Brimicombe, Roland; Heijerman, Harry; Teding van Berkhout, Ferdinand; Spitoni, Cristian; Grave, Sanne; van der Ent, Cornelis; Wolfs, Tom; Willems, Rob; Bonten, Marc

2016-01-01

Introduction Segregation of patients with cystic fibrosis (CF) was implemented to prevent chronic infection with epidemic Pseudomonas aeruginosa strains with presumed detrimental clinical effects, but its effectiveness has not been carefully evaluated. Methods The effect of strict segregation on the incidence of P. aeruginosa infection in CF patients was investigated through longitudinal protocolized follow-up of respiratory tract infection before and after segregation. In two nested cross-sectional studies in 2007 and 2011 the P. aeruginosa population structure was investigated and clinical parameters were determined in patients with and without infection with the Dutch epidemic P. aeruginosa clone (ST406). Results Of 784 included patients 315 and 382 were at risk for acquiring chronic P. aeruginosa infection before and after segregation. Acquisition rates were, respectively, 0.14 and 0.05 per 1,000 days at risk (HR: 0.66, 95% CI [0.2548–1.541]; p = 0.28). An exploratory subgroup analysis indicated lower acquisition after segregation in children < 15 years of age (HR: 0.43, 95% CI[0.21–0.95]; p = 0.04). P. aeruginosa population structure did not change after segregation and ST406 was not associated with lung function decline, death or lung transplantation. Conclusions Strict segregation was not associated with a statistically significant lower acquisition of chronic P. aeruginosa infection and ST406 was not associated with adverse clinical outcome. After segregation there were no new acquisitions of ST406. In an unplanned exploratory analysis chronic acquisition of P. aeruginosa was lower after implementation of segregation in patients under 15 years of age. PMID:27280467

43 CFR 2462.4 - Segregative effect of publication.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Segregative effect of publication. 2462.4... Disposal Classification Procedure: Over 2,560 Acres § 2462.4 Segregative effect of publication. (a) Publication in the Federal Register of a notice of proposed classification pursuant to § 2462.1 or of a notice...

Residential segregation and the survival of U.S. urban public hospitals.

PubMed

Ko, Michelle; Needleman, Jack; Derose, Kathryn Pitkin; Laugesen, Miriam J; Ponce, Ninez A

2014-06-01

Residential segregation is associated geographic disparities in access to care, but its impact on local health care policy, including public hospitals, is unknown. We examined the effects of racial residential segregation on U.S. urban public hospital closures from 1987 to 2007, controlling for hospital, market, and policy characteristics. We found that a high level of residential segregation moderated the protective effects of Black population composition, such that a high level of residential segregation, in combination with a high percentage of poor residents, conferred a higher likelihood of hospital closure. More segregated and poorer communities face disadvantages in access to care that may be compounded as a result of instability in the health care safety net. Policy makers should consider the influence of social factors such as residential segregation on the allocation of the safety net resources.

76 FR 2705 - Notice of Realty Action; Modification of the Segregative Effect of Recreation and Public Purposes...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-14

... action will modify the segregation to open the lands only to effect this exchange. FOR FURTHER... lease on November 3, 1978, and published in the Federal Register (62 FR 9446) which included segregation...

Silicon Materials Task of the Low Cost Solar Array Project, Phase 3. Effect of Impurities and Processing on Silicon Solar Cells

NASA Technical Reports Server (NTRS)

Hopkins, R. H.; Davis, J. R.; Blais, P. D.; Rohatgi, A.; Campbell, R. B.; Rai-Choudhury, P.; Stapleton, R. E.; Mollenkopf, H. C.; Mccormick, J. R.

1979-01-01

The effects of impurities, various thermochemical processes, and any impurity process interactions on the performance of terrestrial silicon solar cells are defined. Determinations of the segregation coefficients of tungsten, tantalum, and cobalt for the Czochralski pulling of silicon single crystals are reported. Sensitive neutron activation analysis was used to determine the metal impurity content of the silicon while atomic absorption was used to measure the metal content of the residual liquid from which the doped crystals were grown. Gettering of Ti doped silicon wafers improved cell performance by one to two percent for the highest temperatures and longest times. The HCl is more effective than POCl3 treatments for deactivating Ti but POCl3 and HCl produced essentially identical results for Mo or Fe.

Influence of the "surface effect" on the segregation parameters of S in Fe(100): A multi-scale modelling and Auger Electron Spectroscopy study

NASA Astrophysics Data System (ADS)

Barnard, P. E.; Terblans, J. J.; Swart, H. C.

2015-12-01

The article takes a new look at the process of atomic segregation by considering the influence of surface relaxation on the segregation parameters; the activation energy (Q), segregation energy (ΔG), interaction parameter (Ω) and the pre-exponential factor (D0). Computational modelling, namely Density Functional Theory (DFT) and the Modified Darken Model (MDM) in conjunction with Auger Electron Spectroscopy (AES) was utilized to study the variation of the segregation parameters for S in the surface region of Fe(100). Results indicate a variation in each of the segregation parameters as a function of the atomic layer under consideration. Values of the segregation parameters varied more dramatically as the surface layer is approached, with atomic layer 2 having the largest deviations in comparison to the bulk values. This atomic layer had the highest Q value and formed the rate limiting step for the segregation of S towards the Fe(100) surface. It was found that the segregation process is influenced by two sets of segregation parameters, those of the surface region formed by atomic layer 2, and those in the bulk material. This article is the first to conduct a full scale investigation on the influence of surface relaxation on segregation and labelled it the "surface effect".

Purification of selenium by zone refining

NASA Astrophysics Data System (ADS)

Burger, A.; Henderson, D. O.; Morgan, S. H.; Feng, J.; Silberman, E.

1990-11-01

We studied the purification of Se using zone refining, with emphasis on the efficiency of this technique in removing the Cu impurity, which is known to be related to a trapping center in CdSe. After 78 passes it was found that Cu accumulates at one end section of the ingot, while at the opposite end the level was below the detection limit of the atomic absorption spectroscopic analysis employed. Infrared spectroscopic data, differential solubility and differential scanning calorimetry measurements also indicate that the effective distribution coefficient, k, for the Cu solute, is less than 1. A model for the various phases present during zone melting is presented and the possibility of segregating impurities having k>1 is discussed.

Distribution of fixed beneficial mutations and the rate of adaptation in asexual populations

PubMed Central

Good, Benjamin H.; Rouzine, Igor M.; Balick, Daniel J.; Hallatschek, Oskar; Desai, Michael M.

2012-01-01

When large asexual populations adapt, competition between simultaneously segregating mutations slows the rate of adaptation and restricts the set of mutations that eventually fix. This phenomenon of interference arises from competition between mutations of different strengths as well as competition between mutations that arise on different fitness backgrounds. Previous work has explored each of these effects in isolation, but the way they combine to influence the dynamics of adaptation remains largely unknown. Here, we describe a theoretical model to treat both aspects of interference in large populations. We calculate the rate of adaptation and the distribution of fixed mutational effects accumulated by the population. We focus particular attention on the case when the effects of beneficial mutations are exponentially distributed, as well as on a more general class of exponential-like distributions. In both cases, we show that the rate of adaptation and the influence of genetic background on the fixation of new mutants is equivalent to an effective model with a single selection coefficient and rescaled mutation rate, and we explicitly calculate these effective parameters. We find that the effective selection coefficient exactly coincides with the most common fixed mutational effect. This equivalence leads to an intuitive picture of the relative importance of different types of interference effects, which can shift dramatically as a function of the population size, mutation rate, and the underlying distribution of fitness effects. PMID:22371564

Residential segregation, dividing walls and mental health: a population-based record linkage study.

PubMed

Maguire, Aideen; French, Declan; O'Reilly, Dermot

2016-09-01

Neighbourhood segregation has been described as a fundamental determinant of physical health, but literature on its effect on mental health is less clear. While most previous research has relied on conceptualised measures of segregation, Northern Ireland is unique as it contains physical manifestations of segregation in the form of segregation barriers (or 'peacelines') which can be used to accurately identify residential segregation. We used population-wide health record data on over 1.3 million individuals, to analyse the effect of residential segregation, measured by both the formal Dissimilarity Index and by proximity to a segregation barrier, on the likelihood of poor mental health. Using multilevel logistic regression models, we found residential segregation measured by the Dissimilarity Index poses no additional risk to the likelihood of poor mental health after adjustment for area-level deprivation. However, residence in an area segregated by a 'peaceline' increases the likelihood of antidepressant medication by 19% (OR=1.19, 95% CI 1.14 to 1.23) and anxiolytic medication by 39% (OR=1.39, 95% CI 1.32 to 1.48), even after adjustment for gender, age, conurbation, deprivation and crime. Living in an area segregated by a 'peaceline' is detrimental to mental health suggesting segregated areas characterised by a heightened sense of 'other' pose a greater risk to mental health. The difference in results based on segregation measure highlights the importance of choice of measure when studying segregation. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Long prereproductive selection and divergence by depth in a Caribbean candelabrum coral

PubMed Central

Prada, Carlos; Hellberg, Michael E.

2013-01-01

Long-lived corals, the foundation of modern reefs, often follow ecological gradients, so that populations or sister species segregate by habitat. Adaptive divergence maintains sympatric congeners after secondary contact or may even generate species by natural selection in the face of gene flow. Such ecological divergence, initially between alternative phenotypes within populations, may be aided by immigrant inviability, especially when a long period separates larval dispersal and the onset of reproduction, during which selection can sort lineages to match different habitats. Here, we evaluate the strength of one ecological factor (depth) to isolate populations by comparing the genes and morphologies of pairs of depth-segregated populations of the candelabrum coral Eunicea flexuosa across the Caribbean. Eunicea is endemic to the Caribbean and all sister species co-occur. Eunicea flexuosa is widespread both geographically and across reef habitats. Our genetic analysis revealed two depth-segregated lineages. Field survivorship data, combined with estimates of selection coefficients based on transplant experiments, suggest that selection is strong enough to segregate these two lineages. Genetic exchange between the Shallow and Deep lineages occurred either immediately after divergence or the two have diverged with gene flow. Migration occurs asymmetrically from the Shallow to Deep lineage. Limited recruitment to reproductive age, even under weak annual selection advantage, is sufficient to generate habitat segregation because of the cumulative prolonged prereproductive selection. Ecological factors associated with depth can act as filters generating strong barriers to gene flow, altering morphologies, and contributing to the potential for speciation in the sea. PMID:23359716

The Integration Anomaly: Comparing the Effects of K-12 Education Delivery Models on Segregation in Schools

ERIC Educational Resources Information Center

Scafidi, Benjamin

2015-01-01

To shed light on the actual impact of school choice on segregation, one has to understand the counter factual--the state of segregation under the current public education system. In the late 1960s and '70s, the trend in public school racial segregation followed the trend in neighborhood segregation. That is to say both improved as American…

Effects of Space Environment on Flow and Concentration During Directional Solidification

NASA Technical Reports Server (NTRS)

Benjapiyaporn, C.; Timchenko, V.; Leonardi, E.; deVahlDavis, G.; deGroh, H. C., III

2000-01-01

A study of directional solidification of a weak binary alloy (specifically, Bi - 1 at% Sn) based on the fixed grid single domain approach is being undertaken. The enthalpy method is used to solve for the temperature field over the computational domain including both the solid and liquid phases; latent heat evolution is treated with the aid of an effective specific heat coefficient. A source term accounting for the release of solute into the liquid during solidification has been incorporated into the solute transport equation. The vorticity-stream function formulation is used to describe thermosolutal convection in the liquid region. In this paper we numerically investigate the effects of g-jitter on directional solidification. A background gravity of 1 micro-g has been assumed, and new results for the effects of periodic disturbances over a range of amplitudes and frequencies on solute field and segregation have been presented.

Residential segregation and the health of African-American infants: does the effect vary by prevalence?

PubMed

Nyarko, Kwame A; Wehby, George L

2012-10-01

Segregation effects may vary between areas (e.g., counties) of low and high low birth weight (LBW; <2,500 g) and preterm birth (PTB; <37 weeks of gestation) rates due to interactions with area differences in risks and resources. We assess whether the effects of residential segregation on county-level LBW and PTB rates for African-American infants vary by the prevalence of these conditions. The study sample includes 368 counties of 100,000 or more residents and at least 50 African-American live births in 2000. Residentially segregated counties are identified alternatively by county-level dissimilarity and isolation indices. Quantile regression is used to assess how residential segregation affects the entire distributions of county-level LBW and PTB rates (i.e. by prevalence). Residential segregation increases LBW and PTB rates significantly in areas of low prevalence, but has no such effects for areas of high prevalence. As a sensitivity analysis, we use metropolitan statistical area level data and obtain similar results. Our findings suggest that residential segregation has adverse effects mainly in areas of low prevalence of LBW and preterm birth, which are expected overall to have fewer risk factors and more resources for infant health, but not in high prevalence areas, which are expected to have more risk factors and fewer resources. Residential policies aimed at area resource improvements may be more effective.

Neighborhood Residential Segregation and Physical Health among Hispanic Americans: Good, Bad, or Benign?

ERIC Educational Resources Information Center

Lee, Min-Ah; Ferraro, Kenneth F.

2007-01-01

Although considerable evidence shows that residential segregation is deleterious to the health of African Americans, findings regarding segregation and health for Hispanic Americans are inconsistent. Competing hypotheses regarding the effects of neighborhood segregation on health are tested with data from Puerto Rican and Mexican American…

Effect of steady crucible rotation on segregation in high-pressure vertical Bridgman growth of cadmium zinc telluride

NASA Astrophysics Data System (ADS)

Yeckel, Andrew; Patrick Doty, F.; Derby, Jeffrey J.

1999-05-01

Three-dimensional axisymmetric, time-dependent simulations of the high-pressure vertical Bridgman growth of large-diameter cadmium zinc telluride are performed to study the effect of steady crucible rotation on axial and radial segregation in the grown crystal. The model includes details of heat transfer, melt convection, solid-liquid interface shape, and pseudo-binary zinc segregation. Imposing a moderate rotation rate of 10 rpm on the system slightly improves axial segregation but makes radial segregation much worse. Moreover, values of dimensionless thermal Rossby and Taylor numbers calculated for this system indicate that the baroclinic instability may occur at the rotation rates studied.

DNA and origin region segregation are not affected by the transition from rod to sphere after inhibition of Escherichia coli MreB by A22.

PubMed

Karczmarek, Aneta; Martínez-Arteaga, Rocío; Baselga, Rocío Martínez-Arteaga; Alexeeva, Svetlana; Hansen, Flemming G; Vicente, Miguel; Nanninga, Nanne; den Blaauwen, Tanneke

2007-07-01

The bacterial actin homologue MreB forms a helix underneath the cytoplasmic membrane and was shown to be essential in the morphogenesis of the rod-shaped cells. Additionally, MreB was implicated to be involved in DNA segregation. However, in our hands the mreBCD deletion strain (PA340-678) grew without apparent DNA segregation defect, suggesting that the reported chromosome segregation inhibition could be caused by a temporarily effect of MreB inhibition or depletion. To assess the involvement of MreB in DNA segregation during the transition from rod to sphere, we compared the effect of A22 and the PBP2 inhibitor mecillinam on the percentage of cells with segregated nucleoids and the number of oriC foci in wild-type Escherichia coli cells. Cells became spherical in the same time window during both treatments and we could not detect any difference in the chromosome or oriC segregation between these two treatments. Additionally, flow cytometric analyses showed that A22 and mecillinam treatment gave essentially the same chromosome segregation pattern. We conclude that MreB is not directly involved in DNA segregation of E. coli.

Self-rated health and residential segregation: how does race/ethnicity matter?

PubMed

Gibbons, Joseph; Yang, Tse-Chuan

2014-08-01

Despite recent declines, racial segregation remains a detriment to minority neighborhoods. However, existing research is inconclusive as to the effects racial segregation has on health. Some argue that racial segregation is related to poor health outcomes, whereas others suspect that racial segregation may actually lead to improved health for some minority communities. Even less is known about whether minority access to white neighborhoods improves health. We address these gaps with individual data from the 2010 Public Health Management Corporation's Southeastern Pennsylvania Household Health Survey and census tract data from the 2010 Decennial Census and the 2006-2010 American Community Survey. We implement logistic multilevel models to determine whether and how a resident's self-rated health is affected by the racial/ethnic segregation of their neighborhoods. Our key finding suggests that the effects of segregation on self-rated health depend on an individual's race/ethnicity, with blacks and Latino residents most likely to experience adverse effects. Particularly, minorities living in predominantly white communities have a significantly higher likelihood to report poor/fair health than they would in segregated minority neighborhoods. These findings make clear that access to white neighborhoods is not sufficient to improve minority health; fuller neighborhood integration is necessary to ensure all have health equity.

PROGRESS AND PROBLEMS FROM THE SOCIAL SCIENTIST'S VIEWPOINT.

ERIC Educational Resources Information Center

CLARK, KENNETH

REVIEWED FROM A SOCIAL SCIENTIST'S VIEWPOINT IS THE EFFECT OF THE SUPREME COURT'S 1954 BROWN DECISION ON PATTERNS OF DEFACTO SEGREGATION IN NORTHERN COMMUNITIES. THE DECISION HAD PROFOUND EFFECTS ON DE FACTO SEGREGATION, PARTICULARLY IN RELATION TO THE DEMOCRATIC IDEALS OF EQUALITY AND TO THE DAMAGED SELF-IMAGE CREATED BY SEGREGATED SCHOOLS. IT…

Structure and Dynamics of Confined Alcohol-Water Mixtures.

PubMed

Bampoulis, Pantelis; Witteveen, Jorn P; Kooij, E Stefan; Lohse, Detlef; Poelsema, Bene; Zandvliet, Harold J W

2016-07-26

The effect of confinement between mica and graphene on the structure and dynamics of alcohol-water mixtures has been studied in situ and in real time at the molecular level by atomic force microscopy (AFM) at room temperature. AFM images reveal that the adsorbed molecules are segregated into faceted alcohol-rich islands on top of an ice layer on mica, surrounded by a pre-existing multilayer water-rich film. These faceted islands are in direct contact with the graphene surface, revealing a preferred adsorption site. Moreover, alcohol adsorption at low relative humidity (RH) reveals a strong preference of the alcohol molecules for the ordered ice interface. The growth dynamics of the alcohol islands is governed by supersaturation, temperature, the free energy of attachment of molecules to the island edge and two-dimensional (2D) diffusion. The measured diffusion coefficients display a size dependence on the molecular size of the alcohols, and are about 6 orders of magnitude smaller than the bulk diffusion coefficients, demonstrating the effect of confinement on the behavior of the alcohols. These experimental results provide new insights into the behavior of multicomponent fluids in confined geometries, which is of paramount importance in nanofluidics and biology.

Sound segregation via embedded repetition is robust to inattention.

PubMed

Masutomi, Keiko; Barascud, Nicolas; Kashino, Makio; McDermott, Josh H; Chait, Maria

2016-03-01

The segregation of sound sources from the mixture of sounds that enters the ear is a core capacity of human hearing, but the extent to which this process is dependent on attention remains unclear. This study investigated the effect of attention on the ability to segregate sounds via repetition. We utilized a dual task design in which stimuli to be segregated were presented along with stimuli for a "decoy" task that required continuous monitoring. The task to assess segregation presented a target sound 10 times in a row, each time concurrent with a different distractor sound. McDermott, Wrobleski, and Oxenham (2011) demonstrated that repetition causes the target sound to be segregated from the distractors. Segregation was queried by asking listeners whether a subsequent probe sound was identical to the target. A control task presented similar stimuli but probed discrimination without engaging segregation processes. We present results from 3 different decoy tasks: a visual multiple object tracking task, a rapid serial visual presentation (RSVP) digit encoding task, and a demanding auditory monitoring task. Load was manipulated by using high- and low-demand versions of each decoy task. The data provide converging evidence of a small effect of attention that is nonspecific, in that it affected the segregation and control tasks to a similar extent. In all cases, segregation performance remained high despite the presence of a concurrent, objectively demanding decoy task. The results suggest that repetition-based segregation is robust to inattention. (c) 2016 APA, all rights reserved).

Segregation and microstructure evolution in chill cast and directionally solidified Ni-Mn-Sn metamagnetic shape memory alloys

NASA Astrophysics Data System (ADS)

Czaja, P.; Wierzbicka-Miernik, A.; Rogal, Ł.

2018-06-01

A multiphase solidification behaviour is confirmed for a range of Ni-rich and Ni-deficient Ni-Mn-Sn induction cast and directionally solidified (Bridgman) alloys. The composition variation is primarily linked to the changing Mn/Sn ratio, whereas the content of Ni remains largely stable. The partitioning coefficients for the Ni50Mn37Sn13 and Ni46Mn41.5Sn12.5 Bridgman alloys were obtained according to the Scheil equation based on the composition distribution along the longitudinal cross section of the ingots. Homogenization heat treatment performed for 72 h at 1220 K turned out sufficient for ensuring chemical uniformity on the macro- and microscale. It is owed to a limited segregation length scale due to slow cooling rates adopted for the directional solidification process.

43 CFR 2091.5-4 - Segregative effect and opening: Water power withdrawals.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Segregative effect and opening: Water power withdrawals. 2091.5-4 Section 2091.5-4 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Segregation and Opening of...

The effect of segregation on the austemper transformation and toughness of ductile irons

NASA Astrophysics Data System (ADS)

Lin, B. Y.; Chen, E. T.; Lei, T. S.

1998-06-01

The effect of segregation of alloying elements on the phase transformation of ductile iron during austempering was investigated. Four heats, each containing 0.4%Mn, 1% Cu, 1.5% Ni, or 0.4% Mo (wt%) separately, were melted; then three different sizes of casting bars (3,15, and 75 mm diameter) were poured from each heat. The distribution and the degree of segregation of certain elements were quantitatively analyzed using an electron microprobe. A personal computer (PC)-controlled heat treating system was used to measure electrical resistivity, and the information on resistivity variations was used to analyze the effect of segregation on phase transformations during austempering. Also, Charpy impact and Rockwell hardness tests were performed to determine the effect of segregation on properties. Results of the electron microprobe analysis showed that the degree of segregation of alloy elements increases with an increase in diameter of the casting bars (i.e., an increase of solidification time of castings). The degree of segregation of alloy elements, represented by segregation ratio (SR) (the maximum concentration of element in cell divided by the minimum concentration of element in cell), varied linearly with the casting modulus (M) (volume of casting divided by surface area of casting). Regarding the segregating tendency among alloy elements, positive segregating elements Mn and Mo showed more segregation than the negative segregating elements Si, Cu, and Ni. In addition, segregation of Mo was more significant than Mn, and that for Cu was greater than Ni and Si. Between the time of finishing the first stage and beginning the second stage of bainite reaction in ductile irons, there is a significant “processing window,” At;, for austempering to obtain optimum mechanical properties. From the electrical resistivity data, it was observed that the austempering temperature plays a major role in the processing window. There was a narrow window at 400 ‡C but a larger one at 350 ‡C. Additionally, the microsegregation of alloying elements led to variation of the time of phase transformation for various regions in the grain cells of ductile iron which caused the processing window to decrease. The span of the processing window decreased with an increase in degree of segregation. There was no significant difference in the hardness of the alloys in various diameter specimens. However, the impact toughness was significantly affected by the segregation. The impact values in 15 mm specimens with less degree of segregation were greater than those in 75 mm specimens with significant segregation. The Ni, Cu, and Mn alloys that were austempered to complete the first stage of bainite formation had approximately the same impact values for all diameter samples. The Mo alloy upon austempering produced no bainite, but it had much untransformed retained austenite in the intercellular regions and, therefore, had lower impact values.

Co-settling of Chromite and Sulfide Melt Droplets and Trace Element Partitioning between Sulfide and Silicate Melts

NASA Astrophysics Data System (ADS)

Manoochehri, S.; Schmidt, M. W.; Guenther, D.

2013-12-01

Gravitational settling of immiscible, dense sulfide melt droplets together with other cumulate phases such as chromite, combined with downward percolation of these droplets through a cumulate pile, is thought to be one of the possible processes leading to the formation of PGE rich sulfide deposits in layered mafic intrusions. Furthermore some chromitite seams in the Merensky Reef (Bushveld Complex) are considered to be acting as a filter or barrier for further downward percolation of sulfide melts into footwall layers. To investigate the feasibility of such mechanical processes and to study the partitioning behavior of 50 elements including transition metals and REEs (but not PGEs) between a silicate and a sulfide melt, two separate series of high temperature (1250-1380 °C) centrifuge-assisted experiments at 1000 g, 0.4-0.6 GPa were conducted. A synthetic silicate glass with a composition representative of the parental magma of the Bushveld Complex (~ 55 wt% SiO2) was mixed with pure FeS powder. For the first series of experiments, 15 or 25 wt% natural chromite with average grain sizes of ~ 5 or 31 μm were added to a mixture of silicate glass and FeS (10 wt%) adding 1 wt% water. For the second series, a mixture of the same glass and FeS was doped with 50 trace elements. These mixtures were first statically equilibrated and then centrifuged. In the first experimental series, sulfide melt droplets settled together with, but did not segregate from chromite grains even after centrifugation at 1000 g for 12 hours. A change in initial chromite grain size and proportions didn't have any effect on segregation. Without chromite, the starting mixture resulted in the formation of large sulfide melt pools together with finer droplets still disseminated through the silicate glass and both at the bottom of the capsule. The incomplete segregation of sulfide melt is interpreted as being due to high interfacial energies between sulfide and silicate melts/crystals which hinder both, the nucleation of newly formed sulfide droplets and the interconnectivity of separate droplets. The interfacial energies between sulfide melt and silicate or oxide crystals is even higher than for silicate melt, consequently in experiments with chromite, sulfide segregation is even more hindered. Partition coefficients of 50 elements between a sulfide and a silicate melt are determined as a function of differing temperature between 1250 - 1380 °C. As a proxy to investigate the bond strength of network modifier cations, the relation between the partition coefficients and ionic potentials of different groups of elements has been determined.

A view on thermodynamics of concentrated electrolytes: Modification necessity for electrostatic contribution of osmotic coefficient

NASA Astrophysics Data System (ADS)

Sahu, Jyoti; Juvekar, Vinay A.

2018-05-01

Prediction of the osmotic coefficient of concentrated electrolytes is needed in a wide variety of industrial applications. There is a need to correctly segregate the electrostatic contribution to osmotic coefficient from nonelectrostatic contribution. This is achieved in a rational way in this work. Using the Robinson-Stokes-Glueckauf hydrated ion model to predict non-electrostatic contribution to the osmotic coefficient, it is shown that hydration number should be independent of concentration so that the observed linear dependence of osmotic coefficient on electrolyte concentration in high concentration range could be predicted. The hydration number of several electrolytes (LiCl, NaCl, KCl, MgCl2, and MgSO4) has been estimated by this method. The hydration number predicted by this model shows correct dependence on temperature. It is also shown that the electrostatic contribution to osmotic coefficient is underpredicted by the Debye-Hückel theory at concentration beyond 0.1 m. The Debye-Hückel theory is modified by introducing a concentration dependent hydrated ionic size. Using the present analysis, it is possible to correctly estimate the electrostatic contribution to the osmotic coefficient, beyond the range of validation of the D-H theory. This would allow development of a more fundamental model for electrostatic interaction at high electrolyte concentrations.

Experimental partitioning of rare earth elements and scandium among armalcolite, ilmenite, olivine and mare basalt liquid

NASA Technical Reports Server (NTRS)

Irving, A. J.; Merrill, R. B.; Singleton, D. E.

1978-01-01

An experimental study was carried out to measure partition coefficients for two rare-earth elements (Sm and Tm) and Sc among armalcolite, ilmenite, olivine and liquid coexisting in a system modeled on high-Ti mare basalt 74275. This 'primitive' sample was chosen for study because its major and trace element chemistry as well as its equilibrium phase relations at atmospheric pressure are known from previous studies. Beta-track analytical techniques were used so that partition coefficients could be measured in an environment whose bulk trace element composition is similar to that of the natural basalt. Partition coefficients for Cr and Mn were determined in the same experiments by microprobe analysis. The only equilibrium partial melting model appears to be one in which ilmenite is initially present in the source region but is consumed by melting before segregation of the high-Ti mare basalt liquid from the residue.

Advanced methods for preparation and characterization of infrared detector materials

NASA Technical Reports Server (NTRS)

Broerman, J. G.; Morris, B. J.; Meschter, P. J.

1983-01-01

Crystals were prepared by the Bridgman-Stockbarger method with a wide range of crystal growth rates and temperature gradients adequate to prevent constitutional supercooling under diffusion-limited, steady-state, growth conditions. The longitudinal compositional gradients for different growth conditions and alloy compositions were calculated and compared with experimental data to develop a quantitative model of solute redistribution during the crystal growth of the alloys. Measurements were performed to ascertain the effect of growth conditions on radial compositional gradients. The pseudobinary HgTe-CdTe constitutional phase diagram was determined by precision differential-thermal-analysis measurements and used to calculate the segregation coefficient of Cd as a function of x and interface temperature. Experiments were conducted to determine the ternary phase equilibria in selected regions of the Hg-Cd-Te constitutional phase diagram. Electron and hole mobilities as functions of temperature were analyzed to establish charge-carrier scattering probabilities. Computer algorithms specific to Hg(1-x)CdxTe were developed for calculations of the charge-carrier concentration, charge-carrier mobilities, Hall coefficient, and Dermi Fermi energy as functions of x, temperature, ionized donor and acceptor concentrations, and neutral defect concentrations.

Functional connectivity and graph theory in preclinical Alzheimer's disease.

PubMed

Brier, Matthew R; Thomas, Jewell B; Fagan, Anne M; Hassenstab, Jason; Holtzman, David M; Benzinger, Tammie L; Morris, John C; Ances, Beau M

2014-04-01

Alzheimer's disease (AD) has a long preclinical phase in which amyloid and tau cerebral pathology accumulate without producing cognitive symptoms. Resting state functional connectivity magnetic resonance imaging has demonstrated that brain networks degrade during symptomatic AD. It is unclear to what extent these degradations exist before symptomatic onset. In this study, we investigated graph theory metrics of functional integration (path length), functional segregation (clustering coefficient), and functional distinctness (modularity) as a function of disease severity. Further, we assessed whether these graph metrics were affected in cognitively normal participants with cerebrospinal fluid evidence of preclinical AD. Clustering coefficient and modularity, but not path length, were reduced in AD. Cognitively normal participants who harbored AD biomarker pathology also showed reduced values in these graph measures, demonstrating brain changes similar to, but smaller than, symptomatic AD. Only modularity was significantly affected by age. We also demonstrate that AD has a particular effect on hub-like regions in the brain. We conclude that AD causes large-scale disconnection that is present before onset of symptoms. Copyright © 2014 Elsevier Inc. All rights reserved.

Nonequilibrium segregation and phase instability in alloy films during elevated-temperature irradiation in a high-voltage electron microscope

NASA Astrophysics Data System (ADS)

Lam, N. Q.; Okamoto, P. R.

1984-05-01

The effects of defect-production rate gradients, caused by the radial nonuniformity in the electron flux distribution, on solute segregation and phase stability in alloy films undergoing high-voltage electron-microscope (HVEM) irradiation at high temperatures are assessed. Two-dimensional (axially symmetric) compositional redistributions were calculated, taking into account both axial and transverse radial defect fluxes. It was found that when highly focused beams were employed radiation-induced segregation consisted of two stages: dominant axial segregation at the film surfaces at short irradiation times and competitive radial segregation at longer times. The average alloy composition within the irradiated region could differ greatly from that irradiated with a uniform beam, because of the additional atom transport from or to the region surrounding the irradiated zone under the influence of radial fluxes. Damage-rate gradient effects must be taken into account when interpreting in-situ HVEM observations of segregation-induced phase instabilities. The theoretical predictions are compared with experimental observations of the temporal and spatial dependence of segregation-induced precipitation in thin films of Ni-Al, Ni-Ge and Ni-Si solid solutions.

Multi-Contextual Segregation and Environmental Justice Research: Toward Fine-Scale Spatiotemporal Approaches.

PubMed

Park, Yoo Min; Kwan, Mei-Po

2017-10-10

Many environmental justice studies have sought to examine the effect of residential segregation on unequal exposure to environmental factors among different social groups, but little is known about how segregation in non-residential contexts affects such disparity. Based on a review of the relevant literature, this paper discusses the limitations of traditional residence-based approaches in examining the association between socioeconomic or racial/ethnic segregation and unequal environmental exposure in environmental justice research. It emphasizes that future research needs to go beyond residential segregation by considering the full spectrum of segregation experienced by people in various geographic and temporal contexts of everyday life. Along with this comprehensive understanding of segregation, the paper also highlights the importance of assessing environmental exposure at a high spatiotemporal resolution in environmental justice research. The successful integration of a comprehensive concept of segregation, high-resolution data and fine-grained spatiotemporal approaches to assessing segregation and environmental exposure would provide more nuanced and robust findings on the associations between segregation and disparities in environmental exposure and their health impacts. Moreover, it would also contribute to significantly expanding the scope of environmental justice research.

Low hydrogen contents in the cores of terrestrial planets.

PubMed

Clesi, Vincent; Bouhifd, Mohamed Ali; Bolfan-Casanova, Nathalie; Manthilake, Geeth; Schiavi, Federica; Raepsaet, Caroline; Bureau, Hélène; Khodja, Hicham; Andrault, Denis

2018-03-01

Hydrogen has been thought to be an important light element in Earth's core due to possible siderophile behavior during core-mantle segregation. We reproduced planetary differentiation conditions using hydrogen contents of 450 to 1500 parts per million (ppm) in the silicate phase, pressures of 5 to 20 GPa, oxygen fugacity varying within IW-3.7 and IW-0.2 (0.2 to 3.7 log units lower than iron-wüstite buffer), and Fe alloys typical of planetary cores. We report hydrogen metal-silicate partition coefficients of ~2 × 10 -1 , up to two orders of magnitude lower than reported previously, and indicative of lithophile behavior. Our results imply H contents of ~60 ppm in the Earth and Martian cores. A simple water budget suggests that 90% of the water initially present in planetary building blocks was lost during planetary accretion. The retained water segregated preferentially into planetary mantles.

Capturing the Two Dimensions of Residential Segregation at the Neighborhood Level for Health Research

PubMed Central

Oka, Masayoshi; Wong, David W. S.

2014-01-01

Two conceptual and methodological foundations of segregation studies are that (i) segregation involves more than one group, and (ii) segregation measures need to quantify how different population groups are distributed across space. Therefore, percentage of population belonging to a group is not an appropriate measure of segregation because it does not describe how populations are spread across different areal units or neighborhoods. In principle, evenness and isolation are the two distinct dimensions of segregation that capture the spatial patterns of population groups. To portray people’s daily environment more accurately, segregation measures need to account for the spatial relationships between areal units and to reflect the situations at the neighborhood scale. For these reasons, the use of local spatial entropy-based diversity index (SHi) and local spatial isolation index (Si) to capture the evenness and isolation dimensions of segregation, respectively, are preferable. However, these two local spatial segregation indexes have rarely been incorporated into health research. Rather ineffective and insufficient segregation measures have been used in previous studies. Hence, this paper empirically demonstrates how the two measures can reflect the two distinct dimensions of segregation at the neighborhood level, and argues conceptually and set the stage for their future use to effectively and meaningfully examine the relationships between residential segregation and health. PMID:25202687

Agents of Change: Mixed-Race Households and the Dynamics of Neighborhood Segregation in the United States

PubMed Central

Ellis, Mark; Holloway, Steven R.; Wright, Richard; Fowler, Christopher S.

2014-01-01

This article explores the effects of mixed-race household formation on trends in neighborhood-scale racial segregation. Census data show that these effects are nontrivial in relation to the magnitude of decadal changes in residential segregation. An agent-based model illustrates the potential long-run impacts of rising numbers of mixed-race households on measures of neighborhood-scale segregation. It reveals that high rates of mixed-race household formation will reduce residential segregation considerably. This occurs even when preferences for own-group neighbors are high enough to maintain racial separation in residential space in a Schelling-type model. We uncover a disturbing trend, however; levels of neighborhood-scale segregation of single-race households can remain persistently high even while a growing number of mixed-race households drives down the overall rate of residential segregation. Thus, the article’s main conclusion is that parsing neighborhood segregation levels by household type—single versus mixed race—is essential to interpret correctly trends in the spatial separation of racial groups, especially when the fraction of households that are mixed race is dynamic. More broadly, the article illustrates the importance of household-scale processes for urban outcomes and joins debates in geography about interscalar relationships. PMID:25082984

Metropolitan racial residential segregation and cardiovascular mortality: exploring pathways.

PubMed

Greer, Sophia; Kramer, Michael R; Cook-Smith, Jessica N; Casper, Michele L

2014-06-01

Racial residential segregation has been associated with an increased risk for heart disease and stroke deaths. However, there has been little research into the role that candidate mediating pathways may play in the relationship between segregation and heart disease or stroke deaths. In this study, we examined the relationship between metropolitan statistical area (MSA)-level segregation and heart disease and stroke mortality rates, by age and race, and also estimated the effects of various educational, economic, social, and health-care indicators (which we refer to as pathways) on this relationship. We used Poisson mixed models to assess the relationship between the isolation index in 265 U.S. MSAs and county-level (heart disease, stroke) mortality rates. All models were stratified by race (non-Hispanic black, non-Hispanic white), age group (35-64 years, ≥ 65 years), and cause of death (heart disease, stroke). We included each potential pathway in the model separately to evaluate its effect on the segregation-mortality association. Among blacks, segregation was positively associated with heart disease mortality rates in both age groups but only with stroke mortality rates in the older age group. Among whites, segregation was marginally associated with heart disease mortality rates in the younger age group and was positively associated with heart disease mortality rates in the older age group. Three of the potential pathways we explored attenuated relationships between segregation and mortality rates among both blacks and whites: percentage of female-headed households, percentage of residents living in poverty, and median household income. Because the percentage of female-headed households can be seen as a proxy for the extent of social disorganization, our finding that it has the greatest attenuating effect on the relationship between racial segregation and heart disease and stroke mortality rates suggests that social disorganization may play a strong role in the elevated rates of heart disease and stroke found in racially segregated metropolitan areas.

Simulations of irradiated-enhanced segregation and phase separation in Fe-Cu-Mn alloys

NASA Astrophysics Data System (ADS)

Li, Boyan; Hu, Shenyang; Li, Chengliang; Li, Qiulin; Chen, Jun; Shu, Guogang; Henager, Chuck, Jr.; Weng, Yuqing; Xu, Ben; Liu, Wei

2017-09-01

For reactor pressure vessel steels, the addition of Cu, Mn, and Ni has a positive effect on their mechanical, corrosion and radiation resistance properties. However, experiments show that radiation-enhanced segregation and/or phase separation is one of the important material property degradation processes. In this work, we develop a model integrating rate theory and phase-field approaches to investigate the effect of irradiation on solute segregation and phase separation. The rate theory is used to describe the accumulation and clustering of radiation defects, while the phase-field approach describes the effect of radiation defects on phase stability and microstructure evolution. The Fe-Cu-Mn ternary alloy is taken as a model system. The free energies used in the phase-field model are from CALPHAD. Spatial dependent radiation damage from atomistic simulations is introduced into the simulation cell for a given radiation dose rate. The radiation effect on segregation and phase separation is taken into account through the defect concentration dependence of solute mobility. Using the model, the effect of temperature and radiation rates on Cu and Mn segregation and Cu-rich phase nucleation were systematically investigated. The segregation and nucleation mechanisms were analyzed. The simulations demonstrate that the nucleus of Cu precipitates has a core-shell composition profile, i.e. Cu-rich at the center and Mn-rich at the interface, in good agreement with theoretical calculations as well as experimental observations.

Interface and facet control during Czochralski growth of (111) InSb crystals for cost reduction and yield improvement of IR focal plane array substrates

NASA Astrophysics Data System (ADS)

Gray, Nathan W.; Perez-Rubio, Victor; Bolke, Joseph G.; Alexander, W. B.

2014-10-01

Focal plane arrays (FPAs) made on InSb wafers are the key cost-driving component in IR imaging systems. The electronic and crystallographic properties of the wafer directly determine the imaging device performance. The "facet effect" describes the non-uniform electronic properties of crystals resulting from anisotropic dopant segregation during bulk growth. When the segregation coefficient of dopant impurities changes notably across the melt/solid interface of a growing crystal the result is non-uniform electronic properties across wafers made from these crystals. The effect is more pronounced in InSb crystals grown on the (111) axis compared with other orientations and crystal systems. FPA devices made on these wafers suffer costly yield hits due to inconsistent device response and performance. Historically, InSb crystal growers have grown approximately 9-19 degree off-axis from the (111) to avoid the facet effect and produced wafers with improved uniformity of electronic properties. It has been shown by researchers in the 1960s that control of the facet effect can produce uniform small diameter crystals. In this paper, we share results employing a process that controls the facet effect when growing large diameter crystals from which 4, 5, and 6" wafers can be manufactured. The process change resulted in an increase in wafers yielded per crystal by several times, all with high crystal quality and uniform electronic properties. Since the crystals are grown on the (111) axis, manufacturing (111) oriented wafers is straightforward with standard semiconductor equipment and processes common to the high-volume silicon wafer industry. These benefits result in significant manufacturing cost savings and increased value to our customers.

Effect of Co-segregating Markers on High-Density Genetic Maps and Prediction of Map Expansion Using Machine Learning Algorithms.

PubMed

N'Diaye, Amidou; Haile, Jemanesh K; Fowler, D Brian; Ammar, Karim; Pozniak, Curtis J

2017-01-01

Advances in sequencing and genotyping methods have enable cost-effective production of high throughput single nucleotide polymorphism (SNP) markers, making them the choice for linkage mapping. As a result, many laboratories have developed high-throughput SNP assays and built high-density genetic maps. However, the number of markers may, by orders of magnitude, exceed the resolution of recombination for a given population size so that only a minority of markers can accurately be ordered. Another issue attached to the so-called 'large p, small n' problem is that high-density genetic maps inevitably result in many markers clustering at the same position (co-segregating markers). While there are a number of related papers, none have addressed the impact of co-segregating markers on genetic maps. In the present study, we investigated the effects of co-segregating markers on high-density genetic map length and marker order using empirical data from two populations of wheat, Mohawk × Cocorit (durum wheat) and Norstar × Cappelle Desprez (bread wheat). The maps of both populations consisted of 85% co-segregating markers. Our study clearly showed that excess of co-segregating markers can lead to map expansion, but has little effect on markers order. To estimate the inflation factor (IF), we generated a total of 24,473 linkage maps (8,203 maps for Mohawk × Cocorit and 16,270 maps for Norstar × Cappelle Desprez). Using seven machine learning algorithms, we were able to predict with an accuracy of 0.7 the map expansion due to the proportion of co-segregating markers. For example in Mohawk × Cocorit, with 10 and 80% co-segregating markers the length of the map inflated by 4.5 and 16.6%, respectively. Similarly, the map of Norstar × Cappelle Desprez expanded by 3.8 and 11.7% with 10 and 80% co-segregating markers. With the increasing number of markers on SNP-chips, the proportion of co-segregating markers in high-density maps will continue to increase making map expansion unavoidable. Therefore, we suggest developers improve linkage mapping algorithms for efficient analysis of high-throughput data. This study outlines a practical strategy to estimate the IF due to the proportion of co-segregating markers and outlines a method to scale the length of the map accordingly.

Effect of Co-segregating Markers on High-Density Genetic Maps and Prediction of Map Expansion Using Machine Learning Algorithms

PubMed Central

N’Diaye, Amidou; Haile, Jemanesh K.; Fowler, D. Brian; Ammar, Karim; Pozniak, Curtis J.

2017-01-01

Advances in sequencing and genotyping methods have enable cost-effective production of high throughput single nucleotide polymorphism (SNP) markers, making them the choice for linkage mapping. As a result, many laboratories have developed high-throughput SNP assays and built high-density genetic maps. However, the number of markers may, by orders of magnitude, exceed the resolution of recombination for a given population size so that only a minority of markers can accurately be ordered. Another issue attached to the so-called ‘large p, small n’ problem is that high-density genetic maps inevitably result in many markers clustering at the same position (co-segregating markers). While there are a number of related papers, none have addressed the impact of co-segregating markers on genetic maps. In the present study, we investigated the effects of co-segregating markers on high-density genetic map length and marker order using empirical data from two populations of wheat, Mohawk × Cocorit (durum wheat) and Norstar × Cappelle Desprez (bread wheat). The maps of both populations consisted of 85% co-segregating markers. Our study clearly showed that excess of co-segregating markers can lead to map expansion, but has little effect on markers order. To estimate the inflation factor (IF), we generated a total of 24,473 linkage maps (8,203 maps for Mohawk × Cocorit and 16,270 maps for Norstar × Cappelle Desprez). Using seven machine learning algorithms, we were able to predict with an accuracy of 0.7 the map expansion due to the proportion of co-segregating markers. For example in Mohawk × Cocorit, with 10 and 80% co-segregating markers the length of the map inflated by 4.5 and 16.6%, respectively. Similarly, the map of Norstar × Cappelle Desprez expanded by 3.8 and 11.7% with 10 and 80% co-segregating markers. With the increasing number of markers on SNP-chips, the proportion of co-segregating markers in high-density maps will continue to increase making map expansion unavoidable. Therefore, we suggest developers improve linkage mapping algorithms for efficient analysis of high-throughput data. This study outlines a practical strategy to estimate the IF due to the proportion of co-segregating markers and outlines a method to scale the length of the map accordingly. PMID:28878789

Dopant occupancy and UV-VIS-NIR spectroscopy of Mg (0, 4, 5 and 6 mol.%):Dy:LiNbO3 crystal

NASA Astrophysics Data System (ADS)

Dai, Li; Liu, Chunrui; Han, Xianbo; Wang, Luping; Tan, Chao; Yan, Zhehua; Xu, Yuheng

2017-09-01

A series of Dy:LiNbO3 crystals with x mol.% Mg2+ ions (x =0, 4, 5 and 6 mol.%) were grown by the Czochralski method. The effective segregation coefficient of Mg2+ and Dy3+ ions was studied by the inductively coupled plasma-atomic emission spectrometry (ICP-AES). UV-VIS-NIR absorption spectra and Judd-Ofelt theory were used to investigate their spectroscopic properties. J-O intensity parameters (Ω2 = 7.53 × 10-20cm2, Ω4 = 6.98 × 10-20cm2, and Ω6 = 3.09 × 10-20cm2) and larger spectroscopic quality factor (X = 2.26) for Mg:(6 mol.%)Dy:LiNbO3 crystals were obtained.

The Effects of Segregation and the Consequences of Desegregation A (September 1952) Social Science Statement in the Brown v. Board of Education of Topeka Supreme Court Case

ERIC Educational Resources Information Center

Clark, Kenneth B.; Chein, Isidor; Cook, Stuart W.

2004-01-01

This statement was an appendix to the appellants' briefs in the Brown v. Board of Education of Topeka, Kansas, Briggs v. Elliott, and Davis v. Prince Edward County, Virginia, cases. The statement offers definitions of segregation and discusses the implications and potential effects of segregation on children both in minority and majority groups.

Multi-Contextual Segregation and Environmental Justice Research: Toward Fine-Scale Spatiotemporal Approaches

PubMed Central

Park, Yoo Min; Kwan, Mei-Po

2017-01-01

Many environmental justice studies have sought to examine the effect of residential segregation on unequal exposure to environmental factors among different social groups, but little is known about how segregation in non-residential contexts affects such disparity. Based on a review of the relevant literature, this paper discusses the limitations of traditional residence-based approaches in examining the association between socioeconomic or racial/ethnic segregation and unequal environmental exposure in environmental justice research. It emphasizes that future research needs to go beyond residential segregation by considering the full spectrum of segregation experienced by people in various geographic and temporal contexts of everyday life. Along with this comprehensive understanding of segregation, the paper also highlights the importance of assessing environmental exposure at a high spatiotemporal resolution in environmental justice research. The successful integration of a comprehensive concept of segregation, high-resolution data and fine-grained spatiotemporal approaches to assessing segregation and environmental exposure would provide more nuanced and robust findings on the associations between segregation and disparities in environmental exposure and their health impacts. Moreover, it would also contribute to significantly expanding the scope of environmental justice research. PMID:28994744

Coleman Revisited: School Segregation, Peers, and Frog Ponds

ERIC Educational Resources Information Center

Goldsmith, Pat Rubio

2011-01-01

Students from minority segregated schools tend to achieve and attain less than similar students from White segregated schools. This study examines whether peer effects can explain this relationship using normative models and frog-pond models. Normative models (where peers become alike) suggest that minority schoolmates are a liability. Frog-pond…

Seeing Race: Teaching Residential Segregation with the Racial Dot Map

ERIC Educational Resources Information Center

Seguin, Charles; Nierobisz, Annette; Kozlowski, Karen Phelan

2017-01-01

Students commonly hold erroneous notions of a "post-racial" world and individualistic worldviews that discount the role of structure in social outcomes. Jointly, these two preconceived beliefs can be powerful barriers to effective teaching of racial segregation: Students may be skeptical that racial segregation continues to exist, and…

Undocumented Migration and the Residential Segregation of Mexicans in New Destinations1

PubMed Central

Hall, Matthew; Stringfield, Jonathan

2014-01-01

This study uses data from the 2000 Census and 2005–2009 American Community Survey to examine the impact of undocumented Mexican migration to new destinations on residential segregation between Mexican immigrants and native-born whites and native-born blacks. We find that Mexican-white and Mexican-black segregation is higher in new Mexican gateways than in established areas and that, for Mexican-immigrant segregation from whites, this heightened level of residential segregation in new destinations can be explained by the high presence of unauthorized Mexican immigrants living there which tends to bolster segregation between the two groups. By contrast, Mexican-immigrant segregation from native-born blacks tends to be lower in areas with larger undocumented populations, a pattern that is especially true in new destinations. Neither of these opposing effects of legal status on Mexican-immigrant segregation can be explained by compositional differences in assimilation (English ability and earnings) between documented and undocumented immigrants nor by structural variation in metropolitan areas, suggesting a unique association between legal status and segregation. PMID:24913945

Factors shaping workplace segregation between natives and immigrants.

PubMed

Strömgren, Magnus; Tammaru, Tiit; Danzer, Alexander M; van Ham, Maarten; Marcińczak, Szymon; Stjernström, Olof; Lindgren, Urban

2014-04-01

Research on segregation of immigrant groups is increasingly turning its attention from residential areas toward other important places, such as the workplace, where immigrants can meet and interact with members of the native population. This article examines workplace segregation of immigrants. We use longitudinal, georeferenced Swedish population register data, which enables us to observe all immigrants in Sweden for the period 1990-2005 on an annual basis. We compare estimates from ordinary least squares with fixed-effects regressions to quantify the extent of immigrants' self-selection into specific workplaces, neighborhoods, and partnerships, which may bias more naïve ordinary least squares results. In line with previous research, we find lower levels of workplace segregation than residential segregation. The main finding is that low levels of residential segregation reduce workplace segregation, even after we take into account intermarriage with natives as well as unobserved characteristics of immigrants' such as willingness and ability to integrate into the host society. Being intermarried with a native reduces workplace segregation for immigrant men but not for immigrant women.

Na, Rb and Cs partitioning between metal, silicate and sulfide: Implications for volatile depletion in terrestrial planets

NASA Astrophysics Data System (ADS)

Boujibar, A.; Fei, Y.; Du, Z.; Righter, K.; Bullock, E. S.

2017-12-01

Inner Solar System materials are known for their depletion in volatile elements, including the moderately volatile alkalis: Na, K, Rb, and Cs. The origin of this depletion is still uncertain, as several processes could have been involved, during the nebular condensation or planetary accretion. Volatile depletion is commonly estimated through comparison of alkali concentrations relatively to those of chondrites, assuming they remain in planetary mantles during core segregation. However, experimental studies show that substantial K can partition into metals that are enriched in sulfur and oxygen. Several models have also suggested that sulfides may have played an important role during episodes of sulfide segregation from a crystallizing magma ocean (sulfide matte) or accretion of S-rich planetary embryos. For Mercury, a sulfide layer could be present between core and mantle, due to immiscibility between Si-rich and S-rich metals. Therefore, here we investigate whether alkali elements (Na, Cs and Rb) could be partly sequestered in planetary cores during their differentiation. We conducted experiments at high pressure and temperature (1 to 5 GPa and up to 1900 °C) to determine partition coefficients of Na, Rb and Cs between metal and silicate. Our results show that pressure, temperature, sulfur and oxygen in metals enhance the partitioning of Na, Rb and Cs into metals, as previously found for K. For all three investigated alkalis (Na, Rb and Cs), we found a maximum partition coefficient of 1 between sulfides containing 13 wt% O and silicate melt. Therefore, S-rich cores or sulfide layers formed due to immiscibility in Fe-S-O systems could have acted as important geochemical reservoirs for alkali elements. Using our experimental data and different assumptions on initial bulk abundances, we evaluate volatile depletion in terrestrial planets, by comparing resulting mantle alkali concentrations after core segregation, with actual concentrations in the Earth's mantle.

Residential segregation and birth weight among racial and ethnic minorities in the United States.

PubMed

Walton, Emily

2009-12-01

Racial and ethnic minorities are often residentially segregated from whites in urban settings, a fact which has important health consequences. Research on the relationship between residential segregation and health outcomes lacks national-level investigation of racial and ethnic minority groups other than African Americans. I use multilevel analyses to examine the associations of residential isolation and clustering with birth weight among Asian, black, and Latino Americans using data from the National Center for Health Statistics' Natality Files and the U.S. Census. Findings indicate that segregation has a negative effect on the likelihood of having a low birth weight baby among Asian Americans, suggesting a possible concentration of social and structural resources in highly-segregated communities. On the contrary, segregation marginally increases the odds of low birth weight among African Americans, but only in the presence of higher poverty rates. Segregation does not affect birth weight among Latino Americans.

SEMICONDUCTOR TECHNOLOGY: SBH adjustment characteristic of the dopant segregation process for NiSi/n-Si SJDs

NASA Astrophysics Data System (ADS)

Haiping, Shang; Qiuxia, Xu

2010-05-01

By means of analyzing the I-V characteristic curve of NiSi/n-Si Schottky junction diodes (NiSi/n-Si SJDs), abstracting the effective Schottky barrier height (varphiB, eff) and the ideal factor of NiSi/n-Si SJDs and measuring the sheet resistance of NiSi films (RNiSi), we study the effects of different dopant segregation process parameters, including impurity implantation dose, segregation annealing temperature and segregation annealing time, on the varphiB, eff of NiSi/n-Si SJDs and the resistance characteristic of NiSi films. In addition, the changing rules of varphiB, eff and RNiSi are discussed.

Simulations of irradiated-enhanced segregation and phase separation in Fe–Cu–Mn alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Boyan; Hu, Shenyang; Li, Chengliang

2017-06-13

For reactor pressure vessel steels, the addition of Cu, Mn, and Ni has a positive effect on mechanical, corrosion and radiation resistance properties. However, experiments show that radiation-enhanced segregation and/or phase separation is one of important material property degradation processes. In this work, we developed a model integrating rate theory and phase-field approaches to investigate the effect of irradiation on solute segregation and phase separation. The rate theory is used to describe the accumulation and clustering of radiation defects while the phase-field approach describes the effect of radiation defects on phase stability and microstructure evolution. The Fe-Cu-Mn ternary alloy ismore » taken as a model system. The free energies used in the phase-field model are from CALPHAD. Spatial dependent radiation damage from atomistic simulations is introduced into the simulation cell for a given radiation dose rate. The radiation effect on segregation and phase separation is taken into account through the defect concentration dependence of solute mobility. With the model the effect of temperatures and radiation rates on Cu and Mn segregation and Cu-rich phase nucleation are systematically investigated. The segregation and nucleation mechanisms are analyzed. The simulations demonstrated that the nucleus of Cu precipitates has a core-shell composition profile, i.e., Cu rich at center and Mn rich at the interface, in good agreement with the theoretical calculation as well as experimental observations.« less

RACIAL ISOLATION IN THE PUBLIC SCHOOLS, VOLUME 1.

ERIC Educational Resources Information Center

HANNAH, JOHN A.; AND OTHERS

THE FINDINGS OF A STUDY OF RACIAL ISOLATION IN THE PUBLIC SCHOOLS ARE DISCUSSED. THE STUDY FOCUSED ON (1) THE EXTENT OF RACIAL SEGREGATION IN THE SCHOOLS AND THE DISPARITY BETWEEN THE EDUCATIONAL ACHIEVEMENT OF NEGRO AND WHITE SCHOOL CHILDREN, (2) FACTORS WHICH INTENSIFY AND PERPETUATE SEGREGATION, (3) THE EFFECTS OF SEGREGATED SCHOOLING ON…

Standardized Testing and School Segregation: Like Tinder for Fire?

ERIC Educational Resources Information Center

Knoester, Matthew; Au, Wayne

2017-01-01

Recent research suggests that high-stakes standardized testing has played a negative role in the segregation of children by race and class in schools. In this article we review research on the overall effects of segregation, the positive and negative aspects of how desegregation plans were carried out following the 1954 Supreme Court decision…

Effect of Macrosegregation on the Microstructure and Mechanical Properties of a Pressure-Vessel Steel

NASA Astrophysics Data System (ADS)

Yan, Guanghua; Han, Lizhan; Li, Chuanwei; Luo, Xiaomeng; Gu, Jianfeng

2017-07-01

Macrosegregation refers to the chemical segregation, which occurs quite commonly in the large forgings such as nuclear reactor pressure vessel. This work assesses the effect of macrosegregation and homogenization treatment on the mechanical properties of a pressure-vessel steel (SA508 Gr.3). It was found that the primary reason for the inhomogeneity of the microstructure was the segregation of Mn, Mo, and Ni. Martensite, and coarse upper bainite with M-A (martensite-austenite) islands have been obtained, respectively, in the positive and negative segregation zone during a simulated quenching process. During tempering, the carbon-rich M-A islands decomposed into a mixture of ferrite and numerous carbides which deteriorated the toughness of the material. The segregation has been substantially minimized by a homogenizing treatment. The results indicate that the material homogenized has a higher impact toughness than the material with segregation, due to the reduction in M-A island in the negative segregation zone. It can be concluded that the microstructure and mechanical properties have been improved remarkably by means of homogenization treatment.

Prior Knowledge Guides Speech Segregation in Human Auditory Cortex.

PubMed

Wang, Yuanye; Zhang, Jianfeng; Zou, Jiajie; Luo, Huan; Ding, Nai

2018-05-18

Segregating concurrent sound streams is a computationally challenging task that requires integrating bottom-up acoustic cues (e.g. pitch) and top-down prior knowledge about sound streams. In a multi-talker environment, the brain can segregate different speakers in about 100 ms in auditory cortex. Here, we used magnetoencephalographic (MEG) recordings to investigate the temporal and spatial signature of how the brain utilizes prior knowledge to segregate 2 speech streams from the same speaker, which can hardly be separated based on bottom-up acoustic cues. In a primed condition, the participants know the target speech stream in advance while in an unprimed condition no such prior knowledge is available. Neural encoding of each speech stream is characterized by the MEG responses tracking the speech envelope. We demonstrate that an effect in bilateral superior temporal gyrus and superior temporal sulcus is much stronger in the primed condition than in the unprimed condition. Priming effects are observed at about 100 ms latency and last more than 600 ms. Interestingly, prior knowledge about the target stream facilitates speech segregation by mainly suppressing the neural tracking of the non-target speech stream. In sum, prior knowledge leads to reliable speech segregation in auditory cortex, even in the absence of reliable bottom-up speech segregation cue.

Development of Computational Tools for Modeling Thermal and Radiation Effects on Grain Boundary Segregation and Precipitation in Fe-Cr-Ni-based Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ying

This work aims at developing computational tools for modeling thermal and radiation effects on solute segregation at grain boundaries (GBs) and precipitation. This report described two major efforts. One is the development of computational tools on integrated modeling of thermal equilibrium segregation (TES) and radiation-induced segregation (RIS), from which synergistic effects of thermal and radiation, pre-existing GB segregation have been taken into consideration. This integrated modeling was used in describing the Cr and Ni segregation in the Fe-Cr-Ni alloys. The other effort is thermodynamic modeling on the Fe-Cr-Ni-Mo system which includes the major alloying elements in the investigated alloys inmore » the Advanced Radiation Resistant Materials (ARRM) program. Through thermodynamic calculation, we provide baseline thermodynamic stability of the hardening phase Ni2(Cr,Mo) in selected Ni-based super alloys, and contribute knowledge on mechanistic understanding on the formation of Ni2(Cr,Mo) in the irradiated materials. The major outcomes from this work are listed in the following: 1) Under the simultaneous thermal and irradiation conditions, radiation-induced segregation played a dominant role in the GB segregation. The pre-existing GB segregation only affects the subsequent radiation-induced segregation in the short time. For the same element, the segregation tendency of Cr and Ni due to TES is opposite to it from RIS. The opposite tendency can lead to the formation of W-shape profile. These findings are consistent with literature observation of the transitory W-shape profile. 2) While TES only affects the distance of one or two atomic layers from GBs, the RIS can affect a broader distance from GB. Therefore, the W-shape due to pre-existing GB segregation is much narrower than that due to composition gradient formed during the transient state. Considering the measurement resolution of Auger or STEM analysis, the segregation tendency due to RIS should play a dominant role in the measured values. However, The GB segregation due to pre-existing GB segregation may affect the chemical potential of element at GB, and subsequently the corrosion resistance. 3) Based on the newly developed thermodynamic database of Fe-Cr-Ni-Mo, we predicted the Ni2(Cr,Mo) as a thermodynamically stable phase in all investigated low Fe-content Ni-based alloys. The calculated phase amount decreases with the increasing Fe content, being consistent with that observed in the irradiated materials. 4) The formation of the Ni2(Cr,Mo) phase in irradiated materials is due to irradiation enhanced diffusion. The calculated equilibrium Ni2(Cr,Mo) amount is more than that observed in the irradiated materials, suggesting that the amount of Ni2(Cr,Mo) is likely to increase more with further irradiation.« less

Enclaves of opportunity or "ghettos of last resort?" Assessing the effects of immigrant segregation on violent crime rates.

PubMed

Feldmeyer, Ben; Harris, Casey T; Scroggins, Jennifer

2015-07-01

A growing body of research indicates that immigration to the U.S. has crime-reducing effects on aggregate levels of violence, which researchers have often attributed to the protective and revitalizing effects of immigrants settling in spatially concentrated neighborhoods. However, recent scholarship suggests that growing shares of the foreign-born population are bypassing these segregated immigrant enclaves and are dispersing more widely to other urban neighborhoods. Moreover, some scholars suggest that spatially isolating immigrant populations may not always be protective, but could actually contribute to social problems like crime, particularly in disadvantaged contexts. The current study offers one of the first analyses exploring the way that segregation of immigrant populations (relative to the U.S.-born) is related to year 2000 violent crime rates for nearly 500 census places in California and New York. Results of our analysis reveal no direct link between immigrant segregation and macro-level violence, but instead show that these effects are highly contextualized and depend on the resources present in locales. Specifically, immigrant segregation contributes to violence in highly disadvantaged places but is linked to lower violence in areas with greater resources. Copyright © 2015 Elsevier Inc. All rights reserved.

Racial segregation, income inequality, and mortality in US metropolitan areas.

PubMed

Nuru-Jeter, Amani M; LaVeist, Thomas A

2011-04-01

Evidence of the association between income inequality and mortality has been mixed. Studies indicate that growing income inequalities reflect inequalities between, rather than within, racial groups. Racial segregation may play a role. We examine the role of racial segregation on the relationship between income inequality and mortality in a cross-section of US metropolitan areas. Metropolitan areas were included if they had a population of at least 100,000 and were at least 10% black (N = 107). Deaths for the time period 1991-1999 were used to calculate age-adjusted all-cause mortality rates for each metropolitan statistical area (MSA) using direct age-adjustment techniques. Multivariate least squares regression was used to examine associations for the total sample and for blacks and whites separately. Income inequality was associated with lower mortality rates among whites and higher mortality rates among blacks. There was a significant interaction between income inequality and racial segregation. A significant graded inverse income inequality/mortality association was found for MSAs with higher versus lower levels of black-white racial segregation. Effects were stronger among whites than among blacks. A positive income inequality/mortality association was found in MSAs with higher versus lower levels of Hispanic-white segregation. Uncertainty regarding the income inequality/mortality association found in previous studies may be related to the omission of important variables such as racial segregation that modify associations differently between groups. Research is needed to further elucidate the risk and protective effects of racial segregation across groups.

The Gerrymandering of School Attendance Zones and the Segregation of Public Schools: A Geospatial Analysis

ERIC Educational Resources Information Center

Richards, Meredith P.

2014-01-01

In this study, I employ geospatial techniques to assess the impact of school attendance zone "gerrymandering" on the racial/ethnic segregation of schools, using a large national sample of 15,290 attendance zones in 663 districts. I estimate the effect of gerrymandering on school diversity and school district segregation by comparing the…

Segregation simulation of binary granular matter under horizontal pendulum vibrations

NASA Astrophysics Data System (ADS)

Ma, Xuedong; Zhang, Yanbing; Ran, Heli; Zhang, Qingying

2016-08-01

Segregation of binary granular matter with different densities under horizontal pendulum vibrations was investigated through numerical simulation using a 3D discrete element method (DEM). The particle segregation mechanism was theoretically analyzed using gap filling, momentum and kinetic energy. The effect of vibrator geometry on granular segregation was determined using the Lacey mixing index. This study shows that dynamic changes in particle gaps under periodic horizontal pendulum vibrations create a premise for particle segregation. The momentum of heavy particles is higher than that of light particles, which causes heavy particles to sink and light particles to float. With the same horizontal vibration parameters, segregation efficiency and stability, which are affected by the vibrator with a cylindrical convex geometry, are superior to that of the original vibrator and the vibrator with a cross-bar structure. Moreover, vibrator geometry influences the segregation speed of granular matter. Simulation results of granular segregation by using the DEM are consistent with the final experimental results, thereby confirming the accuracy of the simulation results and the reliability of the analysis.

InGaAs/GaAs Quantum Dots: Effects of Ensemble Interactions, Interdiffusion, Segregation and Proton Irradiation

NASA Technical Reports Server (NTRS)

Leon, R.

2000-01-01

A sumary or recent experimental findings on the effects of interdiffusion, segregation, strained ensemble interactions and proton irradiation on the optical properties of InGaAs/GaAs quantum dots (QDs) are presented.

Thermal effects in equilibrium surface segregation in a copper/10-atomic-percent-aluminum alloy using Auger electron spectroscopy

NASA Technical Reports Server (NTRS)

Ferrante, J.

1972-01-01

Equilibrium surface segregation of aluminum in a copper-10-atomic-percent-aluminum single crystal alloy oriented in the /111/ direction was demonstrated by using Auger electron spectroscopy. This crystal was in the solid solution range of composition. Equilibrium surface segregation was verified by observing that the aluminum surface concentration varied reversibly with temperature in the range 550 to 850 K. These results were curve fitted to an expression for equilibrium grain boundary segregation and gave a retrieval energy of 5780 J/mole (1380 cal/mole) and a maximum frozen-in surface coverage three times the bulk layer concentration. Analyses concerning the relative merits of sputtering calibration and the effects of evaporation are also included.

Beyond the Census Tract: Patterns and Determinants of Racial Segregation at Multiple Geographic Scales*

PubMed Central

Lee, Barrett A.; Reardon, Sean F.; Firebaugh, Glenn; Farrell, Chad R.; Matthews, Stephen A.; O'Sullivan, David

2014-01-01

The census tract-based residential segregation literature rests on problematic assumptions about geographic scale and proximity. We pursue a new tract-free approach that combines explicitly spatial concepts and methods to examine racial segregation across egocentric local environments of varying size. Using 2000 census data for the 100 largest U.S. metropolitan areas, we compute a spatially modified version of the information theory index H to describe patterns of black-white, Hispanic-white, Asian-white, and multi-group segregation at different scales. The metropolitan structural characteristics that best distinguish micro-segregation from macro-segregation for each group combination are identified, and their effects are decomposed into portions due to racial variation occurring over short and long distances. A comparison of our results to those from tract-based analyses confirms the value of the new approach. PMID:25324575

Racial residential segregation: a fundamental cause of racial disparities in health.

PubMed

Williams, D R; Collins, C

2001-01-01

Racial residential segregation is a fundamental cause of racial disparities in health. The physical separation of the races by enforced residence in certain areas is an institutional mechanism of racism that was designed to protect whites from social interaction with blacks. Despite the absence of supportive legal statutes, the degree of residential segregation remains extremely high for most African Americans in the United States. The authors review evidence that suggests that segregation is a primary cause of racial differences in socioeconomic status (SES) by determining access to education and employment opportunities. SES in turn remains a fundamental cause of racial differences in health. Segregation also creates conditions inimical to health in the social and physical environment. The authors conclude that effective efforts to eliminate racial disparities in health must seriously confront segregation and its pervasive consequences.

Socio-Economic Segregation of Disadvantaged Children between Schools in Pakistan: Comparing the State and Private Sector

ERIC Educational Resources Information Center

Siddiqui, Nadia

2017-01-01

The distribution of children in different school-types and regions in Pakistan suggests that access and opportunities in education are not evenly accessible for many children. Segregation at school level is an important concern for equity and social justice because the adverse effects of segregation increase the pre-existing gap in opportunities…

The Legacy Effect: Understanding How Segregation and Environmental Injustice Unfold over Time in Baltimore

Treesearch

Morgan Grove; Laura Ogden; Steward Pickett; Chris Boone; Geoff Buckley; Dexter H. Locke; Charlie Lord; Billy Hall

2018-01-01

Legacies of social and environmental injustices can leave an imprint on the present and constrain transitions for more sustainable futures. In this article, we ask this question: What is the relationship of environmental inequality and histories of segregation? The answer for Baltimore is complex, where past practices of de jure and de facto segregation have created...

The Effect of High School Socioeconomic, Racial, and Linguistic Segregation on Academic Performance and School Behaviors

ERIC Educational Resources Information Center

Palardy, Gregory J.; Rumberger, Russell W.; Butler, Truman

2015-01-01

Background/Context: The 1954 U.S. Supreme Court decision on Brown v. Board of Education concluded that segregated schools were inherently unequal and therefore unlawful. That decision was not based solely upon the notion that segregated black schools were inferior in terms of academic instruction, curricular rigor, resources, etc., but also on…

The Struggle against Separate and Unequal Schools: Middle Class Mexican Americans and the Desegregation Campaign in Texas, 1929-1957.

ERIC Educational Resources Information Center

San Miguel, Guadalupe, Jr.

1983-01-01

Despite the efforts of Mexican American groups, such as the League of United Latin American Citizens and the G.I. Forum, and court orders to end segregation, schools in Texas continued to segregate Mexican American children. The political liberalism of these groups kept them from developing effective strategies against segregation. (IS)

The Integrating and Segregating Effects of School Choice

ERIC Educational Resources Information Center

Koedel, Cory; Betts, Julian R.; Rice, Lorien A.; Zau, Andrew C.

2009-01-01

We evaluate the integrating and segregating effects of three distinct school choice programs in San Diego. We go beyond the traditional question of racial integration and examine the integration of students by test scores, parental education levels, and language status. In addition to measuring the net integrative effects of school choice, we also…

HOW POPULATION STRUCTURE SHAPES NEIGHBORHOOD SEGREGATION*

PubMed Central

Bruch, Elizabeth E.

2014-01-01

This study investigates how choices about social affiliation based on one attribute can exacerbate or attenuate segregation on another correlated attribute. The specific application is the role of racial and economic factors in generating patterns of racial residential segregation. I identify three population parameters—between-group inequality, within-group inequality, and relative group size—that determine how income inequality between race groups affects racial segregation. I use data from the Panel Study of Income Dynamics to estimate models of individual-level residential mobility, and incorporate these estimates into agent-based models. I then simulate segregation dynamics under alternative assumptions about: (1) the relative size of minority groups; and (2) the degree of correlation between race and income among individuals. I find that income inequality can have offsetting effects at the high and low ends of the income distribution. I demonstrate the empirical relevance of the simulation results using fixed-effects, metro-level regressions applied to 1980-2000 U.S. Census data. PMID:25009360

Colonic stem cell data are consistent with the immortal model of stem cell division under non-random strand segregation.

PubMed

Walters, K

2009-06-01

Colonic stem cells are thought to reside towards the base of crypts of the colon, but their numbers and proliferation mechanisms are not well characterized. A defining property of stem cells is that they are able to divide asymmetrically, but it is not known whether they always divide asymmetrically (immortal model) or whether there are occasional symmetrical divisions (stochastic model). By measuring diversity of methylation patterns in colon crypt samples, a recent study found evidence in favour of the stochastic model, assuming random segregation of stem cell DNA strands during cell division. Here, the effect of preferential segregation of the template strand is considered to be consistent with the 'immortal strand hypothesis', and explore the effect on conclusions of previously published results. For a sample of crypts, it is shown how, under the immortal model, to calculate mean and variance of the number of unique methylation patterns allowing for non-random strand segregation and compare them with those observed. The calculated mean and variance are consistent with an immortal model that incorporates non-random strand segregation for a range of stem cell numbers and levels of preferential strand segregation. Allowing for preferential strand segregation considerably alters previously published conclusions relating to stem cell numbers and turnover mechanisms. Evidence in favour of the stochastic model may not be as strong as previously thought.

Opposing dorsal/ventral stream dynamics during figure-ground segregation.

PubMed

Wokke, Martijn E; Scholte, H Steven; Lamme, Victor A F

2014-02-01

The visual system has been commonly subdivided into two segregated visual processing streams: The dorsal pathway processes mainly spatial information, and the ventral pathway specializes in object perception. Recent findings, however, indicate that different forms of interaction (cross-talk) exist between the dorsal and the ventral stream. Here, we used TMS and concurrent EEG recordings to explore these interactions between the dorsal and ventral stream during figure-ground segregation. In two separate experiments, we used repetitive TMS and single-pulse TMS to disrupt processing in the dorsal (V5/HMT⁺) and the ventral (lateral occipital area) stream during a motion-defined figure discrimination task. We presented stimuli that made it possible to differentiate between relatively low-level (figure boundary detection) from higher-level (surface segregation) processing steps during figure-ground segregation. Results show that disruption of V5/HMT⁺ impaired performance related to surface segregation; this effect was mainly found when V5/HMT⁺ was perturbed in an early time window (100 msec) after stimulus presentation. Surprisingly, disruption of the lateral occipital area resulted in increased performance scores and enhanced neural correlates of surface segregation. This facilitatory effect was also mainly found in an early time window (100 msec) after stimulus presentation. These results suggest a "push-pull" interaction in which dorsal and ventral extrastriate areas are being recruited or inhibited depending on stimulus category and task demands.

Use of Segregation Indices, Townsend Index, and Air Toxics Data to Assess Lifetime Cancer Risk Disparities in Metropolitan Charleston, South Carolina, USA

PubMed Central

Rice, LaShanta J.; Jiang, Chengsheng; Wilson, Sacoby M.; Burwell-Naney, Kristen; Samantapudi, Ashok; Zhang, Hongmei

2014-01-01

Background: Studies have demonstrated a relationship between segregation and level of education, occupational opportunities, and risk behaviors, yet a paucity of research has elucidated the association between racial residential segregation, socioeconomic deprivation, and lifetime cancer risk. Objectives: We examined estimated lifetime cancer risk from air toxics by racial composition, segregation, and deprivation in census tracts in Metropolitan Charleston. Methods: Segregation indices were used to measure the distribution of groups of people from different races within neighborhoods. The Townsend Index was used to measure economic deprivation in the study area. Poisson multivariate regressions were applied to assess the association of lifetime cancer risk with segregation indices and Townsend Index along with several sociodemographic measures. Results: Lifetime cancer risk from all pollution sources was 28 persons/million for half of the census tracts in Metropolitan Charleston. Isolation Index and Townsend Index both showed significant correlation with lifetime cancer risk from different sources. This significance still holds after adjusting for other sociodemographic measures in a Poisson regression, and these two indices have stronger effect on lifetime cancer risk compared to the effects of sociodemographic measures. Conclusions: We found that material deprivation, measured by the Townsend Index and segregation measured by the Isolation index, introduced high impact on lifetime cancer risk by air toxics at the census tract level. PMID:24852759

Residential Ethnic Segregation and Stroke Risk in Mexican Americans: The Brain Attack Surveillance in Corpus Christi Project

PubMed Central

Patel, Rajiv C; Baek, Jonggyu; Smith, Melinda A; Morgenstern, Lewis B; Lisabeth, Lynda D

2015-01-01

Objective Residential ethnic segregation may operate through multiple mechanisms to increase stroke risk. The current study evaluated if residential ethnic segregation was associated with stroke risk in a bi-ethnic population. Design Incident strokes were identified in Nueces County, Texas from 2000 to 2010. Residential ethnic segregation (range: 0–1) was derived for each census tract in the county (n=64) using 2000 U.S Census data, and categorized into: predominantly non-Hispanic white (NHW, <0.3); ethnically mixed (0.3–0.7); predominantly Mexican American (MA, >0.7). Multilevel Poisson regression models were fitted separately for NHWs and MAs to assess the association between residential ethnic segregation (predominantly NHW referent) and relative risk for stroke, adjusted for age category, sex and census tract-level median per capita income. Effect modification by age was also examined. Results In adjusted models, residential ethnic segregation was not associated with stroke risk in either ethnic group. Effect modification by age was significant in both groups. Young MAs and NHWs living in predominantly MA census tracts were at greater relative risk for stroke than those living in predominantly NHW census tracts, but this association was only significant for MAs [MAs: RR = 2.38 (95% CI: 1.31–4.31); NHWs: RR = 1.53 (95% CI: 0.92–2.52)]. Conclusion Our findings demonstrate that residential ethnic segregation may influence downstream stroke risk in young MAs. Pathways between residential ethnic segregation and stroke in young MAs should be explored. PMID:25812246

Future directions in research on institutional and interpersonal discrimination and children's health.

PubMed

Acevedo-Garcia, Dolores; Rosenfeld, Lindsay E; Hardy, Erin; McArdle, Nancy; Osypuk, Theresa L

2013-10-01

Research evidence indicates that 2 forms of racial discrimination-perceived interpersonal discrimination and racial/ethnic residential segregation (a form of institutional discrimination)-may influence children's health and disparities. Although research on these 2 forms of discrimination and health has primarily focused on adults, smaller bodies of work have documented that perceived interpersonal discrimination and segregation have a negative effect on infants' health, and that perceived interpersonal discrimination may negatively affect children's mental health. Three directions for research are (1) incorporating a life-course perspective into studies of discrimination and children's health, (2) linking residential segregation with geography-of-opportunity conceptual frameworks and measures, and (3) considering residential segregation along with segregation in other contexts that influence children's health (e.g., schools).

Morphology and luminosity segregation of galaxies in nearby loose groups

NASA Astrophysics Data System (ADS)

Girardi, M.; Rigoni, E.; Mardirossian, F.; Mezzetti, M.

2003-08-01

We study morphology and luminosity segregation of galaxies in loose groups. We analyze the two catalogs of groups identified in the Nearby Optical Galaxy (NOG) sample, by means of hierarchical and percolation ``friends-of-friends'' methods (HG and PG catalogs, respectively). In the first part of our analysis we consider 387 and 436 groups of HG and PG and compare morphology- (luminosity-) weighted to unweighted group properties: velocity dispersion, mean pairwise distance, and mean groupcentric distance of member galaxies. The second part of our analysis is based on two ensemble systems, one for each catalog, built by suitably combining together galaxies of all groups (1584 and 1882 galaxies for HG and PG groups). We find that earlier-type (brighter) galaxies are more clustered and lie closer to the group centers, both in position and in velocity, than later-type (fainter) galaxies. Spatial segregations are stronger than kinematical segregations. These effects are generally detected at the >˜ 3-sigma level. Luminosity segregation is shown to be independent of morphology segregation. Our main conclusions are strengthened by the detection of segregation in both hierarchical and percolation catalogs. Our results agree with a continuum of segregation properties of galaxies in systems, from low-mass groups to massive clusters.

77 FR 74690 - Notice of Amended Proposed Withdrawal; Partial Termination of Segregative Effect; Arizona...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-17

... Amended Proposed Withdrawal; Partial Termination of Segregative Effect; Arizona, California, Colorado... previously filed application to withdraw public lands in Arizona, California, Colorado, Nevada, New Mexico..., California, Colorado, Nevada, New Mexico, and Utah from settlement, sale, location, and entry under the...

Social Construction of a Segregated Urban Space and Its Effects on Education: A Case Study of the Balmikis of Delhi

ERIC Educational Resources Information Center

Ganguly, Sriti

2018-01-01

While segregation of Dalit habitations is assumed to be a characteristic primarily of the rural, studies indicate that a similar spatial organisation is reproduced in urban spaces as well where large populations, particularly of poor Dalits, continue to live in segregated settlements. This article draws on an exploratory study conducted in one…

Intelligibility of Target Signals in Sequential and Simultaneous Segregation Tasks

DTIC Science & Technology

2009-03-01

SUBJECT TERMS Informational masking; energetic masking, multimasker penalty, speech perception 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...alter- nation rates were high enough to directly interfere with the perception of the F0 values of the speech signals and that they thus disrupted the...segregation effects seen in this experiment and those in which stream segregation with tones was examined. Experiments examining the perception of

Cortical connectivity in fronto-temporal focal epilepsy from EEG analysis: A study via graph theory.

PubMed

Vecchio, Fabrizio; Miraglia, Francesca; Curcio, Giuseppe; Della Marca, Giacomo; Vollono, Catello; Mazzucchi, Edoardo; Bramanti, Placido; Rossini, Paolo Maria

2015-06-01

It is believed that effective connectivity and optimal network structure are essential for proper information processing in the brain. Indeed, functional abnormalities of the brain are found to be associated with pathological changes in connectivity and network structures. The aim of the present study was to explore the interictal network properties of EEG signals from temporal lobe structures in the context of fronto-temporal lobe epilepsy. To complete this aim, the graph characteristics of the EEG data of 17 patients suffering from focal epilepsy of the fronto-temporal type, recorded during interictal periods, were examined and compared in terms of the affected versus the unaffected hemispheres. EEG connectivity analysis was performed using eLORETA software in 15 fronto-temporal regions (Brodmann Areas BAs 8, 9, 10, 11, 20, 21, 22, 37, 38, 41, 42, 44, 45, 46, 47) on both affected and unaffected hemispheres. The evaluation of the graph analysis parameters, such as 'global' (characteristic path length) and 'local' connectivity (clustering coefficient) showed a statistically significant interaction among side (affected and unaffected hemisphere) and Band (delta, theta, alpha, beta, gamma). Duncan post hoc testing showed an increase of the path length in the alpha band in the affected hemisphere with respect to the unaffected one, as evaluated by an inter-hemispheric marker. The affected hemisphere also showed higher values of local connectivity in the alpha band. In general, an increase of local and global graph theory parameters in the alpha band was found in the affected hemisphere. It was also demonstrated that these effects were more evident in drug-free patients than in those undergoing pharmacological therapy. The increased measures in the affected hemisphere of both functional local segregation and global integration could result from the combination of overlapping mechanisms, including reactive neuroplastic changes seeking to maintain constant integration and segregation properties. This reactive neuroplastic mechanism seeking to maintain constant integration and segregation properties seems to be more evident in the absence of antiepileptic treatment. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Heats of Segregation of BCC Binaries from Ab Initio and Quantum Approximate Calculations

NASA Technical Reports Server (NTRS)

Good, Brian S.

2003-01-01

We compare dilute-limit segregation energies for selected BCC transition metal binaries computed using ab initio and quantum approximate energy methods. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent parameters. Quantum approximate segregation energies are computed with and without atomistic relaxation. Results are discussed within the context of segregation models driven by strain and bond-breaking effects. We compare our results with full-potential quantum calculations and with available experimental results.

Luminosity segregation in galaxy clusters as an indication of dynamical evolution

NASA Technical Reports Server (NTRS)

Baier, F. W.; Schmidt, K.-H.

1993-01-01

Theoretical models describing the dynamical evolution of self-gravitating systems predict a spatial mass segregation for more evolved systems, with the more massive objects concentrated toward the center of the configuration. From the observational point of view, however, the existence of mass segregation in galaxy clusters seems to be a matter of controversy. A special problem in this connection is the formation of cD galaxies in the centers of galaxy clusters. The most promising scenarios of their formation are galaxy cannibalism (merger scenario) and growing by cooling flows. It seems to be plausible to consider the swallowing of smaller systems by a dominant galaxy as an important process in the evolution of a cD galaxy. The stage of the evolution of the dominant galaxy should be reflected by the surrounding galaxy population, especially by possible mass segregation effects. Assuming that mass segregation is tantamount to luminosity segregation we analyzed luminosity segregation in roughly 40 cD galaxy clusters. Obviously there are three different groups of clusters: (1) clusters with luminosity segregation, (2) clusters without luminosity segregation, and (3) such objects exhibiting a phenomenon which we call antisegregation in luminosity, i.e. a deficiency of bright galaxies in the central regions of clusters. This result is interpreted in the sense of different degrees of mass segregation and as an indication for different evolution stages of these clusters. The clusters are arranged in the three segregation classes 2, 1, and 0 (S2 = strong mass segregation, S1 = moderate mass segregation, S0 = weak or absent mass segregation). We assume that a galaxy cluster starts its dynamical evolution after virialization without any radial mass segregation. Energy exchange during encounters of cluster members as well as merger processes between cluster galaxies lead to an increasing radial mass segregation in the cluster (S1). If a certain degree of segregation (S2) has been established, an essential number of slow-moving and relative massive cluster members in the center will be cannibalized by the initial brightest cluster galaxy. This process should lead to the growing of the predominate galaxy, which is accompanied by a diminution of the mass segregation (transition to S1 and S0, respectively) in the neighborhood of the central very massive galaxy. An increase of the areal density of brighter galaxies towards the outer cluster regions (antisegregation of luminosity), i.e. an extreme low degree of mass segregation was estimated for a substantial percentage of cD clusters. This result favors the cannibalism scenario for the formation of cD galaxies.

Incorporating convection into one-dimensional solute redistribution during crystal growth from the melt I. The steady-state solution

NASA Astrophysics Data System (ADS)

Yen, C. T.; Tiller, W. A.

1992-03-01

A one-dimensional mathematical analysis is made of the redistribution of solute which occurs during crystal growth from a convected melt. In this analysis, the important contribution from lateral melt convection to one-dimensional solute redistribution analysis is taken into consideration via an annihilation/creation term in the one-dimensional solute transport equation. Calculations of solute redistribution under steady-state conditions have been carried out analytically. It is found that this new solute redistribution model overcomes several weaknesses that occur when applying the Burton, Prim and Slichter solute segregation equation (1953) in real melt growth situations. It is also found that, with this correction, the diffusion coefficients for solute's in liquid silicon are now found to be in the same range as other liquid metal diffusion coefficients.

Inference of the Distribution of Selection Coefficients for New Nonsynonymous Mutations Using Large Samples

PubMed Central

Kim, Bernard Y.; Huber, Christian D.; Lohmueller, Kirk E.

2017-01-01

The distribution of fitness effects (DFE) has considerable importance in population genetics. To date, estimates of the DFE come from studies using a small number of individuals. Thus, estimates of the proportion of moderately to strongly deleterious new mutations may be unreliable because such variants are unlikely to be segregating in the data. Additionally, the true functional form of the DFE is unknown, and estimates of the DFE differ significantly between studies. Here we present a flexible and computationally tractable method, called Fit∂a∂i, to estimate the DFE of new mutations using the site frequency spectrum from a large number of individuals. We apply our approach to the frequency spectrum of 1300 Europeans from the Exome Sequencing Project ESP6400 data set, 1298 Danes from the LuCamp data set, and 432 Europeans from the 1000 Genomes Project to estimate the DFE of deleterious nonsynonymous mutations. We infer significantly fewer (0.38–0.84 fold) strongly deleterious mutations with selection coefficient |s| > 0.01 and more (1.24–1.43 fold) weakly deleterious mutations with selection coefficient |s| < 0.001 compared to previous estimates. Furthermore, a DFE that is a mixture distribution of a point mass at neutrality plus a gamma distribution fits better than a gamma distribution in two of the three data sets. Our results suggest that nearly neutral forces play a larger role in human evolution than previously thought. PMID:28249985

Heats of Segregation of BCC Metals Using Ab Initio and Quantum Approximate Methods

NASA Technical Reports Server (NTRS)

Good, Brian; Chaka, Anne; Bozzolo, Guillermo

2003-01-01

Many multicomponent alloys exhibit surface segregation, in which the composition at or near a surface may be substantially different from that of the bulk. A number of phenomenological explanations for this tendency have been suggested, involving, among other things, differences among the components' surface energies, molar volumes, and heats of solution. From a theoretical standpoint, the complexity of the problem has precluded a simple, unified explanation, thus preventing the development of computational tools that would enable the identification of the driving mechanisms for segregation. In that context, we investigate the problem of surface segregation in a variety of bcc metal alloys by computing dilute-limit heats of segregation using both the quantum-approximate energy method of Bozzolo, Ferrante and Smith (BFS), and all-electron density functional theory. In addition, the composition dependence of the heats of segregation is investigated using a BFS-based Monte Carlo procedure, and, for selected cases of interest, density functional calculations. Results are discussed in the context of a simple picture that describes segregation behavior as the result of a competition between size mismatch and alloying effects

Instabilities in rapid directional solidification under weak flow

NASA Astrophysics Data System (ADS)

Kowal, Katarzyna N.; Davis, Stephen H.; Voorhees, Peter W.

2017-12-01

We examine a rapidly solidifying binary alloy under directional solidification with nonequilibrium interfacial thermodynamics viz. the segregation coefficient and the liquidus slope are speed dependent and attachment-kinetic effects are present. Both of these effects alone give rise to (steady) cellular instabilities, mode S , and a pulsatile instability, mode P . We examine how weak imposed boundary-layer flow of magnitude |V | affects these instabilities. For small |V | , mode S becomes a traveling and the flow stabilizes (destabilizes) the interface for small (large) surface energies. For small |V | , mode P has a critical wave number that shifts from zero to nonzero giving spatial structure. The flow promotes this instability and the frequencies of the complex conjugate pairs each increase (decrease) with flow for large (small) wave numbers. These results are obtained by regular perturbation theory in powers of V far from the point where the neutral curves cross, but requires a modified expansion in powers of V1 /3 near the crossing. A uniform composite expansion is then obtained valid for all small |V | .

Diffusion of Mg dopant in metal-organic vapor-phase epitaxy grown GaN and AlxGa1-xN

NASA Astrophysics Data System (ADS)

Köhler, K.; Gutt, R.; Wiegert, J.; Kirste, L.

2013-02-01

Diffusion of the p-type dopant Mg in GaN and AlxGa1-xN which is accompanied by segregation and affected by transient effects in metal-organic vapor-phase epitaxy reactors is investigated. We have grown 110 nm thick Mg doped GaN and Al0.1Ga0.9N layers on top of undoped GaN and Al0.1Ga0.9N layers, respectively, in a temperature range between 925 °C and 1050 °C where we placed special emphasis on the lower temperature limit without diffusion to allow separation of Mg transients, diffusion, and segregation. Hereby, AlxGa1-xN layers enable monitoring of the resolution limit by secondary ion mass spectrometry analyses for the respective samples; therefore, thin AlxGa1-xN marker layers are incorporated in the thick GaN layers. We found an upper limit of 1.25 × 1019 cm-3 for diffusing Mg atoms in both sample types. Owing to the marked influence of Mg segregation in Al0.1Ga0.9N, diffusion is only seen by using a GaN cap on top of the Al0.1Ga0.9N layer sequence. Diffusion in Al0.1Ga0.9N is shown to be increased by about 25%-30% compared to GaN. Post growth annealing experiments under conditions equivalent to those used for growth of the Mg doped samples showed negligible diffusion. Comparing the results to well established findings on other doped III-V compounds, diffusion is explained by an interstitial-substitutional mechanism with a diffusion coefficient, which is concentration dependent. Analysis of the temperature dependent diffusivity revealed an activation energy of 5.0 eV for GaN:Mg and 5.2 eV for Al0.1Ga0.9N:Mg.

From HADES to PARADISE—atomistic simulation of defects in minerals

NASA Astrophysics Data System (ADS)

Parker, Stephen C.; Cooke, David J.; Kerisit, Sebastien; Marmier, Arnaud S.; Taylor, Sarah L.; Taylor, Stuart N.

2004-07-01

The development of the HADES code by Michael Norgett in the 1970s enabled, for the first time, the routine simulation of point defects in inorganic solids at the atomic scale. Using examples from current research we illustrate how the scope and applications of atomistic simulations have widened with time and yet still follow an approach readily identifiable with this early work. Firstly we discuss the use of the Mott-Littleton methodology to study the segregation of various isovalent cations to the (00.1) and (01.2) surfaces of haematite (agr-Fe2O3). The results show that the size of the impurities has a considerable effect on the magnitude of the segregation energy. We then extend these simulations to investigate the effect of the concentration of the impurities at the surface on the segregation process using a supercell approach. We consider next the effect of segregation to stepped surfaces illustrating this with recent work on segregation of La3+ to CaF2 surfaces, which show enhanced segregation to step edges. We discuss next the application of lattice dynamics to modelling point defects in complex oxide materials by applying this to the study of hydrogen incorporation into bgr-Mg2SiO4. Finally our attention is turned to a method for considering the surface energy of physically defective surfaces and we illustrate its approach by considering the low index surfaces of agr-Al2O3.

Surface Segregation Energies of BCC Binaries from Ab Initio and Quantum Approximate Calculations

NASA Technical Reports Server (NTRS)

Good, Brian S.

2003-01-01

We compare dilute-limit segregation energies for selected BCC transition metal binaries computed using ab initio and quantum approximate energy method. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent parameterization. Quantum approximate segregation energies are computed with and without atomistic relaxation. The ab initio calculations are performed without relaxation for the most part, but predicted relaxations from quantum approximate calculations are used in selected cases to compute approximate relaxed ab initio segregation energies. Results are discussed within the context of segregation models driven by strain and bond-breaking effects. We compare our results with other quantum approximate and ab initio theoretical work, and available experimental results.

Surface Segregation in Ternary Alloys

NASA Technical Reports Server (NTRS)

Good, Brian; Bozzolo, Guillermo H.; Abel, Phillip B.

2000-01-01

Surface segregation profiles of binary (Cu-Ni, Au-Ni, Cu-Au) and ternary (Cu-Au-Ni) alloys are determined via Monte Carlo-Metropolis computer simulations using the BFS method for alloys for the calculation of the energetics. The behavior of Cu or Au in Ni is contrasted with their behavior when both are present. The interaction between Cu and Au and its effect on the segregation profiles for Cu-Au-Ni alloys is discussed.

Current viewpoints on oxide adherence mechanisms

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Browning, R.

1985-01-01

Additional hot stage Auger experiments have provided surface segregation data for NiCrAl + or - Y or Zr alloys in agreement with other investigations. This data, combined with experimental and theoretical evidence of the Al2O3-metal bond strength, is presented in support of a chemical mechanism of Al2O3 scale adhesion. Both the detrimental effects of sulfur segregation and the beneficial effects of dopant segregation may be important. Chemical features of the dopants are compared in light of these proposed mechanisms, namely delta H sub f (sulfide), delta H sub f (oxide), electron orbital configuration, and insolubility in Ni.

Determination of carrier concentration and compensation microprofiles in GaAs

NASA Technical Reports Server (NTRS)

Jastrzebski, L.; Lagowski, J.; Walukiewicz, W.; Gatos, H. C.

1980-01-01

Simultaneous microprofiling of semiconductor free carrier, donor, and acceptor concentrations was achieved for the first time from the absolute value of the free carrier absorption coefficient and its wavelength dependence determined by IR absorption in a scanning mode. Employing Ge- and Si-doped melt-grown GaAs, striking differences were found between the variations of electron concentration and those of ionized impurity concentrations. These results showed clearly that the electronic characteristics of this material are controlled by amphoteric doping and deviations from stoichiometry rather than by impurity segregation.

Perpetuation Theory and the Long-Term Effects of School Desegregation.

ERIC Educational Resources Information Center

Wells, Amy Stuart; Crain, Robert L.

1994-01-01

This review brings together 21 studies on the long-term effects of school desegregation on the life chances of African American students. These studies draw on perpetuation theory, a macro-micro theory of racial segregation. They support the idea that interracial contact in school can help blacks overcome perpetual segregation. (SLD)

Effect of Tin, Copper and Boron on the Hot Ductility of 20CrMnTi Steel between 650 °C and 1100 °C

NASA Astrophysics Data System (ADS)

Peng, Hong-bing; Chen, Wei-qing; Chen, Lie; Guo, Dong

2015-02-01

The hot ductility of 20CrMnTi steel with x% tin, y% copper and z ppm boron (x = 0, 0.02; y = 0, 0.2; z = 0, 60) was investigated. The results show that tin and copper in 20CrMnTi steel are detrimental to its hot ductility while adding boron can eliminate the adverse effect and enhance hot ductility greatly. Tin is found to segregate to the boundaries tested by EPMA in 20CrMnTi steel containing tin and copper and tin-segregation is suppressed by adding boron, moreover, copper was found not to segregate to boundaries, however, fine copper sulfide was found from carbon extraction replicas using TEM. The adverse effect of tin and copper on the hot ductility was due mainly to tin segregation and fine copper sulfide in the steel. The proeutectoid ferrite film precipitating along the austenite grain boundary causes the ductility trough of the three examined steels. Tin and copper in 20CrMnTi steel can retard the occurrence of dynamic recrystallization (DRX) while boron-addition can compensate for that change. The beneficial effect of boron on 20CrMnTi steel containing tin and copper might be ascribed to the fact that boron segregates to grain boundaries, accelerates onset of DRX, retards austenite/ferrite transformation and promotes intragranular nucleation of ferrite.

Atomic scale study of grain boundary segregation before carbide nucleation in Ni-Cr-Fe Alloys

NASA Astrophysics Data System (ADS)

Li, Hui; Xia, Shuang; Liu, Wenqing; Liu, Tingguang; Zhou, Bangxin

2013-08-01

Three dimensional chemical information concerning grain boundary segregation before carbide nucleation was characterized by atom probe tomography in two Ni-Cr-Fe alloys which were aged at 500 °C for 0.5 h after homogenizing treatment. B, C and Si atoms segregation at grain boundary in Alloy 690 was observed. B, C, N and P atoms segregation at grain boundary in 304 austenitic stainless steel was observed. C atoms co-segregation with Cr atoms at the grain boundaries both in Alloy 690 and 304 austenitic stainless steel was found, and its effect on the carbide nucleation was discussed. The amount of each segregated element at grain boundaries in the two Ni-Cr-Fe alloys were analyzed quantitatively. Comparison of the grain boundary segregation features of the two Ni-Cr-Fe alloys were carried out based on the experimental results. The impurity and solute atoms segregate inhomogeneously in the same grain boundary both in 304 SS and Alloy 690. The grain boundary segregation tendencies (Sav) are B (11.8 ± 1.4) > P (5.4 ± 1.4) > N (4.7 ± 0.3) > C (3.7 ± 0.4) in 304 SS, and B (6.9 ± 0.9) > C (6.7 ± 0.4) > Si (1.5 ± 0.2) in Alloy 690. Cr atoms may co-segregate with C atoms at grain boundaries before carbide nucleation at the grain boundaries both in 304 SS and Alloy 690. Ni atoms generally deplete at grain boundary both in 304 SS and Alloy 690. The literature shows that the Ni atoms may co-segregate with P atoms at grain boundaries [28], but the P atoms segregation do not leads to Ni segregation in the current study. In the current study, Fe atoms may segregate or deplete at grain boundary in Alloy 690. But Fe atoms generally deplete at grain boundary in 304 SS. B atoms have the strongest grain boundary segregation tendency both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of B in 304 SS is higher than in Alloy 690. C atoms are easy to segregate at grain boundaries both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of C in Alloy 690 is higher than in 304 SS, due to the higher bulk C concentration and the site competition of P atoms which segregate at grain boundary [29,30]. It is imply that the segregation tendency is influenced by the bulk concentration of the segregates. Si atoms slightly segregate at grain boundaries in Alloy 690, but do not segregate at grain boundaries in 304 SS. N and P atoms segregate at grain boundary in 304 SS, and their segregation Gibbs free energy are similar. N atoms may be exhausted by the TiN precipitated in the matrix and can not be observed in the grain boundary of Alloy 690 [19]. Mn atoms deplete at grain boundary in 304 SS. This phenomenon is similar to that of proton irradiation induced segregation in 304 SS [32]. B, C, N, P segregation Gibbs energies are similar both in 304 SS and Alloy 690. B and C atoms segregate at grain boundary both in Alloy 690 and 304 SS, P and N segregate at grain boundary in 304 SS. Si atoms segregate at grain boundary in Alloy 690, but do not segregate at grain boundary in 304 SS. Cr enriches at grain boundary both in Alloy 690 and 304 SS, although carbide does not nucleate. Ni and Fe may segregate, deplete or homogeneously distribute at grain boundary in Alloy 690, but they deplete at grain boundary in 304 SS. C and Cr atoms co-segregate at grain boundaries before carbide nucleation in Alloy 690 and 304 SS. Combination with other results in literatures, the evolution of Cr concentration at grain boundary should be enrichment at grain boundary before carbide nucleation, depletion at grain boundary after carbide precipitation, and healing after obvious growth of carbide. After aging treatment at 500 °C for 0.5 h, the total reduction of grain boundary free energy due to segregation is 27.489 kJ/mol for Alloy 690 and 45.207 kJ/mol for 304.

First-Principles Study of Mo Segregation in MoNi(111): Effects of Chemisorbed Atomic Oxygen

PubMed Central

Yu, Yanlin; Xiao, Wei; Wang, Jianwei; Wang, Ligen

2015-01-01

Segregation at metal alloy surfaces is an important issue because many electrochemical and catalytic properties are directly correlated to the surface composition. We have performed density functional theory calculations for Mo segregation in MoNi(111) in the presence of chemisorbed atomic oxygen. In particular, the coverage dependence and possible adsorption-induced segregation phenomena are addressed by investigating segregation energies of the Mo atom in MoNi(111). The theoretical calculated results show that the Mo atom prefers to be embedded in the bulk for the clean MoNi(111), while it segregates to the top-most layer when the oxygen coverage is thicker than 1/9 monolayer (ML). Furthermore, we analyze the densities of states for the clean and oxygen-chemisorbed MoNi(111), and see a strong covalent bonding between Mo d-band states and O p-states. The present study provides valuable insight for exploring practical applications of Ni-based alloys as hydrogen evolution electrodes. PMID:28787811

The importance of sulfur for the behavior of highly-siderophile elements during Earth's differentiation

NASA Astrophysics Data System (ADS)

Laurenz, Vera; Rubie, David C.; Frost, Daniel J.; Vogel, Antje K.

2016-12-01

The highly siderophile elements (HSEs) are widely used as geochemical tracers for Earth's accretion and core formation history. It is generally considered that core formation strongly depleted the Earth's mantle in HSEs, which were subsequently replenished by a chondritic late veneer. However, open questions remain regarding the origin of suprachondritic Ru/Ir and Pd/Ir ratios that are thought to be characteristic for the primitive upper mantle. In most core-formation models that address the behavior of the HSEs, light elements such as S entering the core have not been taken into account and high P-T experimental data for S-bearing compositions are scarce. Here we present a comprehensive experimental study to investigate the effect of increasing S concentration in the metal on HSE metal-silicate partitioning at 2473 K and 11 GPa. We show that the HSEs become less siderophile with increasing S concentrations in the metal, rendering core-forming metal less efficient in removing the HSEs from the mantle if S is present. Furthermore, we investigated the FeS sulfide-silicate partitioning of the HSEs as a function of pressure (7-21 GPa) and temperature (2373-2673 K). The sulfide-silicate partition coefficient for Pt increases strongly with P, whereas those for Pd, Ru and Ir all decrease. The combined effect is such that above ∼20 GPa Ru becomes less chalcophile than Pt, which is opposite to their behavior in the metal-silicate system where Ru is always more siderophile than Pt. The newly determined experimental results are used in a simple 2-stage core formation model that takes into account the effect of S on the behavior of the HSEs during core formation. Results of this model show that segregation of a sulfide liquid to the core from a mantle with substantial HSE concentrations plays a key role in reproducing Earth's mantle HSE abundances. As Ru and Pd are less chalcophile than Pt and Ir at high P-T, some Ru and Pd remain in the mantle after sulfide segregation. Addition of the late veneer then raised the concentrations of all HSE to their current levels. Suprachondritic Ru/Ir and Pd/Ir ratios of the mantle can thus be explained by a combination of sulfide segregation together with the addition of a late veneer without the need to invoke unknown chondritic material.

Genotypic gain with simultaneous selection of production, nutrition, and culinary traits in cowpea crosses and backcrosses using mixed models.

PubMed

Oliveira, D G; Rocha, M M; Damasceno-Silva, K J; Sá, F V; Lima, L R L; Resende, M D V

2017-08-17

The aim of this study was to estimate the genotypic gain with simultaneous selection of production, nutrition, and culinary traits in cowpea crosses and backcrosses and to compare different selection indexes. Eleven cowpea populations were evaluated in a randomized complete block design with four replications. Fourteen traits were evaluated, and the following parameters were estimated: genotypic variation coefficient, genotypic determination coefficient, experimental quality indicator and selection reliability, estimated genotypic values ​​- BLUE, genotypic correlation coefficient among traits, and genotypic gain with simultaneous selection of all traits. The genotypic gain was estimated based on tree selection indexes: classical, multiplicative, and the sum of ranks. The genotypic variation coefficient was higher than the environmental variation coefficient for the number of days to start flowering, plant type, the weight of one hundred grains, grain index, and protein concentration. The majority of the traits presented genotypic determination coefficient from medium to high magnitude. The identification of increases in the production components is associated with decreases in protein concentration, and the increase in precocity leads to decreases in protein concentration and cooking time. The index based on the sum of ranks was the best alternative for simultaneous selection of traits in the cowpea segregating populations resulting from the crosses and backcrosses evaluated, with emphasis on the F 4 BC 12 , F 4 C 21 , and F 4 C 12 populations, which had the highest genotypic gains.

The Effect of Dilution on Microsegregation in AWS ER NiCrMo-14 Alloy Welding Claddings

NASA Astrophysics Data System (ADS)

Miná, Émerson Mendonça; da Silva, Yuri Cruz; Dille, Jean; Silva, Cleiton Carvalho

2016-12-01

Dilution and microsegregation are phenomena inherent to claddings, which, in turn, directly affect their main properties. This study evaluated microsegregation in the fusion zone with different dilution levels. The overlays were welded by the TIG cold wire feed process. Dilution was calculated from the geometric characteristics of the claddings and from the conservation of mass equation using chemical composition measurements. Microsegregation was calculated using energy dispersive X-ray spectroscopy measurements of the dendrites and the chemical composition of the fusion zone. The dilution of the claddings was increased by reducing the wire feed rate. Fe showed potential to be incorporated into the solid phase ( k > 1), and this increased with the increase of dilution. Mo, in turn, was segregated into the liquid phase ( k < 1) and also increased with the increase of dilution. However, Cr and W showed a slight decrease in their partition coefficients ( k) with the increase of dilution.

The mismatch negativity as a measure of auditory stream segregation in a simulated "cocktail-party" scenario: effect of age.

PubMed

Getzmann, Stephan; Näätänen, Risto

2015-11-01

With age the ability to understand speech in multitalker environments usually deteriorates. The central auditory system has to perceptually segregate and group the acoustic input into sequences of distinct auditory objects. The present study used electrophysiological measures to study effects of age on auditory stream segregation in a multitalker scenario. Younger and older adults were presented with streams of short speech stimuli. When a single target stream was presented, the occurrence of a rare (deviant) syllable among a frequent (standard) syllable elicited the mismatch negativity (MMN), an electrophysiological correlate of automatic deviance detection. The presence of a second, concurrent stream consisting of the deviant syllable of the target stream reduced the MMN amplitude, especially when located nearby the target stream. The decrease in MMN amplitude indicates that the rare syllable of the target stream was less perceived as deviant, suggesting reduced stream segregation with decreasing stream distance. Moreover, the presence of a concurrent stream increased the MMN peak latency of the older group but not that of the younger group. The results provide neurophysiological evidence for the effects of concurrent speech on auditory processing in older adults, suggesting that older adults need more time for stream segregation in the presence of concurrent speech. Copyright © 2015 Elsevier Inc. All rights reserved.

Gibbsian segregating alloys driven by thermal and concentration gradients: A potential grazing collector optics used in EUV lithography

NASA Astrophysics Data System (ADS)

Qiu, Huatan

A critical issue for EUV lithography is the minimization of collector degradation from intense plasma erosion and debris deposition. Reflectivity and lifetime of the collector optics will be heavily dependent on surface chemistry interactions between fuels and various mirror materials, in addition to high-energy ion and neutral particle erosion effects. An innovative Gibbsian segregation (GS) concept has been developed for being a self-healing, erosion-resistant collector optics. A Mo-Au GS alloy is developed on silicon using a DC dual-magnetron co-sputtering system in order for enhanced surface roughness properties, erosion resistance, and self-healing characteristics to maintain reflectivity over a longer period of mirror lifetime. A thin Au segregating layer will be maintained through segregation during exposure, even though overall erosion is taking place. The reflective material, Mo, underneath the segregating layer will be protected by this sacrificial layer which is lost due to preferential sputtering. The two dominant driving forces, thermal (temperature) and surface concentration gradient (surface removal flux), are the focus of this work. Both theoretical and experimental efforts have been performed to prove the effectiveness of the GS alloy used as EUV collection optics, and to elucidate the underlying physics behind it. The segregation diffusion, surface balance, erosion, and in-situ reflectivity will be investigated both qualitatively and quantitatively. Results show strong enhancement effect of temperature on GS performance, while only a weak effect of surface removal rate on GS performance. When equilibrium between GS and erosion is reached, the surface smoothness could be self-healed and reflectivity could be maintained at an equilibrium level, instead of continuously dropping down to an unacceptable level as conventional optic mirrors behave. GS process also shows good erosion resistance. The effectiveness of GS alloy as EUV mirror is dependent on the temperature and surface removal rate. The Mo-Au GS alloy could be effective at elevated temperature as the potential grazing mirror as EUV collector optics.

Residential Segregation,Spatial Mismatch and Economic Growth across US Metropolitan Area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, Dr Harrison; Li, Huiping

2013-01-01

Numerous studies have demonstrated the detrimental influence of residential segregation on poor inner-city residents. This study examines the impact of residential segregation on the welfare of populations in US metropolitan areas using economic growth as the indicator. Panel data of US metropolitan areas spanning 25 years, 1980 2005, are used to analyze the effect of segregation on economic growth. The results show that both racial and skill segregation have a negative impact on short and long-term economic growth, which have increased over time. Further, the negative impact of the variables associated with spatial mismatch is also revealed. The results clearlymore » point to the need for mobility policies that favor non-White households and comprehensive strategies that promote economic opportunities in low-resource communities in the US.« less

30 CFR 281.42 - Effect of assignment on particular lease.

Code of Federal Regulations, 2010 CFR

2010-07-01

... OCS mineral created by the segregation of a lease under paragraph (a) of this section shall continue... thereafter as minerals are produced from the portion of the lease created by segregation in accordance with...

Three-dimensional analysis of flow and segregation in vertical Bridgman crystal growth under axial and transversal magnetic fields

NASA Astrophysics Data System (ADS)

Lan, C. W.; Lee, I. F.; Yeh, B. C.

2003-07-01

Three-dimensional simulation, both pseudo-steady and time-dependent states, is carried out to illustrate the effects of magnetic fields on the flow and segregation in a vertical Bridgman crystal growth. With an axial magnetic field in a perfectly vertical growth, the calculated results are in good agreement with those obtained by a two-dimensional axisymmetric model. The asymptotic scaling of flow damping is also consistent with the boundary layer approximation regardless to the magnetic orientation. Radial and axial segregations are further discussed concluding that radial segregation could be severe if the flow damping is not adequate. Moreover, there is a regime of enhanced global dopant mixing due to the flow stretching by the axial field. Accordingly, the transversal field is more effective in pushing the growth to the diffusion-controlled limit and suppressing the asymmetric global flow due to ampule tilting.

Integrated schools, segregated curriculum: effects of within-school segregation on adolescent health behaviors and educational aspirations.

PubMed

Walsemann, Katrina M; Bell, Bethany A

2010-09-01

We examined the extent to which within-school segregation, as measured by unevenness in the distribution of Black and White adolescents across levels of the English curriculum (advanced placement-international baccalaureate-honors, general, remedial, or no English), was associated with smoking, drinking, and educational aspirations, which previous studies found are related to school racial/ethnic composition. We analyzed data from wave 1 of the National Longitudinal Study of Adolescent Health, restricting our sample to non-Hispanic Blacks (n=2731) and Whites (n=4158) who from 1994 to 1995 attended high schools that enrolled Black and White students. White female students had higher predicted probabilities of smoking or drinking than did Black female students; the largest differences were in schools with high levels of within-school segregation. Black male students had higher predicted probabilities of high educational aspirations than did White male students in schools with low levels of within-school segregation; this association was attenuated for Black males attending schools with moderate or high levels of within-school segregation. Our results provide evidence that within-school segregation may influence both students' aspirations and their behaviors.

Effect of H2O on metal-silicate partitioning of Ni, Co, V, Cr, Mn and Fe: Implications for the oxidation state of the Earth and Mars

NASA Astrophysics Data System (ADS)

Clesi, V.; Bouhifd, M. A.; Bolfan-Casanova, N.; Manthilake, G.; Fabbrizio, A.; Andrault, D.

2016-11-01

This study investigates the metal-silicate partitioning of Ni, Co, V, Cr, Mn and Fe during core mantle differentiation of terrestrial planets under hydrous conditions. For this, we equilibrated a molten hydrous CI chondrite model composition with various Fe-rich alloys in the system Fe-C-Ni-Co-Si-S in a multi-anvil over a range of P, T, fO2 and water content (5-20 GPa, 2073-2500 K, from 1 to 5 log units below the iron-wüstite (IW) buffer and for XH2O varying from 500 ppm to 1.5 wt%). By comparing the present experiments with the available data sets on dry systems, we observes that the effect of water on the partition coefficients of moderately siderophile elements is only moderate. For example, for iron we observed a decrease in the partition coefficient of Fe (Dmet/silFe) from 9.5 to 4.3, with increasing water content of the silicate melt, from 0 to 1.44 wt%, respectively. The evolution of metal-silicate partition coefficients of Ni, Co, V, Cr, Mn and Fe are modelled based on sets of empirical parameters. These empirical models are then used to refine the process of core segregation during accretion of Mars and the Earth. It appears that the likely presence of 3.5 wt% water on Mars during the core-mantle segregation could account for ∼74% of the FeO content of the Martian mantle. In contrast, water does not play such an important role for the Earth; only 4-6% of the FeO content of its mantle could be due to the water-induced Fe-oxidation, for a likely initial water concentration of 1.8 wt%. Thus, in order to reproduce the present-day FeO content of 8 wt% in the mantle, the Earth could initially have been accreted from a large fraction (between 85% and 90%) of reducing bodies (similar to EH chondrites), with 10-15% of the Earth's mass likely made of more oxidized components that introduced the major part of water and FeO to the Earth. This high proportion of enstatite chondrites in the original constitution of the Earth is consistent with the 17O,48Ca,50Ti,62Ni and 90Mo isotopic study by Dauphas et al. (2014). If we assume that the CI-chondrite was oxidized during accretion, its intrinsically high water content suggests a maximum initial water concentration in the range of 1.2-1.8 wt% for the Earth, and 2.5-3.5 wt% for Mars.

Segregation effects during solidification in weightless melts. [effects of evaporation and solidification on crystalization

NASA Technical Reports Server (NTRS)

Li, C.

1975-01-01

Computer programs are developed and used in the study of the combined effects of evaporation and solidification in space processing. The temperature and solute concentration profiles during directional solidification of binary alloys with surface evaporation were mathematically formulated. Computer results are included along with an econotechnical model of crystal growth. This model allows: prediction of crystal size, quality, and cost; systematic selection of the best growth equipment or alloy system; optimization of growth or material parameters; and a maximization of zero-gravity effects. Segregation in GaAs crystals was examined along with vibration effects on GaAs crystal growth. It was found that a unique segregation pattern and strong convention currents exist in GaAs crystal growth. Some beneficial effects from vibration during GaAs growth were discovered. The implications of the results in space processing are indicated.

76 FR 81524 - Public Land Order No. 7786; Revocation of Secretarial Order Dated October 8, 1907; Montana

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-28

... laws, subject to other segregations of record. DATES: Effective Date: December 28, 2011. FOR FURTHER... existing rights, the provisions of existing withdrawals, other segregations of record, and the requirements...

Differential segregation in a cell-cell contact interface: the dynamics of the immunological synapse.

PubMed Central

Burroughs, Nigel John; Wülfing, Christoph

2002-01-01

Receptor-ligand couples in the cell-cell contact interface between a T cell and an antigen-presenting cell form distinct geometric patterns and undergo spatial rearrangement within the contact interface. Spatial segregation of the antigen and adhesion receptors occurs within seconds of contact, central aggregation of the antigen receptor then occurring over 1-5 min. This structure, called the immunological synapse, is becoming a paradigm for localized signaling. However, the mechanisms driving its formation, in particular spatial segregation, are currently not understood. With a reaction diffusion model incorporating thermodynamics, elasticity, and reaction kinetics, we examine the hypothesis that differing bond lengths (extracellular domain size) is the driving force behind molecular segregation. We derive two key conditions necessary for segregation: a thermodynamic criterion on the effective bond elasticity and a requirement for the seeding/nucleation of domains. Domains have a minimum length scale and will only spontaneously coalesce/aggregate if the contact area is small or the membrane relaxation distance large. Otherwise, differential attachment of receptors to the cytoskeleton is required for central aggregation. Our analysis indicates that differential bond lengths have a significant effect on synapse dynamics, i.e., there is a significant contribution to the free energy of the interaction, suggesting that segregation by differential bond length is important in cell-cell contact interfaces and the immunological synapse. PMID:12324401

Perceptual compression of magnitude-detected synthetic aperture radar imagery

NASA Technical Reports Server (NTRS)

Gorman, John D.; Werness, Susan A.

1994-01-01

A perceptually-based approach for compressing synthetic aperture radar (SAR) imagery is presented. Key components of the approach are a multiresolution wavelet transform, a bit allocation mask based on an empirical human visual system (HVS) model, and hybrid scalar/vector quantization. Specifically, wavelet shrinkage techniques are used to segregate wavelet transform coefficients into three components: local means, edges, and texture. Each of these three components is then quantized separately according to a perceptually-based bit allocation scheme. Wavelet coefficients associated with local means and edges are quantized using high-rate scalar quantization while texture information is quantized using low-rate vector quantization. The impact of the perceptually-based multiresolution compression algorithm on visual image quality, impulse response, and texture properties is assessed for fine-resolution magnitude-detected SAR imagery; excellent image quality is found at bit rates at or above 1 bpp along with graceful performance degradation at rates below 1 bpp.

Surface chemistry, microstructure and friction properties of some ferrous-base metallic glasses at temperatures to 750 C

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron spectroscopy analysis, transmission electron microscopy, diffraction studies, and sliding friction experiments were conducted with ferrous-base metallic glasses in sliding contact with aluminum oxide at temperatures from room to 750 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on the friction properties, surface chemistry, and microstructure of metallic glasses. The relative concentrations of the various constituents at the surface of the sputtered specimens were very different from the normal bulk compositions. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and silicon oxide at 350 C and boron nitride above 500 C. The coefficient of friction increased with increasing temperature to 350 C. Above 500 C the coefficient of friction decreased rapidly. The segregation of contaminants may be responsible for the friction behavior.

Thermal, spectroscopic and laser properties of Nd3+ in gadolinium scandium gallium garnet crystal produced by optical floating zone method

NASA Astrophysics Data System (ADS)

Tian, Li; Wang, Shuxian; Wu, Kui; Wang, Baolin; Yu, Haohai; Zhang, Huaijin; Cai, Huaqiang; Huang, Hui

2013-12-01

A neodymium-doped gadolinium scandium gallium garnet (Nd:GSGG) single crystal with dimensions of Φ 5 × 20 mm2 has been grown by means of optical floating zone (OFZ). X-ray powder diffraction (XRPD) result shows that the as-grown Nd:GSGG crystal possesses a cubic structure with space group Ia3d and a cell parameter of a = 1.2561 nm. Effective elemental segregation coefficients of the Nd:GSGG as-grown crystal were calculated by using X-ray fluorescence (XRF). The thermal properties of the Nd:GSGG crystal were systematically studied by measuring the specific heat, thermal expansion and thermal diffusion coefficient, and the thermal conductivity of this crystal was calculated. The absorption and luminescence spectra of Nd:GSGG were measured at room temperature (RT). By using the Judd-Ofelt (J-O) theory, the theoretical radiative lifetime was calculated and compared with the experimental result. Continuous wave (CW) laser performance was achieved with the Nd:GSGG at the wavelength of 1062 nm when it was pumped by a laser diode (LD). A maximum output power of 0.792 W at 1062 nm was obtained with a slope efficiency of 11.89% under a pump power of 7.36 W, and an optical-optical conversion efficiency of 11.72%.

Effect of thermal and thermo-mechanical cycling on the boron segregation behavior in the coarse-grained heat-affected zone of low-alloy steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sanghoon; Kang, Yongjoon; Lee, Changhee, E-mail: chlee@hanyang.ac.kr

The boron segregation behavior in the coarse-grained heat-affected zone (CGHAZ) of 10 ppm boron-added low-alloy steel during the welding cycle was investigated by taking the changes in the microstructure and hardness into account. Various CGHAZs were simulated with a Gleeble system as a function of the heat input and external stress, and the boron segregation behavior was analyzed by secondary ion mass spectrometry (SIMS) and particle tracking autoradiography (PTA). The segregation of boron was found to initially increase, and then decrease with an increase in the heat input. This is believed to be due to the back-diffusion of boron withmore » an increase in the exposure time at high temperature after non-equilibrium grain boundary segregation. The grain boundary segregation of boron could be decreased by an external stress applied during the welding cycle. Such behavior may be due to an increase in the grain boundary area as a result of the grain size reduction induced by the external stress. - Highlights: • Boron segregation behavior in the CGHAZ of low-alloy steel during a welding cycle was investigated. • Various CGHAZs were simulated with a Gleeble system as a function of the heat input and external stress. • Boron segregation behavior was analyzed using SIMS and PTA techniques.« less

DEM simulation of the granular Maxwell's Demon under zero gravity

NASA Astrophysics Data System (ADS)

Wang, Wenguang; Zhou, Zhigang; Zong, Jin; Hou, Meiying

2017-06-01

In this work, granular segregation in a two-compartment cell (Maxwell's Demon) under zero gravity is studied numerically by DEM simulation for comparison with the experimental observation in satellite SJ-10. The effect of three parameters: the total number of particlesN, the excitation strengthΓ, and the position of the window coupling the two compartments, on the segregationɛ and the waiting timeτ are investigated. In the simulation, non-zero segregation under zero gravity is obtained, and the segregation ɛ is found independent of the excitation strengthΓ. The waiting time τ, however, depends strongly onΓ. For higher acceleration Γ, |ɛi| reaches steady state valueɛ faster.

Heats of Segregation of BCC Binaries from ab Initio and Quantum Approximate Calculations

NASA Technical Reports Server (NTRS)

Good, Brian S.

2004-01-01

We compare dilute-limit heats of segregation for selected BCC transition metal binaries computed using ab initio and quantum approximate energy methods. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent LMTO-based parameters. Quantum approximate segregation energies are computed with and without atomistic relaxation, while the ab initio calculations are performed without relaxation. Results are discussed within the context of a segregation model driven by strain and bond-breaking effects. We compare our results with full-potential quantum calculations and with available experimental results.

Investigation into nanoscratching mechanical response of AlCrCuFeNi high-entropy alloys using atomic simulations

NASA Astrophysics Data System (ADS)

Wang, Zining; Li, Jia; Fang, QiHong; Liu, Bin; Zhang, Liangchi

2017-09-01

The mechanical behaviors and deformation mechanisms of scratched AlCrCuFeNi high entropy alloys (HEAs) have been studied by molecular dynamics (MD) simulations, in terms of the scratching forces, atomic strain, atomic displacement, microstructural evolution and dislocation density. The results show that the larger tangential and normal forces and higher friction coefficient take place in AlCrCuFeNi HEA due to its outstanding strength and hardness, and high adhesion and fracture toughness over the pure metal materials. Moreover, the stacking fault energy (SFE) in HEA increases the probability to initiate dislocation and twinning, which is conducive to the formation of complex deformation modes. Compared to the single element metal workpieces, the segregation potency of solutes into twinning boundary (TB) is raised due to the decreasing segregation energy of TB, resulting in the stronger solute effects on improving twinning properties for HEA workpiece. The higher dislocation density and the more activated slipping planes lead to the outstanding plasticity of AlCrCuFeNi HEA. The solute atoms as barriers to hinder the motion of dislocation and the severe lattice distortion to suppress the free slipping of dislocation are significantly stronger obstacles to strengthen HEA. The excellent comprehensive scratching properties of the bulk AlCrCuFeNi HEAs are associated with the combined effects of multiple strengthening mechanisms, such as dislocation strengthening, deformation twinning strengthening as well as solute strengthening. This work provides a basis for further understanding and tailoring SFE in mechanical properties and deformation mechanism of HEAs, which maybe facilitate the design and preparation of new HEAs with high performance.

Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects.

PubMed

Titus, Michael S; Rhein, Robert K; Wells, Peter B; Dodge, Philip C; Viswanathan, Gopal Babu; Mills, Michael J; Van der Ven, Anton; Pollock, Tresa M

2016-12-01

It has long been known that solute segregation at crystalline defects can have profound effects on material properties. Nevertheless, quantifying the extent of solute segregation at nanoscale defects has proven challenging due to experimental limitations. A combined experimental and first-principles approach has been used to study solute segregation at extended intermetallic phases ranging from 4 to 35 atomic layers in thickness. Chemical mapping by both atom probe tomography and high-resolution scanning transmission electron microscopy demonstrates a markedly different composition for the 4-atomic-layer-thick phase, where segregation has occurred, compared to the approximately 35-atomic-layer-thick bulk phase of the same crystal structure. First-principles predictions of bulk free energies in conjunction with direct atomistic simulations of the intermetallic structure and chemistry demonstrate the breakdown of bulk thermodynamics at nanometer dimensions and highlight the importance of symmetry breaking due to the proximity of interfaces in determining equilibrium properties.

Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects

PubMed Central

Titus, Michael S.; Rhein, Robert K.; Wells, Peter B.; Dodge, Philip C.; Viswanathan, Gopal Babu; Mills, Michael J.; Van der Ven, Anton; Pollock, Tresa M.

2016-01-01

It has long been known that solute segregation at crystalline defects can have profound effects on material properties. Nevertheless, quantifying the extent of solute segregation at nanoscale defects has proven challenging due to experimental limitations. A combined experimental and first-principles approach has been used to study solute segregation at extended intermetallic phases ranging from 4 to 35 atomic layers in thickness. Chemical mapping by both atom probe tomography and high-resolution scanning transmission electron microscopy demonstrates a markedly different composition for the 4–atomic-layer–thick phase, where segregation has occurred, compared to the approximately 35–atomic-layer–thick bulk phase of the same crystal structure. First-principles predictions of bulk free energies in conjunction with direct atomistic simulations of the intermetallic structure and chemistry demonstrate the breakdown of bulk thermodynamics at nanometer dimensions and highlight the importance of symmetry breaking due to the proximity of interfaces in determining equilibrium properties. PMID:28028543

High-Efficiency Inhibition of Gravity Segregation in Al-Bi Immiscible Alloys by Adding Lanthanum

NASA Astrophysics Data System (ADS)

Jia, Peng; Zhang, Jinyang; Geng, Haoran; Teng, Xinying; Zhao, Degang; Yang, Zhongxi; Wang, Yi; Hu, Song; Xiang, Jun; Hu, Xun

2018-05-01

The inhibition of gravity segregation has been a long-standing challenge in fabrication and applications of homogeneous immiscible alloys. Therefore, the effect of rare-earth La on the gravity segregation of Al-Bi immiscible alloys was investigated to understand the homogenization mechanism. The results showed that the addition of La can completely suppress the gravity segregation. This is attributed to the nucleation of Bi-rich liquid phase on the in-situ produced LaBi2 phase and the change of the shape of LaBi2@Bi droplets. In addition, a novel strategy is developed to prepare the homogeneous immiscible alloys through the addition of rare-earth elements. This strategy not only is applicable to other immiscible alloys, but also is conducive to finding more elements to suppress the gravity segregation. This study provided a useful reference for the fabrication of the homogeneous immiscible alloys.

Influence of Secondary Cooling Mode on Solidification Structure and Macro-segregation Behavior for High-carbon Continuous Casting Bloom

NASA Astrophysics Data System (ADS)

Dou, Kun; Yang, Zhenguo; Liu, Qing; Huang, Yunhua; Dong, Hongbiao

2017-07-01

A cellular automaton-finite element coupling model for high-carbon continuously cast bloom of GCr15 steel is established to simulate the solidification structure and to investigate the influence of different secondary cooling modes on characteristic parameters such as equiaxed crystal ratio, grain size and secondary dendrite arm spacing, in which the effect of phase transformation and electromagnetic stirring is taken into consideration. On this basis, evolution of carbon macro-segregation for GCr15 steel bloom is researched correspondingly via industrial tests. Based on above analysis, the relationship among secondary cooling modes, characteristic parameters for solidification structure as well as carbon macro-segregation is illustrated to obtain optimum secondary cooling strategy and alleviate carbon macro-segregation degree for GCr15 steel bloom in continuous casting process. The evaluating method for element macro-segregation is applicable in various steel types.

Shift Happens. How Halide Ion Defects Influence Photoinduced Segregation in Mixed Halide Perovskites

DOE PAGES

Yoon, Seog Joon; Kuno, Masaru; Kamat, Prashant V.

2017-06-01

Minimizing photoinduced segregation in mixed halide lead perovskites is important for achieving stable photovoltaic performance. The shift in the absorption and the rate of formation of iodide- and bromide-rich regions following visible excitation of mixed halide lead perovskites is found to strongly depend on the halide ion concentration. Slower formation and recovery rates observed in halide-deficient films indicate the involvement of defect sites in influencing halide phase segregation. At higher halide concentrations (in stoichiometric excess), segregation effects become less prominent, as evidenced by faster recovery kinetics. These results suggest that light-induced compositional segregation can be minimized in mixed halide perovskitemore » films by using excess halide ions. In conclusion, the findings from this study further reflect the importance of halide ion post-treatment of perovskite films to improve their solar cell performance.« less

The effect of primary recoil spectrum on radiation induced segregation in nickel-silicon alloys

NASA Astrophysics Data System (ADS)

Averback, R. S.; Rehn, L. E.; Wagner, W.; Ehrhart, P.

1983-08-01

Segregation of silicon to the surface of Ni-12.7 at% Si alloys during 2.0-MeV He and 3.25-MeV Kr irradiations was measured using Rutherford backscattering spectrometry. For equal calculated defect production rates the Kr irradiation was < 3 % as efficient as the He irradiation for promoting segregation in the temperature range, 450 °C-580 °C. It was further observed that Kr preirradiation of specimens dramatically reduced segregation during subsequent He irradiation. A model for cascade annealing in Ni-Si alloys is presented which qualitatively explains the segregation results. The model assumes that small interstitial-atom-clusters form in individual cascades and that these clusters become trapped at silicon solute atoms. The vacancy thereby becomes the more mobile defect. The model should also have relevance for the observation that void swelling in nickel is suppressed by the addition of silicon solute.

Sexual Segregation in Juvenile New Zealand Sea Lion Foraging Ranges: Implications for Intraspecific Competition, Population Dynamics and Conservation

PubMed Central

Leung, Elaine S.; Chilvers, B. Louise; Nakagawa, Shinichi; Moore, Antoni B.; Robertson, Bruce C.

2012-01-01

Sexual segregation (sex differences in spatial organisation and resource use) is observed in a large range of taxa. Investigating causes for sexual segregation is vital for understanding population dynamics and has important conservation implications, as sex differences in foraging ecology may affect vulnerability to area-specific human activities. Although behavioural ecologists have proposed numerous hypotheses for this phenomenon, the underlying causes of sexual segregation are poorly understood. We examined the size-dimorphism and niche divergence hypotheses as potential explanations for sexual segregation in the New Zealand (NZ) sea lion (Phocarctos hookeri), a nationally critical, declining species impacted by trawl fisheries. We used satellite telemetry and linear mixed effects models to investigate sex differences in the foraging ranges of juvenile NZ sea lions. Male trip distances and durations were almost twice as long as female trips, with males foraging over the Auckland Island shelf and in further locations than females. Sex was the most important variable in trip distance, maximum distance travelled from study site, foraging cycle duration and percent time at sea whereas mass and age had small effects on these characteristics. Our findings support the predictions of the niche divergence hypothesis, which suggests that sexual segregation acts to decrease intraspecific resource competition. As a consequence of sexual segregation in foraging ranges, female foraging grounds had proportionally double the overlap with fisheries operations than males. This distribution exposes female juvenile NZ sea lions to a greater risk of resource competition and bycatch from fisheries than males, which can result in higher female mortality. Such sex-biased mortality could impact population dynamics, because female population decline can lead to decreased population fecundity. Thus, effective conservation and management strategies must take into account sex differences in foraging behaviour, as well as differential threat-risk to external impacts such as fisheries bycatch. PMID:23028978

Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration

NASA Astrophysics Data System (ADS)

Fishman, Yonatan I.; Arezzo, Joseph C.; Steinschneider, Mitchell

2004-09-01

Auditory stream segregation refers to the organization of sequential sounds into ``perceptual streams'' reflecting individual environmental sound sources. In the present study, sequences of alternating high and low tones, ``...ABAB...,'' similar to those used in psychoacoustic experiments on stream segregation, were presented to awake monkeys while neural activity was recorded in primary auditory cortex (A1). Tone frequency separation (ΔF), tone presentation rate (PR), and tone duration (TD) were systematically varied to examine whether neural responses correlate with effects of these variables on perceptual stream segregation. ``A'' tones were fixed at the best frequency of the recording site, while ``B'' tones were displaced in frequency from ``A'' tones by an amount=ΔF. As PR increased, ``B'' tone responses decreased in amplitude to a greater extent than ``A'' tone responses, yielding neural response patterns dominated by ``A'' tone responses occurring at half the alternation rate. Increasing TD facilitated the differential attenuation of ``B'' tone responses. These findings parallel psychoacoustic data and suggest a physiological model of stream segregation whereby increasing ΔF, PR, or TD enhances spatial differentiation of ``A'' tone and ``B'' tone responses along the tonotopic map in A1.

Microstructure of the Sn-Cu{sub 6}Sn{sub 5} fibrous eutectic and its modification by segregation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drevet, B.; Camel, D.; Favier, J.J.

The influence of segregation due to thermal convection on the microstructure of Sn-Cu{sub 6}Sn{sub 5} fibrous eutectic alloys is studied in a Bridgman type configuration. The eutectic microstructure is characterized by means of image analysis, X-ray diffraction and scanning and transmission electron microscopy. In the absence of segregation, the eutectic is regular and its growth controlled by that of the Cu{sub 6}Sn{sub 5} fibers. The effect of interphases on eutectic spacing, through orientation relationships between fibers and matrix, is also evidenced. The influence of segregation can be summed up by the following effects. At first, in agreement with the Jacksonmore » and Hunt model, it leads to a variation of the eutectic spacing which results from a variation of the fiber volume fraction. Then, the spacing is much greater than the one obtained in the absence of segregation, due to a different tin growth plane and non-optimized fiber/matrix orientation relationships. Finally, the absence of steady state leads to a large dispersion of the spacing associated with a microstructural disorder.« less

76 FR 38416 - Notice of Segregation of Public Lands in the States of Arizona, California, Colorado, Nevada, New...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-30

... protecting potential sites for future solar energy development. DATES: Effective Date: This segregation is... public lands that have been identified by the BLM as having the potential for solar energy generation...

Foreclosures and crime: a city-level analysis in Southern California of a dynamic process.

PubMed

Hipp, John R; Chamberlain, Alyssa W

2015-05-01

Although a growing body of research has examined and found a positive relationship between neighborhood crime and home foreclosures, some research suggests this relationship may not hold in all cities. This study uses city-level data to assess the relationship between foreclosures and crime by estimating longitudinal models with lags for monthly foreclosure and crime data in 128 cities from 1996 to 2011 in Southern California. We test whether these effects are stronger in cities with a combination of high economic inequality and high economic segregation; and whether they are stronger in cities with high racial/ethnic heterogeneity and high racial segregation. One month, and cumulative three month, six month, and 12-month lags of foreclosures are found to increase city level crime for all crimes except motor vehicle theft. The effect of foreclosures on these crime types is stronger in cities with simultaneously high levels of inequality but low levels of economic segregation. The effect of foreclosures on aggravated assault, robbery, and burglary is stronger in cities with simultaneously high levels of racial heterogeneity and low levels of racial segregation. On the other hand, foreclosures had a stronger effect on larceny and motor vehicle theft when they occurred in a city with simultaneously high levels of racial heterogeneity and high levels of racial segregation. There is evidence that the foreclosure crisis had large scale impacts on cities, leading to higher crime rates in cities hit harder by foreclosures. Nonetheless, the economic and racial characteristics of the city altered this effect. Copyright © 2014 Elsevier Inc. All rights reserved.

Hindrance Velocity Model for Phase Segregation in Suspensions of Poly-dispersed Randomly Oriented Spheroids

NASA Astrophysics Data System (ADS)

Faroughi, S. A.; Huber, C.

2015-12-01

Crystal settling and bubbles migration in magmas have significant effects on the physical and chemical evolution of magmas. The rate of phase segregation is controlled by the force balance that governs the migration of particles suspended in the melt. The relative velocity of a single particle or bubble in a quiescent infinite fluid (melt) is well characterized; however, the interplay between particles or bubbles in suspensions and emulsions and its effect on their settling/rising velocity remains poorly quantified. We propose a theoretical model for the hindered velocity of non-Brownian emulsions of nondeformable droplets, and suspensions of spherical solid particles in the creeping flow regime. The model is based on three sets of hydrodynamic corrections: two on the drag coefficient experienced by each particle to account for both return flow and Smoluchowski effects and a correction on the mixture rheology to account for nonlocal interactions between particles. The model is then extended for mono-disperse non-spherical solid particles that are randomly oriented. The non-spherical particles are idealized as spheroids and characterized by their aspect ratio. The poly-disperse nature of natural suspensions is then taken into consideration by introducing an effective volume fraction of particles for each class of mono-disperse particles sizes. Our model is tested against new and published experimental data over a wide range of particle volume fraction and viscosity ratios between the constituents of dispersions. We find an excellent agreement between our model and experiments. We also show two significant applications for our model: (1) We demonstrate that hindered settling can increase mineral residence time by up to an order of magnitude in convecting magma chambers. (2) We provide a model to correct for particle interactions in the conventional hydrometer test to estimate the particle size distribution in soils. Our model offers a greatly improved agreement with the results obtained with direct measurement methods such as laser diffraction.

Variation of mutational burden in healthy human tissues suggests non-random strand segregation and allows measuring somatic mutation rates.

PubMed

Werner, Benjamin; Sottoriva, Andrea

2018-06-01

The immortal strand hypothesis poses that stem cells could produce differentiated progeny while conserving the original template strand, thus avoiding accumulating somatic mutations. However, quantitating the extent of non-random DNA strand segregation in human stem cells remains difficult in vivo. Here we show that the change of the mean and variance of the mutational burden with age in healthy human tissues allows estimating strand segregation probabilities and somatic mutation rates. We analysed deep sequencing data from healthy human colon, small intestine, liver, skin and brain. We found highly effective non-random DNA strand segregation in all adult tissues (mean strand segregation probability: 0.98, standard error bounds (0.97,0.99)). In contrast, non-random strand segregation efficiency is reduced to 0.87 (0.78,0.88) in neural tissue during early development, suggesting stem cell pool expansions due to symmetric self-renewal. Healthy somatic mutation rates differed across tissue types, ranging from 3.5 × 10-9/bp/division in small intestine to 1.6 × 10-7/bp/division in skin.

Wider-community Segregation and the Effect of Neighbourhood Ethnic Diversity on Social Capital: An Investigation into Intra-Neighbourhood Trust in Great Britain and London

PubMed Central

Laurence, James

2016-01-01

Extensive research has demonstrated that neighbourhood ethnic diversity is negatively associated with intra-neighbourhood social capital. This study explores the role of segregation and integration in this relationship. To do so it applies three-level hierarchical linear models to two sets of data from across Great Britain and within London, and examines how segregation across the wider-community in which a neighbourhood is nested impacts trust amongst neighbours. This study replicates the increasingly ubiquitous finding that neighbourhood diversity is negatively associated with neighbour-trust. However, we demonstrate that this relationship is highly dependent on the level of segregation across the wider-community in which a neighbourhood is nested. Increasing neighbourhood diversity only negatively impacts neighbour-trust when nested in more segregated wider-communities. Individuals living in diverse neighbourhoods nested within integrated wider-communities experience no trust-penalty. These findings show that segregation plays a critical role in the neighbourhood diversity/trust relationship, and that its absence from the literature biases our understanding of how ethnic diversity affects social cohesion. PMID:28989199

Wider-community Segregation and the Effect of Neighbourhood Ethnic Diversity on Social Capital: An Investigation into Intra-Neighbourhood Trust in Great Britain and London.

PubMed

Laurence, James

2017-10-01

Extensive research has demonstrated that neighbourhood ethnic diversity is negatively associated with intra-neighbourhood social capital. This study explores the role of segregation and integration in this relationship. To do so it applies three-level hierarchical linear models to two sets of data from across Great Britain and within London, and examines how segregation across the wider-community in which a neighbourhood is nested impacts trust amongst neighbours. This study replicates the increasingly ubiquitous finding that neighbourhood diversity is negatively associated with neighbour-trust. However, we demonstrate that this relationship is highly dependent on the level of segregation across the wider-community in which a neighbourhood is nested. Increasing neighbourhood diversity only negatively impacts neighbour-trust when nested in more segregated wider-communities. Individuals living in diverse neighbourhoods nested within integrated wider-communities experience no trust-penalty. These findings show that segregation plays a critical role in the neighbourhood diversity/trust relationship, and that its absence from the literature biases our understanding of how ethnic diversity affects social cohesion.

Terrestrial magma ocean and core segregation in the earth

NASA Technical Reports Server (NTRS)

Ohtani, Eiji; Yurimoto, Naoyoshi

1992-01-01

According to the recent theories of formation of the earth, the outer layer of the proto-earth was molten and the terrestrial magma ocean was formed when its radius exceeded 3000 km. Core formation should have started in this magma ocean stage, since segregation of metallic iron occurs effectively by melting of the proto-earth. Therefore, interactions between magma, mantle minerals, and metallic iron in the magma ocean stage controlled the geochemistry of the mantle and core. We have studied the partitioning behaviors of elements into the silicate melt, high pressure minerals, and metallic iron under the deep upper mantle and lower mantle conditions. We employed the multi-anvil apparatus for preparing the equilibrating samples in the ranges from 16 to 27 GPa and 1700-2400 C. Both the electron probe microanalyzer (EPMA) and the Secondary Ion Mass spectrometer (SIMS) were used for analyzing the run products. We obtained the partition coefficients of various trace elements between majorite, Mg-perovskite, and liquid, and magnesiowustite, Mg-perovskite, and metallic iron. The examples of the partition coefficients of some key elements are summarized in figures, together with the previous data. We may be able to assess the origin of the mantle abundances of the elements such as transition metals by using the partitioning data obtained above. The mantle abundances of some transition metals expected by the core-mantle equilibrium under the lower mantle conditions cannot explain the observed abundance of some elements such as Mn and Ge in the mantle. Estimations of the densities of the ultrabasic magma Mg-perovskite at high pressure suggest existence of a density crossover in the deep lower mantle; flotation of Mg-perovskite occurs in the deep magma ocean under the lower mantle conditions. The observed depletion of some transition metals such as V, Cr, Mn, Fe, Co, and Ni in the mantle may be explained by the two stage process, the core-mantle equilibrium under the lower mantle conditions in the first stage, and subsequent downwards separation of the ultrabasic liquid (and magnesiowustite) and flotation of Mg-perovskite in the lower mantle.

Social Contacts and Race/Ethnic Job Matching

ERIC Educational Resources Information Center

Stainback, Kevin

2008-01-01

Scholarly literature and the media often tout "networking" as an effective route for obtaining quality employment. Some scholars, however, have cautioned that racially segregated social networks may produce racially segregated workgroups and differential opportunity structures over time. Drawing from theoretical perspectives pertaining to social…

Helium segregation on surfaces of plasma-exposed tungsten

DOE PAGES

Maroudas, Dimitrios; Blondel, Sophie; Hu, Lin; ...

2016-01-21

Here we report a hierarchical multi-scale modeling study of implanted helium segregation on surfaces of tungsten, considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations based on a reliable interatomic interaction potential, including molecular-statics simulations to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile He-n (1 <= n <= 7) clusters in the near-surface region are attracted to the surface due to an elastic interaction force that provides themore » thermodynamic driving force for surface segregation. Elastic interaction force induces drift fluxes of these mobile Hen clusters, which increase substantially as the migrating clusters approach the surface, facilitating helium segregation on the surface. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, in the near-surface region at rates much higher than in the bulk material. Moreover, these near-surface cluster dynamics have significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure. We integrate the findings of such atomic-scale simulations into a properly parameterized and validated spatially dependent, continuum-scale reaction-diffusion cluster dynamics model, capable of predicting implanted helium evolution, surface segregation, and its near-surface effects in tungsten. This cluster-dynamics model sets the stage for development of fully atomistically informed coarse-grained models for computationally efficient simulation predictions of helium surface segregation, as well as helium retention and surface morphological evolution, toward optimal design of plasma facing components.« less

Determination of oligomeric chain length distributions at surfaces using ToF-SIMS: segregation effects and polymer properties

NASA Astrophysics Data System (ADS)

Gardella, Joseph A.; Mahoney, Christine M.

2004-06-01

While many XPS and SIMS studies of polymers have detected and quantified segregation of low surface energy blocks or components in copolymers and polymer blends [D. Briggs, in: D.R. Clarke, S. Suresh, I.M. Ward (Eds.), Surface Analysis of Polymers by XPS and Static SIMS, Cambridge University Press, Cambridge, 1998 (Chapter 5).], this paper reports ToF-SIMS studies of direct measurement of the segment length distribution at the surface of siloxane copolymers. These data allow insight into the segregation of particular portions of the oligomeric distribution; specifically, in this study, longer PDMS oligomers segregated at the expense of shorter PDMS chains. We have reported XPS analysis of competitive segregation effects for short PDMS chains [Macromolecules 35 (13) (2002) 5256]. In this study, a series of poly(ureaurethane)-poly(dimethylsiloxane) (PUU-PDMS) copolymers have been synthesized containing varying ratios of G-3 and G-9 (G- X describes the average segment length of the PDMS added), while maintaining a constant overall siloxane weight percentage (10, 30, and 60%). These copolymers were utilized as model systems to study the preferential segregation of certain siloxane segment lengths to the surface over others. ToF-SIMS analysis of PUU-PDMS copolymers has yielded high-mass range copolymer fragmentation patterns containing intact PDMS segments. For the first time, this information is utilized to determine PDMS segment length distributions at the copolymer surface as compared to the bulk. The results show that longer siloxane segment lengths are preferentially segregating to the surface over shorter chain lengths. These results also show the importance of ToF-SIMS and mass spectrometry in the development of new materials containing low molecular weight amino-propyl-terminated siloxanes.

Helium segregation on surfaces of plasma-exposed tungsten

NASA Astrophysics Data System (ADS)

Maroudas, Dimitrios; Blondel, Sophie; Hu, Lin; Hammond, Karl D.; Wirth, Brian D.

2016-02-01

We report a hierarchical multi-scale modeling study of implanted helium segregation on surfaces of tungsten, considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations based on a reliable interatomic interaction potential, including molecular-statics simulations to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile He n (1  ⩽  n  ⩽  7) clusters in the near-surface region are attracted to the surface due to an elastic interaction force that provides the thermodynamic driving force for surface segregation. This elastic interaction force induces drift fluxes of these mobile He n clusters, which increase substantially as the migrating clusters approach the surface, facilitating helium segregation on the surface. Moreover, the clusters’ drift toward the surface enables cluster reactions, most importantly trap mutation, in the near-surface region at rates much higher than in the bulk material. These near-surface cluster dynamics have significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure. We integrate the findings of such atomic-scale simulations into a properly parameterized and validated spatially dependent, continuum-scale reaction-diffusion cluster dynamics model, capable of predicting implanted helium evolution, surface segregation, and its near-surface effects in tungsten. This cluster-dynamics model sets the stage for development of fully atomistically informed coarse-grained models for computationally efficient simulation predictions of helium surface segregation, as well as helium retention and surface morphological evolution, toward optimal design of plasma facing components.

Metal/Silicate Partitioning at High Pressures and Temperatures

NASA Technical Reports Server (NTRS)

Shofner, G.; Campbell, A.; Danielson, L.; Righter, K.; Rahman, Z.

2010-01-01

The behavior of siderophile elements during metal-silicate segregation, and their resulting distributions provide insight into core formation processes. Determination of partition coefficients allows the calculation of element distributions that can be compared to established values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Moderately siderophile elements, including W, are particularly useful in constraining core formation conditions because they are sensitive to variations in T, P, oxygen fugacity (fO2), and silicate composition. To constrain the effect of pressure on W metal/silicate partitioning, we performed experiments at high pressures and temperatures using a multi anvil press (MAP) at NASA Johnson Space Center and laser-heated diamond anvil cells (LHDAC) at the University of Maryland. Starting materials consisted of natural peridotite mixed with Fe and W metals. Pressure conditions in the MAP experiments ranged from 10 to 16 GPa at 2400 K. Pressures in the LHDAC experiments ranged from 26 to 58 GPa, and peak temperatures ranged up to 5000 K. LHDAC experimental run products were sectioned by focused ion beam (FIB) at NASA JSC. Run products were analyzed by electron microprobe using wavelength dispersive spectroscopy. Liquid metal/liquid silicate partition coefficients for W were calculated from element abundances determined by microprobe analyses, and corrected to a common fO2 condition of IW-2 assuming +4 valence for W. Within analytical uncertainties, W partitioning shows a flat trend with increasing pressure from 10 to 16 GPa. At higher pressures, W becomes more siderophile, with an increase in partition coefficient of approximately 0.5 log units.

MRI Measurements and Granular Dynamics Simulation of Segregation of Granular Mixture

NASA Technical Reports Server (NTRS)

Nakagawa, M.; Moss, Jamie L.; Altobelli, Stephen A.

1999-01-01

A counter intuitive axial segregation phenomenon in a rotating horizontal cylinder has recently captured attention of many researchers in different disciplines. There is a growing consensus that the interplay between the particle dynamics and the evolution of the internal structure during the segregation process must be carefully investigated. Magnetic resonance imaging (MRI) has been used to non-invasively obtain much needed dynamic/static information such as velocity and concentration profiles, and it has proven to be capable of depicting the evolution of segregation processes. Segregation in a rotating cylinder involves two processes: the first is to transport small particles in the radial direction to form a radial core, and the second is to transform the radial core into axially segregated bands. Percolation and/or "stopping" have been proposed as mechanisms for the radial segregation. As to mechanisms for axial band formation, much less is known. The difference in the dynamic angle of repose has been proposed to segregate different components in the axial direction. Recently, Hill and Kakalios have reported that particles mix or demix depending upon the competition between diffusion and preferential drift whose order can be determined by the dynamic angle of repose through the adjustment of the rotation rate. We claim that the dynamic angle of repose could be one of the causes, however, it fails to offer reasonable explanations for certain aspects of the axial migration. For example, we always observe that the radial segregation precedes the axial segregation and small particles migrate in the radial direction to form an axially extended radial core. It then transforms into axially segregated bands. By definition, the effects of the dynamic angle of repose are restricted near the free surface where the flowing layer is present. However, during the process of transforming from the radially segregated core to axially segregated bands, small particles located in the deep core region, which is untouched by the flowing layer, also completely disappear. Usually, the dynamics angle of repose are uniquely defined for individual species to characterize particle properties, and the dynamic angle of repose thus defined provides little information for the dynamic angle of repose of the mixture since the concentration ratio and the internal packing structure do not remain the same during the segregation processes. Under microgravity environment, the dynamics angle of repose argument does not hold since there is simply no flowing layer to influence/determine the preferred directions of segregation. We have thus designed an experiment so that the effects of the dynamic angle of repose can be minimized by filling the cylinder almost completely full. Small particles still formed a radial core and also migrated to form axial bands. As ground based experiments we have designed and conducted both 2D and 3D segregation experiments. The 2D experiments are performed using a thin cylinder (the gap between two end caps is about 5 mm) filled with different combinations of particles. The 3D experiments are conducted with a long cylinder of its length and diameter of 27cm and 7cm, respectively. Results of 2D experiments indicate that different mechanisms govern particle motion in regions near and far from the axis of rotation. Results of 3D experiments indicate that a series of collapses of microstructures of particle packing (micro-collapses) may be responsible for the creation of voids for small particles to migrate through in the axial direction. We have successfully eliminated the dynamic angle of repose as a cause for segregation, however, by almost completely filling the cylinder with the particles, we have lost an opportunity to investigate a possibility of particle "mobility" being a cause for segregation which requires a flowing surface but not the difference in the angle of repose. This is currently being investigated.

Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

NASA Astrophysics Data System (ADS)

Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

1994-12-01

This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content, and is related to the classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is described by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

1994-01-01

This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content, and is related to the classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is described by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

Effects of Hydrogen Annealing, Sulfur Segregation and Diffusion on the Cyclic Oxidation Resistance of Superalloys: a Review

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

1994-01-01

This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content and related to classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is governed by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

Misoriented grain boundaries vicinal to the ? twin in Nickel part II: thermodynamics of hydrogen segregation

NASA Astrophysics Data System (ADS)

O'Brien, Christopher J.; Foiles, Stephen M.

2016-05-01

Grain boundary engineered materials are of immense interest for their resistance to hydrogen embrittlement. This work builds on the work undertaken in Part I on the thermodynamic stability and structure of misoriented grain boundaries vicinal to the ?? (coherent-twin) boundary to examine hydrogen segregation to those boundaries. The segregation of hydrogen reflects the asymmetry of the boundary structure with the sense of rotation of the grains about the coherent-twin boundary, and the temperature-dependent structural transition present in one sense of misorientation. This work also finds that the presence of hydrogen affects a change in structure of the boundaries with increasing concentration. The structural change effects only one sense of misorientation and results in the reduction in length of the emitted stacking faults. Moreover, the structural change results in the generation of occupied sites populated by more strongly bound hydrogen. The improved understanding of misoriented twin grain boundary structure and the effect on hydrogen segregation resulting from this work is relevant to higher length-scale models. To that end, we examine commonly used metrics such as free volume and atomic stress at the boundary. Free volume is found not to be useful as a surrogate for predicting the degree of hydrogen segregation, whereas the volumetric virial stress reliably predicts the locations of hydrogen segregation and exclusion at concentrations below saturation or the point where structural changes are induced by increasing hydrogen concentration.

Historical Examination of the Segregated School Experience

ERIC Educational Resources Information Center

Pellegrino, Anthony M.; Mann, Linda J.; Russell, William B., III

2013-01-01

Effective history teaching includes ample opportunities for students to develop historical thinking skills and habits of mind which encourage them to learn content beyond simple acquisition of facts. Covering the profound topic of segregation by employing multiple perspectives and encouraging investigation beyond the traditional narrative provides…

Radiation-induced segregation at grain boundaries in AL-6XN stainless steels irradiated by hydrogen ions

NASA Astrophysics Data System (ADS)

Long, Yunxiang; Zheng, Zhongcheng; Guo, Liping; Zhang, Weiping; Shen, Zhenyu; Tang, Rui

2018-04-01

The effect of high concentration of hydrogen on the segregation of radiation-induced segregation (RIS) in AL-6XN stainless steels has been investigated by transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy. Specimens were irradiated with 100 keV H2+ ions from 1 dpa to 5 dpa at 380 °C to investigated the dose dependence of grain boundary RIS. A specimen was irradiated to 5 dpa at 290 °C to study the effect of irradiation temperature. The trends of Cr depletion and Ni enrichment with irradiation dose is similar to that of other austenitic steels reported in the literatures, but the higher concentration of hydrogen made the RIS profile wider. An abnormal phenomenon that the degree of RIS increased with decreasing irradiation temperature was found, indicating that with the retention of hydrogen in the steels, temperature dependence of RIS is dominated by the quantity of retained hydrogen, rather than by thermal segregation processes.

Rapid visual perception of interracial crowds: Racial category learning from emotional segregation.

PubMed

Lamer, Sarah Ariel; Sweeny, Timothy D; Dyer, Michael Louis; Weisbuch, Max

2018-05-01

Drawing from research on social identity and ensemble coding, we theorize that crowd perception provides a powerful mechanism for social category learning. Crowds include allegiances that may be distinguished by visual cues to shared behavior and mental states, providing perceivers with direct information about social groups and thus a basis for learning social categories. Here, emotion expressions signaled group membership: to the extent that a crowd exhibited emotional segregation (i.e., was segregated into emotional subgroups), a visible characteristic (race) that incidentally distinguished emotional subgroups was expected to support categorical distinctions. Participants were randomly assigned to view interracial crowds in which emotion differences between (black vs. white) subgroups were either small (control condition) or large (emotional segregation condition). On each trial, participants saw crowds of 12 faces (6 black, 6 white) for roughly 300 ms and were asked to estimate the average emotion of the entire crowd. After all trials, participants completed a racial categorization task and self-report measure of race essentialism. As predicted, participants exposed to emotional segregation (vs. control) exhibited stronger racial category boundaries and stronger race essentialism. Furthermore, such effects accrued via ensemble coding, a visual mechanism that summarizes perceptual information: emotional segregation strengthened participants' racial category boundaries to the extent that segregation limited participants' abilities to integrate emotion across racial subgroups. Together with evidence that people observe emotional segregation in natural environments, these findings suggest that crowd perception mechanisms support racial category boundaries and race essentialism. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

The effects of composition and temperature on chalcophile and lithophile element partitioning into magmatic sulphides

NASA Astrophysics Data System (ADS)

Kiseeva, Ekaterina S.; Wood, Bernard J.

2015-08-01

We develop a comprehensive model to describe trace and minor element partitioning between sulphide liquids and anhydrous silicate liquids of approximately basaltic composition. We are able thereby to account completely for the effects of temperature and sulphide composition on the partitioning of Ag, Cd, Co, Cr, Cu, Ga, Ge, In, Mn, Ni, Pb, Sb, Ti, Tl, V and Zn. The model was developed from partitioning experiments performed in a piston-cylinder apparatus at 1.5 GPa and 1300 to 1700 °C with sulphide compositions covering the quaternary FeSsbnd NiSsbnd CuS0.5sbnd FeO. Partitioning of most elements is a strong function of the oxygen (or FeO) content of the sulphide. This increases linearly with the FeO content of the silicate melt and decreases with Ni content of the sulphide. As expected, lithophile elements partition more strongly into sulphide as its oxygen content increases, while chalcophile elements enter sulphide less readily with increasing oxygen. We parameterised the effects by using the ε-model of non-ideal interactions in metallic liquids. The resulting equation for partition coefficient of an element M between sulphide and silicate liquids can be expressed as We used our model to calculate the amount of sulphide liquid precipitated along the liquid line of descent of MORB melts and find that 70% of silicate crystallisation is accompanied by ∼0.23% of sulphide precipitation. The latter is sufficient to control the melt concentrations of chalcophile elements such as Cu, Ag and Pb. Our partition coefficients and observed chalcophile element concentrations in MORB glasses were used to estimate sulphur solubility in MORB liquids. We obtained between ∼800 ppm (for primitive MORB) and ∼2000 ppm (for evolved MORB), values in reasonable agreement with experimentally-derived models. The experimental data also enable us to reconsider Ce/Pb and Nd/Pb ratios in MORB. We find that constant Ce/Pb and Nd/Pb ratios of 25 and 20, respectively, can be achieved during fractional crystallisation of magmas generated by 10% melting of depleted mantle provided the latter contains >100 ppm S and about 650 ppm Ce, 550 ppm Nd and 27.5 ppb Pb. Finally, we investigated the hypothesis that the pattern of chalcophile element abundances in the mantle was established by segregation of a late sulphide matte. Taking the elements Cu, Ag, Pb and Zn as examples we find that the Pb/Zn and Cu/Ag ratios of the mantle can, in principle, be explained by segregation of ∼0.4% sulphide matte to the core.

HIV prevention interventions to reduce sexual risk for African Americans: the influence of community-level stigma and psychological processes.

PubMed

Reid, Allecia E; Dovidio, John F; Ballester, Estrellita; Johnson, Blair T

2014-02-01

Interventions to improve public health may benefit from consideration of how environmental contexts can facilitate or hinder their success. We examined the extent to which efficacy of interventions to improve African Americans' condom use practices was moderated by two indicators of structural stigma-Whites' attitudes toward African Americans and residential segregation in the communities where interventions occurred. A previously published meta-analytic database was re-analyzed to examine the interplay of community-level stigma with the psychological processes implied by intervention content in influencing intervention efficacy. All studies were conducted in the United States and included samples that were at least 50% African American. Whites' attitudes were drawn from the American National Election Studies, which collects data from nationally representative samples. Residential segregation was drawn from published reports. Results showed independent effects of Whites' attitudes and residential segregation on condom use effect sizes. Interventions were most successful when Whites' attitudes were more positive or when residential segregation was low. These two structural factors interacted: Interventions improved condom use only when communities had both relatively positive attitudes toward African Americans and lower levels of segregation. The effect of Whites' attitudes was more pronounced at longer follow-up intervals and for younger samples and those samples with more African Americans. Tailoring content to participants' values and needs, which may reduce African Americans' mistrust of intervention providers, buffered against the negative influence of Whites' attitudes on condom use. The structural factors uniquely accounted for variance in condom use effect sizes over and above intervention-level features and community-level education and poverty. Results highlight the interplay of social identity and environment in perpetuating intergroup disparities. Potential mechanisms for these effects are discussed along with public health implications. Copyright © 2013 Elsevier Ltd. All rights reserved.

HIV Prevention Interventions to Reduce Sexual Risk for African Americans: The Influence of Community-Level Stigma and Psychological Processes

PubMed Central

Reid, Allecia E.; Dovidio, John F.; Ballester, Estrellita; Johnson, Blair T.

2013-01-01

Interventions to improve public health may benefit from consideration of how environmental contexts can facilitate or hinder their success. We examined the extent to which efficacy of interventions to improve African Americans’ condom use practices was moderated by two indicators of structural stigma—Whites’ attitudes toward African Americans and residential segregation in the communities where interventions occurred. A previously published meta-analytic database was re-analyzed to examine the interplay of community-level stigma with the psychological processes implied by intervention content in influencing intervention efficacy. All studies were conducted in the United States and included samples that were at least 50% African American. Whites’ attitudes were drawn from the American National Election Studies, which collects data from nationally representative samples. Residential segregation was drawn from published reports. Results showed independent effects of Whites’ attitudes and residential segregation on condom use effect sizes. Interventions were most successful when Whites’ attitudes were more positive or when residential segregation was low. These two structural factors interacted: Interventions improved condom use only when communities had both relatively positive attitudes toward African Americans and lower levels of segregation. The effect of Whites’ attitudes was more pronounced at longer follow-up intervals and for younger samples and those samples with more African Americans. Tailoring content to participants’ values and needs, which may reduce African Americans’ mistrust of intervention providers, buffered against the negative influence of Whites’ attitudes on condom use. The structural factors uniquely accounted for variance in condom use effect sizes over and above intervention-level features and community-level education and poverty. Results highlight the interplay of social identity and environment in perpetuating intergroup disparities. Potential mechanisms for these effects are discussed along with public health implications. PMID:24507916

High Field fMRI Reveals Thalamocortical Integration of Segregated Cognitive and Emotional Processing in Mediodorsal and Intralaminar Thalamic Nuclei

PubMed Central

Metzger, C. D.; Eckert, U.; Steiner, J.; Sartorius, A.; Buchmann, J. E.; Stadler, J.; Tempelmann, C.; Speck, O.; Bogerts, B.; Abler, B.; Walter, M.

2010-01-01

Thalamocortical loops, connecting functionally segregated, higher order cortical regions, and basal ganglia, have been proposed not only for well described motor and sensory regions, but also for limbic and prefrontal areas relevant for affective and cognitive processes. These functions are, however, more specific to humans, rendering most invasive neuroanatomical approaches impossible and interspecies translations difficult. In contrast, non-invasive imaging of functional neuroanatomy using fMRI allows for the development of elaborate task paradigms capable of testing the specific functionalities proposed for these circuits. Until recently, spatial resolution largely limited the anatomical definition of functional clusters at the level of distinct thalamic nuclei. Since their anatomical distinction seems crucial not only for the segregation of cognitive and limbic loops but also for the detection of their functional interaction during cognitive–emotional integration, we applied high resolution fMRI on 7 Tesla. Using an event-related design, we could isolate thalamic effects for preceding attention as well as experience of erotic stimuli. We could demonstrate specific thalamic effects of general emotional arousal in mediodorsal nucleus and effects specific to preceding attention and expectancy in intralaminar centromedian/parafascicular complex. These thalamic effects were paralleled by specific coactivations in the head of caudate nucleus as well as segregated portions of rostral or caudal cingulate cortex and anterior insula supporting distinct thalamo–striato–cortical loops. In addition to predescribed effects of sexual arousal in hypothalamus and ventral striatum, high resolution fMRI could extent this network to paraventricular thalamus encompassing laterodorsal and parataenial nuclei. We could lend evidence to segregated subcortical loops which integrate cognitive and emotional aspects of basic human behavior such as sexual processing. PMID:21088699

Segregating Schools: The Foreseeable Consequences of Tuition Tax Credits.

ERIC Educational Resources Information Center

Yale Law Journal, 1979

1979-01-01

Argues that the effect of a proposed tuition tax credit is school segregation, creating serious constitutional objections under the due process clause. A voucher system would avoid these constitutional objections. Available from the Yale Law Journal, 401A Yale Station, New Haven, CT 06520. (Author/IRT)

Effects of temperature segregation on the volumetric and mechanistic properties of asphalt mixtures : research project capsule.

DOT National Transportation Integrated Search

2015-02-01

Material segregation in asphalt mixtures is a non-uniform distribution of coarse : and fine aggregates through its masses, i.e., concentration of coarse materials : in some area and fine materials in others. During construction, the coarse and : fine...

Segregation and preterm birth: The effects of neighborhood racial composition in North Carolina

EPA Science Inventory

Epidemiologic research suggests that racial segregation is associated with poor health among blacks in the United States (US). We used geocoded birth records and US census data to investigate whether neighborhood-level percent black is associated with preterm birth (PTB) for blac...

Impurity effects on the grain boundary cohesion in copper

NASA Astrophysics Data System (ADS)

Li, Yunguo; Korzhavyi, Pavel A.; Sandström, Rolf; Lilja, Christina

2017-12-01

Segregated impurities at grain boundaries can dramatically change the mechanical behavior of metals, while the mechanism is still obscure in some cases. Here, we suggest a unified approach to investigate segregation and its effects on the mechanical properties of polycrystalline alloys using the example of 3 s p impurities (Mg, Al, Si, P, or S) at a special type Σ 5 (310 )[001 ] tilt grain boundary in Cu. We show that for these impurities segregating to the grain boundary, the strain contribution to the work of grain boundary decohesion is small and that the chemical contribution correlates with the electronegativity difference between Cu and the impurity. The strain contribution to the work of dislocation emission is calculated to be negative, while the chemical contribution is calculated to be always positive. Both the strain and chemical contributions to the work of dislocation emission generally become weaker with the increasing electronegativity from Mg to S. By combining these contributions together, we find, in agreement with experimental observations, that a strong segregation of S can reduce the work of grain boundary separation below the work of dislocation emission, thus embrittling Cu, while such an embrittlement cannot be produced by a P segregation because it lowers the energy barrier for dislocation emission relatively more than for work separation.

Perceptual multistability in figure-ground segregation using motion stimuli.

PubMed

Gori, Simone; Giora, Enrico; Pedersini, Riccardo

2008-11-01

In a series of experiments using ambiguous stimuli, we investigate the effects of displaying ordered, discrete series of images on the dynamics of figure-ground segregation. For low frame presentation speeds, the series were perceived as a sequence of discontinuous, static images, while for high speeds they were perceived as continuous. We conclude that using stimuli varying continuously along one parameter results in stronger hysteresis and reduces spontaneous switching compared to matched static stimuli with discontinuous parameter changes. The additional evidence that the size of the hysteresis effects depended on trial duration is consistent with the stochastic nature of the dynamics governing figure-ground segregation. The results showed that for continuously changing stimuli, alternative figure-ground organizations are resolved via low-level, dynamical competition. A second series of experiments confirmed these results with an ambiguous stimulus based on Petter's effect.

Rapid mass segregation in small stellar clusters

NASA Astrophysics Data System (ADS)

Spera, Mario; Capuzzo-Dolcetta, Roberto

2017-12-01

In this paper we focus our attention on small-to-intermediate N-body systems that are, initially, distributed uniformly in space and dynamically `cool' (virial ratios Q=2T/|Ω| below ˜0.3). In this work, we study the mass segregation that emerges after the initial violent dynamical evolution. At this scope, we ran a set of high precision N-body simulations of isolated clusters by means of HiGPUs, our direct summation N-body code. After the collapse, the system shows a clear mass segregation. This (quick) mass segregation occurs in two phases: the first shows up in clumps originated by sub-fragmentation before the deep overall collapse; this segregation is partly erased during the deep collapse to re-emerge, abruptly, during the second phase, that follows the first bounce of the system. In this second stage, the proper clock to measure the rate of segregation is the dynamical time after virialization, which (for cold and cool systems) may be significantly different from the crossing time evaluated from initial conditions. This result is obtained for isolated clusters composed of stars of two different masses (in the ratio mh/ml=2), at varying their number ratio, and is confirmed also in presence of a massive central object (simulating a black hole of stellar size). Actually, in stellar systems starting their dynamical evolution from cool conditions, the fast mass segregation adds to the following, slow, secular segregation which is collisionally induced. The violent mass segregation is an effect persistent over the whole range of N (128 ≤ N ≤1,024) investigated, and is an interesting feature on the astronomical-observational side, too. The semi-steady state reached after virialization corresponds to a mass segregated distribution function rather than that of equipartition of kinetic energy per unit mass as it should result from violent relaxation.

Redefining Racial Residential Segregation and its Association With Physical Activity Among African Americans 50 years and Older: A Mixed Methods Approach

PubMed Central

Armstrong-Brown, Janelle; Eng, Eugenia; Hammond, Wizdom Powell; Zimmer, Catherine; Bowling, J. Michael

2016-01-01

Physical inactivity is one of the factors contributing to disproportionate disease rates among older African Americans. Previous literature indicates that older African Americans are more likely to live in racially segregated neighborhoods and that racial residential segregation is associated with limited opportunities for physical activity. A cross-sectional mixed methods study was conducted guided by the concept of therapeutic landscapes. Multilevel regression analyses demonstrated that racial residential segregation was associated with more minutes of physical activity and greater odds of meeting physical activity recommendations. Qualitative interviews revealed the following physical activity related themes: aging of the neighborhood, knowing your neighbors, feeling of safety, and neighborhood racial identity. Perceptions of social cohesion enhanced participants’ physical activity, offering a plausible explanation to the higher rates of physical activity found in this population. Understanding how social cohesion operates within racially segregated neighborhoods can help to inform the design of effective interventions for this population. PMID:24812201

Phase segregation in multiphase turbulent channel flow

NASA Astrophysics Data System (ADS)

Bianco, Federico; Soldati, Alfredo

2014-11-01

The phase segregation of a rapidly quenched mixture (namely spinodal decomposition) is numerically investigated. A phase field approach is considered. Direct numerical simulation of the coupled Navier-Stokes and Cahn-Hilliard equations is performed with spectral accuracy and focus has been put on domain growth scaling laws, in a wide range of regimes. The numerical method has been first validated against well known results of literature, then spinodal decomposition in a turbulent bounded flow (channel flow) has been considered. As for homogeneous isotropic case, turbulent fluctuations suppress the segregation process when surface tension at the interfaces is relatively low (namely low Weber number regimes). For these regimes, segregated domains size reaches a statistically steady state due to mixing and break-up phenomena. In contrast with homogenous and isotropic turbulence, the presence of mean shear, leads to a typical domain size that show a wall-distance dependence. Finally, preliminary results on the effects to the drag forces at the wall, due to phase segregation, have been discussed. Regione FVG, program PAR-FSC.

First-principles study of Au–Cu alloy surface changes induced by gas adsorption of CO, NO, or O{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhifallah, Marwa; Université de Gabes, Unité de recherche environnement, Catalyse et Analyse des Procédés, 6072 Gabes; Dhouib, Adnene

2016-07-14

The surface composition of bimetallics can be strongly altered by adsorbing molecules where the metal with the strongest interaction with the adsorbate segregates into the surface. To investigate the effect of reactive gas on the surface composition of Au–Cu alloy, we examined by means of density functional theory to study the segregation behavior of copper in gold matrices. The adsorption mechanisms of CO, NO, and O{sub 2} gas molecules on gold, copper, and gold-copper low index (111), (100), and (110) surfaces were analyzed from energetic and electronic points of view. Our results show a strong segregation of Cu toward themore » (110) surface in the presence of all adsorbed molecules. Interestingly, the Cu segregation toward the (111) and (100) surface could occur only in the presence of CO and at a lower extent in the presence of NO. The analysis of the electronic structure highlights the different binding characters of adsorbates inducing the Cu segregation.« less

The Association Between County-Level Injury Rates and Racial Segregation Revisited: A Multilevel Analysis

PubMed Central

Sauber-Schatz, Erin K.; Barbour, Kamil E.; Li, Wei

2009-01-01

Objectives. We investigated whether within-county racial segregation was associated with increased odds of violent injury beyond individual risk. Methods. In a cross-sectional study, data on 75 310 patients admitted with an injury to Pennsylvania hospitals from 1997 to 1999 were analyzed to determine the association between county-level racial segregation and violent injury. We used multilevel analysis to adjust for individual- and county-level factors. Principal components analysis allowed us to separate the effect of segregation from other county-level variables. Results. After adjustment, greater segregation was associated with increased odds of violent injury among Whites (odds ratio [OR] = 1.20; 95% confidence interval [CI] = 1.11, 1.30) and non-Whites (OR = 1.45; 95% CI = 1.28, 1.64). The association was stronger for non-Whites. Conclusions. Our results suggested that living in a county with high levels of racial segregation was associated with increased odds of violence not explained by an individual's own risk. These findings represent an important step in understanding the nature of observed links between race and violence. Future work should develop prevention strategies that simultaneously target community and individual risks. PMID:19150902

Evaluation of an education and training intervention to reduce health care waste in a tertiary hospital in Spain.

PubMed

Mosquera, Margarita; Andrés-Prado, Maria José; Rodríguez-Caravaca, Gil; Latasa, Pello; Mosquera, Marta E G

2014-08-01

In recent decades there has been a significant increase in waste generation. Training interventions in advanced health care waste management can improve the segregation of regulated medical waste and reduce volume and costs. We carried out a quasi-experimental intervention study with before and after training session analysis to compare waste segregation. Descriptive analysis of the segregated health care waste and an evaluation of the quality of segregation were done. A comparison of monthly average waste to assess the effectiveness of the educational intervention was performed. After the intervention, there was a significant reduction in the monthly average health care waste volume of 6.2%. Statistically significant differences in the infectious waste and genotoxic/pharmaceutical waste weight segregated before and after the intervention (P < .05) were found. Because of the health care waste weight reduction and the improvement of waste classification, a savings cost of €125,205 was achieved. The health care waste management training improves biomedical waste segregation at the hospital, reducing the health care waste volume and costs as an added value. Copyright © 2014 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.

Sexual segregation in North American elk: the role of density dependence

PubMed Central

Stewart, Kelley M; Walsh, Danielle R; Kie, John G; Dick, Brian L; Bowyer, R Terry

2015-01-01

We investigated how density-dependent processes and subsequent variation in nutritional condition of individuals influenced both timing and duration of sexual segregation and selection of resources. During 1999–2001, we experimentally created two population densities of North American elk (Cervus elaphus), a high-density population at 20 elk/km2, and a low-density population at 4 elk/km2 to test hypotheses relative to timing and duration of sexual segregation and variation in selection of resources. We used multi-response permutation procedures to investigate patterns of sexual segregation, and resource selection functions to document differences in selection of resources by individuals in high- and low-density populations during sexual segregation and aggregation. The duration of sexual segregation was 2 months longer in the high-density population and likely was influenced by individuals in poorer nutritional condition, which corresponded with later conception and parturition, than at low density. Males and females in the high-density population overlapped in selection of resources to a greater extent than in the low-density population, probably resulting from density-dependent effects of increased intraspecific competition and lower availability of resources. PMID:25691992

Numerical Analysis of the Effect of Particle Shape and Adhesion on the Segregation of Powder Mixtures

NASA Astrophysics Data System (ADS)

Alizadeh Behjani, Mohammadreza; Hassanpour, Ali; Ghadiri, Mojtaba; Bayly, Andrew

2017-06-01

Segregation of granules is an undesired phenomenon in which particles in a mixture separate from each other based on the differences in their physical and chemical properties. It is, therefore, crucial to control the homogeneity of the system by applying appropriate techniques. This requires a fundamental understanding of the underlying mechanisms. In this study, the effect of particle shape and cohesion has been analysed. As a model system prone to segregation, a ternary mixture of particles representing the common ingredients of home washing powders, namely, spray dried detergent powders, tetraacetylethylenediamine, and enzyme placebo (as the minor ingredient) during heap formation is modelled numerically by the Discrete Element Method (DEM) with an aim to investigate the effect of cohesion/adhesion of the minor components on segregation quality. Non-spherical particle shapes are created in DEM using the clumped-sphere method based on their X-ray tomograms. Experimentally, inter particle adhesion is generated by coating the minor ingredient (enzyme placebo) with Polyethylene Glycol 400 (PEG 400). The JKR theory is used to model the cohesion/adhesion of coated enzyme placebo particles in the simulation. Tests are carried out experimentally and simulated numerically by mixing the placebo particles (uncoated and coated) with the other ingredients and pouring them in a test box. The simulation and experimental results are compared qualitatively and quantitatively. It is found that coating the minor ingredient in the mixture reduces segregation significantly while the change in flowability of the system is negligible.

The role of the background: texture segregation and figure-ground segmentation.

PubMed

Caputo, G

1996-09-01

The effects of a texture surround composed of line elements on a stimulus within which a target line element segregates, were studied. Detection and discrimination of the target when it had the same orientation as the surround were impaired at short presentation time; on the other hand, no effect was present when they were reciprocally orthogonal. These results are interpreted as background completion in texture segregation; a texture made up of similar elements is represented as a continuous surface with contour and contrast of an embedded element inhibited. This interpretation is further confirmed with a simple line protruding from an annulus. Generally, the results are taken as evidence that local features are prevented from segmenting when they are parts of a global entity.

Pesticide Removal from Aqueous Solutions by Adding Salting Out Agents

PubMed Central

Moscoso, Fátima; Deive, Francisco J.; Esperança, José M. S. S.; Rodríguez, Ana

2013-01-01

Phase segregation in aqueous biphasic systems (ABS) composed of four hydrophilic ionic liquids (ILs): 1-butyl-3-methylimidazolium methylsulfate and 1-ethyl-3-methylimidazolium methylsulfate (CnC1im C1SO4, n = 2 and 4), tributylmethyl phosphonium methylsulfate (P4441 C1SO4) and methylpyridinium methylsulfate (C1Py C1SO4) and two high charge density potassium inorganic salts (K2CO3 and K2HPO4) were determined by the cloud point method at 298.15 K. The influence of the addition of the selected inorganic salts to aqueous mixtures of ILs was discussed in the light of the Hofmeister series and in terms of molar Gibbs free energy of hydration. The effect of the alkyl chain length of the cation on the methylsulfate-based ILs has been investigated. All the solubility data were satisfactorily correlated to several empirical equations. A pesticide (pentachlorophenol, PCP) extraction process based on the inorganic salt providing a greater salting out effect was tackled. The viability of the proposed process was analyzed in terms of partition coefficients and extraction efficiencies. PMID:24145747

The Role of Contextual Socioeconomic Circumstances and Neighborhood Poverty Segregation on Mortality in 4 European Cities.

PubMed

Marinacci, Chiara; Demaria, Moreno; Melis, Giulia; Borrell, Carme; Corman, Diana; Dell'Olmo, Marc Marí; Rodriguez, Maica; Costa, Giuseppe

2017-10-01

Several studies have recognized the health disadvantage of residents in socioeconomically deprived neighborhoods, independent of the influence of individual socioeconomic conditions. The effect of neighborhood socioeconomic deprivation on general mortality has appeared heterogeneous among the cities analyzed: the underlying mechanisms have been less empirically explored, and explanations for this heterogeneous health effect remain unclear. The present study aimed to: (1) analyze the distribution of socioeconomically disadvantaged persons in neighborhoods of 4 European cities-Turin, Barcelona, Stockholm and Helsinki-trying to measure segregation of residents according to their socioeconomic conditions. Two measuring approaches were used, respectively, through dissimilarity index and clustering estimated from Bayesian models. (2) Analyze the distribution of mortality in the above mentioned cities, trying to disentangle the independent effects of both neighborhood socioeconomic deprivation and neighborhood segregation of residents according to their socioeconomic conditions, using multilevel models. A significantly higher risk of death was observed among residents in more deprived neighborhoods in all 4 cities considered, slightly heterogeneous across them. Poverty segregation appeared to be slightly associated with increasing mortality in Turin and, among females and only according to dissimilarity, in Barcelona. Few studies have explored the health effects of social clustering, and results could inform urban policy design with regard to social mix.

[The Effect of Desegregation on the Minority Child.

ERIC Educational Resources Information Center

Siggers, Kathleen

Measurements of self worth show that children in segregated schools, both white and black, have unrealistically high aspirations. Mexican-Americans measure lower than other major ethnic groups in feelings of self worth. There is evidence from social investigations, however, that segregation produces feelings of "imposed inferiority" among minority…

Gender-Role Identity, Attitudes toward Marriage, and Gender-Segregated School Backgrounds.

ERIC Educational Resources Information Center

Katsurada, Emiko; Sugihara, Yoko

2002-01-01

Investigated the relationship between Japanese college students' gender role identity and attitudes toward marriage, exploring the effects of gender-segregated school backgrounds on gender role identity and attitudes toward marriage. Women without any coeducational school background had relatively strong masculinity and desired to marry at older…

Housing Segregation: Causes, Effects, Possible Cures.

ERIC Educational Resources Information Center

Orfield, Gary

Though Congress long ago declared housing discrimination illegal, there is very little enforcement of the law, and in 2000, the isolation of minority families remains high. The most recent federal and local studies of the housing market and of lending practices indicate continued and widespread discrimination. Segregated black communities extend…

Impact of ancestry categorisations on residential segregation measures using Swedish register data.

PubMed

Jarvis, Benjamin; Kawalerowicz, Juta; Valdez, Sarah

2017-07-01

Country-of-birth data contained in registers are often aggregated to create broad ancestry group categories. We examine how measures of residential segregation vary according to levels of aggregation. We use Swedish register data to calculate pairwise dissimilarity indices from 1990 to 2012 for ancestry groups defined at four nested levels of aggregation: (1) micro-groups containing 50 categories, (2) meso-groups containing 16 categories, (3) macro-groups containing six categories and (4) a broad Western/non-Western binary. We find variation in segregation levels between ancestry groups that is obscured by data aggregation. This study demonstrates that the practice of aggregating country-of-birth statistics in register data can hinder the ability to identify highly segregated groups and therefore design effective policy to remedy both intergroup and intergenerational inequalities.

3D analysis of macrosegregation in twin-roll cast AA3003 alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Šlapáková, Michaela, E-mail: slapakova@karlov.mff.

Twin-roll cast aluminium alloys have a high potential for industrial applications. However, one of the drawbacks of such materials is an inhomogeneous structure generated by macrosegregation, which appears under certain conditions in the center of sheets during solidification. Segregations in AA3003 alloy form as manganese, iron and silicon rich channels spread in the rolling direction. Their spatial distribution was successfully detected by X-ray computed tomography. Scanning electron microscopy was used for a detailed observation of microstructure, morphology and chemical analysis of the segregation. - Highlights: •Macrosegregations in twin-roll cast sheets stretch along the rolling direction. •X-ray computed tomography is anmore » effective tool for visualization of the segregation. •The segregations copy the shape of grain boundaries.« less

Improved radial segregation via the destabilizing vertical Bridgman configuration

NASA Astrophysics Data System (ADS)

Sonda, Paul; Yeckel, Andrew; Daoutidis, Prodromos; Derby, Jeffrey J.

2004-01-01

We employ a computational model to revisit the classic crystal growth experiments conducted by Kim et al. (J. Electrochem. Soc. 119 (1972) 1218) and Müller et al. (J. Crystal Growth 70 (1984) 78), which were among the first to clearly document the effects of flow transitions on segregation. Analysis of the growth of tellerium-doped indium antimonide within a destabilizing vertical Bridgman configuration reveals the existence of multiple states, each of which can be reached by feasible paths of process operation. Transient growth simulations conducted on the different solution branches reveal striking differences in hydrodynamic and segregation behavior. We show that crystals grown in the destabilizing configuration exhibit considerably better radial segregation than those grown in the stabilizing configuration, a result which challenges conventional wisdom and practice.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoon, Seog Joon; Kuno, Masaru; Kamat, Prashant V.

Minimizing photoinduced segregation in mixed halide lead perovskites is important for achieving stable photovoltaic performance. The shift in the absorption and the rate of formation of iodide- and bromide-rich regions following visible excitation of mixed halide lead perovskites is found to strongly depend on the halide ion concentration. Slower formation and recovery rates observed in halide-deficient films indicate the involvement of defect sites in influencing halide phase segregation. At higher halide concentrations (in stoichiometric excess), segregation effects become less prominent, as evidenced by faster recovery kinetics. These results suggest that light-induced compositional segregation can be minimized in mixed halide perovskitemore » films by using excess halide ions. In conclusion, the findings from this study further reflect the importance of halide ion post-treatment of perovskite films to improve their solar cell performance.« less

Cluster structure of anaerobic aggregates of an expanded granular sludge bed reactor.

PubMed

Gonzalez-Gil, G; Lens, P N; Van Aelst, A; Van As, H; Versprille, A I; Lettinga, G

2001-08-01

The metabolic properties and ultrastructure of mesophilic aggregates from a full-scale expanded granular sludge bed reactor treating brewery wastewater are described. The aggregates had a very high methanogenic activity on acetate (17.19 mmol of CH(4)/g of volatile suspended solids [VSS].day or 1.1 g of CH(4) chemical oxygen demand/g of VSS.day). Fluorescent in situ hybridization using 16S rRNA probes of crushed granules showed that 70 and 30% of the cells belonged to the archaebacterial and eubacterial domains, respectively. The spherical aggregates were black but contained numerous whitish spots on their surfaces. Cross-sectioning these aggregates revealed that the white spots appeared to be white clusters embedded in a black matrix. The white clusters were found to develop simultaneously with the increase in diameter. Energy-dispersed X-ray analysis and back-scattered electron microscopy showed that the whitish clusters contained mainly organic matter and no inorganic calcium precipitates. The white clusters had a higher density than the black matrix, as evidenced by the denser cell arrangement observed by high-magnification electron microscopy and the significantly higher effective diffusion coefficient determined by nuclear magnetic resonance imaging. High-magnification electron microscopy indicated a segregation of acetate-utilizing methanogens (Methanosaeta spp.) in the white clusters from syntrophic species and hydrogenotrophic methanogens (Methanobacterium-like and Methanospirillum-like organisms) in the black matrix. A number of physical and microbial ecology reasons for the observed structure are proposed, including the advantage of segregation for high-rate degradation of syntrophic substrates.

Cluster Structure of Anaerobic Aggregates of an Expanded Granular Sludge Bed Reactor

PubMed Central

Gonzalez-Gil, G.; Lens, P. N. L.; Van Aelst, A.; Van As, H.; Versprille, A. I.; Lettinga, G.

2001-01-01

The metabolic properties and ultrastructure of mesophilic aggregates from a full-scale expanded granular sludge bed reactor treating brewery wastewater are described. The aggregates had a very high methanogenic activity on acetate (17.19 mmol of CH4/g of volatile suspended solids [VSS]·day or 1.1 g of CH4 chemical oxygen demand/g of VSS·day). Fluorescent in situ hybridization using 16S rRNA probes of crushed granules showed that 70 and 30% of the cells belonged to the archaebacterial and eubacterial domains, respectively. The spherical aggregates were black but contained numerous whitish spots on their surfaces. Cross-sectioning these aggregates revealed that the white spots appeared to be white clusters embedded in a black matrix. The white clusters were found to develop simultaneously with the increase in diameter. Energy-dispersed X-ray analysis and back-scattered electron microscopy showed that the whitish clusters contained mainly organic matter and no inorganic calcium precipitates. The white clusters had a higher density than the black matrix, as evidenced by the denser cell arrangement observed by high-magnification electron microscopy and the significantly higher effective diffusion coefficient determined by nuclear magnetic resonance imaging. High-magnification electron microscopy indicated a segregation of acetate-utilizing methanogens (Methanosaeta spp.) in the white clusters from syntrophic species and hydrogenotrophic methanogens (Methanobacterium-like and Methanospirillum-like organisms) in the black matrix. A number of physical and microbial ecology reasons for the observed structure are proposed, including the advantage of segregation for high-rate degradation of syntrophic substrates. PMID:11472948

Misoriented grain boundaries vicinal to the (111) <11¯0> twin in nickel part II: Thermodynamics of hydrogen segregation

DOE PAGES

O’Brien, Christopher J.; Foiles, Stephen M.

2016-04-19

Grain boundary engineered materials are of immense interest for their resistance to hydrogen embrittlement. This work builds on the work undertaken in Part I on the thermodynamic stability and structure of misoriented grain boundaries vicinal to the Σ3 (111) <11¯0> (coherent-twin) boundary to examine hydrogen segregation to those boundaries. The segregation of hydrogen reflects the asymmetry of the boundary structure with the sense of rotation of the grains about the coherent-twin boundary, and the temperature-dependent structural transition present in one sense of misorientation. This work also finds that the presence of hydrogen affects a change in structure of the boundariesmore » with increasing concentration. The structural change effects only one sense of misorientation and results in the reduction in length of the emitted stacking faults. Moreover, the structural change results in the generation of occupied sites populated by more strongly bound hydrogen. The improved understanding of misoriented twin grain boundary structure and the effect on hydrogen segregation resulting from this work is relevant to higher length-scale models. To that end, we examine commonly used metrics such as free volume and atomic stress at the boundary. In conclusion, free volume is found not to be useful as a surrogate for predicting the degree of hydrogen segregation, whereas the volumetric virial stress reliably predicts the locations of hydrogen segregation and exclusion at concentrations below saturation or the point where structural changes are induced by increasing hydrogen concentration.« less

Hierarchical spatial segregation of two Mediterranean vole species: the role of patch-network structure and matrix composition.

PubMed

Pita, Ricardo; Lambin, Xavier; Mira, António; Beja, Pedro

2016-09-01

According to ecological theory, the coexistence of competitors in patchy environments may be facilitated by hierarchical spatial segregation along axes of environmental variation, but empirical evidence is limited. Cabrera and water voles show a metapopulation-like structure in Mediterranean farmland, where they are known to segregate along space, habitat, and time axes within habitat patches. Here, we assess whether segregation also occurs among and within landscapes, and how this is influenced by patch-network and matrix composition. We surveyed 75 landscapes, each covering 78 ha, where we mapped all habitat patches potentially suitable for Cabrera and water voles, and the area effectively occupied by each species (extent of occupancy). The relatively large water vole tended to be the sole occupant of landscapes with high habitat amount but relatively low patch density (i.e., with a few large patches), and with a predominantly agricultural matrix, whereas landscapes with high patch density (i.e., many small patches) and low agricultural cover, tended to be occupied exclusively by the small Cabrera vole. The two species tended to co-occur in landscapes with intermediate patch-network and matrix characteristics, though their extents of occurrence were negatively correlated after controlling for environmental effects. In combination with our previous studies on the Cabrera-water vole system, these findings illustrated empirically the occurrence of hierarchical spatial segregation, ranging from within-patches to among-landscapes. Overall, our study suggests that recognizing the hierarchical nature of spatial segregation patterns and their major environmental drivers should enhance our understanding of species coexistence in patchy environments.

Epistasis interaction of QTL effects as a genetic parameter influencing estimation of the genetic additive effect.

PubMed

Bocianowski, Jan

2013-03-01

Epistasis, an additive-by-additive interaction between quantitative trait loci, has been defined as a deviation from the sum of independent effects of individual genes. Epistasis between QTLs assayed in populations segregating for an entire genome has been found at a frequency close to that expected by chance alone. Recently, epistatic effects have been considered by many researchers as important for complex traits. In order to understand the genetic control of complex traits, it is necessary to clarify additive-by-additive interactions among genes. Herein we compare estimates of a parameter connected with the additive gene action calculated on the basis of two models: a model excluding epistasis and a model with additive-by-additive interaction effects. In this paper two data sets were analysed: 1) 150 barley doubled haploid lines derived from the Steptoe × Morex cross, and 2) 145 DH lines of barley obtained from the Harrington × TR306 cross. The results showed that in cases when the effect of epistasis was different from zero, the coefficient of determination was larger for the model with epistasis than for the one excluding epistasis. These results indicate that epistatic interaction plays an important role in controlling the expression of complex traits.

The immersion freezing behavior of size-segregated soot and kaolinite particles

NASA Astrophysics Data System (ADS)

Hartmann, S.; Augustin, S.; Clauss, T.; Niedermeier, D.; Raddatz, M.; Wex, H.; Shaw, R. A.; Stratmann, F.

2011-12-01

Heterogeneous ice nucleation plays a crucial role for ice formation in mixed-phase and cirrus clouds and has an important impact on precipitation formation, global radiation balances, and therefore Earth's climate (Cantrell and Heymsfield, 2005). Mineral dust and soot particles are found to be a major component of ice crystal residues (e.g., Pratt et al., 2009) so these substances are potential sources of atmospheric ice nuclei (IN). Experimental studies investigating the immersion freezing behavior of size-segregated soot and kaolinite particles conducted at the Leipzig Aerosol Cloud Interaction Simulator (LACIS) are presented. In our measurements only one aerosol particle is immersed in an air suspended water droplet which can trigger ice nucleation. The method facilitates very precise examinations with respect to temperature, ice nucleation time and ice nucleus size. Considering laboratory studies, the picture of the IN ability of soot particles is quite heterogeneous. Our studies show that submicron flame, spark soot particles and optionally coated with sulfuric acid to simulate chemically aging do not act as IN at temperatures higher than homogeneous freezing taking place. Therefore soot particles might not be an important source of IN for immersion freezing in the atmosphere. In contrast, kaolinite being representative for natural mineral dust with a well known composition and structure is found to be very active in forming ice for all freezing modes (e.g., Mason and Maybank, 1958). Analyzing the immersion freezing behavior of different sized kaolinite particles (300, 500 and 700 nm in diameter) the size effect was clearly observed, i.e. the ice fraction (number of frozen droplets per total number) scales with particle surface, i.e. the larger the ice nucleus surface the higher the ice fraction. The slope of the logarithm of the ice fraction as function of temperature is similar for all particle sizes investigated and fits very well with the results of Lüönd et al. (2010) and Murray et al. (2011). Heterogeneous ice nucleation rate coefficients are derived which can be used to describe the immersion freezing process size-segregated in cloud microphysical models.

Multitalker Speech Perception with Ideal Time-Frequency Segregation: Effects of Voice Characteristics and Number of Talkers

DTIC Science & Technology

2009-03-23

Multitalker speech perception with ideal time-frequency segregation: Effects of voice characteristics and number of talkers Douglas S. Brungarta Air...INTRODUCTION Speech perception in multitalker listening environments is limited by two very different types of masking. The first is energetic...06 MAR 2009 2. REPORT TYPE 3. DATES COVERED 00-00-2009 to 00-00-2009 4. TITLE AND SUBTITLE Multitalker speech perception with ideal time

First-principles study of the effect of phosphorus on nickel grain boundary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wenguan; Ren, Cuilan; Han, Han, E-mail: hanhan@sinap.ac.cn, E-mail: xuhongjie@sinap.ac.cn

2014-01-28

Based on first-principles quantum-mechanical calculations, the impurity-dopant effects of phosphorus on Σ5(012) symmetrical tilt grain boundary in nickel have been studied. The calculated binding energy suggests that phosphorus has a strong tendency to segregate to the grain boundary. Phosphorus forms strong and covalent-like bonding with nickel, which is beneficial to the grain boundary cohesion. However, a too high phosphorus content can result in a thin and fragile zone in the grain boundary, due to the repulsion between phosphorus atoms. As the concentration of phosphorus increases, the strength of the grain boundary increases first and then decreases. Obviously, there exists anmore » optimum concentration for phosphorus segregation, which is consistent with observed segregation behaviors of phosphorus in the grain boundary of nickel. This work is very helpful to understand the comprehensive effects of phosphorus.« less

A deficiency screen of the major autosomes identifies a gene (matrimony) that is haplo-insufficient for achiasmate segregation in Drosophila oocytes.

PubMed Central

Harris, David; Orme, Charisse; Kramer, Joseph; Namba, Luria; Champion, Mia; Palladino, Michael J; Natzle, Jeanette; Hawley, R Scott

2003-01-01

In Drosophila oocytes, euchromatic homolog-homolog associations are released at the end of pachytene, while heterochromatic pairings persist until metaphase I. A screen of 123 autosomal deficiencies for dominant effects on achiasmate chromosome segregation has identified a single gene that is haplo-insufficient for homologous achiasmate segregation and whose product may be required for the maintenance of such heterochromatic pairings. Of the deficiencies tested, only one exhibited a strong dominant effect on achiasmate segregation, inducing both X and fourth chromosome nondisjunction in FM7/X females. Five overlapping deficiencies showed a similar dominant effect on achiasmate chromosome disjunction and mapped the haplo-insufficient meiotic gene to a small interval within 66C7-12. A P-element insertion mutation in this interval exhibits a similar dominant effect on achiasmate segregation, inducing both high levels of X and fourth chromosome nondisjunction in FM7/X females and high levels of fourth chromosome nondisjunction in X/X females. The insertion site for this P element lies immediately upstream of CG18543, and germline expression of a UAS-CG18543 cDNA construct driven by nanos-GAL4 fully rescues the dominant meiotic defect. We conclude that CG18543 is the haplo-insufficient gene and have renamed this gene matrimony (mtrm). Cytological studies of prometaphase and metaphase I in mtrm hemizygotes demonstrate that achiasmate chromosomes are not properly positioned with respect to their homolog on the meiotic spindle. One possible, albeit speculative, interpretation of these data is that the presence of only a single copy of mtrm disrupts the function of whatever "glue" holds heterochromatically paired homologs together from the end of pachytene until metaphase I. PMID:14573476

Directional Solidification and Characterization of Hg(0.89) Mn(0.11)Te

NASA Technical Reports Server (NTRS)

Price, M. W.; Scripa, R. N.; Lehoczky. S. L.; Szofran, F. R.; Su, C.-H.

1998-01-01

Two boules of Hg(0.89)Mn(0.11)Te(MMT) were solidified using the vertical Bridgman-Stockbarger method. Translation rates of 0.09 and 0. 18 microns/s were used. The influence of growth rate on axial compositional homogeneity in the MMT boules was evaluated experimentally by conducting precision density measurements on radial slices taken from each boule. In addition, Plane Front Solidification theory and segregation coefficient (k) data for the Hg(1-x)Mn(x)Te system were used to fit theoretical composition profiles to the measured MMT axial composition profiles. The strong correlation between the measured and calculated MMT axial composition profiles indicates diffusion dominated axial solute redistribution in the boules under the applied growth conditions. The analysis of the MMT axial composition profiles by Plane Front Solidification theory allowed the calculation of the effective diffusion coefficient (D(eff) = 3.5 x l0(exp -5) sq cm/s). The k-values for the Hg(1-x)Mn(x)Te system and the D(sub eff) - value were then used to verify that both boules were solidified under conditions which did not exceed the Constitutional Supercooling Criteria under ideal conditions. Finally, a preliminary examination of the radial compositional variation in each MMT was made using Fourier Transform Infra-Red Spectroscopy (FTIR). The radial homogeneity in the MMT boules was found to be comparable for both translation rates.

Significant Enhancement in the Thermoelectric Properties of PEDOT:PSS Films through a Treatment with Organic Solutions of Inorganic Salts.

PubMed

Fan, Zeng; Du, Donghe; Yu, Zhimeng; Li, Pengcheng; Xia, Yijie; Ouyang, Jianyong

2016-09-07

Conducting polymers have promising thermoelectric application because they have many advantages including abundant elements, mechanical flexibility, and nontoxicity. The thermoelectric properties of conducting polymers strongly depend on their chemical structure and microstructure. Here, we report a novel and facile method to significantly enhance the thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) films through a treatment with organic solutions of inorganic salts. N,N-Dimethylformamide (DMF) and a common inorganic salt like zinc chloride (ZnCl2) are used as the solvent and solute of the solutions, respectively. The treatments can significantly increase both the Seebeck coefficient and electrical conductivity of the PSS films. The thermoelectric properties of the PSS films are sensitive to the experimental conditions, such as the salt concentration, treatment temperature, and the cation of the salts. After treatment at the optimal experimental conditions, the PSS films can exhibit a Seebeck coefficient of 26.1 μV/K and an electrical conductivity of over 1400 S/cm at room temperature. The corresponding power factor is 98.2 μW/(m·K(2)). The mechanism for the enhancement in the thermoelectric properties is attributed to the segregation of some PSSH chains from PSS and the conformation change of PEDOT chains as a result of the synergetic effects of inorganic salts and DMF.

Pressurized metallurgy for high performance special steels and alloys

NASA Astrophysics Data System (ADS)

Jiang, Z. H.; Zhu, H. C.; Li, H. B.; Li, Y.; Liu, F. B.

2016-07-01

The pressure is one of the basic parameters which greatly influences the metallurgical reaction process and solidification of steels and alloys. In this paper the history and present situation of research and application of pressurized metallurgy, especially pressurized metallurgy for special steels and alloys have been briefly reviewed. In the following part the physical chemistry of pressurized metallurgy is summarized. It is shown that pressurizing may change the conditions of chemical reaction in thermodynamics and kinetics due to the pressure effect on gas volume, solubility of gas and volatile element in metal melt, activity or activity coefficient of components, and change the physical and chemical properties of metal melt, heat transfer coefficient between mould and ingot, thus greatly influencing phase transformation during the solidification process and the solidification structure, such as increasing the solidification nucleation rate, reducing the critical nucleation radius, accelerating the solidification speed and significant macro/micro-structure refinement, and eliminating shrinkage, porosity and segregation and other casting defects. In the third part the research works of pressured metallurgy performed by the Northeastern University including establishment of pressurized induction melting (PIM) and pressurized electroslag remelting (PESR) equipments and development of high nitrogen steels under pressure are described in detail. Finally, it is considered in the paper that application of pressurized metallurgy in manufacture of high performance special steels and alloys is a relatively new research area, and its application prospects will be very broad and bright.

Microstructure Evolution and Rapid Solidification Behavior of Blended Nickel-Based Superalloy Powders Fabricated by Laser Powder Deposition

NASA Astrophysics Data System (ADS)

Tian, Y.; Gauvin, R.; Brochu, M.

2016-07-01

Laser powder deposition was performed on a substrate of Inconel 738 using blended powders of Mar M247 and Amdry DF3 with a ratio of 4:1 for repairing purposes. In the as-deposited condition, continuous secondary phases composed of γ-Ni3B eutectics and discrete (Cr, W)B borides were observed in inter-dendritic regions, and time-dependent nucleation simulation results confirmed that (Cr, W)B was the primary secondary phase formed during rapid solidification. Supersaturated solid solution of B was detected in the γ solid solution dendritic cores. The Kurz-Giovanola-Trivedi model was performed to predict the interfacial morphology and correlate the solidification front velocity (SFV) with dendrite tip radius. It was observed from high-resolution scanning electron microscopy that the dendrite tip radius of the upper region was in the range of 15 to 30 nm, which yielded a SFV of approx 30 cm/s. The continuous growth model for solute trapping behavior developed by Aziz and Kaplan was used to determine that the effective partition coefficient of B was approximately 0.025. Finally, the feasibility of the modeling results were rationalized with the Clyne-Kurz segregation simulation of B, where Clyne-Kurz prediction using a partition coefficient of 0.025 was in good agreement with the electron probe microanalysis results.

The Impact of Housing Segregation on Blacks

ERIC Educational Resources Information Center

Kain, John

1975-01-01

This testimony, before a public hearing of the New York City Commission on Human Rights in May 1974, is stated to focus primarily on the effects of housing market segregation and discrimination on the welfare of black Americans; findings of economic research indicate that Negro households at all income levels are impeded by housing market…

BIG CITY SCHOOL DESEGREGATION--TRENDS AND METHODS.

ERIC Educational Resources Information Center

DENTLER, ROBERT A.; ELSBERY, JAMES

THE CONCERNS OF THIS SPEECH ARE THE EXTENT OF SCHOOL SEGREGATION IN THE NATION'S 20 LARGEST CITIES, THE STEPS WHICH HAVE BEEN AND MIGHT BE TAKEN TO DESEGREGATE THEIR SCHOOL SYSTEMS, AND THE STRATEGIES NECESSARY TO EFFECTIVELY IMPLEMENT SCHOOL DESEGREGATION PLANS. THERE IS ALMOST TOTAL RESIDENTIAL SEGREGATION IN 13 OF THESE CITIES. SEVENTY PERCENT…

Shopping for Schools or Shopping for Peers: Public Schools and Catchment Area Segregation

ERIC Educational Resources Information Center

Rowe, Emma E.; Lubienski, Christopher

2017-01-01

Market theory positions the consumer as a rational choice actor, making informed schooling choices on the basis of "hard" evidence of relative school effectiveness. Yet there are concerns that parents simply choose schools based on socio-demographic characteristics, thus leading to greater social segregation and undercutting the…

"Jeesis Is Alive! He Is the King of Australia": Segregated Religious Instruction, Child Identity and Exclusion

ERIC Educational Resources Information Center

Byrne, Cathy Jane

2012-01-01

Religious categorisation occurs at enrolment in Australian state-run (public) primary schools, with children segregated into religious instruction classes during their first week. Lesson content has no government oversight and, in some schools, options are limited to Christianity. The effect of this categorisation on children's attitudes to…

School Integration Policies in Northern Cities.

ERIC Educational Resources Information Center

Glazer, Nathan

It is pointed out that there is little expert research on the effects of de facto segregation in schools in the North and the West. Too often an oversimplified casual relationship is drawn which explains the educational gap between white and Negro students in de facto segregated schools. Other factors considered in analyzing educational status…

Exploring DNA variant segregation types in pooled genome sequencing enables effective mapping of weeping trait in Malus

USDA-ARS?s Scientific Manuscript database

In recent years, next generation sequencing (NGS) based bulked segregant analysis (BSA) has become a powerful approach for allele discovery in non-model plant species. However, challenges remain, particular for out-crossing species with complex genomes. Here, the genetic control of a weeping bran...

Women, Work, and Vocational Education. Occasional Paper No. 26.

ERIC Educational Resources Information Center

Rieder, Corinne H.

Occupational segregation by sex caused by covert discrimination, often unintentional, effectively limits the careers pursued by both men and women. Data indicate that despite the gains in the number of employed women, job segregation patterns that confine women to the traditional female occupations persist and worsen along with the resultant low…

Gender-Segregated Schooling: A Problem Disguised as a Solution

ERIC Educational Resources Information Center

Fabes, Richard A.; Martin, Carol Lynn; Hanish, Laura D.; Galligan, Kathrine; Pahlke, Erin

2015-01-01

Gender-segregated (GS) schooling has become popular in the United States despite the fact that every major review has concluded that GS schooling is not superior to coeducational schooling. Moreover, concern has been raised that GS schooling leads to negative effects, including increased gender stereotyping. We argue that these negative effects…

Gender Segregation: Separate but Effective?

ERIC Educational Resources Information Center

Holthouse, David

2010-01-01

In 2002, only 11 public schools in the United States had gender-segregated classrooms. As of December 2009, there were more than 550. The movement is based on the hypothesis that hard-wired differences in the ways that male and female brains develop and function in childhood through adolescence require classrooms in which boys and girls are not…

Investigation of Artificial Forced Cooling in the Bridgman Crystal Growth of Cadmium Zinc Telluride

NASA Astrophysics Data System (ADS)

Liu, Juncheng; Li, Jiao; Zhang, Guodong; Li, Changxing; Lennon, Craig; Sivananthan, Siva

2007-08-01

The effects of artificial forced cooling on the solid liquid interface and on solute segregation were investigated by modeling the vertical Bridgman method for the single-crystal growth of CdZnTe, taking into consideration effects such as increasing the axial outward heat flux from the crucible bottom, the radial outward heat flux from the crucible wall, and the carbon film thickness on the crucible inner wall. Axial artificially forced cooling noticeably increases convection and the temperature gradient in the melt next to the solid liquid interface, and substantially reduces interface concavity at the initial solidification stage. Interface concavity increases a little when the solidification proceeds further, however. Axial artificially forced cooling reduces radial solute segregation of the initial segment of the grown crystal and slightly increases the solute iso-concentration segment. Radial artificially forced cooling enhances melt convection substantially, affects solid liquid interface concavity only slightly, and hardly affects solute segregation in the grown crystal. Doubling the carbon film thickness weakens convection of the melt in front of the interface, substantially increases interface concavity, and hardly affects solute segregation in the grown crystal.

Segregation of biomedical waste in an South Indian tertiary care hospital.

PubMed

Sengodan, Vetrivel Chezian

2014-07-01

Hospital wastes pose significant public health hazard if not properly managed. Hence, it is necessary to develop and adopt optimal waste management systems in the hospitals. Biomedical waste generated in Coimbatore Medical College Hospital was color coded (blue, yellow, and red) and the data was analyzed retrospectively on a daily basis for 3 years (January 2010-December 2012). Effective segregation protocols significantly reduced biomedical waste generated from 2011 to 2012. While biomedical waste of red category was significantly higher (>50%), the category yellow was the least. Per unit (per bed per day) total biomedical waste generated was 68.5, 68.8, and 61.3 grams in 2010, 2011, and 2012, respectively. Segregation of biomedical waste at the source of generation is the first and essential step in biomedical waste management. Continuous training, fixing the responsibility on the nursing persons, and constant supervision are the key criteria's in implementing biomedical waste segregation process, which can significantly reduce per unit biomedical waste generated. We highly recommend all hospitals to adopt our protocol and effectively implement them to reduce generation of biomedical waste.

Segregated nodal domains of two-dimensional multispecies Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Chang, Shu-Ming; Lin, Chang-Shou; Lin, Tai-Chia; Lin, Wen-Wei

2004-09-01

In this paper, we study the distribution of m segregated nodal domains of the m-mixture of Bose-Einstein condensates under positive and large repulsive scattering lengths. It is shown that components of positive bound states may repel each other and form segregated nodal domains as the repulsive scattering lengths go to infinity. Efficient numerical schemes are created to confirm our theoretical results and discover a new phenomenon called verticillate multiplying, i.e., the generation of multiple verticillate structures. In addition, our proposed Gauss-Seidel-type iteration method is very effective in that it converges linearly in 10-20 steps.

Effect of heat transfer of melt/solid interface shape and solute segregation in Edge-Defined Film-Fed growth - Finite element analysis

NASA Technical Reports Server (NTRS)

Ettouney, H. M.; Brown, R. A.

1982-01-01

The effects of the heat transfer environment in Edge-Defined Film-Fed Growth on melt-solid interface shape and lateral dopant segregation are studied by finite-element analysis of two-dimensional models for heat and mass transfer. Heat transfer configurations are studied that correspond to the uniform surroundings assumed in previous models and to lowand high-speed growth systems. The maximum growth rate for a silicon sheet is calculated and the range of validity of one-dimensional heat transfer models is established. The lateral segregation that results from curvature of the solidification interface is calculated for two solutes, boron and aluminum. In this way, heat transfer is linked directly to the uniformity of the product crystal.

[Genetic characteristics associated with drought tolerance of plant height and thousand-grain mass of recombinant inbred lines of wheat].

PubMed

Yang, De-Long; Zhang, Guo-Hong; Li, Xing-Mao; Xing, Hua; Cheng, Hong-Bo; Ni, Sheng-Li; Chen, Xiao-Ping

2012-06-01

A total of 120 recombinant inbred lines (RIL) derived from Chinese winter wheat cultivars Longjian 19xQ9086 and the two parents were taken as test materials to study the quantitative genetics characteristics of their plant height at different development stages, thousand-grain mass, as well as the correlations between the two traits under rainfed (drought stress) and well-watered conditions, and evaluate the genetic variation of the RIL. Under the two water conditions, the target traits of the RIL showed substantial transgressive segregation and great sensitivity to water condition. The drought stress coefficient of the plant height was higher at jointing stage, being up to 0.851. There was a significant positive correlation between the plant height at different development stages and the thousand-grain mass, and comparing with that at other growth stages, the plant height at jointing stage had a higher correlation coefficient with the thousand-grain mass (R2DS = 0.32, R2WW = 0.28). The plant height at both jointing and flowering stages had significant positive and direct effect but negative and indirect gross effect on the thousand-grain mass, while the plant height at heading and maturing stages was in adverse. The target traits showed a lower heritability ranged from 0.27 to 0.60. The numbers of the gene pairs controlling the thousand-grain mass were 10 under rainfed and 13 under well-watered conditions, while those of the gene pairs controlling the plant height at different development stages were 3-7 under rainfed and 4-14 under well-watered conditions, respectively. According to the clustering of the drought stress coefficient of plant height, the RIL could be classified into five subgroups, showing the abundant variation of the RIL in their phe- notypes and in the sensitivity to water condition. It was considered that the test RIL were appropriate for the study of the quantitative genetics of wheat drought resistance.

Heroin mismatch in the Motor City: addiction, segregation, and the geography of opportunity.

PubMed

Draus, Paul; Roddy, Juliette; Greenwald, Mark

2012-01-01

In this article, the authors used data from economic and ethnographic interviews with heroin users from Detroit, Michigan, as well as other sources, to illustrate the relationship between heroin users' mobility patterns and urban and suburban environments, especially in terms of drug acquisition and the geography of opportunity. The authors found that although geographic location and social networks associated with segregation provided central city residents and African Americans with a strategic advantage over White suburbanites in locating and purchasing heroin easily and efficiently, this same segregation effectively focuses the negative externalities of heroin markets in central city neighborhoods. Finally, the authors consider how the heroin trade reflects and reproduces the segregated post-industrial landscape and discuss directions for future research about the relationship between ethnic and economic ghettos and regional drug markets.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ying

Radiation-induced segregation (RIS) has been frequently reported in structural materials such as austenitic, ferritic, and ferritic-martensitic stainless steels (SS) that have been widely used in light water reactors (LWRs). RIS has been linked to secondary degradation effects in SS including irradiation-induced stress corrosion cracking (IASCC). Earlier studies on thermal segregation in Fe-based alloys found that metalloids elements such as P, S, Si, Ge, Sn, etc., embrittle the materials when enrichment was observed at grain boundaries (GBs). RIS of Fe-Cr-Ni-based austenitic steels has been modeled in the U.S. 2015 fiscal year (FY2015), which identified the pre-enrichment due to thermal segregation canmore » have an important role on the subsequent RIS. The goal of this work is to develop thermal segregation models for alloying elements in steels for future integration with RIS modeling.« less

High compositional homogeneity of CdTe{sub x}Se{sub 1−x} crystals grown by the Bridgman method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, U. N.; Bolotnikov, A. E.; Camarda, G. S.

2015-02-01

We obtained high-quality CdTe{sub x}Se{sub 1−x} (CdTeSe) crystals from ingots grown by the vertical Bridgman technique. The compositional uniformity of the ingots was evaluated by X-ray fluorescence at BNL’s National Synchrotron Light Source X27A beam line. The compositional homogeneity was highly uniform throughout the ingot, and the effective segregation coefficient of Se was ∼1.0. This high uniformity offers potential opportunity to enhance the yield of the materials for both infrared substrate and radiation-detector applications, so greatly lowering the cost of production and also offering us the prospect to grow large-diameter ingots for use as large-area substrates and for producing highermore » efficiency gamma-ray detectors. The concentration of secondary phases was found to be much lower, by eight- to ten fold compared to that of conventional Cd{sub x}Zn{sub 1−x}Te (CdZnTe or CZT)« less

High Compositional Homogeneity of CdTe xSe 1-x Crystals Grown by the Bridgman Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, U. N.; Bolotnikov, A. E.; Camarda, G. S.

2015-02-03

We obtained high-quality CdTe xSe 1-x (CdTeSe) crystals from ingots grown by the vertical Bridgman technique. The compositional uniformity of the ingots was evaluated by X-ray fluorescence at BNL’s National Synchrotron Light Source X27A beam line. The resulting compositional homogeneity was highly uniform throughout the ingot, and the effective segregation coefficient of Se was ~1.0. This uniformity offers potential opportunity to enhance the yield of the materials for both infrared substrate and radiation-detector applications, so greatly lowering the cost of production and also offering us the prospect to grow large-diameter ingots for use as large-area substrates and for producing highermore » efficiency gamma-ray detectors. The concentration of secondary phases was found to be much lower, by eight- to ten fold compared to that of conventional Cd xZn 1-xTe (CdZnTe or CZT).« less

Heat-induced redistribution of surface oxide in uranium

NASA Astrophysics Data System (ADS)

Swissa, Eli; Shamir, Noah; Mintz, Moshe H.; Bloch, Joseph

1990-09-01

The redistribution of oxygen and uranium metal at the vicinity of the metal-oxide interface of native and grown oxides due to vacuum thermal annealing was studied for uranium and uranium-chromium alloy using Auger depth profiling and metallographic techniques. It was found that uranium metal is segregating out through the uranium oxide layer for annealing temperatures above 450°C. At the same time the oxide is redistributed in the metal below the oxide-metal interface in a diffusion like process. By applying a diffusion equation of a finite source, the diffusion coefficients for the process were obtained from the oxygen depth profiles measured for different annealing times. An Arrhenius like behavior was found for the diffusion coefficient between 400 and 800°C. The activation energy obtained was Ea = 15.4 ± 1.9 kcal/mole and the pre-exponential factor, D0 = 1.1 × 10 -8cm2/ s. An internal oxidation mechanism is proposed to explain the results.

The Growth and Characterization of the Bismuth Strontium-Calcium 2212 Superconductor

NASA Astrophysics Data System (ADS)

Moulton, Linda Vidale

A miniaturized float zone technique, sometimes referred to as the Laser-heated Pedestal Growth (LHPG) method, was used to produce high quality crystals of the incongruently melting rm Bi_2Sr_2CaCu _2O_{8+delta} (2212) superconductor. The main focus of this research was to (1) produce superconducting samples having different compositions, (2) identify the melt compositions and growth temperatures which produced these samples, and (3) determine the variation of their superconducting transition temperature (T _{rm C}) with composition and processing conditions. The rm Bi_2(Sr,Ca) _3Cu_2O_{8+delta} crystallization experiments were supplemented by a series of similar experiments on the incongruently melting compound rm Ca_3Al_2O_6. The phase equilibria in the CaO-rm Al_2O _3 system has been thoroughly studied, and by analyzing the float-zone growth of this simpler and better-characterized material, it was verified that phase equilibria information and solidification behavior could be extracted from and explained by these solidification experiments. Two different types of nonplanar, crystal/melt interface morphologies were observed in the rm Ca_3Al_2O_6 experiments. Each reflected the influence of the phase equilibria in the CaO-rm Al_2O_3 system and component segregation in the melt. The molten zone compositions were found to approach those predicted by the CaO-rm Al_2O_3 phase diagram as the growth rate decreased, in accordance with the Burton-Prim Slichter relationship. Excellent agreement was obtained between actual phases found to coexist at the rm Ca_3Al_2O_6 /melt interface and the predictions of classical crystal growth theory. Based on the results of the rm Ca _3Al_2O_6 crystallization study, the crystal/melt equilibria in the far more complex rm Bi_2O_3-SrO-CaO-CuO system was evaluated by determining the phases formed during the superconductor growth experiments. The melt compositions were found to be rm Bi_2O_3 -rich and SrO-poor relative to the compositions of the 2212 crystals grown from them. The CaO and CuO segregation coefficients, on the other hand, were observed to be near unity. As one would expect for an incongruently -melting compound, segregation at the solidification front generally decreased with increasing crystallization temperature, but all the segregation coefficients were not observed to simultaneously approach unity. The superconducting transition temperatures (T _{rm C}'s) of six as-crystallized samples having homogeneous crystal compositions were also measured. Sample T_{rm C} was observed to increase with increasing growth temperature and, therefore, change with crystal composition. The results of this study suggested that it is desirable to grow crystals at the highest possible crystallization temperature since they will: (1) have the highest as-grown T_{rm C} 's, and (2) solidify with the least component segregation at the growth interface. In addition, the analysis presented here suggests that such growth is not recommended at higher growth rates, since crystals with mid-range solidus compositions (and consequently, moderate growth temperatures) should crystallize most reliably as single-phase samples at higher growth rates.

A hydrodynamic model for granular material flows including segregation effects

NASA Astrophysics Data System (ADS)

Gilberg, Dominik; Klar, Axel; Steiner, Konrad

2017-06-01

The simulation of granular flows including segregation effects in large industrial processes using particle methods is accurate, but very time-consuming. To overcome the long computation times a macroscopic model is a natural choice. Therefore, we couple a mixture theory based segregation model to a hydrodynamic model of Navier-Stokes-type, describing the flow behavior of the granular material. The granular flow model is a hybrid model derived from kinetic theory and a soil mechanical approach to cover the regime of fast dilute flow, as well as slow dense flow, where the density of the granular material is close to the maximum packing density. Originally, the segregation model has been formulated by Thornton and Gray for idealized avalanches. It is modified and adapted to be in the preferred form for the coupling. In the final coupled model the segregation process depends on the local state of the granular system. On the other hand, the granular system changes as differently mixed regions of the granular material differ i.e. in the packing density. For the modeling process the focus lies on dry granular material flows of two particle types differing only in size but can be easily extended to arbitrary granular mixtures of different particle size and density. To solve the coupled system a finite volume approach is used. To test the model the rotational mixing of small and large particles in a tumbler is simulated.

Racial residential segregation impacts on low birth weight using improved neighborhood boundary definitions.

PubMed

Grady, Sue C

2010-12-01

Research on local racial residential segregation and health generally utilize census tract boundaries as a proxy from within which to estimate individual exposures. Census tracts however, may not accurately reflect the neighborhood environments in which people live and interact. Census tract geography may also capture non-exchangeable populations in socially stratified cities, impacting statistical assumptions of independence. To address these concerns, this study assessed the impact of racial residential segregation (i.e., racial isolation and racial clusters) on low birth weight (i.e., intrauterine growth retardation (IUGR) and preterm birth) in the Detroit Metropolitan Area using optimized neighborhood boundary definitions. Automated zone-matching (AZM) methodology was applied to redefine neighborhood (zones). Maternal and infant health information was obtained from Michigan's vital statistics birth registry (n=137,965) for the years 2004-2006. Multilevel models were estimated to assess the effect of high racial isolation and high racial clusters on IUGR and preterm birth, controlling for maternal race, single marital status, smoking and area-level poverty. The results from this study showed that high racial isolation had a significant effect on IUGR, while the odds of preterm birth were higher in racially clustered zones. African American mothers were at increased odds of having IUGR or preterm infants than other mothers; however, these disparities reduced in highly segregated zones. The predicted incidence of IUGR across racially isolated zones and census tracts differed indicating a modifiable area unit problem (MAUP). MAUP effects were not observed in models predicting preterm incidence in high racial clusters or IUGR or preterm incidence in high poverty areas, demonstrating the stability-reliability of these estimates. Future research should continue to optimize neighborhood boundary definitions, while assessing the sensitivity of segregation measures to changes in scale, to improve our understanding of segregation impacts on racial disparities in low birth weight. Copyright © 2010 Elsevier Inc. All rights reserved.

Instabilities in rapid solidification of multi-component alloys

NASA Astrophysics Data System (ADS)

Altieri, Anthony L.; Davis, Stephen H.

2017-10-01

Rapid solidification of multi-component liquids occurs in many modern applications such as additive manufacturing. In the present work the interface departures from equilibrium consist of the segregation coefficient and liquidus slope depending on front speed, the one-sided, frozen-temperature approximation, and the alloy behaving as the superposition of individual components. Linear-stability theory is applied, showing that the cellular and oscillatory instabilities of the binary case are modified. The addition of components tends to destabilize the interface while the addition of a single large-diffusivity material can entirely suppress the oscillatory mode. Multiple minima in the neutral curve for the cellular mode occur.

Transport properties of C and O in UN fuels

NASA Astrophysics Data System (ADS)

Schuler, Thomas; Lopes, Denise Adorno; Claisse, Antoine; Olsson, Pär

2017-03-01

Uranium nitride fuel is considered for fast reactors (GEN-IV generation and space reactors) and for light water reactors as a high-density fuel option. Despite this large interest, there is a lack of information about its behavior for in-pile and out-of-pile conditions. From the present literature, it is known that C and O impurities have significant influence on the fuel performance. Here we perform a systematic study of these impurities in the UN matrix using electronic-structure calculations of solute-defect interactions and microscopic jump frequencies. These quantities were calculated in the DFT +U approximation combined with the occupation matrix control scheme, to avoid convergence to metastable states for the 5 f levels. The transport coefficients of the system were evaluated with the self-consistent mean-field theory. It is demonstrated that carbon and oxygen impurities have different diffusion properties in the UN matrix, with O atoms having a higher mobility, and C atoms showing a strong flux coupling anisotropy. The kinetic interplay between solutes and vacancies is expected to be the main cause for surface segregation, as incorporation energies show no strong thermodynamic segregation preference for (001) surfaces compared with the bulk.

Segregation and Poverty Concentration: The Role of Three Segregations

PubMed Central

Quillian, Lincoln

2014-01-01

A key argument of Massey and Denton’s American Apartheid (1993) is that racial residential segregation and non-white group poverty rates combine interactively to produce spatially concentrated poverty. Despite a compelling theoretical rationale, the empirical tests of this proposition have been negative or mixed. This paper develops a formal decomposition model that expands the Massey model of how segregation, group poverty rates, and other spatial conditions combine to form concentrated poverty. The revised decomposition model allows for income effects on cross-race neighborhood residence and interactive combinations of multiple spatial conditions in the formation of concentrated poverty. Applying the model to data reveals that racial segregation and income segregation within race contribute importantly to poverty concentration, as Massey argued, but that almost equally important for poverty concentration is the disproportionate poverty of the non-group neighbors of blacks and Hispanics. The missing interaction Massey expected in empirical tests can be found with proper accounting for the factors in the expanded model. “Because of racial segregation, a significant share of black America is condemned to experience a social environment where poverty and joblessness are the norm, where a majority of children are born out of wedlock, where most families are on welfare, where educational failure prevails, and where social and physical deterioration abound. Through prolonged exposure to such an environment, black chances for social and economic success are drastically reduced.”--Douglas Massey and Nancy Denton, American Apartheid, p. 2 PMID:24648570

Effect of Segregation of Secondary Phase Particles and "S" Line on Tensile Fracture Behavior of Friction Stir-Welded 2024Al-T351 Joints

NASA Astrophysics Data System (ADS)

Zhang, Z.; Xiao, B. L.; Ma, Z. Y.

2013-09-01

A 5-mm-thick 2024Al-T351 plate was friction stir welded (FSWed) at welding speeds of 100, 200, and 400 mm min-1 with a constant rotation rate of 800 rpm, and the microstructure and tensile fracture behavior of the joints were investigated in detail. FSW resulted in the redistribution of secondary phase particles along the recrystallized grain boundaries at the nugget zone (NZ), forming linear segregation bands consisting of secondary phase particles. The segregation bands, mainly present in the shoulder-driven zone, were believed to result from periodic material flow, with the average band spacing on the longitudinal and horizontal cross sections equal to the tool advancement per revolution. At a low welding speed of 100 mm min-1, in spite of the highest density of segregation bands, the FSWed 2024Al-T351 joint fractured along the low hardness zone (LHZ) of the heat-affected zone because of large hardness gap between NZ and LHZ. Increasing the welding speed to 200 and 400 mm min-1 reduced both the hardness gap between NZ and LHZ and the density of segregation bands. In this case, the segregation bands played a role, resulting in unusual fracture of the joints along the segregation bands. The "S" line originated from the oxide film on the initial butting surfaces and did not affect the fracture behavior of the FSWed 2024Al-T351 joints.

Racial Segregation and the American Foreclosure Crisis

PubMed Central

Rugh, Jacob S.; Massey, Douglas S.

2013-01-01

Although the rise in subprime lending and the ensuing wave of foreclosures was partly a result of market forces that have been well-identified in the literature, in the United States it was also a highly racialized process. We argue that residential segregation created a unique niche of poor minority clients who were differentially marketed risky subprime loans that were in great demand for use in mortgage-backed securities that could be sold on secondary markets. We test this argument by regressing foreclosure actions in the top 100 U.S. metropolitan areas on measures of black, Hispanic, and Asian segregation while controlling for a variety of housing market conditions, including average creditworthiness, the extent of coverage under the Community Reinvestment Act, the degree of zoning regulation, and the overall rate of subprime lending. We find that black residential dissimilarity and spatial isolation are powerful predictors of foreclosures across U.S. metropolitan areas. In order to isolate subprime lending as the causal mechanism whereby segregation influences foreclosures, we estimate a two-stage least squares model that confirms the causal effect of black segregation on the number and rate of foreclosures across metropolitan areas. In the United States segregation was an important contributing cause of the foreclosure crisis, along with overbuilding, risky lending practices, lax regulation, and the bursting of the housing price bubble. PMID:25308973

Residential segregation and mental health among Latinos in a nationally representative survey

PubMed Central

Nobles, Carrie J; Valentine, Sarah E; Zepeda, E David; Wang, Ye; Ahles, Emily M; Shtasel, Derri L; Marques, Luana

2017-01-01

Background Among Latinos, living in a locality with greater Latino ethnic density may be protective for mental health, although findings vary by Latino subgroup, gender and birthplace. Although little studied, Latino residential segregation may capture different pathways linking risk and protective environmental factors to mental health than local ethnic density. Methods This study evaluated the association between residential segregation and mental distress as measured by the Kessler-10 (K10) among Latino participants in the National Latino and Asian American Study (NLAAS). Census data from 2000 was used to calculate metropolitan statistical area (MSA) residential segregation using the dissimilarity and isolation indices, as well as census tract ethnicity density and poverty. Latino subgroup (Puerto Rican, Mexican American, Cuban American and other Latino subgroup), gender and generation status were evaluated as moderators. Results Among 2554 Latino participants in NLAAS, residential segregation as measured by the isolation index was associated with less mental distress (β −0.14, 95% CI −0.26 to −0.03 log(K10)) among Latinos overall after adjustment for ethnic density, poverty and individual covariates. Residential segregation as measured by the dissimilarity index was significantly associated with less mental distress among men (β −0.56, 95% CI −1.04 to −0.08) but not among women (β −0.20, 95% CI −0.45 to 0.04, p-interaction=0.019). No modification was observed by Latino subgroup or generation. Conclusions Among Latinos, increasing residential segregation was associated with less mental distress, and this association was moderated by gender. Findings suggest that MSA-level segregation measures may capture protective effects associated with living in Latino communities for mental health. PMID:27885049

Reverberation impairs brainstem temporal representations of voiced vowel sounds: challenging “periodicity-tagged” segregation of competing speech in rooms

PubMed Central

Sayles, Mark; Stasiak, Arkadiusz; Winter, Ian M.

2015-01-01

The auditory system typically processes information from concurrently active sound sources (e.g., two voices speaking at once), in the presence of multiple delayed, attenuated and distorted sound-wave reflections (reverberation). Brainstem circuits help segregate these complex acoustic mixtures into “auditory objects.” Psychophysical studies demonstrate a strong interaction between reverberation and fundamental-frequency (F0) modulation, leading to impaired segregation of competing vowels when segregation is on the basis of F0 differences. Neurophysiological studies of complex-sound segregation have concentrated on sounds with steady F0s, in anechoic environments. However, F0 modulation and reverberation are quasi-ubiquitous. We examine the ability of 129 single units in the ventral cochlear nucleus (VCN) of the anesthetized guinea pig to segregate the concurrent synthetic vowel sounds /a/ and /i/, based on temporal discharge patterns under closed-field conditions. We address the effects of added real-room reverberation, F0 modulation, and the interaction of these two factors, on brainstem neural segregation of voiced speech sounds. A firing-rate representation of single-vowels' spectral envelopes is robust to the combination of F0 modulation and reverberation: local firing-rate maxima and minima across the tonotopic array code vowel-formant structure. However, single-vowel F0-related periodicity information in shuffled inter-spike interval distributions is significantly degraded in the combined presence of reverberation and F0 modulation. Hence, segregation of double-vowels' spectral energy into two streams (corresponding to the two vowels), on the basis of temporal discharge patterns, is impaired by reverberation; specifically when F0 is modulated. All unit types (primary-like, chopper, onset) are similarly affected. These results offer neurophysiological insights to perceptual organization of complex acoustic scenes under realistically challenging listening conditions. PMID:25628545

Disparities in Surgical Treatment of Early-Stage Breast Cancer Among Female Residents of Texas: The Role of Racial Residential Segregation.

PubMed

Ojinnaka, Chinedum O; Luo, Wen; Ory, Marcia G; McMaughan, Darcy; Bolin, Jane N

2017-04-01

Early-stage breast cancer can be surgically treated by using mastectomy or breast-conserving surgery and adjuvant radiotherapy, also known as breast-conserving therapy (BCT). Little is known about the association between racial residential segregation, year of diagnosis, and surgical treatment of early-stage breast cancer, and whether racial residential segregation influences the association between other demographic characteristics and disparities in surgical treatment. This was a retrospective study using data from the Texas Cancer Registry composed of individuals diagnosed with breast cancer between 1995 and 2012. The dependent variable was treatment using mastectomy or BCT (M/BCT) and the independent variables of interest (IVs) were racial residential segregation and year of diagnosis. The covariates were race, residence, ethnicity, tumor grade, census tract (CT) poverty level, age at diagnosis, stage at diagnosis, and year of diagnosis. Bivariate and multivariable multilevel logistic regression models were estimated. The final sample size was 69,824 individuals nested within 4335 CTs. Adjusting for the IVs and all covariates, there were significantly decreased odds of treatment using M/BCT, as racial residential segregation increased from 0 to 1 (odds ratio [OR] 0.47; 95% confidence interval [CI], 0.41-0.54). There was also an increased likelihood of treatment using M/BCT with increasing year of diagnosis (OR 1.14; 95% CI, 1.13-1.16). A positive interaction effect between racial residential segregation and race was observed (OR 0.56; 95% CI, 0.36-0.88). Residents of areas with high indices of racial residential segregation were less likely to be treated with M/BCT. Racial disparities in treatment using M/BCT increased with increasing racial residential segregation. Copyright © 2016 Elsevier Inc. All rights reserved.

The Racial/Ethnic Distribution of Heat Risk–Related Land Cover in Relation to Residential Segregation

PubMed Central

Morello-Frosch, Rachel; Cushing, Lara

2013-01-01

Objective: We examined the distribution of heat risk–related land cover (HRRLC) characteristics across racial/ethnic groups and degrees of residential segregation. Methods: Block group–level tree canopy and impervious surface estimates were derived from the 2001 National Land Cover Dataset for densely populated urban areas of the United States and Puerto Rico, and linked to demographic characteristics from the 2000 Census. Racial/ethnic groups in a given block group were considered to live in HRRLC if at least half their population experienced the absence of tree canopy and at least half of the ground was covered by impervious surface (roofs, driveways, sidewalks, roads). Residential segregation was characterized for metropolitan areas in the United States and Puerto Rico using the multigroup dissimilarity index. Results: After adjustment for ecoregion and precipitation, holding segregation level constant, non-Hispanic blacks were 52% more likely (95% CI: 37%, 69%), non-Hispanic Asians 32% more likely (95% CI: 18%, 47%), and Hispanics 21% more likely (95% CI: 8%, 35%) to live in HRRLC conditions compared with non-Hispanic whites. Within each racial/ethnic group, HRRLC conditions increased with increasing degrees of metropolitan area-level segregation. Further adjustment for home ownership and poverty did not substantially alter these results, but adjustment for population density and metropolitan area population attenuated the segregation effects, suggesting a mediating or confounding role. Conclusions: Land cover was associated with segregation within each racial/ethnic group, which may be explained partly by the concentration of racial/ethnic minorities into densely populated neighborhoods within larger, more segregated cities. In anticipation of greater frequency and duration of extreme heat events, climate change adaptation strategies, such as planting trees in urban areas, should explicitly incorporate an environmental justice framework that addresses racial/ethnic disparities in HRRLC. PMID:23694846

Residential segregation and mental health among Latinos in a nationally representative survey.

PubMed

Nobles, Carrie J; Valentine, Sarah E; Zepeda, E David; Wang, Ye; Ahles, Emily M; Shtasel, Derri L; Marques, Luana

2017-04-01

Among Latinos, living in a locality with greater Latino ethnic density may be protective for mental health, although findings vary by Latino subgroup, gender and birthplace. Although little studied, Latino residential segregation may capture different pathways linking risk and protective environmental factors to mental health than local ethnic density. This study evaluated the association between residential segregation and mental distress as measured by the Kessler-10 (K10) among Latino participants in the National Latino and Asian American Study (NLAAS). Census data from 2000 was used to calculate metropolitan statistical area (MSA) residential segregation using the dissimilarity and isolation indices, as well as census tract ethnicity density and poverty. Latino subgroup (Puerto Rican, Mexican American, Cuban American and other Latino subgroup), gender and generation status were evaluated as moderators. Among 2554 Latino participants in NLAAS, residential segregation as measured by the isolation index was associated with less mental distress (β -0.14, 95% CI -0.26 to -0.03 log(K10)) among Latinos overall after adjustment for ethnic density, poverty and individual covariates. Residential segregation as measured by the dissimilarity index was significantly associated with less mental distress among men (β -0.56, 95% CI -1.04 to -0.08) but not among women (β -0.20, 95% CI -0.45 to 0.04, p-interaction=0.019). No modification was observed by Latino subgroup or generation. Among Latinos, increasing residential segregation was associated with less mental distress, and this association was moderated by gender. Findings suggest that MSA-level segregation measures may capture protective effects associated with living in Latino communities for mental health. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

On the genetic parameter determining the efficiency of purging: an estimate for Drosophila egg-to-pupae viability.

PubMed

Bersabé, D; García-Dorado, A

2013-02-01

The consequences of inbreeding on fitness can be crucial in evolutionary and conservation grounds and depend upon the efficiency of purging against deleterious recessive alleles. Recently, analytical expressions have been derived to predict the evolution of mean fitness, taking into account both inbreeding and purging, which depend on an 'effective purging coefficient (d(e) )'. Here, we explore the validity of that predictive approach and assay the strength of purging by estimating d(e) for egg-to-pupae viability (EPV) after a drastic reduction in population size in a recently captured base population of Drosophila melanogaster. For this purpose, we first obtained estimates of the inbreeding depression rate (δ) for EPV in the base population, and we found that about 40% was due to segregating recessive lethals. Then, two sets of lines were founded from this base population and were maintained with different effective size throughout the rest of the experiment (N = 6; N = 12), their mean EPV being assayed at different generations. Due to purging, the reductions in mean EPV experienced by these lines were considerably smaller than the corresponding neutral predictions. For the 60% of δ attributable to nonlethal deleterious alleles, our results suggest an effective purging coefficient d(e) > 0.02. Similarly, we obtain that d(e) > 0.09 is required to roughly account for purging against the pooled inbreeding depression from lethal and nonlethal deleterious alleles. This implies that purging should be efficient for population sizes of the order of a few tens and larger, but might be inefficient against nonlethal deleterious alleles in smaller populations. © 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology.

Sound stream segregation: a neuromorphic approach to solve the “cocktail party problem” in real-time

PubMed Central

Thakur, Chetan Singh; Wang, Runchun M.; Afshar, Saeed; Hamilton, Tara J.; Tapson, Jonathan C.; Shamma, Shihab A.; van Schaik, André

2015-01-01

The human auditory system has the ability to segregate complex auditory scenes into a foreground component and a background, allowing us to listen to specific speech sounds from a mixture of sounds. Selective attention plays a crucial role in this process, colloquially known as the “cocktail party effect.” It has not been possible to build a machine that can emulate this human ability in real-time. Here, we have developed a framework for the implementation of a neuromorphic sound segregation algorithm in a Field Programmable Gate Array (FPGA). This algorithm is based on the principles of temporal coherence and uses an attention signal to separate a target sound stream from background noise. Temporal coherence implies that auditory features belonging to the same sound source are coherently modulated and evoke highly correlated neural response patterns. The basis for this form of sound segregation is that responses from pairs of channels that are strongly positively correlated belong to the same stream, while channels that are uncorrelated or anti-correlated belong to different streams. In our framework, we have used a neuromorphic cochlea as a frontend sound analyser to extract spatial information of the sound input, which then passes through band pass filters that extract the sound envelope at various modulation rates. Further stages include feature extraction and mask generation, which is finally used to reconstruct the targeted sound. Using sample tonal and speech mixtures, we show that our FPGA architecture is able to segregate sound sources in real-time. The accuracy of segregation is indicated by the high signal-to-noise ratio (SNR) of the segregated stream (90, 77, and 55 dB for simple tone, complex tone, and speech, respectively) as compared to the SNR of the mixture waveform (0 dB). This system may be easily extended for the segregation of complex speech signals, and may thus find various applications in electronic devices such as for sound segregation and speech recognition. PMID:26388721

Sound stream segregation: a neuromorphic approach to solve the "cocktail party problem" in real-time.

PubMed

Thakur, Chetan Singh; Wang, Runchun M; Afshar, Saeed; Hamilton, Tara J; Tapson, Jonathan C; Shamma, Shihab A; van Schaik, André

2015-01-01

The human auditory system has the ability to segregate complex auditory scenes into a foreground component and a background, allowing us to listen to specific speech sounds from a mixture of sounds. Selective attention plays a crucial role in this process, colloquially known as the "cocktail party effect." It has not been possible to build a machine that can emulate this human ability in real-time. Here, we have developed a framework for the implementation of a neuromorphic sound segregation algorithm in a Field Programmable Gate Array (FPGA). This algorithm is based on the principles of temporal coherence and uses an attention signal to separate a target sound stream from background noise. Temporal coherence implies that auditory features belonging to the same sound source are coherently modulated and evoke highly correlated neural response patterns. The basis for this form of sound segregation is that responses from pairs of channels that are strongly positively correlated belong to the same stream, while channels that are uncorrelated or anti-correlated belong to different streams. In our framework, we have used a neuromorphic cochlea as a frontend sound analyser to extract spatial information of the sound input, which then passes through band pass filters that extract the sound envelope at various modulation rates. Further stages include feature extraction and mask generation, which is finally used to reconstruct the targeted sound. Using sample tonal and speech mixtures, we show that our FPGA architecture is able to segregate sound sources in real-time. The accuracy of segregation is indicated by the high signal-to-noise ratio (SNR) of the segregated stream (90, 77, and 55 dB for simple tone, complex tone, and speech, respectively) as compared to the SNR of the mixture waveform (0 dB). This system may be easily extended for the segregation of complex speech signals, and may thus find various applications in electronic devices such as for sound segregation and speech recognition.

Size segregation in a granular bore

NASA Astrophysics Data System (ADS)

Edwards, A. N.; Vriend, N. M.

2016-10-01

We investigate the effect of particle-size segregation in an upslope propagating granular bore. A bidisperse mixture of particles, initially normally graded, flows down an inclined chute and impacts with a closed end. This impact causes the formation of a shock in flow thickness, known as a granular bore, to travel upslope, leaving behind a thick deposit. This deposit imprints the local segregated state featuring both pure and mixed regions of particles as a function of downstream position. The particle-size distribution through the depth is characterized by a thin purely small-particle layer at the base, a significant linear transition region, and a thick constant mixed-particle layer below the surface, in contrast to previously observed S-shaped steady-state concentration profiles. The experimental observations agree with recent progress that upward and downward segregation of large and small particles respectively is asymmetric. We incorporate the three-layer, experimentally observed, size-distribution profile into a depth-averaged segregation model to modify it accordingly. Numerical solutions of this model are able to match our experimental results and therefore motivate the use of a more general particle-size distribution profile.

Detection of component segregation in granules manufactured by high shear granulation with over-granulation conditions using near-infrared chemical imaging.

PubMed

Koide, Tatsuo; Nagato, Takuya; Kanou, Yoshiyuki; Matsui, Kou; Natsuyama, Susumu; Kawanishi, Toru; Hiyama, Yukio

2013-01-30

The objective of this study was to evaluate the high shear granulation process using near-infrared (NIR) chemical imaging technique and to make the findings available for pharmaceutical development. We prepared granules and tablets made under appropriate- and over-granulation conditions with high shear granulation and observed these granules and tablets using NIR chemical imaging system. We found an interesting phenomenon: lactose agglomeration and segregation of ingredients occurred in experimental tablets when over-granulation conditions, including greater impeller rotation speeds and longer granulation times, were employed. Granules prepared using over-granulation conditions were larger and had progressed to the consolidation stage; segregation between ethenzamide and lactose occurred within larger granules. The segregation observed here is not detectable using conventional analytical technologies such as high pressure liquid chromatography (HPLC) because the content of the granules remained uniform despite the segregation. Therefore, granule visualization using NIR chemical imaging is an effective method for investigating and evaluating the granulation process. Copyright © 2012 Elsevier B.V. All rights reserved.

Spatial heterogeneity and the evolution of sex in diploids.

PubMed

Agrawal, Aneil F

2009-07-01

Much of the theoretical work on the evolution of sex has focused on the effects of recombination. In diploids, segregation also occurs during sexual reproduction. Segregation breaks down some types of genetic associations that are not affected by recombination and thus influences the evolution of sex in ways that are not apparent from studying the evolution of recombination as a surrogate for sex. Here I examine the evolution of sex in diploids experiencing spatially heterogeneous selection. If divergent selection causes genetic differentiation, then migration can be a powerful force generating genetic associations that may not be favored by selection. An advantage to sex can arise from breaking down these associations. By examining modifiers of both sex and recombination, the model allows for a direct comparison of the forces acting on these related but different processes, illuminating the role of segregation. The model also includes inbreeding, which has been shown to be important for both segregation and recombination. I find that inbreeding affects the evolution of sex through segregation, not recombination. Several suggestions for empirical experiments are given.

On Macrosegregation

NASA Astrophysics Data System (ADS)

Ludwig, Andreas; Wu, Menghuai; Kharicha, Abdellah

2015-11-01

Macrosegregations, namely compositional inhomogeneities at a scale much larger than the microstructure, are typically classified according to their metallurgical appearance. In ingot castings, they are known as `A' and `V' segregation, negative cone segregation, and positive secondary pipe segregation. There exists `inverse' segregation at casting surfaces and `centerline' segregation in continuously cast slabs and blooms. Macrosegregation forms if a relative motion between the solute-enriched or -depleted melt and dendritic solid structures occurs. It is known that there are four basic mechanisms for the occurrence of macrosegregation. In the recent years, the numerical description of the combination of these mechanisms has become possible and so a tool has emerged which can be effectively used to get a deeper understanding into the process details which are responsible for the formation of the above-mentioned different macrosegregation appearances. Based on the most sophisticated numerical models, we consequently associate the four basic formation mechanisms with the physical phenomena happening during (i) DC-casting of copper-based alloys, (ii) DC-casting of aluminum-based alloys, (iii) continuous casting of steel, and (iv) ingot casting of steel.

Rethinking the two-body problem: the segregation of women into geographically dispersed occupations.

PubMed

Benson, Alan

2014-10-01

Empirical research on the family cites the tendency for couples to relocate for husbands' careers as evidence against the gender neutrality of household economic decisions. For these studies, occupational segregation is a concern because occupations are not random by sex and mobility is not random by occupation. I find that the tendency for households to relocate for husbands' careers is better explained by the segregation of women into geographically dispersed occupations rather than by the direct prioritization of men's careers. Among never-married workers, women relocate for work less often than men, and the gender effect disappears after occupational segregation is accounted for. Although most two-earner families feature husbands in geographically clustered jobs involving frequent relocation for work, families are no less likely to relocate for work when it belongs to the wife. I conclude that future research in household mobility should treat occupational segregation occurring prior to marriage rather than gender bias within married couples as the primary explanation for the prioritization of husbands' careers in household mobility decisions.

Blue straggler stars beyond the Milky Way: a non-segregated population in the Large Magellanic Cloud cluster NGC 2213

NASA Astrophysics Data System (ADS)

Li, Chengyuan; Hong, Jongsuk

2018-06-01

Using the high-resolution observations obtained by the Hubble Space Telescope, we analysed the blue straggler stars (BSSs) in the Large Magellanic Cloud cluster NGC 2213. We found that the radial distribution of BSSs is consistent with that of the normal giant stars in NGC 2213, showing no evidence of mass segregation. However, an analytic calculation carried out for these BSSs shows that they are already dynamically old, because the estimated half-mass relaxation time for these BSSs is significantly shorter than the isochronal age of the cluster. We also performed direct N-body simulations for an NGC 2213-like cluster to understand the dynamical processes that lead to this non-segregated radial distribution of BSSs. Our numerical simulation shows that the presence of black hole subsystems inside the cluster centre can significantly affect the dynamical evolution of BSSs. The combined effects of the delayed segregation, binary disruption, and exchange interactions of BSS progenitor binaries may result in this non-segregated radial distribution of BSSs in NGC 2213.

Effect of Trace Levels of Si on Microstructure and Grain Boundary Segregation in DOP-26 Iridium Alloy

NASA Astrophysics Data System (ADS)

Pierce, Dean; Muralidharan, Govindarajan; Heatherly, Lee; Fox, Ethan

2018-03-01

The thermodynamics and kinetics of Silicon (Si) segregation to grain boundaries in Iridium alloy DOP-26 with added trace levels of Si of 6, 11, 29, and 36 wppm was studied by Auger Electron Spectroscopy. The four alloys were annealed at 1500 or 1535 °C for 19 or 76 hours followed by cooling at three different rates. Si enrichment at the grain boundaries (GB) increased with increasing bulk Si content, with the grain boundary Si enrichment factors ranging from 62 to 344, depending on the bulk Si content and the cooling rate. Grain boundary Si contents increased with decreasing cooling rate in all alloys, indicating that Si GB segregation is influenced by both thermodynamic and kinetic factors in the alloys and temperature ranges of the study. A Langmuir-McLean isotherm-based model was successfully used to predict the temperature dependence of GB Si segregation in DOP-26 alloys with Si additions and estimate the temperature independent free energy of Si segregation to grain boundaries in DOP-26.

Re-Thinking the Two-Body Problem: The Segregation of Women into Geographically-Dispersed Occupations

PubMed Central

Benson, Alan

2014-01-01

Empirical research on the family cites the tendency for couples to relocate for husbands’ careers as evidence against the gender-neutrality of household economic decisions. For these studies, occupational segregation is a concern because occupations are not random by sex and mobility is not random by occupation. I find the tendency for households to relocate for husbands’ careers is better-explained by the segregation of women into geographically-dispersed occupations rather than by the direct prioritization of men’s careers. Among never-married workers, women relocate for work less-often than men and the gender effect disappears after accounting for occupational segregation. While most two-earner families feature husbands in geographically-clustered jobs involving frequent relocation for work, families are no-less-likely to relocate for work when it belongs to the wife. I conclude future research in household mobility should treat occupational segregation occurring prior to marriage rather than gender bias within married couples as the primary explanation for the prioritization of husbands’ careers in household mobility decisions. PMID:25189156

[Mechanism of mutant induction in the ade2 gene of diploid Saccharomyces cerevisiae yeasts by ultraviolet rays].

PubMed

Gordenin, D A; Inge-Vechtomov, S G

1981-01-01

Ultraviolet light (UV) at 3000 ergs/mm-2 induces ade2 mutants with a frequency about 10(-4) in wild-type haploid strains of yeast and about 10(-5) in diploid wild-type strains. UV irradiation effectively induced mitotic segregation of ade2 in the heterozygous diploid (the frequency of segregation is 6%). Interallelic complementation and localization spectra are similar for mutations induced both in haploids and diploids. The occurrence of ade2 mutants in diploids correlated with mitotic segregation of the marker his8 which is situated in the same arm of XY chromosome as ade2 is, distal to the centromere. Our data about the frequency of ade2 mutants in diploids and haploids, the frequency of ade2 mitotic segregation, mitotic segregation of other markers and genetic characteristics of ade2 mutations confirm the suggestion that the major mechanism of diploid ade2 mutants appearance is mutation in one of the two ADE2 alleles and consequent mitotic homozygotisation of mutation as a result of mitotic crossingover between ade2 and the centromere.

Epistatic Interactions Among Herbicide Resistances in Arabidopsis thaliana: The Fitness Cost of Multiresistance

PubMed Central

Roux, Fabrice; Camilleri, Christine; Giancola, Sandra; Brunel, Dominique; Reboud, Xavier

2005-01-01

The type of interactions among deleterious mutations is considered to be crucial in numerous areas of evolutionary biology, including the evolution of sex and recombination, the evolution of ploidy, the evolution of selfing, and the conservation of small populations. Because the herbicide resistance genes could be viewed as slightly deleterious mutations in the absence of the pesticide selection pressure, the epistatic interactions among three herbicide resistance genes (acetolactate synthase CSR, cellulose synthase IXR1, and auxin-induced AXR1 target genes) were estimated in both the homozygous and the heterozygous states, giving 27 genotype combinations in the model plant Arabidopsis thaliana. By analyzing eight quantitative traits in a segregating population for the three herbicide resistances in the absence of herbicide, we found that most interactions in both the homozygous and the heterozygous states were best explained by multiplicative effects (each additional resistance gene causes a comparable reduction in fitness) rather than by synergistic effects (each additional resistance gene causes a disproportionate fitness reduction). Dominance coefficients of the herbicide resistance cost ranged from partial dominance to underdominance, with a mean dominance coefficient of 0.07. It was suggested that the csr1-1, ixr1-2, and axr1-3 resistance alleles are nearly fully recessive for the fitness cost. More interestingly, the dominance of a specific resistance gene in the absence of herbicide varied according to, first, the presence of the other resistance genes and, second, the quantitative trait analyzed. These results and their implications for multiresistance evolution are discussed in relation to the maintenance of polymorphism at resistance loci in a heterogeneous environment. PMID:16020787

On Reconstructing School Segregation: The Efficacy and Equity of Single-Sex Schooling

ERIC Educational Resources Information Center

Billger, Sherrilyn M.

2009-01-01

A change to Title IX has spurred new single-sex public schooling in the US. Until recently, nearly all gender-segregated schools were private, and comprehensive data for public school comparisons are not yet available. To investigate the effects of single-sex education, I focus on within private sector comparisons, and additionally address…

School Racial Composition and Parental Choice: New Evidence on the Preferences of White Parents in the United States

ERIC Educational Resources Information Center

Billingham, Chase M.; Hunt, Matthew O.

2016-01-01

Racial segregation remains a persistent problem in U.S. schools. In this article, we examine how social psychological factors--in particular, individuals' perceptions of schools with varying demographic characteristics--may contribute to the ongoing structural problem of school segregation. We investigate the effects of school racial composition…

Choosing Segregation or Integration? The Extent and Effects of Ethnic Segregation in Dutch Cities

ERIC Educational Resources Information Center

Karsten, Sjoerd; Felix, Charles; Ledoux, Guuske; Meijnen, Wim; Roeleveld, Jaap; Van Schooten, Erik

2006-01-01

Across Europe, urban education systems are struggling with the process of integration of immigrants in schools. The process of inclusion and exclusion in European cities shows many similarities with earlier experiences in U.S. cities. This article explores the most important aspects of this new urban phenomenon and its impact on urban school…

The Role of Ethnic School Segregation for Adolescents' Religious Salience

ERIC Educational Resources Information Center

Van der Bracht, Koen; D'hondt, Fanny; Van Houtte, Mieke; Van de Putte, Bart; Stevens, Peter A. J.

2016-01-01

Public concerns over the possible effects of school segregation on immigrant and ethnic majority religiosity have been on the rise over the last few years. In this paper we focus on (1) the association between ethnic school composition and religious salience, (2) intergenerational differences in religious salience and (3) the role of ethnic school…

Complex segregation analysis of craniomandibular osteopathy in Deutsch Drahthaar dogs.

PubMed

Vagt, J; Distl, O

2018-01-01

This study investigated familial relationships among Deutsch Drahthaar dogs with craniomandibular osteopathy and examined the most likely mode of inheritance. Sixteen Deutsch Drahthaar dogs with craniomandibular osteopathy were diagnosed using clinical findings, radiography or computed tomography. All 16 dogs with craniomandibular osteopathy had one common ancestor. Complex segregation analyses rejected models explaining the segregation of craniomandibular osteopathy through random environmental variation, monogenic inheritance or an additive sex effect. Polygenic and mixed major gene models sufficiently explained the segregation of craniomandibular osteopathy in the pedigree analysis and offered the most likely hypotheses. The SLC37A2:c.1332C>T variant was not found in a sample of Deutsch Drahthaar dogs with craniomandibular osteopathy, nor in healthy controls. Craniomandibular osteopathy is an inherited condition in Deutsch Drahthaar dogs and the inheritance seems to be more complex than a simple Mendelian model. Copyright © 2017 Elsevier Ltd. All rights reserved.

Segregation-mobility feedback for bidisperse shallow granular flows: Towards understanding segregation in geophysical flows

NASA Astrophysics Data System (ADS)

Thornton, A.; Denissen, I.; Weinhart, T.; Van der Vaart, K.

2017-12-01

The flow behaviour of shallow granular chute flows for uniform particles is well-described by the hstop-rheology [1]. Geophysical flows, however, are often composed of highly non-uniform particles that differ in particle (size, shape, composition) or contact (friction, dissipation, cohesion) properties. The flow behaviour of such mixtures can be strongly influenced by particle segregation effects. Here, we study the influence of particle size-segregation on the flow behaviour of bidisperse flows using experiments and the discrete particle method. We use periodic DPM to derive hstop-rheology for the bi-dispersed granular shallow layer equations, and study their dependence on the segregation profile. In the periodic box simulations, size-segregation results in an upward coarsening of the size distribution with the largest grains collecting at the top of the flow. In geophysical flows, the fact the flow velocity is greatest at the top couples with the vertical segregation to preferentially transported large particles to the front. The large grains may be overrun, resegregated towards the surface and recirculated before being shouldered aside into lateral levees. Theoretically it has been suggested this process should lead to a breaking size-segregation (BSS) wave located between a large-particle-rich front and a small-particle-rich tail [2,3]. In the BSS wave large particles that have been overrun rise up again to the free-surface while small particles sink to the bed. We present evidence for the existences of the BSS wave. This is achieved through the study of three-dimensional bidisperse granular flows in a moving-bed channel. Our analysis demonstrates a relation between the concentration of small particles in the flow and the amount of basal slip, in which the structure of the BSS wave plays a key role. This leads to a feedback between the mean bulk flow velocity and the process of size-segregation. Ultimately, these findings shed new light on the recirculation of large and small grains near avalanche fronts and the effects of this behaviour on the mobility of the bulk flow. [1] Y. Forterre, O. Pouliquen, J. Fluid Mech. 486, 21-50 (2003) [2] A. R. Thornton, J. M. N. T. Gray J. Fluid Mech. 296 261-284 (2008) [3] P. Gajjar, K. van der Vaart, A. R. Thornton, C. G. Johnson, C. Ancey, J. M. N. T. Gray J. Fluid Mech 794, 460-505 (2016)

Controlling mixing and segregation in time periodic granular flows

NASA Astrophysics Data System (ADS)

Bhattacharya, Tathagata

Segregation is a major problem for many solids processing industries. Differences in particle size or density can lead to flow-induced segregation. In the present work, we employ the discrete element method (DEM)---one type of particle dynamics (PD) technique---to investigate the mixing and segregation of granular material in some prototypical solid handling devices, such as a rotating drum and chute. In DEM, one calculates the trajectories of individual particles based on Newton's laws of motion by employing suitable contact force models and a collision detection algorithm. Recently, it has been suggested that segregation in particle mixers can be thwarted if the particle flow is inverted at a rate above a critical forcing frequency. Further, it has been hypothesized that, for a rotating drum, the effectiveness of this technique can be linked to the probability distribution of the number of times a particle passes through the flowing layer per rotation of the drum. In the first portion of this work, various configurations of solid mixers are numerically and experimentally studied to investigate the conditions for improved mixing in light of these hypotheses. Besides rotating drums, many studies of granular flow have focused on gravity driven chute flows owing to its practical importance in granular transportation and to the fact that the relative simplicity of this type of flow allows for development and testing of new theories. In this part of the work, we observe the deposition behavior of both mono-sized and polydisperse dry granular materials in an inclined chute flow. The effects of different parameters such as chute angle, particle size, falling height and charge amount on the mass fraction distribution of granular materials after deposition are investigated. The simulation results obtained using DEM are compared with the experimental findings and a high degree of agreement is observed. Tuning of the underlying contact force parameters allows the achievement of realistic results and is used as a means of validating the model against available experimental data. The tuned model is then used to find the critical chute length for segregation based on the hypothesis that segregation can be thwarted if the particle flow is inverted at a rate above a critical forcing frequency. The critical frequency, fcrit, is inversely proportional to the characteristic time of segregation, ts. Mixing is observed instead of segregation when the chute length L < U avgts, where Uavg denotes the average stream-wise flow velocity of the particles. While segregation is often an undesired effect, sometimes separating the components of a particle mixture is the ultimate goal. Rate-based separation processes hold promise as both more environmentally benign as well as less energy intensive when compared to conventional particle separations technologies such as vibrating screens or flotation methods. This approach is based on differences in the kinetic properties of the components of a mixture, such as the velocity of migration or diffusivity. In this portion of the work, two examples of novel rate-based separation devices are demonstrated. The first example involves the study of the dynamics of gravity-driven particles through an array of obstacles. Both discrete element (DEM) simulations and experiments are used to augment the understanding of this device. Dissipative collisions (both between the particles themselves and with the obstacles) give rise to a diffusive motion of particles perpendicular to the flow direction and the differences in diffusion lengths are exploited to separate the particles. The second example employs DEM to analyze a ratchet mechanism where a current of particles can be produced in a direction perpendicular to the energy input. In this setup, a vibrating saw-toothed base is employed to induce different mobility for different types of particles. The effect of operating conditions and design parameters on the separation efficiency are discussed. Keywords: granular flow, particle, mixing, segregation, discrete element method, particle dynamics, tumbler, chute, periodic flow inversion, collisional flow, rate-based separation, ratchet, static separator, dissipative particle dynamics, non-spherical droplet.

Measures Matter: The Local Exposure/Isolation (LEx/Is) Metrics and Relationships Between Local Level Segregation and Breast Cancer Survival

PubMed Central

Bemanian, Amin; Beyer, Kirsten M.M.

2017-01-01

Background The Black to White disparity in breast cancer survival is increasing, and racial residential segregation is a potential driver for this trend. However, study findings have been mixed, and no study has comprehensively compared the effectiveness of different local level segregation metrics in explaining cancer survival. Methods We proposed a set of new local segregation metrics named LEx/Is (Local Exposure and Isolation) and compared our new local isolation metric to two related metrics - the location quotient (LQ) and the index of concentration at extremes (ICE) - across the 102 largest US metropolitan areas. Then, using case data from the Milwaukee, WI metropolitan area, we used proportional hazards models to explore associations between segregation and breast cancer survival. Results Across the 102 metropolitan areas, the new local isolation metric was less skewed than the LQ or ICE. Across all races, Hispanic isolation was associated with poorer all-cause survival, and Hispanic LQ and Hispanic-White ICE were found to be associated with poorer survival for both breast cancer specific and all-cause mortality. For Black patients, Black LQ was associated with lower all-cause mortality and Black local isolation was associated with reduced all-cause and breast cancer specific mortality. ICE was found to suffer from high multicollinearity. Conclusions Local segregation is associated with breast cancer survival, but associations varied based on patient race and metric employed. Impact We highlight how selection of a segregation measure can alter study findings. These relationships need to be validated in other geographic areas. PMID:28325737

Microwave and micronization treatments affect dehulling characteristics and bioactive contents of dry beans (Phaseolus vulgaris L.).

PubMed

Oomah, B Dave; Kotzeva, Lily; Allen, Meghan; Bassinello, Priscila Zaczuk

2014-05-01

Heat pretreatment is considered the first step in grain milling. This study therefore evaluated microwave and micronization heat treatments in improving the dehulling characteristics, phenolic composition and antioxidant and α-amylase activities of bean cultivars from three market classes. Heat treatments improved dehulling characteristics (hull yield, rate coefficient and reduced abrasive hardness index) depending on bean cultivar, whereas treatment effects increased with dehulling time. Micronization increased minor phenolic components (tartaric esters, flavonols and anthocyanins) of all beans but had variable effects on total phenolic content depending on market class. Microwave treatment increased α-amylase inhibitor concentration, activity and potency, which were strongly correlated (r²  = 0.71, P < 0.0001) with the flavonol content of beans. Heat treatment had variable effects on the phenolic composition of bean hulls obtained by abrasive dehulling without significantly altering the antioxidant activity of black and pinto bean hulls. Principal component analysis on 22 constituents analyzed in this study demonstrated the differences in dehulling characteristics and phenolic components of beans and hulls as major factors in segregating the beneficial heat treatment effects. Heat treatment may be useful in developing novel dietary fibers from beans with variable composition and bioactivity with a considerable range of applications as functional food ingredients. © 2013 Society of Chemical Industry.

The failure models of Sn-based solder joints under coupling effects of electromigration and thermal cycling

NASA Astrophysics Data System (ADS)

Ma, Limin; Zuo, Yong; Liu, Sihan; Guo, Fu; Wang, Xitao

2013-01-01

Currently, the main concerns of Pb-free solder joints are focusing on electromigration (EM) and thermomechanical fatigue (TMF) problems. Many models have been established to understand the failure mechanisms of the joint under such single test conditions. Based on the fact that almost all microelectronic devices serve in combination conditions of fluctuated temperature and electric current stressing, the coupling effects of EM and TMF on evolution of microstructure and resistance of solder joint had been investigated. The failure models of binary SnBi alloy and ternary SnAgCu (SAC) solder under the coupling stressing were divided into four and three different stages, respectively. The failure mechanisms were dominant by the relationship of phase segregation, polarity effect, phase coarsening, and the coefficient of thermal expansion mismatch. Cracks tend to form and propagate along the interface between intermetallic compound layers and solder matrix in SAC solder. However, grain boundary was considered as the nucleation sites for microcracks in SnBi solder. High current density alleviates the deterioration of solder at the beginning stage of coupling stressing through Joule heating effect. An abrupt jump of resistance could be observed before the failure of the joint. The failure molds were determined by interactions of EM behaviors and TMF damages.

Male group size, female distribution and changes in sexual segregation by Roosevelt elk

PubMed Central

Peterson, Leah M.

2017-01-01

Sexual segregation, or the differential use of space by males and females, is hypothesized to be a function of body size dimorphism. Sexual segregation can also manifest at small (social segregation) and large (habitat segregation) spatial scales for a variety of reasons. Furthermore, the connection between small- and large-scale sexual segregation has rarely been addressed. We studied a population of Roosevelt elk (Cervus elaphus roosevelti) across 21 years in north coastal California, USA, to assess small- and large-scale sexual segregation in winter. We hypothesized that male group size would associate with small-scale segregation and that a change in female distribution would associate with large-scale segregation. Variation in forage biomass might also be coupled to small and large-scale sexual segregation. Our findings were consistent with male group size associating with small-scale segregation and a change in female distribution associating with large-scale segregation. Females appeared to avoid large groups comprised of socially dominant males. Males appeared to occupy a habitat vacated by females because of a wider forage niche, greater tolerance to lethal risks, and, perhaps, to reduce encounters with other elk. Sexual segregation at both spatial scales was a poor predictor of forage biomass. Size dimorphism was coupled to change in sexual segregation at small and large spatial scales. Small scale segregation can seemingly manifest when all forage habitat is occupied by females and large scale segregation might happen when some forage habitat is not occupied by females. PMID:29121076

Compositional segregation and electrical properties characterization of [001]- and [011]-oriented co-growth Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal

NASA Astrophysics Data System (ADS)

Song, Kexin; Li, Zhenrong; Guo, Haisheng; Xu, Zhuo; Fan, Shiji

2018-04-01

A Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 relaxor ferroelectric single crystal boule of 3 in. diameter was grown using [001]- and [011]-oriented co-growth crystals as seeds by the modified Bridgman method. The as-grown crystal boule was divided into two growth regions [001] and [011]. The composition and the electrical properties of samples of the two regions were characterized in detail along the growth direction in the whole crystal boule. The PT content of [001]-grown samples increased from 27.7 to 36.8 mol. % along the growth direction, especially they are averagely higher about 0.7 mol. % than those of [011]-grown samples at the same growth position. The PMN content of [001]-grown samples decreased from 43.0 to 34.8 mol. %, which is lower than that of the corresponding [011]-grown samples. The compositional segregation behavior along [001] and [011] growth directions was discussed based on the crystal growth theories. Variations in the rhombohedral to tetragonal phase transition temperature (TRT), the piezoelectric properties, the coercive electric field and the remnant polarization of [001] samples were discussed according to changes in compositional segregation and crystal anisotropy. Under the exact same growth conditions, the [011]-grown crystal has a larger composition segregation effect than that of the [001]-grown crystal. This result provides a positive effect on analysing the nature and reducing the effect of compositional segregation.

Nonequilibrium processes of segregation and diffusion in metal-polymer tribosystems

NASA Astrophysics Data System (ADS)

Sidashov, A. V.; Kolesnikov, I. V.

2017-12-01

The article presents the results of exchange-diffusion processes between chemical elements in metal-polymer tribosystems (between a metal wheel of a rolling stock and a composite polymer brake shoe). The effect of the segregation processes on the strength characteristics of the working surface of a tribosystem is estimated by quantum chemical calculations, Auger and X-ray photoelectron spectroscopies.

Equal Educational Opportunity in the Sacramento City Unified School District; A Report to the Board of Education, The Sacramento City Unified School District.

ERIC Educational Resources Information Center

Sacramento City Unified School District, CA. Citizens Advisory Committee on Equal Educational Opportunity.

A 1965 report presents the findings of a citizens committee on racial tension and school segregation in Sacramento, California. Discussed are defacto segregation and its causes and effects, equal educational opportunity, the neighborhood school concept, and intergroup relations. A series of recommendations for improvement are included. (NH)

Vertical Phase Segregation Induced by Dipolar Interactions in Planar Polymer Brushes

DOE PAGES

Mahalik, Jyoti P.; Sumpter, Bobby G.; Kumar, Rajeev

2016-09-13

In this paper, we present a generalized theory for studying structural properties of a planar dipolar polymer brush immersed in a polar solvent. We show that an explicit treatment of the dipolar interactions yields a macroscopic concentration dependent effective “chi” (the Flory–Huggins-like interaction) parameter. Furthermore, it is shown that the concentration dependent chi parameter promotes phase segregation in polymer solutions and brushes so that the polymer-poor phase consists of a finite/nonzero polymer concentration. Such a destabilization of the homogeneous phase by the dipolar interactions appears as vertical phase segregation in a planar polymer brush. In a vertically phase segregated polymermore » brush, the polymer-rich phase near the grafting surface coexists with the polymer-poor phase at the other end. Predictions of the theory are directly compared with prior reported experimental results for dipolar polymers in polar solvents. Excellent agreements with the experimental results are found, hinting that the dipolar interactions play a significant role in vertical phase segregation of planar polymer brushes. We also compare our field theoretical approach with the two-state and other models invoking ad hoc concentration dependence of the chi parameter. Interplay between the short-ranged excluded volume interactions and long-ranged dipolar interactions is shown to play an important role in affecting the vertical phase separation. Finally, effects of mismatch between the dipole moments of the polymer segments and the solvent molecules are investigated in detail.« less

Mechanisms and genetic control of interspecific crossing barriers in Lycopersicon. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mutschler, M.A.

Deficiency of Lycopersicon esculentum allele (E) was observed from the RFLP and isozyme data of the F{sub 2} populations derived from the cross L. esculentum x L. pennellii. The genome composition of the F{sub 2} populations containing L. pennellii cytoplasm (F{sub 2}{sup Lp4}) has a lower proportion of the homozygous L. pennellii (PP) genotypes and a higher proportion of heterozygote (EP) genotypes than that of the F{sub 2} populations containing L. esculentum cytoplasm (F{sub 2}{sup Le}). A lower proportion of the L. pennellii alleles (P) was also observed in F{sub 2}{sup Lp4} as compared to F{sub 2}{sup Le} when eachmore » marker locus was tested individually. To study the effects of gametic and zygotic selection on segregation distortion, the expected patterns of segregation at a marker locus were derived for ten selection models with gametic or zygotic selection at a hidden linked locus. Segregation distortion caused by four of the selection models studied can be uniquely identified by the patterns of significance expected for the likelihood ratio tests at the marker loci. Comparison of the chromosomal regions associated with specific selection models across populations (of this experiment and previous publications) indicated that the segregation distortion observed in chromosome 10 is associated with zygotic selection affecting both arms of the chromosome, and cytoplasm substitution has the effect of decreasing the segregation distortion on the long arm of the chromosome.« less

Integration of basic sciences and clinical sciences in oral radiology education for dental students.

PubMed

Baghdady, Mariam T; Carnahan, Heather; Lam, Ernest W N; Woods, Nicole N

2013-06-01

Educational research suggests that cognitive processing in diagnostic radiology requires a solid foundation in the basic sciences and knowledge of the radiological changes associated with disease. Although it is generally assumed that dental students must acquire both sets of knowledge, little is known about the most effective way to teach them. Currently, the basic and clinical sciences are taught separately. This study was conducted to compare the diagnostic accuracy of students when taught basic sciences segregated or integrated with clinical features. Predoctoral dental students (n=51) were taught four confusable intrabony abnormalities using basic science descriptions integrated with the radiographic features or taught segregated from the radiographic features. The students were tested with diagnostic images, and memory tests were performed immediately after learning and one week later. On immediate and delayed testing, participants in the integrated basic science group outperformed those from the segregated group. A main effect of learning condition was found to be significant (p<0.05). The results of this study support the critical role of integrating biomedical knowledge in diagnostic radiology and shows that teaching basic sciences integrated with clinical features produces higher diagnostic accuracy in novices than teaching basic sciences segregated from clinical features.

Segregation of biomedical waste in an South Indian tertiary care hospital

PubMed Central

Sengodan, Vetrivel Chezian

2014-01-01

Introduction: Hospital wastes pose significant public health hazard if not properly managed. Hence, it is necessary to develop and adopt optimal waste management systems in the hospitals. Material and method: Biomedical waste generated in Coimbatore Medical College Hospital was color coded (blue, yellow, and red) and the data was analyzed retrospectively on a daily basis for 3 years (January 2010-December 2012). Results: Effective segregation protocols significantly reduced biomedical waste generated from 2011 to 2012. While biomedical waste of red category was significantly higher (>50%), the category yellow was the least. Per unit (per bed per day) total biomedical waste generated was 68.5, 68.8, and 61.3 grams in 2010, 2011, and 2012, respectively. Discussion: Segregation of biomedical waste at the source of generation is the first and essential step in biomedical waste management. Continuous training, fixing the responsibility on the nursing persons, and constant supervision are the key criteria's in implementing biomedical waste segregation process, which can significantly reduce per unit biomedical waste generated. Conclusion: We highly recommend all hospitals to adopt our protocol and effectively implement them to reduce generation of biomedical waste. PMID:25097419

Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

PubMed Central

Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

2016-01-01

Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

Surface segregation on Fe3%Si0.04%VC(100) single crystal surfaces

NASA Astrophysics Data System (ADS)

Uebing, C.; Viefhaus, H.

1990-10-01

Surface segregation phenomena on (100) oriented single crystal surfaces of the ferritic Fe-3%Si-0.04%V-C alloy were investigated by AES and LEED. At temperatures below 635 °C vanadium and carbon cosegregation is observed after prolonged heating. At thermodynamic equilibrium the substrate surface is saturated with the binary surface compound VC. The two-dimensional VC is epitaxially arranged on the substrate surface as indicated by LEED investigations. Its structure corresponds to the (100) plane of the three-dimensional VC with rocksalt structure. Sharp above 635 °C the surface compound VC is dissolved into the bulk. At higher temperatures the substrate surface is covered with segregated silicon forming a c(2 × 2) structure. This surface phase transition is reversible. Because of the low concentration and slow diffusion of vanadium, non-equilibrium surface states are formed as intermediates upon segregation of silicon and carbon. Below 500 °C a disordered graphite layer with a characteristical asymmetrical C Auger peak is observed on the substrate surface. Above 500 °C carbon segregation leads to the formation of an ordered c(2 × 2) structure with a symmetrical C Auger peak being characteristic for carbidic or atomically adsorbed species. At increasing temperatures silicon segregation takes place leading to a c(2 × 2) structure. Between silicon and carbon site competition is effective.

Race and Space in the 1990s: Changes in the Geographic Scale of Racial Residential Segregation, 1990-2000

PubMed Central

Reardon, Sean F.; Farrell, Chad R.; Matthews, Stephen A.; O'Sullivan, David; Bischoff, Kendra; Firebaugh, Glenn

2014-01-01

We use newly developed methods of measuring spatial segregation across a range of spatial scales to assess changes in racial residential segregation patterns in the 100 largest U.S. metropolitan areas from 1990 to 2000. Our results point to three notable trends in segregation from 1990 to 2000: 1) Hispanic-white and Asian-white segregation levels increased at both micro- and macro-scales; 2) black-white segregation declined at a micro-scale, but was unchanged at a macro-scale; and 3) for all three racial groups and for almost all metropolitan areas, macro-scale segregation accounted for more of the total metropolitan area segregation in 2000 than in 1990. Our examination of the variation in these trends among the metropolitan areas suggests that Hispanic-white and Asian-white segregation changes have been driven largely by increases in macro-scale segregation resulting from the rapid growth of the Hispanic and Asian populations in central cities. The changes in black-white segregation, in contrast, appear to be driven by the continuation of a 30-year trend in declining micro-segregation, coupled with persistent and largely stable patterns of macro-segregation. PMID:19569292

Experimental determination of Pb partitioning between sulfide melt and basalt melt as a function of P, T and X

NASA Astrophysics Data System (ADS)

Hart, Stanley R.; Gaetani, Glenn A.

2016-07-01

We have measured the partition coefficient of Pb (KdPb) between FeS melt and basalt melt at temperatures of 1250-1523 °C, pressures of 1.0-3.5 GPa and oxygen fugacities at iron-wustite and wustite-magnetite. The total observed range of KdPb is 4.0-66.6, with a strong negative dependence on pressure and a strong negative dependence on FeO of the silicate melt (Fe+2 only). The FeO control was constrained over a wide range of FeO (4.2-39.5%). We found that the effect of oxygen fugacity can be subsumed under the FeO control parameter. Prior work has established the lack of a significant effect of temperature (Kiseeva and Wood, 2015; Li and Audétat, 2015). Our data are parameterized as: KdPb = 4.8 + (512 - 119*P in GPa)*(1/FeO - 0.021). We also measured a single value of KdPb between clinopyroxene and basalt melt at 2.0 GPa of 0.020 ± 0.001. This experimental data supports the ;natural; partitioning of Pb measured on sulfide globules in MORB (Patten et al., 2013), but not the low KdPb of ∼3 inferred from sulfides in abyssal peridotites by Warren and Shirey (2012). It also quantitatively affirms the modeling of Hart and Gaetani (2006) with respect to using sulfide to buffer the canonical Nd/Pb ratio for MORB and OIB (Hofmann, 2003). For the low FeO and pressure of segregation typical of MORB, KdPb ∼ 45, and the Nd/Pb ratio of erupted basalts will be the same as the Nd/Pb ratio of the mantle source. The remaining puzzle is why MORB and OIB have the same Nd/Pb when they clearly have different FeO and pressure of melt segregation.

Thermal Properties of SiOC Glasses and Glass Ceramics at Elevated Temperatures

PubMed Central

Stabler, Christina; Reitz, Andreas; Stein, Peter; Albert, Barbara; Riedel, Ralf

2018-01-01

In the present study, the effect of the chemical and phase composition on the thermal properties of silicon oxide carbides (SiOC) has been investigated. Dense monolithic SiOC materials with various carbon contents were prepared and characterized with respect to their thermal expansion, as well as thermal conductivity. SiOC glass has been shown to exhibit low thermal expansion (e.g., ca. 3.2 × 10−6 K−1 for a SiOC sample free of segregated carbon) and thermal conductivity (ca. 1.5 W/(m∙K)). Furthermore, it has been observed that the phase separation, which typically occurs in SiOC exposed to temperatures beyond 1000–1200 °C, leads to a decrease of the thermal expansion (i.e., to 1.83 × 10−6 K−1 for the sample above); whereas the thermal conductivity increases upon phase separation (i.e., to ca. 1.7 W/(m∙K) for the sample mentioned above). Upon adjusting the amount of segregated carbon content in SiOC, its thermal expansion can be tuned; thus, SiOC glass ceramics with carbon contents larger than 10–15 vol % exhibit similar coefficients of thermal expansion to that of the SiOC glass. Increasing the carbon and SiC content in the studied SiOC glass ceramics leads to an increase in their thermal conductivity: SiOC with relatively large carbon and silicon carbides (SiC) volume fractions (i.e., 12–15 and 20–30 vol %, respectively) were shown to possess thermal conductivities in the range from 1.8 to 2.7 W/(m∙K). PMID:29439441

Field Evaluation of Temperature Differential in HMA Mixtures

DOT National Transportation Integrated Search

2012-05-15

Segregation is a common occurrence in hot mix asphalt (HMA) construction. The two types of : segregation encountered are gradation segregation and thermal segregation. This investigation report : involves mainly thermal segregation, which occurs when...

Progressive retinal atrophy in the Border Collie: a new XLPRA.

PubMed

Vilboux, Thierry; Chaudieu, Gilles; Jeannin, Patricia; Delattre, Delphine; Hedan, Benoit; Bourgain, Catherine; Queney, Guillaume; Galibert, Francis; Thomas, Anne; André, Catherine

2008-03-03

Several forms of progressive retinal atrophy (PRA) segregate in more than 100 breeds of dog with each PRA segregating in one or a few breeds. This breed specificity may be accounted for by founder effects and genetic drift, which have reduced the genetic heterogeneity of each breed, thereby facilitating the identification of causal mutations. We report here a new form of PRA segregating in the Border Collie breed. The clinical signs, including the loss of night vision and a progressive loss of day vision, resulting in complete blindness, occur at the age of three to four years and may be detected earlier through systematic ocular fundus examination and electroretinography (ERG). Ophthalmic examinations performed on 487 dogs showed that affected dogs present a classical form of PRA. Of those, 274 have been sampled for DNA extraction and 87 could be connected through a large pedigree. Segregation analysis suggested an X-linked mode of transmission; therefore both XLPRA1 and XLPRA2 mutations were excluded through the genetic tests. Having excluded these mutations, we suggest that this PRA segregating in Border Collie is a new XLPRA (XLPRA3) and propose it as a potential model for the homologous human disease, X-Linked Retinitis Pigmentosa.

Homogenizing Advanced Alloys: Thermodynamic and Kinetic Simulations Followed by Experimental Results

NASA Astrophysics Data System (ADS)

Jablonski, Paul D.; Hawk, Jeffrey A.

2017-01-01

Segregation of solute elements occurs in nearly all metal alloys during solidification. The resultant elemental partitioning can severely degrade as-cast material properties and lead to difficulties during post-processing (e.g., hot shorts and incipient melting). Many cast articles are subjected to a homogenization heat treatment in order to minimize segregation and improve their performance. Traditionally, homogenization heat treatments are based upon past practice or time-consuming trial and error experiments. Through the use of thermodynamic and kinetic modeling software, NETL has designed a systematic method to optimize homogenization heat treatments. Use of the method allows engineers and researchers to homogenize casting chemistries to levels appropriate for a given application. The method also allows for the adjustment of heat treatment schedules to fit limitations on in-house equipment (capability, reliability, etc.) while maintaining clear numeric targets for segregation reduction. In this approach, the Scheil module within Thermo-Calc is used to predict the as-cast segregation present within an alloy, and then diffusion controlled transformations is used to model homogenization kinetics as a function of time and temperature. Examples of computationally designed heat treatments and verification of their effects on segregation and properties of real castings are presented.

Molecular Mobility in Phase Segregated Bottlebrush Block Copolymer Melts

NASA Astrophysics Data System (ADS)

Yavitt, Benjamin; Gai, Yue; Song, Dongpo; Winter, H. Henning; Watkins, James

We investigate the linear viscoelastic behavior of poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) brush block copolymer (BBCP) materials over a range of vol. fractions and with side chain lengths below the entanglement molecular weights. The high chain mobility of the brush architecture results in rapid micro-phase segregation of the brush copolymer segments, which occurs during thermal annealing at mild temperatures. Master curves of the dynamic moduli were obtained by time-temperature superposition. The reduced degree of chain entanglements leads to a unique liquid-like rheology similar to that of bottlebrush homopolymers, even in the phase segregated state. We also explore the alignment of phase segregated domains at exceptionally low strain amplitudes (γ = 0.01) and mild processing temperatures using small angle X-ray scattering (SAXS). Domain orientation occurred readily at strains within the linear viscoelastic regime without noticeable effect on the moduli. This interplay of high molecular mobility and rapid phase segregation that are exhibited simultaneously in BBCPs is in contrast to the behavior of conventional linear block copolymer (LBCP) analogs and opens up new possibilities for processing BBCP materials for a wide range of nanotechnology applications. NSF Center for Hierarchical Manufacturing at the University of Massachusetts, Amherst (CMMI-1025020).

Multiscale simulation of xenon diffusion and grain boundary segregation in UO₂

DOE PAGES

Andersson, David A.; Tonks, Michael R.; Casillas, Luis; ...

2015-07-01

In light water reactor fuel, gaseous fission products segregate to grain boundaries, resulting in the nucleation and growth of large intergranular fission gas bubbles. The segregation rate is controlled by diffusion of fission gas atoms through the grains and interaction with the boundaries. Based on the mechanisms established from earlier density functional theory (DFT) and empirical potential calculations, diffusion models for xenon (Xe), uranium (U) vacancies and U interstitials in UO₂ have been derived for both intrinsic (no irradiation) and irradiation conditions. Segregation of Xe to grain boundaries is described by combining the bulk diffusion model with a model formore » the interaction between Xe atoms and three different grain boundaries in UO₂ (Σ5 tilt, Σ5 twist and a high angle random boundary), as derived from atomistic calculations. The present model does not attempt to capture nucleation or growth of fission gas bubbles at the grain boundaries. The point defect and Xe diffusion and segregation models are implemented in the MARMOT phase field code, which is used to calculate effective Xe and U diffusivities as well as to simulate Xe redistribution for a few simple microstructures.« less

Segregating photoelastic particles in free-surface granular flows

NASA Astrophysics Data System (ADS)

Thomas, Amalia; Vriend, Nathalie; Environmental; Industrial Fluid Dynamics Team

2017-11-01

We present results from a novel experimental set-up creating 2D avalanches of photoelastic discs. Two distinct hoppers supply either monodisperse or bidisperse particles at adjustable flow-rates into a 2 meter long, narrow acrylic chute inclined at 20°. For 20-40 seconds the avalanche maintains a steady-state that accelerates and thins downstream. The chute basal roughness is variable, allowing for different flow profiles. Using a set of polarizers and a high-speed camera, we visualize and quantify the forces due to dynamic interactions between the discs using photoelastic theory. Velocity and density profiles are derived from particle tracking at different distances from the discharge point and are coarse-grained to obtain continuous fields. With the access to both force information and dynamical properties via particle-tracking, we can experimentally validate existing mu(I) and non-local rheologies. As an extension, we probe the effect of granular segregation in bimodal mixtures by using the two separate inflow hoppers. We derive the state of segregation along the avalanche channel and measure the segregation velocities of each species. This provides insight in, and a unique validation of, the fundamental physical processes that drive segregation in avalanching geometries.

Maintaining the ties that bind: the role of an intermediate visual memory store in the persistence of awareness.

PubMed

Ferber, Susanne; Emrich, Stephen M

2007-03-01

Segregation and feature binding are essential to the perception and awareness of objects in a visual scene. When a fragmented line-drawing of an object moves relative to a background of randomly oriented lines, the previously hidden object is segregated from the background and consequently enters awareness. Interestingly, in such shape-from-motion displays, the percept of the object persists briefly when the motion stops, suggesting that the segregated and bound representation of the object is maintained in awareness. Here, we tested whether this persistence effect is mediated by capacity-limited working-memory processes, or by the amount of object-related information available. The experiments demonstrate that persistence is affected mainly by the proportion of object information available and is independent of working-memory limits. We suggest that this persistence effect can be seen as evidence for an intermediate, form-based memory store mediating between sensory and working memory.

Heat flow control and segregation in directional solidification: Development of an experimental and theoretical basis for Bridgman-type growth experiments in a microgravity environment

NASA Technical Reports Server (NTRS)

Witt, A. F.

1986-01-01

Within the framework of the proposed research, emphasis was placed on application of magnetic fields to semiconductor growth systems. It was found that magnetic fields up to 3 kGauss do not affect the growth behavior nor the macro-segregation behavior in the system Ge(Ga). Applied fields are found to significantlty alter the radial dopant distribution, which is attributed to alterations in the spatial orientation of convective cells. Increasing the magnetic field to 30 kGauss is found to have a fundamental effect on dopant segregation. Emphasis is also placed on the potential of KC-135 flights for preliminary studies on the effects of reduced gravity environments on the wetting behavior of semiconductor systems in growth configuration. The limited number of experiments conducted does not allow any conclusions on the merits of KC-135 flights for semiconductor processing research.

A hybrid technique for speech segregation and classification using a sophisticated deep neural network

PubMed Central

Nawaz, Tabassam; Mehmood, Zahid; Rashid, Muhammad; Habib, Hafiz Adnan

2018-01-01

Recent research on speech segregation and music fingerprinting has led to improvements in speech segregation and music identification algorithms. Speech and music segregation generally involves the identification of music followed by speech segregation. However, music segregation becomes a challenging task in the presence of noise. This paper proposes a novel method of speech segregation for unlabelled stationary noisy audio signals using the deep belief network (DBN) model. The proposed method successfully segregates a music signal from noisy audio streams. A recurrent neural network (RNN)-based hidden layer segregation model is applied to remove stationary noise. Dictionary-based fisher algorithms are employed for speech classification. The proposed method is tested on three datasets (TIMIT, MIR-1K, and MusicBrainz), and the results indicate the robustness of proposed method for speech segregation. The qualitative and quantitative analysis carried out on three datasets demonstrate the efficiency of the proposed method compared to the state-of-the-art speech segregation and classification-based methods. PMID:29558485

The Effect of Hydrogen Annealing and Sulfur Content on the Oxidation Resistance of PWA 1480

NASA Technical Reports Server (NTRS)

Smialek, James L.

1997-01-01

For many decades the dramatic effect of trace amounts of reactive elements on alumina and chromia scale adhesion has been recognized and widely studied. Although various theories have been used to account for such behavior, the connection between scale adhesion and sulfur segregation was initially reported by Smeggil et al. This study found strong surface segregation of sulfur from very low levels in the bulk which could then be curtailed by the addition of reactive elements. It was assumed that the reactive elements, which are strong sulfide formers, acted by getting sulfur in the bulk thus precluding sulfur segregation and weakening of the oxide-metal bond. Subsequent studies confirmed that adhesion could be produced by reducing the sulfur impurity level, without reactive elements. The understanding of this phenomenon has been applied to modern single crystal superalloys, where the addition of Y, although very effective, is problematic. Also problematic is definition of the level of sulfur that is acceptable and below which no further adhesion benefit is reached. Published works have indicated a broad transition defined by various materials and oxidation tests. The present study describes the oxidation behavior of one superalloy (PWA 1480) as a function of various sulfur contents produced by hydrogen annealing for various temperatures, times, and sample thicknesses. The purpose is to define more precisely a criterion for adhesion based on total sulfur reservoir and segregation potential.

Phase-field-crystal study of solute trapping

NASA Astrophysics Data System (ADS)

Humadi, Harith; Hoyt, Jeffrey J.; Provatas, Nikolas

2013-02-01

In this study we have incorporated two time scales into the phase-field-crystal model of a binary alloy to explore different solute trapping properties as a function of crystal-melt interface velocity. With only diffusive dynamics, we demonstrate that the segregation coefficient, K as a function of velocity for a binary alloy is consistent with the model of Kaplan and Aziz where K approaches unity in the limit of infinite velocity. However, with the introduction of wavelike dynamics in both the density and concentration fields, the trapping follows the kinetics proposed by Sobolev [Phys. Lett. A10.1016/0375-9601(95)00084-G 199, 383 (1995)], where complete trapping occurs at a finite velocity.

Development of a Single-Crystal Fifth-Generation Nickel Superalloy

NASA Astrophysics Data System (ADS)

Petrushin, N. V.; Elyutin, E. S.; Visik, E. M.; Golynets, S. A.

2017-11-01

The chemical and phase compositions of a rhenium-ruthenium-containing fifth-generation VZhM8 nickel superalloy, which is intended for single-crystal turbine blades of an aviation engine, are calculated using computer simulation. VZhM8 alloy <001>, <011>, and <111> single crystals are fabricated. The microstructure, the γ/γ' misfit, the segregation coefficients of alloying elements, the dissolution temperature of the γ' phase, and the solidus and liquidus temperatures of the VZhM8 alloy single crystals in the as-cast state and after heat treatment are studied. The temperature-time dependences of the static elastic modulus, the short-term mechanical properties, and the long-term strength of the alloy single crystals are determined

Development of {110}<001> annealing texture in Al-free and 0.1 %Mn-added 3 %Si-Fe alloy strips containing 95 ppm sulfur

NASA Astrophysics Data System (ADS)

Heo, N. H.; Yoon, G. G.

2010-04-01

The solubility of sulfur is calculated in 0.1 %Mn-added 3 %Si-Fe alloys. The segregation kinetics of sulfur is compared in the alloy containing 95 ppm sulfur, depending on the annealing atmosphere. The effects of pre-annealing and annealing atmosphere on final annealing texture are investigated. Segregation behaviors of sulfur at free surfaces and grain boundaries are compared and, during the selective growth, the importance of the grain boundary concentration of sulfur is emphasized. Finally, a correlation between the development of the annealing texture and segregation kinetics of sulfur in the alloy strip is discussed.

School Choice, Racial Segregation, and Test-Score Gaps: Evidence from North Carolina's Charter School Program

ERIC Educational Resources Information Center

Bifulco, Robert; Ladd, Helen F.

2007-01-01

Using panel data that track individual students from year to year, we examine the effects of charter schools in North Carolina on racial segregation and black-white test score gaps. We find that North Carolina's system of charter schools has increased the racial isolation of both black and white students, and has widened the achievement gap.…

Interface segregation behavior in thermal aged austenitic precipitation strengthened stainless steel.

PubMed

Li, Hui; Song, Hui; Liu, Wenqing; Xia, Shuang; Zhou, Bangxin; Su, Cheng; Ding, Wenyan

2015-12-01

The segregation of various elements at grain boundaries, precipitate/matrix interfaces were analyzed using atom probe tomography in an austenitic precipitation strengthened stainless steel aged at 750 °C for different time. Segregation of P, B and C at all types of interfaces in all the specimens were observed. However, Si segregated at all types of interfaces only in the specimen aged for 16 h. Enrichment of Ti at grain boundaries was evident in the specimen aged for 16 h, while Ti did not segregate at other interfaces. Mo varied considerably among interface types, e.g. from segregated at grain boundaries in the specimens after all the aging time to never segregate at γ'/γ phase interfaces. Cr co-segregated with C at grain boundaries, although carbides still did not nucleate at grain boundaries yet. Despite segregation tendency variations in different interface types, the segregation tendency evolution variation of different elements depending aging time were analyzed among all types of interfaces. Based on the experimental results, the enrichment factors, Gibbs interface excess and segregation free energies of segregated elements were calculated and discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Measures Matter: The Local Exposure/Isolation (LEx/Is) Metrics and Relationships between Local-Level Segregation and Breast Cancer Survival.

PubMed

Bemanian, Amin; Beyer, Kirsten M M

2017-04-01

Background: The Black-to-White disparity in breast cancer survival is increasing, and racial residential segregation is a potential driver for this trend. However, study findings have been mixed, and no study has comprehensively compared the effectiveness of different local-level segregation metrics in explaining cancer survival. Methods: We proposed a set of new local segregation metrics named local exposure and isolation (LEx/Is) and compared our new local isolation metric with two related metrics, the location quotient (LQ) and the index of concentration at extremes (ICE), across the 102 largest U.S. metropolitan areas. Then, using case data from the Milwaukee, WI, metropolitan area, we used proportional hazards models to explore associations between segregation and breast cancer survival. Results: Across the 102 metropolitan areas, the new local isolation metric was less skewed than the LQ or ICE. Across all races, Hispanic isolation was associated with poorer all-cause survival, and Hispanic LQ and Hispanic-White ICE were found to be associated with poorer survival for both breast cancer-specific and all-cause mortality. For Black patients, Black LQ was associated with lower all-cause mortality and Black local isolation was associated with reduced all-cause and breast cancer-specific mortality. ICE was found to suffer from high multicollinearity. Conclusions: Local segregation is associated with breast cancer survival, but associations varied based on patient race and metric employed. Impact: We highlight how selection of a segregation measure can alter study findings. These relationships need to be validated in other geographic areas. Cancer Epidemiol Biomarkers Prev; 26(4); 516-24. ©2017 AACR See all the articles in this CEBP Focus section, "Geospatial Approaches to Cancer Control and Population Sciences." ©2017 American Association for Cancer Research.

Hydrogen segregation to inclined Σ3 < 110 >twin grain boundaries in nickel

DOE PAGES

O’Brien, Christopher J.; Foiles, Stephen M.

2016-08-04

Low-mobility twin grain boundaries dominate the microstructure of grain boundary-engineered materials and are critical to understanding their plastic deformation behaviour. The presence of solutes, such as hydrogen, has a profound effect on the thermodynamic stability of the grain boundaries. This work examines the case of a Σ3 grain boundary at inclinations from 0° ≤ Φ ≤ 90°. The angle Φ corresponds to the rotation of the Σ3 (1 1 1) < 1 1 0 > (coherent) into the Σ3 (1 1 2) < 1 1 0 > (lateral) twin boundary. To this end, atomistic models of inclined grain boundaries, utilisingmore » empirical potentials, are used to elucidate the finite-temperature boundary structure while grand canonical Monte Carlo models are applied to determine the degree of hydrogen segregation. In order to understand the boundary structure and segregation behaviour of hydrogen, the structural unit description of inclined twin grain boundaries is found to provide insight into explaining the observed variation of excess enthalpy and excess hydrogen concentration on inclination angle, but the explanatory power is limited by how the enthalpy of segregation is affected by hydrogen concentration. At higher concentrations, the grain boundaries undergo a defaceting transition. In order to develop a more complete mesoscale model of the interfacial behaviour, an analytical model of boundary energy and hydrogen segregation that relies on modelling the boundary as arrays of discrete 1/3 < 1 1 1 > disconnections is constructed. Lastly, the complex interaction of boundary reconstruction and concentration-dependent segregation behaviour exhibited by inclined twin grain boundaries limits the range of applicability of such an analytical model and illustrates the fundamental limitations for a structural unit model description of segregation in lower stacking fault energy materials.« less

Human female meiosis revised: new insights into the mechanisms of chromosome segregation and aneuploidies from advanced genomics and time-lapse imaging.

PubMed

Capalbo, Antonio; Hoffmann, Eva R; Cimadomo, Danilo; Ubaldi, Filippo Maria; Rienzi, Laura

2017-11-01

The unbalanced transmission of chromosomes in human gametes and early preimplantation embryos causes aneuploidy, which is a major cause of infertility and pregnancy failure. A baseline of 20% of human oocytes are estimated to be aneuploid and this increases exponentially from 30 to 35 years, reaching on average 80% by 42 years. As a result, reproductive senescence in human females is predominantly determined by the accelerated decline in genetic quality of oocytes from 30 years of age. Understanding mechanisms of chromosome segregation and aneuploidies in the female germline is a crucial step towards the development of new diagnostic approaches and, possibly, for the development of therapeutic targets and molecules. Here, we have reviewed emerging mechanisms that may drive human aneuploidy, in particular the maternal age effect. We conducted a systematic search in PubMed Central of the primary literature from 1990 through 2016 following the PRISMA guidelines, using MeSH terms related to human aneuploidy. For model organism research, we conducted a literature review based on references in human oocytes manuscripts and general reviews related to chromosome segregation in meiosis and mitosis. Advances in genomic and imaging technologies are allowing unprecedented insight into chromosome segregation in human oocytes. This includes the identification of a novel chromosome segregation error, termed reverse segregation, as well as sister kinetochore configurations that were not predicted based on murine models. Elucidation of mechanisms that result in errors in chromosome segregation in meiosis may lead to therapeutic developments that could improve reproductive outcomes by reducing aneuploidy. © The Author 2017. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com

The Effect of School Quality on Black-White Health Differences: Evidence From Segregated Southern Schools

PubMed Central

Frisvold, David; Golberstein, Ezra

2013-01-01

This study assesses the effect of black-white differences in school quality on black-white differences in health in later life resulting from the racial convergence in school quality for cohorts born between 1910 and 1950 in southern states with segregated schools. Using data from the 1984 through 2007 National Health Interview Surveys linked to race-specific data on school quality, we find that reductions in the black-white gap in school quality led to modest reductions in the black-white gap in disability. PMID:23839102

49 CFR 176.80 - Applicability.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Segregation Requirements § 176.80 Applicability. (a) This subpart sets forth segregation requirements in addition to any segregation requirements set forth elsewhere in this subchapter. (b) Hazardous materials in... segregation requirements of this subpart and any additional segregation specified in this subchapter for...

49 CFR 176.80 - Applicability.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Segregation Requirements § 176.80 Applicability. (a) This subpart sets forth segregation requirements in addition to any segregation requirements set forth elsewhere in this subchapter. (b) Hazardous materials in... segregation requirements of this subpart and any additional segregation specified in this subchapter for...

The New Segregation.

ERIC Educational Resources Information Center

Laosa, Luis M.

2001-01-01

This issue reviews national demographic trends in school segregation, summarizing research findings. Though the national debate on school segregation emphasizes blacks and whites, present-day school segregation includes segregation by socioeconomic level, ethnicity, and native language. The research study examined features of the ecology of…

Quantitative determination of zero-gravity effects on electronic materials processing germanium crystal growth with simultaneous interface demarcation experiment MA-060, section 5

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Witt, A. F.; Lichtensteiger, M.; Herman, C. J.

1982-01-01

The crystal growth and segregation characteristics of a melt in a directional solidification configuration under near zero g conditions were investigated. The germanium (doped with gallium) system was selected because it was extensively studied on Earth and because it lends itself to a very detailed macroscopic and microscopic characterization. An extensive study was performed of the germanium crystals grown during the Apollo-Soyuz Test Project mission. It was found that single crystal growth was achieved and that the interface demarcation functioned successfully. On the basis of the results obtained to date, there is no indication that convection driven by thermal or surface tension gradients was present in the melt. The gallium segregation, in the absence of gravity, was found to be fundamentally different in its initial and its subsequent stages from that of the ground based tests. None of the existing theoretical models for growth and segregation can account for the observed segregation behavior in the absence of gravity.

Heroin Mismatch in the Motor City: Addiction, Segregation and the Geography of Opportunity

PubMed Central

Draus, Paul; Roddy, Juliette; Greenwald, Mark

2012-01-01

In this paper, we employ data drawn from economic and ethnographic interviews with Detroit heroin users, as well as other sources, to illustrate the relationship between heroin users’ mobility patterns and urban and suburban environments, especially in terms of drug acquisition and the geography of opportunity. We explore how the “spatial mismatch” (Kain 1968; 1992) between legal work opportunities and central city residents is seemingly reversed in the case of heroin users. We find that while both geographic location and social networks associated with segregation provide central city residents and African Americans with a strategic advantage over white suburbanites in locating and purchasing heroin easily and efficiently, this same segregation effectively focuses the negative externalities of heroin markets in central city neighborhoods. Finally, we consider how the heroin trade reflects and reproduces the segregated post-industrial landscape, and we discuss directions for potential future research on the relationship between ethnic and economic ghettos and regional drug markets. PMID:22679895

Analysis of Helium Segregation on Surfaces of Plasma-Exposed Tungsten

NASA Astrophysics Data System (ADS)

Maroudas, Dimitrios; Hu, Lin; Hammond, Karl; Wirth, Brian

2015-11-01

We report a systematic theoretical and atomic-scale computational study of implanted helium segregation on surfaces of tungsten, which is considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations, including molecular statics to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile helium clusters (of 1-7 He atoms) in the near-surface region are attracted to the surface due to an elastic interaction force. This thermodynamic driving force induces drift fluxes of these mobile clusters toward the surface, facilitating helium segregation. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, at rates much higher than in the bulk material. This cluster dynamics has significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure.

BubR1- and Polo-Coated DNA Tethers Facilitate Poleward Segregation of Acentric Chromatids

PubMed Central

Royou, Anne; Gagou, Mary E.; Karess, Roger; Sullivan, William

2010-01-01

Summary The mechanisms that safeguard cells against chromosomal instability (CIN) are of great interest, as CIN contributes to tumorigenesis. To gain insight into these mechanisms, we studied the behavior of cells entering mitosis with damaged chromosomes. We used the endonuclease I-CreI to generate acentric chromosomes in Drosophila larvae. While I-CreI expression produces acentric chromosomes in the majority of neuronal stem cells, remarkably, it has no effect on adult survival. Our live studies reveal that acentric chromatids segregate efficiently to opposite poles. The acentric chromatid poleward movement is mediated through DNA tethers decorated with BubR1, Polo, INCENP, and Aurora-B. Reduced BubR1 or Polo function results in abnormal segregation of acentric chromatids, a decrease in acentric chromosome tethering, and a great reduction in adult survival. We propose that BubR1 and Polo facilitate the accurate segregation of acentric chromatids by maintaining the integrity of the tethers that connect acentric chromosomes to their centric partners. PMID:20141837

Temporal windows in visual processing: "prestimulus brain state" and "poststimulus phase reset" segregate visual transients on different temporal scales.

PubMed

Wutz, Andreas; Weisz, Nathan; Braun, Christoph; Melcher, David

2014-01-22

Dynamic vision requires both stability of the current perceptual representation and sensitivity to the accumulation of sensory evidence over time. Here we study the electrophysiological signatures of this intricate balance between temporal segregation and integration in vision. Within a forward masking paradigm with short and long stimulus onset asynchronies (SOA), we manipulated the temporal overlap of the visual persistence of two successive transients. Human observers enumerated the items presented in the second target display as a measure of the informational capacity read-out from this partly temporally integrated visual percept. We observed higher β-power immediately before mask display onset in incorrect trials, in which enumeration failed due to stronger integration of mask and target visual information. This effect was timescale specific, distinguishing between segregation and integration of visual transients that were distant in time (long SOA). Conversely, for short SOA trials, mask onset evoked a stronger visual response when mask and targets were correctly segregated in time. Examination of the target-related response profile revealed the importance of an evoked α-phase reset for the segregation of those rapid visual transients. Investigating this precise mapping of the temporal relationships of visual signals onto electrophysiological responses highlights how the stream of visual information is carved up into discrete temporal windows that mediate between segregated and integrated percepts. Fragmenting the stream of visual information provides a means to stabilize perceptual events within one instant in time.

Mechanism of Macrosegregation Formation in Continuous Casting Slab: A Numerical Simulation Study

NASA Astrophysics Data System (ADS)

Jiang, Dongbin; Wang, Weiling; Luo, Sen; Ji, Cheng; Zhu, Miaoyong

2017-12-01

Solidified shell bulging is supposed to be the main reason for slab center segregation, while the influence of thermal shrinkage rarely has been considered. In this article, a thermal shrinkage model coupled with the multiphase solidification model is developed to investigate the effect of the thermal shrinkage, solidification shrinkage, grain sedimentation, and thermal flow on solute transport in the continuous casting slab. In this model, the initial equiaxed grains contract freely with the temperature decrease, while the coherent equiaxed grains and columnar phase move directionally toward the slab surface. The results demonstrate that the center positive segregation accompanied by negative segregation in the periphery zone is mainly caused by thermal shrinkage. During the solidification process, liquid phase first transports toward the slab surface to compensate for thermal shrinkage, which is similar to the case considering solidification shrinkage, and then it moves opposite to the slab center near the solidification end. It is attributed to the sharp decrease of center temperature and the intensive contract of solid phase, which cause the enriched liquid to be squeezed out. With the effect of grain sedimentation and thermal flow, the negative segregation at the external arc side (zone A1) and the positive segregation near the columnar-to-equiaxed transition at the inner arc side (position B1) come into being. Besides, it is found that the grain sedimentation and thermal flow only influence solute transport before equiaxed grains impinge with each other, while the solidification and thermal shrinkage still affect solute redistribution in the later stage.

Sex and the housing: Effects on behavior, cortisol levels and weight in zebrafish.

PubMed

Reolon, Gustavo Kellermann; de Melo, Gabriela Madalena; da Rosa, João Gabriel Dos Santos; Barcellos, Leonardo José Gil; Bonan, Carla Denise

2018-01-15

Studies with zebrafish use acclimatizing periods of at least one week immediately before the experiments. During this time, animals can be housed in sexually segregated conditions (only females or males in the tank) or in mixed-sex conditions (both sexes in the tank). The influence of sex and housing conditions regarding the presence of one or two sexes is largely unknown in zebrafish. Our aim was to evaluate the influence that sex and housing regarding the sex of animals had in the open tank task, in the inhibitory avoidance memory test, in cortisol levels and weight in zebrafish. Four groups of animals were used: 1) segregated housed females (only females were kept in the tank); 2) segregated housed males (only males were kept in the tank); 3) mixed-sex housed females (only females were analyzed from a tank containing 50% ratio of each sex); 4) mixed-sex housed males (only males were analyzed from a tank containing 50% ratio of each sex). Males showed higher total distance travelled and mean speed when compared to females. In the inhibitory avoidance memory, sexually segregated animals had higher latencies than their mixed-sex counterparts in the 1day test and sexually segregated females presented a memory that persisted longer and was able to be reinstated. Whole-body cortisol levels were higher in mixed-sex animals while weight was lower in these fish. To the best of our knowledge, this is the first time that effects of sex and housing regarding sex were investigated in behavior and physiology of zebrafish. Copyright © 2017 Elsevier B.V. All rights reserved.

Superresolution Imaging of Ribosomes and RNA Polymerase in Live Escherichia coli Cells

PubMed Central

Bakshi, Somenath; Siryaporn, Albert; Goulian, Mark; Weisshaar, James C.

2012-01-01

Summary Quantitative spatial distributions of ribosomes (S2-YFP) and RNA polymerase (β′-yGFP) in live E. coli are measured by superresolution fluorescence microscopy. In moderate growth conditions, Nucleoid-ribosome segregation is strong, and RNAP localizes to the nucleoid lobes. The mean copy numbers per cell are 4600 RNAPs and 55,000 ribosomes. Only 10–15% of the ribosomes lie within the densest part of the nucleoid lobes, and at most 4% of the RNAPs lie in the two ribosome-rich endcaps. The predominant observed diffusion coefficient of ribosomes is Dribo = 0.04 μm2/s, attributed to free mRNA being translated by one or more 70S ribosomes. We find no clear evidence of sub-diffusion, as would arise from tethering of ribosomes. The degree of DNA-ribosome segregation strongly suggests that in E. coli most translation occurs on free mRNA transcripts that have diffused into the ribosome-rich regions. Both RNAP and ribosome radial distributions extend to the cytoplasmic membrane, consistent with the transertion hypothesis. However, few if any RNAP copies lie near the membrane of the endcaps. This suggests that if transertion occurs, it exerts a direct radially expanding force on the nucleoid, but not a direct axially expanding force. PMID:22624875

Summer habitat selection by Dall’s sheep in Wrangell-St. Elias National Park and Preserve, Alaska

USGS Publications Warehouse

Roffler, Gretchen H.; Adams, Layne G.; Hebblewhite, Mark

2017-01-01

Sexual segregation occurs frequently in sexually dimorphic species, and it may be influenced by differential habitat requirements between sexes or by social or evolutionary mechanisms that maintain separation of sexes regardless of habitat selection. Understanding the degree of sex-specific habitat specialization is important for management of wildlife populations and the design of monitoring and research programs. Using mid-summer aerial survey data for Dall’s sheep (Ovis dalli dalli) in southern Alaska during 1983–2011, we assessed differences in summer habitat selection by sex and reproductive status at the landscape scale in Wrangell-St. Elias National Park and Preserve (WRST). Males and females were highly segregated socially, as were females with and without young. Resource selection function (RSF) models containing rugged terrain, intermediate values of the normalized difference vegetation index (NDVI), and open landcover types best explained resource selection by each sex, female reproductive classes, and all sheep combined. For male and all female models, most coefficients were similar, suggesting little difference in summer habitat selection between sexes at the landscape scale. A combined RSF model therefore may be used to predict the relative probability of resource selection by Dall’s sheep in WRST regardless of sex or reproductive status.

Overcoming Triple Segregation

ERIC Educational Resources Information Center

Gandara, Patricia

2010-01-01

Latinos are, after whites, the most segregated student group in the United States, and their segregation is closely tied to poor academic outcomes. Latinos experience a triple segregation: by race/ethnicity, poverty, and language. Racial segregation perpetuates negative stereotypes, reduces the likelihood of a strong teaching staff, and is often…

The Effects of the Determinants of Women's Movement Into and Out of Male-dominated Occupations on Occupational Sex Segregation.

ERIC Educational Resources Information Center

Sheridan, Jennifer T.

Although occupational sex segregation has decreased over the last 25 years, it is still a major social concern primarily because of the role it plays in perpetuating the gender wage gap. This paper uses data from the Wisconsin Longitudinal Study, a study that followed a random sample of 10,317 high school graduates, to assess the determinants of…

Fighting Segregation in Special Needs Education in the Netherlands: The Effects of Different Funding Models

ERIC Educational Resources Information Center

Pijl, Sip Jan

2016-01-01

In the past few decades, the number of students attending segregated special schools in the Netherlands has risen considerably. In 1975, 2.2% of all students between 4 and 11 years old attended a special school, and this percentage almost doubled to 4.3% over the next 20 years. In order to stop further growth, two new education policies came into…

Long-range effect of ion irradiation on Cu surface segregation in a Cu sbnd Ni system

NASA Astrophysics Data System (ADS)

Zhang, Li; Tang, Guangze; Ma, Xinxin; Russell, F. Michael; Cao, Xingzhong; Wang, Baoyi; Zhang, Peng

2011-05-01

Ni films were deposited on one side of single crystal Cu substrate discs of 1.0 and 1.5 mm thickness. These discs were irradiated on the Cu side with argon ions. Evidence for enhanced Cu segregation at the Ni surface was found for both thicknesses. This effect decreased with increasing distance between the diffusion zone and the irradiated surface. Slow positron annihilation results indicate lower vacancy-like defects at the subsurface layer after Ar irradiation on the other surface of Cu disks. Such long-range effect is here interpreted on the basis of a particular type of mobile discrete breather called quodon.

Diffusion induced atomic islands on the surface of Ni/Cu nanolayers

NASA Astrophysics Data System (ADS)

Takáts, Viktor; Csik, Attila; Hakl, József; Vad, Kálmán

2018-05-01

Surface islands formed by grain-boundary diffusion has been studied in Ni/Cu nanolayers by in-situ low energy ion scattering spectroscopy, X-ray photoelectron spectroscopy, scanning probe microscopy and ex-situ depth profiling based on ion sputtering. In this paper a new experimental approach of measurement of grain-boundary diffusion coefficients is presented. Appearing time of copper atoms diffused through a few nanometer thick nickel layer has been detected by low energy ion scattering spectroscopy with high sensitivity. The grain-boundary diffusion coefficient can be directly calculated from this appearing time without using segregation factors in calculations. The temperature range of 423-463 K insures the pure C-type diffusion kinetic regime. The most important result is that surface coverage of Ni layer by Cu atoms reaches a maximum during annealing and stays constant if the annealing procedure is continued. Scanning probe microscopy measurements show a Volmer-Weber type layer growth of Cu layer on the Ni surface in the form of Cu atomic islands. Depth distribution of Cu in Ni layer has been determined by depth profile analysis.

High Spectral Resolution Lidar and MPLNET Micro Pulse Lidar Aerosol Optical Property Retrieval Intercomparison During the 2012 7-SEAS Field Campaign at Singapore

NASA Technical Reports Server (NTRS)

Lolli, Simone; Welton, Ellsworth J.; Campbell, James R.; Eloranta, Edwin; Holben, Brent N.; Chew, Boon Ning; Salinas, Santo V.

2014-01-01

From August 2012 to February 2013 a High Resolution Spectral Lidar (HSRL; 532 nm) was deployed at that National University of Singapore near a NASA Micro Pulse Lidar NETwork (MPLNET; 527 nm) site. A primary objective of the MPLNET lidar project is the production and dissemination of reliable Level 1 measurements and Level 2 retrieval products. This paper characterizes and quantifies error in Level 2 aerosol optical property retrievals conducted through inversion techniques that derive backscattering and extinction coefficients from MPLNET elastic single-wavelength datasets. MPLNET Level 2 retrievals for aerosol optical depth and extinction/backscatter coefficient profiles are compared with corresponding HSRL datasets, for which the instrument collects direct measurements of each using a unique optical configuration that segregates aerosol and cloud backscattered signal from molecular signal. The intercomparison is performed, and error matrices reported, for lower (0-5km) and the upper (>5km) troposphere, respectively, to distinguish uncertainties observed within and above the MPLNET instrument optical overlap regime.

The Role of Residential Segregation in Contemporary School Segregation

ERIC Educational Resources Information Center

Frankenberg, Erica

2013-01-01

Inaction to address housing segregation in metropolitan areas has resulted in persistently high levels of residential segregation. As the Supreme Court has recently limited school districts' voluntary integration efforts, this article considers the role of residential segregation in maintaining racially isolated schools, namely what is known about…

41 CFR 109-1.5106 - Segregation of personal property.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false Segregation of personal...-INTRODUCTION 1.51-Personal Property Management Standards and Practices § 109-1.5106 Segregation of personal...) The segregation of the property would materially hinder the progress of the work (i.e., segregation is...

49 CFR 176.146 - Segregation from non-hazardous materials.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Segregation from non-hazardous materials. 176.146... VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.146 Segregation from non... for “away from” segregation apply. (2) An explosive substance or article which has a secondary...

49 CFR 176.140 - Segregation from other classes of hazardous materials.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Segregation from other classes of hazardous... CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.140 Segregation from other classes of hazardous materials. (a) Class 1 (explosive) materials must be segregated...

41 CFR 109-1.5106 - Segregation of personal property.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Segregation of personal...-INTRODUCTION 1.51-Personal Property Management Standards and Practices § 109-1.5106 Segregation of personal...) The segregation of the property would materially hinder the progress of the work (i.e., segregation is...

Income Segregation between Schools and School Districts

ERIC Educational Resources Information Center

Owens, Ann; Reardon, Sean F.; Jencks, Christopher

2016-01-01

Although trends in the racial segregation of schools are well documented, less is known about trends in income segregation. We use multiple data sources to document trends in income segregation between schools and school districts. Between-district income segregation of families with children enrolled in public school increased by over 15% from…

49 CFR 176.144 - Segregation of Class 1 (explosive) materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Segregation of Class 1 (explosive) materials. 176... VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.144 Segregation of Class... any ferrous metal or aluminum alloy, unless separated by a partition. (e) Segregation on deck: When...

49 CFR 176.144 - Segregation of Class 1 (explosive) materials.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Segregation of Class 1 (explosive) materials. 176... VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.144 Segregation of Class... any ferrous metal or aluminum alloy, unless separated by a partition. (e) Segregation on deck: When...

49 CFR 176.146 - Segregation from non-hazardous materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Segregation from non-hazardous materials. 176.146... VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.146 Segregation from non... for “away from” segregation apply. (2) An explosive substance or article which has a secondary...

49 CFR 176.140 - Segregation from other classes of hazardous materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Segregation from other classes of hazardous... CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.140 Segregation from other classes of hazardous materials. (a) Class 1 (explosive) materials must be segregated...

46 CFR 148.120 - Stowage and segregation requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Stowage and segregation requirements. 148.120 Section... OF BULK SOLID MATERIALS THAT REQUIRE SPECIAL HANDLING Stowage and Segregation § 148.120 Stowage and segregation requirements. (a) Each material listed in Table 148.10 of this part must be segregated from...

Shaping Income Segregation in Schools: The Role of School Attendance Zone Geography

ERIC Educational Resources Information Center

Saporito, Salvatore

2017-01-01

This study investigates how much the geographic shapes of school attendance zones contributes to their levels of income segregation while holding constant levels of income segregation across residential areas. Income segregation across attendance zones is measured with the rank ordered information theory index. Income segregation across…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenik, E.A.

X-ray microanalysis in an analytical electron microscope is a proven technique for the measurement of solute segregation in alloys. Solute segregation under equilibrium or nonequilibrium conditions can strongly influence material performance. X-ray microanalysis in an analytical electron microscope provides an alternative technique to measure grain boundary segregation, as well as segregation to other defects not accessible to Auger analysis. The utility of the technique is demonstrated by measurements of equilibrium segregation to boundaries in an antimony containing stainless steel, including the variation of segregation with boundary character and by measurements of nonequilibrium segregation to boundaries and dislocations in an ion-irradiatedmore » stainless steel.« less

Death by Segregation: Does the Dimension of Racial Segregation Matter?

PubMed

Yang, Tse-Chuan; Matthews, Stephen A

2015-01-01

The county-level geographic mortality differentials have persisted in the past four decades in the United States (US). Though several socioeconomic factors (e.g., inequality) partially explain this phenomenon, the role of race/ethnic segregation, in general, and the different dimensions of segregation, more specifically, has been underexplored. Focusing on all-cause age-sex standardized US county-level mortality (2004-2008), this study has two substantive goals: (1) to understand whether segregation is a determinant of mortality and if yes, how the relationship between segregation and mortality varies by racial/ethnic dyads (e.g., white/black), and (2) to explore whether different dimensions of segregation (i.e., evenness, exposure, concentration, centralization, and clustering) are associated with mortality. A third goal is methodological: to assess whether spatial autocorrelation influences our understanding of the associations between the dimensions of segregation and mortality. Race/ethnic segregation was found to contribute to the geographic mortality disparities. Moreover, the relationship with mortality differed by both race/ethnic group and the dimension of segregation. Specifically, white/black segregation is positively related to mortality, whereas the segregation between whites and non-black minorities is negatively associated with mortality. Among the five dimensions of segregation, evenness and exposure are more strongly related to mortality than other dimensions. Spatial filtering approaches also identified six unique spatial patterns that significantly affect the spatial distribution of mortality. These patterns offer possible insights that help identify omitted variables related to the persistent patterning of mortality in the US.

Steadily oscillating axial bands of binary granules in a nearly filled coaxial cylinder.

PubMed

Inagaki, Shio; Ebata, Hiroyuki; Yoshikawa, Kenichi

2015-01-01

Granular materials often segregate under mechanical agitation such as flowing, shaking, or rotating, in contrast to an expectation of mixing. It is well known that bidisperse mixtures of granular materials in a partially filled rotating cylinder exhibit monotonic coarsening dynamics of segregation. Here we report the steady oscillation of segregated axial bands under the stationary rotation of a nearly filled coaxial cylinder for O(10(3)) revolutions. The axial bands demonstrate steady back-and-forth motion along the axis of rotation. Experimental findings indicated that these axial band dynamics are driven by global convection throughout the system. The essential features of the spatiotemporal dynamics are reproduced with a simple phenomenological equation that incorporates the effect of global convection.

Granular Segregation Driven by Particle Interactions

NASA Astrophysics Data System (ADS)

Lozano, C.; Zuriguel, I.; Garcimartín, A.; Mullin, T.

2015-05-01

We report the results of an experimental study of particle-particle interactions in a horizontally shaken granular layer that undergoes a second order phase transition from a binary gas to a segregation liquid as the packing fraction C is increased. By focusing on the behavior of individual particles, the effect of C is studied on (1) the process of cluster formation, (2) cluster dynamics, and (3) cluster destruction. The outcomes indicate that the segregation is driven by two mechanisms: attraction between particles with the same properties and random motion with a characteristic length that is inversely proportional to C . All clusters investigated are found to be transient and the probability distribution functions of the separation times display a power law tail, indicating that the splitting probability decreases with time.

Progressive Retinal Atrophy in the Border Collie: A new XLPRA

PubMed Central

Vilboux, Thierry; Chaudieu, Gilles; Jeannin, Patricia; Delattre, Delphine; Hedan, Benoit; Bourgain, Catherine; Queney, Guillaume; Galibert, Francis; Thomas, Anne; André, Catherine

2008-01-01

Background Several forms of progressive retinal atrophy (PRA) segregate in more than 100 breeds of dog with each PRA segregating in one or a few breeds. This breed specificity may be accounted for by founder effects and genetic drift, which have reduced the genetic heterogeneity of each breed, thereby facilitating the identification of causal mutations. We report here a new form of PRA segregating in the Border Collie breed. The clinical signs, including the loss of night vision and a progressive loss of day vision, resulting in complete blindness, occur at the age of three to four years and may be detected earlier through systematic ocular fundus examination and electroretinography (ERG). Results Ophthalmic examinations performed on 487 dogs showed that affected dogs present a classical form of PRA. Of those, 274 have been sampled for DNA extraction and 87 could be connected through a large pedigree. Segregation analysis suggested an X-linked mode of transmission; therefore both XLPRA1 and XLPRA2 mutations were excluded through the genetic tests. Conclusion Having excluded these mutations, we suggest that this PRA segregating in Border Collie is a new XLPRA (XLPRA3) and propose it as a potential model for the homologous human disease, X-Linked Retinitis Pigmentosa. PMID:18315866

A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

NASA Technical Reports Server (NTRS)

Jayne, D. T.; Smialek, J. L.

1993-01-01

Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

DNA-damage response during mitosis induces whole-chromosome missegregation.

PubMed

Bakhoum, Samuel F; Kabeche, Lilian; Murnane, John P; Zaki, Bassem I; Compton, Duane A

2014-11-01

Many cancers display both structural (s-CIN) and numerical (w-CIN) chromosomal instabilities. Defective chromosome segregation during mitosis has been shown to cause DNA damage that induces structural rearrangements of chromosomes (s-CIN). In contrast, whether DNA damage can disrupt mitotic processes to generate whole chromosomal instability (w-CIN) is unknown. Here, we show that activation of the DNA-damage response (DDR) during mitosis selectively stabilizes kinetochore-microtubule (k-MT) attachments to chromosomes through Aurora-A and PLK1 kinases, thereby increasing the frequency of lagging chromosomes during anaphase. Inhibition of DDR proteins, ATM or CHK2, abolishes the effect of DNA damage on k-MTs and chromosome segregation, whereas activation of the DDR in the absence of DNA damage is sufficient to induce chromosome segregation errors. Finally, inhibiting the DDR during mitosis in cancer cells with persistent DNA damage suppresses inherent chromosome segregation defects. Thus, the DDR during mitosis inappropriately stabilizes k-MTs, creating a link between s-CIN and w-CIN. The genome-protective role of the DDR depends on its ability to delay cell division until damaged DNA can be fully repaired. Here, we show that when DNA damage is induced during mitosis, the DDR unexpectedly induces errors in the segregation of entire chromosomes, thus linking structural and numerical chromosomal instabilities. ©2014 American Association for Cancer Research.

Intergroup contact, friendship quality and political attitudes in integrated and segregated schools in Northern Ireland.

PubMed

Stringer, Maurice; Irwing, P; Giles, M; McClenahan, C; Wilson, R; Hunter, J A

2009-06-01

This study examines the effects of integrated and segregated schooling on Northern Irish children's self-reported contact and friendship with members of the other denominational group in school and community settings. To assess the effects of cross group friendships and cross group contacts in school and outside school on children's political attitudes. A cross-sectional design was employed with 1732 children being assessed at three age levels 11,12 & 14 years in eight-matched integrated, maintained (Catholic) and controlled (Protestant) schools. Lisrel modelling was used to investigate the interrelationships among cross group friendship quality, cross group contacts in school and outside school and children's political attitudes. Intergroup contact within and outside school was reported frequently in integrated schools but only occasionally in segregated schools. Modelling revealed that cross group contacts in school and outside school were both associated with less extreme political attitudes. Friendship quality with cross group members had no significant effects on political attitudes. The results provide support for educating Protestants and Catholics together as a means of moderating attitudes and creating cross-community friendships in a divided society.

Effects of centrifugal acceleration on the flows and segregation in vertical Bridgman crystal growth with steady ampoule rotation

NASA Astrophysics Data System (ADS)

Lan, C. W.

2001-07-01

The effects of centrifugal acceleration on the flows and segregation in vertical Bridgman crystal growth with steady ampoule rotation are investigated through numerical simulation. The numerical model is based on the Boussinesq approximation in a rotating frame, and the fluid flow, heat and mass transfer, and the growth interface are solved simultaneously by a robust finite-volume/Newton method. The growth of gallium-doped germanium (GaGe) in the Grenoble furnace is adopted as an example. The calculated results at small Froude number (Fr<<1) are consistent with the previous prediction (Lan, J. Crystal growth 197 (1999) 983). However, at a high rotation speed or in reduced gravity, where the centrifugal acceleration becomes important (Fr˜1), the results are quite different due to the secondary flow induced. Since the direction of the induced flow is different from that of the buoyancy convection due to the concave interface, the flow damping is more effective than that due to the Coriolis force alone. More importantly, radial segregation can be reversed during the flow transition from one to the other.

A Revaluation of Indexes of Residential Segregation

ERIC Educational Resources Information Center

Winship, Christopher

1977-01-01

Shows that there are at least two different perspectives from which residential segregation can be examined. Segregation can be measured as it deviates from a situation of complete desegregation or in terms of a situation in which there is random segregation in the city. New criteria for indexes of residential segregation are developed. (Author/JM)

28 CFR 541.20 - Justification for placement in disciplinary segregation and review of inmates in disciplinary...

Code of Federal Regulations, 2010 CFR

2010-07-01

... disciplinary segregation and review of inmates in disciplinary segregation. 541.20 Section 541.20 Judicial... disciplinary segregation and review of inmates in disciplinary segregation. (a) Except as provided in paragraph... the physical confines of administrative detention, and (3) upon advice of appropriate medical staff...

43 CFR 3873.1 - Segregation of mineral from non-mineral land.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Segregation of mineral from non-mineral... AND CONFLICTS Segregation § 3873.1 Segregation of mineral from non-mineral land. Where a survey is... satisfactorily established that there are existent prior unpatented mining claims, the segregation of the latter...

Income Segregation between Schools and School Districts. CEPA Working Paper No. 16-04

ERIC Educational Resources Information Center

Owens, Ann; Reardon, Sean F.; Jencks, Christopher

2016-01-01

Although trends in the racial segregation of schools are well documented, less is known about trends in "income" segregation. We use multiple data sources to document trends in income segregation between schools and school districts. Between-district income segregation of families with children enrolled in public school increased by over…

Segregation as Splitting, Segregation as Joining: Schools, Housing, and the Many Modes of Jim Crow

ERIC Educational Resources Information Center

Highsmith, Andrew R.; Erickson, Ansley T.

2015-01-01

Popular understandings of segregation often emphasize the Jim Crow South before the 1954 "Brown" decision and, in many instances, explain continued segregation in schooling as the result of segregated housing patterns. The case of Flint, Michigan, complicates these views, at once illustrating the depth of governmental commitment to…

A Naturalistic Observational Study of Informal Segregation: Seating Patterns in Lectures

ERIC Educational Resources Information Center

Koen, Jennifer; Durrheim, Kevin

2010-01-01

In spite of the removal of legislated racial segregation, a number of observational studies in South Africa and elsewhere have shown that "informal," nonlegislated segregation persists in spaces of everyday interaction. Most of these have been case studies of segregation at single sites. The authors seek to quantify segregation in a…

Compositional inhomogeneityand segregation in (K 0.5Na 0.5)NbO 3 ceramics

DOE PAGES

Chen, Kepi; Tang, Jing; Chen, Yan

2016-03-11

The effects of the calcination temperature of (K 0.5Na 0.5)NbO 3 (KNN) powder on the sintering and piezoelectric properties of KNN ceramics have been investigated in this report. KNN powders are synthesized via the solid-state approach. Scanning electron microscopy and X-ray diffraction characterizations indicate that the incomplete reaction at 700 °C and 750 °C calcination results in the compositional inhomogeneity of the K-rich and Na-rich phases while the orthorhombic single phase is obtained after calcination at 900 °C. During the sintering, the presence of the liquid K-rich phase due to the lower melting point has a significant impact on themore » densification, the abnormal grain growth and the deteriorated piezoelectric properties. From the standpoint of piezoelectric properties, the optimal calcination temperature obtained for KNN ceramics calcined at this temperature is determined to be 800 °C, with piezoelectric constant d 33=128.3 pC/N, planar electromechanical coupling coefficient k p=32.2%, mechanical quality factor Q m=88, and dielectric loss tan δ=2.1%.« less

The effect of clouds on the earth's radiation budget

NASA Technical Reports Server (NTRS)

Ziskin, Daniel; Strobel, Darrell F.

1991-01-01

The radiative fluxes from the Earth Radiation Budget Experiment (ERBE) and the cloud properties from the International Satellite Cloud Climatology Project (ISCCP) over Indonesia for the months of June and July of 1985 and 1986 were analyzed to determine the cloud sensitivity coefficients. The method involved a linear least squares regression between co-incident flux and cloud coverage measurements. The calculated slope is identified as the cloud sensitivity. It was found that the correlations between the total cloud fraction and radiation parameters were modest. However, correlations between cloud fraction and IR flux were improved by separating clouds by height. Likewise, correlations between the visible flux and cloud fractions were improved by distinguishing clouds based on optical depth. Calculating correlations between the net fluxes and either height or optical depth segregated cloud fractions were somewhat improved. When clouds were classified in terms of their height and optical depth, correlations among all the radiation components were improved. Mean cloud sensitivities based on the regression of radiative fluxes against height and optical depth separated cloud types are presented. Results are compared to a one-dimensional radiation model with a simple cloud parameterization scheme.

Growth and optical properties of Pr,Yb-codoped KY 3F 10 fluoride single crystals for up-conversion visible luminescence

NASA Astrophysics Data System (ADS)

Kim, Kyoung Jin; Jouini, Anis; Yoshikawa, Akira; Simura, Rayko; Boulon, Georges; Fukuda, Tsuguo

2007-02-01

We investigate different ways to realize laser emission from (Pr 3+) 3P J=0,1,2 levels by pump sources other than the common argon and excimer-dye laser. The use of infrared (IR) laser diodes in combination with intra- and inter-ionic energy transfer processes (up-conversion) could be an efficient solution towards laser oscillation. Pr 3+,Yb 3+-codoped KY 3F 10 (Pr, Yb:KYF) single crystals were successfully grown by the micro-pulling-down (μ-PD) method. The crystals were transparent with a slightly greenish color, 2.0-2.5 mm in diameter, 20-30 mm in length and free from visible inclusions and cracks. Effective segregation coefficients of Pr and Yb in KYF were studied by means of absorption and chemical analysis. Strong visible emission via selective IR pumping with λ=975 nm and up-conversion excitation were obtained in Pr, Yb:KYF at room temperature (RT). Luminescence measurements have been carried out and the decay kinetics of the Pr 3+ visible emissions was investigated by room temperature time-resolved spectra.

Deleterious mutations and selection for sex in finite diploid populations.

PubMed

Roze, Denis; Michod, Richard E

2010-04-01

In diploid populations, indirect benefits of sex may stem from segregation and recombination. Although it has been recognized that finite population size is an important component of selection for recombination, its effects on selection for segregation have been somewhat less studied. In this article, we develop analytical two- and three-locus models to study the effect of recurrent deleterious mutations on a modifier gene increasing sex, in a finite diploid population. The model also incorporates effects of mitotic recombination, causing loss of heterozygosity (LOH). Predictions are tested using multilocus simulations representing deleterious mutations occurring at a large number of loci. The model and simulations show that excess of heterozygosity generated by finite population size is an important component of selection for sex, favoring segregation when deleterious alleles are nearly additive to dominant. Furthermore, sex tends to break correlations in homozygosity among selected loci, which disfavors sex when deleterious alleles are either recessive or dominant. As a result, we find that it is difficult to maintain costly sex when deleterious alleles are recessive. LOH tends to favor sex when deleterious mutations are recessive, but the effect is relatively weak for rates of LOH corresponding to current estimates (of the order 10(-4)-10(-5)).

Generative Models of Segregation: Investigating Model-Generated Patterns of Residential Segregation by Ethnicity and Socioeconomic Status

PubMed Central

Fossett, Mark

2011-01-01

This paper considers the potential for using agent models to explore theories of residential segregation in urban areas. Results of generative experiments conducted using an agent-based simulation of segregation dynamics document that varying a small number of model parameters representing constructs from urban-ecological theories of segregation can generate a wide range of qualitatively distinct and substantively interesting segregation patterns. The results suggest how complex, macro-level patterns of residential segregation can arise from a small set of simple micro-level social dynamics operating within particular urban-demographic contexts. The promise and current limitations of agent simulation studies are noted and optimism is expressed regarding the potential for such studies to engage and contribute to the broader research literature on residential segregation. PMID:21379372

Black-white metropolitan segregation and self-rated health: Investigating the role of neighborhood poverty.

PubMed

Do, D Phuong; Frank, Reanne; Iceland, John

2017-08-01

While black-white segregation has been consistently linked to detrimental health outcomes for blacks, whether segregation is necessarily a zero-sum arrangement in which some groups accrue health advantages at the expense of other groups and whether metropolitan segregation impacts the health of racial groups uniformly within the metropolitan area, remains unclear. Using nationally representative data from the 2008-2013 National Health Interview Survey linked to Census data, we investigate whether the association between metropolitan segregation and health is invariant within the metropolitan area or whether it is modified by neighborhood poverty for black and white Americans. In doing so, we assess the extent to which segregation involves direct health tradeoffs between blacks and whites. We conduct race-stratified multinomial and logistic regression models to assess the relationship between 1) segregation and level of neighborhood poverty and 2) segregation, neighborhood poverty, and poor health, respectively. We find that, for blacks, segregation was associated with a higher likelihood of residing in high poverty neighborhoods, net of individual-level socioeconomic characteristics. Segregation was positively associated with poor health for blacks in high poverty neighborhoods, but not for those in lower poverty neighborhoods. Hence, the self-rated health of blacks clearly suffers as a result of black-white segregation - both directly, and indirectly through exposure to high poverty neighborhoods. We do not find consistent evidence for a direct relationship between segregation and poor health for whites. However, we find some suggestive evidence that segregation may indirectly benefit whites through decreasing their exposure to high poverty environments. These findings underscore the critical role of concentrated disadvantage in the complex interconnection between metropolitan segregation and health. Weakening the link between racial segregation and concentrated poverty via local policy and planning has the potential for broad population-based health improvements and significant reductions in black-white health disparities. Copyright © 2017. Published by Elsevier Ltd.

Public school segregation and juvenile violent crime arrests in metropolitan areas.

PubMed

Eitle, David; Eitle, Tamela McNulty

2010-01-01

Previous research has established an association between residential segregation and violent crime in urban America. Our study examines whether school-based segregation is predictive of arrests of juveniles for violent crimes in U.S. metro areas. Using Census, Uniform Crime Report, and Common Core data for 204 metro areas, a measure of school-based racial segregation, Theil's entropy index, is decomposed into two components: between- and within-district segregation. Findings reveal evidence of a significant interaction term: Within-district segregation is inversely associated with arrests for juvenile violence, but only in metropolitan areas with higher than average levels of between-district segregation.

An agent-based simulation of persistent inequalities in health behavior: Understanding the interdependent roles of segregation, clustering, and social influence.

PubMed

Langellier, Brent A

2016-12-01

Health inequalities are conspicuously persistent through time and often durable even in spite of interventions. In this study, I use agent-based simulation models (ABMs) to understand how the complex interrelationships between residential segregation, social network formation, group-level preferences, and social influence may contribute to this persistence. I use a more-stylized ABM, Bubblegum Village (BV), to understand how initial inequalities in bubblegum-chewing behaviors either endure, increase, or decrease over time given group-level differences in preferences, neighborhood-level barriers or facilitators of bubblegum chewing (e.g., access to bubblegum shops), and agents' preferences for segregation, homophily, and clustering (i.e., the 'tightness' of social networks). I further use BV to understand whether segregation and social network characteristics impact whether the effects of a bubblegum-reduction intervention that is very effective in the short term are durable over time, as well as to identify intervention strategies to reduce attenuation of the intervention effects. In addition to BV, I also present results from an ABM based on the distribution and social characteristics of the population in Philadelphia, PA. This model explores similar questions to BV, but examines racial/ethnic inequalities in soda consumption based on agents' social characteristics and baseline soda consumption probabilities informed by the 2007-2010 National Health and Nutrition Examination Survey. Collectively, the models suggest that residential segregation is a fundamental process for the production and persistence of health inequalities. The other major conclusion of the study is that, for behaviors that are subject to social influence and that cluster within social groups, interventions that are randomly-targeted to individuals with 'bad' behaviors will likely experience a large degree of recidivism to pre-intervention behaviors. In contrast, interventions that target multiple members of the same network, as well as multilevel interventions that include a neighborhood-level component, can reduce recidivism.

Grain size segregation in debris discs

NASA Astrophysics Data System (ADS)

Thebault, P.; Kral, Q.; Augereau, J.-C.

2014-01-01

Context. In most debris discs, dust grain dynamics is strongly affected by stellar radiation pressure. Because this mechanism is size-dependent, we expect dust grains to be spatially segregated according to their sizes. However, because of the complex interplay between radiation pressure, grain processing by collisions, and dynamical perturbations, this spatial segregation of the particle size distribution (PSD) has proven difficult to investigate and quantify with numerical models. Aims: We propose to thoroughly investigate this problem by using a new-generation code that can handle some of the complex coupling between dynamical and collisional effects. We intend to explore how PSDs behave in both unperturbed discs at rest and in discs pertubed by planetary objects. Methods: We used the DyCoSS code to investigate the coupled effect of collisions, radiation pressure, and dynamical perturbations in systems that have reached a steady-state. We considered two setups: a narrow ring perturbed by an exterior planet, and an extended disc into which a planet is embedded. For both setups we considered an additional unperturbed case without a planet. We also investigated the effect of possible spatial size segregation on disc images at different wavelengths. Results: We find that PSDs are always spatially segregated. The only case for which the PSD follows a standard dn ∝ s-3.5ds law is for an unperturbed narrow ring, but only within the parent-body ring itself. For all other configurations, the size distributions can strongly depart from such power laws and have steep spatial gradients. As an example, the geometrical cross-section of the disc is very rarely dominated by the smallest grains on bound orbits, as it is expected to be in standard PSDs in sq with q ≤ -3. Although the exact profiles and spatial variations of PSDs are a complex function of the set-up that is considered, we are still able to derive some reliable results that will be useful for image or SED-fitting models of observed discs.

Gender Segregation in the Spanish Labor Market: An Alternative Approach

ERIC Educational Resources Information Center

del Rio, Coral; Alonso-Villar, Olga

2010-01-01

The aim of this paper is to study occupational segregation by gender in Spain, which is a country where occupational segregation explains a large part of the gender wage gap. As opposed to previous studies, this paper measures not only overall segregation, but also the segregation of several population subgroups. For this purpose, this paper uses…

The Growth of Segregation in American Schools: Changing Patterns of Separation and Poverty since 1968.

ERIC Educational Resources Information Center

Orfield, Gary; And Others

This study shows where school segregation is concentrated and where schools remain highly integrated. It offers the first national comparison of segregation by community size and reveals that segregation remains high in big cities and serious in mid-size central cities. Many African-American and Latino students also attend segregated schools in…

Simulations of the dispersion of reactive pollutants in a street canyon, considering different chemical mechanisms and micromixing

NASA Astrophysics Data System (ADS)

Garmory, A.; Kim, I. S.; Britter, R. E.; Mastorakos, E.

The Stochastic Fields (SF) or Field Monte Carlo method has been used to model the dispersion of reactive scalars in a street canyon, using a simple chemistry and the CBM-IV mechanism. SF is a Probability Density Function (PDF) method which allows both means and variances of the scalars to be calculated as well as considering the effect of segregation on reaction rates. It was found that the variance of reactive scalars such as NO 2 was very high in the mixing region at roof-top level with rms values of the order of the mean values. The effect of segregation on major species such as O 3 was found to be very small using either mechanism, however, some radical species in CBM-IV showed a significant difference. These were found to be the seven species with the fastest chemical timescales. The calculated photostationary state defect was also found to be in error when segregation is neglected.

Segregation control in vertical Bridgman crystal growth

NASA Astrophysics Data System (ADS)

Tao, Y.; Kou, S.

1996-11-01

To help the crystal grow at a constant dopant concentration in vertical Bridgman crystal growth, the dopant concentration of the growth melt, i.e. the melt from which the crystal grows, was kept constant. To achieve this, three different methods were used to replenish the growth melt at a controlled rate and suppress dopant diffusion between the growth melt and the replenishing melt. In method one, a replenishing crucible having a long melt passageway was immersed in the growth melt. In method two, a replenishing crucible having an independent feed-rate control mechanism was held above the growth melt. In method three, a submerged diffusion baffle was used to form a long melt passageway between the growth melt and the replenishing melt. NaNO 3 was used as a model material for crystal growth. Single crystals were grown by these three methods with effective segregation control. Method two was applied to InSb and single crystals were also grown with effective segregation control.

A SHORT SEQUENCE IMMEDIATELY UPSTREAM OF THE INTERNAL REPEAT ELEMENTS IS CRITICAL FOR KSHV LANA MEDIATED DNA REPLICATION AND IMPACTS EPISOME PERSISTENCE

PubMed Central

León Vázquez, Erika De; Juillard, Franceline; Rosner, Bernard; Kaye, Kenneth M.

2013-01-01

Kaposi’s sarcoma-associated herpesvirus LANA (1162 residues) mediates episomal persistence of viral genomes during latency. LANA mediates viral DNA replication and segregates episomes to daughter nuclei. A 59 residue deletion immediately upstream of the internal repeat elements rendered LANA highly deficient for DNA replication and modestly deficient for the ability to segregate episomes, while smaller deletions did not. The 59 amino acid deletion reduced LANA episome persistence by ~14-fold, while sequentially smaller deletions resulted in ~3-fold, or no deficiency. Three distinct LANA regions reorganized heterochromatin, one of which contains the deleted sequence, but the deletion did not abolish LANA’s ability to alter chromatin. Therefore, this work identifies a short internal LANA sequence that is critical for DNA replication, has modest effects on episome segregation, and substantially impacts episome persistence; this region may exert its effects through an interacting host cell protein(s). PMID:24314665

Protein Mixture Segregation at Coffee-Ring: Real-Time Imaging of Protein Ring Precipitation by FTIR Spectromicroscopy.

PubMed

Choi, Sun; Birarda, Giovanni

2017-08-03

During natural drying process, all solutions and suspensions tend to form the so-called "coffee-ring" deposits. This phenomenon, by far, has been interpreted by the hydrodynamics of evaporating fluids. However, in this study, by applying Fourier transform infrared imaging (FTIRI), it is possible to observe the segregation and separation of a protein mixture at the "ring", hence we suggest a new way to interpret "coffee-ring effect" of solutions. The results explore the dynamic process that leads to the ring formation in case of model plasma proteins, such as BGG (bovine γ globulin), BSA (bovine serum albumin), and Hfib (human fibrinogen), and also report fascinating discovery of the segregation at the ring deposits of two model proteins BGG and BSA, which can be explained by an energy kinetic model, only. The investigation suggests that the coffee-ring effect of solute in an evaporating solution drop is driven by an energy gradient created from change of particle-water-air interfacial energy configuration.

Distinct Feedforward and Feedback Effects of Microstimulation in Visual Cortex Reveal Neural Mechanisms of Texture Segregation.

PubMed

Klink, P Christiaan; Dagnino, Bruno; Gariel-Mathis, Marie-Alice; Roelfsema, Pieter R

2017-07-05

The visual cortex is hierarchically organized, with low-level areas coding for simple features and higher areas for complex ones. Feedforward and feedback connections propagate information between areas in opposite directions, but their functional roles are only partially understood. We used electrical microstimulation to perturb the propagation of neuronal activity between areas V1 and V4 in monkeys performing a texture-segregation task. In both areas, microstimulation locally caused a brief phase of excitation, followed by inhibition. Both these effects propagated faithfully in the feedforward direction from V1 to V4. Stimulation of V4, however, caused little V1 excitation, but it did yield a delayed suppression during the late phase of visually driven activity. This suppression was pronounced for the V1 figure representation and weaker for background representations. Our results reveal functional differences between feedforward and feedback processing in texture segregation and suggest a specific modulating role for feedback connections in perceptual organization. Copyright © 2017 Elsevier Inc. All rights reserved.

Improved alumina scale adhesion of electron beam physical vapor deposited Dy/Hf-doped β-NiAl coatings

NASA Astrophysics Data System (ADS)

Li, Dongqing; Guo, Hongbo; Peng, Hui; Gong, Shengkai; Xu, Huibin

2013-10-01

The cyclic oxidation behavior of Dy/Hf-doped β-NiAl coatings produced by electron beam physical vapor deposition (EB-PVD) was investigated. For the undoped NiAl coating, numerous voids were formed at the alumina scale/coating interface and large rumpling developed in the scale, leading to premature oxide spallation. The addition of Dy and Hf both improved scale adhesion and the alumina scale grown on the NiAl-Hf coating showed better adhesion than that on the NiAl-Dy coating, although the suppressing effect on interfacial void formation and the scale rumpling resistance were stronger in the NiAl-Dy coating. It is proposed that the segregation of Dy and Hf ions at the scale/coating interfaces not only prevent interfacial sulfur segregation but also may directly enhance interfacial adhesion by participating in bonding across the interfaces, and this strengthening effect is relatively stronger for Hf ionic segregation.

Segregation in like-charged polyelectrolyte-surfactant mixtures can be precisely tuned via manipulation of the surfactant mass ratio.

PubMed

Wills, Peter W; Lopez, Sonia G; Burr, Jocelyn; Taboada, Pablo; Yeates, Stephen G

2013-04-09

In this study, we consider segregative phase separation in aqueous mixtures of quaternary ammonium surfactants didecyldimethylammonium chloride (DDQ) and alkyl (C12, 70%; C14 30%) dimethyl benzyl ammonium chloride (BAC) upon the addition of poly(diallyldimethylammonium) chloride (pDADMAC) as a function of both concentration and molecular weight. The nature of the surfactant type is dominant in determining the concentration at which separation into an upper essentially surfactant-rich phase and lower polyelectrolyte-rich phase is observed. However, for high-molecular-weight pDADMAC there is a clear indication of an additional depletion flocculation effect. When the BAC/DDQ ratio is tuned, the segregative phase separation point can be precisely controlled. We propose a phase separation mechanism for like-charged quaternary ammonium polyelectrolyte/surfactant/water mixtures induced by a reduction in the ionic atmosphere around the surfactant headgroup and possible ion pair formation. An additional polyelectrolyte-induced depletion flocculation effect was also observed.

Experimental investigation of the origin of fynbos plant community structure after fire.

PubMed

Silvertown, Jonathan; Araya, Yoseph N; Linder, H Peter; Gowing, David J

2012-11-01

Species in plant communities segregate along fine-scale hydrological gradients. Although this phenomenon is not unique to fynbos, this community regenerates after fire and therefore provides an opportunity to study the ecological genesis of hydrological niche segregation. Following wildfires at two field sites where we had previously mapped the vegetation and monitored the hydrology, seeds were moved experimentally in >2500 intact soil cores up and down soil-moisture gradients to test the hypothesis that hydrological niche segregation is established during the seedling phase of the life cycle. Seedling numbers and growth were then monitored and they were identified using DNA bar-coding, the first use of this technology for an experiment of this kind. At the site where niche segregation among Restionaceae had previously been found, the size of seedlings was significantly greater, the wetter the location into which they were moved, regardless of the soil moisture status of their location of origin, or of the species. Seedling weight was also significantly greater in a competition treatment where the roots of other species were excluded. No such effects were detected at the control site where niche segregation among Restionaceae was previously found to be absent. The finding that seedling growth on hydrological gradients in the field is affected by soil moisture status and by root competition shows that hydrological niche segregation could potentially originate in the seedling stage. The methodology, applied at a larger scale and followed-through for a longer period, could be used to determine whether species are differently affected by soil moisture.

Residential segregation and racial disparities in self-rated health: How do dimensions of residential segregation matter?1

PubMed Central

Yang, Tse-Chuan; Zhao, Yunhan; Song, Qian

2016-01-01

Previous research on segregation and health has been criticized for overlooking the fact that segregation is a multi-dimensional concept (i.e., evenness, exposure, concentration, centralization, and clustering) and recent evidence drawn from non-black minorities challenges the conventional belief that residential segregation widens racial health disparities. Combining a survey data (n=18,752) from Philadelphia with the 2010 Census tract (n=925) data, we examine two theoretical frameworks to understand why the association of segregation with health may differ by race/ethnicity. Specifically, we investigate how each dimension of segregation contributed to racial disparities in self-rated health. We found (1) high levels of white/ black concentration could exacerbate the white/black health disparities up to 25 percent, (2) the white/Hispanic health disparities was narrowed by increasing the level of white/Hispanic centralization, and (3) no single dimension of segregation statistically outperforms others. Our findings supported that segregation is bad for blacks but may be beneficial for Hispanics. PMID:27886735

Neighbourhood racial/ethnic composition and segregation and trajectories of cognitive decline among US older adults.

PubMed

Kovalchik, Stephanie A; Slaughter, Mary E; Miles, Jeremy; Friedman, Esther M; Shih, Regina A

2015-10-01

The influence of the sociodemographic context of one's environment on cognitive ageing is not well understood. We examined differences in cognitive trajectories according to the racial/ethnic characteristics of the residential environment. On the basis of 63 996 person-years of data from a nationally representative cohort of 6150 adults over the age of 50 years from the Health and Retirement Study, we used multivariate linear mixed models to determine the effect of neighbourhood racial/ethnic composition and county-level segregation on cognitive function and cognitive decline over a 10-year period. In models adjusting for individual demographic and health characteristics, Hispanic composition had a significant positive association with cognitive function (standardised β=0.136, p<0.05) and moderate evidence of an association with greater cognitive decline (standardised β=-0.014, p=0.09). Greater Hispanic-white segregation was associated with statistically significant higher cognitive function at baseline (standardised β=0.099, p<0.001) and greater cognitive decline (standardised β=-0.011, p<0.01). For a 20 percentage-point increase in Hispanic composition and segregation, the observed associations implied 1 and 1.25 additional years of cognitive ageing over 10 years, respectively. These effects did not differ by individual race/ethnicity and were not explained by neighbourhood socioeconomic status or neighbourhood selection. Black composition and black-white segregation did not have a significant influence on cognitive ageing. This study demonstrates disparities in the progression of cognitive ageing according to racial/ethnic characteristics of the neighbourhood environment. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Micro and Macro Segregation in Alloys Solidifying with Equiaxed Morphology

NASA Technical Reports Server (NTRS)

Stefanescu, Doru M.; Curreri, Peter A.; Leon-Torres, Jose; Sen, Subhayu

1996-01-01

To understand macro segregation formation in Al-Cu alloys, experiments were run under terrestrial gravity (1g) and under low gravity during parabolic flights (10(exp -2) g). Alloys of two different compositions (2% and 5% Cu) were solidified at two different cooling rates. Systematic microscopic and SEM observations produced microstructural and segregation maps for all samples. These maps may be used as benchmark experiments for validation of microstructure evolution and segregation models. As expected, the macro segregation maps are very complex. When segregation was measured along the central axis of the sample, the highest macro segregation for samples solidified at 1g was obtained for the lowest cooling rate. This behavior is attributed to the longer time available for natural convection and shrinkage flow to affect solute redistribution. In samples solidified under low-g, the highest macro-segregation was obtained at the highest cooling rate. In general, low-gravity solidification resulted in less segregation. To explain the experimental findings, an analytical (Flemings-Nereo) and a numerical model were used. For the numerical model, the continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the microscopic transport phenomena, for a two-phase system. The model proposed considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The Flemings-Nereo model explains well macro segregation in the initial stages of low-gravity segregation. The numerical model can describe the complex macro segregation pattern and the differences between low- and high-gravity solidification.

Two critical periods in early visual cortex during figure-ground segregation.

PubMed

Wokke, Martijn E; Sligte, Ilja G; Steven Scholte, H; Lamme, Victor A F

2012-11-01

The ability to distinguish a figure from its background is crucial for visual perception. To date, it remains unresolved where and how in the visual system different stages of figure-ground segregation emerge. Neural correlates of figure border detection have consistently been found in early visual cortex (V1/V2). However, areas V1/V2 have also been frequently associated with later stages of figure-ground segregation (such as border ownership or surface segregation). To causally link activity in early visual cortex to different stages of figure-ground segregation, we briefly disrupted activity in areas V1/V2 at various moments in time using transcranial magnetic stimulation (TMS). Prior to stimulation we presented stimuli that made it possible to differentiate between figure border detection and surface segregation. We concurrently recorded electroencephalographic (EEG) signals to examine how neural correlates of figure-ground segregation were affected by TMS. Results show that disruption of V1/V2 in an early time window (96-119 msec) affected detection of figure stimuli and affected neural correlates of figure border detection, border ownership, and surface segregation. TMS applied in a relatively late time window (236-259 msec) selectively deteriorated performance associated with surface segregation. We conclude that areas V1/V2 are not only essential in an early stage of figure-ground segregation when figure borders are detected, but subsequently causally contribute to more sophisticated stages of figure-ground segregation such as surface segregation.

Two critical periods in early visual cortex during figure–ground segregation

PubMed Central

Wokke, Martijn E; Sligte, Ilja G; Steven Scholte, H; Lamme, Victor A F

2012-01-01

The ability to distinguish a figure from its background is crucial for visual perception. To date, it remains unresolved where and how in the visual system different stages of figure–ground segregation emerge. Neural correlates of figure border detection have consistently been found in early visual cortex (V1/V2). However, areas V1/V2 have also been frequently associated with later stages of figure–ground segregation (such as border ownership or surface segregation). To causally link activity in early visual cortex to different stages of figure–ground segregation, we briefly disrupted activity in areas V1/V2 at various moments in time using transcranial magnetic stimulation (TMS). Prior to stimulation we presented stimuli that made it possible to differentiate between figure border detection and surface segregation. We concurrently recorded electroencephalographic (EEG) signals to examine how neural correlates of figure–ground segregation were affected by TMS. Results show that disruption of V1/V2 in an early time window (96–119 msec) affected detection of figure stimuli and affected neural correlates of figure border detection, border ownership, and surface segregation. TMS applied in a relatively late time window (236–259 msec) selectively deteriorated performance associated with surface segregation. We conclude that areas V1/V2 are not only essential in an early stage of figure–ground segregation when figure borders are detected, but subsequently causally contribute to more sophisticated stages of figure–ground segregation such as surface segregation. PMID:23170239

Growth of silicon carbide crystals on a seed while pulling silicon crystals from a melt

NASA Technical Reports Server (NTRS)

Ciszek, T. F.; Schwuttke, G. H. (Inventor)

1979-01-01

A saturated solution of silicon and an element such as carbon having a segregation coefficient less than unity is formed by placing a solid piece of carbon in a body of molten silicon having a temperature differential decreasing toward the surface. A silicon carbide seed crystal is disposed on a holder beneath the surface of the molten silicon. As a rod or ribbon of silicon is slowly pulled from the melt, a supersaturated solution of carbon in silicon is formed in the vicinity of the seed crystal. Excess carbon is emitted from the solution in the form of silicon carbide which crystallizes on the seed crystal held in the cool region of the melt.

Communication: Virial coefficients and demixing in highly asymmetric binary additive hard-sphere mixtures.

PubMed

López de Haro, Mariano; Tejero, Carlos F; Santos, Andrés

2013-04-28

The problem of demixing in a binary fluid mixture of highly asymmetric additive hard spheres is revisited. A comparison is presented between the results derived previously using truncated virial expansions for three finite size ratios with those that one obtains with the same approach in the extreme case in which one of the components consists of point particles. Since this latter system is known not to exhibit fluid-fluid segregation, the similarity observed for the behavior of the critical constants arising in the truncated series in all instances, while not being conclusive, may cast serious doubts as to the actual existence of a demixing fluid-fluid transition in disparate-sized binary additive hard-sphere mixtures.

Synthesis of nanopowders of the aluminum-substituted lanthanum gallate solid electrolyte by mechanochemical route

NASA Astrophysics Data System (ADS)

Domingues, Eddy M.; Gonçalves, Priscila; Figueiredo, Filipe M.

2012-07-01

The room temperature mechanosynthesis of La1-xSrxGa1-y-zMgyAlzO3-δ nanopowders is successfully demonstrated for a broad compositional range (x ≤ 0.1; y ≤ 0.2, z ≤ 0.4) by resorting to a nearly amorphous alumina precursor with enhanced reactivity. It is shown that ceramics with one single phase and free from open porosity can be obtained by sintering these nanopowders at 1350-1450 °C. Microstructural data show that the substitution of Ga by Al hinders densification and decreases the grain size of ceramics. This is explained assuming the segregation of aluminum cations to the grain boundaries as a result of the decrease of the cationic diffusion coefficients.

43 CFR 2091.5-1 - Segregation of lands resulting from withdrawal applications filed on or after October 21, 1976.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Segregation of lands resulting from... RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Segregation and Opening of Lands § 2091.5-1 Segregation... publication and extends for a period of 2 years unless sooner terminated as set out below. (b) Segregations...

43 CFR 2091.5-2 - Segregation of lands resulting from withdrawal applications filed prior to October 21, 1976.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Segregation of lands resulting from... RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Segregation and Opening of Lands § 2091.5-2 Segregation... modifies the term of segregation for all lands covered by the amended application to conform with the...

Effect of Various Material Properties on the Adhesive Stage of Fretting

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1974-01-01

Various properties of metals and alloys were studied with respect to their effect on the initial stage of the fretting process, namely adhesion. Crystallographic orientation, crystal structure, interfacial binding energies of dissimiliar metal, segregation of alloy constituents and the nature and structure of surface films were found to influence adhesion. High atomic density, low surface energy grain orientations exhibited lower adhesion than other orientations. Knowledge of interfacial surface binding energies assists in predicting adhesive transfer and wear. Selective surface segregation of alloy constituents accomplishes both a reduction in adhesion and improved surface oxidation characteristics. Equivalent surface coverages of various adsorbed species indicate that some are markedly more effective in inhibiting adhesion than others.

Granular segregation driven by particle interactions.

PubMed

Lozano, C; Zuriguel, I; Garcimartín, A; Mullin, T

2015-05-01

We report the results of an experimental study of particle-particle interactions in a horizontally shaken granular layer that undergoes a second order phase transition from a binary gas to a segregation liquid as the packing fraction C is increased. By focusing on the behavior of individual particles, the effect of C is studied on (1) the process of cluster formation, (2) cluster dynamics, and (3) cluster destruction. The outcomes indicate that the segregation is driven by two mechanisms: attraction between particles with the same properties and random motion with a characteristic length that is inversely proportional to C. All clusters investigated are found to be transient and the probability distribution functions of the separation times display a power law tail, indicating that the splitting probability decreases with time.

Minimizing Segregation During the Controlled Directional Solidification of Dendritic Alloys Publication: Metallurgical and Materials Transactions

NASA Technical Reports Server (NTRS)

Grugel, R. N.; Fedoseyev, A. I.; Kim, S.; Curreri, Peter A. (Technical Monitor)

2002-01-01

Gravity-driven thermosolutal convection that arises during controlled directional solidification (DS) of dendritic alloys promotes detrimental macro-segregation (e.g. freckles and steepling) in products such as turbine blades. Considerable time and effort has been spent to experimentally and theoretically investigate this phenomena; although our knowledge has advanced to the point where convection can be modeled and accurately compared to experimental results, little has been done to minimize its onset and deleterious effects. The experimental work demonstrates that segregation can be. minimized and microstructural uniformity promoted when a slow axial rotation is applied to the sample crucible during controlled directional solidification processing. Numerical modeling utilizing continuation and bifurcation methods have been employed to develop accurate physical and mathematical models with the intent of identifying and optimizing processing parameters.

Macrosegregation and Microstructural Evolution in a Pressure-Vessel Steel

NASA Astrophysics Data System (ADS)

Pickering, E. J.; Bhadeshia, H. K. D. H.

2014-06-01

This work assesses the consequences of macrosegregation on microstructural evolution during solid-state transformations in a continuously cooled pressure-vessel steel (SA508 Grade 3). Stark spatial variations in microstructure are observed following a simulated quench from the austenitization temperature, which are found to deliver significant variations in hardness. Partial-transformation experiments are used to show the development of microstructure in segregated material. Evidence is presented which indicates the bulk microstructure is not one of upper bainite, as it has been described in the past, but one comprised of Widmanstätten ferrite and pockets of lower bainite. Segregation is observed on three different length scales, and the origins of each type are proposed. Suggestions are put forward for how the segregation might be minimized, and its detrimental effects suppressed by heat treatments.

Dislocation nucleation facilitated by atomic segregation

NASA Astrophysics Data System (ADS)

Zou, Lianfeng; Yang, Chaoming; Lei, Yinkai; Zakharov, Dmitri; Wiezorek, Jörg M. K.; Su, Dong; Yin, Qiyue; Li, Jonathan; Liu, Zhenyu; Stach, Eric A.; Yang, Judith C.; Qi, Liang; Wang, Guofeng; Zhou, Guangwen

2018-01-01

Surface segregation--the enrichment of one element at the surface, relative to the bulk--is ubiquitous to multi-component materials. Using the example of a Cu-Au solid solution, we demonstrate that compositional variations induced by surface segregation are accompanied by misfit strain and the formation of dislocations in the subsurface region via a surface diffusion and trapping process. The resulting chemically ordered surface regions acts as an effective barrier that inhibits subsequent dislocation annihilation at free surfaces. Using dynamic, atomic-scale resolution electron microscopy observations and theory modelling, we show that the dislocations are highly active, and we delineate the specific atomic-scale mechanisms associated with their nucleation, glide, climb, and annihilation at elevated temperatures. These observations provide mechanistic detail of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems.

Integration and segregation in auditory scene analysis

NASA Astrophysics Data System (ADS)

Sussman, Elyse S.

2005-03-01

Assessment of the neural correlates of auditory scene analysis, using an index of sound change detection that does not require the listener to attend to the sounds [a component of event-related brain potentials called the mismatch negativity (MMN)], has previously demonstrated that segregation processes can occur without attention focused on the sounds and that within-stream contextual factors influence how sound elements are integrated and represented in auditory memory. The current study investigated the relationship between the segregation and integration processes when they were called upon to function together. The pattern of MMN results showed that the integration of sound elements within a sound stream occurred after the segregation of sounds into independent streams and, further, that the individual streams were subject to contextual effects. These results are consistent with a view of auditory processing that suggests that the auditory scene is rapidly organized into distinct streams and the integration of sequential elements to perceptual units takes place on the already formed streams. This would allow for the flexibility required to identify changing within-stream sound patterns, needed to appreciate music or comprehend speech..

Quantitative determination of zero-gravity effects on electronic materials processing germanium crystal growth with simultaneous interface demarcation. Experiment MA-060

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Witt, A. F.

1977-01-01

Experiment MA-060 was designed to establish the crystal growth and segregation characteristics of a melt in a directional solidification configuration under near zero-g conditions. The interface demarcation technique was incorporated into the experiment since it constitutes a unique tool for recording the morphology of the growth rate throughout solidification, and for establishing an absolute time reference framework for all stages of the solidification process. An extensive study was performed of the germanium crystals grown during the Apollo-Soyuz Test Project mission. It was found that single crystal growth was achieved and that the interface demarcation functioned successfully. There was no indication that convection driven by thermal or surface tension gradients was present in the melt. The gallium segregation, in the absence of gravity, was found to be fundamentally different in its initial and its subsequent stages from that of the ground-based tests. None of the existing theoretical models for growth and segregation can account for the observed segregation behavior in the absence of gravity.

Genetic aspect of Alzheimer disease: Results of complex segregation analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadonvick, A.D.; Lee, I.M.L.; Bailey-Wilson, J.E.

1994-09-01

The study was designed to evaluate the possibility that a single major locus will explain the segregation of Alzheimer disease (AD). The data were from the population-based AD Genetic Database and consisted of 402 consecutive, unrelated probands, diagnosed to have either `probable` or `autopsy confirmed` AD and their 2,245 first-degree relatives. In this analysis, a relative was considered affected with AD only when there were sufficient medical/autopsy data to support diagnosis of AD being the most likely cause of the dementia. Transmission probability models allowing for a genotype-dependent and logistically distributed age-of-onset were used. The program REGTL in the S.A.G.E.more » computer program package was used for a complex segregation analysis. The models included correction for single ascertainment. Regressive familial effects were not estimated. The data were analyzed to test for single major locus (SML), random transmission and no transmission (environmental) hypotheses. The results of the complex segregation analysis showed that (1) the SML was the best fit, and (2) the non-genetic models could be rejected.« less

On the modeling of the bottom particles segregation with non-linear diffusion equations: application to the marine sand ripples

NASA Astrophysics Data System (ADS)

Tiguercha, Djlalli; Bennis, Anne-claire; Ezersky, Alexander

2015-04-01

The elliptical motion in surface waves causes an oscillating motion of the sand grains leading to the formation of ripple patterns on the bottom. Investigation how the grains with different properties are distributed inside the ripples is a difficult task because of the segration of particle. The work of Fernandez et al. (2003) was extended from one-dimensional to two-dimensional case. A new numerical model, based on these non-linear diffusion equations, was developed to simulate the grain distribution inside the marine sand ripples. The one and two-dimensional models are validated on several test cases where segregation appears. Starting from an homogeneous mixture of grains, the two-dimensional simulations demonstrate different segregation patterns: a) formation of zones with high concentration of light and heavy particles, b) formation of «cat's eye» patterns, c) appearance of inverse Brazil nut effect. Comparisons of numerical results with the new set of field data and wave flume experiments show that the two-dimensional non-linear diffusion equations allow us to reproduce qualitatively experimental results on particles segregation.

Racial Residential Segregation and STI Diagnosis Among Non-Hispanic Blacks, 2006-2010.

PubMed

Lutfi, Khaleeq; Trepka, Mary Jo; Fennie, Kristopher P; Ibañez, Gladys; Gladwin, Hugh

2018-06-01

Sexually transmitted infections (STI) disproportionately impact non-Hispanic blacks. Racial residential segregation has been associated with negative socioeconomic outcomes. We sought to examine the association between segregation and STI diagnosis among blacks. The National Survey of Family Growth and US Census served as data sources. Five distinct dimensions represent segregation. The association between STI diagnosis and each segregation dimension was assessed with multilevel logistic regression modeling. 305 (7.4%) blacks reported STI diagnosis during the past 12 months. Depending on the dimension, segregation was a risk factor [dissimilarity aOR 2.41 (95% CI 2.38-2.43)] and a protective factor [isolation aOR 0.90 (95% CI 0.89-0.91)] for STI diagnosis. Findings suggest that STI diagnosis among blacks is associated with segregation. Additional research is needed to identify mechanisms for how segregation affects STI diagnosis and to aid in the development of interventions to decrease STIs.

Racial residential segregation and risky sexual behavior among non-Hispanic blacks, 2006-2010.

PubMed

Lutfi, Khaleeq; Trepka, Mary Jo; Fennie, Kristopher P; Ibanez, Gladys; Gladwin, Hugh

2015-09-01

Sexually transmitted infections (STIs) including human immunodeficiency virus (HIV) have disproportionately affected the non-Hispanic black population in the United States. A person's community can affect his or her STI risk by the community's underlying prevalence of STIs, sexual networks, and social influences on individual behaviors. Racial residential segregation-the separation of racial groups in a residential context across physical environments-is a community factor that has been associated with negative health outcomes. The objective of this study was to examine if non-Hispanic blacks living in highly segregated areas were more likely to have risky sexual behavior. Demographic and sexual risk behavior data from non-Hispanic blacks aged 15-44 years participating in the National Survey of Family Growth were linked to Core-Based Statistical Area segregation data from the U.S. Census Bureau. Five dimensions measured racial residential segregation, each covering a different concept of spatial variation. Multilevel logistic regressions were performed to test the effect of each dimension on sexual risk behavior controlling for demographics and community poverty. Of the 3643 participants, 588 (14.5%) reported risky sexual behavior as defined as two or more partners in the last 12 months and no consistent condom use. Multilevel analysis results show that racial residential segregation was associated with risky sexual behavior with the association being stronger for the centralization [aOR (95% CI)][2.07 (2.05-2.08)] and concentration [2.05 (2.03-2.07)] dimensions. This suggests risky sexual behavior is more strongly associated with neighborhoods with high concentrations of non-Hispanic blacks and an accumulation of non-Hispanic blacks in an urban core. Findings suggest racial residential segregation is associated with risky sexual behavior in non-Hispanic blacks 15-44 years of age with magnitudes varying by dimension. Incorporating additional contextual factors may lead to the development of interventions that promote healthier behaviors and lower rates of HIV and other STIs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Natural experiment examining the longitudinal association between change in residential segregation and youth cardiovascular health across race/ethnicity and gender in the USA.

PubMed

D'Agostino, Emily M; Patel, Hersila H; Ahmed, Zafar; Hansen, Eric; Mathew, M Sunil; Nardi, Maria I; Messiah, Sarah E

2018-05-10

Identifying how racial/ethnic residential segregation and mobility may impact health can guide innovative strategies for reducing youth disparities. This natural experiment examined the association between change in residential segregation and cardiovascular health outcomes across race/ethnicity and gender for youth (n=2250, mean age 9.1 years, 54% male; 51% Hispanic, 49% non-Hispanic black (NHB); 49% high area poverty) attending a multisite park-based afterschool fitness programme in Florida, USA. Two-level generalised linear mixed models with random intercepts for park effects were fit to test the change in segregation-cardiovascular health association over two school years. After covariate adjustment (individual-level gender, race/ethnicity, age, time and park-area poverty), greater improvements in cardiovascular health including body mass index percentile, sum of skinfold thicknesses, systolic/diastolic blood pressure percentiles and 400 m run time were found for youth who attended the program in a less segregated area compared with their home area (p<0.05 for all outcomes). NHB girls showed the greatest cardiovascular health improvements. Specifically, compared with the reference group (no change in segregation), skinfold thicknesses and systolic blood pressure percentiles decreased 17% (incidence rate ratio (IRR) 95% CI 0.81 to 0.86) and 16% (IRR 95% CI 0.82 to 0.87), respectively, versus 1% increase for both outcomes (IRR 95% CI 0.98 to 1.05) and (IRR 95% CI 0.98 to 1.05), respectively, for movement to less versus more segregated areas. In light of a continually expanding youth obesity epidemic, the global effort to reduce health inequities may be supported through Parks and Recreation Departments given potential to expand geographic mobility for low resource subgroups. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

An Investigation of Spatial Hearing in Children with Normal Hearing and with Cochlear Implants and the Impact of Executive Function

NASA Astrophysics Data System (ADS)

Misurelli, Sara M.

The ability to analyze an "auditory scene"---that is, to selectively attend to a target source while simultaneously segregating and ignoring distracting information---is one of the most important and complex skills utilized by normal hearing (NH) adults. The NH adult auditory system and brain work rather well to segregate auditory sources in adverse environments. However, for some children and individuals with hearing loss, selectively attending to one source in noisy environments can be extremely challenging. In a normal auditory system, information arriving at each ear is integrated, and thus these binaural cues aid in speech understanding in noise. A growing number of individuals who are deaf now receive cochlear implants (CIs), which supply hearing through electrical stimulation to the auditory nerve. In particular, bilateral cochlear implants (BICIs) are now becoming more prevalent, especially in children. However, because CI sound processing lacks both fine structure cues and coordination between stimulation at the two ears, binaural cues may either be absent or inconsistent. For children with NH and with BiCIs, this difficulty in segregating sources is of particular concern because their learning and development commonly occurs within the context of complex auditory environments. This dissertation intends to explore and understand the ability of children with NH and with BiCIs to function in everyday noisy environments. The goals of this work are to (1) Investigate source segregation abilities in children with NH and with BiCIs; (2) Examine the effect of target-interferer similarity and the benefits of source segregation for children with NH and with BiCIs; (3) Investigate measures of executive function that may predict performance in complex and realistic auditory tasks of source segregation for listeners with NH; and (4) Examine source segregation abilities in NH listeners, from school-age to adults.

Segregation analysis of prostate cancer in France: evidence for autosomal dominant inheritance and residual brother-brother dependence.

PubMed

Valeri, A; Briollais, L; Azzouzi, R; Fournier, G; Mangin, P; Berthon, P; Cussenot, O; Demenais, F

2003-03-01

Four segregation analyses concerning prostate cancer (CaP), three conducted in the United States and one in Northern Europe, have shown evidence for a dominant major gene but with different parameter estimates. A recent segregation analysis of Australian pedigrees has found a better fit of a two-locus model than single-locus models. This model included a dominantly inherited increased risk that was greater at younger ages and a recessively inherited or X-linked increased risk that was greater at older ages. Recent linkage analyses have led to the detection of at least 8 CaP predisposing genes, suggesting a complex inheritance and genetic heterogeneity. To assess the nature of familial aggregation of prostate cancer in France, segregation analysis was conducted in 691 families ascertained through 691 CaP patients, recruited from three French hospitals and unselected with respect to age at diagnosis, clinical stage or family history. This mode of family inclusion, without any particular selection of the probands, is unique, as probands from all previous analyses were selected according to various criteria. Segregation analysis was carried out using the logistic hazard regressive model, as incorporated in the REGRESS program, which can accommodate a major gene effect, residual familial dependences of any origin (genetic and/or environmental), and covariates, while including survival analysis concepts. Segregation analysis showed evidence for the segregation of an autosomal dominant gene (allele frequency of 0.03%) with an additional brother-brother dependence. The estimated cumulative risks of prostate cancer by age 85 years, among subjects with the at-risk genotype, were 86% in the fathers' generation and 99% in the probands' generation. This study supports the model of Mendelian transmission of a rare autosomal dominant gene with high penetrance, and demonstrates that additional genetic and/or common sibling environmental factors are involved to account for the familial clustering of CaP.

Effect of Heat Treatment on Chemical Segregation in CMSX-4 Nickel-Base Superalloy

NASA Astrophysics Data System (ADS)

Szczotok, A.; Chmiela, B.

2014-08-01

Superalloys display a strong tendency toward chemical segregation during solidification. Therefore, it is of great importance to develop appropriate techniques for the melting and casting of superalloys. Elements partitioning between the γ and γ' phases in single crystal superalloys have been investigated by several authors using electron probe microanalysis (Hemmersmeier and Feller-Kniepmeier Mater Sci Eng A 248:87-97, 1998; Kearsey et al. Intermetallics 12:903-910, 2004; Kearsey et al. Superalloys 2004, pp 801-810, 2004; D'Souza et al. Mater Sci Eng A 490:258-265, 2008). We examined the effect of the particular stages of standard heat treatment (solution treatment and ageing) applied to CMSX-4 single crystal superalloy on chemical segregation that occurs between dendrites and interdendritic areas. Dendritic structures were observed using a scanning electron microscope. Analyses of the chemical composition were performed using energy dispersive x-ray spectroscopy. The obtained qualitative and quantitative results for the concentrations of elements enabled us to confirm the dendritic segregation in as-cast CMSX-4 superalloy. The concentrations of some refractory elements (tungsten, rhenium) were much greater in dendrites than in interdendritic areas. However, these differences in chemical composition gradually decreased during heat treatment. The results obtained in this study warrant further examination of the diffusion processes of elements during heat treatment of the investigated superalloy, and of the kinetics of diffusion.

Habitat degradation may affect niche segregation patterns in lizards

NASA Astrophysics Data System (ADS)

Pelegrin, N.; Chani, J. M.; Echevarria, A. L.; Bucher, E. H.

2013-08-01

Lizards partition resources in three main niche dimensions: time, space and food. Activity time and microhabitat use are strongly influenced by thermal environment, and may differ between species according to thermal requirements and tolerance. As thermal characteristics are influenced by habitat structure, microhabitat use and activity of lizards can change in disturbed habitats. We compared activity and microhabitat use of two abundant lizard species of the Semi-arid Chaco of Argentina between a restored and a highly degraded Chaco forest, to determine how habitat degradation affects lizard segregation in time and space, hypothesizing that as activity and microhabitat use of lizards are related to habitat structure, activity and microhabitat use of individual species can be altered in degraded habitats, thus changing segregation patterns between them. Activity changed from an overlapped pattern in a restored forest to a segregated pattern in a degraded forest. A similar trend was observed for microhabitat use, although to a less extent. No correlation was found between air temperature and lizard activity, but lizard activity varied along the day and among sites. Contrary to what was believed, activity patterns of neotropical diurnal lizards are not fixed, but affected by multiple factors related to habitat structure and possibly to interspecific interactions. Changes in activity patterns and microhabitat use in degraded forests may have important implications when analyzing the effects of climate change on lizard species, due to synergistic effects.

Asymmetric segregation of template DNA strands in basal-like human breast cancer cell lines

PubMed Central

2013-01-01

Background and methods Stem or progenitor cells from healthy tissues have the capacity to co-segregate their template DNA strands during mitosis. Here, we set out to test whether breast cancer cell lines also possess the ability to asymmetrically segregate their template DNA strands via non-random chromosome co-segregation, and whether this ability correlates with certain properties attributed to breast cancer stem cells (CSCs). We quantified the frequency of asymmetric segregation of template DNA strands in 12 human breast cancer cell lines, and correlated the frequency to molecular subtype, CD44+/CD24-/lo phenotype, and invasion/migration ability. We tested if co-culture with human mesenchymal stem cells, which are known to increase self-renewal, can alter the frequency of asymmetric segregation of template DNA in breast cancer. Results We found a positive correlation between asymmetric segregation of template DNA and the breast cancer basal-like and claudin-low subtypes. There was an inverse correlation between asymmetric segregation of template DNA and Her2 expression. Breast cancer samples with evidence of asymmetric segregation of template DNA had significantly increased invasion and borderline significantly increased migration abilities. Samples with high CD44+/CD24-/lo surface expression were more likely to harbor a consistent population of cells that asymmetrically segregated its template DNA; however, symmetric self-renewal was enriched in the CD44+/CD24-/lo population. Co-culturing breast cancer cells with human mesenchymal stem cells expanded the breast CSC pool and decreased the frequency of asymmetric segregation of template DNA. Conclusions Breast cancer cells within the basal-like subtype can asymmetrically segregate their template DNA strands through non-random chromosome segregation. The frequency of asymmetric segregation of template DNA can be modulated by external factors that influence expansion or self-renewal of CSC populations. Future studies to uncover the underlying mechanisms driving asymmetric segregation of template DNA and dictating cell fate at the time of cell division may explain how CSCs are maintained in tumors. PMID:24238140

7 CFR 996.13 - Peanuts.

Code of Federal Regulations, 2014 CFR

2014-01-01

... from visible Aspergillus flavus. (c) Segregation 2. “Segregation 2 peanuts” means farmers stock peanuts... rancidity, mold, or decay and which are free from visible Aspergillus flavus. (d) Segregation 3. “Segregation 3 peanuts” means farmers stock peanuts with visible Aspergillus flavus. ...

7 CFR 996.13 - Peanuts.

Code of Federal Regulations, 2013 CFR

2013-01-01

... from visible Aspergillus flavus. (c) Segregation 2. “Segregation 2 peanuts” means farmers stock peanuts... rancidity, mold, or decay and which are free from visible Aspergillus flavus. (d) Segregation 3. “Segregation 3 peanuts” means farmers stock peanuts with visible Aspergillus flavus. ...

7 CFR 996.13 - Peanuts.

Code of Federal Regulations, 2012 CFR

2012-01-01

... from visible Aspergillus flavus. (c) Segregation 2. “Segregation 2 peanuts” means farmers stock peanuts... rancidity, mold, or decay and which are free from visible Aspergillus flavus. (d) Segregation 3. “Segregation 3 peanuts” means farmers stock peanuts with visible Aspergillus flavus. ...

Loss of sexual recombination and segregation is associated with increased diversification in evening primroses.

PubMed

Johnson, Marc T J; Fitzjohn, Richard G; Smith, Stacey D; Rausher, Mark D; Otto, Sarah P

2011-11-01

The loss of sexual recombination and segregation in asexual organisms has been portrayed as an irreversible process that commits asexually reproducing lineages to reduced diversification. We test this hypothesis by estimating rates of speciation, extinction, and transition between sexuality and functional asexuality in the evening primroses. Specifically, we estimate these rates using the recently developed BiSSE (Binary State Speciation and Extinction) phylogenetic comparative method, which employs maximum likelihood and Bayesian techniques. We infer that net diversification rates (speciation minus extinction) in functionally asexual evening primrose lineages are roughly eight times faster than diversification rates in sexual lineages, largely due to higher speciation rates in asexual lineages. We further reject the hypothesis that a loss of recombination and segregation is irreversible because the transition rate from functional asexuality to sexuality is significantly greater than zero and in fact exceeded the reverse rate. These results provide the first empirical evidence in support of the alternative theoretical prediction that asexual populations should instead diversify more rapidly than sexual populations because they are free from the homogenizing effects of sexual recombination and segregation. Although asexual reproduction may often constrain adaptive evolution, our results show that the loss of recombination and segregation need not be an evolutionary dead end in terms of diversification of lineages. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

PP2A(Cdc55)'s role in reductional chromosome segregation during achiasmate meiosis in budding yeast is independent of its FEAR function.

PubMed

Kerr, Gary W; Wong, Jin Huei; Arumugam, Prakash

2016-07-26

PP2A(Cdc55) is a highly conserved serine-threonine protein phosphatase that is involved in diverse cellular processes. In budding yeast, meiotic cells lacking PP2A(Cdc55) activity undergo a premature exit from meiosis I which results in a failure to form bipolar spindles and divide nuclei. This defect is largely due to its role in negatively regulating the Cdc Fourteen Early Anaphase Release (FEAR) pathway. PP2A(Cdc55) prevents nucleolar release of the Cdk (Cyclin-dependent kinase)-antagonising phosphatase Cdc14 by counteracting phosphorylation of the nucleolar protein Net1 by Cdk. CDC55 was identified in a genetic screen for monopolins performed by isolating suppressors of spo11Δ spo12Δ lethality suggesting that Cdc55 might have a role in meiotic chromosome segregation. We investigated this possibility by isolating cdc55 alleles that suppress spo11Δ spo12Δ lethality and show that this suppression is independent of PP2A(Cdc55)'s FEAR function. Although the suppressor mutations in cdc55 affect reductional chromosome segregation in the absence of recombination, they have no effect on chromosome segregation during wild type meiosis. We suggest that Cdc55 is required for reductional chromosome segregation during achiasmate meiosis and this is independent of its FEAR function.

Multimodal effects of small molecule ROCK and LIMK inhibitors on mitosis, and their implication as anti-leukemia agents.

PubMed

Oku, Yusuke; Tareyanagi, Chiaki; Takaya, Shinichi; Osaka, Sayaka; Ujiie, Haruki; Yoshida, Kentaro; Nishiya, Naoyuki; Uehara, Yoshimasa

2014-01-01

Accurate chromosome segregation is vital for cell viability. Many cancer cells show chromosome instability (CIN) due to aberrant expression of the genes involved in chromosome segregation. The induction of massive chromosome segregation errors in such cancer cells by small molecule inhibitors is an emerging strategy to kill these cells selectively. Here we screened and characterized small molecule inhibitors which cause mitotic chromosome segregation errors to target cancer cell growth. We screened about 300 chemicals with known targets, and found that Rho-associated coiled-coil kinase (ROCK) inhibitors bypassed the spindle assembly checkpoint (SAC), which delays anaphase onset until proper kinetochore-microtubule interactions are established. We investigated how ROCK inhibitors affect chromosome segregation, and found that they induced microtubule-dependent centrosome fragmentation. Knockdown of ROCK1 and ROCK2 revealed their additive roles in centrosome integrity. Pharmacological inhibition of LIMK also induced centrosome fragmentation similar to that by ROCK inhibitors. Inhibition of ROCK or LIMK hyper-stabilized mitotic spindles and impaired Aurora-A activation. These results suggested that ROCK and LIMK are directly or indirectly involved in microtubule dynamics and activation of Aurora-A. Furthermore, inhibition of ROCK or LIMK suppressed T cell leukemia growth in vitro, but not peripheral blood mononuclear cells. They induced centrosome fragmentation and apoptosis in T cell leukemia cells. These results suggested that ROCK and LIMK can be a potential target for anti-cancer drugs.

The segregation of baryons and dark matter during halo assembly

NASA Astrophysics Data System (ADS)

Liao, Shihong; Gao, Liang; Frenk, Carlos S.; Guo, Qi; Wang, Jie

2017-09-01

The standard galaxy formation theory assumes that baryons and dark matter are initially well mixed before becoming segregated due to radiative cooling. We use non-radiative hydrodynamical simulations to explicitly examine this assumption and find that baryons and dark matter can also be segregated due to different characteristics of gas and dark matter during the buildup of the halo. As a result, baryons in many haloes do not originate from the same Lagrangian region as the dark matter. When using the fraction of corresponding dark matter and gas particles in the initial conditions (the 'paired fraction') as a proxy of the dark matter and gas segregation strength of a halo, on average about 25 per cent of the baryonic and dark matter of the final halo are segregated in the initial conditions. This is at odds with the assumption of the standard galaxy formation model. A consequence of this effect is that the baryons and dark matter of the same halo initially experience different tidal torques and thus their angular momentum vectors are often misaligned. The degree of the misalignment is largely preserved during later halo assembly and can be understood with the tidal torque theory. The result challenges the precision of some semi-analytical approaches that utilize dark matter halo merger trees to infer properties of gas associated with dark matter haloes.

Electromigration Critical Product to Measure Effect of Underfill Material in Suppressing Bi Segregation in Sn-58Bi Solder

NASA Astrophysics Data System (ADS)

Zhao, Xu; Takaya, Satoshi; Muraoka, Mikio

2017-08-01

Recently, we detected length-dependent electromigration (EM) behavior in Sn-58Bi (SB) solder and revealed the existence of Bi back-flow, which retards EM-induced Bi segregation and is dependent on solder length. The cause of the back-flow is attributed to an oxide layer formed on the SB solder. At present, underfill (UF) material is commonly used in flip-chip packaging as filler between chip and substrate to surround solder bumps. In this study, we quantitatively investigated the effect of UF material as a passivation layer on EM in SB solder strips. EM tests on SB solder strips with length of 50 μm, 100 μm, and 150 μm were conducted simultaneously. Some samples were coated with commercial thermosetting epoxy UF material, which acted as a passivation layer on the Cu-SB-Cu interconnections. The value of the critical product for SB solder was estimated to be 38 A/cm to 43 A/cm at 353 K to 373 K without UF coating and 59 A/cm at 373 K with UF coating. The UF material acting as a passivation layer suppressed EM-induced Bi segregation and increased the threshold current density by 37% to 55%. However, at very high current density, this effect became very slight. In addition, Bi atoms can diffuse to the anode side through the Sn phase, hence addition of microelements to the Sn phase to form obstacles, such as intermetallic compounds, may retard Bi segregation in SB solder.

The pedogeochemical segregation a few horizons in soils from glass houses

NASA Astrophysics Data System (ADS)

Bulgariu, Dumitru; Rusu, Constantin; Filipov, Feodor; Buzgar, Nicolae; Bulgariu, Laura

2010-05-01

Our studies have focused the apparition and manifestation conditions of pedogeochemical segregation phenomena in case of soils from Copou - Iaşi, Bacău and Bârlad (Romania) glass house, and the effects of this on the pedogeochemical and agrochemical characteristics of soils from glass houses cultivated with vegetables. The utilization of intensive cultivation technologies of vegetables in glass houses determined the degradation of morphological, physical and chemical characteristics of soils, by rapid evolution of salted processes (salinization and / or sodization), compaction, carbonatation, eluviation-illuviation, frangipane formation, stagnogleization, gleization etc. Under these conditions, at depth of 30-40 cm is formed a compact and impenetrable horizon - Ahok(x) horizon. In function of exploitation conditions and by the chemical-mineralogical characteristics of soils from glasshouses, the Ahok horizons can have frangipane properties, expressed more or less. These horizons determined a geochemical segregation of soils from glass houses: (i) superior horizons, above Ahok(x) horizon evolve in weak oxidative conditions, weak alkaline pH, higher salinity, humidity and temperature; (ii) inferior horizons, below Ahok(x) horizon evolve in weak reducing conditions weak acid pH, lower salinity, humidity and temperature. Concomitant with the development of Ahok(x) horizons, the rapid degradation of the properties of soils from glasshouses is observed. The aspects about the formation of frangipane horizon in soils from glasshouses are not yet sufficiently know. Whatever of the formation processes, the frangipane horizons determined a sever segregation in pedogeochemical evolution of soils from glass houses, with very important consequences on the agrochemical quality of these soils. The segregation effects are manifested in the differential dynamics of pedogeochemical processes from superior horizons (situated above the segregation horizon), in comparison with the inferior horizons (situated below the segregation horizon), and in global evolution of degradation processes of soils from glasshouses. The results obtained by as have shown that together by mobile forms of Si, Al and Fe, at the formation of segregation horizons (frangipane), an important role has the phosphorus (organic. in special) and the organic-mineral complexes, respectively. The experimental results indicate a strong accumulation tendency, at the level of pedogeochemical segregation horizons - Ahok(x) horizons, of fin grain-size fractions and of amorphous forms of mineral components. Also, was observed that in the composition of soil aggregates from frangipane horizon, and important weight have the smectites, amorphous iron oxides and oxy-hydroxides, amorphous silica and organic matter. The particularity of pedogeochemical segregation horizon (frangipane) from Copou-Iaşi glass house is given by the relatively high contents of: (i) phosphorus - organic, in special, as inositol-phosphoric esters; (ii) fulvic acids; (iii) organic-mineral complexes - with special composition and structure, and (iv) poly-metha-phosphate associated with aluminosilicated gel - from chemical point of view has the characteristics of a pseudo-solid solution by (SiO2)x(Al2O3)y(PO4)z type, where x / z = (10-16) / 1, and y / z = (3-5) / 1); this appear as nodular depositions ( = 3-5 mm) covered with thin iron-carbonated crust. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51-045/07).

Twenty Years after Brown: Where Are We Now?

ERIC Educational Resources Information Center

Edelman, Marian Wright

1974-01-01

To resolve the basic question of what is unconstitutional school segregation, lawyer Edelman suggests bombarding the citadel of de facto segregation with a legal strategy that expands the definition of de jure segregation to include acts that produce segregation in fact. (Editor)

49 CFR 175.78 - Stowage compatibility of cargo.

Code of Federal Regulations, 2010 CFR

2010-10-01

... leakage. (b) At a minimum, the segregation instructions prescribed in the following Segregation Table must be followed to maintain acceptable segregation between packages containing hazardous materials with different hazards. The Segregation Table instructions apply whether or not the class or division is the...

Repair rather than segregation of damage is the optimal unicellular aging strategy.

PubMed

Clegg, Robert J; Dyson, Rosemary J; Kreft, Jan-Ulrich

2014-08-16

How aging, being unfavourable for the individual, can evolve is one of the fundamental problems of biology. Evidence for aging in unicellular organisms is far from conclusive. Some studies found aging even in symmetrically dividing unicellular species; others did not find aging in the same, or in different, unicellular species, or only under stress. Mathematical models suggested that segregation of non-genetic damage, as an aging strategy, would increase fitness. However, these models failed to consider repair as an alternative strategy or did not properly account for the benefits of repair. We used a new and improved individual-based model to examine rigorously the effect of a range of aging strategies on fitness in various environments. Repair of damage emerges as the best strategy despite its fitness costs, since it immediately increases growth rate. There is an optimal investment in repair that outperforms damage segregation in well-mixed, lasting and benign environments over a wide range of parameter values. Damage segregation becomes beneficial, and only in combination with repair, when three factors are combined: (i) the rate of damage accumulation is high, (ii) damage is toxic and (iii) efficiency of repair is low. In contrast to previous models, our model predicts that unicellular organisms should have active mechanisms to repair damage rather than age by segregating damage. Indeed, as predicted, all organisms have evolved active mechanisms of repair whilst aging in unicellular organisms is absent or minimal under benign conditions, apart from microorganisms with a different ecology, inhabiting short-lived environments strongly favouring early reproduction rather than longevity. Aging confers no fitness advantage for unicellular organisms in lasting environments under benign conditions, since repair of non-genetic damage is better than damage segregation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Brien, Christopher J.; Foiles, Stephen M.

Low-mobility twin grain boundaries dominate the microstructure of grain boundary-engineered materials and are critical to understanding their plastic deformation behaviour. The presence of solutes, such as hydrogen, has a profound effect on the thermodynamic stability of the grain boundaries. This work examines the case of a Σ3 grain boundary at inclinations from 0° ≤ Φ ≤ 90°. The angle Φ corresponds to the rotation of the Σ3 (1 1 1) < 1 1 0 > (coherent) into the Σ3 (1 1 2) < 1 1 0 > (lateral) twin boundary. To this end, atomistic models of inclined grain boundaries, utilisingmore » empirical potentials, are used to elucidate the finite-temperature boundary structure while grand canonical Monte Carlo models are applied to determine the degree of hydrogen segregation. In order to understand the boundary structure and segregation behaviour of hydrogen, the structural unit description of inclined twin grain boundaries is found to provide insight into explaining the observed variation of excess enthalpy and excess hydrogen concentration on inclination angle, but the explanatory power is limited by how the enthalpy of segregation is affected by hydrogen concentration. At higher concentrations, the grain boundaries undergo a defaceting transition. In order to develop a more complete mesoscale model of the interfacial behaviour, an analytical model of boundary energy and hydrogen segregation that relies on modelling the boundary as arrays of discrete 1/3 < 1 1 1 > disconnections is constructed. Lastly, the complex interaction of boundary reconstruction and concentration-dependent segregation behaviour exhibited by inclined twin grain boundaries limits the range of applicability of such an analytical model and illustrates the fundamental limitations for a structural unit model description of segregation in lower stacking fault energy materials.« less

Dynamics of Transformation from Segregation to Mixed Wealth Cities

PubMed Central

Sahasranaman, Anand; Jensen, Henrik Jeldtoft

2016-01-01

We model the dynamics of a variation of the Schelling model for agents described simply by a continuously distributed variable—wealth. Agent movement is not dictated by agent choice as in the classic Schelling model, but by their wealth status. Agents move to neighborhoods where their wealth is not lesser than that of some proportion of their neighbors, the threshold level. As in the case of the classic Schelling model, we find here that wealth-based segregation occurs and persists. However, introducing uncertainty into the decision to move—that is, with some probability, if agents are allowed to move even though the threshold condition is contravened—we find that even for small proportions of such disallowed moves, the dynamics no longer yield segregation but instead sharply transition into a persistent mixed wealth distribution, consistent with empirical findings of Benenson, Hatna, and Or. We investigate the nature of this sharp transformation, and find that it is because of a non-linear relationship between allowed moves (moves where threshold condition is satisfied) and disallowed moves (moves where it is not). For small increases in disallowed moves, there is a rapid corresponding increase in allowed moves (before the rate of increase tapers off and tends to zero), and it is the effect of this non-linearity on the dynamics of the system that causes the rapid transition from a segregated to a mixed wealth state. The contravention of the tolerance condition, sanctioning disallowed moves, could be interpreted as public policy interventions to drive de-segregation. Our finding therefore suggests that it might require limited, but continually implemented, public intervention—just sufficient to enable a small, persistently sustained fraction of disallowed moves so as to trigger the dynamics that drive the transformation from a segregated to mixed equilibrium. PMID:27861578

Effect of Boron Microalloying Element on Susceptibility to Hydrogen Embrittlement in High Strength Mooring Chain Steel

NASA Astrophysics Data System (ADS)

Li, H.; Cheng, X. Y.; Shen, H. P.; Su, L. C.; Zhang, S. Y.

The susceptibility to hydrogen embrittlement in high strength mooring chain steel with different boron content (0, 0.003 %, 0.008 %) were investigated by electrochemical hydrogen charging technique and tensile test. The results revealed that appropriate boron content can effectively depress hydrogen induced embrittlement. Precharged with a low current density, this effect seemed to be unobvious. It gradually became clearly with the increasing current density. The increase of resistance to the hydrogen embrittlement for 3B and 8B after adding appropriate boron was attributed to three facts. The first was that the segregation of boron atoms along grain boundaries reduced the grain boundary segregation of phosphorus, which prohibited hydrogen concentration at the grain boundaries, depressing the possibility of the intergranular fracture due to H. The second was that the segregation of boron increased intergranular cohesion, enhanced grain boundary strength, and refined the final microstructure. The third was that the addition of boron changed the state of hydrogen traps, leading to the small amount of diffusible hydrogen. That is to say, hydrogen transferred to these defects by dislocations was accordingly decreased, which led to the low sensitive of hydrogen induced cracking.

Identification of a new allele of Es-I segregating in an inbred strain of mice.

PubMed

Soares, E R

1979-08-01

A new allele of Es-1, designated Es-1e, has been identified in the mouse. This allele was discovered segregating among the progeny of a strain DBA/2J male and is apparently the result of a spontaneous mutation within this strain. Genetic analyses have shown that this mutation is heritable and, further, that both heterozygous and homozygous progeny are viable and fertile. To date, no discernible deleterious effects have been identified as associated with this mutation.

Robertsonian translocations

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1993-12-31

Chapter 27, describes the occurrence of Robertsonian translocations (RTs), which refer to the recombination of whole chromosome arms, in both monocentric and dicentric chromosomes. The nonrandom participation of acrocentric chromosomes in RTs is documented by various methods, including unbiased ascertainment and ascertainment through trisomy, infertility, unspecified mental retardation, and Prader-Willi syndrome. Causes of nonrandom participation of chromosomes in RTs is presented, as are the following topics: segregation in carriers of RTs and segregation in sperm cells of RT carriers, interchromosomal effects and conclusions. 48 refs., 3 figs., 2 tabs.

18 CFR 401.113 - Segregable materials.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 18 Conservation of Power and Water Resources 2 2010-04-01 2010-04-01 false Segregable materials. 401.113 Section 401.113 Conservation of Power and Water Resources DELAWARE RIVER BASIN COMMISSION... Segregable materials. Any reasonably segregable portion of a record shall be provided to any person...

18 CFR 401.113 - Segregable materials.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 18 Conservation of Power and Water Resources 2 2013-04-01 2012-04-01 true Segregable materials. 401.113 Section 401.113 Conservation of Power and Water Resources DELAWARE RIVER BASIN COMMISSION... Segregable materials. Any reasonably segregable portion of a record shall be provided to any person...

18 CFR 401.113 - Segregable materials.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 18 Conservation of Power and Water Resources 2 2014-04-01 2014-04-01 false Segregable materials. 401.113 Section 401.113 Conservation of Power and Water Resources DELAWARE RIVER BASIN COMMISSION... Segregable materials. Any reasonably segregable portion of a record shall be provided to any person...

18 CFR 401.113 - Segregable materials.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 18 Conservation of Power and Water Resources 2 2012-04-01 2012-04-01 false Segregable materials. 401.113 Section 401.113 Conservation of Power and Water Resources DELAWARE RIVER BASIN COMMISSION... Segregable materials. Any reasonably segregable portion of a record shall be provided to any person...

49 CFR 176.708 - Segregation distances.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Segregation distances. 176.708 Section 176.708... Requirements for Radioactive Materials § 176.708 Segregation distances. (a) Table IV lists minimum separation... into account any relocation of cargo during the voyage. (e) Any departure from the segregation...

49 CFR 176.145 - Segregation in single hold vessels.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Segregation in single hold vessels. 176.145 Section 176.145 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS... VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.145 Segregation in...

43 CFR 2091.07 - Principles.

Code of Federal Regulations, 2011 CFR

2011-10-01

... OF THE INTERIOR LAND RESOURCE MANAGEMENT (2000) SPECIAL LAWS AND RULES Segregation and Opening of... the Geothermal Steam Act, if so specified in the document that segregates the lands. The segregation... are required when the opening date is not specified in the document creating the segregation, or when...

49 CFR 176.145 - Segregation in single hold vessels.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Segregation in single hold vessels. 176.145 Section 176.145 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS... VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.145 Segregation in...

High-temperature X-ray diffraction study of crystallization and phase segregation on spinel-type lithium manganese oxides

NASA Astrophysics Data System (ADS)

Komaba, Shinichi; Yabuuchi, Naoaki; Ikemoto, Sachi

2010-01-01

To study crystallization process of spinel-type Li 1+xMn 2-xO 4, in-situ high-temperature X-ray diffraction technique (HT-XRD) was utilized for the mixture consisting of Li 2CO 3 and Mn 2O 3 as starting material in the temperature range of 25-700 °C. In-situ HT-XRD analysis directly revealed that crystallization process of Li 1+xMn 2-xO 4 was significantly affected by the difference in the Li/Mn molar ratio in the precursor. Single phase of stoichiometric LiMn 2O 4 formed at 700 °C. The formation of single phase of spinel was achieved at the lower temperature than the stoichiometric sample as Li/Mn molar ratio in the precursor increased. Lattice parameter of the stoichiometric LiMn 2O 4 at 25 °C was 8.24 Å and expanded to 8.31 Å at 700 °C, which corresponds to the approximately 3% expansion in the unit cell volume. From the slope of the lattice parameter change as a function of temperatures, linear thermal expansion coefficient of the stoichiometric LiMn 2O 4 was calculated to be 1.2×10 -5 °C -1 in this temperature range. When the Li/Mn molar ratio in Li 1+xMn 2-xO 4 increased ( x > 0.1), the spinel phase segregated into the Li 1+yMn 2-yO 4 ( x > y) and Li 2MnO 3 during heating, which involved the oxygen loss from the materials. During the cooling process from 700 °C, and the segregated phase merged into Li 1+xMn 2-xO 4 with oxygen incorporation. Such trend directly observed by in-situ HT-XRD was supported by thermal gravimetric analysis as reversible weight (oxygen) loss/gain at higher temperature (500-700 °C).

Evolution and development of model membranes for physicochemical and functional studies of the membrane lateral heterogeneity.

PubMed

Morigaki, Kenichi; Tanimoto, Yasushi

2018-03-14

One of the main questions in the membrane biology is the functional roles of membrane heterogeneity and molecular localization. Although segregation and local enrichment of protein/lipid components (rafts) have been extensively studied, the presence and functions of such membrane domains still remain elusive. Along with biochemical, cell observation, and simulation studies, model membranes are emerging as an important tool for understanding the biological membrane, providing quantitative information on the physicochemical properties of membrane proteins and lipids. Segregation of fluid lipid bilayer into liquid-ordered (Lo) and liquid-disordered (Ld) phases has been studied as a simplified model of raft in model membranes, including giant unilamellar vesicles (GUVs), giant plasma membrane vesicles (GPMVs), and supported lipid bilayers (SLB). Partition coefficients of membrane proteins between Lo and Ld phases were measured to gauze their affinities to lipid rafts (raftophilicity). One important development in model membrane is patterned SLB based on the microfabrication technology. Patterned Lo/Ld phases have been applied to study the partition and function of membrane-bound molecules. Quantitative information of individual molecular species attained by model membranes is critical for elucidating the molecular functions in the complex web of molecular interactions. The present review gives a short account of the model membranes developed for studying the lateral heterogeneity, especially focusing on patterned model membranes on solid substrates. Copyright © 2018 Elsevier B.V. All rights reserved.

Local Residential Segregation Matters: Stronger Association of Census Tract Compared to Conventional City-Level Measures with Fatal and Non-Fatal Assaults (Total and Firearm Related), Using the Index of Concentration at the Extremes (ICE) for Racial, Economic, and Racialized Economic Segregation, Massachusetts (US), 1995-2010.

PubMed

Krieger, Nancy; Feldman, Justin M; Waterman, Pamela D; Chen, Jarvis T; Coull, Brent A; Hemenway, David

2017-04-01

Research on residential segregation and health, primarily conducted in the USA, has chiefly employed city or regional measures of racial segregation. To test our hypothesis that stronger associations would be observed using local measures, especially for racialized economic segregation, we analyzed risk of fatal and non-fatal assault in Massachusetts (1995-2010), since this outcome is strongly associated with residential segregation. The segregation metrics comprised the Index of Concentration at the Extremes (ICE), the Index of Dissimilarity, and poverty rate, with measures computed at both the census tract and city/town level. Key results were that larger associations between fatal and non-fatal assaults and residential segregation occurred for models using the census tract vs. city/town measures, with the greatest associations observed for racialized economic segregation. For fatal assaults, comparing the bottom vs. top quintiles, the incidence rate ratio (and 95% confidence interval (CI)) in models using the census tract measures equaled 3.96 (95% CI 3.10, 5.06) for the ICE for racialized economic segregation, 3.26 (95% CI 2.58, 4.14) for the ICE for income, 3.14 (95% CI 2.47, 3.99) for poverty, 2.90 (95% CI 2.21, 3.81) for the ICE for race/ethnicity, and only 0.93 (95% CI 0.79, 1.11) for the Index of Dissimilarity; in models that included both census tract and city/town ICE measures, this risk ratio for the ICE for racialized economic segregation was higher at the census tract (3.29; 95% CI 2.43, 4.46) vs. city/town level (1.61; 95% CI 1.12, 2.32). These results suggest that, at least in the case of fatal and non-fatal assaults, research on residential segregation should employ local measures, including of racialized economic segregation, to avoid underestimating the adverse impact of segregation on health.

C-Cr segregation at grain boundary before the carbide nucleation in Alloy 690

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Hui, E-mail: huili@shu.edu.cn; Laboratory for Microstructures, Shanghai University, Shanghai, 200444; Xia Shuang

2012-04-15

The grain boundary segregation in Alloy 690 was investigated by atom probe tomography. B, C and Si segregated at the grain boundary. The high concentration regions for each segregation element form a set of straight arrays that are parallel to each other in the grain boundary plane. The concentration fluctuation has a periodicity of about 7 nm in the grain boundary plane. Before the Cr{sub 23}C{sub 6} nucleation at grain boundaries, the C-Cr co-segregate on one side of the grain boundaries while not the exact grain boundary core regions have been detected. The reasons why grain boundary carbides have coherentmore » orientation relationship only with one side of nearby grain which grain boundary is located at high index crystal plane were discussed. - Highlights: Black-Right-Pointing-Pointer Grain boundary segregation in Alloy 690 was investigated by atom probe tomography. Black-Right-Pointing-Pointer B, C and Si segregate at the grain boundary. Black-Right-Pointing-Pointer Concentration of segregated atoms periodicity fluctuated in the grain boundary plane. Black-Right-Pointing-Pointer C and Cr co-segregate on one side of the grain boundary before carbide nucleation.« less

How Segregation Makes Us Fat: Food Behaviors and Food Environment as Mediators of the Relationship Between Residential Segregation and Individual Body Mass Index.

PubMed

Goodman, Melody; Lyons, Sarah; Dean, Lorraine T; Arroyo, Cassandra; Hipp, James Aaron

2018-01-01

Racial residential segregation affects food landscapes that dictate residents' food environments and is associated with obesity risk factors, including individual dietary patterns and behaviors. We examine if food behaviors and environments mediate the association between segregation and body mass index (BMI). Non-Hispanic Whites and Blacks living in the St. Louis and Kansas City metro regions from 2012 to 2013 were surveyed on dietary behaviors, food environment, and BMI ( n  = 1,412). These data were combined with the CDC's modified retail food environment index and 2012 American Community Survey data to calculate racial segregation using various evenness and exposure indices. Multi-level mediation analyses were conducted to determine if dietary behavior and food environment mediate the association between racial residential segregation and individual BMI. The positive association between racial segregation and individual BMI is partially mediated by dietary behaviors and fully mediated by food environments. Racial segregation (evenness and exposure) is associated with BMI, mediated by dietary behaviors and food environment. Elements of the food environment, which form the context for dietary behaviors, are potential targets for interventions to reduce obesity in residentially segregated areas.

Health Care Waste Segregation Behavior among Health Workers in Uganda: An Application of the Theory of Planned Behavior.

PubMed

Akulume, Martha; Kiwanuka, Suzanne N

2016-01-01

Objective . The goal of this study was to assess the appropriateness of the theory of planned behavior in predicting health care waste segregation behaviors and to examine the factors that influence waste segregation behaviors. Methodology . One hundred and sixty-three health workers completed a self-administered questionnaire in a cross-sectional survey that examined the theory of planned behavior constructs (attitudes, subjective norms, perceived behavioral control, and intention) and external variables (sociodemographic factors, personal characteristics, organizational characteristics, professional characteristics, and moral obligation). Results . For their most recent client 21.5% of the health workers reported that they most definitely segregated health care waste while 5.5% did not segregate. All the theory of planned behavior constructs were significant predictors of health workers' segregation behavior, but intention emerged as the strongest and most significant ( r = 0.524, P < 0.001). The theory of planned behavior model explained 52.5% of the variance in health workers' segregation behavior. When external variables were added, the new model explained 66.7% of the variance in behavior. Conclusion . Generally, health workers' health care waste segregation behavior was high. The theory of planned behavior significantly predicted health workers' health care waste segregation behaviors.

Sequential stream segregation in normally-hearing and cochlear-implant listenersa)

PubMed Central

Tejani, Viral D.; Schvartz-Leyzac, Kara C.; Chatterjee, Monita

2017-01-01

Sequential stream segregation by normal hearing (NH) and cochlear implant (CI) listeners was investigated using an irregular rhythm detection (IRD) task. Pure tones and narrowband noises of different bandwidths were presented monaurally to older and younger NH listeners via headphones. For CI users, stimuli were delivered as pure tones via soundfield and via direct electrical stimulation. Results confirmed that tonal pitch is not essential for stream segregation by NH listeners and that aging does not reduce NH listeners' stream segregation. CI listeners' stream segregation was significantly poorer than NH listeners' with pure tone stimuli. With direct stimulation, however, CI listeners showed significantly stronger stream segregation, with a mean normalized pattern similar to NH listeners, implying that the CI speech processors possibly degraded acoustic cues. CI listeners' performance on an electrode discrimination task indicated that cues that are salient enough to make two electrodes highly discriminable may not be sufficiently salient for stream segregation, and that gap detection/discrimination, which must depend on perceptual electrode differences, did not play a role in the IRD task. Although the IRD task does not encompass all aspects of full stream segregation, these results suggest that some CI listeners may demonstrate aspects of stream segregation. PMID:28147600

Mixing and diffusion in a two-type population.

PubMed

Izquierdo, Segismundo S; Izquierdo, Luis R; López-Pintado, Dunia

2018-02-01

The outbreak of epidemics, the rise of religious radicalization or the motivational influence of fellow students in classrooms are some of the issues that can be described as diffusion processes in heterogeneous groups. Understanding the role that interaction patterns between groups (e.g. homophily or segregation) play in the diffusion of certain traits or behaviours is a major challenge for contemporary societies. Here, we study the impact on diffusion processes of mixing (or, alternatively, segregating) two groups that present different sensitivities or propensities to contagion. We find non-monotonic effects of mixing and inefficient segregation levels, i.e. situations where a change in the mixing level can benefit both groups, e.g. where an increase in the mixing level can reduce the expected contagion levels in both groups. These findings can have fundamental consequences for the design of inclusion policies.

Mixing and diffusion in a two-type population

PubMed Central

López-Pintado, Dunia

2018-01-01

The outbreak of epidemics, the rise of religious radicalization or the motivational influence of fellow students in classrooms are some of the issues that can be described as diffusion processes in heterogeneous groups. Understanding the role that interaction patterns between groups (e.g. homophily or segregation) play in the diffusion of certain traits or behaviours is a major challenge for contemporary societies. Here, we study the impact on diffusion processes of mixing (or, alternatively, segregating) two groups that present different sensitivities or propensities to contagion. We find non-monotonic effects of mixing and inefficient segregation levels, i.e. situations where a change in the mixing level can benefit both groups, e.g. where an increase in the mixing level can reduce the expected contagion levels in both groups. These findings can have fundamental consequences for the design of inclusion policies. PMID:29515903

Magneto-Hydrodynamic Damping of Convection During Vertical Bridgman-Stockbarger Growth of HgCdTe

NASA Technical Reports Server (NTRS)

Watring, D. A.; Lehoczky, S. L.

1996-01-01

In order to quantify the effects of convection on segregation, Hg(0.8)Cd(0.2)Te crystals were grown by the vertical Bridgman-Stockbarger method in the presence of an applied axial magnetic field of 50 kG. The influence of convection, by magneto-hydrodynamic damping, on mass transfer in the melt and segregation at the solid-liquid interface was investigated by measuring the axial and radial compositional variations in the grown samples. The reduction of convective mixing in the melt through the application of the magnetic field is found to decrease radial segregation to the diffusion-limited regime. It was also found that the suppression of the convective cell near the solid-liquid interface results in an increase in the slope of the diffusion-controlled solute boundary layer, which can lead to constitutional supercooling.

27 CFR 24.27 - Segregation of operations.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Segregation of operations. 24.27 Section 24.27 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... Segregation of operations. The appropriate TTB officer may require the proprietor to segregate operations...

27 CFR 24.27 - Segregation of operations.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Segregation of operations. 24.27 Section 24.27 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... Segregation of operations. The appropriate TTB officer may require the proprietor to segregate operations...

28 CFR 541.24 - Disciplinary segregation status.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 28 Judicial Administration 2 2011-07-01 2011-07-01 false Disciplinary segregation status. 541.24... INMATE DISCIPLINE AND SPECIAL HOUSING UNITS Special Housing Units § 541.24 Disciplinary segregation status. You may be placed in disciplinary segregation status only by the DHO as a disciplinary sanction. ...

Racial and Ethnic Residential Segregation, the Neighborhood Socioeconomic Environment, and Obesity Among Blacks and Mexican Americans

PubMed Central

Kershaw, Kiarri N.; Albrecht, Sandra S.; Carnethon, Mercedes R.

2013-01-01

We used cross-sectional data on 2,660 black and 2,611 Mexican-American adult participants in the National Health and Nutrition Examination Survey (1999–2006) to investigate the association between metropolitan-level racial/ethnic residential segregation and obesity and to determine whether it was mediated by the neighborhood socioeconomic environment. Residential segregation was measured using the black and Hispanic isolation indices. Neighborhood poverty and negative income incongruity were assessed as mediators. Multilevel Poisson regression with robust variance estimates was used to estimate prevalence ratios. There was no relationship between segregation and obesity among men. Among black women, in age-, nativity-, and metropolitan demographic-adjusted models, high segregation was associated with a 1.29 (95% confidence interval (CI): 1.00, 1.65) times higher obesity prevalence than was low segregation; medium segregation was associated with a 1.35 (95% CI: 1.07, 1.70) times higher obesity prevalence. Mexican-American women living in high versus low segregation areas had a significantly lower obesity prevalence (prevalence ratio, 0.54; 95% CI: 0.33, 0.90), but there was no difference between those living in medium versus low segregation areas. These associations were not mediated by neighborhood poverty or negative income incongruity. These findings suggest variability in the interrelationships between residential segregation and obesity for black and Mexican-American women. PMID:23337312

Do Diabetic Patients Living in Racially Segregated Neighborhoods Experience Different Access and Quality of Care?

PubMed Central

Chan, Kitty S.; Gaskin, Darrell J.; Dinwiddie, Gniesha Y.; McCleary, Rachael

2012-01-01

Background Place of residence, particularly residential segregation, has been implicated in health and health care disparities. However, prior studies have not focused on care for diabetes, a prevalent condition for minority populations. Objective To examine the association of residential segregation with a range of access and quality of care outcomes among Black and Hispanic diabetics using a nationally representative U.S. sample. Research Design Cross-sectional study using data for 1598 adult diabetics from the 2006 Medical Expenditure Panel Survey (MEPS) linked to residential segregation information for Blacks and Hispanics based on the 2000 census. Relationships of five dimensions of residential segregation (dissimilarity, isolation, clustering, concentration and centralization) with access and quality of care outcomes were examined using linear, logistic and multinomial logistic regression models, controlling for respondent characteristics and community utilization and hospital capacity. Results Black and Hispanic diabetics had comparable or better access to providers, but received fewer recommended services. Living in a segregated community was associated with more recommended services received, but also problems with seeing a specialist. The relationship of residential segregation to diabetes care varied depending on type of segregation and race/ethnic group assessed. Conclusions Residential segregation influences the care experience of diabetics in the U.S. Our study highlights the importance of investigating how different types of segregation may affect diabetes care received by patients from different race and ethnic groups. PMID:22525608

46 CFR 148.155 - Stowage and segregation for potentially dangerous materials.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Stowage and segregation for potentially dangerous...) DANGEROUS CARGOES CARRIAGE OF BULK SOLID MATERIALS THAT REQUIRE SPECIAL HANDLING Stowage and Segregation § 148.155 Stowage and segregation for potentially dangerous materials. (a) A PDM must be stowed and...

46 CFR 148.155 - Stowage and segregation for potentially dangerous materials.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Stowage and segregation for potentially dangerous...) DANGEROUS CARGOES CARRIAGE OF BULK SOLID MATERIALS THAT REQUIRE SPECIAL HANDLING Stowage and Segregation § 148.155 Stowage and segregation for potentially dangerous materials. (a) A PDM must be stowed and...

46 CFR 148.155 - Stowage and segregation for potentially dangerous materials.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Stowage and segregation for potentially dangerous...) DANGEROUS CARGOES CARRIAGE OF BULK SOLID MATERIALS THAT REQUIRE SPECIAL HANDLING Stowage and Segregation § 148.155 Stowage and segregation for potentially dangerous materials. (a) A PDM must be stowed and...

50 Years after "Brown": Segregation in the Miami-Dade County Public Schools

ERIC Educational Resources Information Center

Moore, James

2004-01-01

Fifty years after the "Brown v. Board of Education" decision outlawed de jure segregation in American schools, many school districts remain segregated. Despite numerous efforts aimed at desegregation, residential segregation--the primary barrier to significant school desegregation--remains entrenched throughout the United States. The Miami-Dade…

Development of a test to measure the tendency for a hot-mix asphalt to segregate

DOT National Transportation Integrated Search

2000-02-01

Hot Mix Asphalt tends to segregate during handling and placement. The use of a test to determine the tendency to segregate would assist the user in determining when a mix gradation needs adjustment to avoid construction of a segregated pavement or wh...

76 FR 76180 - Notice of Realty Action: Termination of Segregation, Opening of Public Lands; Montana

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-06

...] Notice of Realty Action: Termination of Segregation, Opening of Public Lands; Montana AGENCY: Bureau of... generally, subject to valid existing rights, the provisions of existing withdrawals, other segregations of..., subject to valid existing rights, the provision of existing withdrawals, other segregations of record, and...

Student Mobility, Segregation, and Achievement Gaps: Evidence from Clark County, Nevada

ERIC Educational Resources Information Center

Welsh, Richard O.

2018-01-01

Student mobility and school segregation are two important issues with significant equity implications for urban school districts that are often addressed separately. This article examines the relationship between student mobility and school segregation. The findings indicate that more segregated schools typically have smaller within-school…

78 FR 4365 - Capital, Margin, and Segregation Requirements for Security-Based Swap Dealers and Major Security...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-22

... 3235-AL12 Capital, Margin, and Segregation Requirements for Security-Based Swap Dealers and Major... public comment to establish capital, margin, and segregation requirements for security-based swap dealers... soliciting comment on proposed rules and rule amendments establishing capital, margin, and segregation...

46 CFR 148.155 - Stowage and segregation for potentially dangerous materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Stowage and segregation for potentially dangerous...) DANGEROUS CARGOES CARRIAGE OF BULK SOLID MATERIALS THAT REQUIRE SPECIAL HANDLING Stowage and Segregation § 148.155 Stowage and segregation for potentially dangerous materials. (a) A PDM must be stowed and...

Indian Residential Segregation in the Urban Southwest: 1970 and 1980.

ERIC Educational Resources Information Center

Bohland, James R.

1982-01-01

Indian segregation in 11 cities in the Southwest in 1970 and 1980 was less than the segregation of either Blacks or Spanish Americans. Indian segregation declined between 1970 and 1980, but the decline was least in cities experiencing the greatest growth in Indian population. (Author/AM)

Mixing, segregation, and flow of granular materials

NASA Astrophysics Data System (ADS)

McCarthy, Joseph J.

1998-11-01

This dissertation addresses mixing, segregation, and flow of granular materials with the ultimate goal of providing fundamental understanding and tools for the rational design and optimization of mixing devices. In particular, the paradigm cases of a slowly rotated tumbler mixer and flow down an inclined plane are examined. Computational work, as well as supporting experiments, are used to probe both two and three dimensional systems. In the avalanching regime, the mixing and flow can be viewed either on a global-scale or a local-scale. On the global-scale, material is transported via avalanches whose gross motion can be well described by geometrical considerations. On the local-scale, the dynamics of the particle motion becomes important; particles follow complicated trajectories that are highly sensitive to differences in size/density/morphology. By decomposing the problem in this way, it is possible to study the implications of the geometry and dynamics separately and to add complexities in a controlled fashion. This methodology allows even seemingly difficult problems (i.e., mixing in non-convex geometries, and mixing of dissimilar particles) to be probed in a simple yet methodical way. In addition this technique provides predictions of optimal mixing conditions in an avalanching tumbler, a criterion for evaluating the effect of mixer shape, and mixing enhancement strategies for both two and three dimensional mixers. In the continuous regime, the flow can be divided into two regions: a rapid flow region of the cascading layer at the free surface, and a fixed bed region undergoing solid body rotation. A continuum-based description, in which averages are taken across the layer, generates quantitative predictions about the flow in the cascading layer and agrees well with experiment. Incorporating mixing through a diffusive flux (as well as constitutive expression for segregation) within the cascading layer allows for the determination of optimal mixing conditions. Segregation requires a detailed understanding of the interplay between the flow and the properties of the particles. A relatively mature simulation technique, particle dynamics (PD), aptly captures these effects and is eminently suited to mixing studies; particle properties can be varied on a particle-by-particle basis and detailed mixed structures are easily captured and visualized. However, PD is computationally intensive and is therefore of questionable general utility. By combining PD and geometrical insight-in essence, by focusing the particle dynamics simulation only where it is needed-a new hybrid method of simulation, which is much faster than a conventional particle dynamics method, can be achieved. This technique can yield more than an order of magnitude increase in computational speed while maintaining the versatility of a particle dynamics simulation. Alternatively, by utilizing PD to explore segregation mechanisms in simple flows-e.g., flow down an inclined plane-heuristic models and constitutive relations for segregation can be tested. Incorporating these segregation flux terms into a continuum description of the flow in a tumbler allows rapid Lagrangian simulation of the competition between mixing and segregation. For the case of density segregation, this produces good agreement between theory and experiment with essentially no adjustable parameters. In addition, an accurate quantitative prediction of the optimal mixing time is obtained.

Effect of La3+ substitution with Gd3+ on the resistive switching properties of La0.7Sr0.3MnO3 thin films

NASA Astrophysics Data System (ADS)

Lee, Hong-Sub; Park, Chang-Sun; Park, Hyung-Ho

2014-05-01

This study demonstrated that the resistive switching voltage of perovskite manganite material could be controlled by A-site cation substitution in "A" MnO3 perovskite manganite structure. A partial substitution of La3+ in La0.7Sr0.3MnO3 with smaller cation Gd3+ induced A-site vacancy of the largest Sr2+ cation with surface segregation of SrOy due to ionic size mismatch, and the induced vacancies reduced migration energy barrier. The operating voltage decreased from 3.5 V to 2.5 V due to a favorable condition for electrochemical migration and redox of oxygen ions. Moreover, surface-segregated SrOy was enhanced with Gd-substitution and the SrOy reduced Schottky-like barrier height and resistive switching ratio from the potential drop and screening effect. The relationship between A-site vacancy generation resulting in surface segregation of SrOy and resistive switching behavior was also investigated by energy resolved x-ray photoelectron spectroscopy, O 1s near edge x-ray absorption spectroscopy, and current voltage measurement.

Effect of Solute Segregation on Fracture Toughness in a Ni-Cr Steel

NASA Astrophysics Data System (ADS)

Kameda, Jun

1981-12-01

A study has been made of the influence of intergranular solute segregation on fracture toughness K1c in a series of Ni-Cr steels individually doped with Sb, Sn, and P. By means of toughness measurements in steels having two different intergranular Sb distributions, of measurements of acoustic emissions and of scanning electron micrographs of a load-interrupted and post-test-fatigued specimen, the values of K1c, computed from the “pop-in” load of the load vs clip gauge displacement curves, are found to represent the formation of many patches of contiguous intergranular microcracks ahead of the precrack. The present experiments demonstrate that in the early stage of solute segregation, K1c decreases more substantially than does the strength of grain boundaries σ* (measured in the notched bar tests), although the embrittlement effects of metalloid elements are the same order for both K1c and σ*. A proposed model for the stress-gradient-control of brittle fracture supports the finding that the measurements of K1c give a distorted view of the progress of intergranular embrittlement.

An Analysis of the Mode of Gene Action Affecting Pupa Weight in TRIBOLIUM CASTANEUM

PubMed Central

Goodwill, R.

1975-01-01

Triple-testcross experiments (Kearsey and Jinks 1968) were employed to investigate the mode of gene action affecting pupa weight in Tribolium castaneum. Their experimental design involves two inbred lines, the F1 progeny and a segregating population derived from the cross of the inbred lines. In the present experiments, four segregating populations were used. These populations included the F2 generation, a select line (SEL) and two relaxed select lines (RSI and RSII). In addition, all possible reciprocal crosses were made among the RSI, RSII, and SEL populations. It was observed that: (1) additive, dominant and epistatic gene effects all made significant contributions to the pupa weight of the progeny from all four segregating populations; (2) there was no evidence of either accumulation of epistasis as a result of selection in the SEL population or decline in epistasis as a result of removing selection pressure from the RSI and RSII populations; and (3) significant negative heterosis and maternal effects contributed to the pupa weight of the crossbred progeny of the RSI, RSII and SEL populations. PMID:1132679