Kinetics of solid-solid phase transformations in shock waves

This research is focused on the development of a microstructural model for phase transformation kinetics in shock waves. It is assumed that the Hugoniot state lies in the region of metastability around an equilibrium solid‑solid phase boundary, hence this model applies to transformations occurring through nucleation and growth. The model accounts for both homogeneous (thermally driven) and heterogeneous (catalyzed by crystal defects) nucleation in the shock front, the subsequent growth of the nuclei, and their eventual coalescence. The spatiotemporal dependence of the volume fraction is calculated using KJMA kinetic theory. An explicit expression for the interphase interface speed, which appears in the Avrami equation, is provided by a phase field model [1]; the thermodynamic driving force for interface propagation includes the free energy difference of the phases, the transformation work, and an athermal threshold associated with crystal defects [2]. The transformation work accounts for shear stresses due to the shock wave as well as residuals associated with the two-phase microstructure. The plastic constitutive relation of the two-phase material, which is computed using the KJMA-based volume fraction and now standard results from the literature (Crisfield, Eshelby, and Hill), and the heat transport equation are coupled to the thermoelastic equations. The solution of this coupled set of equations yields a nonsteady, two-wave shock profile. We relate the evolution of this shock profile to the nucleation rate and interface speed. Several examples of shock-induced microstructure evolution are presented. REFERENCES [1] Levitas, V.I., Preston, D.L. Phys. Rev. B. 2002, 66, 134206, 134207. [2] Levitas, V.I., Lee, D.-W., Preston, D.L. 2010. Int. J. Plasticity. 2010, 26, 395

The curvature of semidirect product groups associated with two-component Hunter-Saxton systems

In this paper, we study two-component versions of the periodic Hunter-Saxton equation and its $\mu$-variant. Considering both equations as a geodesic flow on the semidirect product of the circle diffeomorphism group \Diff(\S) with a space of scalar functions on $\S$ we show that both equations are locally well-posed. The main result of the paper is that the sectional curvature associated with the 2HS is constant and positive and that 2$\mu$HS allows for a large subspace of positive sectional curvature. The issues of this paper are related to some of the results for 2CH and 2DP presented in [J. Escher, M. Kohlmann, and J. Lenells, J. Geom. Phys. 61 (2011), 436-452].Comment: 19 page

Missing observations in ARIMA models: skipping strategy versus additive outlier approach

Optimal estimation of missing values in ARMA models is typically performed by using the Kalman Filter for likelihood evaluation, "skipping" in the computations the missing observations, obtaining the maximum likelihood (ML) estimators of the model parameters, and using some smoothing algorithm. The same type of procedure has been extended to nonstationary ARIMA models in G6mez Maravall (1994). An alternative procedure suggests filling in the holes in the series with arbitrary values and then performing ML estimation of the ARIMA model with Additive Outliers (AO). When the model parameters are not known the two methods differ, since the AO likelihood is affected by the arbitrary values. We develop the proper likelihood for the AO approach in the general non-stationary case and show the equivalence of this and the skipping method. Computationally efficient ways to apply both procedures, based on an Augmented Kalman Filter, are detailed. Finally, the two methods are compared through simulation, and their relative advantages assessed; the comparison also includes the AO method with the uncorrected likelihood

School Inequality: Challenges and Solutions

“Welcome Remarks” were given by Wendy Collins Perdue, Dean of the University of Richmond School of Law, and Dr. Ronald Crutcher, President of the University of Richmond. (9:05 a.m.–9:15 a.m.) “Keynote” by Catherine Lhamon, U.S. Department of Education Assistant Secretary for Civil Rights. (9:15 a.m.–10:00 a.m.) “State-Level School Finance Panel” by Kimberly Robinson, Professor of Law at the University of Richmond School of Law; David Hinojosa, National Director of Policy with the Intercultural Development Research Association (IDRA); and Molly Hunter, Director of the Education Law Center’s Educational Justice program. (10:00 a.m.–11:10 a.m.) “Innovation in Addressing School Inequality Panel” by Lisa Scruggs, Partner with Duane Morris, LLP; Javaid Siddiqi, Director of Hunt-Kean Leadership Fellows at the Hunt Institute; and Jerusha Conner, Associate Professor and Graduate Education Program Coordinator at Villanova University, College of Liberal Arts and Sciences. (11:10 a.m.–12:20 p.m.) “School Discipline Panel” by Jason Nance, Associate Professor of Law and the Associate Director for Education Law and Policy at the Center on Children and Families at the University of Florida Levin College of Law; Marilyn Armour, a University Distinguished Teaching Professor and Director of the Institute for Restorative Justice and Restorative Dialogue at the University of Texas at Austin School of Social Work; Pamela Meanes, Partner at Thompson Coburn LLP and former President of the National Bar Association; and Meredith Harbach, Professor of Law at the University of Richmond School of Law. (1:20 p.m.–2:30 p.m.) Finally, a debate on the role the federal government should hold in the governance of public education featured Preston Green III, the John and Carla Klein Professor of Urban Education and Professor of Educational Leadership and Law at the University of Connecticut (arguing in favor of the federal government having an increased role) and Gerard Robinson, Resident Fellow of Educational Policy Studies at the American Enterprise Institute (arguing against). (2:30 p.m.–3:30 p.m.

Micro-Electro-Mechanical-Systems (MEMS) and Fluid Flows

The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electro-mechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research

Depth-resolved measurement of mucosal microvascular blood content using low-coherence enhanced backscattering spectroscopy

Low-coherence enhanced backscattering (LEBS) spectroscopy is a light scattering technique which uses partial spatial coherence broadband illumination to interrogate the optical properties at sub-diffusion length scales. In this work, we present a post-processing technique which isolates the hemoglobin concentration at different depths within a sample using a single spectroscopic LEBS measurement with a fixed spatial coherence of illumination. We verify the method with scattering (spectralon reflectance standard and polystyrene microspheres) and absorbing (hemoglobin) phantoms. We then demonstrate the relevance of this method for quantifying hemoglobin content as a function of depth within biological tissue using the azoxymethane treated animal model of colorectal cancer

Copy Number Variation of <i>CCL3-</i>like Genes Affects Rate of Progression to Simian-AIDS in Rhesus Macaques (<i>Macaca mulatta</i>)

Variation in genes underlying host immunity can lead to marked differences in susceptibility to HIV infection among humans. Despite heavy reliance on non-human primates as models for HIV/AIDS, little is known about which host factors are shared and which are unique to a given primate lineage. Here, we investigate whether copy number variation (CNV) at CCL3-like genes (CCL3L), a key genetic host factor for HIV/AIDS susceptibility and cell-mediated immune response in humans, is also a determinant of time until onset of simian-AIDS in rhesus macaques. Using a retrospective study of 57 rhesus macaques experimentally infected with SIVmac, we find that CCL3L CNV explains approximately 18% of the variance in time to simian-AIDS (pCCL3L copy number associating with more rapid disease course. We also find that CCL3L copy number varies significantly (p−6) among rhesus subpopulations, with Indian-origin macaques having, on average, half as many CCL3L gene copies as Chinese-origin macaques. Lastly, we confirm that CCL3L shows variable copy number in humans and chimpanzees and report on CCL3L CNV within and among three additional primate species. On the basis of our findings we suggest that (1) the difference in population level copy number may explain previously reported observations of longer post-infection survivorship of Chinese-origin rhesus macaques, (2) stratification by CCL3L copy number in rhesus SIV vaccine trials will increase power and reduce noise due to non-vaccine-related differences in survival, and (3) CCL3L CNV is an ancestral component of the primate immune response and, therefore, copy number variation has not been driven by HIV or SIV per se.</p

Upregulation of basolateral small conductance potassium channels (KCNQ1/KCNE3) in ulcerative colitis

Background Basolateral K+ channels hyperpolarize colonocytes to ensure Na+ (and thus water) absorption. Small conductance basolateral (KCNQ1/KCNE3) K+ channels have never been evaluated in human colon. We therefore evaluated KCNQ1/KCNE3 channels in distal colonic crypts obtained from normal and active ulcerative colitis (UC) patients. Methods KCNQ1 and KCNE3 mRNA levels were determined by qPCR, and KCNQ1/KCNE3 channel activity in normal and UC crypts, and the effects of forskolin (activator of adenylate cyclase) and UC-related proinflammatory cytokines on normal crypts, studied by patch clamp recording. Results Whereas KCNQ1 and KCNE3 mRNA expression was similar in normal and UC crypts, single 6.8 pS channels were seen in 36% of basolateral patches in normal crypts, and to an even greater extent (74% of patches, P < 0.001) in UC crypts, with two or more channels per patch. Channel activity was 10-fold higher (P < 0.001) in UC crypts, with a greater contribution to basolateral conductance (5.85 ± 0.62 mS cm−2) than in controls (0.28 ± 0.04 mS cm−2, P < 0.001). In control crypts, forskolin and thromboxane A2 stimulated channel activity 30-fold and 10-fold respectively, while PGE2, IL-1β, and LTD4 had no effect. Conclusions KCNQ1/KCNE3 channels make only a small contribution to basolateral conductance in normal colonic crypts, with increased channel activity in UC appearing insufficient to prevent colonic cell depolarization in this disease. This supports the proposal that defective Na+ absorption rather than enhanced Cl− secretion, is the dominant pathophysiological mechanism of diarrhea in UC

Recombinant Simian Varicella Virus-Simian Immunodeficiency Virus Vaccine Induces T and B Cell Functions and Provides Partial Protection against Repeated Mucosal SIV Challenges in Rhesus Macaques

HIV vaccine mediated efficacy, using an expanded live attenuated recombinant varicella virus-vectored SIV rSVV-SIVgag/env vaccine prime with adjuvanted SIV-Env and SIV-Gag protein boosts, was evaluated in a female rhesus macaques (RM) model against repeated intravaginal SIV challenges. Vaccination induced anti-SIV IgG responses and neutralizing antibodies were found in all vaccinated RMs. Three of the eight vaccinated RM remained uninfected (vaccinated and protected, VP) after 13 repeated challenges with the pathogenic SIVmac251-CX-1. The remaining five vaccinated and infected (VI) macaques had significantly reduced plasma viral loads compared with the infected controls (IC). A significant increase in systemic central memory CD4+ T cells and mucosal CD8+ effector memory T-cell responses was detected in vaccinated RMs compared to controls. Variability in lymph node SIV-Gag and Env specific CD4+ and CD8+ T cell cytokine responses were detected in the VI RMs while all three VP RMs had more durable cytokine responses following vaccination and prior to challenge. VI RMs demonstrated predominately SIV-specific monofunctional cytokine responses while the VP RMs generated polyfunctional cytokine responses. This study demonstrates that varicella virus-vectored SIV vaccination with protein boosts induces a 37.5% efficacy rate against pathogenic SIV challenge by generating mucosal memory, virus specific neutralizing antibodies, binding antibodies, and polyfunctional T-cell responses

No evidence of tradeoffs in the evolution of sperm numbers and sperm size in mammals

Postcopulatory sexual selection, in the form sperm competition, has influenced the evolution of several male reproductive traits. However, theory predicts that sperm competition would lead to tradeoffs between numbers and size of spermatozoa because increased costs per cell would result in a reduction of sperm number if both traits share the same energetic budget. Theoretical models have proposed that, in large animals, increased sperm size would have minimal fitness advantage compared with increased sperm numbers. Thus, sperm numbers would evolve more rapidly than sperm size under sperm competition pressure. We tested in mammals whether sperm competition maximizes sperm numbers and size, and whether there is a tradeoff between these traits. Our results showed that sperm competition maximizes sperm numbers in eutherian and metatherian mammals. There was no evidence of a tradeoff between sperm numbers and sperm size in any of the two mammalian clades since we did not observe any significant relationship between sperm numbers and sperm size once the effect of sperm competition was taken into account. Maximization of both numbers and size in mammals may occur because each trait is crucial at different stages in sperm's life; e.g., size determined sperm velocity is a key determinant of fertilization success. In addition, numbers and size may also be influenced by diverse energetic budgets required at different stages of sperm formation