Processing of glass-ceramics from lunar resources

The goal is to fabricate useful ceramic materials from the by-products of lunar oxygen production processes. Specifically, the crystal nucleation and growth kinetics of ilmenite-extracted lunar regolith were studied in order to produce glass-ceramics with optimal mechanical, thermal, and abrasion resistant properties. In the initial year of the program, construction and calibration of a high temperature viscometer, used for determining the viscosity of simulated lunar glasses was finished. A series of lunar simulants were also prepared, and the viscosity of each was determined over a range of temperatures. It was found that an increase in the concentration of Fe2O3 decreases the viscosity of the glass. While this may be helpful in processing the glass, Fe2O3 concentrations greater than approximately 10 wt percent resulted in uncontrolled crystallization during viscosity measurements. Impurities (such as Na2O, MnO, and K2O) in the regolith appeared to decrease the viscosity of the parent glass. These effects, as well as those of TiO2 and SiO2 on the processability of the glass, however, remain to be quantified

Boundary Layers on Sobolev–Besov Spaces and Poisson's Equation for the Laplacian in Lipschitz Domains

AbstractWe study inhomogeneous boundary value problems for the Laplacian in arbitrary Lipschitz domains with data in Sobolev–Besov spaces. As such, this is a natural continuation of work in [Jerison and Kenig,J. Funct. Anal.(1995), 16–219] where the inhomogeneous Dirichlet problem is treated via harmonic measure techniques. The novelty of our approach resides in the systematic use of boundary integral methods. In this regard, the key results are establishing the invertibility of the classical layer potential operators on scales of Sobolev–Besov spaces on Lipschitz boundaries for optimal ranges of indices. Applications toLp-based Helmholtz type decompositions of vector fields in Lipschitz domains are also presented

Prospective Cohort Study Assessing the Use of Peripheral Saphenous Venous Pressure Monitoring as a Marker of the Transcaval Venous Pressure Gradient in Liver Transplant Surgery

Objectives: Assessment of the transcaval venous pressure gradient, the central venous to inferior vena caval pressure, assists anesthetists and surgeons in management of liver transplant recipients. Traditionally, this entails insertion of a femoral central line with increased patient risk and health care cost. Here, we assessed the ability of a saphenous vein cannula to act as a surrogate for the femoral central line as a means to assess the transcaval pressure gradient in a safer and less invasive manner. / Materials and Methods: A prospective cohort of 22 patients undergoing liver transplant underwent saphenous vein cannulation in addition to insertion of a femoral and internal jugular central venous catheter. Data were collected throughout each phase of surgery to assess the central, femoral, and saphenous vein pressures; results of a range of relevant physiological and ventilatory data were also collected. / Results: The primary outcome, the correlation between saphenous and femoral venous pressure throughout surgery, was acceptable (r2 = 0.491, P < .001). During the anhepatic phase of surgery, this correlation improved (r2 = 0.912, P < .001). The correlation between the femoral to central venous pressure and saphenous to central venous pressure gradients was also reasonable throughout surgery (r2 = 0.386, P < .001), and this correlation was significantly stronger during the anhepatic phase (r2 = 0.935, P < .001). / Conclusions: Saphenous venous pressure, provided by peripheral cannulation, provided a reliable, less invasive, and safer alternative to femoral central line insertion for determination of the transcaval pressure gradient during the anhepatic phase of liver transplant

Sharp two-sided heat kernel estimates for critical Schr\"odinger operators on bounded domains

On a smooth bounded domain \Omega \subset R^N we consider the Schr\"odinger operators -\Delta -V, with V being either the critical borderline potential V(x)=(N-2)^2/4 |x|^{-2} or V(x)=(1/4) dist (x,\partial\Omega)^{-2}, under Dirichlet boundary conditions. In this work we obtain sharp two-sided estimates on the corresponding heat kernels. To this end we transform the Scr\"odinger operators into suitable degenerate operators, for which we prove a new parabolic Harnack inequality up to the boundary. To derive the Harnack inequality we have established a serier of new inequalities such as improved Hardy, logarithmic Hardy Sobolev, Hardy-Moser and weighted Poincar\'e. As a byproduct of our technique we are able to answer positively to a conjecture of E.B.Davies.Comment: 40 page

The Next 50 Years: Considering Gender as a Context for Understanding Young Children’s Peer Relationships

The study of children’s peer relationships has been well represented within the pages of Merrill-Palmer Quarterly. Particularly over the last decade, the pace of publishing studies on peer relationships has increased. Despite this upswing in interest in peer relationships, significant gaps remain. In this article, we focus on a particularly overlooked and significant area of peer relationships, namely, the role of sex-segregated peer interactions and how these relate to development in early childhood. We review why this topic is important for researchers to consider and highlight promising directions for research that we hope will appear in future volumes of Merrill-Palmer Quarterly

Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows

We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN], on the vanishing viscosity limit of circularly symmetric viscous flow in a disk with rotating boundary, shown there to converge to the inviscid limit in $L^2$-norm as long as the prescribed angular velocity $\alpha(t)$ of the boundary has bounded total variation. Here we establish convergence in stronger $L^2$ and $L^p$-Sobolev spaces, allow for more singular angular velocities $\alpha$, and address the issue of analyzing the behavior of the boundary layer. This includes an analysis of concentration of vorticity in the vanishing viscosity limit. We also consider such flows on an annulus, whose two boundary components rotate independently. [LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J., Vanishing viscosity limit for incompressible flow inside a rotating circle, preprint 2006

Investigating the role of ephrin signalling in spinal cord injury.

Spinal cord injury in adult mammals commonly leads to the permanent loss of motor and sensory function in regions of the body below the level of injury. The inability of the central nervous system to regenerate is, in part, due to the presence of growth-inhibitory agents surrounding the lesion site. This thesis presents a previously unreported, inhibitory interaction between ephrinB2 expressed on reactive astrocytes and the EphA4 receptor present on lesioned corticospinal tract axons. This interaction appears to mediate the unusually large retraction of the corticospinal tract away from spinal cord injury sites. An attempt to interfere with this interaction by implanting a cell line secreting the ephrinA5 receptor binding domain is reported. While this approach induced improvements in regenerative sprouting from the corticospinal tract, complications with immune rejection and cell proliferation stopped further investigation. A second intervention using a small peptide with high affinity and specificity for the EphA4 receptor is also reported. Intrathecal infusion of this peptide for 14 or 28 days after injury reversed the retraction of the corticospinal tract and induced improvements in regenerative sprouting from corticospinal and rubrospinal tracts following dorsal or lateral white matter transection injuries. Sprouts were seen to migrate long distances, often to the astrocyte margin of the lesion cavity. Astrocyte behaviour following injury was also altered with the formation of astrocytic 'bridges' into the lesion cavity along which regenerating axons grew. Functional recovery was also enhanced with improvements in the paw reaching assay within 10 days of a unilateral dorsal column lesion with a 30% recovery of function at 28 days post-operation. The simplicity of this intervention and direct translation to human application make it a promising candidate for use in combinatorial approaches to human spinal cord injury treatment

Crack Bridging Mechanism for Glass Strengthening by Organosilane Water-Based Coatings

We used an epoxysilane/aminosilane coating deposited from an aqueous solution to strengthen flat glass. We studied film formation, interfacial and mechanical properties of the film. The film is highly cross-linked with a 6 GPa Young's modulus and good adhesion. Our results suggest that crack face bridging accounts for most of the 75 % reinforcement in this system