Development of low density rigid polyurethane foam for use of s-1c flight vehicles final report

Compression testing of low density rigid polyurethane foam for S-1DC flight vehicle

Normalization of Gravitational Acceleration Models

Unlike the uniform density spherical shell approximations of Newton, the con- sequence of spaceflight in the real universe is that gravitational fields are sensitive to the nonsphericity of their generating central bodies. The gravitational potential of a nonspherical central body is typically resolved using spherical harmonic approximations. However, attempting to directly calculate the spherical harmonic approximations results in at least two singularities which must be removed in order to generalize the method and solve for any possible orbit, including polar orbits. Three unique algorithms have been developed to eliminate these singularities by Samuel Pines [1], Bill Lear [2], and Robert Gottlieb [3]. This paper documents the methodical normalization of two1 of the three known formulations for singularity-free gravitational acceleration (namely, the Lear [2] and Gottlieb [3] algorithms) and formulates a general method for defining normalization parameters used to generate normalized Legendre Polynomials and ALFs for any algorithm. A treatment of the conventional formulation of the gravitational potential and acceleration is also provided, in addition to a brief overview of the philosophical differences between the three known singularity-free algorithms

Disrupted CXCR2 Signaling in Oligodendroglia Lineage Cells Enhances Myelin Repair in a Viral Model of Multiple Sclerosis.

CXCR2 is a chemokine receptor expressed on oligodendroglia that has been implicated in the pathogenesis of neuroinflammatory demyelinating diseases as well as enhancement of the migration, proliferation, and myelin production by oligodendroglia. Using an inducible proteolipid protein (Plp) promoter-driven Cre-loxP recombination system, we were able to assess how timed ablation of Cxcr2 in oligodendroglia affected disease following intracranial infection with the neurotropic JHM strain of mouse hepatitis virus (JHMV). Generation of Plp-Cre-ER(T)::Cxcr2flox/flox transgenic mice (termed Cxcr2-CKO mice) allows for Cxcr2 to be silenced in oligodendrocytes in adult mice following treatment with tamoxifen. Ablation of oligodendroglia Cxcr2 did not influence clinical severity in response to intracranial infection with JHMV. Infiltration of activated T cells or myeloid cells into the central nervous system (CNS) was not affected, nor was the ability to control viral infection. In addition, the severity of demyelination was similar between tamoxifen-treated mice and vehicle-treated controls. Notably, deletion of Cxcr2 resulted in increased remyelination, as assessed by g-ratio (the ratio of the inner axonal diameter to the total outer fiber diameter) calculation, compared to that in vehicle-treated control mice. Collectively, our findings argue that CXCR2 signaling in oligodendroglia is dispensable with regard to contributing to neuroinflammation, but its deletion enhances remyelination in a preclinical model of the human demyelinating disease multiple sclerosis (MS).IMPORTANCE Signaling through the chemokine receptor CXCR2 in oligodendroglia is important for developmental myelination in rodents, while chemical inhibition or nonspecific genetic deletion of CXCR2 appears to augment myelin repair in animal models of the human demyelinating disease multiple sclerosis (MS). To better understand the biology of CXCR2 signaling on oligodendroglia, we generated transgenic mice in which Cxcr2 is selectively ablated in oligodendroglia upon treatment with tamoxifen. Using a viral model of neuroinflammation and demyelination, we demonstrate that genetic silencing of CXCR2 on oligodendroglia did not affect clinical disease, neuroinflammation, or demyelination, yet there was increased remyelination. These findings support and extend previous findings suggesting that targeting CXCR2 may offer a therapeutic avenue for enhancing remyelination in patients with demyelinating diseases

Model documentation, chapter 4

The modeling groups are listed along with a brief description of the respective models

Postcardiac transplant survival in the current era in patients receiving continuous-flow left ventricular assist devices

ObjectivesContinuous-flow left ventricular assist devices have become the standard of care for patients with heart failure requiring mechanical circulatory support as a bridge to transplant. However, data on long-term post-transplant survival for these patients are limited. We evaluated the effect of continuous-flow left ventricular assist devices on postcardiac transplant survival in the current era.MethodsAll patients who received a continuous-flow left ventricular assist device as a bridge to transplant at a single center from June 2005 to September 2011 were evaluated.ResultsOf the 167 patients who received a continuous-flow left ventricular assist device as a bridge to transplant, 77 (46%) underwent cardiac transplantation, 27 died before transplantation (16%), and 63 (38%) remain listed for transplantation and continued with left ventricular assist device support. The mean age of the transplanted patients was 54.5 ± 11.9 years, 57% had an ischemic etiology, and 20% were women. The overall mean duration of left ventricular assist device support before transplantation was 310 ± 227 days (range, 67-1230 days). The mean duration of left ventricular assist device support did not change in patients who had received a left ventricular assist device in the early period of the study (2005-2008, n = 62) compared with those who had received a left ventricular assist device later (2009-2011, n = 78, 373 vs 392 days, P = NS). In addition, no difference was seen in survival between those patients supported with a left ventricular assist device for fewer than 180 days or longer than 180 days before transplantation (P = NS). The actuarial survival after transplantation at 30 days and 1, 3, and 5 years by Kaplan-Meier analysis was 98.7%, 93.0%, 91.1%, and 88.0%, respectively.ConclusionsThe short- and long-term post-transplant survival for patients bridged with a continuous-flow left ventricular assist device in the current era has been excellent. Furthermore, the duration of left ventricular assist device support did not affect post-transplant survival. The hemodynamic benefits of ventricular unloading with continuous-flow left ventricular assist devices, in addition to their durability and reduced patient morbidity, have contributed to improved post-transplant survival

Theory and observations: Model simulations of the period 1955-1985

The main objective of the theoretical studies presented here is to apply models of stratospheric chemistry and transport in order to understand the processes that control stratospheric ozone and that are responsible for the observed variations. The model calculations are intended to simulate the observed behavior of atmospheric ozone over the past three decades (1955-1985), for which there exists a substantial record of both ground-based and, more recently, satellite measurements. Ozone concentrations in the atmosphere vary on different time scales and for several different causes. The models described here were designed to simulate the effect on ozone of changes in the concentration of such trace gases as CFC, CH4, N2O, and CO2. Changes from year to year in ultraviolet radiation associated with the solar cycle are also included in the models. A third source of variability explicitly considered is the sporadic introduction of large amounts of NO sub x into the stratosphere during atmospheric nuclear tests

Model/data comparisons of ozone in the upper stratosphere and mesosphere

We compare ground-based microwave observations of ozone in the upper stratosphere and mesosphere with daytime observations made from the SME (Solar Mesosphere Explorer) satellite, with nighttime data from the LIMS instrument, and with a diurnal photochemical model. The results suggest that the data are all in reasonable agreement and that the model-data discrepancy is much less than previously thought, particularly in the mesosphere. This appears to be due to the fact that the latest data are lower than earlier reports and the updated model predicts more ozone than older versions. The model and the data agree to within a factor of 1.5 at all altitudes and typically are within 20 percent

Resonant enhancement of the jump rate in a double-well potential

We study the overdamped dynamics of a Brownian particle in the double-well potential under the influence of an external periodic (AC) force with zero mean. We obtain a dependence of the jump rate on the frequency of the external force. The dependence shows a maximum at a certain driving frequency. We explain the phenomenon as a switching between different time scales of the system: interwell relaxation time (the mean residence time) and the intrawell relaxation time. Dependence of the resonant peak on the system parameters, namely the amplitude of the driving force A and the noise strength (temperature) D has been explored. We observe that the effect is well pronounced when A/D > 1 and if A/D 1 the enhancement of the jump rate can be of the order of magnitude with respect to the Kramers rate.Comment: Published in J. Phys. A: Math. Gen. 37 (2004) 6043-6051; 6 figure