Integrated controls and health monitoring for chemical transfer propulsion

NASA is reviewing various propulsion technologies for exploring space. The requirements are examined for one enabling propulsion technology: Integrated Controls and Health Monitoring (ICHM) for Chemical Transfer Propulsion (CTP). Functional requirements for a CTP-ICHM system are proposed from tentative mission scenarios, vehicle configurations, CTP specifications, and technical feasibility. These CTP-ICHM requirements go beyond traditional reliable operation and emergency shutoff control to include: (1) enhanced mission flexibility; (2) continuously variable throttling; (3) tank-head start control; (4) automated prestart and post-shutoff engine check; (5) monitoring of space exposure degradation; and (6) product evolution flexibility. Technology development plans are also discussed

A candidate architecture for monitoring and control in chemical transfer propulsion systems

To support the exploration of space, a reusable space-based rocket engine must be developed. This engine must sustain superior operability and man-rated levels of reliability over several missions with limited maintenance or inspection between flights. To meet these requirements, an expander cycle engine incorporating a highly capable control and health monitoring system is planned. Alternatives for the functional organization and the implementation architecture of the engine's monitoring and control system are discussed. On the basis of this discussion, a decentralized architecture is favored. The trade-offs between several implementation options are outlined and future work is proposed

Theoretical investigation of finite size effects at DNA melting

We investigated how the finiteness of the length of the sequence affects the phase transition that takes place at DNA melting temperature. For this purpose, we modified the Transfer Integral method to adapt it to the calculation of both extensive (partition function, entropy, specific heat, etc) and non-extensive (order parameter and correlation length) thermodynamic quantities of finite sequences with open boundary conditions, and applied the modified procedure to two different dynamical models. We showed that rounding of the transition clearly takes place when the length of the sequence is decreased. We also performed a finite-size scaling analysis of the two models and showed that the singular part of the free energy can indeed be expressed in terms of an homogeneous function. However, both the correlation length and the average separation between paired bases diverge at the melting transition, so that it is no longer clear to which of these two quantities the length of the system should be compared. Moreover, Josephson's identity is satisfied for none of the investigated models, so that the derivation of the characteristic exponents which appear, for example, in the expression of the specific heat, requires some care

In vivo microdialysis reveals age-dependent decrease of brain interstitial fluid tau levels in P301S human tau transgenic mice

Although tau is a cytoplasmic protein, it is also found in brain extracellular fluids, e.g., CSF. Recent findings suggest that aggregated tau can be transferred between cells and extracellular tau aggregates might mediate spread of tau pathology. Despite these data, details of whether tau is normally released into the brain interstitial fluid (ISF), its concentration in ISF in relation to CSF, and whether ISF tau is influenced by its aggregation are unknown. To address these issues, we developed a microdialysis technique to analyze monomeric ISF tau levels within the hippocampus of awake, freely moving mice. We detected tau in ISF of wild-type mice, suggesting that tau is released in the absence of neurodegeneration. ISF tau was significantly higher than CSF tau and their concentrations were not significantly correlated. Using P301S human tau transgenic mice (P301S tg mice), we found that ISF tau is fivefold higher than endogenous murine tau, consistent with its elevated levels of expression. However, following the onset of tau aggregation, monomeric ISF tau decreased markedly. Biochemical analysis demonstrated that soluble tau in brain homogenates decreased along with the deposition of insoluble tau. Tau fibrils injected into the hippocampus decreased ISF tau, suggesting that extracellular tau is in equilibrium with extracellular or intracellular tau aggregates. This technique should facilitate further studies of tau secretion, spread of tau pathology, the effects of different disease states on ISF tau, and the efficacy of experimental treatments

Morphology‐Dependent Influences on the Performance of Battery Cells with a Hierarchically Structured Positive Electrode**

The rising demand for high-performing batteries requires new technological concepts. To facilitate fast charge and discharge, hierarchically structured electrodes offer short diffusion paths in the active material. However, there are still gaps in understanding the influences on the cell performance of such electrodes. Here, we employed a cell model to demonstrate that the morphology of the hierarchically structured electrode determines which electrochemical processes dictate the cell performance. The potentially limiting processes include electronic conductivity within the porous secondary particles, solid diffusion within the primary particles, and ionic transport in the electrolyte surrounding the secondary particles. Mitigating these limits requires an electronic conductivity in the active material of at least 10−4 S m−1 and a primary particle radius below 100 nm. Our insights enable a goal-oriented tailoring of hierarchically structured electrodes for high-power applications

Morphology-Dependent Influences on the Performance of Battery Cells with a Hierarchically Structured Positive Electrode

The rising demand for high-performing batteries requires new technological concepts. To facilitate fast charge and discharge, hierarchically structured electrodes offer short diffusion paths in the active material. However, there are still gaps in understanding the influences on the cell performance of such electrodes. Here, we employed a cell model to demonstrate that the morphology of the hierarchically structured electrode determines which electrochemical processes dictate the cell performance. The potentially limiting processes include electronic conductivity within the porous secondary particles, solid diffusion within the primary particles, and ionic transport in the electrolyte surrounding the secondary particles. Our insights enable a goal-oriented tailoring of hierarchically structured electrodes for high-power applications

Type I and type II interferon responses in two human liver cell lines (Huh-7 and HuH6)

AbstractMost studies investigating the biology of Hepatitis C virus (HCV) have used the human hepatoma cell line Huh-7 or subclones thereof, as these are the most permissive cell lines for HCV infection and replication. Other cell lines also support replication of HCV, most notably the human hepatoblastoma cell line HuH6. HCV replication in cell culture is generally highly sensitive to interferons (IFNs) and differences in the IFN-mediated inhibition of virus replication may reflect alterations in the IFN-induced antiviral response inherent to different host cells. For example, HCV replication is highly sensitive to IFN-γ treatment in Huh-7, but not in HuH6 cells. In this study, we used microarray-based gene expression profiling to compare the response of Huh-7 and HuH6 cells to stimulation with IFN-α and IFN-γ. Furthermore, we determined whether the resistance of HCV replication in HuH6 cells can be linked to differences in the expression profile of IFN-regulated genes. Although both cells lines responded to IFNs with rapid changes in gene expression, thereby demonstrating functional type I and type II signaling pathways, differences were observed for a number of genes. Raw and normalized expression data have been deposited in GEO under accession number GSE68927

On Mean Field Glassy Dynamics out of Equilibrium

We study the off equilibrium dynamics of a mean field disordered systems which can be interpreted both as a long range interaction spin glass and as a particle in a random potential. The statics of this problem is well known and exhibits a low temperature spin glass phase with continuous replica symmetry breaking. We study the equations of off equilibrium dynamics with analytical and numerical methods. In the spin glass phase, we find that the usual equilibrium dynamics (observed when the observation time is much smaller than the waiting time) coexists with an aging regime. In this aging regime, we propose a solution implying a hierarchy of crossovers between the observation time and the waiting time.Comment: LaTeX, LPTENS preprint 94/0

Graft-versus-Host disease Prophylaxis with Everolimus and Tacrolimus Is Associated with a High Incidence of Sinusoidal Obstruction Syndrome and Microangiopathy: Results of the EVTAC Trial

AbstractA calcineurin inhibitor combined with methotrexate is the standard prophylaxis for graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). Everolimus, a derivative of sirolimus, seems to mediate antileukemia effects. We report on a combination of everolimus and tacrolimus in 24 patients (median age, 62 years) with either myelodysplastic syndrome (MDS; n = 17) or acute myeloid leukemia (AML; n = 7) undergoing intensive conditioning followed by HSCT from related (n = 4) or unrelated (n = 20) donors. All patients engrafted, and only 1 patient experienced grade IV mucositis. Nine patients (37%) developed acute grade II-IV GVHD, and 11 of 17 evaluable patients (64%) developed chronic extensive GVHD. Transplantation-associated microangiopathy (TMA) occurred in 7 patients (29%), with 2 cases of acute renal failure. The study was terminated prematurely because an additional 6 patients (25%) developed sinusoidal obstruction syndrome (SOS), which was fatal in 2 cases. With a median follow-up of 26 months, the 2-year overall survival rate was 47%. Although this new combination appears to be effective as a prophylactic regimen for acute GVHD, the incidence of TMA and SOS is considerably higher than seen with other regimens