Catalysts for ultrahigh current density oxygen cathodes for space fuel cell applications

The objective of this research was to identify promising electrocatalyst/support systems for the oxygen cathode in alkaline fuel cells operating at relatively high temperatures, O2 pressures and current densities. A number of materials were prepared, including Pb-Ru and Pb-Ir pyrochlores, RuO2 and Pt-doped RuO2, and lithiated NiO. Several of these were prepared using techniques that had not been previously used to prepare them. Particularly interesting is the use of the alkaline solution technique to prepare the Pt-doped Pb-Ru pyrochlore in high area form. Well-crystallized Pb(2)Ru(2)O(7-y) was used to fabricate high performance O2 cathodes with relatively good stability in room temperature KOH. This material was also found to be stable over a useful potential range at approximately 140 C in concentrated KOH. Other pyrochlores were found to be either unstable (amorphous samples) or the fabrication of the gas-fed electrodes could not be fully optimized during this project period. Future work may be directed at this problem. High area platinum supported on conductive metal oxide supports produced mixed results: small improvements in O2 reduction performance for Pb(2)Ru(2)O(7-y) but a large improvement for Li-doped NiO at room temperature. Nearly reversible behavior was observed for the O2/OH couple for Li-doped NiO at approximately 200 C

A Simplified Procedure for Sizing Vertical Ground Coupled Heat Pump Heat Exchangers for Residences in Texas

A simplified technique for the sizing of vertical U-tube ground coupled heat pump (GCHP) heat exchangers for Texas climates was developed utilizing a transient simulation model of a ground coupled heat pump and weather and soil data for Texas. The simulation model discretized the ground heat exchanger into elements and computed the temperature distribution surrounding the heat exchanger on a minute-by-minute basis. Hundreds of runs were made with the model for a wide range of ground temperatures, ground thermal properties (density, thermal conductivity, and specific heat), and outdoor weather. A set of sizing charts were developed from the model runs that could provide quick reference on the size of the ground heat exchanger. Corrections for ground temperature, ground density, ground thermal conductivity, and indoor air temperature were presented. Soil temperature and thermal conductivity were found to be the most important parameters for sizing GCHP heat exchangers. Results from the simplified method were compared to two available heat exchanger sizing methods: the National Water Well Association (NWWA) and the International Ground Source Heat Pump Association (IGSHPA). The simplified method predicted shorter lengths than those from either of these two methods

A Modified Analytical Method for Simulating Cyclic Operation of Vertical U-Tube Ground-Coupled Heat Pumps

A modified analytical model is presented which discretizes the ground-coupled heat exchanger of a ground-coupled heat pump and utilized a separate cylindrical source solution for each element. First law expressions are utilized for each element to derive a set of fully implicit finite difference equations for the pipe wall temperature and the fluid temperature profile inside the ground-coupled heat exchanger. This method entails less computational overhead than methods which utilize numerical solutions inside the soil, and comes closer than previous analytical methods to satisfying the constant heat flux assumption of the original analytical solution. The thermal capacitance effects of the fluid inside the ground-coupled heat exchanger are included to allow proper prediction of the entering water temperature (EWT) profile at start-up. Comparisons with experimental data on EWT, capacity, energy input and cycling are provided

The lysosomal inhibitor, chloroquine, increases cell surface BMPR-II levels and restores BMP9 signalling in endothelial cells harbouring BMPR-II mutations.

Pulmonary arterial hypertension (PAH) is characterized by dysregulated pulmonary artery endothelial cell (PAEC) proliferation, apoptosis and permeability. Loss-of-function mutations in the bone morphogenetic protein receptor type-II (BMPR-II) are the most common cause of heritable PAH, usually resulting in haploinsufficiency. We previously showed that BMPR-II expression is regulated via a lysosomal degradative pathway. Here, we show that the antimalarial drug, chloroquine, markedly increased cell surface expression of BMPR-II protein independent of transcription in PAECs. Inhibition of protein synthesis experiments revealed a rapid turnover of cell surface BMPR-II, which was inhibited by chloroquine treatment. Chloroquine enhanced PAEC expression of BMPR-II following siRNA knockdown of the BMPR-II transcript. Using blood outgrowth endothelial cells (BOECs), we confirmed that signalling in response to the endothelial BMPR-II ligand, BMP9, is compromised in BOECs from patients harbouring BMPR-II mutations, and in BMPR-II mutant PAECs. Chloroquine significantly increased gene expression of BMP9-BMPR-II signalling targets Id1, miR21 and miR27a in both mutant BMPR-II PAECs and BOECs. These findings provide support for the restoration of cell surface BMPR-II with agents such as chloroquine as a potential therapeutic approach for heritable PAH

Field Performance of a Ground-Coupled Heat Pump in Abilene, Texas

A nominal 10.6 kW (3 ton), vertical-configuration ground-coupled heat pump was installed in Abilene, Texas in December 1989 and was monitored until May 1993 using a remote data acquisition system. The unit was installed in the guest officer quarters at Dyes Air Force Base. Monitored data included: temperature and relative humidity of return and supply air, water temperature entering and leaving the condenser, power consumption of the individual system components, cycling rate, on-time, and soil temperatures at various depths and radial locations. Water and air flow rates were measured twice during the monitored period, and have remained constant. The measured quantities allow calculation of instantaneous capacity, power, coefficient of performance (COP), and ground-coil heat rejection. Data for operation in the cooling and heating mode are discussed here. Based on the experimental data, it was discovered that the water temperature entering the condenser (EWT) exhibited a prolonged minimum after start-up due to cooling of the water during the off-cycle when operating in the cooling mode. The decreased levels of EWT early in the cycle increased capacity and decreased power, both acting to increase the COP. Seasonal COPs for heating and cooling were estimated from the data and are presented

Functional analysis of transcription factor binding sites in human promoters

BACKGROUND: The binding of transcription factors to specific locations in the genome is integral to the orchestration of transcriptional regulation in cells. To characterize transcription factor binding site function on a large scale, we predicted and mutagenized 455 binding sites in human promoters. We carried out functional tests on these sites in four different immortalized human cell lines using transient transfections with a luciferase reporter assay, primarily for the transcription factors CTCF, GABP, GATA2, E2F, STAT, and YY1. RESULTS: In each cell line, between 36% and 49% of binding sites made a functional contribution to the promoter activity; the overall rate for observing function in any of the cell lines was 70%. Transcription factor binding resulted in transcriptional repression in more than a third of functional sites. When compared with predicted binding sites whose function was not experimentally verified, the functional binding sites had higher conservation and were located closer to transcriptional start sites (TSSs). Among functional sites, repressive sites tended to be located further from TSSs than were activating sites. Our data provide significant insight into the functional characteristics of YY1 binding sites, most notably the detection of distinct activating and repressing classes of YY1 binding sites. Repressing sites were located closer to, and often overlapped with, translational start sites and presented a distinctive variation on the canonical YY1 binding motif. CONCLUSIONS: The genomic properties that we found to associate with functional TF binding sites on promoters -- conservation, TSS proximity, motifs and their variations -- point the way to improved accuracy in future TFBS predictions

Accurate structure factors from pseudopotential methods

Highly accurate experimental structure factors of silicon are available in the literature, and these provide the ideal test for any \emph{ab initio} method for the construction of the all-electron charge density. In a recent paper [J. R. Trail and D. M. Bird, Phys. Rev. B {\bf 60}, 7863 (1999)] a method has been developed for obtaining an accurate all-electron charge density from a first principles pseudopotential calculation by reconstructing the core region of an atom of choice. Here this method is applied to bulk silicon, and structure factors are derived and compared with experimental and Full-potential Linear Augmented Plane Wave results (FLAPW). We also compare with the result of assuming the core region is spherically symmetric, and with the result of constructing a charge density from the pseudo-valence density + frozen core electrons. Neither of these approximations provide accurate charge densities. The aspherical reconstruction is found to be as accurate as FLAPW results, and reproduces the residual error between the FLAPW and experimental results.Comment: 6 Pages, 3 figure