Successful completion of a cyclic ground test of a mercury ion auxiliary propulsion system

An engineering model Ion Auxiliary Propulsion System (IAPS) 8-cm thruster (S/N 905) has completed a life test at NASA Lewis Research Center. The mercury ion thruster successfully completed and exceeded the test goals of 2557 on/off cycles and 7057 hr of operation at full thrust. The final 1200 cycles and 3600 hr of the life test were conducted using an engineering model of the IAPS power electronics unit (PEU) and breadboard digital controller and interface unit (DCIU). This portion of the test is described in this paper with a charted history of thruster operating parameters and off-normal events. Performance and operating characteristics were constant throughout the test with only minor variations. The engineering model power electronics unit operated without malfunction; the flight software in the digital controller and interface unit was exercised and verified. Post-test inspection of the thruster revealed facility enhanced accelerator grid erosion but overall the thruster was in good condition. It was concluded that the thruster performance was not drastically degraded by time or cycles. Additional cyclic testing is currently under consideration

Tackling concentrated worklessness: integrating governance and policy across and within spatial scales

Spatial concentrations of worklessness remained a key characteristic of labour markets in advanced industrial economies, even during the period of decline in aggregate levels of unemployment and economic inactivity evident from the late 1990s to the economic downturn in 2008. The failure of certain localities to benefit from wider improvements in regional and national labour markets points to a lack of effectiveness in adopted policy approaches, not least in relation to the governance arrangements and policy delivery mechanisms that seek to integrate residents of deprived areas into wider local labour markets. Through analysis of practice in the British context, we explore the difficulties of integrating economic and social policy agendas within and across spatial scales to tackle problems of concentrated worklessness. We present analysis of a number of selected case studies aimed at reducing localised worklessness and identify the possibilities and constraints for effective action given existing governance arrangements and policy priorities to promote economic competitiveness and inclusion

Redistribution of cytoplasmic VEGF to the basolateral aspect of renal tubular cells in ischemia-reperfusion injury

Redistribution of cytoplasmic VEGF to the basolateral aspect of renal tubular cells in ischemia-reperfusion injury.BackgroundVascular endothelial growth factor (VEGF) mRNA and protein expression are increased by hypoxia in a variety of cell types and organs. In the kidney, however, chronic hypoxia does not up-regulate VEGF mRNA. This suggests that VEGF may be regulated by unique mechanisms in the kidney.MethodsUnilateral ischemia was induced in rats by vascular cross-clamping (40 min) followed by reperfusion (0, 20, 40, and 80 min). The distribution of VEGF protein was determined by immunohistochemical staining and Western blotting. mRNA was detected by Northern blotting and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemical staining for VEGF was verified using two VEGF antibodies. To further substantiate the immunohistochemical findings, laser scanning confocal fluorescence microscopy was used to demonstrate the distribution of VEGF protein in rat renal tubular epithelial cells (NRK52-E) subjected to hypoxia (40 min) and re-oxygenation (0, 5, 20, 40 and 80 min).ResultsNormal kidneys showed diffuse immunohistochemical staining for VEGF in all tubules of the renal cortex and medulla. Following ischemia, staining demonstrated a prominent shift of cytoplasmic VEGF to the basolateral aspect of tubular cells with both VEGF antibodies. The distribution of cytoplasmic VEGF returned to normal following 40 and 80 minutes of reperfusion. Western blots of cytoplasmic samples from ischemic kidneys reperfused for 0 and 20 minutes showed decreased levels of VEGF164 compared with normal (P < 0.01). VEGF164 and VEGF188 levels in the membrane fraction showed no change. Northern blots and semiquantitative RT-PCR showed no significant up-regulation of VEGF mRNA or change in the splice pattern. NRK52-E cells subjected to hypoxia and re-oxygenation for 0 and 5 minutes showed increased staining for VEGF compared with normal, with prominent VEGF staining at the periphery of the cell, similar to the appearance in ischemic kidneys. VEGF staining became more diffuse with further re-oxygenation.ConclusionAlthough synthesis of VEGF mRNA and protein is not increased during ischemia reperfusion injury, pre-existing VEGF in the tubular cell cytoplasm redistributes to the basolateral aspect of the cells. These data suggest that the kidney may have evolved unique patterns of VEGF regulation to cope with acute hypoxia

Identifying diamagnetic interactions in scattering and nonlinear optics

In the generic formulation of optical interactions there is, beyond the familiar electric and magnetic multipolar forms of coupling, an additional diamagnetization term that rarely receives attention. In fact it can give rise to effects that should be observable in the general context of nonlinear optical spectroscopy, as well as scattering. A quantum electrodynamical analysis reveals features of special interest in two specific cases: two-photon absorption and Rayleigh scattering. Diamagnetic contributions are seen to be dispersion free with regards to the frequency of input radiation, and can represent unique interactions within optical absorption and emission processes. There is also a configuration in which diamagnetic couplings, which are quadratic in the magnetic field, can supersede those that are dependent linearly on the electric field strength, such as the electric dipole. In this connection the influence of retroreflected circularly polarized light, which leads to a local distance dependence in magnitude of the electromagnetic fields, produces conditions in which the diamagnetization response can become a prominent feature in two-photon absorption

Cryptic Constituents: The Paradox of High Flux-Low Concentration Components of Aquatic Ecosystems

The interface between terrestrial ecosystems and inland waters is an important link in the global carbon cycle. However, the extent to which allochthonous organic matter entering freshwater systems plays a major role in microbial and higher-trophic-level processes is under debate. Human perturbations can alter fluxes of terrestrial carbon to aquatic environments in complex ways. The biomass and production of aquatic microbes are traditionally thought to be resource limited via stoichiometric constraints such as nutrient ratios or the carbon standing stock at a given timepoint. Low concentrations of a particular constituent, however, can be strong evidence of its importance in food webs. High fluxes of a constituent are often associated with low concentrations due to high uptake rates, particularly in aquatic food webs. A focus on biomass rather than turnover can lead investigators to misconstrue dissolved organic carbon use by bacteria. By combining tracer methods with mass balance calculations, we reveal hidden patterns in aquatic ecosystems that emphasize fluxes, turnover rates, and molecular interactions. We suggest that this approach will improve forecasts of aquatic ecosystem responses to warming or altered nitrogen usage

Teamwork Satisfaction And Student Attitudes Towards Online Learning During An Engineering Problem And Project Based Learning (PBL) Module

Research has shown that students that report high levels of learner satisfaction and positive attitudes are more likely to succeed within the online environment. This is reflected in the considerable body of research that focuses on these factors across a range of academic disciplines. By assessing students\u27 attitudes and satisfaction, educators gain a valuable affective perspective that allows for a more complete examination of strategy effectiveness. This paper examines teamwork satisfaction and student attitude towards online learning, while also highlighting elements of successful online collaboration as identified by students using the instruments developed by Hasler-Waters & Napier, Ku et al, and Tseng et al. This case study was carried out over a seven-week period with first-year engineering students (N=94), in a module entitled Design for Manufacture, during the COVID-19 pandemic. The findings revealed high levels of student satisfaction and attitudes towards working in teams in the online environment while participating in problem and project-based learning (PBL). Additionally, the findings outline multiple factors that affect the success of online collaboration. The relevance of these findings is then discussed in the context of an increasing move towards blended and online engineering education provision