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

Comparison and Analysis of Flexibility for Cutlery Made from Biobased/ Biodegradable and Petrochemical Materials

Biorenewable plastics can have the potential to reduce pollution, demand on landfills, and dependence on foreign petroleum caused by petroleum-based plastics. To determine the performance of biobased utensils compared to petrochemical based utensils, this study investigated 13 bio-based/biorenewable utensils and six petrochemical utensils in terms of weight, stiffness, and specific stiffness (stiffness/weight ratio). The Commercial Item Description (CID), which was created by the U.S. Government via the General Services Administration (GSA), is the current standard for testing utensils. The biobased products selected for this study were “commercial or industrial products (other than food or feed) that are composed, in whole, or in significant part, of biological products, renewable agricultural materials (including plant, animal, and marine materials), or forestry materials.” (USDA Bio Preferred Program, 2012). The results of this study show that the majority of biobased products exhibited similar strength and deflection under a given load as petrochemical products. This is the first comparison of this kind and it will allow designers and manufacturers to further optimize their products

A Hybrid Sequencing Approach Completes the Genome Sequence of Thermoanaerobacter ethanolicus JW 200

Thermoanaerobacter ethanolicus JW 200 has been identified as a potential sustainable biofuel producer due to its ability to readily ferment carbohydrates to ethanol. A hybrid sequencing approach, combining Oxford Nanopore and Illumina DNA sequence reads, was applied to produce a single contiguous genome sequence of 2,911,280 bp

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

Optical binding in nanoparticle assembly: Potential energy landscapes

Optical binding is an optomechanical effect exhibited by systems of micro- and nanoparticles, suitably irradiated with off-resonance laser light. Physically distinct from standing-wave and other forms of holographic optical traps, the phenomenon arises as a result of an interparticle coupling with individual radiation modes, leading to optically induced modifications to Casmir-Polder interactions. To better understand how this mechanism leads to the observed assemblies and formation of patterns in nanoparticles, we develop a theory in terms of optically induced energy landscapes exhibiting the three-dimensional form of the potential energy field. It is shown in detail that the positioning and magnitude of local energy maxima and minima depend on the configuration of each particle pair, with regards to the polarization and wave vector of the laser light. The analysis reveals how the positioning of local minima determines the energetically most favorable locations for the addition of a third particle to each equilibrium pair. It is also demonstrated how the result of such an addition subtly modifies the energy landscape that will, in turn, determine the optimum location for further particle additions. As such, this development represents a rigorous and general formulation of the theory, paving the way toward full comprehension of nanoparticle assembly based on optical binding