Solutions of Penrose's Equation

The computational use of Killing potentials which satisfy Penrose's equation is discussed. Penrose's equation is presented as a conformal Killing-Yano equation and the class of possible solutions is analyzed. It is shown that solutions exist in spacetimes of Petrov type O, D or N. In the particular case of the Kerr background, it is shown that there can be no Killing potential for the axial Killing vector.Comment: To appear in J. Math. Phy

Environmental protection requirements for scout/shuttle auxiliary stages

The requirements for enabling the Scout upper stages to endure the expected temperature, mechanical shock, acoustical and mechanical vibration environments during a specified shuttle mission were determined. The study consisted of: determining a shuttle mission trajectory for a 545 kilogram (1200 pound) Scout payload; compilation of shuttle environmental conditions; determining of Scout upper stages environments in shuttle missions; compilation of Scout upper stages environmental qualification criteria and comparison to shuttle mission expected environments; and recommendations for enabling Scout upper stages to endure the exptected shuttle mission environments

Phosphorus limitation of primary productivity in the eastern Mediterranean Sea

Although NO3- is generally considered to limit primary productivity in most of the world’s oceans, previous studies have suggested the Mediterranean Sea may be an exception. In this study of the southeastern Mediterranean, we found that all the PO43- was removed from the upper water column during the winter phytoplankton bloom in the core and boundary of a warm-core eddy, while measurable (0.3-0.6 µM) NO3- remained. The N:P (NO3-: PO43-) ratio in the core and boundary of the Cyprus eddy was 27.4 and the slope of the linear portion of the N vs. P scattergram with 25.5 with a positive intercept of 0.5 µM on the NO3- axis. A similar N:P ratio (28-29), slope (21-23), and intercept (0.9-1.1) was found for the water column across much of the southern Levantine basin. These data, taken together with the results of incubation experiments, lead us to conclude that the southeastern Mediterranean is strongly P limited. The degree of P limitation increases from west to east across the entire basin. We suggest that removal of PO43 by adsorbtion on Fe- rich dust particles may be an important process controlling the concentration of P in the water column

Investigation of conduction band structure, electron scattering mechanisms and phase transitions in indium selenide by means of transport measurements under pressure

In this work we report on Hall effect, resistivity and thermopower measurements in n-type indium selenide at room temperature under either hydrostatic and quasi-hydrostatic pressure. Up to 40 kbar (= 4 GPa), the decrease of carrier concentration as the pressure increases is explained through the existence of a subsidiary minimum in the conduction band. This minimum shifts towards lower energies under pressure, with a pressure coefficient of about -105 meV/GPa, and its related impurity level traps electrons as it reaches the band gap and approaches the Fermi level. The pressure value at which the electron trapping starts is shown to depend on the electron concentration at ambient pressure and the dimensionality of the electron gas. At low pressures the electron mobility increases under pressure for both 3D and 2D electrons, the increase rate being higher for 2D electrons, which is shown to be coherent with previous scattering mechanisms models. The phase transition from the semiconductor layered phase to the metallic sodium cloride phase is observed as a drop in resistivity around 105 kbar, but above 40 kbar a sharp nonreversible increase of the carrier concentration is observed, which is attributed to the formation of donor defects as precursors of the phase transition.Comment: 18 pages, Latex, 10 postscript figure

Local estimates for entropy densities in coupled map lattices

We present a method to derive an upper bound for the entropy density of coupled map lattices with local interactions from local observations. To do this, we use an embedding technique being a combination of time delay and spatial embedding. This embedding allows us to identify the local character of the equations of motion. Based on this method we present an approximate estimate of the entropy density by the correlation integral.Comment: 4 pages, 5 figures include

Temporal nutrient dynamics in the Mediterranean Sea in response to anthropogenic inputs

The temporal dynamics of the concentrations of nitrate (N), phosphate (P), and the N: P ratio in the upper water column (200-600 m) of the Mediterranean (MED) Sea were investigated using observational data (similar to 123,100 data points) collected between 1985 and 2014. The studied variables were found to evolve similarly in the western and easternMED Sea. In both basins, the N concentration increased during the first part of the observational period (1985-1998), and the temporal trend of N was broadly consistent with the history of riverine and atmospheric nitrogen input from populated areas in Europe, with a lag period of 20 years. In subsequent years, the N concentration was high and relatively constant between 1998 and 2005, after which N decreased gradually, although the decreasing trend was indistinct in the western basin. In particular, the trend of constant then declining N after 1998 is consistent with the history of pollutant nitrogen emissions from the European continent, allowing a 20 year lag following the introduction of regulation of pollutant nitrogen in the 1970s. The three-phase temporal transition in P in both basins was more consistent with the riverine phosphorus input, with a lag period of 20 years. Our analysis indicates that the recent dynamics of N and P in the upper MED Sea has been sensitive to the dynamics of anthropogenic nitrogen and phosphorus input from atmospheric deposition and rivers.1132Ysciescopu

The PML for rough surface scattering

In this paper we investigate the use of the perfectly matched layer (PML) to truncate a time harmonic rough surface scattering problem in the direction away from the scatterer. We prove existence and uniqueness of the solution of the truncated problem as well as an error estimate depending on the thickness and composition of the layer. This global error estimate predicts a linear rate of convergence (under some conditions on the relative size of the real and imaginary parts of the PML function) rather than the usual exponential rate. We then consider scattering by a half-space and show that the solution of the PML truncated problem converges globally at most quadratically (up to logarithmic factors), providing support for our general theory. However we also prove exponential convergence on compact subsets. We continue by proposing an iterative correction method for the PML truncated problem and, using our estimate for the PML approximation, prove convergence of this method. Finally we provide some numerical results in 2D.(C) 2008 IMACS. Published by Elsevier B.V. All rights reserved

Just plain Wronga?: a multimodal critical analysis of online payday loan discourse

Payday loans constitute one of the most rapidly expanding and controversial forms of consumer lending today. Payday lending – the selling of high-interest, short-term credit – has thrived in the wake of the decline of the traditional high street banking system and the reluctance on the part of many mainstream credit services, following the 2007/8 Global Financial Crisis, to lend to low income earners. This study critically examines the website of the industry leader in the UK, Wonga, a payday lender which recently rebranded and relaunched itself (in 2015) after being embroiled in a series of financial scandals. Our analysis centres on the new Wonga website, the gateway to its financial services, and identifies three inter-related discursive strategies through which the lender, in the wake of its financial misconduct, seeks to present itself as a reputable financial service provider, namely by (1) constructing the empowered and responsible borrower, (2) de-stigmatising both its service provision and its prospective customers, the payday borrower, and (3) minimising the consequences and risks associated with payday borrowing. We argue that, collectively, these strategies constitute an artful response by Wonga to the changing legislative and socio-economic contexts in which it and other payday lenders are now required to operate, permitting it to continue marketing and selling its high-interest rate financial services

The laboratory telerobotic manipulator program

New opportunities for the application of telerobotic systems to enhance human intelligence and dexterity in the hazardous environment of space are presented by the NASA Space Station Program. Because of the need for significant increases in extravehicular activity and the potential increase in hazards associated with space programs, emphasis is being heightened on telerobotic systems research and development. The Laboratory Telerobotic Manipulator (LTM) program is performed to develop and demonstrate ground-based telerobotic manipulator system hardware for research and demonstrations aimed at future NASA applications. The LTM incorporates traction drives, modularity, redundant kinematics, and state-of-the-art hierarchical control techniques to form a basis for merging the diverse technological domains of robust, high-dexterity teleoperations and autonomous robotic operation into common hardware to further NASA's research

Mutant huntingtin enhances activation of dendritic Kv4 K+ channels in striatal spiny projection neurons

Huntington\u27s disease (HD) is initially characterized by an inability to suppress unwanted movements, a deficit attributable to impaired synaptic activation of striatal indirect pathway spiny projection neurons (iSPNs). To better understand the mechanisms underlying this deficit, striatal neurons in ex vivo brain slices from mouse genetic models of HD were studied using electrophysiological, optical and biochemical approaches. Distal dendrites of iSPNs from symptomatic HD mice were hypoexcitable, a change that was attributable to increased association of dendritic Kv4 potassium channels with auxiliary KChIP subunits. This association was negatively modulated by TrkB receptor signaling. Dendritic excitability of HD iSPNs was rescued by knocking-down expression of Kv4 channels, by disrupting KChIP binding, by restoring TrkB receptor signaling or by lowering mutant-Htt (mHtt) levels with a zinc finger protein. Collectively, these studies demonstrate that mHtt induces reversible alterations in the dendritic excitability of iSPNs that could contribute to the motor symptoms of HD