The effects of atomic oxygen on the thermal emittance of high temperature radiator surfaces

Radiator surfaces on high temperature space power systems such as SP-100 space nuclear power system must maintain a high emittance level in order to reject waste heat effectively. One of the primary materials under consideration for the radiators is carbon-carbon composite. Since carbon is susceptible to attack by atomic oxygen in the low earth orbital environment, it is important to determine the durability of carbon composites in this environment as well as the effect atomic oxygen has on the thermal emittance of the surface if it is to be considered for use as a radiator. Results indicate that the thermal emittance of carbon-carbon composite (as low as 0.42) can be enhanced by exposure to a directed beam of atomic oxygen to levels above 0.85 at 800 K. This emittance enhancement is due to a change in the surface morphology as a result of oxidation. High aspect ratio cones are formed on the surface which allow more efficient trapping of incident radiation. Erosion of the surface due to oxidation is similar to that for carbon, so that at altitudes less than approximately 600 km, thickness loss of the radiator could be significant (as much as 0.1 cm/year). A protective coating or oxidation barrier forming additive may be needed to prevent atomic oxygen attack after the initial high emittance surface is formed. Textured surfaces can be formed in ground based facilities or possibly in space if emittance is not sensitive to the orientation of the atomic oxygen arrival that forms the texture

Cost-Effective Water Quality Management Strategies in Central and Eastern Europe

Many countries in Central and Eastern Europe will be formulating new environmental regulations within the next few years. Among the many topics which these are likely to address is the development of control policies for waste-water dischargers, including municipal sewage treatment plants. In Western Europe and North America, standards have relied heavily upon so-called "best available technology" control policies, which require dischargers to use treatment processes that reduce emissions of BOD, phosphorus, and nitrogen as much as is technically feasible. However, these technologies are often very expensive. Given the state of Central and Eastern European economies, less expensive methods to improve water quality should be seriously considered. In this paper, we investigate control policies, alternative sewage treatment possibilities, water quality models, and optimization methods required to identify least-cost strategies to improve the region's ambient water quality. We survey the costs and technical capacities of a variety of treatment techniques, ranging from simple primary or mechanical treatment to advanced technology to remove nutrients. We also survey existing water quality models and show how they can be adapted to the policy analysis problem. Finally, we characterize a number of potential policies in terms that are amenable to analysis of their costs and ambient quality impacts. Focussing on municipal waste-water treatment plants and water quality in rivers and streams, we show how these techniques can be integrated and applied. We conclude with an empirical example based on the Nitra, a small, heavily contaminated river in Slovakia

An automated and versatile ultra-low temperature SQUID magnetometer

We present the design and construction of a SQUID-based magnetometer for operation down to temperatures T = 10 mK, while retaining the compatibility with the sample holders typically used in commercial SQUID magnetometers. The system is based on a dc-SQUID coupled to a second-order gradiometer. The sample is placed inside the plastic mixing chamber of a dilution refrigerator and is thermalized directly by the 3He flow. The movement though the pickup coils is obtained by lifting the whole dilution refrigerator insert. A home-developed software provides full automation and an easy user interface.Comment: RevTex, 10 pages, 10 eps figures. High-resolution figures available upon reques

Hippocampal network oscillations - recent insights from in vitro experiments.

Network oscillations are present throughout the mammalian brain. They are important for certain cognitive functions, such as learning and memory. The hippocampus exhibits prominent oscillations similar to those seen in other parts of the cortex. Due to its highly organised lamellar structure, ex vivo and in vitro preparations from the hippocampus have provided experimental models within which to study network oscillations. As such, experiments in hippocampal slices continue to progress our understanding about both the mechanisms and functions of cortical network oscillations. Here, advances from the past two years are summarised, and the current state of the field discussed.The authors are grateful for research funding from the BBSRC, UK. JLB is supported by a CASE studentship from the BBSRC.This is the final published version. It is also available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0959438814001627#

The Hippocampal Cacophony: Multiple Layers of Communication

Locally generated gamma oscillations synchronize spikes, but the nature of coupling between regions remains unclear. In this issue of Neuron, Schomburg et al. (2014) show that afferent gamma input fails to entrain hippocampal output, suggesting limited propagation of gamma waves

Oxidation and protection of fiberglass-epoxy composite masts for photovoltaic arrays in the low Earth orbital environment

Fiberglass-epoxy composites are considered for use as structural members for the mast of the space station solar array panel. The low Earth orbital environment in which space station is to operate is composed mainly of atomic oxygen, which has been shown to cause erosion of many organic materials and some metals. Ground based testing in a plasma asher was performed to determine the extent of degradation of fiberglass-epoxy composites when exposed to a simulated atomic oxygen environment. During exposure, the epoxy at the surface of the composite was oxidized, exposing individual glass fibers which could easily be removed. Several methods of protecting the composite were evaluated in an atomic oxygen environment and with thermal cycling and flexing. The protection techniques evaluated to date include an aluminum braid covering, an indium-tin eutectic and a silicone based paint. The open aluminum braid offered little protection while the CV-1144 coating offered some initial protection against atomic oxygen, but appears to develop cracks which accelerate degradation when flexed. Coatings such as the In-Sn eutectic may provide adequate protection by containing the glass fibers even though mass loss still occurs

Decomposition of time-covariant operations on quantum systems with continuous and/or discrete energy spectrum

Every completely positive map G that commutes which the Hamiltonian time evolution is an integral or sum over (densely defined) CP-maps G_\sigma where \sigma is the energy that is transferred to or taken from the environment. If the spectrum is non-degenerated each G_\sigma is a dephasing channel followed by an energy shift. The dephasing is given by the Hadamard product of the density operator with a (formally defined) positive operator. The Kraus operator of the energy shift is a partial isometry which defines a translation on R with respect to a non-translation-invariant measure. As an example, I calculate this decomposition explicitly for the rotation invariant gaussian channel on a single mode. I address the question under what conditions a covariant channel destroys superpositions between mutually orthogonal states on the same orbit. For channels which allow mutually orthogonal output states on the same orbit, a lower bound on the quantum capacity is derived using the Fourier transform of the CP-map-valued measure (G_\sigma).Comment: latex, 33 pages, domains of unbounded operators are now explicitly specified. Presentation more detailed. Implementing the shift after the dephasing is sometimes more convenien

Compactness properties of operator multipliers

We continue the study of multidimensional operator multipliers initiated in [arXiv:math/0701645]. We introduce the notion of the symbol of an operator multiplier. We characterise completely compact operator multipliers in terms of their symbol as well as in terms of approximation by finite rank multipliers. We give sufficient conditions for the sets of compact and completely compact multipliers to coincide and characterise the cases where an operator multiplier in the minimal tensor product of two C*-algebras is automatically compact. We give a description of multilinear modular completely compact completely bounded maps defined on the direct product of finitely many copies of the C*-algebra of compact operators in terms of tensor products, generalising results of Saar

Evaluation of a Salve or Two Novel Winter Teat Dips to Maintain or Enhance Teat Integrity During Winter

Winter conditions can lead to rapid dehydration and cracking of teat tissue, thus increasing mastitis risks. The objectives of these three winter trials were to compare application of a salve or 2 new novel commercial winter teat dip products (\u3e 70% propylene glycol plus fatty acid germicide) to an existing commercially available teat dip (good germicide and skin conditioning) and best management winter milking practices. Overall results for the 3 trials suggest slight (glycol) to no (salve) positive effect on teat end health (especially cracking) when tested in comparison to the use of a good milking and winter dipping practices and a very good commercial post-milking dip used in this herd. There was a slight decrease in % teats cracked with glycol dips following rapid temperature changes. However, none of the treatments were effective in completely alleviating teat end changes due to weather