DD-Dimensional Gravity from (D+1)(D+1) Dimensions

We generalise Wesson's procedure, whereby vacuum $(4+1)-$dimensional field equations give rise to $(3+1)-$dimensional equations with sources, to arbitrary dimensions. We then employ this generalisation to relate the usual $(3+1)-$dimensional vacuum field equations to $(2+1)-$dimensional field equations with sources and derive the analogues of the classes of solutions obtained by Ponce de Leon. This way of viewing lower dimensional gravity theories can be of importance in establishing a relationship between such theories and the usual 4-dimensional general relativity, as well as giving a way of producing exact solutions in $(2+1)$ dimensions that are naturally related to the vacuum $(3+1)-$dimensional solutions. An outcome of this correspondence, regarding the nature of lower dimensional gravity, is that the intuitions obtained in $(3+1)$ dimensions may not be automatically transportable to lower dimensions. We also extend a number of physically motivated solutions studied by Wesson and Ponce de Leon to $(D+1)$ dimensions and employ the equivalence between the $(D+1)$ Kaluza-Klein theories with empty $D-$dimensional Brans-Dicke theories (with $\omega=0$) to throw some light on the solutions derived by these authors.Comment: 11 pages, latex, published in CQG vol. 12 no. 1

Imaging and Spectroscopy of Ultra Steep Spectrum Radio Sources

We present a sample of 40 Ultra Steep Spectrum (USS, $\alpha \leq -1.3$, $S_{\nu}\propto \nu^{\alpha}$) radio sources selected from the Westerbork in the Southern Hemisphere (WISH) catalog. The USS sources have been imaged in K--band at the Cerro Tololo Inter-American Observatory (CTIO) and with the Very Large Telescope at Cerro Paranal. We also present VLT, Keck and Willian Herschel Telescope(WHT) optical spectroscopy of 14 targets selection from 4 different USS samples. For 12 sources, we have been able to determine the redshifts, including 4 new radio galaxies at z > 3. We find that most of our USS sources have predominantly small (6'') radio sizes and faint magnitudes (K~18). The mean K-band counterpart magnitude is $\bar{K}$=18.6. The expected redshift distribution estimated using the Hubble K-z diagram has a mean of $\bar{z}_{exp}$$\sim$2.13, which is higher than the predicted redshift obtained for the SUMSS-NVSS sample and the expected redshift obtained in the 6C$^{**}$ survey. The compact USS sample analyzed here may contain a higher fraction of galaxies which are high redshift and/or are heavily obscured by dust. Using the 74, 352 and 1400 MHz flux densities of a sub-sample, we construct a radio colour-colour diagram. We find that all but one of our USS sources have a strong tendency to flatten below 352 MHz. We also find that the highest redshift source from this paper (at z=3.84) does not show evidence for spectral flattening down to 151 MHz. This suggests that very low frequency selected USS samples will likely be more efficient to find high redshift galaxies.Comment: Accepted for publication in MNRAS, 14 pages including 44 PostScript figures and 4 tables. Version with all figures available from http://www.eso.org/~cdebreuc/papers.htm

The Terceira Rift, Azores: a melt inclusion study of submarine lavas

The Azores plateau, a bathymetric high, is seated on an anomalous mantle domain located in the Azores Triple Junction where the American, EUR and AFR lithospheric plates meet. The cause for these anomalies is controversial but many authors consider the presence of an anomalously hot/wet enriched mantle probably supplied by a plume [3]. The origin, size and present location of the plume is under debate but an area near Terceira is the favoured plume centre [2]. The Terceira Rift (TR) defines the EUR/AFR plate boundary of the Azores triple junction. The TR is a 550 km long, generally ESE trending line of volcanic massifs along the axis (e.g. São Miguel, D. João de Castro, Terceira and Graciosa) alternating with deep basins (e.g. Hirondelle basin) interpreted as volcanically unfilled rift valley segments [3]. Vesicular, porphyritic basalts were sampled along the Terceira Rift during Portuguese scientific cruises (EMEPC 2007-2009). Initial studies focused on the adjacent areas Don João de Castro - DJC (submarine volcano) and Hirondelle - Hir (basin). Major and trace element data of phenocrysts (olivine, clinopyroxene, plagioclase), groundmass and exposed melt inclusions found in these vesicular lavas depict only slight differences between the two sites. DJC samples depict higher Fo and Mg# in olivine and clinopyroxene, respectively. Chondrite-normalized REE data indicate that groundmass material is LREE-enriched in both Hir and DJC lavas. Exposed melt inclusions (MI) show similar REE patterns compared to their hosts. Clinopyroxene in both sites display L-MREE enriched, HREE depleted sinusoidal patterns. MI were found in olivine, clinopyroxene and plagioclase phenocrysts. MI are glassy to completely opaque and devitrified, with one or more bubbles, and sulfide globules (SG). SG are spherical, depict two-phase lamellar intergrowths of Fe-Ni and Cu-Fe phases, and are ubiquitous in DJC and Hir lava samples. Some lavas display SG within clinopyroxene-hosted MI and dispersed in the groundmass. Preliminary data suggest that lavas found in these areas of the Terceira Rift were sulfur-saturated in different stages of their evolution; during early fractionation and prior to eruption. The geochemistry of melt inclusion will contribute to the understanding of mantle source, melting and mixing processes in the Terceira Rift, Azores

Electrostatic Properties of PE and PTFE Subjected to Atmospheric Pressure Plasma Treatment; Correlation of Experimental Results with Atomistic Modeling

The use of an atmospheric pressure glow discharge (APGD) plasma was used at KSC to increase the hydrophilicity of spaceport materials to enhance their surface charge dissipation and prevent possible ESD in spaceport operations. Significant decreases in charge decay times were observed after tribocharging the materials using the standard KSC tribocharging test. The polarity and amount of charge transferred was dependent upon the effective work function differences between the respective materials. In this study, polyethylene (PE) and polytetrafluoroethylene (PTFE) were exposed to a He+O2 APGD. The pre and post treatment surface chemistry was analyzed by X-ray photoelectron spectroscopy and contact angle measurements. Semi-empirical and ab initio calculations were performed to correlate the experimental results with some plausible molecular and electronic structure features of the oxidation process. For the PE, significant surface oxidation was observed, as indicated by XPS showing C-O, C=O, and O-C=O bonding, and a decrease in the surface contact angle from 98.9 deg to 61.2 deg. For the PTFE, no C-O bonding appeared and the surface contact angle increased indicating the APGD only succeeded in cleaning the PTFE surface without affecting the surface structure. The calculations using the PM3 and DFT methods were performed on single and multiple oligomers to simulate a wide variety of oxidation scenarios. Calculated work function results suggest that regardless of oxidation mechanism, e.g. -OH, =0 or a combination thereof, the experimentally observed levels of surface oxidation are unlikely to lead to a significant change in the electronic structure of PE and that its increased hydrophilic properties are the primary reason for the observed changes in its electrostatic behavior. The calculations for PTFE argue strongly against significant oxidation of that material, as confirmed by the XPS results

Microheterogeneity and interspecific variability of the nuclear sperm proteins from Mytilus

AbstractWe have used acetic acid-urea-triton (AUT) gel electrophoresis and ionic exchange chromatography in order to analyze the interspecific, variability and microheterogeneity pattern of the protamine-like (PL) protiens of the sperm or 4 different species or the bivalve molluse, Mytilus. We have found that based upon these 2 criteria, it is possible to unambiguously distinguish each species from the rest. We have thus been able to corroborate the identity or M. irossulus, We have also analyzed the amino acid composition of some of the PL components for each different species, In the case of the PL-11* fraction, we have analyzed the composition of its major protein subcomponents

Nonlinear unmixing of hyperspectral images: Models and algorithms

When considering the problem of unmixing hyperspectral images, most of the literature in the geoscience and image processing areas relies on the widely used linear mixing model (LMM). However, the LMM may be not valid, and other nonlinear models need to be considered, for instance, when there are multiscattering effects or intimate interactions. Consequently, over the last few years, several significant contributions have been proposed to overcome the limitations inherent in the LMM. In this article, we present an overview of recent advances in nonlinear unmixing modeling

Training Neural Networks with Universal Adiabatic Quantum Computing

The training of neural networks (NNs) is a computationally intensive task requiring significant time and resources. This paper presents a novel approach to NN training using Adiabatic Quantum Computing (AQC), a paradigm that leverages the principles of adiabatic evolution to solve optimisation problems. We propose a universal AQC method that can be implemented on gate quantum computers, allowing for a broad range of Hamiltonians and thus enabling the training of expressive neural networks. We apply this approach to various neural networks with continuous, discrete, and binary weights. Our results indicate that AQC can very efficiently find the global minimum of the loss function, offering a promising alternative to classical training methods.Comment: 14 page

Application of Glow Discharge Plasma to Alter Surface Properties of Materials

Some polymer materials that are considered important for spaceport operations are rendered noncompliant when subjected to the Kennedy Space Center (KSC) Standard electrostatic testing. These materials operate in stringent environmental conditions, such as high humidity. Treating materials that fail electrostatic testing and altering their surface properties so that they become compliant would result in considerable cost savings. Significant improvement in electrostatic dissipation of Saf-T-Vu PVC after treatment with air Atmospheric Plasma Glow Discharge (APGD) was observed and the material now passed the KSC electrostatic test. The O:C ratio on the surface, as monitored by X-ray Photoelectron Spectroscopy, increased from 0.165 tO 0.275 indicating enhanced oxidation, and surface contact angle measurements decreased from 107.5 to 72.6 showing increased hydrophilicity that accounted for the increased conductivity. Monitoring of the aging showed that the materials hydrophobic recovery resulted in it failing the electrostatic test 30 hours after treatment. This was probably due to the out-diffusion of the added Zn, Ba, and Cd salt stabilizers detected on the surface and/or diffusion of low molecular weight oligomers. On going work includes improving the long term hydrophilicity by optimizing the APGD process with different gas mixtures. Treatment of other spaceport materials is also presented