Abundance analyses of helium-rich subluminous B stars

The connection between helium-rich hot subdwarfs of spectral types O and B (He-sdB) has been relatively unexplored since the latter were found in significant numbers in the 1980's. In order to explore this connection further, we have analysed the surface composition of six He-sdB stars, including LB 1766, LB 3229, SB 21 (= Ton-S 137 = BPS 29503-0009), BPS 22940-0009, BPS 29496-0010, and BPS 22956-0094. Opacity-sampled line-blanketed model atmospheres have been used to derive atmospheric properties and elemental abundances. All the stars are moderately metal-poor compared with the Sun ([Fe/H] ~ -0.5). Four stars are nitrogen-rich, two of these are carbon-rich, and at least four appear to be neon-rich. The data are insufficient to rule out binarity in any of the sample. The surface composition and locus of the N-rich He-sdBs are currently best explained by the merger of two helium white dwarfs, or possibly by the merger of a helium white dwarf with a post-sdB white dwarf. C-rich He-sdBs require further investigation.Comment: Accepted 2010 July

Breit-Wigner-Fano lineshapes in Raman spectra of graphene

Excitation of electron-hole pairs in the vicinity of the Dirac cone by the Coulomb interaction gives rise to an asymmetric Breit-Wigner-Fano lineshape in the phonon Raman spectra in graphene. This asymmetric lineshape appears due to the interference effect between the phonon spectra and the electron-hole pair excitation spectra. The calculated Breit-Wigner-Fano asymmetric factor 1/qBWF as a function of the Fermi energy shows a V-shaped curve with a minimum value at the charge neutrality point and gives good agreement with the experimental result.Comment: 15 pages, 4 figure

Probing the gateway to superheavy nuclei in cranked relativistic Hartree-Bogoliubov theory

The cranked relativistic Hartree+Bogoliubov theory has been applied for a systematic study of the nuclei around 254No, the heaviest nuclei for which detailed spectroscopic data are available. The deformation, rotational response, pairing correlations, quasi-particle and other properties of these nuclei have been studied with different relativistic mean field (RMF) parametrizations. For the first time, the quasi-particle spectra of odd deformed nuclei have been calculated in a fully self-consistent way within the framework of the RMF theory. The energies of the spherical subshells, from which active deformed states of these nuclei emerge, are described with an accuracy better than 0.5 MeV for most of the subshells with the NL1 and NL3 parametrizations. However, for a few subshells the discrepancy reach 0.7-1.0 MeV. The implications of these results for the study of superheavy nuclei are discussed.Comment: 7 pages, 3 figures, Proceedings of the Conference on Frontiers of Nuclear Structure, Berkeley, California, July 29th - August 2nd, 2002, UC Berkeley, Clark Kerr Campus, in pres

Origin of electronic Raman scattering and the Fano resonance in metallic carbon nanotubes

Fano resonance spectra for the G band in metallic carbon nanotubes are calculated as a function of laser excitation energy in which the origin of the resonance is given by an interference between the continuous electronic Raman spectra and the discrete phonon spectra. We found that the second-order scattering process of the non-zero q electron-electron interaction is more relevant to the continuous spectra rather than the q = 0 first-order process because the q = 0 direct Coulomb interaction vanishes due to the symmetry of the two sublattices of a nanotube. We also show that the RBM spectra of metallic carbon nanotubes have an asymmetric line shape which previously had been overlooked.Comment: 5 pages, 5 figures, submitted to Physical Review Letters on February 4, 201

Dynamic organization schemes for cooperative proxy caching

In a generic cooperative caching architecture, web proxies form a mesh network. When a proxy cannot satisfy a request, it forwards the request to the other nodes of the mesh. Since a local cache cannot fulfill the majority of the arriving requests (typical values of the local hit ratio are about 30-50%), the volume of queries diverted to neighboring nodes can substantially grow and may consume considerable amount of system resources. A proxy does not need to cooperate with every node of the mesh due to the following reasons: (i) the traffic characteristics may be highly diverse; (ii) the contents of some nodes may extensively overlap; (iii) the inter-node distance might be too large. Furthermore, organizing N proxies in a mesh topology introduces scalability problems, since the number of queries is of the order of N/sup 2/. Therefore, restricting the number of neighbors for each proxy to k < N - 1 will likely lead to a balanced trade-off between query overhead and hit ratio, provided cooperation is done among useful neighbors. For a number of reasons the selection of useful neighbors is not efficient. An obvious reason is that web access patterns change dynamically. Furthermore, availability of proxies is not always globally known. This paper proposes a set of algorithms that enable proxies to independently explore the network and choose the k most beneficial (according to local criteria) neighbors in a dynamic fashion. The simulation experiments illustrate that the proposed dynamic neighbor reconfiguration schemes significantly reduce the overhead incurred by the mesh topology while yielding higher hit ratios compared to the static approach.published_or_final_versio

Comparative Analysis of V-Akt Murine Thymoma Viral Oncogene Homolog 3 (AKT3) Gene between Cow and Buffalo Reveals Substantial Differences for Mastitis

AKT3 gene is a constituent of the serine/threonine protein kinase family and plays a crucial role in synthesis of milk fats and cholesterol by regulating activity of the sterol regulatory element binding protein (SREBP). AKT3 is highly conserved in mammals and its expression levels during the lactation periods of cattle are markedly increased. AKT3 is highly expressed in the intestine followed by mammary gland and it is also expressed in immune cells. It is involved in the TLR pathways as effectively as proinflammatory cytokines. The aims of this study were to investigate the sequences differences between buffalo and cow. Our results showed that there were substantial differences between buffalo and cow in some exons and noteworthy differences of the gene size in different regions. We also identified the important consensus sequence motifs, variation in 2000 upstream of ATG, substantial difference in the “3′UTR” region, and miRNA association in the buffalo sequences compared with the cow. In addition, genetic analyses, such as gene structure, phylogenetic tree, position of different motifs, and functional domains, were performed to establish their correlation with other species. This may indicate that a buffalo breed has potential resistance to disease, environment changes, and airborne microorganisms and some good production and reproductive traits

Pemodelan Numerik Cfd pada Lambung Torpedo

Torpedo pada umumnya berbentuk tabung yang memiliki sistem penggerak sendiri. Torpedo yang dianalisa ini merupakan perpaduan dari desain torpedo jenis MK-44 dan MK-46 menjadi sebuah desain baru yang diharapkan dapat memperoleh performa yang lebih optimal. Dengan menggunakan perangkat lunak berbasis numerik CFD dapat dianalisa efek hidrodinamika yang timbul pada torpedo seperti: distribusi tekanan yang terjadi pada lambung torpedo, arah aliran fluida saat torpedo bergerak, streamline desain torped

Solidworks Simulation of Mechanical Properties of Recycled Plastics/Nanocomposite Faces Sandwich Panels

Sandwich panels are lightweight, high strength materials desired by engineers for various applications. However, many contributions cited the replacement of the metallic surfaces with reinforced polymeric composites for additional weight reduction purpose but none observed for recycled plastics. Accordingly, this work plans to investigate the mechanical behavior of sandwich panels made of recycled plastic/Nano reinforced composites under tension, compression, and bending load using Solidworks simulation. The data were obtained from previous works, and the complementary data were collected using different approaches. All models revealed that polycarbonate (PC) skin dominated over polypropylene and high-density polyethylene due to the highest modulus of elasticity. However, the results indicated that the core unless reinforced the outer skins will be separated as a result of residual strain at interfaces. Consequently, the core of PC skin sandwich panel reinforced with two thin sheets which lead to improvement in loading endurance from 500 to 1500N without exceeding the allowable limits of the materials and leading to the birth of environmentally intimated material termed green sandwich panel

Simple Model for Active Isolation of Machine Foundations by Open Trenches

Ground disturbance due to waves generated by a machine foundation can be detrimental to adjacent structures or operation of sensitive equipment nearby. For machine foundations vibrating at moderate to high frequencies, the amplitude of ground motion can be reduced significantly by installing a wave barrier around the source. A three-dimensional boundary element algorithm incorporating quadratic elements has been used to perform an extensive parametric study on the effectiveness of open trenches as wave barriers. Based on the results of the study, a simple model in the form of an algebraic expression is developed for estimating the vibration screening effectiveness of open trench wave barriers. Furthermore, through comparisons with published field test data and rigorous boundary element solutions, the validity of the simple model is established