Conformal Collineations and Ricci Inheritance Symmetry in String Cloud and String Fluids

Conformal collineations (a generalization of conformal motion) and Ricci inheritance collineations, defined by $\pounds_\xi R_{ab}=2\alpha R_{ab}$, for string cloud and string fluids in general relativity are studied. By investigating the kinematical and dynamical properties of such fluids and using the field equations, some recent studies on the restrictions imposed by conformal collineations are extended, and new results are found.Comment: 12 pages, LaTeX, no figures, to appear in Int. J. Mod. Phys.

Spacelike Ricci Inheritance Vectors in a Model of String Cloud and String Fluid Stress Tensor

We study the consequences of the existence of spacelike Ricci inheritance vectors (SpRIVs) parallel to $x^a$ for model of string cloud and string fluid stress tensor in the context of general relativity. Necessary and sufficient conditions are derived for a spacetime with a model of string cloud and string fluid stress tensor to admit a SpRIV and a SpRIV which is also a spacelike conformal Killing vector (SpCKV). Also, some results are obtained.Comment: 11 page

Lipid levels in HIV-positive men receiving anti-retroviral therapy are not associated with copy number variation of reverse cholesterol transport pathway genes Genetics

Background: The exacerbation of HIV-1 associated dyslipidemia seen in a subset of patients receiving anti-retroviral therapy suggests that genetic factors put these individuals at greater risk of cardiovascular disease. Single nucleotide polymorphisms (SNPs) within genes of and influencing the reverse cholesterol transport (RCT) pathway are associated with lipid levels but little is known regarding their copy number variation (CNV). This form of quantitative genetic variation has the potential to alter the amount of gene product made, thereby also influencing lipid metabolism. Results: To examine if CNV in RCT pathway genes was associated with altered serum lipid profiles in HIV-positive individuals receiving therapy, we designed a custom multiplex ligation-dependent probe amplification assay to screen 16 RCT genes within a subset of individuals from the Multicenter AIDS Cohort Study who show extreme lipid phenotypes. Verification of CNV was performed using a custom NanoString assay, and the Illumina HT-12 mRNA expression microarray was used to determine the influence of copy number on gene expression. Among the RCT genes, CNV was observed to be extremely rare. The only CNV seen was in the CETP gene, which showed a loss of copy in 1 of the 320 samples (0.3 %) in our study. The genes in our study showed little variation in expression between individuals, and the variation seen was not related to any detected CNV. Conclusions: Whole gene CNV is uncommon in RCT pathway genes, and not a major factor in the development of highly active antiretroviral therapy (HAART) associated dyslipidemia

A solar flare type increase in cosmic rays at low latitudes

During the hour following the big solar flare on 23-2-1956, an average increase of +5.7 ± 0.8% has been observed in meson intensity measured with standard telescopes at Ahmedabad, Kodaikanal and Trivandrum. This is the first report of a significant solar flare type increase in cosmic rays near the geomagnetic equator. If the increase is due to solar protons travelling in approximately direct paths, the energy of the protous must extend from about 35-67.5 Bev. It is estimated that the average flux of such protons is approximately equal to 1.5 times the flux of general cosmic ray intensity in the same energy range. During the hour, the sun is estimated to have emitted more than 1028 protons of about 50 Bev energy

Ricci Collineations for type B warped space-times

We present the general structure of proper Ricci Collineations (RC) for type B warped space-times. Within this framework, we give a detailed description of the most general proper RC for spherically symmetric metrics. As examples, static spherically symmetric and Friedmann-Robertson-Walker space-times are considered.Comment: 18 pages, Latex, To appear in GR

Sintering of calcium phosphates with a femtosecond pulsed laser for hard tissue engineering

The authors acknowledge support from the sponsors of this work; the EPSRC LUMIN (EP/K020234/1) and EU-Marie-Curie-IAPP LUSTRE (324538) projects.Direct laser sintering on hard tissues is likely to open new pathways for personalised medicine. To minimise irradiation damage of the surrounding soft tissues, lasers operating at wavelengths that are ‘safe’ for the tissues and biomaterials with improved optical properties are required. In this work laser sintering is demonstrated with the use of an ultrafast, femtosecond (100 fs) pulsed laser operating at a wavelength of 1045 nm and two existing calcium phosphate minerals (brushite and hydroxyapatite) which have been improved after doping with iron (10 mol%). Femtosecond laser irradiation caused transformation of the Fe3+-doped brushite and Fe3+-doped HAp samples into β-calcium pyrophosphate and calcium-iron-phosphate, respectively, with simultaneous evidence for microstructural sintering and densification. After estimating the temperature profile at the surface of the samples we suggest that soft tissues over 500 μm from the irradiated zone would be safe from thermal damage. This novel laser processing provides a means to control the phase constitution and the morphology of the finished surfaces. The porous structure of β-pyrophosphate might be suitable for applications in bone regeneration by supporting osteogenic cell activity while, the densified Fe3+-rich calcium-iron-phosphate may be promising for applications like dental enamel restoration.PostprintPeer reviewe