Galactic R Coronae Borealis Stars: The C-2 Swan Bands, The Carbon Problem, And The C-12/C-13 Ratio

Observed spectra of R Coronae Borealis (RCB) and hydrogen-deficient carbon (HdC) stars are analyzed by synthesizing the C-2 Swan bands (1, 0), (0, 0), and (0, 1) using our detailed line list and the Uppsala model atmospheres. The (0, 1) and (0, 0) C-2 bands are used to derive the C-12 abundance, and the (1, 0) (CC)-C-12-C-13 band to determine the C-12/C-13 ratios. The carbon abundance derived from the C-2 Swan bands is about the same for the adopted models constructed with different carbon abundances over the range 8.5 (C/He = 0.1%) to 10.5 (C/He = 10%). Carbon abundances derived from C I lines are about a factor of four lower than the carbon abundance of the adopted model atmosphere over the same C/He interval, as reported by Asplund et al., who dubbed the mismatch between adopted and derived C abundance as the "carbon problem." In principle, the carbon abundances obtained from C-2 Swan bands and that assumed for the model atmosphere can be equated for a particular choice of C/He that varies from star to star. Then, the carbon problem for C-2 bands is eliminated. However, such C/He ratios are in general less than those of the extreme helium stars, the seemingly natural relatives to the RCB and HdC stars. A more likely solution to the C-2 carbon problem may lie in a modification of the model atmosphere's temperature structure. The derived carbon abundances and the C-12/C-13 ratios are discussed in light of the double degenerate and the final flash scenarios.Robert A. Welch Foundation of Houston, TX F-634McDonald Observator

PSORIASIS: THE IMPLICATIONS OF OXIDATIVE STRESS LED PATHOGENESIS FOR DIETETIC INTERVENTIONS

Psoriasis represents the major common dermatosis of multifactorial determination. The fundamental evolutionary biology of environs bearing skin and revelations on multistep involvement of oxidative stress in pathogenic events of psoriasis make strong case for medical contemplation. Very clearly the perspectives of dietetics in avoidance and amelioration of psoriasis, emerge as the least addressed in contemporary care, even at speciality level. An attempt is made to discuss multistep pathogenic indulgence of oxidative stress to emphasize the worth attention to dietetic intervention toward rational and desired management of psoriasis

Optical Observations and Multiband Modelling of the Afterglow of GRB 041006: Evidence of A Hard Electron Energy Spectrum

We present the CCD Cousins R band photometric observations of the afterglow of GRB 041006. The multiband afterglow evolution is modelled using an underlying `hard' electron energy spectrum with a $p_1 \sim 1.3$. The burst appears to be of very low energy ($E \sim 10^{48}$ ergs) confined to a narrow cone of opening angle $\theta \sim 2.3^{\circ}$. The associated supernova is compared with SN1998bw and is found to be brighter.Comment: Accepted for publication in Bull. Astr. Soc. India (BASI

Retinal Inflammaging: Pathogenesis and Prevention

Macula lutea, the yellow sot or fovea centralis in eye serves the distinctive central vision in perceiving visual cues and contributing to task performance. Impaired visual acuity in later years in life, compromises safety, productivity and life quality. Carotenoid pigment content declines with cumulation of light induced damage through aging process in retina. The progression of resultant macular degeneration is aggravated by oxidative stress, inflammation, raised blood sugar and vasculopathy associating aging. Senescent dry degeneration involves drusen (a compound of glycolipid and glycol-conjugate core) deposition that impairs metabolic connectivity of upper layers of retina with choroid. Degeneration of retinal pigment epithelium (RPE) and photoreceptors thus, results. The late more severe form of age related macular degeneration (AMD), involves factors inducing choroidal neo-vascularization. Leaky neo-capillaries speed degenerative process of retina. Most age related pathologies are initiated by metabolic disruptions and AMD shares features of systemic atherosclerosis. An aberrant tissue response to free radical stress, vasculopathy and local ischaemic underlies AMD pathogenesis.There is no specific treatment modality and prudent strategy in prophylaxis only. Early diagnosis and proper control of environmental and lifestyle factors are strived by newer biomedical understanding, which is briefly reviewed

Multiscale Mode Dynamics of a Tethered Membrane

Stochastic dynamics of a tethered membrane with a bond-fluctuating coarse-grained Monte Carlo simulation shows, in addition to diffusion, nondiffusive behavior sensitive to the type of membrane, its size, and quality of the solvent. Motion of the membrane’s center node is described by the variation of the mean-square displacement (R2n) with time step (t), i.e., R2n∝t2ν with the exponent ν≃1/8−1∕6 in the short time followed by subdiffusive power laws (i.e., ν∼1∕5, 1∕10) in the intermediate time regimes before reaching diffusion ν=1. The crossover between in-plane wrinkle modes is identified from the segmental (node) motion of the membrane

Globular Structure of a Human Immunodeficiency Virus-1 Protease (1DIFA dimer) in an Effective Solvent Medium by a Monte Carlo Simulation

A coarse-grained model is used to study the structure and dynamics of a human immunodeficiency virus-1 protease (1DIFA dimer) consisting of 198 residues in an effective solvent medium on a cubic lattice by Monte Carlo simulations for a range of interaction strengths. Energy and mobility profiles of residues are found to depend on the interaction strength and exhibit remarkable segmental symmetries in two monomers. Lowest energy residues such as Arg(41) and Arg(140) (most electrostatic and polar) are not the least mobile; despite the higher energy, the hydrophobic residues (Ile, Leu, and Val) are least mobile and form the core by pinning down the local segments for the globular structure. Variations in the gyration radius (R(g)) and energy (E(c)) of the protein show nonmonotonic dependence on the interaction strength with the smallest R(g) around the largest value of E(c). Pinning of the conformations by the hydrophobic residues at high interaction strength seems to provide seed for the protein chain to collapse

Conformational Response to Solvent Interaction and Temperature of a Protein (Histone h3.1) by a Multi-Grained Monte Carlo Simulation

Interaction with the solvent plays a critical role in modulating the structure and dynamics of a protein. Because of the heterogeneity of the interaction strength, it is difficult to identify multi-scale structural response. Using a coarse-grained Monte Carlo approach, we study the structure and dynamics of a protein (H3.1) in effective solvent media. The structural response is examined as a function of the solvent-residue interaction strength (based on hydropathy index) in a range of temperatures (spanning low to high) involving a knowledge-based (Miyazawa-Jernigan(MJ)) residue-residue interaction. The protein relaxes rapidly from an initial random configuration into a quasi-static structure at low temperatures while it continues to diffuse at high temperatures with fluctuating conformation. The radius of gyration (Rg) of the protein responds non-monotonically to solvent interaction, i.e., on increasing the residue-solvent interaction strength (fs), the increase in Rg (fs≤fsc) is followed by decay (fs≥fsc) with a maximum at a characteristic value (fsc) of the interaction. Raising the temperature leads to wider spread of the distribution of the radius of gyration with higher magnitude of fsc. The effect of solvent on the multi-scale (λ: residue to Rg) structures of the protein is examined by analyzing the structure factor (S(q),|q| = 2π/λ is the wave vector of wavelength, λ) in detail. Random-coil to globular transition with temperature of unsolvated protein (H3.1) is dramatically altered by the solvent at low temperature while a systematic change in structure and scale is observed on increasing the temperature. The interaction energy profile of the residues is not sufficient to predict its mobility in the solvent. Fine-grain representation of protein with two-node and three-node residue enhances the structural resolution; results of the fine-grained simulations are consistent with the finding described above of the coarse-grained description with one-node residue

Random Coil to Globular Thermal Response of a Protein (H3.1) with Three Knowledge-Based Coarse-Grained Potentials

The effect of temperature on the conformation of a histone (H3.1) is studied by a coarse-grained Monte Carlo simulation based on three knowledge-based contact potentials (MJ, BT, BFKV). Despite unique energy and mobility profiles of its residues, the histone H3.1 undergoes a systematic (possibly continuous) structural transition from a random coil to a globular conformation on reducing the temperature. The range over which such a systematic response in variation of the radius of gyration (Rg) with the temperature (T) occurs, however, depends on the potential, i.e. ΔTMJ ≈ 0.013–0.020, ΔTBT ≈ 0.018–0.026, and ΔTBFKV ≈ 0.006–0.013 (in reduced unit). Unlike MJ and BT potentials, results from the BFKV potential show an anomaly where the magnitude of Rg decreases on raising the temperature in a range ΔTA ≈ 0.015–0.018 before reaching its steady-state random coil configuration. Scaling of the structure factor, S(q) ∝ q−1/ν, with the wave vector, q = 2π/λ, and the wavelength, λ, reveals a systematic change in the effective dimension (De∼1/ν) of the histone with all potentials (MJ, BT, BFKV): De∼3 in the globular structure with De∼2 for the random coil. Reproducibility of the general yet unique (monotonic) structural transition of the protein H3.1 with the temperature (in contrast to non-monotonic structural response of a similar but different protein H2AX) with three interaction sets shows that the knowledge-based contact potential is viable tool to investigate structural response of proteins. Caution should be exercise with the quantitative comparisons due to differences in transition regimes with these interactions