Hydrocarbon ions in the lower ionosphere of Saturn

[1] Radio occultation measurements of the Saturn ionosphere have shown that persistent but variable electron density layers appear well below the major peaks. We model here the region of hydrocarbon ions that is below the main peak and is produced by absorption of solar photons in the wavelength range 842 to 1116 Å, which penetrate to altitudes below the methane homopause in the wings of the H2 absorption lines, and in the gaps between groups of lines. In this wavelength range, H2 absorbs photons in discrete transitions to rovibrational levels of electronically excited states, which then decay to a range of rovibrational levels of the electronic ground state, or to the continuum of the ground state. The cross sections for these discrete absorptions vary by several orders of magnitude from the peaks to the wings of the absorption lines. We find that the adoption of high resolution photoabsorption cross sections for the H2 bands leads to different photoionization profiles for both the hydrocarbons and H atoms, and to peak inline imagephotoproduction profiles that are more than an order of magnitude larger than those computed with low resolution cross sections. For the present model, we find that ionization by energetic electrons that accompany the absorption of soft X-rays appears in the same altitude range. We predict that a broad region of hydrocarbon ions appears well below the main peak, in the altitude range 600 to 1000 km above the 1 bar level (2–0.04 μbar) with a maximum electron density of ∼3×103cm−3 at low solar activity

An Observational Determination of the Proton to Electron Mass Ratio in the Early Universe

In an effort to resolve the discrepancy between two measurements of the fundamental constant mu, the proton to electron mass ratio, at early times in the universe we reanalyze the same data used in the earlier studies. Our analysis of the molecular hydrogen absorption lines in archival VLT/UVES spectra of the damped Lyman alpha systems in the QSOs Q0347-383 and Q0405-443 yields a combined measurement of a (Delta mu)/mu value of (-7 +/- 8) x 10^{-6}, consistent with no change in the value of mu over a time span of 11.5 gigayears. Here we define (Delta mu) as (mu_z - mu_0) where mu_z is the value of mu at a redshift of z and mu_0 is the present day value. Our null result is consistent with the recent measurements of King et al. 2009, (Delta mu)/u = (2.6 +/- 3.0) x 10^{-6}, and inconsistent with the positive detection of a change in mu by Reinhold et al. 2006. Both of the previous studies and this study are based on the same data but with differing analysis methods. Improvements in the wavelength calibration over the UVES pipeline calibration is a key element in both of the null results. This leads to the conclusion that the fundamental constant mu is unchanged to an accuracy of 10^{-5} over the last 80% of the age of the universe, well into the matter dominated epoch. This limit provides constraints on models of dark energy that invoke rolling scalar fields and also limits the parameter space of Super Symmetric or string theory models of physics. New instruments, both planned and under construction, will provide opportunities to greatly improve the accuracy of these measurements.Comment: Accepted for publication in the Astrophysical Journa

Tuberculosis burden in stage 5 chronic kidney disease patients undergoing dialysis therapy at Livingstone Hospital, Port Elizabeth, South Africa

Background. Tuberculosis (TB) is currently the leading cause of death from a single infectious agent worldwide. Patients who receive dialysis are particularly vulnerable to TB infection owing to immune dysfunction. Nonetheless, there is a paucity of incidence data on dialysis patients infected with TB in high-burden countries, such as South Africa (SA).Objectives. To determine the incidence of TB in prevalent chronic kidney disease stage 5 (CKD-5D) patients on dialysis at a single centre in Eastern Cape Province, SA, and to identify the risk factors associated with TB infection.Methods. We conducted a retrospective cohort study of all consenting CKD-5D patients between April 2010 and March 2014 at Livingstone Hospital Renal Unit, Port Elizabeth, the Eastern Cape. TB was defined as definite or probable according to World Health Organization (WHO) criteria, and the cohort was split into those who developed TB (TB+) and those who did not (TB−).Results. One hundred and eleven patients were enrolled – predominantly black Africans (73%) and women (53%); the mean age (standard deviation (SD)) was 42 (9.8) years. The prevalence of HIV infection was 11%, all patients were receiving antiretroviral treatment and all had suppressed viral loads. Sixty-eight patients were on haemodialysis and 43 on peritoneal dialysis. Nineteen patients were diagnosed with 20 episodes of TB; 14 cases were pulmonary TB and 6 cases extrapulmonary TB. Of the patients with TB, 2 were HIV-infected, 7 (35%) were definite TB cases and 13 (65%) were probable cases. The calculated incidence rate was 4 505/100 000 patient years. Only informal housing (30% in TB+ v. 12% in TB−; p=0.042) and a history of hospitalisation (90% v. 76%, respectively; p=0.042) were significantly associated with a diagnosis of TB.Conclusions. Dialysis patients in the Eastern Cape region of SA are at extremely high risk of acquiring TB, with an incidence rate 4.1 times that of the local population and >5 times that of the general SA population. Only informal housing and a history of hospitalisation were identified as positive risk factors for TB in this young population with a low HIV prevalence. Isoniazid prophylaxis in this high-risk group might be of benefit, but further studies are required to inform such treatment

Solar energy for self-contained power supply

Solar energy relevance in self-contained utility system as well as economic feasibility for each class of consumers considered. The article will outline utilising features of self-contained photovoltaic stations in Middle East and Northern Africa

Effect of Time Reversal Symmetry Breaking on the Density of States in Small Superconducting Grains

We show that in ultra-small superconducting grains any concentration of magnetic impurities or infinitely small orbital effect of magnetic field leads to destruction of the hard gap in the tunneling density of states. Instead, though exponentially suppressed at low energies, the tunneling density of states exhibits the ``soft gap'' behavior, vanishing linearly with excitation energy, as the energy approaches zero.Comment: 4 pages, 1 eps figur

Precession of a Freely Rotating Rigid Body. Inelastic Relaxation in the Vicinity of Poles

When a solid body is freely rotating at an angular velocity ${\bf \Omega}$, the ellipsoid of constant angular momentum, in the space $\Omega_1, \Omega_2, \Omega_3$, has poles corresponding to spinning about the minimal-inertia and maximal-inertia axes. The first pole may be considered stable if we neglect the inner dissipation, but becomes unstable if the dissipation is taken into account. This happens because the bodies dissipate energy when they rotate about any axis different from principal. In the case of an oblate symmetrical body, the angular velocity describes a circular cone about the vector of (conserved) angular momentum. In the course of relaxation, the angle of this cone decreases, so that both the angular velocity and the maximal-inertia axis of the body align along the angular momentum. The generic case of an asymmetric body is far more involved. Even the symmetrical prolate body exhibits a sophisticated behaviour, because an infinitesimally small deviation of the body's shape from a rotational symmetry (i.e., a small difference between the largest and second largest moments of inertia) yields libration: the precession trajectory is not a circle but an ellipse. In this article we show that often the most effective internal dissipation takes place at twice the frequency of the body's precession. Applications to precessing asteroids, cosmic-dust alignment, and rotating satellites are discussed.Comment: 47 pages, 1 figur

Comparison of Postural Recovery Following Short and Long Duration Spaceflights

INTRODUCTION: Post-flight postural ataxia reflects adaptive changes to vestibulo-spinal reflexes and control strategies adopted for movement in weightlessness. Quantitative measures obtained during computerized dynamic posturography (CDP) from US and Russian programs provide insight into the effect of spaceflight duration in terms of both the initial decrements and recovery of postural stability. METHODS: CDP was obtained on 117 crewmembers following Shuttle flights lasting 4-17 days, and on 64 crewmembers following long-duration missions lasting 48-380 days. Although the number and timing of sessions varied, the goal was to characterize postural recovery pooling similar measures from different research and flight medicine programs. This report focuses on eyes closed, head erect conditions with either a fixed or sway-referenced base of support. A smaller subset of subjects repeated the sway-referenced condition while making pitch head movements (+/- 20deg at 0.33Hz). Equilibrium scores were derived from peak-to-peak anterior-posterior sway. Fall probability was modeled using Bayesian statistical methods to estimate parameters of a logit function. RESULTS: The standard Romberg condition was the least sensitive. Longer duration flights led to larger decrements in stability with sway-reference support during the first 1-2 days, although the timecourse of recovery was similar across flight duration with head erect. Head movements led to increased incidence of falls during the first week, with a significantly longer recovery following long duration flights. CONCLUSIONS: The diagnostic assessment of postural instability, and differences in the timecourse of postural recovery between short and long flight durations, are more pronounced during unstable support conditions requiring active head movements

The Observations Of The X-Ray Source Hz Herculis-Hercules X-1

NASAESASRCAstronom

Transport properties and point contact spectra of Ni_xNb_{1-x} metallic glasses

Bulk resistivity and point contact spectra of Ni_xNb_{1-x} metallic glasses have been investigated as functions of temperature (0.3-300K) and magnetic field (0-12T). Metallic glasses in this family undergo a superconducting phase transition determined by the Nb concentration. When superconductivity was suppressed by a strong magnetic field, both the bulk sample R(T) and the point contact differential resistance curves of Ni_xNb_{1-x} showed logarithmic behavior at low energies, which is explained by a strong electron - "two level system" coupling. We studied the temperature, magnetic field and contact resistance dependence of Ni_{44}Nb_{56} point-contact spectra in the superconducting state and found telegraph-like fluctuations superimposed on superconducting characteristics. These R(V) characteristics are extremely sensitive detectors for slow relaxing "two level system" motion.Comment: 4 pages, 5 figure