Strong-field tidal distortions of rotating black holes: Formalism and results for circular, equatorial orbits

Tidal coupling between members of a compact binary system can have an interesting and important influence on that binary's dynamical inspiral. Tidal coupling also distorts the binary's members, changing them (at lowest order) from spheres to ellipsoids. At least in the limit of fluid bodies and Newtonian gravity, there are simple connections between the geometry of the distorted ellipsoid and the impact of tides on the orbit's evolution. In this paper, we develop tools for investigating tidal distortions of rapidly rotating black holes using techniques that are good for strong-field, fast-motion binary orbits. We use black hole perturbation theory, so our results assume extreme mass ratios. We develop tools to compute the distortion to a black hole's curvature for any spin parameter, and for tidal fields arising from any bound orbit, in the frequency domain. We also develop tools to visualize the horizon's distortion for black hole spin $a/M \le \sqrt{3}/2$ (leaving the more complicated $a/M > \sqrt{3}/2$ case to a future analysis). We then study how a Kerr black hole's event horizon is distorted by a small body in a circular, equatorial orbit. We find that the connection between the geometry of tidal distortion and the orbit's evolution is not as simple as in the Newtonian limit.Comment: 37 pages, 8 figures. Accepted for publication to Physical Review D. This version corrects a number of typographical errors found when reviewing the page proof

Systematic Errors in Cosmic Microwave Background Interferometry

Cosmic microwave background (CMB) polarization observations will require superb control of systematic errors in order to achieve their full scientific potential, particularly in the case of attempts to detect the B modes that may provide a window on inflation. Interferometry may be a promising way to achieve these goals. This paper presents a formalism for characterizing the effects of a variety of systematic errors on interferometric CMB polarization observations, with particular emphasis on estimates of the B-mode power spectrum. The most severe errors are those that couple the temperature anisotropy signal to polarization; such errors include cross-talk within detectors, misalignment of polarizers, and cross-polarization. In a B mode experiment, the next most serious category of errors are those that mix E and B modes, such as gain fluctuations, pointing errors, and beam shape errors. The paper also indicates which sources of error may cause circular polarization (e.g., from foregrounds) to contaminate the cosmologically interesting linear polarization channels, and conversely whether monitoring of the circular polarization channels may yield useful information about the errors themselves. For all the sources of error considered, estimates of the level of control that will be required for both E and B mode experiments are provided. Both experiments that interfere linear polarizations and those that interfere circular polarizations are considered. The fact that circular experiments simultaneously measure both linear polarization Stokes parameters in each baseline mitigates some sources of error.Comment: 19 pages, 9 figures, submitted to Phys. Rev.

Self-field effects upon the critical current density of flat superconducting strips

We develop a general theory to account self-consistently for self-field effects upon the average transport critical current density Jc of a flat type-II superconducting strip in the mixed state when the bulk pinning is characterized by a field-dependent depinning critical current density Jp(B), where B is the local magnetic flux density. We first consider the possibility of both bulk and edge-pinning contributions but conclude that bulk pinning dominates over geometrical edge-barrier effects in state-of-the-art YBCO films and prototype second-generation coated conductors. We apply our theory using the Kim model, JpK(B) = JpK(0)/(1+|B|/B0), as an example. We calculate Jc(Ba) as a function of a perpendicular applied magnetic induction Ba and show how Jc(Ba) is related to JpK(B). We find that Jc(Ba) is very nearly equal to JpK(Ba) when Ba > Ba*, where Ba* is the value of Ba that makes the net flux density zero at the strip's edge. However, Jc(Ba) is suppressed relative to JpK(Ba) at low fields when Ba < Ba*, with the largest suppression occurring when Ba*/B0 is of order unity or larger.Comment: 9 pages, 4 figures, minor revisions to add four reference

Mosaicking with cosmic microwave background interferometers

Measurements of cosmic microwave background (CMB) anisotropies by interferometers offer several advantages over single-dish observations. The formalism for analyzing interferometer CMB data is well developed in the flat-sky approximation, valid for small fields of view. As the area of sky is increased to obtain finer spectral resolution, this approximation needs to be relaxed. We extend the formalism for CMB interferometry, including both temperature and polarization, to mosaics of observations covering arbitrarily large areas of the sky, with each individual pointing lying within the flat-sky approximation. We present a method for computing the correlation between visibilities with arbitrary pointing centers and baselines and illustrate the effects of sky curvature on the l-space resolution that can be obtained from a mosaic.Comment: 9 pages; submitted to Ap

Decreased NADPH oxidase expression and antioxidant activity in cachectic skeletal muscle

Background - Cancer cachexia is the progressive loss of skeletal muscle protein that contributes significantly to cancer morbidity and mortality. Evidence of antioxidant attenuation and the presence of oxidised proteins in patients with cancer cachexia indicate a role for oxidative stress. The level of oxidative stress in tissues is determined by an imbalance between reactive oxygen species production and antioxidant activity. This study aimed to investigate the superoxide generating NADPH oxidase (NOX) enzyme and antioxidant enzyme systems in murine adenocarcinoma tumour-bearing cachectic mice. Methods - Superoxide levels, mRNA levels of NOX enzyme subunits and the antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidise (GPx) and catalase was measured in the skeletal muscle of mice with cancer and cancer cachexia. Protein expression levels of NOX enzyme subunits and antioxidant enzyme activity was also measured in the same muscle samples. Results - Superoxide levels increased 1.4-fold in the muscle of mice with cancer cachexia, and this was associated with a decrease in mRNA of NOX enzyme subunits, NOX2, p40phox and p67phox along with the antioxidant enzymes SOD1, SOD2 and GPx. Cancer cachexia was also associated with a 1.3-fold decrease in SOD1 and 2.0-fold decrease in GPx enzyme activity. Conclusion - Despite increased superoxide levels in cachectic skeletal muscle, NOX enzyme subunits, NOX2, p40phox and p67phox, were downregulated along with the expression and activity of the antioxidant enzymes. Therefore, the increased superoxide levels in cachectic skeletal muscle may be attributed to the reduction in the activity of endogenous antioxidant enzymes

Ticarcillin hypersusceptibility in pseudomonas aeruginosa in cystic fibrosis

Background: A subpopulation of Pseudomonas aeruginosa (PsA) exists in cysticfibrosis (CF) patients that&nbsp; is&nbsp; hypersusceptible&nbsp; to&nbsp; ticarcillin,&nbsp; a&nbsp; carboxypenicillin,&nbsp; in&nbsp; vitro (Tichs strain)&nbsp; defined&nbsp; as&nbsp; a minimum inhibitory concentration (MIC) ≤4μg/ml. Methods: In a retrospective cohort study, isolates of PsA from CF (23),&nbsp; non-cystic fibrosis bronchiectasis (NCFB) (17) and control (18) patients were analysed. MICs for each isolate were determined using agar dilution against six antibiotics and interpreted using EUCAST breakpoints. Prevalence of Tichs in&nbsp; each&nbsp; cohort&nbsp; was&nbsp; calculated.&nbsp; A&nbsp; point&nbsp; prevalence&nbsp; survey&nbsp; was&nbsp; conducted&nbsp; in&nbsp; CF&nbsp; to&nbsp; review&nbsp; the&nbsp; patients’ clinical progress following PsA isolation. Results: Prevalence of the Tichs strain in PsA was 48%, 76% and 0% in the CF, NCFB and control cohorts respectively. A statistically significant difference in geometric mean MIC was seen between the Tichs and non-Tichs&nbsp; cohorts in CF for ticarcillin (as expected) and temocillin (p=0.041and p=0.036 respectively). A similar trend was observed in NCFB for ticarcillin (p=0.038) and temocillin (p=0.067), although statistical significance was not reached for the latter.In&nbsp; CF,&nbsp; the&nbsp; Tichs&nbsp; strain&nbsp; demonstrated&nbsp; lower&nbsp; MICs&nbsp; to&nbsp; all antibiotics&nbsp; tested&nbsp; apart&nbsp; from&nbsp; gentamicin compared&nbsp; to&nbsp; their&nbsp; non-Tichs counterparts. Those&nbsp; who&nbsp; had the Tichs strain&nbsp; in&nbsp; CF&nbsp; had&nbsp; fewer&nbsp; antibiotics (13.9&nbsp; days&nbsp; versus&nbsp; 23.5&nbsp; days,&nbsp; Tichs&nbsp; and&nbsp; non-Tichs respectively)&nbsp; although&nbsp; this&nbsp; result&nbsp; was&nbsp; not&nbsp; statistically significant p=0.202. Conclusion: Our&nbsp; data&nbsp; supports&nbsp; the&nbsp; existence&nbsp; of&nbsp; a&nbsp; Tichs strain&nbsp; of&nbsp; PsA&nbsp; in&nbsp; our&nbsp; CF&nbsp; and&nbsp; NCFB&nbsp; patient populations. This strain correlated with reduced MICs to temocillin in CF, to which PsA would normally be resistant, which may be of clinical relevance.</p

Relationship between dietary intake and erythrocyte PUFA in adolescents from a Western Australian cohort

Background: Population-based studies show that the intake of omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFA) are associated with a range of health conditions. Therefore, the reliability of food frequency questionnaires (FFQ) as rapid and easily accessible screening tools for PUFA intake deserve investigation. Objective: We aimed to assess the relationship between erythrocyte fatty acids and fatty acid intake collected using the Commonwealth Scientific and Industrial Research Organisation (CSIRO) food frequency questionnaire in an adolescent cohort. Design: A cross-sectional study using data from 1155 young adolescents participating in the 14-year follow-up of the Raine Study. Bland–Altman plots were used to determine the agreement between dietary intake and erythrocyte levels of each fatty acid. Results: The main dietary source of n-3 long-chain (LC) PUFA was ‘fresh fish’ (53% of total n-3 LC-PUFA). Docosahexaenoic acid (DHA) showed the strongest correlation between erythrocyte and diet assessment (r = 0.274; p \u3c 0.001), whilst linoleic acid (LA) (r = 0.103; p \u3c 0.001) and arachidonic acid (AA) (r = − 0.06; p = 0.042) showed weaker correlations, with limits of agreement relatively narrow. Bland–Altman plots showed a dose-dependent bias between the FFQ fatty acid data and corresponding erythrocyte data. Conclusions: For the major n-3 and n-6 PUFA, dietary intakes derived from the FFQ showed weaker correlations and poorer agreement with erythrocyte levels, and the deviation between the two increased with higher intake levels

Unsettling sustainability: the poetics of discomfort

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