Interacting Cosmological Fluids and the Coincidence Problem

We examine the evolution of a universe comprising two interacting fluids, which interact via a term proportional to the product of their densities. In the case of two matter fluids it is shown that the ratio of the densities tends to a constant after an initial cooling-off period. We then obtain a complete solution for the cosmological constant (w = -1) scenario. Finally, we investigate the general case in which the dark energy equation of state is p = w*rho, where w is a constant, and show that periodic solutions can occur if w < -1. We further demonstrate that the ratio of the dark matter to dark energy densities is confined to a bounded interval, and that this ratio can be O(1) at infinitely many times in the history of the universe, thus solving the coincidence problem.Comment: 20 pages, 8 figures. Added two new sections (VI and VII) constraining the parameters and examining the evolution of the periodic solution in more detail. Submitted to Phys. Rev.

Major Outcomes in Atrial Fibrillation Patients with One Risk Factor: Impact of Time in Therapeutic Range

BACKGROUND: The benefits and harms of oral anticoagulation (OAC) therapy in patients with only one stroke risk factor (i.e. CHA2DS2-VASc= 1 in males, or 2 in females) has been subject of debate. METHODS: We analysed all patients with only one stroke risk factor from the merged datasets of SPORTIF III and V trials. Anticoagulation control was defined according to time in therapeutic range (TTR). RESULTS: Of the original trial cohort, 1,097 patients had only one stroke risk factor. Stroke/systemic thromboembolic event had an incidence of 0.9 per 100 patient-years, with an incidence of 1.6 per 100 patient-years for all-cause death and 2.3%/patient-years for the composite outcome of stroke/systemic thromboembolic event/all-cause death. There were no significant differences in the risk for stroke/systemic thromboembolic event between sexes, nor between the different stroke risk factors amongst these atrial fibrillation patients with only one stroke risk factor. Cox regression analysis in patients treated with warfarin only found TTR to be inversely associated with stroke/systemic thromboembolic event (p=0.034) and all-cause death (p=0.015). Chronic heart failure was significantly associated with the outcome of all-cause death (p=0.0019) and the composite outcome of stroke/systemic thromboembolic event/all-cause death (p=0.021). There was a significant inverse linear association between TTR and the cumulative risk for both stroke/systemic thromboembolic event and all-cause death (both p<0.001). CONCLUSIONS: In atrial fibrillation patients with only one additional stroke risk factor (i.e. CHA2DS2-VASc= 1 in males or 2 in females), rates of major adverse events (stroke/systemic thromboembolic event, mortality) were high, despite anticoagulation. TTR in warfarin-treated patients was inversely associated with the occurrence of both stroke/systemic thromboembolic event and all-cause death

Does measurement technique explain the mismatch between European head size and WHO charts?

Objective To test whether different measuring techniques produce systematic differences in head size that could explain the large head circumferences found in Northern European children compared with the WHO standard. Design: Cross-sectional observational study. Setting: Scotland, UK. Patients: Study 1: 68 healthy children aged 0.4–18 months from mother and baby groups and a medical students teaching session. Study 2: 81 children aged 0.4 to 25 months from hospital wards and neonatal follow-up clinics. Interventions: Study 1: heads measured with plastic tape using both the WHO tight and UK loose technique. Study 2: heads measured using WHO research technique and a metal measuring tape and compared with routinely acquired measurements. Main outcome measures: Mean difference in head z-scores using WHO standard between the two methods. Results: The tight technique resulted in a mean (95% CI) z-score difference of 0.41 (0.27 to 0.54, p&lt;0.001) in study 1 and 0.44 (0.36 to 0.53, p&lt;0.001) in study 2. However, the mean WHO measurements in the healthy infants still produced a mean z-score that was two-third of a centile space (0.54 SD (0.28 to 0.79) p&lt;0.001) above the 50th centile. Conclusion: The WHO measurement techniques produced significantly lower measures of head size, but average healthy Scottish children still had larger heads than the WHO standard using this method

The year in cardiology: arrhythmias and pacing.

During this last year, there has been much progress with regard to anticoagulant and ablation therapy for atrial fibrillation (AF). Apart from recently issued European Society of Cardiology Guidelines for the management of patients with supraventricular arrhythmias, there has been little progress in research in this field. Ventricular arrhythmias and device therapy have seen modest progress

Squeeze flow and compaction behavior of toughened polyimide matrix composites

The main emphasis was placed upon the squeeze flow and compaction behavior of the Lewis Research Center (LaRC) research project series polyimide matrix composites. The measurement of squeeze film flow behavior was performed by a plastometer which monitors the change of thickness of a prepreg specimen laid between two parallel plates under the specified temperature and pressure history. A critical evaluation of the plastometer data was attempted by examining the morphology of the specimen at various points during the squeeze flow. The effects of crosslinks (Mc) of resin, imidization (B-ataging) condition, and pressure on the squeeze flow behavior were examined. Results are given

Desiccation and Preculture Effects on Survival of Encapsulated Zygotic Embryos of Rubber (Hevea Brasiliensis Muel.-Arg) Following Liquid Nitrogen Exposure

The effects of desiccation, sucrose as cryoprotectant and abscisic acid (ABA) as chemical ameliorant on the cryopreservation of Hevea zygotic embryos were evaluated using the alginate encapsulation method. The first part of the study was on the effects of desiccation on the survival of alginate-encapsulated Hevea zygotic embryos following liquid nitrogen exposure. The embryos need to be desiccated to at least 26% moisture content to enable some survival after exposure to liquid nitrogen. Embryos desiccated to moisture content of 14% and 18% gave comparatively higher survival after cryopreservation (42.5% and 47.5% respectively). Encapsulation of the embryos enhanced desiccation tolerance and desiccation was allowed even until 10% moisture content with some survival even though Hevea seeds are known to be recalcitrant. Encapsulation had broaden the window for cryopreservation by allowing the embryos to survive desiccation and cryopreservation at a broader range of moisture content compared to naked embryos done in previous work. However, a very low percentage of embryos developed into normal plantlets. The importance of sucrose preculture for cryopreservation of encapsulated Hevea embryos is also proven in this study. Sucrose preculture at low concentration of 0.3 M improved viability and survival before and after cryopreservation significantly to 70% and 60% respectively. Desiccation and freezing resistance were further enhanced when the encapsulated embryos were precultured on 0 . 5 M sucrose with viability as high as 82% (after cryopreservation). However, after twelve weeks culture, the percentage of survival after cryopreservation was maintained as when precultured on 0.3 M sucrose, with 1 4% and 1 6% moisture levels showing better results (51% and 59% respectively). Preculture with 0.5 M sucrose improved perculture of embryos developed into normal plantlet (as high as 35% and 32% survival before and after cryopreservation). As the concentration of sucrose preculture was increased further to 0.7 M and 0.9 M, the freezing tolerance of the embryos reduced considerably. A very low percentage of normal plantlet was obtained after cryopreservation (3 to 9%). Desiccation tolerance was also slightly reduced as indicated by lower survival before cryopreservation

Short runs of atrial arrhythmia and stroke risk: a European-wide online survey among stroke physicians and cardiologists

Methods: An online survey of cardiologists and stroke physicians was carried out to assess current management of patients with short runs of atrial arrhythmia within Europe. Results: Respondents included 311 clinicians from 32 countries. To diagnose atrial fibrillation, 80% accepted a single 12-lead ECG and 36% accepted a single run of &lt; 30 seconds on ambulatory monitoring. Stroke physicians were twice as likely to accept &lt; 30 seconds of arrhythmia as being diagnostic of atrial fibrillation (OR 2.43, 95% CI 1.19–4.98). They were also more likely to advocate anticoagulation for hypothetical patients with lower risk; OR 1.9 (95% CI 1.0–3.5) for a patient with CHA2DS2-VASc = 2. Conclusion: Short runs of atrial fibrillation create a dilemma for physicians across Europe. Stroke physicians and cardiologists differ in their diagnosis and management of these patients

Oil Palm Ash As Solid Catalyst For Palm Oil-based Transesterification To Biodiesel: Optimization By Response Surface Methodology

Biodiesel adalah satu bahan api alternatif untuk enjin diesel yang semakin mendapat perhatian dari segi kesusutan sumber bahan api fosil seluruh duni

Sifat Morfologi Buluh, Dendrocalamus Asper (Schultes F.) Backer Ex Heyne dan Perkaitannya dengan Faktor Edafik Terpilih di Bahagian Sri Aman, Sarawak

Sifat morfologi buluh, Dendrocalamus asper (Schultes f.) Backer ex Heyne dan perkaitannya dengan faktor edafik terpilih telah dikajikan di lima kawasan di bahagian Sri Aman, Sarawak. 96 plot telah disetkan di kawasan kajian berkenaan. Kedua-dua ciri-ciri fizikal dan kimia edafik termasuk pH, kandungan nitrogen, jumlah fosforus, kalsium tertukarkan, magnesium tertukarkan, kalium tertukarkan, natrium tertukarkan, kelembapan, kandungan bahan organik, ketumpatan pukal dan tekstur telah ditentukan melalui analisis makmal. Keputusan menunjukkan bahawa tekstur tanah adalah pasir-Ioam, min bagi pH, kandungan nitrogen, jumlah fosforus, kalsium tertukarkan, magnesium tertukarkan, kalium tertukarkan, natrium tertukarkan, kelembapan, kandungan bahan organik, ketumpatan pukal masing-masing adalah 5.20±0.05, 0.23±0.01%, 269.50±17.00 mgr¹, 1.43±0.18 cmol/kg, 0.91±0.06 cmol/kg, 0.30±0.01 cmol/kg, 0.10±0.02 cmol/kg, 14.26±0.61%, 9.51±0.42% dan 1.00±0.03 gcm⁻³

A Generalized Theory of Varying Alpha

In this paper, we formulate a generalization of the simple Bekenstein-Sandvik-Barrow-Magueijo (BSBM) theory of varying alpha by allowing the coupling constant, \omega, for the corresponding scalar field \psi\ to depend on \psi. We focus on the situation where \omega\ is exponential in \psi\ and find the late-time behaviours that occur in matter-dominated and dark-energy dominated cosmologies. We also consider the situation when the background expansion scale factor of the universe evolves in proportion to an arbitrary power of the cosmic time. We find the conditions under which the fine structure `constant' increases with time, as in the BSBM theory, and establish a cosmic no-hair behaviour for accelerating universes. We also find the conditions under which the fine structure `constant' can decrease with time and compare the whole family of models with astronomical data from quasar absorption spectra.Comment: 25 pages, 6 figures. Minor corrections and clarifications added. Final section on spatial variations removed so that the paper focuses exclusively on time-variatio