Metallic liquid hydrogen and likely Al2O3 metallic glass

Dynamic compression has been used to synthesize liquid metallic hydrogen at 140 GPa (1.4 million bar) and experimental data and theory predict Al2O3 might be a metallic glass at ~300 GPa. The mechanism of metallization in both cases is probably a Mott-like transition. The strength of sapphire causes shock dissipation to be split differently in the strong solid and soft fluid. Once the 4.5-eV H-H and Al-O bonds are broken at sufficiently high pressures in liquid H2 and in sapphire (single-crystal Al2O3), electrons are delocalized, which leads to formation of energy bands in fluid H and probably in amorphous Al2O3. The high strength of sapphire causes shock dissipation to be absorbed primarily in entropy up to ~400 GPa, which also causes the 300-K isotherm and Hugoniot to be virtually coincident in this pressure range. Above ~400 GPa shock dissipation must go primarily into temperature, which is observed experimentally as a rapid increase in shock pressure above ~400 GPa. The metallization of glassy Al2O3, if verified, is expected to be general in strong oxide insulators. Implications for Super Earths are discussed.Comment: 8 pages, 5 figures, 14th Liquid and Amorphous Metals Conference, Rome 201

Entropy-Dominated Dissipation in Sapphire Shock-Compressed up to 400 GPa (4 Mbar)

Sapphire (single-crystal Al2O3) is a representative Earth material and is used as a window and/or anvil in shock experiments. Pressure, for example, at the core-mantle boundary is about 130 gigapascals (GPa). Defects induced by 100-GPa shock waves cause sapphire to become opaque, which precludes measuring temperature with thermal radiance. We have measured wave profiles of sapphire crystals with several crystallographic orientations at shock pressures of 16, 23, and 86 GPa. At 23 GPa plastic-shock rise times are generally quite long (~100 ns) and their values depend sensitively on the direction of shock propagation in the crystal lattice. The long rise times are probably caused by the high strength of inter-atomic interactions in the ordered three-dimensional sapphire lattice. Our wave profiles and recent theoretical and laser-driven experimental results imply that sapphire disorders without significant shock heating up to about 400 GPa, above which Al2O3 is amorphous and must heat. This picture suggests that the characteristic shape of shock compression curves of many Earth materials at 100 GPa pressures is caused by a combination of entropy and temperature.Comment: 12 pages, 4 figure

Self-perceived psychological stress and ischemic stroke: a case-control study

<p>Abstract</p> <p>Background</p> <p>A growing body of evidence suggests that psychological stress contributes to coronary artery disease. However, associations between stress and stroke are less clear. In this study, we investigated the possible association between ischemic stroke and self-perceived psychological stress, as measured by a single-item questionnaire, previously reported to be associated with myocardial infarction.</p> <p>Methods</p> <p>In the Sahlgrenska Academy Study on Ischemic Stroke (SAHLSIS), 600 consecutive patients with acute ischemic stroke (aged 18 to 69 years) and 600 age-matched and sex-matched population controls were recruited. Ischemic stroke subtype was determined according to Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. Self-perceived psychological stress preceding stroke was assessed retrospectively using a single-item questionnaire.</p> <p>Results</p> <p>Permanent self-perceived psychological stress during the last year or longer was independently associated with overall ischemic stroke (multivariate adjusted odds ratio (OR) 3.49, 95% confidence interval (CI) 2.06 to 5.93). Analyses by stroke subtype showed that this association was present for large vessel disease (OR 3.91, 95% CI 1.58 to 9.67), small vessel disease (OR 3.20, 95% CI 1.64 to 6.24), and cryptogenic stroke (OR 4.03, 95% CI 2.34 to 6.95), but not for cardioembolic stroke (OR 1.48, 95% CI 0.64 to 3.39).</p> <p>Conclusion</p> <p>In this case-control study, we found an independent association between self-perceived psychological stress and ischemic stroke. A novel finding was that this association differed by ischemic stroke subtype. Our results emphasize the need for further prospective studies addressing the potential role for psychological stress as a risk factor for ischemic stroke. In such studies ischemic stroke subtypes should be taken into consideration.</p

Coastal groundwater discharge – an additional source of phosphorus for the oligotrophic wetlands of the Everglades

In this manuscript we define a new term we call coastal groundwater discharge (CGD), which is related to submarine groundwater discharge (SGD), but occurs when seawater intrudes inland to force brackish groundwater to discharge to the coastal wetlands. A hydrologic and geochemical investigation of both the groundwater and surface water in the southern Everglades was conducted to investigate the occurrence of CGD associated with seawater intrusion. During the wet season, the surface water chemistry remained fresh. Enhanced chloride, sodium, and calcium concentrations, indicative of brackish groundwater discharge, were observed in the surface water during the dry season. Brackish groundwaters of the southern Everglades contain 1–2.3μM concentrations of total phosphorus (TP). These concentrations exceed the expected values predicted by conservative mixing of local fresh groundwater and intruding seawater, which both have TPμM. The additional source of TP may be from seawater sediments or from the aquifer matrix as a result of water–rock interactions (such as carbonate mineral dissolution and ion exchange reactions) induced by mixing fresh groundwater with intruding seawater. We hypothesize that CGD maybe an additional source of phosphorus (a limiting nutrient) to the coastal wetlands of the southern Everglades

Posttraumatic Stress Disorder Prevalence and Risk of Recurrence in Acute Coronary Syndrome Patients: A Meta-analytic Review

BACKGROUND:Acute coronary syndromes (ACS; myocardial infarction or unstable angina) can induce posttraumatic stress disorder (PTSD), and ACS-induced PTSD may increase patients' risk for subsequent cardiac events and mortality. OBJECTIVE:To determine the prevalence of PTSD induced by ACS and to quantify the association between ACS-induced PTSD and adverse clinical outcomes using systematic review and meta-analysis. DATA SOURCES:Articles were identified by searching Ovid MEDLINE, PsycINFO, and Scopus, and through manual search of reference lists. METHODOLOGY/PRINCIPAL FINDINGS:Observational cohort studies that assessed PTSD with specific reference to an ACS event at least 1 month prior. We extracted estimates of the prevalence of ACS-induced PTSD and associations with clinical outcomes, as well as study characteristics. We identified 56 potentially relevant articles, 24 of which met our criteria (N = 2383). Meta-analysis yielded an aggregated prevalence estimate of 12% (95% confidence interval [CI], 9%-16%) for clinically significant symptoms of ACS-induced PTSD in a random effects model. Individual study prevalence estimates varied widely (0%-32%), with significant heterogeneity in estimates explained by the use of a screening instrument (prevalence estimate was 16% [95% CI, 13%-20%] in 16 studies) vs a clinical diagnostic interview (prevalence estimate was 4% [95% CI, 3%-5%] in 8 studies). The aggregated point estimate for the magnitude of the relationship between ACS-induced PTSD and clinical outcomes (ie, mortality and/or ACS recurrence) across the 3 studies that met our criteria (N = 609) suggested a doubling of risk (risk ratio, 2.00; 95% CI, 1.69-2.37) in ACS patients with clinically significant PTSD symptoms relative to patients without PTSD symptoms. CONCLUSIONS/SIGNIFICANCE:This meta-analysis suggests that clinically significant PTSD symptoms induced by ACS are moderately prevalent and are associated with increased risk for recurrent cardiac events and mortality. Further tests of the association of ACS-induced PTSD and clinical outcomes are needed

Sleep-disordered breathing-do we have to change gears in heart failure?

The majority of patients with heart failure have sleep-disordered breathing (SDB)-with central (rather than obstructive) sleep apnoea becoming the predominant form in those with more severe disease. Cyclical apnoeas and hypopnoeas are associated with sleep disturbance, hypoxaemia, haemodynamic changes, and sympathetic activation. Such patients have a worse prognosis than those without SDB. Mask-based therapies of positive airway pressure targeted at SDB can improve measures of sleep quality and partially normalise the sleep and respiratory physiology, but recent randomised trials of cardiovascular outcomes in central sleep apnoea have been neutral or suggested the possibility of harm, likely from increased sudden death. Further randomised outcome studies (with cardiovascular mortality and hospitalisation endpoints) are required to determine whether mask-based treatment for SDB is appropriate for patients with chronic systolic heart failure and obstructive sleep apnoea, for those with heart failure with preserved ejection fraction, and for those with decompensated heart failure. New therapies for sleep apnoea-such as implantable phrenic nerve stimulators-also require robust assessment. No longer can the surrogate endpoints of improvement in respiratory and sleep metrics be taken as adequate therapeutic outcome measures in patients with heart failure and sleep apnoea

Stress, ageing and their influence on functional, cellular and molecular aspects of the immune system

The immune response is essential for keeping an organism healthy and for defending it from different types of pathogens. It is a complex system that consists of a large number of components performing different functions. The adequate and controlled interaction between these components is necessary for a robust and strong immune response. There are, however, many factors that interfere with the way the immune response functions. Stress and ageing now consistently appear in the literature as factors that act upon the immune system in the way that is often damaging. This review focuses on the role of stress and ageing in altering the robustness of the immune response first separately, and then simultaneously, discussing the effects that emerge from their interplay. The special focus is on the psychological stress and the impact that it has at different levels, from the whole system to the individual molecules, resulting in consequences for physical health