Observation of a Griffiths-like phase in the paramagnetic regime of ErCo_2

A systematic x-ray magnetic circular dichroism study of the paramagnetic phase of ErCo2 has recently allowed to identify the inversion of the net magnetization of the Co net moment with respect to the applied field well above the ferrimagnetic ordering temperature, Tc. The study of small angle neutron scattering measurements has also shown the presence of short range order correlations in the same temperature region. This phenomenon, which we have denoted parimagnetism, may be related with the onset of a Griffiths-like phase in paramagnetic ErCo2. We have measured ac susceptibility on ErCo2 as a function of temperature, applied field, and excitation frequency. Several characteristics shared by systems showing a Griffiths phase are present in ErCo2, namely the formation of ferromagnetic clusters in the disordered phase, the loss of analyticity of the magnetic susceptibility and its extreme sensitivity to an applied magnetic field. The paramagnetic susceptibility allows to establish that the magnetic clusters are only formed by Co moments as well as the intrinsic nature of those Co moments

Role of environmental factors for the vertical distribution (0–1000 m) of marine bacterial communities in the NW Mediterranean Sea

Bacterioplankton plays a central role in energy and matter fluxes in the sea, yet the factors that constrain its variation in marine systems are still poorly understood. Here we use the explanatory power of direct multivariate gradient analysis to evaluate the driving forces exerted by environmental parameters on bacterial community distribution in the water column. We gathered and analysed data from a one month sampling period from the surface to 1000 m depth at the JGOFS-DYFAMED station (NW Mediterranean Sea). This station is characterized by very poor horizontal advection currents which makes it an ideal model to test hypotheses on the causes of vertical stratification of bacterial communities. Capillary electrophoresis single strand conformation polymorphism (CE-SSCP) fingerprinting profiles analyzed using multivariate statistical methods demonstrated a vertical zonation of bacterial assemblages in three layers, above, in or just below the chlorophyll maximum and deeper, that remained stable during the entire sampling period. Through the use of direct gradient multivariate ordination analyses we demonstrate that a complex array of biogeochemical parameters is the driving force behind bacterial community structure shifts in the water column. Physico-chemical parameters such as phosphate, nitrate, salinity and to a lesser extent temperature, oxygen, dissolved organic carbon and photosynthetically active radiation acted in synergy to explain bacterial assemblages changes with depth. Analysis of lipid biomarkers of organic matter sources and fates suggested that bacterial community structure in the surface layers was in part explained by lipids of chloroplast origin. Further detailed analysis of pigment-based phytoplankton diversity gave evidence of a compartmentalized influence of several phytoplankton groups on bacterial community structure in the first 150 m depth

Prospects for studying the solar CNO cycle by means of a lithium neutrino detector

Lithium detectors have a high sensitivity to CNO neutrinos from the Sun. The present experimental data and prospects for future experiments on the detection of CNO neutrinos are discussed. A nonstationary case is considered when the flux of 13N neutrinos is higher than the standard solar model predicts due to the influx of fresh material from the peripheral layers to the solar core.Comment: 12 pages, 5 figures, a thoroughly revised version, reported at International Symposium "Physics of Massive Neutrinos" at MILOS (Greece) 19-23 May 200

Fluctuations and Dissipation of Coherent Magnetization

A quantum mechanical model is used to derive a generalized Landau-Lifshitz equation for a magnetic moment, including fluctuations and dissipation. The model reproduces the Gilbert-Brown form of the equation in the classical limit. The magnetic moment is linearly coupled to a reservoir of bosonic degrees of freedom. Use of generalized coherent states makes the semiclassical limit more transparent within a path-integral formulation. A general fluctuation-dissipation theorem is derived. The magnitude of the magnetic moment also fluctuates beyond the Gaussian approximation. We discuss how the approximate stochastic description of the thermal field follows from our result. As an example, we go beyond the linear-response method and show how the thermal fluctuations become anisotropy-dependent even in the uniaxial case.Comment: 22 page

Evidencias de actividad glaciar durante el Dryas reciente (12, 9-11, 7 ka BP) en la Península Ibérica

El Dryas Reciente (Younger Dryas) (GS-1, entre 12, 9 y 11, 7 ka BP) se caracterizó por un marcado descenso de la temperatura a escala global. La consecuencia fue un re avance de los glaciares que afectó también a las cordilleras más importantes de la Península Ibérica. Este trabajo revisa la información disponible sobre la localización, evolución y extensión de tales glaciares. La actividad geomorfológica durante el Dryas Reciente en la Península Ibérica se ha identificado mediante depósitos morrénicos, umbrales rocosos pulidos por el hielo, y glaciares rocosos, datados en la mayor parte de los casos mediante métodos cosmogénicos. Los mejores ejemplos de morrenas del Dryas Reciente se localizan en los Pirineos, donde se desarrollaron cortas lenguas glaciares de hasta 4 km de longitud en los macizos más elevados y numerosos glaciares de circo. También hay evidencias de pequeños glaciares de circo y glaciares rocosos en la Cordillera Cantábrica y en el Sistema Central (sierras de Gredos y Guadarrama), como indican umbrales rocosos y depósitos morrénicos en el frente de circos glaciares. En cambio, en Sierra Nevada, en el extremo meridional de la Península Ibérica, las únicas evidencias del Younger Dryas son glaciares rocosos que se desarrollaron durante el Dryas Antiguo y estuvieron funcionales durante todo el Dryas reciente. The Younger Dryas (GS-1, entre 12, 9 y 11, 7 ka BP) was characterized by a remarkable declining in temperature at a global scale. The consequence was a moderate re-advance of glaciers that also affected the main ranges of the Iberian Peninsula. This paper reviews the available information on the location, evolution and extent of such glaciers. The geomorphological activity during the Younger Dryas in the Iberian Peninsula has been identified throughout the presence of morainic deposits (dated in most cases with cosmogenic exposure ages), rocky thresholds polished by the ice, and rock glaciers. The best examples of Younger Dryas moraines were found in the Central Pyrenees, with short ice tongues of up to 4 km in length in the highest massifs and a number of glacial cirques. There is also evidence of small cirque glaciers in the Cantabrian Range and the Central System Range (Gredos and Guadarrama sierras), as deduced by rocky thresholds and morainic deposits close to cirque headwalls. Conversely, in Sierra Nevada (southernmost sector of the Iberian Peninsula) the only evidence of the Younger Dryas is the presence of rock glaciers that were developed during the Oldest Dryas and survived during the Younger Dryas

Influence of Polymorphisms Involved in Platelet Activation and Inflammatory Response on Aspirin-Related Upper Gastrointestinal Bleeding: A Case-Control Study

Background: Despite the wide benefits of aspirin and its cost-effectiveness, aspirin prescriptions have been reduced due to idiosyncratic responses in susceptible individuals. Low-dose aspirin and single-nucleotide polymorphisms (SNPs) are independently associated with increased risk of gastrointestinal hemorrhage; however, to-date, no studies investigated the SNP-aspirin interaction effect on upper gastrointestinal hemorrhage (UGIH). Therefore, we aimed to evaluate the role of 25 SNPs in multiple genes involved in platelet activation, angiogenesis and inflammatory response in aspirin-related UGIH. Methods: A multicenter, full case-control study was conducted in patients exposed and unexposed to aspirin. Three hundred twenty-six cases diagnosed with UGIH were matched with 748 controls (1:3) by age, gender, health center, and recruitment date. Only adults of European origin were included. Participants were stratified by aspirin exposure and genotype [(Aspirin(-), wild-type), (Aspirin(+), wild-type), (Aspirin(+), genetic variation), (Aspirin(-), genetic variation)]. For each SNP, the Odds Ratio of UGIH and their 95% confidence intervals were estimated in each subgroup by using the generalized linear mixed models for dependent binomial variables. SNP-aspirin interaction effect was estimated through Relative Excess Risk due to Interaction (RERI) measures. Results: We observed two categories of SNPs that might modify the risk magnitude of UGIH in aspirin consumers. Seven SNPs (rs1387180 A > G, rs2238631 T > C, rs1799964 T > C, rs5050 T > C/T > G, rs689466 T > C, rs1799983 T > A/T > G, and rs7756935 C > A) were "positive modifiers" associated with an excess of risk from aspirin exposure and carrying that genetic variation (1.75 T, rs1131882 G > A, rs4311994 C > T, rs10120688 G > A, rs4251961 T > C, rs3778355 G > C, rs1330344 C > T, rs5275 A > G/A > T, and rs3779647 C > T) were "negative modifiers" and associated with a reduced risk in aspirin users (-2.74 </= RERI </= -0.95). Conclusion: This preliminary study suggests that polymorphisms in genes involved in platelets activity, angiogenesis and inflammatory response might modify the risk of aspirin-related UGIH. Further studies with larger sample size and in different populations are needed to confirm our findings. If confirmed, this might have great impact on public health, thanks to aspirin's prophylactic properties in diseases of high incidence and severity

Cardiovascular Screening Practices and Statin Prescription Habits in Patients with Psoriasis among Dermatologists, Rheumatologists and Primary Care Physicians

Patients with psoriasis have a higher prevalence of cardiovascular risk factors. This study evaluated cardio-vascular screening practices and statin prescribing habits among dermatologists, rheumatologists and primary care physicians (PCPs) through an online questionnaire, which was distributed through the Spanish scientific societies of the above-mentioned specialties. A total of 299 physicians (103 dermatologists, 94 rheumatologists and 102 PCPs) responded to the questionnaire. Of these, 74.6% reported screening for smoking, 37.8% for hypertension, 80.3% for dyslipidaemia, and 79.6% for diabetes mellitus. Notably, only 28.4% performed global screening, defined as screening for smoking, hypertension, dyslipidaemia, and diabetes mellitus by the same physician, and 24.4% reported calculating 10-year cardiovascular disease (CVD) risk, probably reflecting a lack of comprehensive cardiovascular risk assessment in these patients. This study also identified unmet needs for awareness of cardiovascular comorbidities in psoriasis and corresponding screening and treatment recommendations among PCPs. Of PCPs, 61.2% reported not being aware of the association between psoriasis and CVD and/or not being aware of its screening recommendations, and 67.6% did not consider psoriasis as a risk-enhancing factor when deciding on statin prescription. Thirteen dermatologists (12.6%) and 35 rheumatologists (37.2%) reported prescribing statins. Among those who do not prescribe, 49.7% would be willing to start their prescription

Ultrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnet.

The question of how, and how fast, magnetization can be reversed is a topic of great practical interest for the manipulation and storage of magnetic information. It is generally accepted that magnetization reversal should be driven by a stimulus represented by time-non-invariant vectors such as a magnetic field, spin-polarized electric current, or cross-product of two oscillating electric fields. However, until now it has been generally assumed that heating alone, not represented as a vector at all, cannot result in a deterministic reversal of magnetization, although it may assist this process. Here we show numerically and demonstrate experimentally a novel mechanism of deterministic magnetization reversal in a ferrimagnet driven by an ultrafast heating of the medium resulting from the absorption of a sub-picosecond laser pulse without the presence of a magnetic field

From presence to consciousness through virtual reality

Immersive virtual environments can break the deep, everyday connection between where our senses tell us we are and where we are actually located and whom we are with. The concept of 'presence' refers to the phenomenon of behaving and feeling as if we are in the virtual world created by computer displays. In this article, we argue that presence is worthy of study by neuroscientists, and that it might aid the study of perception and consciousness