Thermal nucleation of cavities in liquid helium at negative pressures

We have investigated the nucleation rate at which cavities are formed in 4He and 3He at negative pressures due to thermal fluctuations. To this end, we have used a density functional that reproduces the He liquid-gas interface along the coexistence line. The inclusion of thermal effects in the calculation of the barrier against nucleation results in a sizable decrease of the absolute value of the tensile strength above 1.5 K.

Nucleation in supersaturated solutions 3He in 4He at negative pressure.

Depending on the 3He concentration, thermal nucleation in 3-4He supersaturated liquid mixtures at negative pressures may be originated either by bubble or by 3rich drop formation. We have investigated this phenomenon within a density-functional approach, determining the regions in the pressure¿3He-concentration plane where bubbles or drops likely drive the nucleation process. As an illustrative example, we also give the homogeneous nucleation pressure corresponding to 50 and 100 mK temperature.

Exotic dynamically generated baryons with negative charm quantum number

Following a model based on the SU(8) symmetry that treats heavy pseudoscalars and heavy vector mesons on an equal footing, as required by heavy quark symmetry, we study the interaction of baryons and mesons in coupled channels within an unitary approach that generates dynamically poles in the scattering T-matrix. We concentrate in the exotic channels with negative charm quantum number for which there is the experimental claim of one state.

Liquid-liquid phase transition for soft-core attractive potential

Using event-driven molecular dynamics simulations, we study a three-dimensional one-component system of spherical particles interacting via a discontinuous potential combining a repulsive square soft core and an attractive square well. In the case of a narrow attractive well, it has been shown that this potential has two metastable gas-liquid critical points. Here we systematically investigate how the changes of the parameters of this potential affect the phase diagram of the system. We find a broad range of potential parameters for which the system has both a gas-liquid critical point C1 and a liquid-liquid critical point C2. For the liquid-gas critical point we find that the derivatives of the critical temperature and pressure, with respect to the parameters of the potential, have the same signs: they are positive for increasing width of the attractive well and negative for increasing width and repulsive energy of the soft core. This result resembles the behavior of the liquid-gas critical point for standard liquids. In contrast, for the liquid-liquid critical point the critical pressure decreases as the critical temperature increases. As a consequence, the liquid-liquid critical point exists at positive pressures only in a finite range of parameters. We present a modified van der Waals equation which qualitatively reproduces the behavior of both critical points within some range of parameters, and gives us insight on the mechanisms ruling the dependence of the two critical points on the potential¿s parameters. The soft-core potential studied here resembles model potentials used for colloids, proteins, and potentials that have been related to liquid metals, raising an interesting possibility that a liquid-liquid phase transition may be present in some systems where it has not yet been observed.

Expanding scroll rings and negative tension turbulence in a model of excitable media

Scroll waves in excitable media, described by the Barkley model, are studied. In the parameter region of weak excitability, negative tension of wave filaments is found. It leads to expansion of scroll rings and instability of wave filaments. A circular filament tends to stretch, bend, loop, and produce an expanding tangle that fills up the volume. The filament does not undergo fragmentation before it touches the boundaries. Statistical properties of such Winfree turbulence of scroll waves are numerically investigated.

Effects of math anxiety on student success in higher education

This study examines whether math anxiety and negative attitudes toward mathematics have an effect on university students" academic achievement in a methodological course forming part of their degree. A total of 193 students were presented with a math anxiety test and some questions about their enjoyment, self-confidence and motivation regarding mathematics, and their responses were assessed in relation to the grades they had obtained during continuous assessment on a course entitled"Research Design". Results showed that low performance on the course was related to math anxiety and negative attitudes toward mathematics. We suggest that these factors may affect students" performance and should therefore be taken into account in attempts to improve students" learning processes in methodological courses of this kind.

Aminogenesis control in fermented sausages manufactured with pressurized meat batter and starter culture

The application of high hydrostatic pressure (200 MPa) to meat batter just before sausage fermentation and the inoculation of starter culture were studied to improve the safety and quality of traditional Spanish fermented sausages (fuet and chorizo). Higher amounts of biogenic amines were formed in chorizo than in fuet. Without interfering with the ripening performance in terms of acidification, drying and proteolysis, hydrostatic pressure prevented enterobacteria growth but did not affect Gram-positive bacteria significantly. Subsequently, a strong inhibition of diamine (putrescine and cadaverine) accumulation was observed, but that of tyramine was not affected. The inoculated decarboxylase-negative strains, selected from indigenous bacteria of traditional sausages, were resistant to the HHP treatment, being able to lead the fermentation process, prevent enterococci development and significantly reduce enterobacteria counts. In sausages manufactured with either non-pressurized or pressurized meat batter, starter culture was the most protective measure against the accumulation of tyramine and both diamines.

The effect of pesticides and alien invesive species on soil biota and litter decomposition rates in a Mediterrean-climate ecosystem of Western Australia

Ecosystems are complex systems and changing one of their components can alter their whole functioning. Decomposition and biodiversity are two factors that play a role in this stability, and it is vital to study how these two factors are interrelated and how other factors, whether of human origin or not, can affect them. This study has tested different hypotheses regarding the effects of pesticides and invasive species on the biodiversity of the soil fauna and litter decomposition rate. Decomposition was measured using the litterbags technique. Our results indicate that pesticides had a negative effect on decomposition whereas invasive species increased decomposition rate. At the same time, the diversity of the soil biota was unaffected by either factor. These results allow us to better understand the response of important ecosystem functions to human‐induced alterations, in order to mitigate harmful effects or restore them wherever necessary.

Modulation of plant HMG-CoA reductase by protein phosphatase 2A: Positive and negative control at a key node of metabolism

The enzyme HMG-CoA reductase (HMGR) has a key regulatory role in the mevalonate pathway for isoprenoid biosynthesis, critical not only for normal plant development, but also for the adaptation to demanding environmental conditions. Consistent with this notion, plant HMGR is modulated by many diverse endogenous signals and external stimuli. Protein phosphatase 2A (PP2A) is involved in auxin, abscisic acid, ethylene and brassinosteroid signaling and now emerges as a positive and negative multilevel regulator of plant HMGR, both during normal growth and in response to a variety of stress conditions. The interaction with HMGR is mediated by B" regulatory subunits of PP2A, which are also calcium binding proteins. The new discoveries uncover the potential of PP2A to integrate developmental and calcium-mediated environmental signals in the control of plant HMGR.

Persistence of cognitive impairment and its negative impact on psychosocial functioning in lithium-treated, euthymic bipolar patients: a 6-year follow-up study.

BACKGROUND: Previous cross-sectional studies report that cognitive impairment is associated with poor psychosocial functioning in euthymic bipolar patients. There is a lack of long-term studies to determine the course of cognitive impairment and its impact on functional outcome. Method A total of 54 subjects were assessed at baseline and 6 years later; 28 had DSM-IV TR bipolar I or II disorder (recruited, at baseline, from a Lithium Clinic Program) and 26 were healthy matched controls. They were all assessed with a cognitive battery tapping into the main cognitive domains (executive function, attention, processing speed, verbal memory and visual memory) twice over a 6-year follow-up period. All patients were euthymic (Hamilton Rating Scale for Depression score lower than 8 and Young mania rating scale score lower than 6) for at least 3 months before both evaluations. At the end of follow-up, psychosocial functioning was also evaluated by means of the Functioning Assessment Short Test. RESULTS: Repeated-measures multivariate analysis of covariance showed that there were main effects of group in the executive domain, in the inhibition domain, in the processing speed domain, and in the verbal memory domain (p<0.04). Among the clinical factors, only longer illness duration was significantly related to slow processing (p=0.01), whereas strong relationships were observed between impoverished cognition along time and poorer psychosocial functioning (p<0.05). CONCLUSIONS: Executive functioning, inhibition, processing speed and verbal memory were impaired in euthymic bipolar out-patients. Although cognitive deficits remained stable on average throughout the follow-up, they had enduring negative effects on psychosocial adaptation of patients.

Molecular tracking of coagulase-negative staphylococcal isolates from catheter-related infections

Three molecular typing methods (pulsed-field electrophoresis, localization of the mecA gene, and probing the vicinity of mec) have been used for the characterization of 40 catheter-related isolates of coagulase-negative staphylococci (CNS) in 14 patients admitted to the same hospital. The 40 isolates yielded 14 different SmaI banding patterns and corresponding unique localizations of mecA, each associated with a unique ClaI mecA polymorph. In 6 of the 14 patients the contaminated skin at the catheter entry site was the source of 4 local infections and 2 cases of bacteremia. A contaminated hub was the origin of 2 local infections and 4 cases of bacteremia in 6 more patients. The remaining 2 patients had positive cultures from both skin and catheter hub. In each bacteremic patient, the CNS recovered from catheter-related sites (tip, skin, and/or hub) and the CNS recovered from blood were identical, but each of these matching isolates was unique to the particular patient, indicating a low rate of cross-infection from patient to patient. Although classical methods for typing CNS (e.g., biotype and antibiotype) are readily available for most hospital laboratories, they have limitations concerning reproducibility and discriminatory power. Molecular epidemiologic techniques can provide powerful support to traditional techniques in determining the etiologic role of CNS in the disease process

Two different epidemiological scenarios of border disease in the populations of Pyrenean chamois (Rupicapra p. pyrenaica) after the first disease outbreaks

Since 2001 several outbreaks of a new disease associated with Border disease virus (BDV) infection have caused important declines in Pyrenean chamois (Rupicapra pyrenaica) populations in the Pyrenees. The goal of this study was to analyze the post-outbreak BDV epidemiology in the first two areas affected by disease with the aim to establish if the infection has become endemic. We also investigated if BDV infected wild and domestic ruminants sharing habitat with chamois. Unexpectedly, we found different epidemiological scenarios in each population. Since the disease outbreaks, some chamois populations recuperated quickly, while others did not recover as expected. In chamois from the first areas, prevalence was high (73.47%) and constant throughout the whole study period and did not differ between chamois born before and after the BDV outbreak; in all, BDV was detected by RT-PCR in six chamois. In the other areas, prevalence was lower (52.79%) and decreased during the study period; as well, prevalence was significantly lower in chamois born after the disease outbreak. No BDV were detected in this population. A comparative virus neutralisation test performed with four BDV strains and one Bovine viral diarrhoea virus (BVDV) strain showed that all the chamois had BDV-specific antibodies. Pestivirus antibodies were detected in all the rest of analyzed species, with low prevalence values in wild ruminants and moderate values in domestic ruminants. No viruses were detected in these species. These results confirm the hypothesis that outbreaks of BDV infection only affect the Pyrenean chamois, although other wild ruminants can occasionally be infected. In conclusion, two different scenarios have appeared since the first border disease outbreaks in Pyrenean chamois: on the one hand frequent BDV circulation with possible negative impact on population dynamics in some areas and on the other, lack of virus circulation and quick recovery of the chamois population.

The Impact of a Character Posture Model on the Communication of Affect in an Immersive Virtual Environment

This paper presents the quantitative and qualitative findings from an experiment designed to evaluate a developing model of affective postures for full-body virtual characters in immersive virtual environments (IVEs). Forty-nine participants were each requested to explore a virtual environment by asking two virtual characters for instructions. The participants used a CAVE-like system to explore the environment. Participant responses and their impression of the virtual characters were evaluated through a wide variety of both quantitative and qualitative methods. Combining a controlled experimental approach with various data-collection methods provided a number of advantages such as providing a reason to the quantitative results. The quantitative results indicate that posture plays an important role in the communication of affect by virtual characters. The qualitative findings indicated that participants attribute a variety of psychological states to the behavioral cues displayed by virtual characters. In addition, participants tended to interpret the social context portrayed by the virtual characters in a holistic manner. This suggests that one aspect of the virtual scene colors the perception of the whole social context portrayed by the virtual characters. We conclude by discussing the importance of designing holistically congruent virtual characters especially in immersive settings.

Positive Outcomes Influence the Rate and Time to Publication, but Not the Impact Factor of Publications of Clinical Trial Results

Objectives: Publication bias may affect the validity of evidence based medical decisions. The aim of this study is to assess whether research outcomes affect the dissemination of clinical trial findings, in terms of rate, time to publication, and impact factor of journal publications. Methods and Findings: All drug-evaluating clinical trials submitted to and approved by a general hospital ethics committee between 1997 and 2004 were prospectively followed to analyze their fate and publication. Published articles were identified by searching Pubmed and other electronic databases. Clinical study final reports submitted to the ethics committee, final reports synopses available online and meeting abstracts were also considered as sources of study results. Study outcomes were classified as positive (when statistical significance favoring experimental drug was achieved), negative (when no statistical significance was achieved or it favored control drug) and descriptive (for non-controlled studies). Time to publication was defined as time from study closure to publication. A survival analysis was performed using a Cox regression model to analyze time to publication. Journal impact factors of identified publications were recorded. Publication rate was 48·4% (380/785). Study results were identified for 68·9% of all completed clinical trials (541/785). Publication rate was 84·9% (180/212) for studies with results classified as positive and 68·9% (128/186) for studies with results classified as negative (p<0·001). Median time to publication was 2·09 years (IC95 1·61-2·56) for studies with results classified as positive and 3·21 years (IC95 2·69-3·70) for studies with results classified as negative (hazard ratio 1·99 (IC95 1·55-2·55). No differences were found in publication impact factor between positive (median 6·308, interquartile range: 3·141-28·409) and negative result studies (median 8·266, interquartile range: 4·135-17·157). Conclusions: Clinical trials with positive outcomes have significantly higher rates and shorter times to publication than those with negative results. However, no differences have been found in terms of impact factor.

Fiscal sustainability and fiscal shocks in a dollarized and oil-exporting country: Ecuador

This paper investigates the fiscal sustainability of an emerging, dollarized, oil-exporting country: Ecuador. A cointegrated VAR approach is adopted in testing, first, if the intertemporal budget constraint is satisfied in Ecuador and, second, in identifying the permanent and transitory shocks that affect a fiscal policy characterized by inertia and a heavy dependence on oil revenues. Following confirmation that the debt-GDP ratio does not place the Ecuadorian budget under any pressure, we reformulate the model and identify two forces that push the fiscal system out of equilibrium, namely, economic activity and oil revenues implemented in the government budget. We argue that Ecuador needs to recover control of its monetary policy and to promote the diversification of its economy in order that non-oil tax revenues can replace oil revenues as a pushing force. Finally, we calculate quarterly elasticities of tax revenues with respect to Ecuador’s GDP and that of eight Eurozone countries. We illustrate graphically how the Eurozone countries with low positive or high negative elasticities’ levels suffer debt problems after the crisis. This finding emphasizes the pressing need for Ecuador to strengthen the connection between its tax revenues and output, and also suggests that the convergence of these elasticities in the Eurozone might contribute to the success of an eventually future fiscal union.