199 research outputs found
Elementary constraints on autocorrelation function scalings
Elementary algebraic constraints on the form of an autocorrelation function
C(tw+t,tw)= rule out some two-time scalings found in the
literature as possible long-time asymptotic forms. The same argument leads to
the realization that two usual definitions of {\em many-time scale} relaxation
for aging systems are not equivalent
Application of a grid numerical method to calculate state-selective cross sections for electron capture in Be4+ + H(1s) collisions
Charge-transfer n partial cross sections have been calculated for collisions of Be4+ with H(1s) by means of a versatile lattice method that is applicable in a wide energy range (between 1 and 500 keV/u). The cross sections, which include up to the high-lying n = 8 level, are compared to existing semiclassical calculations in order to quantify the accuracy of the results. The reliability of the lattice method at high impact energies is confirmed by comparison with classical trajectory Monte Carlo calculations. It is found that the n partial cross sections larger than 10−18 cm2, calculated using the lattice method, agree with differences smaller than 15% with those from the method considered the most accurate at each energy. The calculation yields as well accurate total electron
capture cross sections, which are studied in detail at E = 100 keV/u to obtain a converged valueThis work has been partially supported by the Ministerio de EconomÃa y Competitividad (Spain) (Projects No. ENE2011-28200 and No. ENE2014-52432-R). with financial support from the Red Española de Supercomputación (RES; Grants No. FI-2012-2-0016, ´
No. FI-2013-1-0020, and No. FI2013-2-0006
Calculation of total cross section for electron capture in collisions of Carbon ions with H (D,T) (1s)
The calculations of total cross sections of electron capture in collisions of Cq+ with H (1s) are reviewed. At low collision energies new calculations have been performed using molecular expansions, to analyze isotope effects. The Classical Trajectory Monte Carlo method have been also applied to discuss the occuracy of previous calculatiosn and to extend the energy range of the available cross sectionsProject ENE2011-28200 (SecretarÃa de Estado de I+D+i, SPAIN
A tale of two species: the importance of native ecosystems for long-term conservation on PrÃncipe Island, Gulf of Guinea
Since it was first described in 1901, the PrÃncipe thrush Turdus xanthorhynchus has been rare and restricted to the native forest in the south of PrÃncipe Island. The Obô giant land snail Archachatina bicarinata, however, was widespread across the island and at least locally abundant until the 1990s. Since then its population has collapsed, and now, like the thrush, it is also restricted to the native forest in the south of the island. Using species distribution modelling, we show that both species are currently strongly associated with rugged and remote areas of native forest at high altitudes. We argue that their current distribution might be negatively affected by anthropogenic pressures, as both are harvested, and also because invasive alien species are expected to have deleterious effects on these species, although further studies are needed to clarify interactions between these native and introduced species. The diachronic stories of these species highlight an overlooked value of native ecosystems: their role in the conservation of widespread species that might be unable to use anthropogenic landscapes in the future. They also reinforce the need for protected areas that strive to exclude most human activities in the context of particularly sensitive biodiversity, as is often the case on oceanic islands.info:eu-repo/semantics/publishedVersio
Asymptotically Anti-de Sitter spacetimes and scalar fields with a logarithmic branch
We consider a self-interacting scalar field whose mass saturates the
Breitenlohner-Freedman bound, minimally coupled to Einstein gravity with a
negative cosmological constant in D \geq 3 dimensions. It is shown that the
asymptotic behavior of the metric has a slower fall-off than that of pure
gravity with a localized distribution of matter, due to the back-reaction of
the scalar field, which has a logarithmic branch decreasing as r^{-(D-1)/2} ln
r for large radius r.
We find the asymptotic conditions on the fields which are invariant under the
same symmetry group as pure gravity with negative cosmological constant
(conformal group in D-1 dimensions). The generators of the asymptotic
symmetries are finite even when the logarithmic branch is considered but
acquire, however, a contribution from the scalar field.Comment: 7 pages, CECS style, references adde
Variable mode-mixity during fatigue cycles – crack tip parameters determined from displacement fields measured by digital image correlation
This paper focusses on discussing equivalent stress intensity factors and kink angles after a change of mode-mixity from one cycle to the next and when the mode-mixity changes continuously during the fatigue cycles. Thin-walled tubes with through-wall cracks have been loaded by proportional and non-proportional tension and torsion. In the experimental investigation, the region of fatigue crack growth was observed by applying the digital image correlation technique. Data on the variations of the displacement and strain fields during the cycles were acquired and used to determine mixed-mode variations of stress intensity factors associated with opening modes I, II and III. For each specific specimen the crack path was observed in order to relate its curvature – both kinks and continuously developing warped cracks – with the variations of the displacement field and associated stress intensity factors
N-terminal-pro-B type natriuretic peptide as a useful tool to evaluate pulmonary hypertension and cardiac function in CDH infants
Objective: In congenital diaphragmatic hernia (CDH) the severity of pulmonary hypertension (PH) is considered, by several authors, determinant of clinical outcome. Plasmatic N-terminal-pro-B type natriuretic peptide (NT-proBNP) might be useful in diagnosis and management of PH in newborns, although its interest in CDH infants remains to be defined. Early NT-proBNP levels were assessed in CDH infants and correlated with cardiovascular echocardiographic parameters. Patients and Methods: 28 newborns, CDH and age-matched controls were enrolled in a prospective study. Clinical condition, NT-proBNP plasmatic levels, echo parameters of PH and biventricular function were assessed at 24 h after delivery as well as survival outcome. Results: Estimated mean pulmonary pressure and NT-proBNP were significantly higher in CDH than control infants. NT-proBNP significantly correlated with estimated pulmonary artery pressure, right ventricular Tei index, and tricuspid E/A ratio. Additionally, we found that CDH infants with NT-proBNP >11,500 pg/ml experienced a worse prognosis. Conclusions: We demonstrated that PH is associated with NT-proBNP elevation and diastolic impairment in CDH infants. Early elevations in NT-proBNP levels seem to alert for a subset of CDH infants with worse prognosis. Copyrigh
Excess adiposity and low physical fitness hamper Supine-to-Stand test performance among sedentary adolescents
Objective: The aim of this study was to analyze the relationship between body adiposity and physical fitness with performance in the Supine-to-Stand test (STS-test) in sedentary adolescents. Methods: Sixty-two adolescents, of both sexes, between 10 and 16 years old, participated in the study. Body mass (BM), height, waist circumference (WC), fat mass (FM), fat-free mass (FFM), right and left handgrip strength (HGS-right, HGS-left), abdominal resistance (ABDO), flexibility (FLEX), and cardiorespiratory fitness (VO2peak) were measured. Body mass index (BMI), z-score BMI (BMI-z), tri-ponderal mass index (TMI) and waist-to-height ratio (WHtR) were calculated. The STS-test was applied to evaluate the STS-MC by the movement patterns in the execution of the test. The STS-time in seconds (s) was categorized into terciles: fast (FG  2.6 s). One-way ANOVA, Chi-square, Spearman's correlation coefficient as well as non-parametric tests were used, with significance p ≤ 0.05. Results: The SG presented higher BMI, BMI-z, TMI, WHtR, FM, %FM, as well as lower averages for %FFM, HGS-right, HGS-left, FLEX, ABDO, VO2peak, VO2peak relative to BM (VO2peakBM) in relation to GF. The BMI, BMI-z, TMI, WC, WHtR and FM showed moderate and direct correlations with STS-time and inverse with STS-MC (p < 0.01). HGS-right, HGS-left, ABDO, and VO2peakBM showed moderate and an inverse correlation with STS-time (p < 0.05). The VO2peakBM was moderate and with direct correlations to STS-MC (p < 0.01). Conclusion: It is concluded that excess fat and low physical fitness hamper STS-test performance. Therefore, the STS-test can be used for screening students to assess MC
Linea de base para la toma de desiciones en bioseguridad: desarrollo de un modelo para la evaluación de flujo de genes en yuca III. Persistencia de plantas voluntarias en campos del agricultor de yuca (Manihot esculenta Crantz)
Potencial alelopático de extratos aquosos de Melissa officinalis L. e Mentha x villosa L. na germinação e vigor de sementes de Plantago major L.
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