Effect of strain on surface diffusion in semiconductor heteroepitaxy

We present a first-principles analysis of the strain renormalization of the cation diffusivity on the GaAs(001) surface. For the example of In/GaAs(001)-c(4x4) it is shown that the binding of In is increased when the substrate lattice is expanded. The diffusion barrier \Delta E(e) has a non-monotonic strain dependence with a maximum at compressive strain values (e 0) studied. We discuss the consequences of spatial variations of both the binding energy and the diffusion barrier of an adatom caused by the strain field around a heteroepitaxial island. For a simplified geometry, we evaluate the speed of growth of two coherently strained islands on the GaAs(001) surface and identify a growth regime where island sizes tend to equalize during growth due to the strain dependence of surface diffusion.Comment: 10 pages, 8 figures, LaTeX2e, to appear in Phys. Rev. B (2001). Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

Modified f(R) gravity from scalar-tensor theory and inhomogeneous EoS dark energy

The reconstruction of f(R)-gravity is showed by using an auxiliary scalar field in the context of cosmological evolution, this development provide a way of reconstruct the form of the function f (R) for a given evolution of the Hubble parameter. In analogy, f(R)-gravity may be expressed by a perfect fluid with an inhomogeneous equation of state that depends on the Hubble parameter and its derivatives. This mathematical equivalence that may confuse about the origin of the mechanism that produces the current acceleration, and possibly the whole evolution of the Hubble parameter, is shown here.Comment: 8 page

Baseline characteristics of patients in the reduction of events with darbepoetin alfa in heart failure trial (RED-HF)

<p>Aims: This report describes the baseline characteristics of patients in the Reduction of Events with Darbepoetin alfa in Heart Failure trial (RED-HF) which is testing the hypothesis that anaemia correction with darbepoetin alfa will reduce the composite endpoint of death from any cause or hospital admission for worsening heart failure, and improve other outcomes.</p> <p>Methods and results: Key demographic, clinical, and laboratory findings, along with baseline treatment, are reported and compared with those of patients in other recent clinical trials in heart failure. Compared with other recent trials, RED-HF enrolled more elderly [mean age 70 (SD 11.4) years], female (41%), and black (9%) patients. RED-HF patients more often had diabetes (46%) and renal impairment (72% had an estimated glomerular filtration rate <60 mL/min/1.73 m2). Patients in RED-HF had heart failure of longer duration [5.3 (5.4) years], worse NYHA class (35% II, 63% III, and 2% IV), and more signs of congestion. Mean EF was 30% (6.8%). RED-HF patients were well treated at randomization, and pharmacological therapy at baseline was broadly similar to that of other recent trials, taking account of study-specific inclusion/exclusion criteria. Median (interquartile range) haemoglobin at baseline was 112 (106–117) g/L.</p> <p>Conclusion: The anaemic patients enrolled in RED-HF were older, moderately to markedly symptomatic, and had extensive co-morbidity.</p&gt

Microbiota and neurologic diseases : potential effects of probiotics

Background: The microbiota colonizing the gastrointestinal tract have been associated with both gastrointestinal and extra-gastrointestinal diseases. In recent years, considerable interest has been devoted to their role in the development of neurologic diseases, as many studies have described bidirectional communication between the central nervous system and the gut, the so-called "microbiota-gut-brain axis". Considering the ability of probiotics (i.e., live non-pathogenic microorganisms) to restore the normal microbial population and produce benefits for the host, their potential effects have been investigated in the context of neurologic diseases. The main aims of this review are to analyse the relationship between the gut microbiota and brain disorders and to evaluate the current evidence for the use of probiotics in the treatment and prevention of neurologic conditions. Discussion: Overall, trials involving animal models and adults have reported encouraging results, suggesting that the administration of probiotic strains may exert some prophylactic and therapeutic effects in a wide range of neurologic conditions. Studies involving children have mainly focused on autism spectrum disorder and have shown that probiotics seem to improve neuro behavioural symptoms. However, the available data are incomplete and far from conclusive. Conclusions: The potential usefulness of probiotics in preventing or treating neurologic diseases is becoming a topic of great interest. However, deeper studies are needed to understand which formulation, dosage and timing might represent the optimal regimen for each specific neurologic disease and what populations can benefit. Moreover, future trials should also consider the tolerability and safety of probiotics in patients with neurologic diseases

Variability in Iron Bound Organic Carbon in the Mississippi River Influenced Shelf Sediments

Reactive iron and associated organic carbon estimates from Mississippi river influenced shelf sediments of the northern Gulf of Mexic

Variability in Iron Bound Organic Carbon in the Mississippi River Influenced Shelf Sediments

Reactive iron and associated organic carbon estimates from Mississippi river influenced shelf sediments of the northern Gulf of Mexic

Low Temperature Surface Passivation Of Silicon Solar Cells

Low temperature surface passivation is a process that has a potential to reduce the input energy cost of the solar cell with minimum modification of the manufacturing bed, while keeping the efficiency, and life of the cells within acceptable range of values. In this review, low temperature deposition methods of SiO2, Al2O3, a-Si:H, silicon nano particles (NPs), and organic materials, are considered. Surface recombination velocities, defect densities, stability of these passivating layers are discussed along with the mechanisms of passivation on Si surface

Low Temperature Surface Passivation Of Silicon Solar Cells

Low temperature surface passivation is a process that has a potential to reduce the input energy cost of the solar cell with minimum modification of the manufacturing bed, while keeping the efficiency, and life of the cells within acceptable range of values. In this review, low temperature deposition methods of SiO2, Al2O3, a-Si:H, silicon nano particles (NPs), and organic materials, are considered. Surface recombination velocities, defect densities, stability of these passivating layers are discussed along with the mechanisms of passivation on Si surface

Mossbauer spectroscopic study of ion beam mixing at Fe-Cu interface

Metastable FeCu alloy films have been synthesized by ion beam induced atomic mixing at the Fe-Cu interface. Polycrystalline copper foils coated with 180 λ thick overlayer of iron (enriched to ˜33% in the concentration of 57Fe mossbauer isotope) have been, bombarded with Kr+ ions having energies in the range between 30 keVand 120 keV at a dose of -1016ions/cm2. The as-deposited and ion beam mixed composites have been characterized by using the submicron sensitive technique of conversion electron mossbauer spectroscopy (CEMS). The ion energy dependence of the extent of mixing has been compared with model calculations of energy deposition in interface layers. By deconvoluting the complex mossbauer spectra it has been shown that interface alloy formed by ion mixing exhibits the presence of a random chemical disorder. The ferromagnetic spectral contributions have been analyzed in terms of the presence of one or more copper atoms (acting as magnetic holes in the near neighbour shells of the 57Fe atoms)