12,088 research outputs found
Cigarette smokers and vascular damage: analysis of mechanisms that impair endothelium dependent vasodilatation
No full textCigarette smokers and vascular damage: analysis of mechanisms that impair endothelium dependent vasodilatatio
Additional Non Equilibrium Processes in the Dynamic Interaction between Flux Quanta and Defects
No full textEffect of ketogenic mediterranean diet with phytoextracts and low carbohydrates/high-protein meals on weight, cardiovascular risk factors, body composition and diet compliance in Italian council employees
No full textAbstract Background There has been increased interest in recent years in very low carbohydrate ketogenic diets (VLCKD) that, even though they are much discussed and often opposed, have undoubtedly been shown to be effective, at least in the short to medium term, as a tool to tackle obesity, hyperlipidemia and some cardiovascular risk factors. For this reason the ketogenic diet represents an interesting option but unfortunately suffers from a low compliance. The aim of this pilot study is to ascertain the safety and effects of a modified ketogenic diet that utilizes ingredients which are low in carbohydrates but are formulated to simulate its aspect and taste and also contain phytoextracts to add beneficial effects of important vegetable components. Methods The study group consisted of 106 Rome council employees with a body mass index of ≥ 25, age between 18 and 65 years (19 male and 87 female; mean age 48.49 ± 10.3). We investigated the effects of a modified ketogenic diet based on green vegetables, olive oil, fish and meat plus dishes composed of high quality protein and virtually zero carbohydrate but which mimic their taste, with the addition of some herbal extracts (KEMEPHY ketogenic Mediterranean with phytoextracts). Calories in the diet were unlimited. Measurements were taken before and after 6 weeks of diet. Results There were no significant changes in BUN, ALT, AST, GGT and blood creatinine. We detected a significant (p 2 to 29.01 Kg/m2), body weight (86.15 kg to 79.43 Kg), percentage of fat mass (41.24% to 34.99%), waist circumference (106.56 cm to 97.10 cm), total cholesterol (204 mg/dl to 181 mg/dl), LDLc (150 mg/dl to 136 mg/dl), triglycerides (119 mg/dl to 93 mg/dl) and blood glucose (96 mg/dl to 91 mg/dl). There was a significant (p Conclusions The KEMEPHY diet lead to weight reduction, improvements in cardiovascular risk markers, reduction in waist circumference and showed good compliance.</p
Influence of point defects injection on the stability of a supersaturated Ga-Si solid solution
No full textThe ultrahigh doping levels of Si needed in ultradownscaled electronic devices can be achieved forming supersaturated solid solutions by solid-phase epitaxy. These solutions are, however, unstable upon high-temperature annealing, and electrical deactivation of the impurities exceeding the solid solubility limit occurs. There are indications that deactivation is driven by the interaction of impurities with native (i.e., intrinsic) defects, but the relevant process has not been studied in detail thus far, nor have the defect complexes presumably causing the deactivation been identified. Here we use light-ion beam treatments and Rutherford backscattering analysis combined with first-principles density-functional calculations to investigate the interaction of a specific Group-III acceptor, Ga, with native defects-mostly self-interstitials-generated by irradiation at room temperature, or upon thermal annealing. Monitoring the off-lattice displacement of Ga during He-beam irradiation at room temperature or after high-temperature annealing by channeling analysis, we find a partitioning into substitutional and tetrahedral interstitial Ga populations in the former case, and a partitioning into substitutional and random populations in the latter. Based on ab initio calculations and angular-scan Rutherford backscattering spectroscopy, we are able to interpret the results in terms of (a) self-interstitial-assisted enhanced diffusion of Ga, and (b) the subsequent formation of stable Ga-Ga and Ga-Ga-Si complexes. This suggests that deactivation is indeed mediated by native defects (mainly self-interstitials) causing the off-site displacement of the Ga impurity
Carrier mobility and strain effect in heavily doped p-type Si
No full textAlthough carrier mobility (μ) in Si is a fundamental property deeply investigated since 40 years, a complete understanding of its characteristics over a large range of carrier concentration is still lacking. For example, the effect of strain was largely debated and μ enhancement was demonstrated in strained Si channels where the carrier concentration is 10^20 cm−3), which is actually of fundamental interest for USJ applications, many questions are still open about μ: why is μ lower in presence of some dopants with respect to other chemical species? The relevant point is that high μ in either n- or p-type Si is observed when the dopant has a covalent radius smaller than Si and that, at the concentration at which the chemical effect on the μ is visible, an appreciable strain is generated in the doped layer. We present here an experiment to study the dependence of the hole μ on the dopant species in heavily doped p-type Si under low electrical field. The Hall carrier concentration and μ has been measured in Si co-implanted with B and Ga in the (0.1–2) × 10^20 cm−3 range. The strain induced by substitutional dopants, detected by high resolution X-ray diffraction (HRXRD), has been varied by changing the B and Ga concentration. The effect of strain on μ has been disentangled and a linear dependence of 1/μ on the perpendicular strain has been found. Using this relationship we demonstrate that the strain induced by the substitutional dopant can account for the effect of chemical species on charge carrier μ
Fluorine incorporation during Si solid phase epitaxy
No full textWe have investigated the F incorporation and segregation in preamorphized Si during solid phase epitaxy (SPE) at different temperatures and for several implanted-F energies and fluences. The Si samples were amorphized to a depth of 550 nm by implanting Si at liquid nitrogen temperature and then enriched with F at different energies (65-150 keV) and fluences (0.07-5 x 10(14) F/cm(2)). Subsequently, the samples were regrown by SPE at different temperatures: 580, 700 and 800 degrees C. We have found that the amount of F incorporated after SPE strongly depends on the SPE temperature and on the energy and fluence of the implanted-F, opening the possibility to tailor the F profile during SPE
Fluorine segregation and incorporation during solid-phase epitaxy of Si
No full textWe report on the F incorporation into Si during solid-phase epitaxy (SPE) at 580 degrees C and with the presence of B and/or As, clarifying the F incorporation mechanism into Si. A strong segregation of F at the moving amorphous-crystalline interface has been characterized, leading to a SPE rate retardation and to a significant loss of F atoms through the surface. In B- or As-doped samples, an enhanced, local F incorporation is observed, whereas in the case of B and As co-implantation (leading to compensating dopant effect), a much lower F incorporation is achieved at the dopant peak. The F enhanced incorporation with the presence of B or As is shown to be a kinetic effect related to the SPE rate modification by doping, whereas the hypothesis of a F-B or F-As chemical bonding is refused. These results shed new light on the application of F in the fabrication of ultrashallow junctions in future generation devices
Study on the Mg-Li-Zn ternary alloy system with improved mechanical properties, good degradation performance and different responses to cells
No full textNovel Mg-(3.5, 6.5wt%)Li-(0.5, 2, 4wt%)Zn ternary alloys were developed as new kinds of biodegradable metallic materials with potential for stent application. Their mechanical properties, degradation behavior, cytocompatibility and hemocompatibility were studied. These potential biomaterials showed higher ultimate tensile strength than previously reported binary Mg-Li alloys and ternary Mg-Li-X (X=Al, Y, Ce, Sc, Mn and Ag) alloys. Among the alloys studied, the Mg-3.5Li-2Zn and Mg-6.5Li-2Zn alloys exhibited comparable corrosion resistance in Hank's solution to pure magnesium and better corrosion resistance in a cell culture medium than pure magnesium. Corrosion products observed on the corroded surface were composed of Mg(OH)2, MgCO3 and Ca-free Mg/P inorganics and Ca/P inorganics. In vitro cytotoxicity assay revealed different behaviors of Human Umbilical Vein Endothelial Cells (HUVECs) and Human Aorta Vascular Smooth Muscle Cells (VSMCs) to material extracts. HUVECs showed increasing nitric oxide (NO) release and tolerable toxicity, whereas VSMCs exhibited limited decreasing viability with time. Platelet adhesion, hemolysis and coagulation tests of these Mg-Li-Zn alloys showed different degrees of activation behavior, in which the hemolysis of the Mg-3.5Li-2Zn alloy was lower than 5%. These results indicated the potential of the Mg-Li-Zn alloys as good candidate materials for cardiovascular stent applications. Statement of significance: Mg-Li alloys are promising as absorbable metallic biomaterials, which however have not received significant attention since the low strength, controversial corrosion performance and the doubts in Li toxicity. The Mg-Li-Zn alloy in the present study revealed much improved mechanical properties higher than most reported binary Mg-Li and ternary Mg-Li-X alloys, with superior corrosion resistance in cell culture media. Surprisingly, the addition of Li and Zn showed increased nitric oxide release. The present study indicates good potential of Mg-Li-Zn alloy as absorbable cardiovascular stent material.Accepted Author ManuscriptBiomaterials & Tissue Biomechanic
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