Anisotropic Confinement, Electronic Coupling and Strain Induced Effects Detected by Valence-Band Anisotropy in Self-Assembled Quantum Dots

A method to determine the effects of the geometry and lateral ordering on the electronic properties of an array of one-dimensional self-assembled quantum dots is discussed. A model that takes into account the valence-band anisotropic effective masses and strain effects must be used to describe the behavior of the photoluminescence emission, proposed as a clean tool for the characterization of dot anisotropy and/or inter-dot coupling. Under special growth conditions, such as substrate temperature and Arsenic background, 1D chains of In(0.4)Ga(0.6) As quantum dots were grown by molecular beam epitaxy. Grazing-incidence X-ray diffraction measurements directly evidence the strong strain anisotropy due to the formation of quantum dot chains, probed by polarization-resolved low-temperature photoluminescence. The results are in fair good agreement with the proposed model.

Internal Strain Distribution in Freestanding Porous Silicon

Elastic properties of freestanding porous silicon layers fabricated by electrochemical anodization were studied by Raman scattering. Different anodization currents provided different degrees of porosity in the nanometer scale. Raman lines corresponding to the longitudinal optical phonons of crystalline and amorphous phases were observed. The amorphous volume fraction increased and the phonon frequencies for both phases decreased with increasing porosity. A strain distribution model is proposed whose fit to the experimental results indicates that the increasing nanoscale porosity causes strain relaxation in the amorphous domains and strain buildup in the crystalline ones. The present analysis has significant implications on the estimation of the crystalline Si domain's characteristic size from Raman scattering data. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3225832] All rights reserved.

Purification and characterization of an antimicrobial peptide produced by Pseudomonas sp strain 4B

An antimicrobial peptide produced by a bacterium isolated from the effluent pond of a bovine abattoir was purified and characterized. The strain was characterized by biochemical profiling and 16S rDNA sequencing as Pseudomonas sp. The antimicrobial peptide was purified by ammonium sulfate precipitation, gel filtration, and ion exchange chromatography. Direct activity on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was observed. A major band on SDS-PAGE suggested that the antimicrobial peptide has a molecular mass of about 30 kDa. The substance was inhibitory to a broad range of indicator strains, including pathogenic and food spoilage bacteria such as Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, among other. The partially purified antimicrobial substance remained active over a wide temperature range and was resistant to all proteases tested. This substance showed different properties than other antimicrobials from Pseudomonas species, suggesting a novel antimicrobial peptide was characterized.

Highly Toxic Microcystis aeruginosa Strain, Isolated from So Paulo-Brazil, Produce Hepatotoxins and Paralytic Shellfish Poison Neurotoxins

While evaluating several laboratory-cultured cyanobacteria strains for the presence of paralytic shellfish poison neurotoxins, the hydrophilic extract of Microcystis aeruginosa strain SPC777-isolated from Billings`s reservoir, So Paulo, Brazil-was found to exhibit lethal neurotoxic effect in mouse bioassay. The in vivo test showed symptoms that unambiguously were those produced by PSP. In order to identify the presence of neurotoxins, cells were lyophilized, and the extracts were analyzed by HPLC-FLD and HPLC-MS. HPLC-FLD analysis revealed four main Gonyautoxins: GTX4(47.6%), GTX2(29.5%), GTX1(21.9%), and GTX3(1.0%). HPLC-MS analysis, on other hand, confirmed both epimers, with positive Zwitterions M(+) 395.9 m/z for GTX3/GTX2 and M(+) 411 m/z for GTX4/GTX1 epimers. The hepatotoxins (Microcystins) were also evaluated by ELISA and HPLC-MS analyses. Positive immunoreaction was observed by ELISA assay. Alongside, the HPLC-MS analyses revealed the presence of [l-ser(7)] MCYST-RR. The N-methyltransferase (NMT) domain of the microcystin synthetase gene mcyA was chosen as the target sequence to detect the presence of the mcy gene cluster. PCR amplification of the NMT domain, using the genomic DNA of the SPC777 strain and the MSF/MSR primer set, resulted in the expected 1,369 bp product. The phylogenetic analyses grouped the NMT sequence with the NMT sequences of other known Microcystis with high bootstrap support. The taxonomical position of M. aeruginosa SPC777 was confirmed by a detailed morphological description and a phylogenetic analysis of 16S rRNA gene sequence. Therefore, co-production of PSP neurotoxins and microcystins by an isolated M. aeruginosa strain is hereby reported for the first time.

A new monitor for routine thermal and epithermal neutron fluence rate monitoring in k(0) INAA

The Zr-Au set for monitoring the thermal and epithermal neutron fluence rate and the epithermal spectrum parameter a is not always practicable for routine application of INAA in well-thermalized facilities. An alternative set consisting of Cr, Au and Mo provides values for the thermal neutron fluence rate, f and alpha that are not significantly different from those found via the Zr-Au method and the Cd-covered Zr-method. The IRMM standard SMELS-II was analyzed using the (Au-Cr-Mo) monitor and a good agreement was obtained. (C) 2008 Elsevier Ltd. All rights reserved.

Fermentation of cacao (Theobroma cacao L.) seeds with a hybrid Kluyveromyces marxianus strain improved product quality attributes

Fermentation of Theobroma cacao (cacao) seeds is an absolute requirement for the full development of chocolate flavor precursors. An adequate aeration of the fermenting cacao seed mass is a fundamental prerequisite for a satisfactory fermentation. Here, we evaluated whether a controlled inoculation of cacao seed fermentation using a Kluyveromyces marxianus hybrid yeast strain, with an increased pectinolytic activity, would improve an earlier liquid drainage (`sweatings`) from the fermentation mass, developing a superior final product quality. Inoculation with K. marxianus increased by one third the volume of drained liquid and affected the microorganism population structure during fermentation, which was detectable up to the end of the process. Introduction of the hybrid yeast affected the profile of total seed protein degradation evaluated by polyacrylamide gel electrophoresis, with improved seed protein degradation, and reduction of titrable acidity. Sensorial evaluation of the chocolate obtained from beans fermented with the K. marxianus inoculation was more accepted by analysts in comparison with the one from cocoa obtained through natural fermentation. The increase in mass aeration during the first 24 h seemed to be fundamental for the improvement of fermentation quality, demonstrating the potential application of this improved hybrid yeast strain with superior exogenous pectinolytic activity.

Exercise training associated with diet improves heart rate recovery and cardiac autonomic nervous system activity in obese children

The purpose of this study was to test the hypotheses that in obese children: 1) hypocaloric diet (D) improves both heart rate recovery at 1 min (Delta HRR1) cfter an exercise test, and cardiac autonomic nervous system activity (CANSA) in obese children; 2) Diet and exercise training (DET) combined leads to greater improvement in both Delta HRR1 after an exercise test and in CANSA, than D alone. Moreover, we examined the relationships among Delta HRR1, CANSA, cardiorespiratory fitness and anthropometric variables (AV) in obese children submitted to D and to DET. 33 obese children (10 +/- 0.2 years; body mass index (BMI) >95(th) percentile) were divided into 2 groups: D (n = 15; BMI = 31 +/- 1 kg/m(2)) and DET (n = 18; 29 +/- 1 kg/m(2)). All children performed a maximal cardiopulmonary exercise test on a treadmill. The Delta HRR1 was defined as the difference between heart rate at peak and at 1-min post-exercise. CANSA was assessed using power spectral analysis of heart rate variability at rest. The sympathovagal balance (low frequency and high frequency ratio, LF/HF) was measured. After interventions, all obese children showed reduced body weight (P < 0.05). The D group did not improve in terms of peak VO(2), Delta HRR1 or LF/HF ratio (P > 0.05). In contrast, the DET group showed increased peak VO(2) (P = 0.01) and improved Delta HRR1 (Delta HRR1 = 37.3 +/- 2.6; P = 0.01) and LF/HF ratio (P = 0.001). The DET group demonstrated significant relationships among Delta HRR1, peak VO(2) and CANSA (P < 0.05). In conclusion, DET, in contrast to D, promoted improved Delta HRR1 and CANSA in obese children, suggesting a positive influence of increased levels of cardiorespiratory fitness by exercise training on cardiac autonomic activity.

Influence of high- and low-carbohydrate diet following glycogen-depleting exercise on heart rate variability and plasma catecholamines

The purpose of this study was to investigate the effects of a short-term low-or high-carbohydrate (CHO) diet consumed after exercise on sympathetic nervous system activity. Twelve healthy males underwent a progressive incremental test; a control measurement of plasma catecholamines and heart rate variability (HRV); an exercise protocol to reduce endogenous CHO stores; a low-or high-CHO diet (counterbalanced order) consumed for 2 days, beginning immediately after the exercise protocol; and a second resting plasma catecholamine and HRV measurement. The exercise and diet protocols and the second round of measurements were performed again after a 1-week washout period. The mean (+/- SD) values of the standard deviation of R-R intervals were similar between conditions (control, 899.0 +/- 146.1 ms; low-CHO diet, 876.8 +/- 115.8 ms; and high-CHO diet, 878.7 +/- 127.7 ms). The absolute high-and low-frequency (HF and LF, respectively) densities of the HRV power spectrum were also not different between conditions. However, normalized HF and LF (i.e., relative to the total power spectrum) were lower and higher, respectively, in the low-CHO diet than in the control diet (mean +/- SD, 17 +/- 9 normalized units (NU) and 83 +/- 9 NU vs. 27 +/- 11 NU and 73 +/- 17 NU, respectively; p < 0.05). The LF/HF ratio was higher with the low-CHO diet than with the control diet (mean +/- SD, 7.2 +/- 6.2 and 4.2 +/- 3.2, respectively; p < 0.05). The mean values of plasma catecholamines were not different between diets. These results suggest that the autonomic control of the heart rate was modified after a short-term low-CHO diet, but plasma catecholamine levels were not altered.

Peak torque and rate of torque development in elderly with and without fall history

Background Falls are one of the greatest concerns among the elderly A number of studies have described peak torque as one of the best fall-related predictor. No studies have comprehensively focused on the rate of torque development of the lower limb muscles among elderly fallers. Then, the aim of this study was to determine the relationship between muscle peak torque and rate of torque development of the lower limb joints in elderly with and without fall history It was also aimed to determine whether these parameters of muscle performance (i e, peak torque and rate of torque development) are related to the number of falls. Methods: Thirty-one women volunteered to participate in the study and were assigned in one of the groups according to the number of falls over the 12 months that preceded the present Then, participants with no fall history (Cl; n = 13; 67.6[7.5] years-old), one fall (GII; n = 8, 66 0[4 91 years-old) and two or more falls (GIII, n = 10; 67.8[8.8] years-old) performed a number of lower limb maximal isometric voluntary contractions from which peak torque and rate of torque development were quantified Findings. Primary outcomes indicated no peak torque differences between experimental groups in any lower limb joint. The rate of torque development of the knee flexor muscles observed in the non-fallers (Cl) was greater than that observed in the fallers (P < 0.05) and had a significant relationship with the number of falls (P < 0 05) Interpretation. The greater knee flexor muscles` rate of torque development found in the non-fallers in comparison to the fallers indicated that the ability of the elderly to rapidly reorganise the arrangement of the lower limb may play a significant role in allowing the elderly to recover balance after a trip. Thus, training stimulus aimed to improve the rate of torque development may be more beneficial to prevent falls among the elderly than other training stimulus, which are not specifically designed to improve the ability to rapidly produce large amounts of torque (C) 2010 Published by Elsevier Ltd

Low carbohydrate diet affects the oxygen uptake on-kinetics and rating of perceived exertion in high intensity exercise

The aim of this study was to determine if the carbohydrate (CHO) availability alters the rate of increase in the rating of perceived exertion (RPE) during high intensity exercise and whether this would be associated with physiological changes. Six males performed high intensity exercise after 48 h of controlled, high CHO (80%) and low CHO (10%) diets. Time to exhaustion was lower in the low compared to high CHO diet. The rate of increase in RPE was greater and the VO(2) slow component was lower in the low CHO diet than in the control. There was no significant condition effect for cortisol, insulin, pH, plasma glucose, potassium, or lactate concentrations. Multiple linear regression indicated that the total amplitude of VO(2) and perceived muscle strain accounted for the greatest variance in the rate of increase in RPE. These results suggest that cardiorespiratory variables and muscle strain are important afferent signals from the periphery for the RPE calculations.

Resting Heart Rate is Associated with Blood Pressure in Male Children and Adolescents

Objectives To analyze the association between resting heart rate and blood pressure in male children and adolescents and to identify if this association is mediated by important confounders. Study design Cross-sectional study carried out with 356 male children and adolescents from 8 to 18 years old. Resting heart rate was measured by a portable heart rate monitor according to recommendations and stratified into quartiles. Blood pressure was measured with an electronic device previously validated for pediatric populations. Body fatness was estimated by a dual-energy x-ray absorptiometry. Results Obese subjects had values of resting heart rate 7.8% higher than nonobese (P = .001). Hypertensive children and adolescents also had elevated values of resting heart rate (P = .001). When the sample was stratified in nonobese and obese, the higher quartile of resting heart rate was associated with hypertension in both groups of children and adolescents. Conclusions This study confirms the existence of a relationship between elevated resting heart rate and increased blood pressure in a pediatric population, independent of adiposity, ethnicity and age. (J Pediatr 2011; 158:634-7).

Ethanol production by a new pentose-fermenting yeast strain, Scheffersomyces stipitis UFMG-IMH 43.2, isolated from the Brazilian forest

The ability of a recently isolated Scheffersomyces stipitis strain (UFMG-IMH 43.2) to produce ethanol from xylose was evaluated. For the assays, a hemicellulosic hydrolysate produced by dilute acid hydrolysis of sugarcane bagasse was used as the fermentation medium. Initially, the necessity of adding nutrients (MgSO(4).7H(2)O, yeast extract and/or urea) to this medium was verified, and the yeast extract supplementation favoured ethanol production by the yeast. Then, in a second stage, assays under different initial xylose and cell concentrations, supplemented or not with yeast extract, were performed. All these three variables showed significant (p < 0.05) influence on ethanol production. The best results (ethanol yield and productivity of 0.19 g/g and 0.13 g/l/h, respectively) were obtained using the hydrolysate containing an initial xylose concentration of 30 g/l, supplemented with 5.0 g/l yeast extract and inoculated with an initial cell concentration of 2.0 g/l. S. stipitis UFMG-IMH 43.2 was demonstrated to be a yeast strain with potential for use in xylose conversion to ethanol. The establishment of the best fermentation conditions was also proved to be of great importance to increasing the product formation by this yeast strain. These findings open up new perspectives for the establishment of a feasible technology for ethanol production from hemicellulosic hydrolysates. Copyright (C) 2011 John Wiley & Sons, Ltd.

Sequential production of amylolytic and lipolytic enzymes by bacterium strain isolated from petroleum contaminated soil

Amylases and lipases are highly demanded industrial enzymes in various sectors such as food, pharmaceuticals, textiles, and detergents. Amylases are of ubiquitous occurrence and hold the maximum market share of enzyme sales. Lipases are the most versatile biocatalyst and bring about a range of bioconversion reactions such as hydrolysis, inter-esterification, esterification, alcoholysis, acidolysis, and aminolysis. The objective of this work was to study the feasibility for amylolitic and lipolytic production using a bacterium strain isolated from petroleum contaminated soil in the same submerged fermentation. This was a sequential process based on starch and vegetable oils feedstocks. Run were performed in batchwise using 2% starch supplemented with suitable nutrients and different vegetable oils as a lipase inducers. Fermentation conditions were pH 5.0; 30 degrees C, and stirred speed (200 rpm). Maxima activities for amyloglucosidase and lipase were, respectively, 0.18 and 1,150 U/ml. These results showed a promising methodology to obtain both enzymes using industrial waste resources containing vegetable oils.

Niobium hydrogenation process Effect of temperature and cooling rate from the hydrogenation temperature

High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes The present work aimed at the effect of temperature and cooling rate conditions on the niobium hydrogenation process using hydrogen gas The hydrogen contents of the materials were evaluated by weight change and chemical analysis X ray diffraction (XRD) was performed to identify and determine the lattice parameters of the formed hydride phases No hydrogenation took place under isothermal conditions only during cooling of the materials Significant hydrogenation occurred in the 500 C and 700 C experiments leading to the formation of a beta NbH(x) single phase material (C) 2010 Elsevier Ltd All rights reserved

Screening of lipases for the synthesis of xylitol monoesters by chemoenzymatic esterification and the potential of microwave and ultrasound irradiations to enhance the reaction rate

Lipases from different sources, Pseudomonas fluorescens (AK lipase), Burkholderia cepacia (PS lipase), Penicillium camembertii (lipase G) and Porcine pancreas lipase (PPL), previously immobilized on epoxy SiO(2)-PVA, were screened for the synthesis of xylitol monoesters by esterification of the protected xylitol using oleic acid as acyl donor group. Among all immobilized derivatives, the highest esterification yield was achieved by P. camembertii lipase, showing to be attractive alternative to bulk chemical routes to satisfy increasing commercial demands. Further experiments were performed to determine the influence of fatty acids chain size on the reaction yield and the feasibility of using non-conventional heating systems (microwave and ultrasound irradiations) to enhance the reaction rate. (C) 2010 Elsevier B.V. All rights reserved.