Scaling properties of slow fracture in glass: from deterministic to irregular topography

In this work we discuss the morphology and self-affine properties of the slow-fracture surfaces of soda-lime glass obtained by a bending process under the effect of applied water vapor. The fractographic analysis showed the presence of secondary cracks in the mirror zone, whereas in the mist–hackle region step-like morphologies were observed and over them we found fine undulations. The self-affine analysis, performed by two methods, showed the existence of two different statistical distributions for the roughness exponent, ζ. At the beginning of the mirror zone ζ = 0.5, in the mist–hackle region we detected the same value for fine length scales, whereas at large length scales we observed ζ = 0.8. This scenario may be described by a qualitative model in which the deterministic mirror–mist–hackle pattern coexists with an irregular topography, the two observed regimes are thus characterized by two different roughness exponents, with the 0.5 value dominating at low-speed/fine-scales and the 0.8 value governing the high-speed/large-scales regimes.     

Purification and characterization of an extracellular trypsin-like protease of Fusarium oxysporum var. lini

An alkaline serineprotease, capable of hydrolyzing Nalpha-benzoyl- dl arginine p-nitroanilide, was secreted by Fusarium oxysporum var. lini grown in the presence of gelatin as the sole nitrogen and carbon source. The protease was purified 65-fold to electrophoretic homogenity from the culture supernatant in a three-step procedure comprising QSepharose chromatography, affinity chromatography, and FPLC on a MonoQ column. SDS-PAGE analysis of the purified protein indicated an estimated molecular mass of 41 kDa. The protease had optimum activity at a reaction temperature of 45 degrees C and showed a rapid decrease of activity at 48 degrees C. The optimum pH was around 8.0. Characterization of the protease showed that Ca2+ and Mg2+ cations increased the activity, which was not inhibited by EDTA or 1,10-phenanthroline. The enzyme activity on Nalpha-benzoyl-DL arginine p-nitroanilide was inhibited by 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride, p-aminobenzamidine dihydrochloride, aprotinin, 3-4 dichloroisocoumarin, and N-tosyl-L-lysine chloromethyl ketone. The enzyme is also inhibited by substrate concentrations higher than 2.5 x 10(-4)M. The protease had a Michaelis-Menten constant of 0.16 mM and a V(max) of 0.60 mumol released product.min(-1).mg(-1) enzyme when assayed in a non-inhibiting substrate concentration. The activity on Nalpha-benzoyl- dl arginine p-nitroanilide was competitively inhibited by p-aminobenzamidine dihydrochoride. A K(i) value of 0.04 mM was obtained.     

Antimicrobial, Antiproliferative and Proapoptotic Activities of Extract, Fractions and Isolated Compounds from the Stem of Erythroxylum caatingae Plowman

In the study, we have examined the antitumor and antimicrobial activities of the methanol extract, the fractions, a fraction of total alkaloids and two alkaloids isolated from the stem of Erythroxylum caatingae Plowman. All test fractions, except the hexane fractions, showed antimicrobial activity on gram-positive bacteria and fungi. The acetate: methanol (95:5), acetate, chloroform and hexane fractions show the highest cytotoxicity activity against the NCI-H292, HEp-2 and K562 cell lines using MTT. The absence of hemolysis in the erythrocytes of mice was observed in these fractions and 6β-Benzoyloxy-3α-(3,4,5- trimethoxybenzoyloxy) tropane (catuabine B). Staining with Annexin V-FITC and JC-1 was used to verify the mechanism of action of the compounds of E. caatingae that showed cytotoxicity less than 30 μg/mL in leukemic cells. After 48 h of incubation, we observed that the acetate: methanol (95:5), acetate, and chloroform fractions, as well as the catuabine B, increased in the number of cells in early apoptosis, from 53.0 to 74.8%. An analysis of the potential of the mitochondrial membrane by incorporation of JC-1 showed that most cells during incubation of the acetate: methanol (95:5) and acetate fractions (63.85 and 59.2%) were stained, suggesting the involvement of an intrinsic pathway of apoptosis.     

Initial power measurements for a family of novel vertical-wheel bioreactors

The purpose of this investigation was to develop an initial set of Power number versus Reynolds number results for a family of vertical-wheel bioreactors. These bioreactors are increasingly being used for the manufacture of cells for cell therapy but have not been characterized according to this approach. A novel gravimetric method to measure power was used, and the validity of this method was assessed by measuring power for a standard stirred tank bioreactor with a Rushton impeller. The results of the gravimetric method were found to closely match those derived from traditional methods. The validated method was then used to measure the power draw and develop an initial set of Power number versus Reynolds number results for a family of vertical-wheel bioreactors.     

Nanostructured membranes based on cellulose acetate obtained by electrospinning. Part II. Controlled release profile and microbiological behavior

Nanofiber membranes of cellulose acetate (CA) were produced with four mixtures of solvents, that is, acetic acid/water, acetone/water, dimethylacetamide (DMAc)/acetone, and DMAc/acetone/water, with the incorporation of the drug gentamicin sulfate at two concentrations. We evaluated the influence of the drug concentration in the electrospinning process. The best membrane produced in this stage was the membrane electrospun with the DMAc/acetone/water solvent mixture, whose process was shown to be viable and did not alter the membrane diameter or aspect with the variation of the drug concentration. Membranes prepared in this way and loaded with 50% of the drug were used for the studies of the release kinetics. Comparisons between the release profiles of the same membranes coated with hydroxypropyl methylcellulose, Eudragit L100, and electrospun CA nanofibers were carried out. The best results on the drug‐release profile were obtained with the membrane coated with nanofibers of CA, which caused a decrease of 9 h in the burst effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2772–2779, 2013     

Electrical conductivity of LTA‐zeolite in the presence of poly(vinyl alcohol) and poly(vinyl pyrrolidone) polymers

In this work we studied the electrical behavior of Linde type A zeolite (K⁺) in the presence of two polymers, poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP), with excellent film forming properties. Homogeneous composite thin films of PVA/LTA‐zeolite and PVP/LTA‐zeolite were prepared with different zeolite concentrations. The current?voltage (I?V) characteristics of the composites were measured at different applied voltages. The results show that the conductivity properties are composition‐ratio‐dependent and are also related to the type of polymers. Moreover, a well‐defined step‐like change was detected in the I?V curve of PVP/LTA‐zeolite at very high applied voltage. © 2013 Society of Chemical Industry     

Oxygen and carbon dioxide transport through high barrier polyester blends

The transport of oxygen and carbon dioxide through a set of random copolymer films based on poly(ethylene terephthalate) (PET) and poly(ethylene 2,6‐naphthalate) (PEN) were explored. Diffusivity and permeability of both gases decreased with increasing PEN content. The oxygen and carbon dioxide diffusion coefficients decreased 74 and 82% from pure PET to pure PEN, respectively. The presence of stiffer PEN moieties had an effect on the glass transition temperature (T_g) of PET/PEN blends and gas barrier. In the complete range of tested blends, the differential scanner calorimeter analysis displayed a single value of thermal glass transition temperature. As the PEN content was increased, the fractional free volume (FFV) and the diffusion coefficients of the blends were decreased. The Doolittle equation provided the best fit for diffusivity and FFV and showed that the gas transport behavior was better understood when it was taken into consideration the cohesive energy of blends. As the PEN content in films was increased, their rigidity and the glass/rubber transition temperature were increased, and their capacity to be penetrated by small molecules like O₂ and CO₂ was decreased. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

PLUG＆DRIVE^TM系列应用概况（二）——应用于电机驱动的集成功率模块

对于每个给高端IGBTs提供门极脉冲的三个高端电路，高端和低端驱动器IC需要一个浮动的电源供电。一个获得浮动电源的非常方便的方法是使用自举电路。下图说明了三相开关逆变器驱动电路的其中一相的实现方法。该电路适用于每一相。     

On higher order statistics of the Nakagami-m distribution

This paper proposes a fading model that leads to a formal, but simple method to obtain the exact formula of the Nakagami-m published in 1960 distribution for m=n/2, with n a nonzero integer number. Based on such a model, the joint distribution of the envelope and its time derivative are accomplished, and exact formulas for the level crossing rate (closed-form formula) and for the average fade duration are derived. Simulation curves and exact formulas are checked against each other and a very good agreement between them is attained. Although derived for discrete values of m (m being an integer multiple of 1/2), there are no mathematical constraints for these expressions to be used for any real value of m⩾1/2