A DC-DC converter based on the three-state switching cell for high current and voltage step-down applications

This paper presents a pulsewidth modulation dc-dc nonisolated buck converter using the three-state switching cell, constituted by two active switches, two diodes, and two coupled inductors. Only part of the load power is processed by the active switches, reducing the peak current through the switches to half of the load current, as higher power levels can then be achieved by the proposed topology. The volume of reactive elements, i.e., inductors and capacitors, is also decreased since the ripple frequency of the output voltage is twice the switching frequency. Due to the intrinsic characteristics of the topology, total losses are distributed among all semiconductors. Another advantage of this converter is the reduced region for discontinuous conduction mode when compared to the conventional buck converter or, in other words, the operation range in continuous conduction mode is increased, as demonstrated by the static gain plot. The theoretical approach is detailed through qualitative and quantitative analyses by the application of the three-state switching cell to the buck converter operating in nonoverlapping mode $(D < 0.5)$. Besides, the mathematical analysis and development of an experimental prototype rated at 1 kW are carried out. The main experimental results are presented and adequately discussed to clearly identify its claimed advantages. © 1986-2012 IEEE.

Lack of protective effects of zinc gluconate against rat colon carcinogenesis

Zinc has been proposed as a promising chemopreventive candidate against colon cancer. However, few studies on the potential beneficial effects of this trace element on cancer chemoprevention are available. The present study was designed to investigate the potential modifying influence of zinc gluconate (ZnGly) on the initiation step of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH). Male Wistar rats received orally ZnGly (15 mg elemental zinc/kg, 3 times per wk) 2 wk before and during DMH treatment (3 × 40 mg/kg, once a wk). The animals were euthanized at the end of 4th and 16th wk. Colons were analyzed for aberrant crypt foci (ACF) and tumor development. Blood and colon zinc levels, cell proliferation, and apoptosis indexes in colonic crypts were analyzed 24 h after the last DMH administration. Oral treatment with ZnGly did neither alter the number of ACF nor the indexes of cell proliferation and apoptosis in the colonic mucosa. The incidence and multiplicity of colon tumors induced by DMH and their histopathological patterns were not modified by previous treatment with ZnGly. These findings indicate a lack of chemopreventive action of zinc gluconate supplementation on the initiation step of rat colon carcinogenesis induced by DMH. © 2013 Copyright Taylor and Francis Group, LLC.

Açai (Euterpe oleracea Mart.) feeding attenuates dimethylhydrazine-induced rat colon carcinogenesis

This study investigated the protective effect of spray-dried açaí powder (AP) intake on colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) in male Wistar rats. After 4. weeks of DMH administrations, the groups were fed with standard diet, a diet containing 2.5% or 5.0% AP or a diet containing 0.2% N-acetylcysteine (NAC) for 10. weeks, using aberrant crypt foci (ACF) as the endpoint. Additionally, two groups were fed with standard diet or a diet containing 5.0% AP for 20. weeks, using colon tumors as the endpoint. In ACF assay, a reduction in the number of aberrant crypts (ACs) and ACF (1-3 AC) were observed in the groups fed with 5.0% AP (37% AC and 47% ACF inhibition, p=. 0.036) and 0.2% NAC (39% AC and 41% ACF inhibition, p=. 0.042). In tumor assay, a reduction in the number of invasive tumors (p<. 0.005) and tumor multiplicity (p=. 0.001) was observed in the group fed with 5.0% AP. Also, a reduction in tumor Ki-67 cell proliferation (p=. 0.003) and net growth index (p=. 0.001) was observed in the group fed with 5.0% AP. Therefore the findings of this study indicate that AP feeding may reduce the development of chemically-induced rat colon carcinogenesis. © 2013 Elsevier Ltd.

LED light attenuation through human dentin: A first step toward pulp photobiomodulation after cavity preparation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

One step forward: contrasting the effects of Toe clipping and PIT tagging on frog survival and recapture probability

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Phase space properties and chaotic transport for a particle moving in a time dependent step potential well

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

eIF5A and EF-P: two unique translation factors are now traveling the same road

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reliability of peak O-2 uptake and O-2 uptake kinetics in step exercise tests in healthy subjects

To date little is known about the reliability of peak oxygen consumption (VO2pEAK) in incremental metronome paced step tests (1ST) and the reliability of on-kinetics VO2 has never been studied. We aimed to study the reliability of both tests. Eleven healthy subjects performed two ISTs until exhaustion. On two different days two duplicate 4 min constant metronome paced step tests (CST) were performed. VO2PEAK, mean response time (MRT) and phase II time constant (tau) were tested for reproducibility using the paired t-tests, in addition to the limits of agreement (LOA) and within subject coefficient of variation (COV). With a 95% LOA of 0.38 to 0.26 L min(-1), -8.7 to 9.1 s and -9.9 to 10.5 s they exhibit a COV of 3%, 4.5% and 6.9% for VO2PEAK, MRT and tau respectively. ST are sufficiently reliable for maximal and submaximal aerobic power assessments in healthy subjects and new studies of oxygen uptake kinetics in selected patient groups are warranted. (C) 2014 Elsevier B.V. All rights reserved.

Computer graphics applied to anatomy: a study of two bio-cad modeling methods on finite element analysis of human edentulous hemi-mandible

Modeling is a step to perform a finite element analysis. Different methods of model construction are reported in literature, as the Bio-CAD modeling. The purpose of this study was to perform a model evaluation and application using two methods of Bio-CAD modeling from human edentulous hemi-mandible on the finite element analysis. From CT scans of dried human skull was reconstructed a stereolithographic model. Two methods of modeling were performed: STL conversion approach (Model 1) associated to STL simplification and reverse engineering approach (Model 2). For finite element analysis was used the action of lateral pterygoid muscle as loading condition to assess total displacement (D), equivalent von-Mises stress (VM) and maximum principal stress (MP). Two models presented differences on the geometry regarding surface number (1834 (model 1); 282 (model 2)). Were observed differences in finite element mesh regarding element number (30428 nodes/16683 elements (model 1); 15801 nodes/8410 elements (model 2). D, VM and MP stress areas presented similar distribution in two models. The values were different regarding maximum and minimum values of D (ranging 0-0.511 mm (model 1) and 0-0.544 mm (model 2), VM stress (6.36E-04-11.4 MPa (model 1) and 2.15E-04-14.7 MPa (model 2) and MP stress (-1.43-9.14 MPa (model 1) and -1.2-11.6 MPa (model 2). From two methods of Bio-CAD modeling, the reverse engineering presented better anatomical representation compared to the STL conversion approach. The models presented differences in the finite element mesh, total displacement and stress distribution.

Natural killer activity in a medium-term multi-organ bioassay for carcinogenesis

Natural killer (NK) cell activity was evaluated after the initiation and promotion steps in a medium-term multi-organ bioassay for carcinogenesis. NK cell activity was assessed in vitro by Cr51 release assay at the 4th and 30th weeks of the experiment. Male Wistar rats were sequentially initiated with N-diethylnitrosamine (DEN i.p.), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN drinking water), N-methyl-N-nitrosourea (MNU i.p.), dihydroxy-di-N-propylnitrosamine (DHPN drinking water) and N,N'-dimethylhydrazine (DMH s.c.) at subcarcinogenic doses for 4 weeks (DMBDD initiation). One group was evaluated at the 4th week and the other was maintained without any further treatment until the 30th week. Two initiated groups were exposed through the diet to 2-acetylaminofluorene (2-AAF) or phenobarbital (PB), from the 6th until the 30th week. Five additional groups were studied to evaluate the effects of each initiator on NK activity. All groups submitted to initiation only, initiation plus promotion, or promotion only, developed significantly more preneoplastic lesions than the untreated control group. The main target organs for tumor development in the initiated animals were the liver and the colon, irrespective of treatment with 2-AAF or PB. NK cell activity was not affected by exposure to genotoxic carcinogens after initiation, at the 4th week. Treatments only with PB or 2-AAF did not change NK cell activity. However, decreased NK cell activity was registered in the group only initiated with DMBDD and in the group given DMBDD+2-AAF. This late depression of NK cell activity at the 30th week could be related to the production of suppressing molecules by the tumor cells.

Multi-step adhesive cementation versus one-step adhesive cementation: push-out bond strength between fiber post and root dentin before and after mechanical cycling

This study evaluated the effects of mechanical cycling on resin push-out bond strength to root dentin, using two strategies for fiber post cementation. Forty bovine roots were embedded in acrylic resin after root canal preparation using a custom drill of the fiber post system. The fiber posts were cemented into root canals using two different strategies (N = 20): a conventional adhesive approach using a three-step etch-and-rinse adhesive system combined with a conventional resin cement (ScotchBond Multi Purpose Plus + RelyX ARC ), or a simplified adhesive approach using a self-adhesive resin cement (RelyX U100). The core was built up with composite resin and half of the specimens from each cementation strategy were submitted to mechanical cycling (45 degree angle; 37 degrees C; 88 N; 4 Hz; 700,000 cycles). Each specimen was cross-sectioned and the disk specimens were pushed-out. The means from every group (n = 10) were statistically analyzed using a two-way ANOVA and a Tukey test (P = 0.05). The cementation strategy affected the push-out results (P < 0.001), while mechanical cycling did not (P = 0.3716). The simplified approach (a self-adhesive resin cement) had better bond performance despite the conditioning. The self-adhesive resin cement appears to be a good option for post cementation. Further trials are needed to confirm these results.

Extraction of natural red colorants from the fermented broth of Penicillium purpurogenum using aqueous two-phase polymer systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Plasmid DNA partitioning and separation using poly(ethylene glycol)/poly(acrylate)/salt aqueous two-phase systems

Phase diagrams of poly(ethylene glycol)/polyacrylate/Na2SO4 systems have been investigated with respect to polymer size and pH. Plasmid DNA from Escherichia coil can depending on pH and polymer molecular weight be directed to a poly(ethylene glycol) or to a polyacrylate-rich phase in an aqueous two-phase system formed by these polymers. Bovine serum albumin (BSA) and E. coil homogenate proteins can be directed opposite to the plasmid partitioning in these systems. Two bioseparation processes have been developed where in the final step the pDNA is partitioned to a salt-rich phase giving a total process yield of 60-70%. In one of them the pDNA is partitioned between the polyacrylate and PEG-phases in order to remove proteins. In a more simplified process the plasmid is partitioned to a PEG-phase and back-extracted into a Na2SO4-rich phase. The novel polyacrylate/PEG system allows a strong change of the partitioning between the phases with relatively small changes in composition or pH. (C) 2012 Elsevier B.V. All rights reserved.

Solid-phase microextraction combined with comprehensive two-dimensional gas chromatography for fatty acid profiling of cell wall phospholipids

The combination of solid-phase microextraction (SPME) with comprehensive two-dimensional gas chromatography is evaluated here for fatty acid (FA) profiling of the glycerophospholipid fraction from human buccal mucosal cells. A base-catalyzed derivatization reaction selective for polar lipids such as glycerophospholipid was adopted. SPME is compared to a miniaturized liquidliquid extraction procedure for the isolation of FA methyl esters produced in the derivatization step. The limits of detection and limits of quantitation were calculated for each sample preparation method. Because of its lower values of limits of detection and quantitation, SPME was adopted. The extracted analytes were separated, detected, and quantified by comprehensive two-dimensional gas chromatography with flame ionization detection (FID). The combination of SPME and comprehensive two-dimensional gas chromatography with FID, using a selective derivatization reaction in the preliminary steps, proved to be a simple and fast procedure for FA profiling, and was successfully applied to the analysis of adult human buccal mucosal cells.

The revision of the Brazilian Forest Act: increased deforestation or a historic step towards balancing agricultural development and nature conservation?

Almost two-thirds of the Brazilian territory still has prevalence of natural vegetation. Although not all pristine, much of these areas have high conservation value. 170 million hectare (Mha) of the natural vegetation is located within Federal and State protected areas. Most of the remaining 367 Mha is on private agriculture lands, where the Forest Act is the most important legal framework for conservation. In July 2010, the Brazilian parliament began the analysis of a substitutive legislation for the Forest Act. The main motivations for the revision is that, on the one hand, it has been found ineffective in protecting natural vegetation, and on the other hand, it is perceived as a barrier against development in the agriculture sector. The substitutive Forest Act, as it presently stands, does not represent a balance between existing standpoints and objectives; it may drive development towards either more private protection through market-driven compensation actions, or increased deforestation and less nature protection/restoration. This article uses outcomes from modeling analyses to discuss weaknesses of the substitutive Forest Act and to suggest possible improvements. (C) 2011 Elsevier Ltd. All rights reserved.