Influence of fixed electric charges on potential profile across the squid axon membrane

The potential profile for a model of squid axon membrane has been determined for two physiological states: resting and action states. The non-linear Poisson-Boltzmann equation has been solved by considering the volumetric charge densities due to charges dissolved in an electrolytic solution and fixed on both glycocalyx and cytoplasmatic proteins. Results showing the features of the potential profile along the outer electrolytic region are similar for both resting and action states. However, the potential fall along glycocalyx at action state is lower than at resting. A small variation in the Na+ concentration drastically affects the surface membrane potentials and vice versa. We conclude that effects on the potential profile due to surface lipidic bilayer charge and contiguous electric double layers are more relevant than those provoked by fixed charges distributed along the cell cytoplasm. (c) 2007 Elsevier B.V. All rights reserved.

Refined sandwich model for the vibration of beams with embedded shear piezoelectric actuators and sensors

This work extends a previously presented refined sandwich beam finite element (FE) model to vibration analysis, including dynamic piezoelectric actuation and sensing. The mechanical model is a refinement of the classical sandwich theory (CST), for which the core is modelled with a third-order shear deformation theory (TSDT). The FE model is developed considering, through the beam length, electrically: constant voltage for piezoelectric layers and quadratic third-order variable of the electric potential in the core, while meclianically: linear axial displacement, quadratic bending rotation of the core and cubic transverse displacement of the sandwich beam. Despite the refinement of mechanical and electric behaviours of the piezoelectric core, the model leads to the same number of degrees of freedom as the previous CST one due to a two-step static condensation of the internal dof (bending rotation and core electric potential third-order variable). The results obtained with the proposed FE model are compared to available numerical, analytical and experimental ones. Results confirm that the TSDT and the induced cubic electric potential yield an extra stiffness to the sandwich beam. (C) 2007 Elsevier Ltd. All rights reserved.

Investigation of the mass transfer processes during the desalination of water containing phenol and sodium chloride by electrodialysis

Oxidation processes are used in wastewater treatment when conventional processes are not effective due to the presence of recalcitrant organic contaminants, like phenol. However, the presence of ionic compounds associated with organic pollutants may retard the oxidation. In this work the transport of species contained in an aqueous solution of phenol containing sodium chloride was evaluated in an electrodialysis (ED) system. An experimental study was carried out in which the influence of the process variables on the phenol loss and sodium chloride removal was investigated. Experiments were also performed without current, in order to determine the phenol transfer due to diffusion. The phenol and salt concentration variations in the ED compartments were measured over time, using dedicated procedures and an experimental design to determine the global characteristic parameters. A phenomenological approach was used to relate the phenol, salt and water fluxes with the driving forces (concentration and electric potential gradients). Under ED conditions, two contributions were pointed out for the phenol transport, i.e. diffusion and convection, this latter coming from the water flux due to electroosmosis related to the migration of salts. The fitting of the parameters of the transport equations resulted in good agreement with the experimental results over the range of conditions investigated. (c) 2008 Elsevier B.V. All rights reserved.

Probing Individual Quantum Dots: Noise in Self-Assembled Systems

In this work we explore the noise characteristics in lithographically-defined two terminal devices containing self-assembled InAs/InP quantum dots. The experimental ensemble of InAs dots show random telegraph noise (RTN) with tuneable relative amplitude-up to 150%-in well defined temperature and source-drain applied voltage ranges. Our numerical simulation indicates that the RTN signature correlates with a very low number of quantum dots acting as effective charge storage centres in the structure for a given applied voltage. The modulation in relative amplitude variation can thus be associated to the altered electrostatic potential profile around such centres and enhanced carrier scattering provided by a charged dot.

Three-dimensional electrical impedance, tomography: A topology optimization approach

Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.

Chaotic transport in reversed shear tokamaks

For tokamak models using simplified geometries and reversed shear plasma profiles, we have numerically investigated how the onset of Lagrangian chaos at the plasma edge may affect the plasma confinement in two distinct but closely related problems. Firstly, we have considered the motion of particles in drift waves in the presence of an equilibrium radial electric field with shear. We have shown that the radial particle transport caused by this motion is selective in phase space, being determined by the resonant drift waves and depending on the parameters of both the resonant waves and the electric field profile. Moreover, we have shown that an additional transport barrier may be created at the plasma edge by increasing the electric field. In the second place, we have studied escape patterns and magnetic footprints of chaotic magnetic field lines in the region near a tokamak wall, when there are resonant modes due to the action of an ergodic magnetic limiter. A non-monotonic safety factor profile has been used in the analysis of field line topology in a region of negative magnetic shear. We have observed that, if internal modes are perturbed, the distributions of field line connection lengths and magnetic footprints exhibit spatially localized escape channels. For typical physical parameters of a fusion plasma, the two Lagrangian chaotic processes considered in this work can be effective in usual conditions so as to influence plasma confinement. The reversed shear effects discussed in this work may also contribute to evaluate the transport barrier relevance in advanced confinement scenarios in future tokamak experiments.

IS ORDINARY ELECTRIC DRILLS` VENTING PORT A POTENTIAL SOURCE OF SURGICAL INFECTION?

Objective: To evaluate the potential risk of surgical contamination by the venting port of ordinary electric drills (ED) employed in orthopaedic surgeries. Materials and Methods: an experimental laboratory, randomized study was developed to analyze EDs in surgical practice and new cleaned and sterilized equipment, which were contaminated with Bacillus atrophaeus spores at a concentration of 84 X 10(6) UFC. The air generated by the engine of each drill was collected and cultivated on sterile agar plates. Results: Positive culture was identified in two ED in surgical practice, as well as a positive culture to Bacillus atrophaeus with 1 CFU growth (1, 19 X 10(-8)). Conclusion: In the conditions of the experiment, the air generated by the venting port of the ED`s engine does not consist of a source of contamination for the surgical site.

Gene expression profile analysis of primary glioblastomas and non-neoplastic brain tissue: identification of potential target genes by oligonucleotide microarray and real-time quantitative PCR

The prognosis of glioblastomas is still extremely poor and the discovery of novel molecular therapeutic targets can be important to optimize treatment strategies. Gene expression analyses comparing normal and neoplastic tissues have been used to identify genes associated with tumorigenesis and potential therapeutic targets. We have used this approach to identify differentially expressed genes between primary glioblastomas and non-neoplastic brain tissues. We selected 20 overexpressed genes related to cell cycle, cellular movement and growth, proliferation and cell-to-cell signaling and analyzed their expression levels by real time quantitative PCR in cDNA obtained from microdissected fresh tumor tissue from 20 patients with primary glioblastomas and from 10 samples of non-neoplastic white matter tissue. The gene expression levels were significantly higher in glioblastomas than in non-neoplastic white matter in 18 out of 20 genes analyzed: P < 0.00001 for CDKN2C, CKS2, EEF1A1, EMP3, PDPN, BNIP2, CA12, CD34, CDC42EP4, PPIE, SNAI2, GDF15 and MMP23b; and NFIA (P: 0.0001), GPS1 (P: 0.0003), LAMA1 (P: 0.002), STIM1 (P: 0.006), and TASP1 (P: 0.01). Five of these genes are located in contiguous loci at 1p31-36 and 2 at 17q24-25 and 8 of them encode surface membrane proteins. PDPN and CD34 protein expression were evaluated by immunohistochemistry and they showed concordance with the PCR results. The present results indicate the presence of 18 overexpressed genes in human primary glioblastomas that may play a significant role in the pathogenesis of these tumors and that deserve further functional investigation as attractive candidates for new therapeutic targets.

Chemometric Studies on Natural Products as Potential Inhibitors of the NADH Oxidase from Trypanosoma cruzi Using the VolSurf Approach

Natural products have widespread biological activities, including inhibition of mitochondrial enzyme systems. Some of these activities, for example cytotoxicity, may be the result of alteration of cellular bioenergetics. Based on previous computer-aided drug design (CADD) studies and considering reported data on structure-activity relationships (SAR), an assumption regarding the mechanism of action of natural products against parasitic infections involves the NADH-oxidase inhibition. In this study, chemometric tools, such as: Principal Component Analysis (PCA), Consensus PCA (CPCA), and partial least squares regression (PLS), were applied to a set of forty natural compounds, acting as NADH-oxidase inhibitors. The calculations were performed using the VolSurf+ program. The formalisms employed generated good exploratory and predictive results. The independent variables or descriptors having a hydrophobic profile were strongly correlated to the biological data.

An AC-5 cathepsin B-like protease purified from Haemonchus contortus excretory secretory products shows protective antigen potential for lambs

The immunogenic properties of cysteine proteases obtained from excretory/secretory products (ES) of Haemonchus contortus were investigated with a fraction purified with a recombinant H. contortus cystatin affinity column. The enrichment of H. contortus ES for cysteine protease was confirmed with substrate SDS-PAGE gels since the cystatin-binding fraction activity was three times higher than total ES, despite representing only 3% of total ES. This activity was inhibited by a specific cysteine protease inhibitor (E64) and by recombinant cystatin. The one-dimensional profile of the cystatin-binding fraction displayed a single band with a molecular mass of 43 kDa. Mass spectrometry showed this to be AC-5, a cathepsin B-like cysteine protease which had not been identified in ES products of H. contortus before. The cystatin binding fraction was tested as an immunogen in lambs which were vaccinated three times (week 0, 2.5 and 5), challenged with 10 000 L3 H. contortus (week 6) before necropsy and compared to unvaccinated challenge controls and another group given total ES (n = 10 per group). The group vaccinated with cystatin-binding proteins showed 36% and 32% mean worm burden and eggs per gram of faeces (EPG) reductions, respectively, compared to the controls but total ES was almost without effect. After challenge the cystatin-binding proteins induced significantly higher local and systemic ES specific IgA and IgG responses.

THE EFFECT OF REFRIGERATED STORAGE ON SENSORY PROFILE AND PHYSICAL-CHEMICAL CHARACTERISTICS OF MINIMALLY PASTEURIZED ORANGE JUICE

Minimal pasteurization of orange juice (OJ) consists of using minimum holding time and temperature to ensure partial inactivation of pectin methylesterase (PME). This process produces juice with preserved sensory attributes and has a better acceptance by consumers when compared with commercially pasteurized OJ. Sensory profile and physical-chemical characteristics of minimally processed OJ was determined, during refrigerated storage, for two OJ blends with different pH values and the same level of PME thermal inactivation. A selected and trained sensorial panel (n = 16) performed sensory analysis, based on a quantitative descriptive analysis, twice a week for 30 days, evaluating the attributes of appearance (suspended particles and color intensity), odor (natural orange and fermented orange) and flavor (orange characteristic, fermented orange, acid and bitter taste). Storage presented great effect on OJ sensory profile; however, it was not noticeable on physical-chemical characteristics.

Estimating Amino Acid Requirement of Brazilian Freshwater Fish from Muscle Amino Acid Profile

Information on nutritional requirement of some Brazilian farmed fish species, especially essential amino acids (EAA) requirements, is scarce. The estimation of amino acids requirements based on amino acid composition of fish is a fast and reliable alternative. Matrinxa, Brycon amazonicus, and curimbata, Prochilodus lineatus, are two important Brazilian fish with potential for aquaculture. The objective of the present study was to estimate amino acid requirements of these species and analyze similarities among amino acid composition of different fish species by cluster analysis. To estimate amino acid requirement, the following formula was used: amino acid requirement = [(amount of an individual amino acid in fish muscle tissue) x (average totalEAA requirement among channel catfish, Ictalurus punctatus, Nile tilapia, Oreochromis niloticus, and common carp, Cyprinus carpio)]/(average fish muscle totalEAA). Most values found lie within the range of requirements determined for other omnivorous fish species, in exception of leucine requirement estimated for both species, and arginine requirement estimated for matrinxa alone. Rather than writing off the need for regular dose-response assays under the ideal protein concept to determine EAA requirements of curimbata and matrinxa, results set solid base for the study of tropical species dietary amino acids requirements.

Isolation of micropropagated strawberry endophytic bacteria and assessment of their potential for plant growth promotion

Twenty endophytic bacteria were isolated from the meristematic tissues of three varieties of strawberry cultivated in vitro, and further identified, by FAME profile, into the genera Bacillus and Sphingopyxis. The strains were also characterized according to indole acetic acid production, phosphate solubilization and potential for plant growth promotion. Results showed that 15 strains produced high levels of IAA and all 20 showed potential for solubilizing inorganic phosphate. Plant growth promotion evaluated under greenhouse conditions revealed the ability of the strains to enhance the root number, length and dry weight and also the leaf number, petiole length and dry weight of the aerial portion. Seven Bacillus spp. strains promoted root development and one strain of Sphingopyxis sp. promoted the development of plant shoots. The plant growth promotion showed to be correlated to IAA production and phosphate solubilization. The data also suggested that bacterial effects could potentially be harnessed to promote plant growth during seedling acclimatization in strawberry.

Bacterial communities and biogeochemical transformations of iron and sulfur in a high saltmarsh soil profile

Microbial community structure in saltmarsh soils is stratified by depth and availability of electron acceptors for respiration. However, the majority of the microbial species that are involved in the biogeochemical transformations of iron (Fe) and sulfur (S) in such environments are not known. Here we examined the structure of bacterial communities in a high saltmarsh soil profile and discuss their potential relationship with the geochemistry of Fe and S. Our data showed that the soil horizons Ag (oxic-suboxic), Bg (suboxic), Cri (anoxic with low concentration of pyrite Fe) and Cr-2 (anoxic with high concentrations of pyrite Fe) have distinct geochemical and microbiological characteristics. In general, total S concentration increased with depth and was correlated with the presence of pyrite Fe. Soluble + exchangable-Fe, pyrite Fe and acid volatile sulfide Fe concentrations also increased with depth, whereas ascorbate extractable-Fe concentrations decreased. The occurrence of reduced forms of Fe in the horizon Ag and oxidized Fe in horizon Cr-2 suggests that the typical redox zonation, common to several marine sediments, does not occur in the saltmarsh soil profile studied. Overall, the bacterial community structure in the horizon Ag and Cr-2 shared low levels of similarity, as compared to their adjacent horizons, Bg and Cr-1, respectively. The phylogenetic analyses of bacterial 16S rRNA gene sequences from clone libraries showed that the predominant phylotypes in horizon Ag were related to Alphaproteobacteria and Bacteroidetes. In contrast, the most abundant phylotypes in horizon Cr-2 were related to Deltaproteo-bacteria, Chloroflexi, Deferribacteres and Nitrospira. The high frequency of sequences with low levels of similarity to known bacterial species in horizons Ag and Cr-2 indicates that the bacterial communities in both horizons are dominated by novel bacterial species. (c) 2008 Elsevier Ltd. All rights reserved.

Potential of Ginkgo biloba L. leaves in the management of hyperglycemia and hypertension using in vitro models

Leaves from four different Ginkgo biloba L. trees (1 and 2 - females; 3 and 4 - males), grown at the same conditions, were collected during a period of 5 months (from June to October, 2007). Water and 12% ethanol extracts were analyzed for total phenolics content, antioxidant activity, phenolic profile, and the potential in vitro inhibitory effects on alpha-amylase, alpha-glucosidase, and Angiotensin I-Converting Enzyme (ACE) enzymes related to the management of diabetes and hypertension. The results indicated a significant difference among the trees in all functional benefits evaluated in the leaf extracts and also found important seasonal variation related to the same functional parameters. In general, the aqueous extracts had higher total phenolic content than the ethanolic extracts. Also, no correlation was found between total phenolics and antioxidant activity. In relation to the ACE inhibition, only ethanolic extracts had inhibitory activity. (C) 2009 Elsevier Ltd. All rights reserved.