Detection of the early stage of recombinational DNA repair by silicon nanowire transistors

A silicon nanowire-based biosensor has been designed and applied for label-free and ultrasensitive detection of the early stage of recombinational DNA repair by RecA protein. Silicon nanowires transistors were fabricated by atomic force microscopy nanolithography and integrated into a microfluidic environment. The sensor operates by measuring the changes in the resistance of the nanowire as the biomolecular reactions proceed. We show that the nanoelectronic sensor can detect and differentiate several steps in the binding of RecA to a single-stranded DNA filament taking place on the nanowire-aqueous interface. We report relative changes in the resistance of 3.5% which are related to the interaction of 250 RecA·single-stranded DNA complexes. Spectroscopy data confirm the presence of the protein-DNA complexes on the functionalized silicon surfaces.     

Severe hemorrhage because of delayed iliac vein rupture after dialysis catheter placement: Is it preventable?

Mechanical complications of femoral catheterization for hemodialysis include pseudoaneurysm, arteriovenous fistulae, neurological injury, and vessel perforation. With regard to the latter, severe hemorrhage is a rare but devastating and potentially fatal complication. We report the case of a 76-year-old female who underwent femoral catheterization for hemodialysis using ultrasound guidance. The first hemodialysis session was conducted without incident. Unfortunately, inadvertent injury and delayed perforation of the iliac vein resulted in severe hemorrhage and retroperitoneal hematoma. Surgical repair was performed. The patient was asymptomatic after the procedure and was discharged 15 days later. Based on this case and a review of the literature, we present mechanisms and ways to prevent this complication.     

Ceramic/metal biocidal nanocomposites for bone-related applications

Hydroxyapatite/silver nanocomposites have been designed and synthesized as an engineering material for biomedical applications. The hydroxyapatite matrix was synthesized by a sol-gel method and, subsequently, the Ag nanoparticles were deposited by heterogeneous precipitation followed by two different reduction routes: thermal or chemical. Both sets were studied and compared and, in all cases, the metal nanoparticles appear perfectly isolated and attached to the surface of the hydroxyapatite. The average metal particle size is below 10?nm, allowing an important contact surface between silver and the microorganisms. The antimicrobial behavior against common bacteria showed a high effectiveness, well above the commercial level, as well as against yeast, in the case of the chemically reduced sample. Due to the nanocomposite microstructure, only a negligible portion of metal was released to the lixiviated liquid after the biocide tests, minimizing the risk of toxicity. These nanocomposites offer a solution to the infections on the surface of implants, one of the main problems in reaching a suitable level of osseointegration.     

Single and mixed poloxamine micelles as nanocarriers for solubilization and sustained release of ethoxzolamide for topical glaucoma therapy

Polymeric micelles of single and mixed poloxamines (Tetronic) were evaluated regarding their ability to host the antiglaucoma agent ethoxzolamide (ETOX) for topical ocular application. Three highly hydrophilic varieties of poloxamine (T908, T1107 and T1307) and a medium hydrophilic variety (T904), possessing a similar number of propylene oxide units but different contents in ethylene oxide, were chosen for the study. The critical micellar concentration and the cloud point of mixed micelles in 0.9 per cent NaCl were slightly greater than the values predicted from the additive rule, suggesting that the co-micellization is hindered. Micellar size ranged between 17 and 120 nm and it was not altered after the loading of ETOX (2.7–11.5 mg drug g^–1 poloxamine). Drug solubilization ability ranked in the order: T904 (50-fold increase in the apparent solubility) > T1107 ≅ T1307 > T908. Mixed micelles showed an intermediate capability to host ETOX but a greater physical stability, maintaining almost 100 per cent drug solubilized after 28 days. Furthermore, the different structural features of poloxamines and their combination in mixed micelles enabled the tuning of drug release profiles, sustaining the release in the 1–5 days range. These findings together with promising hen''s egg test-chorioallantoic membrane biocompatibility tests make poloxamine micelles promising nanocarriers for carbonic anhydrase inhibitors in the treatment of glaucoma.     

Prediction of MOR and MOE of structural plywood board using an artificial neural network and comparison with a multivariate regression model

The structural application of plywood boards has increased considerably in recent years. In this context, determining plywood mechanical properties such as bending strength and modulus of elasticity through predictive models using more-easily obtained properties is a very useful tool for in-factory quality control. Artificial neural networks have demonstrated their high capacity for modelling complex relations between variables, considerably improving on results obtained through regression techniques. Four neural networks were developed to obtain these mechanical properties by determining board thickness, moisture content, specific gravity, bending strength and modulus of elasticity of test pieces of small dimensions. The results were compared with those of a regression model and in all cases the results of the present study were better.     

Constructal flow distributor as a bipolar plate for proton exchange membrane fuel cells

A plate-type constructal flow distributor is implemented as a gas distributor for a proton exchange membrane fuel cell. A 3D complete model is simulated using CFD techniques. The fuel cell model includes the gas flow channels, the gas diffusion layers and the membrane-electrode assembly (MEA). The governing equations for the mass and momentum transfer are solved including the pertinent source terms due to the electrochemical reactions in the different zones of the fuel cell. Three constructal flow configurations were studied; each pattern is a fractal expansion of the original design, therefore, the only difference between them is the number of branches in the geometry. It was found that the number of branches is the key parameter in the performance of a fuel cell when using the constructal distributors as flow channels. The performance of the fuel cell is reported in I-V curves, power curves, and overpotential curves in order to determine which irreversibility is the main cause of energy losses. In terms of flow analysis, it was found that the constructal flow distributor presents a low pressure drop for a wide range of Reynolds number conditions at the inlet, as well as an excellent uniformity of flow distribution. Regardless of the outstanding hydrodynamic performance of the constructal distributors and the large current density values obtained, the implementation of these designs as flow patterns for PEMFCs need further optimization; first, the manufacturing of the plates have to be addressed in an efficient way; and secondly, the application in stacks will require an elaborate design to accomplish this task.     

Electrooxidation of H2/CO on carbon-supported PtRu-MoOx nanoparticles for polymer electrolyte fuel cells

Ternary PtRu-MoO_x catalysts with various Mo compositions have been investigated as anode electrocatalytic materials for a polymer electrolyte fuel cell fed with H₂/CO mixtures. Electrocatalysts have been prepared using a highly reproducible two step method, which allowed good control over the composition and particle size. All the prepared catalysts record a total metal loading close to 30 wt%, and a Mo load of 0, 1 and 3 wt%, supported on carbon Vulcan XC-72R, keeping the Pt/Ru atomic ratio constant. The incorporation of different amounts of Mo over the PtRu system does not modify structural characteristics such as particle size and crystal phases. However, the surface composition depends largely on the amount of Mo. An increase in the Mo loading to 3 wt% resulted in a decrease of the Pt surface area. The in situ FTIR technique has been used to investigate the CO oxidation process. The extent of CO poisoning was found to be lower for the trimetallic catalysts than for the binary catalyst at a potential below 0.25 V. The fuel cell performance was evaluated at 80 °C in a PEMFC fed with H₂/CO (10 ppm). Polarization curves for the catalysts show that activity depends heavily on composition, with catalysts with a small amount of Mo (1 wt%) displaying the highest CO tolerance. An increase in Mo loading (3 wt%) decreases activity of the PtRuMo, although it also reduces CO poisoning. The presence of Mo⁵⁺ species must be crucial for reducing the saturation coverage of irreversibly adsorbed CO on Pt surface atoms at very low potentials. However, the surface metal ratio of Pt/Mo (wt%) must be higher than 4, in order to keep the enough surface bare platinum sites, which are required for the dissociative adsorption of molecular H₂.     

Identity fusion and self-sacrifice: Arousal as a catalyst of pro-group fighting, dying, and helping behavior.

Identity fusion is a feeling of oneness with the group that induces people to tether their feelings of personal agency to the group. We accordingly proposed that increasing the agency of fused persons by elevating autonomic arousal would amplify their tendency to endorse and actually enact pro-ingroup behavior. In 4 experiments, increasing autonomic arousal through physical exercise elevated heart rates and fusion-unrelated activity among all participants. Fused participants, however, uniquely responded to arousal by translating elevated agency into endorsement of pro-group activity. These effects emerged both for endorsement of extreme behaviors for the group and for overt behaviors, specifically helping behavior (donating money to needy in-group members), and the speed with which participants raced a fusion-related avatar. The effects also generalized across 3 different arousal inductions (dodgeball, wind sprints, and Exercycle). Finally, fusion-related agency partially mediated the interactive effects of fusion and arousal on pro-group behavior. Apparently, autonomic arousal increases agency and identity fusion channels increased agency into pro-group behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)