Simple reconstitution of protein pores in nano lipid bilayers

We developed a new, simple and robust approach for rapid screening of single molecule interactions with protein channels. Our glass nanopipets can be fabricated simply by drawing glass capillaries in a standard pipet puller, in a matter of minutes, and do not require further modification before use. Giant unilamellar vesicles break when in contact with the tip of the glass pipet and form a supported bilayer with typical seal resistances of ～140 GΩ, which is stable for hours and at applied potentials up to 900 mV. Bilayers can be formed, broken, and re-formed more than 50 times using the same pipet enabling rapid screening of bilayers for single protein channels. The stability of the lipid bilayer is significantly superior to that of traditionally built bilayers supported by Teflon membranes, particularly against perturbation by electrical and mechanical forces. We demonstrate the functional reconstitution of the E. coli porin OmpF and α-hemolysin in a glass nanopipet supported bilayer. Interactions of the antibiotic enrofloxacin with the OmpF channel have been studied at the single-molecule level, demonstrating the ability of this method to detect single molecule interactions with protein channels. High-resolution conductance measurements of protein channels can be performed with low sample and buffer consumption. Glass nanopipet supported bilayers are uniquely suited for single-molecule studies as they are more rigid and the lifetime of a stable membrane is on the scale of hours, closer to that of natural cell membranes.     

Investigations of the unsteady diffusion process in microchannels

This paper is concerned with the investigations and modeling of the unsteady diffusion process along a straight micro-channel with a cross section of 380 μm×360 μm. The studied process is characterized by small Reynolds numbers (Re<10) and high Péclet number (Pe>1000). The 3D computations of the coupled momentum and diffusion equations for isochoric motions are performed with the FLUENT code using the unsteady solvers for both equations. In the limit of stationary solutions, the numerical results are validated by direct flow visualizations and experimental data using confocal microscopy. The computed distributions of concentration provide qualitative and quantitative information on the transitory diffusion process and the rate of solute spreading within the investigated geometry. In particular, the pattern of the “butterfly effect” is represented and analyzed during the non-stationary dynamical process. The work is relevant for the design of novel microfluidics applications where the control of diffusion processes at the walls are important (absorption, extraction, capture of molecules or nano-particles).     

Algorithms for Using Some Models of Gel and Glass Effects in Free-Radical Polymerization of Methyl Methacrylate

The aim of this article is the modeling and simulation of the batch bulk polymerization of methyl methacrylate (MMA). Simple dependencies between the propagation and termination rate constants and monomer conversion for the gel and glass effects are proposed. The empirical parameters in these relations are determined from conversion and molecular-weight experimental data obtained under various reaction conditions (initiator concentration and temperature). Sometimes, different relations were necessary to express the variation of the kinetic constants on conversion subintervals. Thus, these models have been used continuously or discontinuously, as a function of their results. An algorithm for using this model was also established.

The analysis of this model has two aims: (1) to get a good agreement between simulation and experiment; (2) to provide a simple model to be used under different reactor conditions (batch, semibatch, or continuous) or which can be easily handled in polymer engineering studies, such as sensitivity analysis, optimal control, and so forth.     

Formation of Aluminide Coatings by a Low Temperature FBCVD Process

The formation of aluminide coatings on Ni, Inconel 738, NiCr23Fe, SS304 and ARMCO Fe by a Fluidised Bed Chemical Vapour Deposition (FBCVD) process at low temperatures (550‐650°C) was studied. Aluminium powder and a HCl activator were used to form precursor halide vapours of Al. This led to the aluminide coating formation on the substrate's surface. The examination of the treated samples by means of optical microscopy and SEM/EDX indicated the deposition of dense and homogeneous coatings over the entire surface even for small treatment times. Coating thickness growth and coating morphology were evaluated for various treatment times and temperatures. The low temperature process has advantages compared to the high temperature process since the mechanical properties of the treated parts are not affected, although the coating thicknesses achieved are smaller.     

Stimulus configuration, occasion setting and the hippocampus.

N. A. Schmajuk, J. Lamoureux, and P. C. Holland (in press) showed that an extension of a neural network model introduced by N. A. Schmajuk and J. J. DiCarlo (1992) characterizes many of the differences between simple conditioning and occasion setting. In the framework of this model, it is proposed that the hippocampus modulates (a) the competition among simple and complex stimuli to establish associations with the unconditioned stimulus, and (b) the configuration of simple stimuli into complex stimuli. Under the assumptions that (a) nonselective lesions of the hippocampal formation impair both configuration and competition, and (b) selective lesions of the hippocampus proper impair only stimulus configuration, the model correctly describes the effects of these lesions on paradigms in which stimuli act as occasion setters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nanocomposites based on MWCNT and polystyrene,styrene‐acrylonitrile copolymer,or polymethylmethacrylate,obtained by miniemulsion polymerization

Free radical miniemulsion polymerization of styrene (St), St/acrylonitrile 3 : 1 mixture or methylmethacrylate in the presence of multiwalled carbon nanotubes (MWCNT) was proven as a convenient way to obtain homogenous hybrids with perspectives in associated applications like foams specialties materials. Miniemulsion polymerization was viable up to 2% wt. MWCNT to monomer, without agglomerations. The grafting on MWCNT during the polymerization occurs without the need for supplementary functionalization and the polymer grafted nanotubes showed stable dispersions in the polymer solvent. Monomer polarity affected the grafting ability during the polymerization process. The nanocomposites obtained after purification and drying were used in foaming process. MWCNT presence in the related nanocomposites decreased the pore sizes in foam‐like materials (for all three different matrices). At 1 wt % MWCNT content, low density (< 0.3 g/cm³), low pore size (< 10 μm) and high cell density (>10⁹ cell/cm³) were achieved. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41148.     

Preparation of lignin nanoparticles by chemical modification

Lignin is the main natural aromatic polymer and consists of about a quarter of lignocellulosic biomass. That is why products obtained from lignin are very attractive research topics, but it is also a very complex issue due to its complicated structure which depends on the separation method and plant species. To become a widely used raw material, the basic characteristics and structure-dependent properties must be elucidated, initially. For this reason, it is necessary to obtain lignin with superior properties, to be able to compete with fossil resources. This paper presents a chemical method to modify lignin by hydroxymethylation to obtain nanoparticles. Nanotechnology allows using chemical, physical and biological effects that do not occur outside the nanoscale world. To find the best conditions (from the average particle size distribution point of view), three reaction parameters were varied: ratio of lignin/aldehyde, pH and temperature. The following output value has been the average particle size distribution. The obtained data were processed with software in demo version (Modde 9) and resulted regression equation allows us to establish the optimum conditions. At the same time, the reaction products thus synthesized were characterized by FTIR spectroscopy, GPC, and ³¹PNMR spectroscopy. The results confirm that using this reaction, it is possible to synthesize nanoparticles from hydroxymethylated lignin. Lignin derivatives containing high hydroxyl group content have a potential utilization as phenol substitute in the phenol formaldehyde resin synthesis, composites, biocides, etc.     

Optimum allocation of computer spares for three-level stocks

This paper presents a model for determining the optimum stock in a three level depots system. The method for determining stock levels uses “incremental performance per price algorithm” (IPPA) and the “new Lawler-Bell algorithm” (NLB). The practical calculation is carried out on a computer, the results being presented in the form of a list of necessary spare units from the first to the third level.     

The pattern of responding in the peak-interval procedure with gaps: An individual-trials analysis.

Humans and lower animals time as if using a stopwatch that can be “stopped” or “reset” on command. This view is challenged by data from the peak-interval procedure with gaps: Unexpected retention intervals (gaps) delay the response function in a seemingly continuous fashion, from stop to reset. We evaluated whether these results are an artifact of averaging over trials, or whether subjects use discrete alternatives or a continuum of alternatives in individual-trials: A Probability-of-Reset hypothesis proposes that in individual gap trials subjects stochastically use discrete alternatives (stop/reset), such that when averaged over trials, the response distribution in gap trials falls in between “stop” and “reset.” Alternatively, a Resource Allocation hypothesis proposes that during individual gap trials working memory for the pregap duration decays, such that the response function in individual gap trials is shifted rightward in a continuous fashion. Both hypotheses provided very good fits with the observed individual-trial distributions, although the Resource Allocation hypothesis generated reliably better fits. Results provide support for the usefulness of individual-trial analyses in dissociating theoretical alternatives in interval timing tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)