Biomimetic model of the outer plexiform layer by incorporating memristive devices.

In this paper we present a biorealistic model for the first part of the early vision of processing by incorporating memristive nanodevices. The architecture of the proposed network is based on the organization and functioning of the outer plexiform layer (OPL) in the vertebrate retina. We demonstrate that memristive devices are indeed a valuable building block for neuromorphic architectures, as their highly nonlinear and adaptive response could be exploited for establishing ultradense networks with dynamics similar to that of their biological counterparts. We particularly show that hexagonal memristive grids can be employed for faithfully emulating the smoothing effect occurring in the OPL to enhance the dynamic range of the system. In addition, we employ a memristor-based thresholding scheme for detecting the edges of grayscale images, while the proposed system is also evaluated for its adaptation and fault tolerance capacity against different light or noise conditions as well as its distinct device yields.

Distinct hydration properties of wild-type and familial point mutant A53T of α-synuclein associated with Parkinson's disease.

The propensity of α-synuclein to form amyloid plays an important role in Parkinson's disease. Three familial mutations, A30P, E46K, and A53T, correlate with Parkinson's disease. Therefore, unraveling the structural effects of these mutations has basic implications in understanding the molecular basis of the disease. Here, we address this issue through comparing details of the hydration of wild-type α-synuclein and its A53T mutant by a combination of wide-line NMR, differential scanning calorimetry, and molecular dynamics simulations. All three approaches suggest a hydrate shell compatible with a largely disordered state of both proteins. Its fine details, however, are different, with the mutant displaying a somewhat higher level of hydration, suggesting a bias to more open structures, favorable for protein-protein interactions leading to amyloid formation. These differences disappear in the amyloid state, suggesting basically the same surface topology, irrespective of the initial monomeric state.

Potential application of Metolose in a thermoresponsive transdermal therapeutic system.

The purpose of the present study was to formulate a novel thermoresponsive membrane controlled therapeutic system from Metolose for possible transdermal application. Metolose gel shows thermal gelation property, which can be characterized by two (T(1), T(2)) temperatures. A sharp decrease of viscosity can be measured at T(1), but gelation can be observed at T(2). Different types of Metolose polymers were compared considering their thermoresponsive behaviour. Only thermal gelation was observed in the case of Metolose SM, while Metolose SH showed a sudden decrease of viscosity at T(1). Since this temperature is above the body temperature, so it should be shifted to the skin temperature in case of possible transdermal application. Modulation of thermoresponsibility was followed by rheological method, and the thermoresponsive drug release from Metolose gel was studied by static liberation test. Our results demonstrated that the effect of different salts (NaCl, NaHCO(3), KCl) of various concentrations in Metolose SH gel reduced T(1) to the skin temperature, which enabled enhanced drug release.

The seasonal changes in the concentration of polycyclic aromatic hydrocarbons in precipitation and aerosol near Lake Balaton, Hungary.

The concentration of polycyclic aromatic hydrocarbons (PAHs) in atmospheric precipitation and aerosol samples was monitored in a rural site by Lake Balaton, Hungary to examine the seasonal variation. The seasonal mean concentration of individual 3-6-ring PAHs in precipitation varied from 1 to 54 ng l-1 and from 3 to 350 ng l-1 in summer and winter, respectively. In the atmospheric aerosol samples the seasonal mean concentration of PAHs varied from 4 to 880 pg m-3, from 4 to 300 pg m-3, from 11 to 1050 pg m-3 and from 36 to 5000 pg m-3 in spring, summer, autumn and winter, respectively. Wet (412 micrograms m-2 year-1) and aerosol (190-300 micrograms m2 year-1) deposition rates were also estimated indicating that the two processes are of comparable importance in the removal of 3-6-ring PAHs from the atmosphere.

Theoretical approach to non-constant uptake rates for tube-type diffusive samplers.

A simple theoretical model was developed for evaluating the validity of the simplified uptake model of diffusive sampling. In the model based on the plate theory diffusion to the adsorbent surface, phase equilibrium of the adsorbate and mass transport in the adsorbent bed were considered. It was found that in the early stage of sampling, the rate of sampling is close to its theoretical value. As sampling progresses, the concentration increases and the mass transfer front gradually moves into the adsorbent layer. Above a certain threshold limit, the mass uptake becomes a steady state process in which the diffusion in the air gap and the mass transport in the adsorbent bed are balanced. As uptake is a cumulative process, sampling should continue long enough to render the effects of these initial changes negligible. That is why constant uptake rates can still be obtained above a critical exposure dose. This critical exposure dose should be exceeded both in the determination of uptake rates and outdoor measurements, to obtain consistent and reliable analytical data. Evaluation of the time and concentration dependence of uptake rate in laboratory experiments and the time dependence of uptake rate in filed test was performed to justify the model results. Since the determination of uptake rates always takes places in the laboratory, where the exposure time is much shorter and the concentration is much higher than in the environment, the uptake rates are thus overestimated by 10-30%. Therefore, the uptake rates should be determined in the field under ambient conditions by means of an independent reference method.

Isolation of water-soluble organic matter from atmospheric aerosol.

The development of a solid phase extraction (SPE) method is presented, which is capable of isolating approx. 60% of the water-soluble organic compounds from aerosol samples. The aqueous extracts of the filter samples were acidified then passed through an SPE column. Four silica-based and two polymeric reversed phase columns were tested and similar recoveries of the organic carbon were found. The isolated organic matter was nearly free from inorganic ions, which are major constituents of atmospheric aerosol. This fraction accounted for a major part of the UV absorption above 250 nm and fluorescence activity of the aerosol extract. The precision of the method was tested by performing three parallel sample preparations with Oasis HLB columns. It was found that the relative standard deviation of the carbon content of the isolated organic matter was better than 7%, which indicated the reliability of the method. In the atmospheric aerosol research the newly developed sample preparation method facilitates the physical and chemical characterisation of water-soluble organic compounds without the interference of inorganic constituents.

Electrokinetic injection in capillary electrophoresis and its application to the analysis of inorganic compounds.

In capillary electrophoresis, electrokinetic injection is a highly controversial sampling technique. It is a simple mode of sample introduction which is suitable for on-line preconcentration of the analytes, but its precision and accuracy are more strongly affected by experimental conditions compared to hydrodynamic injection. In the first part of this paper the features of electrokinetic and hydrodynamic injections are compared, followed by a detailed discussion on the different biases of electrokinetic injection and on how to reduce them. Finally, applications of the electrokinetic injection are reviewed with special emphasis on the analysis of inorganic compounds.

Sample preparation of atmospheric aerosol for the determination of carbonyl compounds.

Sample preparation including sonication and solid phase extraction has been developed for the determination of carbonyl compounds in atmospheric aerosol. Aerosol samples were sonicated in acidified acetonitrile containing 2,4-dinitrophenylhydrazine (DNPH) to form hydrazone derivatives of aldehydes and ketones. Water was added to the extract to increase its polarity. Then the solution was passed through an octadecyl or phenyl solid phase extraction cartridge. The concentrated hydrazone derivatives were eluted with tetrahydrofuran, the eluate was evaporated to dryness then dissolved in acetonitrile/water mixture and finally analysed by RP-HPLC with UV detection at 360 nm. The absolute detection limits of the individual carbonyl compounds range from 0.4 to 5.8 ng.

The evaluation of a tenax GR diffusive sampler for the determination of benzene and other volatile aromatics in outdoor air.

The applicability of a tube-type diffusive sampler as an environmental monitor for benzene, toluene, ethylbenzene and xylene (BTEX) is reported. Uptake rates have been experimentally determined for a novel type adsorbent, Tenax GR, and compared to theoretical values. It is shown, that the uptake rates are virtually independent of environmental parameters within the experimental conditions studied. The response of the sampler to transient changes in concentrations has been determined in the laboratory. It is found that the sampler is capable of following an extreme concentration profile. Field comparisons with pumped samplers have been performed and good agreement is observed between the results of the two independent methods. The samplers have also been applied as environmental monitors at different locations.