Electropolymerization of thionine as a stable film along with carbon nanotube for sensitive detection of tetracycline antibiotic drug

Iranian Polymer Journal - Herein, a simple, rapid, cost-effective and sensitive poly(thionine)-based electrochemical sensor is described to determine trace amounts of tetracycline. In the present...     

Coupling potentials in CA1 neurons during calcium-free-induced field burst activity

Small amplitude depolarizations (fast prepotentials, spikelets) recorded in mammalian neurons are thought to represent either dendritic action potentials or presynaptic action potentials attenuated by gap junctions. We have used whole-cell recordings in an in vitro calcium-free model of epilepsy to record spikelets from CA1 neurons of the rat hippocampus. It was found that spikelet appearance was closely correlated with the occurrence of dye coupling between pyramidal neurons, indicating that both phenomena share a common substrate. Spikelets were characterized according to waveform (amplitude and shape) and temporal occurrence. Spikelet amplitudes were found to be invariant with neuronal membrane potential, and their pattern of occurrence was indistinguishable from patterns of action potential firing in these cells. Voltage and current recordings revealed a spikelet waveform that was usually biphasic, comprised of a rapid depolarization followed by a slower hyperpolarization. Numerical differentiation of spike bursts resulted in waveforms similar to recorded spikelet sequences, while numerical integration of spikelets yielded waveforms that were indistinguishable from action potentials. Modification of spikelet waveforms by the potassium channel blocker tetraethylammonium chloride suggests that spikelets may arise from both resistive and capacitive transmission of presynaptic action potentials. Intracellular alkalinization and acidification brought about by perfusion with NH4Cl caused changes in spikelet frequency, consistent with reported alterations of field burst activity in this model of epilepsy. These results suggest that spikelets result from gap junctional communication, and may be important determinants of neuronal activity during seizure-like activity.     

Co(OH)2 nanoparticles deposited on reduced graphene oxide nanoflake as a suitable electrode material for supercapacitor and oxygen evolution reaction in alkaline media

In this work, cobalt hydroxide nanoparticles are simply synthesized (size is about 50 nm) and deposited on the reduced graphene oxide nanoflake by the hydrothermal method. Then, the ability of glassy carbon electrode modified with this low-cost nanocomposite is examined as a supercapacitor and oxygen evolution electrocatalysts in 2.0 mol L^?1 KOH by a three-electrode system. The modified electrode as a pseudocapacitor with potential windows of 0.35 V, exhibits a powerful specific capacitance (235.20 F g^?1 at 0.1 A g^?1 current density), energy density, stability (about 90% of the initial capacitance value maintain after 2000 cycles at 1.0 A g^?1) and fast charge/discharge ability. Furthermore, the modified electrode displays a good electrocatalytic activity for oxygen evolution reaction with a current density of 10.0 mA cm^?2 at 1.647 V, small Tafel slope of 56.5 mV dec^?1, good onset potential of 1.521 V vs. RHE and suitable durability.     

Use of a novel initiator for synthesis of amino-end functionalized polystyrene (NH2-PS) by atom transfer radical polymerization

Here we report a versatile new method for end-functionalizing polystyrene. In order to produce polystyrene with an amino end group, 2-(3-bromo-3-phenylpropyl)isoindoline-1,3-dione was synthesized and used as a novel initiator for ATRP. After ATRP polymerization, tri-n-butyltin hydride ((n-Bu)₃SnH) reductively replace existing halogens on polymer chains by hydrogen. Finally, the phthaloyl groups on polymer backbone were cleaved by treatment with hydrazine yielding amino terminated polystyrene. A polymer with M _n ≈ 10,350 and M _w/M _n = 1.17 was obtained. Therefore, this method allows the preparation of amino end functionalized polystyrene of narrow polydispersity with complete degree of functionalization.     

Effects of nanoclay on rheological properties of bitumen binder

Nanoclays are the new generation of processed clays of interest in a wide range of high performance composites. In other words, nanoclay is defined as clay that can be modified to make the clay complexes compatible with organic monomers and polymers. Here, it can be said that the polymeric nanocomposites are among the most exciting and promising classes of materials discovered recently. A number of physical properties can be enhanced successfully when as a polymer is modified with small amount of nanoclay on condition that the clay is dispersed at nanoscopic level. This research has accomplished a comparative rheological test on the unmodified and nanoclay modified bitumen. For that matter, so, two types of nanoclay were used: nanofil-15 and cloisite-15A. The nanostructure exfoliation of nanoclay platelets in bitumen has been studied using X-ray diffraction (XRD). In the present research, although the empirical rheological test on bitumen are penetration, softening point, ductility and ageing effect, the fundamental rheological test by dynamic shear rheometer (DSR) is conducted on modified and unmodified bitumen. Test results show that while nanoclay changes rheological properties of bitumen and increases stiffness, it also decreases angle phase and improves ageing resistances, as well.     

Theory and design of multirate sensor arrays

This paper studies the basic design challenges associated with multirate sensor arrays. A multirate sensor array is a sensor array in which each sensor node communicates a low-resolution measurement to a central processing unit. The objective is to design the individual sensor nodes and the central processing unit such that, at the end, a unified high-resolution measurement is reconstructed. A multirate sensor array can be modeled as an analysis filterbank in discrete-time. Using this model, the design problem is reduced to solving the following two problems: a) how to design the sensor nodes such that the time-delay of arrival (TDOA) between the sensors can be estimated and b) how to design a synthesis filterbank to fuse the low-rate data sent by the sensor nodes given the TDOA? In this paper, we consider a basic two-channel sensor array. We show that it is possible to estimate the TDOA between the sensors if the analysis filters incorporated in the array satisfy specific phase-response requirements. We then provide practical sample designs that satisfy these requirements. We prove, however, that a fixed synthesis filterbank cannot reconstruct the desired high-resolution measurement for all TDOA values. As a result, we suggest a fusion system that uses different sets of synthesis filters for even and odd TDOAs. Finally, we use the H/sub /spl infin// optimality theory to design optimal synthesis filters.     

Limitations and capabilities of frequency domain broadbandconstrained beamforming schemes

Time domain processing of broadband signals using an array of sensors is normally carried out by a transversal filter, and the filter coefficients are adjusted by solving a constrained beamforming problem that requires manipulation of matrices of dimension LJ×LJ with L denoting the number of sensors in the array and J denoting the filter length. This paper studies a frequency domain method to compute the coefficients of transversal filter, compares its performance, sensitivity to the look direction, and computational efficiency with that of the direct method, and shows how the computational saving increases using the frequency domain method as the number of elements and the filter length are increased. The paper presents a number of techniques that exploit the inherent structure present in the frequency domain method to reduce the computation load and shows that the real-time computational saving of the order of 12520 folds is possible for an array of 100 elements using a tap delay line filter of 100 taps. The paper demonstrates that a beamformer using this method is able to produce more output SNR with less computation time than the one using the normal time domain method     

Development and characterisation of a sugar‐free milk‐based dessert formulation with fig (Ficus carica L.) and carboxymethylcellulose

The objective of this study was to develop an optimum formula for ‘Shir Anjir’, an Iranian dessert containing milk, dried fig (13, 16.5, 20%) and carboxymethylcellulose (CMC) (0, 0.35, 0.7%) with no added sugar. Apparent viscosity, flow behaviour indices, pH, acidity (% lactic acid), total solid and colour parameters were compared. Sensory tests were performed to evaluate degree of liking of colour, appearance, taste, texture, mouthfeel and general acceptance. Figs and CMC influenced the dessert's characteristics. The most popular formula contained milk, 16.5% figs and 0.7% CMC and had an apparent viscosity of 3.78 Pa·s at 5 °C, exhibiting a shear‐thinning behaviour.     

Residual stress analysis of autofrettaged thick-walled spherical pressure vessel

In this study, residual stress distributions in autofrettaged homogenous spherical pressure vessels subjected to different autofrettage pressures are evaluated. Results are obtained by developing an extension of variable material properties (VMP) method. The modification makes VMP method applicable for analyses of spherical vessels based on actual material behavior both in loading and unloading and considering variable Bauschinger effect. The residual stresses determined by employing finite element method are compared with VMP results and it is demonstrated that the using of simplified material models can cause significant error in estimation of hoop residual stress, especially near the inner surface of the vessel. By performing a parametric study, the optimum autofrettage pressure and corresponding autofrettage percent for creating desirable residual stress state are introduced and determined.