Synthesis and Characterization of Polymer-Based Magnetic Nanocomposite with Uniformly Distributed Hematite Nanoparticles on the Surface of Polystyrene Aromatic Compound

Nanosize hematite (α-Fe₂O₃) particles were synthesized by the Sol-gel method and were used for preparing polystyrene@α-Fe₂O₃ (PS@α-Fe₂O₃) nanocomposites via microemulsion polymerization by using ammonium proxidisulfate (APS) as an initiator. The obtained nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrophotometer, thermo gravimetric analysis (TGA), and vibrating sample magnetometer (VSM), respectively. TEM analysis showed that the average particle size of the α-Fe₂O₃ and PS@α-Fe₂O₃ nanocomposites synthesized were about 25 and 80 nm, respectively. The polystyrene microsphere was uniformly coated by α-Fe₂O₃ nanoparticles and the shell-thickness of the core-shell hybrid particles was controlled by the feed of α-Fe₂O₃ nanoparticles during the polymerization.     

Bit-error probability for optimum combining of binary signals in the presence of interference and noise

We derive an exact bit-error probability (BEP) expression for coherent detection of binary signals with optimum combining in wireless systems in the presence of multiple cochannel interferers and thermal noise. A flat Rayleigh fading environment with space diversity, uncorrelated equal-power interferers, and additive white Gaussian noise is considered. The approach is to use the chain rule of conditional expectation together with the joint probability density function (pdf) of the eigenvalues of the interference correlation matrix. This joint pdf is related to the Vandermonde determinant. Let N/sub A/ denote the number of antennas and N/sub I/ the number of interferers. We consider both the cases of an overloaded system, in which N/sub I//spl ges/N/sub A/, and an underloaded system, in which N/sub I/相似文献   

An analytical approach to evaluate service coverage in slowfrequency-hopping mobile radio systems

The performance of a time-division multiple-access mobile radio system adopting slow frequency hopping is analyzed by following an original procedure that allows the evaluation of thermal noise and fast fading (e.g., Rayleigh) effects on block-coded transmission with nonideal interleaving. Starting from this approach, service coverage can be analytically evaluated when the “slow” disturbances affecting the transmission are fixed. The method proposed is able to take several impairments and parameters into account, such as shadowing and discontinuous transmission. The experimental results confirmed the validity of the theoretical approach     

Integrating blood cell mechanics,platelet adhesive dynamics and coagulation cascade for modelling thrombus formation in normal and diabetic blood

Normal haemostasis is an important physiological mechanism that prevents excessive bleeding during trauma, whereas the pathological thrombosis especially in diabetics leads to increased incidence of heart attacks and strokes as well as peripheral vascular events. In this work, we propose a new multiscale framework that integrates seamlessly four key components of blood clotting, namely transport of coagulation factors, coagulation kinetics, blood cell mechanics and platelet adhesive dynamics, to model the development of thrombi under physiological and pathological conditions. We implement this framework to simulate platelet adhesion due to the exposure of tissue factor in a three-dimensional microchannel. Our results show that our model can simulate thrombin-mediated platelet activation in the flowing blood, resulting in platelet adhesion to the injury site of the channel wall. Furthermore, we simulate platelet adhesion in diabetic blood, and our results show that both the pathological alterations in the biomechanics of blood cells and changes in the amount of coagulation factors contribute to the excessive platelet adhesion and aggregation in diabetic blood. Taken together, this new framework can be used to probe synergistic mechanisms of thrombus formation under physiological and pathological conditions, and open new directions in modelling complex biological problems that involve several multiscale processes.     

Oxalate membrane-selective electrode based on surfactant-modified zeolite

A novel polyvinyl chloride (PVC) membrane electrode for use in a potentiometric sensor for oxalate is described. The sensor comprises a surfactant-modified zeolite A (SMZ) as a modifier, dioctyl phthalate (DOP) as a plasticizer, and PVC matrix in the ratio 10:60:30 (modifier:DOP:PVC) (w/w). The membrane sensor showed a suitable response to oxalate in the concentration range of 1.0 × 10⁻⁶ to 3.0 × 10⁻¹ M (r = 0.9997), with a detection limit of 3.2 × 10⁻⁷ M and a Nernstian slope of −29.9 ± 0.6 mV per decade⁻¹ of oxalate concentration. The electrode response to oxalate remained constant in the pH range of 3.2–10.8. The selectivity coefficients for oxalate relative to a number of potential interfering substances were also determined. The sensor was highly selective for oxalate over a wide variety of other anions and exhibited a rapid response time of 5 s over a period of 2 months with good reproducibility. Thus, this novel sensor may be applied as an indicator electrode in the potentiometric titration of oxalate and Ca²⁺ ions.     

Non‐binary protograph low‐density parity‐check codes for space communications

Protograph‐based non‐binary low‐density parity‐check (LDPC) codes with ultra‐sparse parity‐check matrices are compared with binary LDPC and turbo codes (TCs) from space communication standards. It is shown that larger coding gains are achieved, outperforming the binary competitors by more than 0.3 dB on the additive white Gaussian noise channel (AWGN). In the short block length regime, the designed codes gain more than 1 dB with respect to the binary protograph LDPC codes recently proposed for the next generation up‐link standard of the Consultative Committee for Space Data Systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Concussion/Mild Traumatic Brain Injury (TBI) Induces Brain Insulin Resistance: A Positron Emission Tomography (PET) Scanning Study

Brain injury/concussion is a growing epidemic throughout the world. Although evidence supports association between traumatic brain injury (TBI) and disturbance in brain glucose metabolism, the underlying molecular mechanisms are not well established. Previously, we reported the release of cellular prion protein (PrPc) from the brain to circulation following TBI. The PrPc level was also found to be decreased in insulin-resistant rat brains. In the present study, we investigated the molecular link between PrPc and brain insulin resistance in a single and repeated mild TBI-induced mouse model. Mild TBI was induced in mice by dropping a weight (~95 g at 1 m high) on the right side of the head. The procedure was performed once and thrice (once daily) for single (SI) and repeated induction (RI), respectively. Micro PET/CT imaging revealed that RI mice showed significant reduction in cortical, hippocampal and cerebellum glucose uptake compared to SI and control. Mice that received RI also showed significant motor and cognitive deficits. In co-immunoprecipitation, the interaction between PrPc, flotillin and Cbl-associated protein (CAP) observed in the control mice brains was disrupted by RI. Lipid raft isolation showed decreased levels of PrPc, flotillin and CAP in the RI mice brains. Based on observation, it is clear that PrPc has an interaction with CAP and the dislodgment of PrPc from cell membranes may lead to brain insulin resistance in a mild TBI mouse model. The present study generated a new insight into the pathogenesis of brain injury, which may result in the development of novel therapy.     

Distributed generation modeling for power flow studies and a three-phase unbalanced power flow solution for radial distribution systems considering distributed generation

Distributed generations (DGs) are generally modeled as PV or PQ nodes in power flow studies (PFSs) for distribution system. Determining a suitable model for each DG unit requires knowing the DG operation and the type of its connection to the grid (direct or indirect). In this respect, this paper offers a helpful list of DG models for PFSs. Moreover, an unbalanced three-phase power flow algorithm for radial distribution networks considering DG is presented based on the power summation method in backward/forward sweep technique. The proposed algorithm is simple and fast and can handle DG units in both PV and PQ mode. In comparison with the current analysis methods, handling of PV nodes in the proposed method is very simple since it uses active and reactive powers as flow variables rather than the complex currents and then checks the limits of reactive power of the generator of PV node straightforwardly. IEEE four-node test feeder is used to validate the proposed method. IEEE 13-node test feeder without regulator and with different DG models is analyzed and the results are presented. Moreover, the results are compared with and without considering system losses.     

A study to identify S-S and S-S-S bonds in organic compounds by mass spectrometry and ultraviolet and Raman spectroscopy techniques

In the present study, after an investigation and study of organic di- and trisulfide characters, a method for the identification of S–S and S–S–S bonds using some common spectroscopy techniques, including ultraviolet (UV) spectroscopy, Raman, mass spectrometry (MS) and thin-layer chromatography (TLC), has been introduced and developed. It is worth mentioning that only the reported literature data and our own results have been used.     

Performance of narrowband CPM systems withlimiter-discriminator-integrator detection and decision feedbackequalization in mobile radio channels

A completely analytical approach is presented to achieve error probability analysis of limiter-discriminator-integrator (LDI) detection of binary continuous-phase modulation in a land mobile radio channel characterized by Rayleigh fading and Doppler effects. Optimum choice of the postdetection integration time is carried out when varying both system parameters and propagation characteristics, namely the Doppler shift. The improvements obtainable by means of decision feedback equalization (DFE) are also considered, in the presence of error propagation. The algorithm allows a very general analysis, which can be applied both to a partial and a full response modulation pulse, with narrowband IF filter and multipath propagation. This leads to the optimization of various system parameters, such as filter bandwidth, the modulation index, and the postdetection integration time, whatever the choice of the modulation pulse