Millimeter Wave Power Combiner Based on a Half-Open Resonator

Experimental investigations of quasi-optical power combiner based on a half-open resonator are described. Power and frequency characteristics have been studied for one or three diodes. It is shown that the positioning of the diodes is preferred over the center of the field spot along a resonator axis.     

An inverse finite element minimization-based method for solution of multi-dimensional phase-change and material boundary shapes

An inverse finite element method for solution of unknown multidimensional phase-change and material boundary shapes is presented. The method is based on minimization and requires boundary shape parametrization. The unknown boundary parameters are determined by minimizing the error between a limited number of known (e.g. measured) temperatures and the temperatures associated with the iteratively altered boundary. The algorithm presented is based on the multidimensional downhill simplex minimization method. The inverse method is illustrated and verified using a model of the plasma arc welding process. In particular, it is shown that the technique is capable of accurately determining a specified weld pool capillary interface shape using a limited number of simulated thermocouple measurements. The code's ability to determine the interface shape is investigated under various interface-thermocouple separations, using varying numbers of simulated thermocouples.     

APA finances: Future prospects and plans.

Proposes that the American Psychological Association (APA) will face future deficits unless plans are made to avoid them. This proposal is based on a 5-yr forecast for 1972–1976. The Council of Representatives will be asked to establish financial goals and to assign responsibility for achieving goals to boards and committees of the APA. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of Pannexin 1 ATP-Permeable Channels in the Regulation of Signaling Pathways during Skeletal Muscle Unloading

Skeletal muscle unloading results in atrophy. We hypothesized that pannexin 1 ATP-permeable channel (PANX1) is involved in the response of muscle to unloading. We tested this hypothesis by blocking PANX1, which regulates efflux of ATP from the cytoplasm. Rats were divided into six groups (eight rats each): non-treated control for 1 and 3 days of the experiments (1C and 3C, respectively), 1 and 3 days of hindlimb suspension (HS) with placebo (1H and 3H, respectively), and 1 and 3 days of HS with PANX1 inhibitor probenecid (PRB; 1HP and 3HP, respectively). When compared with 3C group there was a significant increase in ATP in soleus muscle of 3H and 3HP groups (32 and 51%, respectively, p < 0.05). When compared with 3H group, 3HP group had: (1) lower mRNA expression of E3 ligases MuRF1 and MAFbx (by 50 and 38% respectively, p < 0.05) and MYOG (by 34%, p < 0.05); (2) higher phosphorylation of p70S6k and p90RSK (by 51 and 35% respectively, p < 0.05); (3) lower levels of phosphorylated eEF2 (by 157%, p < 0.05); (4) higher level of phosphorylated GSK3β (by 189%, p < 0.05). In conclusion, PANX1 ATP-permeable channels are involved in the regulation of muscle atrophic processes by modulating expression of E3 ligases, and protein translation and elongation processes during unloading.     

On cognitive processes in cognitive radio networks

In this article we model the cognitive processes and evaluate their impact on the performance of cognitive radio networks (CRN). Operation of the cognitive radio nodes, can be characterized by two types of processes: communication processes such as packets transmission, and cognitive processes such as estimation of the network state and decision-making for dynamic resource allocation. We propose a continuous time Markov chain model of CRN that couples these processes into unified queueing framework and analyze it by means of the matrix-geometric approach. From the obtained results, we derive the performance measures of CRN such as average delay and throughput, and establish their dependencies on the underlying cognitive processes. Additionally, we design an efficient policy for accessing the vacant channels and managing the transmission-sensing trade-off, which arises when transmissions and sensing are mutually exclusive. The policy search is carried out by the stochastic optimization method of cross-entropy. The optimized policy leads to significantly enhanced performance of CRN.     

Effect of various parameters on the conductivity of free standing electrosynthesized polypyrrole films

Electrical characteristics of polypyrrole films electrodeposited in different aqueous electrolyte solutions including p-toluenesulfonate, naphtalenesulfonate, nitrate, tetrafluoroborate, and perchlorate anions were investigated using the Van der Pauw procedure. The polymer films were synthesized by electrochemical oxidation at a fixed potential. Experimental parameters including the pyrrole concentration, electrolyte, applied potential and substrate were shown to affect the electrical conductivity σ of polypyrrole films. Since the substrate contributes significantly to the overall conductivity of polypyrrole-coated electrodes, the results obtained with free standing polymer films appeared more reliable. The results indicated that the p-toluenesulfonate doped PPy film showed the highest average conductivity (σ_293 K = 4.5 × 10⁵ S m^?1) whereas the perchlorate doped one produced the lowest of all the films prepared (σ_293 K = 2 × 10⁴ S m^?1).