Dielectric relaxation of monoesters based poly(styrene-co-maleic anhydride) copolymer

A series of alkyl-grafted copolymers based on styrene-maleic anhydride (SMA) copolymers were synthesized by esterification of SMA with several long chain normal aliphatic alcohols. The prepared copolymers were characterized by FT-IR and ¹H NMR and DSC. The dielectric behavior of these copolymers was investigated in the frequency 20–10⁵ Hz and temperature −40 to 180 °C ranges. Two relaxation processes were observed, α, and β-relaxation. The former is associated with the glass-rubber transition and is characterized by the Vogel–Fulcher–Tammann temperature dependence and the latter relaxation is related to the local motion of the ester side groups attached to the polymer backbone. The apparent activation energy for the β-relaxation was found to depend significantly on the alkyl chain length. The dielectric analysis of the β-relaxation process detected is discussed.     

Modelling of proton exchange membrane fuel cell performance based on semi-empirical equations

Using semi-empirical equations for modeling a proton exchange membrane fuel cell is proposed for providing a tool for the design and analysis of fuel cell total systems. The focus of this study is to derive an empirical model including process variations to estimate the performance of fuel cell without extensive calculations. The model take into account not only the current density but also the process variations, such as the gas pressure, temperature, humidity, and utilization to cover operating processes, which are important factors in determining the real performance of fuel cell. The modelling results are compared well with known experimental results. The comparison shows good agreements between the modeling results and the experimental data. The model can be used to investigate the influence of process variables for design optimization of fuel cells, stacks, and complete fuel cell power system.     

Efficient detection algorithm for 2Nx2N MIMO systems using alamouti code and QR decomposition

We propose an efficient 2Ntimes2N MIMO detection algorithm where the transmit signals are grouped in pairs and separately coded using the standard Alamouti space-time code. At the receiver, one or more QR decompositions are performed and the upper triangular property of the R matrices so obtained is exploited in order to successively decode the transmitted symbols starting with those interference-free symbols corresponding to the last two rows and columns of R. Bit-error-rate simulation results, for a 4times4 MIMO system and a bandwidth efficiency of 8 bits/s/Hz, show that the proposed technique, while less complex than ordered MMSE V-BLAST, outperforms the latter by 2-6 dB at a BER of 10^-4     

Multiplex sequencing of 1.5 Mb of the Mycobacterium leprae genome

The nucleotide sequence of 1.5 Mb of genomic DNA from Mycobacterium leprae was determined using computer-assisted multiplex sequencing technology. This brings the 2.8-Mb M. leprae genome sequence to approximately 66% completion. The sequences, derived from 43 recombinant cosmids, contain 1046 putative protein-coding genes, 44 repetitive regions, 3 tRNAs, and 15 tRNAs. The gene density of one per 1.4 kb is slightly lower than that of Mycoplasma (1.2 kb). Of the protein coding genes, 44% have significant matches to genes with well-defined functions. Comparison of 1157 M. leprae and 1564 Mycobacterium tuberculosis proteins shows a complex mosaic of homologous genomic blocks with up to 22 adjacent proteins in conserved map order. Matches to known enzymatic, antigenic, membrane, cell wall, cell division, multidrug resistance, and virulence proteins suggest therapeutic and vaccine targets. Unusual features of the M. leprae genome include large polyketide synthase (pks) operons, inteins, and highly fragmented pseudogenes.     

Improving the program-planning skills of school psychologists: Use of performance feedback.

Reports results of an investigation that suggest the potential utility of performance feedback for improving the capability of school psychologists for planning psychological service programs. Nine school psychologists were randomly assigned to receive performance feedback by the director of school psychological services through 1 of 3 means: no feedback, weekly feedback, monthly feedback. Results indicate that both weekly and monthly feedback provided by the director resulted in greater improvement and maintenance of program-planning skills. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of maternal high histidine levels on activity and maze retention in the rat.

4 groups of pregnant albino rats were maintained on either a histidine-high diet, or received periodic injections of C-nitromethane, or they received both treatments throughout gestation. Later, the offspring were tested in an open field for activity in a maze-learning task and retested for the retention of the maze habit. Results show that both nitromethane injections and histidine-high diets resulted in impaired performance. On the open field test, the experimental Ss were more active, and on initial learning of the maze pattern they demonstrated a learning deficit. However, when retested 7 and 30 days later, they showed no deficit in retention of the maze habit. In addition, an analysis of covariance indicated that the hyperactivity and learning deficit were independent characteristics of maternal hyperhistidinemia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy balance for a DC plasma torch

A study was made of the energy utilization efficiency in a d.c. plasma toich operating with argon at atmospheric pressure at a power level of 10-25 kW. Calorimetric measurements of the energy lost to the cathode, anode and that remaining in the plasma jet showed that the torch efficiency was about 40 to 50%. It increases with an increase of the plasma gas flow rate but decreases with an increase of the current intensity. The electrode spacing was found to have no significant influence on the efficiency over the range investigated. The torch efficiency could be substantially improved by a reduction of the anode size. The addition of small concentrations of a diatomic gas such as nitrogen improved the efficiency to about 65% and increased the total power dissipated in the torch.     

The formation and interpretation of defect images from crystalline materials in a scanning transmission electron microscope.

The technique of scanning transmission electron microscopy (STEM) has been employed usefully in studies of amorphous materials, and the theory of image formation and interpretation in this case has been well developed. Less attention has been given to the practical and theoretical problems associated with the use of STEM for the examination of crystalline materials. In this case the contrast mechanisms are dominated by Bragg diffraction and so they are quite different from those occurring in amorphous substances. In this paper practical techniques for the observation and interpretation of contrast from defects in crystalline materials are discussed. It is shown that whilst images of defects are obtained readily under all typical STEM operating conditions, the form of the image and the information it contains varies with the angle subtended at the specimen by the detector. If this angle is too large significant image modifications relative to the "conventional" transmission electron microscope case may occur and the resolution of the image may degrade. If this angle is too small, then signal to noise considerations make an interpretation of the image difficult. In this paper we indicate how the detector angle may be chosen correctly, and also present techniques for setting up a STEM instrument for imaging a crystalline material containing lattice defects.     

Issues in the training of school psychologists in program evaluation.

Program evaluation is becoming increasingly important to all professional psychologists, including school psychologists. Despite a burgeoning of information about program evaluation principles, little attention has been given to program evaluation training, especially the utility of that training for program decision making. Five issues pertinent to the training of school psychologists in program evaluation are discussed: need for training, extent of training, goals of training, methods of training, and evaluation of training experiences. The material presented is based on the authors' experiences in program evaluation training at the Rutgers School Psychology Training Program. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficient motor synchrony in schizophrenia.

Introduced a laboratory measure of motor function, synchronization of tapping with an auditory stimulus, as an index of motor disorganization in schizophrenia. It was hypothesized that (a) schizophrenics' performance on this task would be distinguishable from that of controls and would reflect a relative inability to take advantage of stimulus predictability, independent of task difficulty; (b) clinical measures of disturbed motor behavior would be associated with poorer synchronization; and (c) synchronization performance would be associated with clinical ratings of formal thought disorder and type-token ratio assessment of disorganization in spoken language. 16 schizophrenic, 8 affective, and 8 normal controls (18–48 yrs) were studied. The schizophrenics showed a specific pattern of disrupted synchrony not consistent with explanations based on S motivation, task difficulty, motor dexterity, a general psychosis factor, drug effects, or tapping speed ability. Deficient motor performance was associated with clinical evidence of abnormal movement and disturbed thinking and with the type-token ratio. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)