Characterization of ZnS grown by metal-organic chemical vapour deposition on GaAs(100) using t-butyl mercaptan and dimethylzinc

ZnS has been grown on GaAs(100) substrates by atmospheric pressure metal–organic chemical vapour deposition (MOCVD) using dimethylzinc (DMZn) and t-butyl mercaptan (t-BuSH). The effects of the reactant gas phase molar ratio and the growth temperature on the characteristics of the material grown have been investigated. The structural quality of the layer is demonstrated by X-ray rocking curve half-widths of less than 300 arcsec for the epilayers. There is little significant pre-reaction and the layers are of excellent surface morphology and layer uniformity.     

Cooperative multihop broadcast for wireless networks

We address the minimum-energy broadcast problem under the assumption that nodes beyond the nominal range of a transmitter can collect the energy of unreliably received overheard signals. As a message is forwarded through the network, a node will have multiple opportunities to reliably receive the message by collecting energy during each retransmission. We refer to this cooperative strategy as accumulative broadcast. We seek to employ accumulative broadcast in a large scale loosely synchronized, low-power network. Therefore, we focus on distributed network layer approaches for accumulative broadcast in which loosely synchronized nodes use only local information. To further simplify the system architecture, we assume that nodes forward only reliably decoded messages. Under these assumptions, we formulate the minimum-energy accumulative broadcast problem. We present a solution employing two subproblems. First, we identify the ordering in which nodes should transmit. Second, we determine the optimum power levels for that ordering. While the second subproblem can be solved by means of linear programming, the ordering subproblem is found to be NP-complete. We devise a heuristic algorithm to find a good ordering. Simulation results show the performance of the algorithm to be close to optimum and a significant improvement over the well known BIP algorithm for constructing energy-efficient broadcast trees. We then formulate a distributed version of the accumulative broadcast algorithm that uses only local information at the nodes and has performance close to its centralized counterpart.     

An array processor for general purpose digital image compression

A new VLSI processor (DIP chip) for image compression is presented which combines principles of multipipeline and array processing. The device is not specific to any one image compression algorithm and can be regarded as a general purpose processor. The chip has been implemented using a CMOS 1.0-μm process on a 14.4×13.5-mm² die. An internal clock frequency of 40 MHz results in 1.2×10⁹ operations/s on 8-bit data. Solutions to problems associated with the large bandwidth required, for both image data and instruction streams, is the main aim of the paper. The necessary problem of increasing the array clock frequency relative to the input/output clock frequency without the need for a large on-chip instruction cache or fast external clock speeds is also addressed     

The rhetoric and reality of housing choice: The role of urban consolidation

In Australia, growth at the fringe has been seen as an inevitable response to a lack of affordable housing in the inner and middle zones of the major metropolitan cities. Urban consolidation was seen as one way of improving housing affordability and increasing housing choices and, at the same time, constraining outward growth. It will do so only if households forego past preferences for ownership of a detached house. This paper examines the contribution urban consolidation has made to meeting affordability and choice objectives by providing some insights into whether households are trading off tenure choices for lifestyle choices based on location and dwelling type. It also provides information on the extent of spatial polarisation of income that has contributed to the observed outcomes.     

The nootropic correction of disorders in learning and memory processes induced by extreme exposures

Experiments on rats demonstrated that the low-intensity electromagnetic field (12.6 cm, 2375 MHz, power density 1 mW/cm2), motion sickness, and electroconvulsive shock provoked the retrograde amnesia in the passive avoidance test. The oxyracetam (100 mg/kg, i.p.), aniracetam (50 mg/kg, i.p.), nooglutil (50 mg/kg, i.p.), meclofenoxate (50 mg/kg, i.p.), pyracetam (200 mg/kg, i.p.), and GABA (200 mg/kg, i.p) prevented the memory-impairing effect of all these extreme factors. On the contrary, the N-acetylglycinamide, semax, and other nootropic drugs were effective only under one or two extreme conditions.     

In vivo characterization of cytotoxic intracellular edema by multicomponent analysis of transverse magnetization decay curves

The precise measurement of low numbers of leukocyte below 0.1 WBC/microliter in filtered red cell or platelet suspensions meet both aims: to check the compliance with previously determined requirements and to evaluate the performances of novel filtering material (5 log depletion or more), justified by more and more important clinical use. The reliability of results, obtained with the chosen method, is ensured by applying of validation protocol, including training of technologist, assessment of the analytical range and the detection limit, assessment of precision and accuracy. The flow cytometry (FC) and Nageotte Chamber (NC) method are the both techniques which are currently used in routine Quality Control (QC) and validated by multicenter studies. Recent developments are made for increasing the sensibility of these counting methods, thanks to higher concentration or volume of the sample to be analysed. Among the experimental techniques, requiring more advances before implementing in QC program, quantitative PCR must become essential as reference method for evaluating the efficiency of filtration, in the future.     

Genetic analysis of delta helD and delta uvrD mutations in combination with other genes in the RecF recombination pathway in Escherichia coli: suppression of a ruvB mutation by a uvrD deletion

Helicase II (uvrD gene product) and helicase IV (helD gene product) have been shown previously to be involved in the RecF pathway of recombination. To better understand the role of these two proteins in homologous recombination in the RecF pathway [recBCsbcB(C) background, we investigated the interactions between helD, uvrD and the following RecF pathway genes: recF, recO, recN and ruvAB. We observed synergistic interactions between uvrD ant the recF, recN, recO and recG genes in both conjugational recombination and the repair of methylmethane sulfonate (MMS)-induced DNA damage. No synergistic interactions were detected between helD and the recF, recO and regN genes when conjugational recombination was analyzed. We did, however, detect synergistic interactions between helD and recF/recO in recombinational repair. Surprisingly, the uvrD deletion completely suppressed the phenotype of a ruvB mutation in a recBCsbcB(C) background. Both conjugational recombination efficiency and MMS-damaged DNA repair proficiency returned to wild-type levels in the deltauvrDruvB9 double mutant. Suppression of the effects of the ruvB mutation by a uvrD deletion was dependent on the recG and recN genes and not dependent on the recF/O/R genes. These data are discussed in the context of two "RecF" homologous recombination pathways operating in a recBCsbcB(C) strain background.