Quantitative phase contrast imaging of arborescent graft polystyrene by off-axis transmission electron holography

Imaging nanoscale polymer objects in the Transmission Electron Microscope is difficult, because small polymeric objects interact only weakly with intermediate-energy electrons. Heavy element staining can induce significant amplitude contrast, but stains can introduce artifacts that complicate the structure determination at nanometer length scales. This paper explores transmission electron holography for phase contrast imaging of unstained arborescent graft polystyrene nanoparticles. Holography is able to recover significant phase contrast from these particles despite the fact that there is negligible amplitude contrast. Comparative imaging experiments show that off-axis holography provides substantially higher contrast than that generated by the traditional method of transferring phase information to amplitude information via defocus. This effect is a consequence of different lens contrast-transfer behavior in each of these two imaging approaches. Under kinematical conditions when the appropriate mean inner potential is known, the specimen's projected thickness can be directly mapped from the holographic phase image to give a measure of the specimen's three-dimensional shape. Such quantitative imaging shows that individual arborescent graft polystyrene nanoparticles, which are spherical in a good solvent, adopt a flattened shape when deposited on a carbon substrate and allowed to dry.     

Developing hypertext-based learning courseware for computernetworks: the macro and micro stages

In order to design and develop hypertext-based learning courseware for computer networks, one needs to know human learning processes and how hypertext can be used to facilitate learning, to be aware of appropriate instructional theories and models to guide design processes, and to consider pedagogical issues. The instructional systems development approach and the elaboration theory of instruction are introduced as the macro and micro stages of designing hypertext learning courses. The development of a sample course is reported. Discussions and a conclusion are provided     

Characterization of Perina nuda nucleopolyhedrovirus (PenuNPV) polyhedrin gene

The occurrence and metabolic capacities of sulfate-reducing bacteria (SRB) were studied in 23 water samples taken from producing wells at 14 different sites. Oil fields in France, the North Sea, and the Gulf of Guinea were selected and classified according to physicochemical parameters (salinity ranging from 0.3 to 120 g.L-1 and temperature between 29 and 85 degrees C). After the distribution of SRB within oil fields was studied, several strains of SRB were isolated and characterized metabolically. Twenty of the thirty-seven strains were not related to any known species. Most of the identified strains were members of the genera Desulfovibrio and Desulfotomaculum by molecular, morphological, and physiological properties.     

Analysis of a Software-Focused Products and Service Supply Chain

In this paper, we study a software-focused products and service supply chain based on the practice of two leading electronic manufacturing services providers in the world and their major corporate clients. We discuss the common and unique issues that a software-focused supply chain has compared with a traditional supply chain. We also indicate the research challenges and opportunities for a software-focused supply chain     

Off-state breakdown effects on gate leakage current in powerpseudomorphic AlGaAs/InGaAs HEMTs

The effects of off-state breakdown on characteristics of power AlGaAs/InGaAs pseudomorphic HEMTs (PHEMTs) are investigated in detail. While the gate leakage current is substantially decreased after breakdown stress, no obvious changes in drain-to-source current and transconductance are observed. Prior to breakdown stress, gate leakage current shows a nearly ideal 1/f noise characteristic with an Ig² dependence, suggesting a surface generation-recombination current from the interface of the passivation layer. After stress, the gate current noise can be drastically reduced. The results suggest an alternative for alleviating the gate leakage current in PHEMTs     

Two‐phase scale‐based reduction method for fulfilling monitoring service on mobile devices

One of the general location‐based services (LBSs) is the monitoring of real‐time locations of moving objects. When the number of moving objects is large and the task of monitoring is carried out on mobile devices, the monitoring service suffers from constraints of screen size, computing speed, and network bandwidth. In the present paper, a two‐phase scale‐based reduction method (SRM) consisting of a zoom phase and a mosaic phase, is proposed to overcome these constraints. The zoom phase reduces the original monitoring area which, in turn, undergoes further reduction in the mosaic phase. The performance was measured with the use of two ratios: the reduction ratio (RRatio) and the transmission ratio (TRatio). From the experimental results, the lowest RRatio was 52%, i.e. almost half of the original data size was reduced. The lowest average TRatio was also 52% for the worst case, i.e. the entire original monitoring area was displayed on the mobile device. Moreover, the display time was shortened from 14.3 to 0.7 s. These results show that the use of the two‐phase SRM is practical and efficient when applied to the monitoring service on mobile devices. Copyright © 2006 John Wiley & Sons, Ltd.     

Effects of morphology and oxygen supply on schizophyllan formation by Schizophyllum commune using a pellet size controlling bioreactor

The effects of mycelial morphology and oxygen supply on the production of the anti‐tumor polysaccharide from Schizophyllum commune were evaluated in this study. A pellet size controlling bioreactor has been used successfully for the production of the anti‐tumor polysaccharide of S commune. The average pellet size of mycelia in a bubble column bioreactor was around 20.5 mm in a typical run without using pellet size control. By forcing the fermentation broth through a pellet size control device with a stainless screen at five different fermentation times ranging from 1.0 to 4.5 days in each batch, different fungal pellet sizes ranging from 12.3 to 3.0 mm were achieved. The formation of anti‐tumor polysaccharide, schizophyllan (SPG), was significantly associated with the pellet morphology and oxygen supply rate. An optimal product yield of 0.29 g g^?1 glucose was obtained when the pellet size was controlled at 12.3 mm. Oxygen transfer limitation inside the pellets was responsible for the formation of entrapped polysaccharide. Maximum entrapped SPG yield (Yp/s entrapped) of 0.88 g g^?1 glucose occurred at the optimal pellet size of 12.3 mm. Copyright © 2005 Society of Chemical Industry