Electrochemistry of aluminium in room temperature A1C13-TMPAC molten salts.

PhDAluminium can be electrodeposited on tungsten, aluminium, platinum, nickel and glassy carbon from 2: 1 A1C13-TMPAC (trimethylphenylammonium chloride) molten salts at room temperature. The A1C13-TMPAC melts diluted with 1,2-dichlorobenzene of had a beneficial effect on increasing aluminium deposition and stripping currents by decreasing viscosity and increasing the conductivity of the melt. The reductions of A12C17 ions were quasi-reversible and diffusion controlled, The irreversibility of the reductions was due to the relatively low conductivity and high viscosity of the melts. The aluminium deposition was associated with the reduction of the resulting product A1C14 ions following the locally changing acidity of the melts, and a corrosion reaction between fresh aluminium deposits and the melt. The mechanism for aluminium electrodeposition from 2: 1 A1C13-TMPAC was realised likely similar to that for the acidic A1C13- BPC melts. The bulk depositions of aluminium on all electrode except platinum involved three-dimensional instantaneous nucleation process followed by hemispherical diffusion-controlled growth of the developing nuclei. On platinum the nucleation process was characteristic of instantaneous at short time and then tended to progressive. The phenomena of aluminium UPD were found on all electrodes but not on aluminium itself, highly dependent upon substrates, and involved alloying effects on metal substrates. The UPD layers on the surface of the electrodes corresponded to about 2 -- 10 aluminium monolayer equivalents. The UPD was surface constrained on tungsten, whereas were diffusion controlled on nickel and platinum. The processes on tungsten and platinum were under the limitation of kinetics. On nickel and platinum, the electrodes and the nickel and platinum components in fresh deposits were likely to react with A12C17 and Cl' ions in the melt to form corresponding metal complexes. 11 The passivation phenomena were observed to occur on all electrodes. These could resulted from a black layer formed by AIC13 precipitates. Particularly, on aluminium the stripping of aluminium was involved in an active dissolution-passivation process.Knopp Electronics Services Lt

A sensitive and rapid assay for homologous recombination in mosquito cells: impact of vector topology and implications for gene targeting

BACKGROUND: Recent progress in insect transgenesis has been dramatic but existing transposon-based approaches are constrained by position effects and potential instability. Gene targeting would bring a number of benefits, however progress requires a better understanding of the mechanisms involved. Much can be learned in vitro since extrachromosomal recombination occurs at high frequency, facilitating the study of multiple events and the impact of structural changes among the recombining molecules. We have investigated homologous recombination in mosquito cells through restoration of luciferase activity from deleted substrates. The implications of this work for the construction of insect gene targeting vectors are discussed. RESULTS: We show that linear targeting vectors are significantly more efficient than circular ones and that recombination is stimulated by introducing double-strand breaks into, or near, the region of homology. Single-strand annealing represents a very efficient pathway but may not be feasible for targeting unbroken chromosomes. Using circular plasmids to mimic chromosomal targets, one-sided invasion appears to be the predominant pathway for homologous recombination. Non-homologous end joining reactions also occur and may be utilised in gene targeting if double-strand breaks are first introduced into the target site. CONCLUSIONS: We describe a rapid, sensitive assay for extrachromosomal homologous recombination in mosquito cells. Variations in substrate topology suggest that single-strand annealing and one-sided invasion represent the predominant pathways, although non-homologous end joining reactions also occur. One-sided invasion of circular chromosomal mimics by linear vectors might therefore be used in vitro to investigate the design and efficiency of gene targeting strategies

Relation Based Access Control in Campus Social Network System

AbstractAs one of the most popular network applications, online social network system has gained huge adoption in the past few years. Campus social network system is a special type of social network system which focuses on providing information communication, knowledge sharing, and online collaboration services to campus users in colleges and universities. In this paper, we discuss the design of relation based access control in campus social network system which is decided by the collective efforts system designers, system administrators, and especially users of the system. Generally speaking, relation based access control in campus social network system is defined in terms of users can establish relationships; and they can also assign relation based permissions on information and resources when they release them. It consists of user-centered access control and group-centered access control which deal with access control of information and resources released in users’ personal space and groups’ shared space respectively. Once a campus social network system is put online, access control in it is actually decided by the collective intelligence of its users. Specifically, it's built upon collective intelligence that is reflected through users’ identity, their social relationships and permissions that they set on their profile and created content. In a word, relation based access control in campus social network system adopts a collective intelligence model

Study of Photonic Crystal Structures by Thz-tds

The purpose of this study was to examine the behavior of dielectric and metallic photonic crystal structures embedded in single mode metal parallel plate waveguide (PPWG). The terahertz (THz) pulse was coupled in and out by two plano-cylindrical silicon lenses. The photonic crystals were fabricated by using Micro-Electro-Mechanical-Systems (MEMS) technology, which constructed very high aspect ratio structures. The transmission properties of the THz radiation of these structures were investigated using terahertz time-domain spectroscopy (THz-TDS). We demonstrated the transmitted THz bandgaps in the 2D polymer (SU-8) photonic crystal structures, 2D metallic photonic crystal structures and 2D metallic photonic crystal defect structures. The experimental results matched the transfer matrix method (tmM) and the finite difference time domain (FDTD) simulation results very well. A very important conclusion is that the advantages of single mode PPWG and the coupling method give us a powerful tool to simulate infinite 2D ideal photonic crystal structures. This method can be used to do the farther research of THz photonic crystal structures. Some applications such as photonic crystal waveguide and tunable photonic bandgap are also investigated and demonstrated.School of Electrical & Computer Engineerin

Self-excision of the BAC sequences from the recombinant Marek's disease virus genome increases replication and pathogenicity

Cloning of full length genomes of herpesviruses as bacterial artificial chromosomes (BAC) has greatly facilitated the manipulation of the genomes of several herpesviruses to identify the pathogenic determinants. We have previously reported the construction of the BAC clone (pRB-1B5) of the highly oncogenic Marek's disease virus (MDV) strain RB-1B, which has proven to be a valuable resource for elucidating several oncogenic determinants. Despite the retention of the BAC replicon within the genome, the reconstituted virus was able to induce tumours in susceptible chickens. Nevertheless, it was unclear whether the presence of the BAC influenced the full oncogenic potential of the reconstituted virus. To maximize the closeness of BAC-derived virus to the parental RB-1B strain, we modified the existing pRB-1B5 clone by restoring the Us2 and by introducing SV40-cre cassette within the loxP sites of the mini-F plasmid, to allow self-excision of the plasmid sequences in chicken cells. The reconstituted virus from the modified clone showed significant improvement in replication in vitro and in vivo. Excision of the BAC sequences also enhanced the pathogenicity to levels similar to that of the parental virus, as the cumulative incidence of Marek's disease in groups infected with the recombinant and the parental viruses showed no significant differences. Thus, we have been able to make significant improvements to the existing BAC clone of this highly oncogenic virus which would certainly increase its usefulness as a valuable tool for studies on identifying the oncogenic determinants of this major avian pathogen

Preparation and Free Radical Detection of Doped ZnO Nanomaterials

Nanomaterials play an important role in the field of optics and medicine, and rare earth cerium can act as a catalyst and a dopant to increase improve its optical properties. Used nanometer zinc oxide as a carrier, the Ag-ZnO and Ag-Ce-ZnO samples were prepared with the sol-gel method and characterized by X-ray diffractometer. The nanometer zinc oxide materials can generate the free hydroxyl radicals, so the methylene blue solution (MB) was used as the capture agent, and the free radicals produced by the doped nanometer zinc oxide were detected by UV-spectrophotometry. The results showed that the preparation particle size of the Ag-ZnO sample was about 75nm, particle size of the Ag-Ce-ZnO sample was about 70nm. The concentration of two samples treated with the dispersant PAAS generated hydroxyl radicals is much larger than the two samples treated with the dispersant SDBS. The doping of Ce ions not only improved the optical activity of the samples, but also increased the content of hydroxyl radicals. Rare-earth doped effe ctively improved the optical properties of the ZnO nanoparticles, and the effect of sample Ag-Ce-ZnO was better than Ag-ZnO samples. Discussion and study on the nature of both the nanometer zinc oxide and doped nanometer zinc oxide, as well as the method of preparation and the theory of produce hydroxyl radicals. In the experiment, doped nano-ZnO was used as carrier and methylene blue (MB) as capture reagent. This study provided a new method for the detection of free radicals drugs

Study on the mechanisms of refracturing technology featuring temporary plug for fracturing fluid diversion in tight sandstone reservoirs

Well production rates in unconventional plays usually decline dramatically in the first year. Refracturing, which is a remedial production operation, is often done because original hydraulic fracturing failed to contribute any significant amount of flow or significant unfractured pay exists in the well. In order to maximize the fracturing fluid contact with the intact rock and to stimulate more reservoir volume in previously stimulated wells, a refracturing technology featuring a novel temporary plugging for fluid diversion is developed to enable the fracturing fluid to reach the untouched areas and to create reoriented fractures. In this paper, laboratory physical simulation tests of refracturing using fiber for effective temporary plugging is carried out to study the refracture morphology and the influencing factors of refractures. Results show that the refracture morphology is affected by the horizontal stress difference, the injection rate of initial fracturing fluid, and the natural fractures. Under condition of the different horizontal stress differences, the fracture initiation and orientation angle are different. When the horizontal stress difference is small, it is easy to form large angle fractures. The injection rate of initial fracturing fluid affects the length of initial fractures and refractures. The smaller the initial fracturing fluid injection rate is, the better the effect of temporary plugging in refracturing. The presence of natural fractures will lead to reorientation of refractures to form a complex fracture network. This study provides a theoretical guidance and technology support for refracturing operations

Molecular anchors in the solid state: Restriction of intramolecular rotation boosts emission efficiency of luminogen aggregates to unity

Introduction of freely rotatable tetraphenylethene (TPE) to conventional luminophors quenches their light emissions in the solutions but endows the resultant molecules (TPEArs) with aggregation-induced emission characteristics in the condensed phase due to the restriction of intramolecular rotation. High fluorescence quantum yields up to 100% have been achieved in the films of TPEArs

THz parallel plate photonic waveguides

We have observed narrowband transmission or rejection in the frequency spectra of THz pulses transmitted through air-spaced parallel plate photonic waveguides. These waveguides have one of the metal plates covered by a silicon plate with a metallic photonic band gap (PBG) surface precisely fabricated by lithographic techniques. We use two different PBG surface types: an array of metallic cylindrical pillars, and an array of metallic cylindrical holes. With the inversion of the PBG structures from cylinders to holes, the output spectra changes from narrow bandpass to narrow band-reject filtering. These photonic waveguides show extremely sharp spectral responses in regions as large as 1 THz, with stop bands or transmission bands having contrasts of as much as 90 dB.Peer reviewedElectrical and Computer Engineerin