Wave excitations of drifting two-dimensional electron gas under strong inelastic scattering

We have analyzed low-temperature behavior of two-dimensional electron gas in polar heterostructures subjected to a high electric field. When the optical phonon emission is the fastest relaxation process, we have found existence of collective wave-like excitations of the electrons. These wave-like excitations are periodic in time oscillations of the electrons in both real and momentum spaces. The excitation spectra are of multi-branch character with considerable spatial dispersion. There are one acoustic-type and a number of optical-type branches of the spectra. Their small damping is caused by quasi-elastic scattering of the electrons and formation of relevant space charge. Also there exist waves with zero frequency and finite spatial periods - the standing waves. The found excitations of the electron gas can be interpreted as synchronous in time and real space manifestation of well-known optical-phonon-transient-time-resonance. Estimates of parameters of the excitations for two polar heterostructures, GaN/AlGaN and ZnO/MgZnO, have shown that excitation frequencies are in THz-frequency range, while standing wave periods are in sub-micrometer region.Comment: 26 pages and 6 figure

Injection statistics simulator for dynamic analysis of noise in mesoscopic devices

We present a model for electron injection from thermal reservoirs which is applied to particle simulations of one-dimensional mesoscopic conductors. The statistics of injected carriers is correctly described from nondegenerate to completely degenerate conditions. The model is validated by comparing Monte Carlo simulations with existing analytical results for the case of ballistic conductors. An excellent agreement is found for average and noise characteristics, in particular, the fundamental unities of electrical and thermal conductances are exactly reproduced.Comment: 4 pages, revtex, 4 PS figures, accepted Semicond. Sci. Techno

Development and Characterization of a Model Latent Herpes Simplex Virus Infection in Cultured Cells

Herpes simplex virus is the classic example of a virus which persists indefinitely in the host following the initial infection. Recurrent episodes of active virus growth characterize the infection in some individuals . In addition to the periodic flair-ups of active virus growth, the persistence of virus may be expressed in a more subtle way. It is possible that one or more types of human cancer result from the persistence of this virus in the host. The exact mechanism by which the virus is maintained in the host between outbreaks of active growth is not known. It is usually not possible to isolate the virus between the outbreaks and the virus is said to be latent during this period. Most of the available evidence indicates that the virus exists in a nonreplicating form when it is latent. This dissertation describes the establishment and characterization of a model latent herpes simplex virus infection in cell cultures . Cultures of rabbit kidney cells were infected with approximately one infectious unit of virus per 100 cells and incubated at 41C for 1-7 days. No evidence of virus growth was seen at 4 1C and infectious virus disappeared from the cells very rapidly at this temperature. Two-hundred infected cultures were transferred to 37C after incubation at 41C. In 43% of these cultures virus was recovered within 3 days after incubation at 3 7C. In 16% of these cultures no virus was recovered after incubation at 3 7C for up to 150 days. In the remaining 41% of the cultures, however, virus growth occurred but only after lag periods of variable length. The longest lag period was 45 days and the average lag period was 15.3 days. During the period when no evidence of virus growth was seen, treatment of the cells by freeze-thawing or by sonication failed to yield infectious virus. Once active virus growth occurred, virus was able to be isolated from the cultures and this virus was neutralized by commercial herpes simplex virus antiserum. Quantitative studies indicated that 0.25-1% of the inoculum virus was able to survive incubation at 41C for up to 6 days and replicate after transfer to 3 7C. Immunofluorescence studies indicated that virus-specific antigens were produced at 4 1C. Fluorescence microscopy of cells stained with acridine orange indicated that the block in virus replication occurred early in the infection cycle. Characteristic features of cells infected with virus at 3 7C were absent from the cells infected at 41C. Although virus failed to replicate in rabbit kidney cells at 41C, control cells preincubated at 41C were fully competent to replicate exogenous virus immediately after transfer to 3 7C . An attempt was made to establish the latent infection in cells directly at 3 7C by using a very small inoculum of virus . The latent infection could not be established in this way. When virus was added directly onto cells at 3 7C, active virus growth was always seen within 3 days or no growth occurred at all in cultures maintained for up to 30 days . A latent infection similar to that established in rabbit kidney cells was established in Wistar-38 cells. However, attempts to establish a similar infection in human kidney cells were unsuccessful. The basis for this cell-dependent difference was not investigated. Cultures were treated with certain hormones and chemical agents in attempts to modify the latent infection. Hormones that were used include hydrocortisone, 17 B-estradiol, progesterone, L-thyroxin and L- epinephrine. Treatment of cultures with progesterone at the time that the cultures were infected with virus and incubated at 41C resulted in a significant reduction in the number of cultures from which virus was recovered after transfer to 3 7C. The other hormones did not affect the latent infection in this way. Three chemical agents, 5-bromo-2-deoxyuridine, 5-iodo-2- deoxyuridine, and puromycin increased the reactivation rates of virus from cultures when the cultures were treated with the agent at the time of infection with virus and incubation at 41C. When cultures were treated with 5-bromo-2-deoxyuridine at the time of transfer from 41C to 3 7C (after the latent infection had already been established) the overall recovery rate was the same from treated cultures as from control cultures. However, the average lag period of the treated cultures was significantly increased. Finally, treatment of cultures with neutral red dye and exposure of these cultures to strong visible light had no effect on the overall recovery rate but did increase the average lag period of the treated cultures

Azerbaijan frameworks:geopolitical and socio-economic considerations

The contribution intends to present a framework as updated as possible on Azerbaijan, a country of which we are hearing more and more but not very well known and known to most, trying to provide an overview of what Azerbaijan is today, paying particular attention to the history of this interesting country in order to understand what it is today and even more what is the path taken for its future development. Therefore, some areas and aspects of the country have been identified, which will be, to follow, argued. Starting from the entirely geographical aspects to the more socio-cultural, then moving on to international relations and geopolitics and finally to the economic aspects

Sensory information processing in mouse barrel cortex

Processazione dell'informazione sensoriale nella "barrel cortex" di top

Relations between a Country and a Continent: China and Africa. A first and not a simple matter......

Through this contribution of a geopolitical approach, the author intends to propose an updated and accurate framework on the relations between China and Africa as well as some critical reflections on various geopolitical and geo-economic aspects concerning the intense development of the diversified economic relations between China and the different African States. China's foreign economic policy in Africa has laid solid foundations through the implementation of the various Sino-African Cooperation Forums that have taken place since 2000 and that have seen an increasing involvement of the Chinese government in the process. This paper intends to make a brief reflection on China's visible economic and geopolitical interest in the African Continent as a whole. The analysis that follows traces the main stages in the history of relations between China and Africa, emphasizing the increased importance of the Sino-African forums that led to what is now known as Chinese neo-colonization. In addition, the case studies of the Silk Road and the Rare Lands are highlighted. Finally, some of the social impacts of the Chinese presence in Africa are also examined such as the construction of new cities for the Chinese migrant population and the teaching of the Chinese language (Mandarin) in schools in some African Countries

Buccal and topical drug delivery

The aim of this work is to investigate new and classical techniques, methods and formulations for topical and buccal release. All the formulations proposed are based on natural and biocompatible polymer matrices such as gellan gum, scleroglucan and hydroxypropylmethylcellulose. The proposed formulations are tested by in vitro release tests. In fact they represents a valid support and a useful starting point for the realization of a potentially usable in-vivo pharmaceutical formulation that may have commercial utility. The research work is both experimental and theoretical. Each topic presents a more chemical-pharmaceutical part, based on the formulation preparation and release experiments, and a more theoretical-numerical approach that allows a correct interpretation and description of the experimental data obtained. Release from hydrogels and thin films require different modelling approaches. Also the physico-mathematical description of different release experiments (different release devices such as Franz cell, millifluidic device and USP II) requires different theoretical and numerical techniques. The outcome of an accurate model development is of fundamental importance for future design of pharmaceutical formulations with prescribed release properties. In addition the formulations are investigated through rheological, mechanical, thermoanalytic and mucoadhesive tests in order to have a more comprehensive picture of their practical utilization

TURBULENCE IN MOLECULAR CLOUDS

We generate random Gaussian turbulent velocity fields with a Kolmogorov spectrum and use these to obtain synthetic line-of-sight velocity profiles. The profiles are found to be similar to line profiles observed in molecular clouds. We suggest methods for analysing measured line profiles to test whether they might arise from Gaussian Kolmogorov turbulence.Comment: accepted in ApJ, compressed postscript, figures not included. Complete preprint available at http://ucowww.ucsc.edu/~dubinski/home.html or by request to [email protected]

Na Lawa (ni Qoli/The Fishing Net) Conceptual Framework and the Institutional Web

This paper uses an indigenous Fijian methodology, Na Lawa (ni Qoli) or The (Fishing) Net that takes a holistic and relational approach, integral to indigenous epistemologies. The “nodes” or knots in the lawa (net) represent traditional and/or modern concepts. The connected nodes represent a network of relationships. Each node represents concepts that can be researched and examined to clarify the connections and to highlight what is relevant to, or what impedes, ako/vuli/learning, and what adaptation or intervention might be needed to improve ako. Using as a grid the institutional web of the Vanua, church, and state centering on education, and knots in the lawa to identify issues affecting iTaukei children’s ako, the methodology offers a roadmap for researchers, academics, and policymakers as an overview. Identifying IT (Information Technology) as a problem, this paper uses Na Lawa methodology to demonstrate the application of the net and institutional web as a roadmap. To illustrate conceptual linkages and the social relations that make up the institutional web, the concept of “technology” is used to demonstrate how the web of relations to other conceptual nodes can be strengthened. Using the lawa as a grid to identify each node representing a concept, constructs are inferred, based on the institutional attributes and their contributory roles to strengthening of relationships that build on ako. The nodes are the “talking points” for participants to clarify and identify overlapping issues to research. The paper advocates a simultaneous effort by all institutions to strengthen relations between nodes to improve ako and reciprocal networking. Indeed, the voice of the community is essential in this approach

Differential expression and biochemical activity of the immune receptor Tim-3 in healthy and malignant human myeloid cells

The T cell immunoglobulin and mucin domain 3 (Tim-3) is a plasma membrane-associated receptor which is involved in a variety of biological responses in human immune cells. It is highly expressed in most acute myeloid leukaemia (AML) cells and therefore may serve as a possible target for AML therapy. However, its biochemical activities in primary human AML cells remain unclear. We therefore analysed the total expression and surface presence of the Tim-3 receptor in primary human AML blasts and healthy primary human leukocytes isolated from human blood. We found that Tim-3 expression was significantly higher in primary AML cells compared to primary healthy leukocytes. Tim-3 receptor molecules were distributed largely on the surface of primary AML cells, whereas in healthy leukocytes Tim-3 protein was mainly expressed intracellularly. In primary human AML blasts, both Tim-3 agonistic antibody and galectin-9 (a Tim-3 natural ligand) significantly upregulated mTOR pathway activity. This was in line with increased accumulation of hypoxia-inducible factor 1 alpha (HIF-1α) and secretion of VEGF and TNF-α. Similar results were obtained in primary human healthy leukocytes. Importantly, in both types of primary cells, Tim-3-mediated effects were compared with those induced by lipopolysaccharide (LPS) and stem cell factor (SCF). Tim-3 induced comparatively moderate responses in both AML cells and healthy leukocytes. However, Tim-3, like LPS, mediated the release of both TNF-α and VEGF, while SCF induced mostly VEGF secretion and did not upregulate TNF-α release