Nano-Materials and Nano-Technology

Nano, a Greek word , means dwarf. Science has, however, given this dwarf a numerical value of "one billionth". A nanometer is thus one billionth of a meter, or 10A°.As a very general definition , materials/structures with one or more physical dimensions having the size of some nano-meters are now called nano-materials/ nano-structures. The processes utilized to create such materials/structures, and technologies to exploit these to fabricate devices with/ without integration with suitable micro/ macro dimension materials/ structures /devices are termed as nanotechnologies. With increasing use of the word NANO in popular science and consumer applications, sub-micron size materials and devices arealso loosely included in the nano-categories. Nano-materials are low dimensional materials which are classified by physicists as zero, one, or two dimensional, depending on whether three, two, or one dimensions are small enough in size (which is of course relative to the size of the probe entities) so that classical laws of physics are not applicable with confidence. Some typical examples of low dimensional materials and devices are listed in the following

Mutagenesis: investigating the process and processing the outcome for crop improvement

The discoveries during the late 1920s that the genetic material is amenable to changes excited geneticists who saw new opportunities for both basic and practical applications. During the 1950s, induced mutagenesis was widely pursued in the US, Europe, Japan and China. In India, Swaminathan and his team at the Indian Agricultural Research Institute, New Delhi initiated a major programme on mutagenesis in crop plants. These studies were broadly aimed at understanding the process of mutation, testing the efficacy of various mutagens, identifying optimum dose and the best method of treatment for different crop species; isolation of mutants of basic and applied value; elucidating the biological effects of radiation-treated media, seeds and vegetative propagules on the organisms consuming them

"Nothing new": responses to the introduction of antiretroviral drugs in South Africa.

Interviews conducted in South Africa found that awareness of antiretroviral therapy was generally poor. Antiretroviral drugs were not perceived as new, but one of many alternative therapies for HIV/AIDS. Respondents had more detailed knowledge of indications, effects and how to access alternative treatments, which is bolstered by the active promotion and legitimization of alternative treatments. Many expressed a lack of excitement about the introduction of antiretroviral therapy, and little change in their attitudes concerning the epidemic

Magnetoresistance of atomic-sized contacts: an ab-initio study

The magnetoresistance (MR) effect in metallic atomic-sized contacts is studied theoretically by means of first-principle electronic structure calculations. We consider three-atom chains formed from Co, Cu, Si, and Al atoms suspended between semi-infinite Co leads. We employ the screened Korringa-Kohn-Rostoker Green's function method for the electronic structure calculation and evaluate the conductance in the ballistic limit using the Landauer approach. The conductance through the constrictions reflects the spin-splitting of the Co bands and causes high MR ratios, up to 50%. The influence of the structural changes on the conductance is studied by considering different geometrical arrangements of atoms forming the chains. Our results show that the conductance through s-like states is robust against geometrical changes, whereas the transmission is strongly influenced by the atomic arrangement if p or d states contribute to the current.Comment: Revised version, presentation of results is improved, figure 2 is splitted to two figure

Construction and commissioning of the tracker module for the SuperNEMO experiment

The SuperNEMO experiment will search for neutrinoless double-beta decay in the Modane Underground Laboratory. This decay mode, if observed, confirms that neutrinos are Majorana fermions. It would be a new lepton violating process, and would provide a measurement of the absolute neutrino mass. The SuperNEMO experiment is designed to reach a half-life sensitivity of 1026 years corresponding to an effective Majorana neutrino mass of 50−100 meV. The SuperNEMO demonstrator module is the first stage of the experiment, containing 7kg of 82Se, with an expected sensitivity of T½ (0ν) > 6.5×1024 y after 2.5 years. Full topological event reconstruction is achieved through the use of a wire tracker operating in Geiger mode combined with scintillator calorimeter modules. Construction of the demonstrator module is well underway. We present the design of the tracker, and the current status of the construction and commissioning efforts

Sorption of Water & Some Straight- & Branched-chain Aliphatic Alcohols by Casein

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Broad boron sheets and boron nanotubes: An ab initio study of structural, electronic, and mechanical properties

Based on a numerical ab initio study, we discuss a structure model for a broad boron sheet, which is the analog of a single graphite sheet, and the precursor of boron nanotubes. The sheet has linear chains of sp hybridized sigma bonds lying only along its armchair direction, a high stiffness, and anisotropic bonds properties. The puckering of the sheet is explained as a mechanism to stabilize the sp sigma bonds. The anisotropic bond properties of the boron sheet lead to a two-dimensional reference lattice structure, which is rectangular rather than triangular. As a consequence the chiral angles of related boron nanotubes range from 0 to 90 degrees. Given the electronic properties of the boron sheets, we demonstrate that all of the related boron nanotubes are metallic, irrespective of their radius and chiral angle, and we also postulate the existence of helical currents in ideal chiral nanotubes. Furthermore, we show that the strain energy of boron nanotubes will depend on their radii, as well as on their chiral angles. This is a rather unique property among nanotubular systems, and it could be the basis of a different type of structure control within nanotechnology.Comment: 16 pages, 17 figures, 2 tables, Versions: v1=preview, v2=first final, v3=minor corrections, v4=document slightly reworke

Discrimination between two mechanisms of surface-scattering in a single-mode waveguide

Transport properties of a single-mode waveguide with rough boundary are studied by discrimination between two mechanisms of surface scattering, the amplitude and square-gradient ones. Although these mechanisms are generically mixed, we show that for some profiles they can separately operate within non-overlapping intervals of wave numbers of scattering waves. This effect may be important in realistic situations due to inevitable long-range correlations in scattering profiles.Comment: 5 pages, 3 figure