Introducing a twist in carbon nanotubes

A simple model based on rotational distortion of carbon atoms between adjacent layers running perpendicular to the tube axis, without altering the hexagonal motifs is proposed for constructing coiled carbon nanotubes

Computational identification and characterization of putative miRNAs in Nasonia species

MicroRNAs are important at post transcriptional regulation in eukaryotes. Nasonia genus is becoming increasingly popular model in present days due to genetic advantages it possesses over Drosophila. Nasonia species are found distributed throughout the world, expect for N. longicornis, and N. giraulti. In this study, we use the sequential method of blasting all known invertebrate miRNA genes against the Nasonia vitripennis, Nasonia longicornis, and Nasonia giraulti genomes. We identify 40, 31 and 29 putative pre-​miRNAs and mature sequences in N. vitripennis, N. giraulti and N. longicornis resp. A cross species comparison of putative miRNA sequences and their statistical characteristics reveals that there are no huge differences between the species, except for few miRNAs which are reported. We also find that the minimal folding energy index for three Nasonia species pre-​miRNA's av. is around -​0.85 ± 0.11. Further, we report that U is predominant at the 5' end of mature sequence, which being a typical characteristic of plant miRNAs. Using MiRanda, we predict nearly 471 potential sites in the N. vitripennis genome. Thus concluding our study to be the beginning of understanding the Nasonia's non coding RNAs and may play an important role in effective pest management in near future

Structure and stability of spiro-cyclic water clusters

The structure and stability of spiro-cyclic water clusters containing up to 32 water molecules have been investigated at different levels of theory. Although there exist minima lower in energy than these spiro-cyclic clusters, calculations at the Hartree-Fock level, density functional theory using B3LYP parametrization and second order Møller-Plesset perturbation theory using 6-31G∗ and 6-311++G∗∗ basis sets show that they are stable in their own right. Vibrational frequency calculations and atoms-inmolecules analysis of the electron density map confirm the robustness of these hydrogen bonded clusters

Three-dimensional time-dependent quantum mechanical study of the reaction He+H<SUB>2</SUB><SUP>+</SUP>&#8594;HeH<SUP>+</SUP>+H

We report the results of a three-dimensional time-dependent quantum mechanical study of the reaction He+H2+ (&#957;=0,1)&#8594;HeH++H at &lt;Etrans&gt;=1.0 eV, which reproduces clearly the vibrational enhancement for the system. In addition, preliminary results for He+HD+ (&#957;=1-3) suggest the preferential formation of HeD+ over HeH+ in the products

Pattern formation in Passiflora incarnata: An activator-inhibitor model

Based on a careful examination of the onset of violet colored dots along the filaments in the developing floral bud stage and the formation of alternating bands of violet and white color in the matured flowers of Passiflora incarnata (Passion flower), it is concluded that the pattern arises from a competition between the production of violet colored anthocyanin and the colorless flavonols along the filaments. The activator-inhibitor model of Gierer and Meinhardt along with the reaction diffusion theory of Turing is used to explain the formation of concentric rings in the flower

An improved continuous compositional-spread technique based on pulsed-laser deposition and applicable to large substrate areas

A new method for continuous compositional-spread (CCS) thin-film fabrication based on pulsed-laser deposition (PLD) is introduced. This approach is based on a translation of the substrate heater and the synchronized firing of the excimer laser, with the deposition occurring through a slit-shaped aperture. Alloying is achieved during film growth (possible at elevated temperature) by the repeated sequential deposition of sub-monolayer amounts. Our approach overcomes serious shortcomings in previous in-situ implementations of CCS based on sputtering or PLD, in particular the variations of thickness across the compositional spread and the differing deposition energetics as function of position. While moving-shutter techniques are appropriate for PLD-approaches yielding complete spreads on small substrates (i.e. small as compared to distances over which the deposition parameters in PLD vary, typically about 1 cm), our method can be used to fabricate samples that are large enough for individual compositions to be analyzed by conventional techniques, including temperature-dependent measurements of resistivity and dielectric and magnetic and properties (i.e. SQUID magnetometry). Initial results are shown for spreads of (Sr,Ca)RuO$_3$.Comment: 6 pages, 8 figures, accepted for publication in Rev. Sci. Instru

Quantum chemical investigation of the reaction of O(<SUP>3</SUP>P<SUB>2</SUB>) with certain hydrocarbon radicals

The reaction of ground-state atomic oxygen [O(3P2)] with methyl, ethyl, n-propyl and isopropyl radicals has been studied using the density functional method and the complete basis set model. The energies of the reactants, products, reaction intermediates and various transition states as well as the reaction enthalpies have been computed. The possible product channels and the reaction pathways are identified in each case. In the case of methyl radical the minimum energy reaction pathway leads to the products CO + H2 + H. In the case of ethyl radical the most facile pathway leads to the products, methanal + CH3 radical. For propyl radical (n- and iso-), the minimum energy reaction pathways would lead to the channel containing ethanal + methyl radical

Preparation of YBCO Films on CeO 2 -Buffered (001) YSZ Substrates by a Non-Fluorine MOD Method

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66369/1/j.1551-2916.2004.01669.x.pd

Computed Rotational Collision Rate Coefficients for Recently Detected Anionic Cyanopolyynes

We report new results from quantum calculations of energy-transfer processes taking place in interstellar environments and involving two newly observed molecular species: C$_5$N$^-$ and C$_7$N$^-$ in collision with He atoms and the p-H$_2$ molecules. These species are part of the anionic molecular chains labeled as cyanopolyynes which have been observed over the years in molecule-rich Circumstellar Envelopes and in molecular clouds. In the present work, we first carry out new $ab$ $initio$ calculations for the C$_7$N$^-$ interaction potential with He atom and then obtain state-to-state rotationally inelastic cross sections and rate coefficients involving the same transitions which have been observed experimentally by emission in the interstellar medium (ISM) from both of these linear species. For the C$_5$N$^-$/He system we extend the calculations already published in our earlier work (see reference below) to compare more directly the two molecular anions. We extend further the quantum calculations by also computing in this work collision rate coefficients for the hydrogen molecule interacting with C5N$^-$, using our previously computed interaction potential. Additionally, we obtain the same rate coefficients for the C$_7$N$^-$/H$_2$ system by using a scaling procedure that makes use of the new C$_7$N$^-$/He rate coefficients, as discussed in detail in the present paper. Their significance in affecting internal state populations in ISM environments where the title anions have been found is analyzed by using the concept of critical density indicators. Finally, similarities and differences between such species and the comparative efficiency of their collision rate coefficients are discussed. These new calculations suggest that, at least for the case of these longer chains, the rotational populations could reach local thermal equilibrium conditions within their observational environments

Effect of parabolic solar energy collectors for water distillation

This research article briefly summarizes the augmentation of condensate output using concentrators. This study compares a single-slope solar still, a compound conical concentrator (CCC) solar still, and a compound parabolic concentrator–tubular solar still (CPC–TSS). The effect of miniaturization of the absorber (increase in the concentration factor) and some modifications in the solar still assembly show a remarkable increase in output. The measured daily yield rate per square meter of absorber area of the single slope solar still, CCC solar still, and CPC–TSS is 2,100, 18,000, and 6,100 ml, respectively. It was found that the CCC solar still provides the maximum yield