Finite Temperature Behavior of Small Silicon and Tin Clusters: An Ab Initio Molecular Dynamics Study

The finite temperature behavior of small Silicon (Si$_{10}$, Si$_{15}$, and Si$_{20}$) and Tin (Sn$_{10}$ and Sn$_{20}$) clusters is studied using isokinetic Born-Oppenheimer molecular dynamics. The lowest equilibrium structures of all the clusters are built upon a highly stable tricapped trigonal prism unit which is seen to play a crucial role in the finite temperature behavior of these clusters. Thermodynamics of small tin clusters (Sn$_{10}$ and Sn$_{20}$) is revisited in light of the recent experiments on tin clusters of sizes 18-21 [G. A. Breaux et. al. Phys. Rev. B {\bf 71} 073410 (2005)]. We have calculated heat capacities using multiple histogram technique for Si$_{10}$, Sn$_{10}$ and Si$_{15}$ clusters. Our calculated specific heat curves have a main peak around 2300 K and 2200 K for Si$_{10}$ and Sn$_{10}$ clusters respectively. However, various other melting indicators such as root mean square bond length fluctuations, mean square displacements show that diffusive motion of atoms within the cluster begins around 650 K. The finite temperature behavior of Si$_{10}$ and Sn$_{10}$ is dominated by isomerization and it is rather difficult to discern the temperature range for transition region. On the other hand, Si$_{15}$ does show a liquid like behavior over a short temperature range followed by the fragmentation observed around 1800 K. Finite temperature behavior of Si$_{20}$ and Sn$_{20}$ show that these clusters do not melt but fragment around 1200 K and 650 K respectively.Comment: 9 figure

Yield potential and economics of rabi sorghum (Sorghum bicolor L.) as influenced by different crop residues and green biomass composts

A field experiment was conducted on vertisols at Organic Farming Research Institute, University of Agricultural Sciences, Raichur coming under northern Karnataka during rabi season of 2015-16 to study the yield potential (q ha-1 ) and economics of rabi sorghum (Sorghum bicolor L.) as influenced by different crop residues and green biomass composts. The experiment consisted of fifteen treatments, of which twelve treatments were based on nitrogen supply though different composts, one recommended dose of fertilizer, one recommended organic and inorganic fertilizers and another was absolute control. Significantly higher grain yield (39.9 q ha-1 ) and stover yield (13.2 tha1 ) was recorded with application of FYM @ 3 t ha-1 + RDF (50:25 N:P2O5 kg ha-1 )followed by recommended NP fertilizers (T13: 37.2 q ha-1 ) and Cotton stalks +Redgram stalks + Glyricidiasp. with C: N ratio of 30:1 compost @ 50 kg N equivalent (T12: 36.6 q ha-1 ). The lowest grain yield was recorded with absolute control (T15: 18.4 q ha-1 ). Significantly higher B:C (3.08) was recorded with RDF(50:25 N:P2O5 kg ha-1 ) + FYM @ 3 t ha-1 application followed Cotton stalks +Redgram stalks + Glyricidia sp. with C: N ratio of 30:1 compost @ 50 kg N equivalent (T12:2.90) over other treatments. Application of recommended FYM @ 3 t ha-1 15 days before sowing along with 50 kg of nitrogen and 25 kg of phosphorus per hectare at the time of sowing recorded higher dry matter production, grain and stover yield and net returns and benefit: cost ratio

Density functional investigation of the interaction of acetone with small gold clusters

The structural evolution of Aun (n = 2, 3, 5, 7, 9, and 13) clusters and the adsorption of organic molecules such as acetone, acetaldehyde, and diethyl ketone on these clusters are studied using a density functional method. The detailed study of the adsorption of acetone on the Aun clusters reveals two main points. (1) The acetone molecule interacts with one gold atom of the gold clusters via the carbonyl oxygen. (2) This interaction is mediated through back donation mainly from the spd-hybridized orbitals of the interacting gold atom to the oxygen atom of the acetone molecule. In addition, a hydrogen bond is observed between a hydrogen atom of the methyl group and another gold atom (not involved in the bonding with carbonyl oxygen). Interestingly, the authors notice that the geometries of Au9 and Au13 undergo a significant flattening due to the adsorption of an acetone molecule. They have also investigated the role of the alkyl chain attached to the carbonyl group in the adsorption process by analyzing the interaction of Au13 with acetaldehyde and diethyl ketone

Influence of varied crop residues and green biomass composts to rabi sorghum growing soils on uptake of major nutrients, microbial biomass and soil fertility status

A field experiment was conducted on vertisols (pH of 7.56 with organic carbon content of 0.55%) at Re- search Institute on Organic Farming, University of Agricultural Sciences, Raichur coming under northern Karnataka during rabi season of 2015-16 to study the Influence of varied crop residues and green biomass composts to rabi sorghum growing soils on uptake of major nutrients, organic carbon and soil fertility status. In general application of Cotton stalks, Redgram stalks, Glyricidia, combination of cotton and redgram stalks composts, FYM and combina- tion of organic and inorganic fertilizers helped to buildup soil nutrients with respect to organic carbon, available nitro- gen and phosphorus. Significantly higher nitrogen (227.3 kg ha-1), phosphorous (75.7 kg ha-1) and potassium (141.7 kg ha-1) uptake by rabi sorghum was recorded with combined application of recommended FYM (3 t ha-1) and NP fertilizers (50:25 kg N, P2O5 ha-1) (T14) followed by Cotton stalks +Redgram stalks + Glyricidia sp. with C:N ratio of 30:1 compost @ 50 kg N equivalent (T12: 222.0, 74.0 and 132.3 kg ha-1). The least uptake was recorded with abso- lute control (T15: 127.0, 42.0 and 71.7 kg ha-1). Similar trend was observed with organic carbon, available nitrogen and phosphorus. Combined application of recommended FYM (3 t ha-1) and NP fertilizers (50:25 kg N, P2O5 ha-1) followed by Cotton stalks +Redgram stalks + Glyricidia sp. with C:N ratio of 30:1 compost @ 50 kg N equivalent at the time of sowing recorded higher major nutrients uptake, microbial biomass and soil fertility status

The string model of the Cooper pair in the anisotropic superconductor

The analogy between the Cooper pair in high temperature superconductor and the quark-antiquark pair in quantum chromodynamics (QCD) is proposed. In QCD the nonlinear chromodynamical field between a quark and an antiquark is confined to a tube. So we assume that there is the strong interaction between phonons which can confine them to some tube too. This tube is described using the nonlinear Schr\"odinger equation. We show that it has an infinite spectrum of axially symmetric (string) solutions with negative finite linear energy density. The one-dimensional nonlinear Schr\"odinger equation has a finite spectrum (hence, it has a steady-state) which describes the Cooper pair squezeed between anisotropy planes in the superconductor. It is shown that in this model the transition temperature is approximately 45 K.Comment: final version, Latex, 9p, to be published in Phys. Rev.

DFT-based Conformational Analysis of a Phospholipid Molecule (DMPC)

The conformational space of the dimyristoyl phosphatidylcholine (DMPC) molecule has been studied using Density Functional Theory (DFT), augmented with a damped empirical dispersion energy term (DFT-D). Fourteen ground-state isomers have been found with total energies within less than 1 kcal/mol. Despite differences in combinations of their torsion angles, all these conformers share a common geometric profile, which includes a balance of attractive, repulsive and constraint forces between and within specific groups of atoms. The definition of this profile fits with most of the structural characteristics deduced from measured NMR properties of DMPC solutions. The calculated vibrational spectrum of the molecule is in good agreement with experimental data obtained for DMPC bilayers. These results support the idea that DMPC molecules preserve their individual molecular structures in the various assemblies.Comment: 31 pages, 6 Tables, 4 Figure

Size--sensitive melting characteristics of gallium clusters: Comparison of Experiment and Theory for Ga17+_{17}{}^{+} and Ga20+_{20}{}^{+}

Experiments and simulations have been performed to examine the finite-temperature behavior of Ga$_{17}{}^{+}$ and Ga$_{20}{}^{+}$ clusters. Specific heats and average collision cross sections have been measured as a function of temperature, and the results compared to simulations performed using first principles Density--Functional Molecular--Dynamics. The experimental results show that while Ga$_{17}{}^{+}$ apparently undergoes a solid--liquid transition without a significant peak in the specific--heat, Ga$_{20}{}^{+}$ melts with a relatively sharp peak. Our analysis of the computational results indicate a strong correlation between the ground--state geometry and the finite--temperature behavior of the cluster. If the ground--state geometry is symmetric and "ordered" the cluster is found to have a distinct peak in the specific--heat. However, if the ground--state geometry is amorphous or "disordered" the cluster melts without a peak in the specific--heat.Comment: 6 figure

Somatically Hypermutated Plasmodium-Specific IgM+ Memory B Cells Are Rapid, Plastic, Early Responders upon Malaria Rechallenge

SummaryHumoral immunity consists of pre-existing antibodies expressed by long-lived plasma cells and rapidly reactive memory B cells (MBC). Recent studies of MBC development and function after protein immunization have uncovered significant MBC heterogeneity. To clarify functional roles for distinct MBC subsets during malaria infection, we generated tetramers that identify Plasmodium-specific MBCs in both humans and mice. Long-lived murine Plasmodium-specific MBCs consisted of three populations: somatically hypermutated immunoglobulin M+ (IgM+) and IgG+ MBC subsets and an unmutated IgD+ MBC population. Rechallenge experiments revealed that high affinity, somatically hypermutated Plasmodium-specific IgM+ MBCs proliferated and gave rise to antibody-secreting cells that dominated the early secondary response to parasite rechallenge. IgM+ MBCs also gave rise to T cell-dependent IgM+ and IgG+B220+CD138+ plasmablasts or T cell-independent B220−CD138+ IgM+ plasma cells. Thus, even in competition with IgG+ MBCs, IgM+ MBCs are rapid, plastic, early responders to a secondary Plasmodium rechallenge and should be targeted by vaccine strategies

A localised chlorophyll deficiency associated with male sterility in Nicotiana tabacum L.

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