Magic Melters' Have Geometrical Origin

Recent experimental reports bring out extreme size sensitivity in the heat capacities of Gallium and Aluminum clusters. In the present work we report results of our extensive {\it ab initio} molecular dynamical simulations on Ga$_{30}$ and Ga$_{31}$, the pair which has shown rather dramatic size sensitivity. We trace the origin of this size sensitive heat capacities to the relative order in their respective ground state geometries. Such an effect of nature of the ground state on the characteristics of heat capacities is also seen in case of small Gallium and Sodium clusters indicating that the observed size sensitivity is a generic feature of small clusters.Comment: 4 pages, 6 figure

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

Effect of Cobalt Chloride on the Amino Acid Levels in Silk Gland of Silkworm, Bombyx mori L

The effect of cobalt on the total proteins, protease activity, free amino acids, alanine amino transferase (ALAT) activity and aspartate amino transferase (AAT) activity were studied. The increase of total protein content in silk gland may be either due to increased efflux or decreased proteolysis activity which might lead to accumulation of protein content. The decrease of protease activity level in silk gland may be due to lower rate of histolysis. The free amino acids showed a decrease in the silk gland of cobalt chloride treated larvae which indicates the faster mobilization of free amino acids into oxidative metabolism in the presence of cobalt chloride. The ALAT and AAT activity levels were elevated after cobalt chloride treatment indicating the active involvement in the protein synthesis. DOI: 10.17762/ijritcc2321-8169.15079

Biosorption of Arsenic (III) by Using Lemon Peel Powder as Low Cost Effective Biosorbent

The use of lemon peel powder, a novel, low-cost, and sustainable biosorbent derived from food waste, to remove arsenic has largely gone unexplored. The feasibility and viability of the As (III) biosorption abilities of lemon peel powder are compared in this study. The parameters such as contact time, pH, the amount of lemon peels used, the initial arsenic concentration, and temperature all had an effect on the sorption process. Thermodynamic, kinetic, and equilibrium were all evaluated. The optimal pH was 6.0, and it lasted until pH 8 with 72.34% removal efficiency. Lemon peel (LP) has a pH PZC value of 7 and a surface pH of 7. The analysis of kinetics revealed that the biosorption was regulated by a second-order reaction, as well as the fact that the catalytic region of the biosorbent was heterogeneous; however, the biosorption process was better defined by the Freundlich and Temkin isotherms. Finally, it is possible to remove arsenic (III) using waste content. Thermodynamic and equilibrium analysis have shown that sorption is a natural process that is spontaneous, beneficial, and endothermic. In addition, Fourier Transfer Infrared Spectroscopy (FTIR) research shows that arsenic reacts with metal oxides and the -OH functional group in lemon peel. These findings indicate that this peel can be used to remove arsenic from a simulated aqueous solution as a valuable, low-cost sorbent. This research lays the groundwork for the potential production of an effective filtration device that uses citrus peel powder as a low-cost, innovative, and long-lasting biosorbent to treat water polluted with arsenic (III). Keywords: Arsenic, Equilibrium, FTIR, Isotherms, Kinetic, PZC, Thermodynami DOI: 10.7176/JNSR/12-14-01 Publication date:July 31st 202

Ab initio Molecular Dynamical Investigation of the Finite Temperature Behavior of the Tetrahedral Au19_{19} and Au20_{20} Clusters

Density functional molecular dynamics simulations have been carried out to understand the finite temperature behavior of Au$_{19}$ and Au$_{20}$ clusters. Au$_{20}$ has been reported to be a unique molecule having tetrahedral geometry, a large HOMO-LUMO energy gap and an atomic packing similar to that of the bulk gold (J. Li et al., Science, {\bf 299} 864, 2003). Our results show that the geometry of Au$_{19}$ is exactly identical to that of Au$_{20}$ with one missing corner atom (called as vacancy). Surprisingly, our calculated heat capacities for this nearly identical pair of gold cluster exhibit dramatic differences. Au$_{20}$ undergoes a clear and distinct solid like to liquid like transition with a sharp peak in the heat capacity curve around 770 K. On the other hand, Au$_{19}$ has a broad and flat heat capacity curve with continuous melting transition. This continuous melting transition turns out to be a consequence of a process involving series of atomic rearrangements along the surface to fill in the missing corner atom. This results in a restricted diffusive motion of atoms along the surface of Au$_{19}$ between 650 K to 900 K during which the shape of the ground state geometry is retained. In contrast, the tetrahedral structure of Au$_{20}$ is destroyed around 800 K, and the cluster is clearly in a liquid like state above 1000 K. Thus, this work clearly demonstrates that (i) the gold clusters exhibit size sensitive variations in the heat capacity curves and (ii) the broad and continuous melting transition in a cluster, a feature which has so far been attributed to the disorder or absence of symmetry in the system, can also be a consequence of a defect (absence of a cap atom) in the structure.Comment: 7 figure

Molecular Exploration of Guava (Psidium guajava L.) Genome Using SSR and RAPD Markers: A Step towards Establishing Linkage Map

In the present study, molecular evaluation of two guava mapping populations (MP), MPI comprising 94 F1 progenies and MPII comprising 46 F1 progenies, was carried out using simple sequence repeat (SSR) and random amplified polymorphic DNA (RAPD) markers. A pseudo-test cross strategy was implemented where 'Kamsari' X 'Purple Local' and 'Purple Local' X 'Allahabad Safeda' were crossed, and, these showed variation in fruit quality traits such as seedstrength (hardness/softness), fruit weight, TSS and pulp color. A set of 30 RAPD markers was used for genotyping MPI while a set of 55 SSR markers was used for genotyping MPII. In case of MPI, 30 RAPD markers generated 214 scorable markers, of which 80 markers were specific to 'Kamsari', 14 markers to 'Purple Local' and the remaining 120 were intercross markers. As for MPII, 55 polymorphic SSR markers resulted in generation of 207 alleles (with a maximum of 4 alleles and a minimum of 3 alleles per locus), of which 108 alleles were specific to 'Purple Local' while 99 were specific to 'Allahabad Safeda'. Genotypic data thus generated can be further exploited for constructing genetic linkage maps and mapping complex QTLs governing fruit quality traits in guava.

Influence of Organic Manures and Fertilizers on Nutrient Uptake, Yield and Quality in Cabbage-Baby Corn Cropping Sequence

Field experiments were conducted at Acharya N.G. Ranga Agricultural University, Hyderabad, Andhra Pradesh, India, during rabi and kharif seasons of 2010 and 2011 to study direct, cumulative, or residual effect of organic manures (Farmyard Manure, Vermicompost, Poultry Manure, Neem Cake, and combinations thereof) along with the recommended dose of fertilizers (RDF) and absolute Control, on nutrient uptake, yield and quality in cabbage-baby corn cropping sequence system. Results showed that application of recommended dose of fertilizers [N, P and K (100:50:50 kg ha-1)] recorded highest yield in cabbage (38.91t ha-1), which was comparable to combined application (2.89t ha-1) of poultry manure and neem cake (37.9t ha-1). In baby corn, maximum yield (6.12t ha-1) was recorded with recommended dose of fertilizers, followed by the combined use of poultry manure and neem cake (5.80t ha-1). Among various treatments, residual effect and combined application of poultry manure and neem cake to a preceding cabbage crop, recorded maximum yield in baby corn (4.71t ha-1) over other treatments. Similar trend was seen in nutrient uptake by cabbage and baby corn (cumulative and residual). Highest protein and ascorbic acid content in cabbage, residual and cumulative baby corn was recorded with application of poultry manure + neem cake (2.89t ha-1), and poultry manure + FYM (6.11t ha-1) respectively

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

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