Computer experiment on propagation of solitons in crystals

Molecular dynamics computer simulation was carried out for homogeneous one-dimensional crystals and Langmuir–Blogett chain crystals. A mass-spring model was used, and the anharmonic interatomic potential up to the fourth order was taken into account. The total number of atoms was 120, and an end of the crystal was free to move and the other end fixed. An input pulse was applied to a couple of free end atoms, and the displacements and kinetic energies of all atoms in the crystal were computed. Solitons and phonons were produced, propagated and reflected at the ends of the crystal. Long-period propagation of stable solitons was observed in homogeneous crystals and in one-layer LB chain crystals.     

Modeling of the Complex Doping Dependence of dTc/dP of YBa2Cu3O6+x

The pressure-induced intrinsic effects in the CuO₂ plane within the van Hove singularity (VHS) scenario is combined with the modified two-dimensional (2D) lattice gas phenomenology for the basal plane to model the complex structure of the hole-doping dependence of the pressure derivatives of T _c of YBa₂Cu₃O_6+x . The experimentally observed structure is found to be reproduced reasonably satisfactorily in the present formalism. This shows that the pressure-induced changes in the CuO₂ plane and the oxygen ordering in the basal plane both play important roles in explaining the doping dependent pressure derivative of T _c .     

The NIP Genes in Sugar Beet: Underlying Roles in Silicon Uptake and Growth Improvement

Silicon - Silicon (Si) can stimulate plant growth and stress resistance. This study aimed at elucidating the physiological responses and molecular characterization of different NIP (nodulin 26-like...     

Molecular dynamics simulations of homogeneous condensation and thermophysical properties of HFO1123 and its binary blends with HFC134a at 273.15 K to 298.15 K

Journal of Mechanical Science and Technology - The hydrofluoroolefin (HFO) refrigerant R1123 (1,1,2-trifluoroethene) and its blends with R134a are excellent alternative choices for refrigeration...     

Brittle–ductile transition of double network hydrogels: Mechanical balance of two networks as the key factor

Tough double network (DN) hydrogels are a kind of interpenetrating network (IPN) gels with a contrasting structure; they consist of a rigid and brittle 1st network with dilute, densely cross-linked short chains and a soft and ductile 2nd network with concentrated, loosely cross-linked long chains. In this work, we focus on how the brittle gel changes into a tough one by increasing the amount of ductile component. By comparing the molecular structures of the individual first network and second network gels, we found that the true key mechanical factor that governs the brittle–ductile transition is the fracture stress ratio of the two networks, σ_f,2/σ_f,1. This ratio is related to the density ratio of elastically effective polymer strands of the two networks, ν_e,2/ν_e,1, where the inter-network topological entanglement makes dominant contribution to ν_e,2. When ν_e,2/ν_e,1 < k = 3.8−9.5, the second network fractures right after the fracture of the first network, and the gels are brittle. When ν_e,2/ν_e,1 > k, only the first network fractures. As a result, the brittle first network serves as sacrificial bonds, imparting toughness of DN gels. The study also confirms that the load transfer between the two networks is via inter-network topological entanglement. This result provides essential information to design tough materials based on the double network concept.     

Screening of arsenic in tubewell water with field test kits: evaluation of the method from public health perspective

There is an urgent need for Bangladesh to identify the arsenic (As) contaminated tubewells (TWs) in order to assess the health risks and initiate appropriate mitigation measures. This will involve testing water in millions of TWs and raising community awareness about the health problems related to chronic As exposure from drinking water. Field test kits offer the only practical tool within the time frame and financial resources available for screening and assessment of the As contaminated TWs as well as their monitoring than that of the laboratory measurement. A comparison of field test kit and laboratory measurements by AAS as "gold standard" for As in water of 12,532 TWs in Matlab Upazila in Bangladesh, indicates that the field kit correctly determined the status of 91% of the As levels compared to the Bangladesh Drinking Water Standard (BDWS) of 50 microg/L, and 87% of the WHO guideline value of 10 microg/L. Nevertheless, due to analytical and human errors during the determination of As by the field test kits, some misclassification of wells is inevitable. Cross-checking of the field test kit results, both by Field Supervisor and by the laboratory analyses reveal considerable discrepancies in the correct screening mainly at As concentration ranges of 10-24.9 microg/L and 50-99.9 microg/L, critical from a public health point of view. The uncertainties of misclassification of these two groups of TWs have severe public health implications due to As exposure from drinking water sources. This can be reduced through proper training of the field personnel, cross verification of the field test kit results with laboratory analyses and further development of the field test kits to determine As at low concentrations.     

Status of biodiesel research and development in Pakistan

Performance of biodiesel in engines is well established and biodiesel is currently adjudged as a low carbon fuel with the most potential of replacing fossil fuels. The fossil fuel sources are dwindling in Pakistan resulting in importation of about 8.1 million tonnes at approximately US$ 9.4 billion per annum. In the ambit of this justification, augmenting the energy scarce resources in Pakistan through intense harnessing of the varied biodiesel sources can adequately address the deficiency and can ensure energy security. Towards this end, the progress attained in biodiesel related researches in Pakistan are evaluated and presented with the view of highlighting ways of achieving the target set by the Government. A feedstock that drew less attention is spent triglycerides, and the little work reported by some organizations appeared promising. Now the onus is upon organizations such as the Alternative Energy Development Board and Pakistan State Oil to harness the research results from several indigenous Universities and develop a full-scale biodiesel economy in Pakistan.     

Fabrication of nano patterns on various substrates using nanosphere lithography technique

This paper presents a procedure for fabricating large-area, size-tunable, metal arrays with a periodically different shape using Nanosphere Lithography (NSL). This technique has attracted considerable interest because of its important applications as diffraction devices, chemical and optical data recording. Their ordered arrays can be used for anti-reflection surfaces, bio-sensors and nanopatterning masks. Two different types of patterns, honeycomb and hexagonal patterns, could be fabricated on various substrates with different procedures. All steps for making different patterns employed a PS (polystyrene) monolayer by spin coating. Honeycomb patterns were fabricated by spin coating a PS monolayer on a glass substrate and depositing a metal followed by removal of the monolayer, whereas the hexagonal pattern was produced by the transfer of a gold deposited monolayer onto a GaN substrate using the same process. These processes allow simple and excellent control of the size and shape of the patterns. All experimental results on structure characterization and determination of the nanoparticle metrics were accomplished by atomic force microscopy and field emission-scanning electronic microscopy.     

In Situ Loading of Basic Fibroblast Growth Factor Within Porous Silica Nanoparticles for a Prolonged Release

Basic fibroblast growth factor (bFGF), a protein, plays a key role in wound healing and blood vessel regeneration. However, bFGF is easily degraded in biologic systems. Mesoporous silica nanoparticles (MSNs) with well-tailored porous structure have been used for hosting guest molecules for drug delivery. Here, we report an in situ route to load bFGF in MSNs for a prolonged release. The average diameter (d) of bFGF-loaded MSNs is 57 ± 8 nm produced by a water-in-oil microemulsion method. The in vitro releasing profile of bFGF from MSNs in phosphate buffer saline has been monitored for 20 days through a colorimetric enzyme linked immunosorbent assay. The loading efficiency of bFGF in MSNs is estimated at 72.5 ± 3%. In addition, the cytotoxicity test indicates that the MSNs are not toxic, even at a concentration of 50 μg/mL. It is expected that the in situ loading method makes the MSNs a new delivery system to deliver protein drugs, e.g. growth factors, to help blood vessel regeneration and potentiate greater angiogenesis.