Formation of Gallium-induced nanostructures on single crystal HOPG surface

The room temperature growth of gallium atoms on the highly oriented pyrolytic graphite (HOPG) surface has been performed. The gallium atoms were deposited by thermal evaporation method in an ultra high vacuum system at a base pressure 5 × 10⁻¹⁰ torr. The X-ray photo electron spectroscopy (XPS) studies had been performed to confirm the presence of gallium atoms on HOPG surface. Scanning tunneling spectroscopy (STM) technique was employed to study the surface morphology of the clean HOPG surface and gallium covered HOPG surfaces which recognize the formation of gallium induced nanostructures. The deconvoluted XPS core level spectra of C (1s) and Ga (3d) demonstrate the possible interaction between substrate and the adsorbate atoms. The STM analysis revealed that the gallium deposition on HOPG led to significant change in the surface morphology. It was observed that the Ga atoms adsorbed as layer structure on HOPG surface for low coverage while quasi one-dimensional chain like nanostructure (1 ± 0.2 nm) has been formed for higher Ga coverage. The nanostructured surfaces induced by Ga deposition are found to be stable and could be used as a template for the growth of metallic nanostructures.     

Partial molar adiabatic compressibilities of transfer of some amino acids from water to aqueous lactose solutions at different temperatures

Apparent molar adiabatic compressibilities (K_{?, s}) of glycine, L-alanine, L-valine, and L-leucine have been determined in aqueous and mixed aqueous solutions of lactose (2 to 6 mass%) at T = (293.15, 298.15, 303.15, and 308.15) K. From these data partial molar adiabatic compressibilities at infinite dilution (K_{?, s}⁰) have been evaluated to calculate corresponding transfer function. The transfer partial molar adiabatic compressibilities at infinite dilution (ΔK_{?, s}⁰) are found to be positive. The decrease in the magnitude of transfer partial molar adiabatic compressibilities from glycine to L-leucine indicates the dominance of hydrophobic-hydrophobic interactions between the increasing side chains of amino acids. Also, the contributions of NH₃⁺COO⁻ , and CH₂ groups have been calculated by the linear correlation of K_{?, s}⁰ with number of carbon atoms in the alkyl chain of amino acids.     

Terpolymerization of p-acetylpyridine oxime, p-methylacetophenone and formaldehyde, and its thermal studies

A terpolymer resin involving p-acetylpyridine oxime and p-methylacetophenone with formaldehyde (APOMAF) was synthesized by condensation polymerization in the presence of an acid catalyst. The structure of terpolymer was elucidated by FT-IR, ¹H NMR, pyrolysis gas chromatography mass spectrometer (Py?CGC?CMS), nitrogen adsorption/desorption analysis, Ubbelohde viscometer and non-aqueous conductometric titration, TG?CDTG and DSC. Molar fractions of monomer, condensing and comonomer unit (m ₁, m ₂, and m ₃) in APOMAF using ¹H NMR analysis data were calculated as 1.67; 0.27 and 0.66?mol%, respectively. The apparent activation energy of terpolymer by using various degradation models including the Flynn?CWall?COzawa (FWO), Kissinger?CAkahira?CSunose (KAS), and Friedman methods were 140.3; 144.9 and 129.9?kJ?mol^?1, respectively. The results from isoconversional degradation kinetics and Pyrolysis (GC?CMS) indicates that the degradation mechanism of terpolymer are likely limited by at least two-reaction step, the first being associated with the loss of the pendent methyl, acetyl, and oxime groups (side group elimination) while the second mass loss being due to the degradation of the terpolymer backbone (random scission) which clearly indicates that grafting pendant groups to the terpolymer backbone yields polymers with lower thermal stability. From the calculation, the solid state thermal degradation mechanism is proposed to be D₃ (three-dimensional diffusion) at initial stage and F ₁ (Random nucleation with one nucleus on the individual particles) at final stage.     

Approximation of the supply scheduling problem

The supply scheduling problem consists in finding a minimum cost delivery plan from a set of providers to a manufacturing unit, subject to given bounds on the shipment sizes and subject to the demand at the manufacturing unit. We provide a fully polynomial time approximation scheme for this problem.     

Discrimination of bacteria from Jamaican bauxite soils using laser-induced breakdown spectroscopy

Soil bacteria are sensitive to ecological change and can be assessed to gauge anthropogenic influences and ecosystem health. In recent years, there has been a significant increase in the focus on new technologies that can be applied to the evaluation of soil quality. Laser-induced breakdown spectroscopy (LIBS) is a promising technique that has been used for the investigation and characterization of explosives, solids, liquids, gases, biological and environmental samples. In this study, bacteria from un-mined and a chronosequence of reclaimed bauxite soils were isolated on Luria–Bertani agar media. Polymerase chain reaction amplification of the bacterial 16S rDNA, sequencing, and phylogenetic analysis were applied to each isolated soil bacteria from the sample sites resulting in the identification and classification of the organisms. Femtosecond LIBS performed on the isolated bacteria showed atomic and ionic emission lines in the spectrum containing inorganic elements such as sodium (Na), magnesium (Mg), potassium (K), zinc (Zn), and calcium (Ca). Principal component analysis and partial least squares regression analysis were performed on the acquired bacterial spectra demonstrating that LIBS has the potential to differentiate and discriminate among bacteria in the un-mined and reclaimed chronosequence of bauxite soils.     

Supply network planning in the forest supply chain with bucking decisions anticipation

We consider a two-echelon timber supply chain in which the first echelon consists of several stands to be harvested and the second echelon consists of mills to be supplied with logs of different length. This problem aims at minimizing harvesting and transportation costs for one production period, while satisfying demand expressed as a mix of volumes of specific log types. Harvesting cost, which includes felling, bucking and hauling to roadside, depends upon the number of log type to be produced and sorted. Each stand to be harvested is modeled individually with a limited number of trees of various classes of diameter and total length, which affects the productivity factors of the bucking patterns to be used. To take these characteristics into account, we propose heuristics based on columns generation to solve the supply network problem at the forest level with an anticipation of bucking operations at the stand level.     

Use of graphite oxide and graphene oxide as catalysts in the synthesis of dipyrromethane and calix[4]pyrrole

Graphite oxide and graphene oxides have been used as solid catalysts for the synthesis of 5,5-dialkyldipyrromethanes and calix[4]pyrroles in organic and aqueous solutions at room temperature.     

Hamming weight distributions of multi-twisted codes over finite fields

Designs, Codes and Cryptography - Let $${\mathbb {F}}_q$$ denote the finite field of order q,  and let $$n = m_1+m_2+\cdots +m_\ell ,$$ where $$m_1,m_2,\ldots ,m_\ell $$ are arbitrary...