Discrete Dirac Operators in Clifford Analysis

We develop a constructive framework to define difference approximations of Dirac operators which factorize the discrete Laplacian. This resulting notion of discrete monogenic functions is compared with the notion of discrete holomorphic functions on quad-graphs. In the end Dirac operators on quad-graphs are constructed.     

Synthesis of somatostatin

A tetradecapeptide with the proposed structure of growth hormone release inhibiting factor was synthesized by a classical fragment approach.     

QCD/string holographic mapping and high-energy scattering amplitudes

We find a one-to-one mapping between low-energy string dilaton states in AdS bulk and high-energy glueball states on the corresponding boundary. This holographic mapping leads to a relation between bulk and boundary scattering amplitudes. From this relation and the dilaton action we find the appropriate momentum scaling for high-energy QCD amplitudes at fixed angles.     

Benchtop methods for measuring the fraction of free liquid of biomass slurries

The free-liquid fraction of slurries is strongly correlated with other slurry properties, especially the rheological and transport properties. Measuring free-liquid fraction can be problematic with lignocellulosic materials, and many studies to-date have instead used the total mass-fraction of liquid as a surrogate measure. This study presents two bench-scale methods for determining the free-liquid content of lignocellulosic biomass slurries. One is based on centrifuge-filtration of biomass for increasing time intervals until an asymptote is observed. The other uses solute exclusion methods and includes a proper accounting for unavoidable adsorption of the tracer solute molecules on the biomass solids. Overall, we found both methods gave reasonable results for washed pretreated corn stover. Among our controls, the centrifuge dewatering method tends to enable better results for large, rigid particles, and can give unrealistic results for small, compressible particles. This tendency is also reflected in the results for different pretreated corn stover slurries, where the quality of the results varied with the particle size distribution of the slurries. The solute exclusion method gives physically realistic results for all of our control materials and for washed pretreated materials, but produced physically unrealistic results for one unwashed pretreated corn stover sample. Further, we show that blue dextran interacts chemically with lignocellulosic material via adsorption and suspected degradation reactions.     

Determination of Glycerol in Biodiesel Using a Nickel(II) Oxyhydroxide Chemically Modified Electrode by Cyclic Voltammetry

A glassy carbon electrode chemically modified with nickel oxyhydroxide from a nickel hexacyanoferrate (NiHCF) film was used to determine glycerol in biodiesel by cyclic voltammetry. The modified electrode exhibited a linear response to glycerol concentration in the range from 0.05 to 0.35 mmol L^?1, and a detection limit of 0.030 mmol L^?1. The glycerol concentration found in the biodiesel sample was 0.156 mmol L^?1. The method developed in this study showed a recovery of (100.3±5.0)%.     

Biomass Photochemistry. V. Modifications of Lignin by Photochemical Treatment and Its Chemiluminescence

Lignin modifications resulting from different photochemical pre-treatments were studied using chemiluminescent methods. In the oxidation of lignin in NaOH solutions at 25°C, the intensity increased with increasing temperature and can be described by an Arrheniustype exponential equation with an activation energy of 25.8 ± 2.7 kJ/ mol. The oxidation of lignin model compounds under these conditions indicated ¹O₂ OH′, and O₂ generation. Chemiluminescence of the luminol/H₂O₂/Fe²⁺ system was used to study decomposition products of lignin upon irradiation. Unirradiated lignin proved to be an excellent radical trap, an effect initially abolished upon irradiation. At longer irradiation times, however, the radical trapping behavior was restored. The action of the perodidase/H₂ O₂ system onlignin was also investigated using chemiluminescence. Behavior very similar to that using luninol was observed. The intensity increases with increasing time of irradiation up to an optimum value. More prolonged irradiation results in total quenching of the cheiluminescemce. This is indicative of depolymerization and posterior aggregation.     

Room‐Temperature Formation Pathway for CdTeSe Alloy Magic‐Size Clusters

Little is known about the pathway of room‐temperature formation of ternary CdTeSe magic‐size clusters (MSCs) obtained by mixing binary CdTe and CdSe induction period samples containing binary precursor compounds (PCs) of MSCs, monomers (Ms), and fragments (Fs). Also, unestablished are dispersion effects that occur when as‐mixed samples (without incubation) are placed in toluene (Tol) and octylamine (OTA) mixtures. The resulting ternary MSCs, exhibiting a sharp optical absorption peak at 399 nm, are labelled CdTeSe MSC‐399, and their PCs are referred to as CdTeSe PC‐399. When the amount of OTA is relatively small, single‐ensemble MSC‐399 evolved without either binary CdTe or CdSe MSCs. When the OTA amount is relatively large, CdTe MSC‐371 appeared initially and then disappeared, while single‐ensemble MSC‐399 developed more deliberately. The larger the OTA amount, the more slowly these changes proceeded. The substitution reaction of CdTe PC + CdSe M/F?CdTeSe PC‐399 + CdTe M/F is proposed to be rate‐determining for the MSC‐399 formation in a Tol and OTA mixture. This study provides further understanding of the transformation pathway between MSCs.     

Determination of Trace Levels of Mercury in Effluents and Wastewaters

Abstract

Concern about mercury pollution of the environment and the inapplicability of natural water methods necessitated development of a procedure for determining parts per billion mercury in effluents and wastewaters containing large amounts of organic matter. The sample is digested with sulfuric and nitric acids to destroy the organic matter, and the ionic mercury is reduced to the elemental state by stannous ion. Then the digestate is aerated with a stream of air to carry the mercury vapor through a heated line into a quartz cell positioned in an atomic absorption spectrophotometer for measurement. Analyses of effluents and aqueous samples gave good recoveries of added mercury. Effluents, wastewaters, water supplies and aqueous samples secured within manufacturing plants have been analyzed. With minor modification, the procedure has been applied to manufacturing materials such as vinylpyri-dine, latex, sizing, dyes, caustic, and hydro.