Zirconium Incorporation into CaTiO3 Perovskite Prepared from Xerogels and Implication for the Fate of (Ca,Sr)TiO3 Nuclear Waste Ceramics

CaTiO₃ perovskite has been proposed as a ceramic waste form for immobilization of ⁹⁰Sr. Nonradioactive coprecipitated xerogel powders with nominal atomic ratios of Ca:Zr:Ti = 0.75:0.25:1.00 were synthesized to mimic the fate of (Ca_0.75⁹⁰Sr_0.25)TiO₃ solid solution after complete decay of the Sr and its intermediate product Y to stable Zr when an excess B⁴⁺ (Ti and ⁹⁰Zr) cations will present. Ca:Ti = 1.00:1.00 samples were used as a reference. The powders were heated to various conditions to explore the thermodynamic stability of its oxides. The heated Ca:Zr:Ti = 0.75:0.25:1.00 samples formed a major orthorhombic Ca(Zr_1?xTi_x)O₃ perovskite phase. The Ti/(Ti + Zr) ratio of the perovskite preserves its nominal ratio at 600°C. The Zr rejects from the Ca(Zr_1?xTi_x)O₃ with further increasing the temperature, following the formation of Ca–Ti–Zr–O secondary phases. This study indicates a tendency of the Zr to segregate from an original (Ca,Sr)TiO₃ waste form when the stoichiometry is controlled by the conversion of Sr to Zr (in normal oxidation states).     

De‐esterification pattern of Valencia orange pectinmethylesterases and characterization of modified pectins

BACKGROUND: Pectinmethylesterase (PME, E.C. 1.1.11) isozymes from Valencia orange preparations with different specific activities were used to de‐esterify citrus and sugar beet pectins. Enzymatic modification offers the opportunity to create pectins of tailored functionality and gelling ability. RESULTS: Based on nuclear magnetic resonance spectra, catalysis by all PME extracts produced block‐wise de‐esterification patterns in both citrus and sugar beet pectins. PME activity resulted in increased numbers of contiguous de‐esterified groups and decreased numbers of contiguous esterified groups. De‐esterification by PMEs increased the elastic property (G′) of citrus and sugar beet pectins in the presence of calcium from 10 to 571 and from 0.05 to 201 Pa, respectively. CONCLUSIONS: The results demonstrate the predilection of citrus PMEs toward block wise de‐esterification of pectins and the relationship between calcium binding ability and de‐esterification degree and patterning. Within a narrow range of de‐esterification (37–48%) and with a narrow distribution of contiguous groups, PME modification did not markedly change gelling ability. At lower or higher de‐esterification values, a 2‐fold increase or 50‐fold decrease, respectively in G′ values was observed. Copyright © 2008 Society of Chemical Industry     

The Diurnal Rhythms in Plasma Glycine Pool Sizes and Turnover Rates: 15N-Glycine Single Dose Experiments Employing Gas Chromatographic — Mass Spectrometric Analysis

Gas liquid chromatography–mass spectrometry of trifluoroacetyl n-butyl ester derivatives of plasma amino acids has been used to determine directly the ¹⁵N-enrichment of plasma glycine in rabbits, following the intravenous administration of a single dose of ¹⁵N-glycine. The isotope enrichment time decay curves of plasma glycine were linear over the course of the measurements (5–45 min). Glycine pool sizes and turnover rate constants were obtained from the intercepts and slopes of non weighted least-squares lines, describing the isotope enrichment time decay curve. In fed animals, glycine pool sizes showed only modest variations over a 24 h period, while glycine turnover rate constants showed a statistically significant daily variation with a minimum at 10 PM. In fasted animals, the glycine pool sizes decreased and turnover rate constants increased with the duration of the fast. The turnover rate constants appeared to represent the utilization of glycine, as an energy or nitrogen source in the liver, rather than uptake of glycine into the free amino acid pool of muscle. These data indicate that physiologically significant variations in amino acid dynamics can be obtained from single dose tracer experiments, when GC-MS is used to determine directly the isotope enrichments of plasma amino acids.     

Chemical and structural characterization of bacterially-derived casein peptides that impair milk clotting

Milk-clotting parameters are highly affected by hydrolysis of casein. Previously, it was shown that products of the hydrolysis of casein impair milk clotting, affecting both clotting time and curd firmness. One of these fractions is of particular interest since it is produced exclusively by enzymes of Streptococcus dysgalactiae. The present study aims to further investigate the chemical and structural properties of this fraction in an attempt to understand its influence on milk clotting. Preparations of this fraction, obtained from either S. dysgalactiae-infected glands or ex vivo inoculations with the same bacteria, were found to be identical. Mass spectrometry and Edman degradation analyses indicate that it comprises primarily β-CN^83–209, generated by cleavage at a Val-Val peptide bond, presumably by bacterial thermolysin- or elastin-like proteases. A model offering a putative mechanism for interference with milk-clotting parameters through production of this fraction is presented.     

Photochemistry of α,α′-Disubstituted Azoalkanes. I. Photosolvolytic Inversion and Substitution of α,α′-Dichloro- and α,α′-Dialkoyloxyazoalkanes

A series of α,α′-dichloro (α DClA), α,α′-dialkoyloxy- (αDAlA) and α,α′-dibenzoxy-azoalkanes (αDBeA) without α-aryl substituents was found to undergo meso ? dl photointerconversion upon direct irradiation through Pyrex in the presence of oxygen in a number of solvents. Furthermore, irradiation of α,α′-dipropionoxy-azoalkanes in benzene in the presence of excess acetic acid leads to substitution of the propionoxy groups by acetoxy groups in addition to meso ? dl photointerconversion. Similar irradiation in the presence of CH₃CO₂D does not lead to deuterium substitution of the β-hydrogens. The presence of benzenethiol radical scavenger does not affect the course of these photoreactions. Photosolvolysis schemes involving heterolysis (in the case of αDAlA and αDBeA) or an unstable intermediate (in the case of αDClA) are proposed.     

Efficient Set Intersection with Simulation-Based Security

We consider the problem of computing the intersection of private datasets of two parties, where the datasets contain lists of elements taken from a large domain. This problem has many applications for online collaboration. In this work, we present protocols based on the use of homomorphic encryption and different hashing schemes for both the semi-honest and malicious environments. The protocol for the semi-honest environment is secure in the standard model, while the protocol for the malicious environment is secure in the random oracle model. Our protocols obtain linear communication and computation overhead. We further implement different variants of our semi-honest protocol. Our experiments show that the asymptotic overhead of the protocol is affected by different constants. (In particular, the degree of the polynomials evaluated by the protocol matters less than the number of polynomials that are evaluated.) As a result, the protocol variant with the best asymptotic overhead is not necessarily preferable for inputs of reasonable size.     

Inter-relationships between acidic and alkali treatments of cotton straw and wheat straw and their fibre chemical properties

The amount of lignin in the cell walls of cotton straw (CS) and wheat straw (WS) was found to be the same, but the ratio between lignin and hemicellulose was considerably lower in CS than in WS. In CS the amount of soluble acid lignin was less than 1% of the total lignin, whereas in WS it was 20%. The amount of phenolics in concentrated sulphuric acid (72%) hydrolysates of the cell wall was reduced drastically in WS compared with the amount released by diluted (1 N) sulphuric acid; this may have been due to polymerisation of low-molecular-size lignin. The amount of alkali-soluble lignin in WS was 3–7 times greater than in CS. Following acid treatment the amount of alkali-soluble lignin was reduced from 20% of the total content to 5% in WS, and from 5% to 1% in CS. Enzymic hydrolysis was 49% higher in WS cell wall than in CS cell wall. In WS, acidic and alkali pretreatments followed by cellulase treatment increased glucose yield from cellulose by 260% and 280%, respectively. In CS, acidic pretreatment did not affect the glucose yield from cellulose, whereas alkali treatment increased it by 35%.     

Microstructural enhancement of high coercivity L1(0)-FePt films for next-generation magnetic recording media

The effects of substrate Ar-ion milling and Ta adhesion layer on the microstructural and magnetic properties of L1(0)-FePt films prepared on Si, SiO2, and glass substrates were investigated. It was discovered that the relatively large in-plane surface roughness of CrRu/MgO/FePt films deposited on Si substrates was due to the deformation of the CrRu layer when the composition was heated to 550 degrees C. More than an order of magnitude improvement for the in-plane surface roughness was achieved when substrate Ar-ion milling or Ta adhesion layer was incorporated into the process. While the Ta adhesion layer proved to be detrimental to the (200) growth of the CrRu layer, optimal FePt film properties with coercivity values larger than 2 Tesla and out-of-plane roughness less than 1 nm were achieved when only substrate Ar-ion milling was implemented.