Synthesis, hydration and durability of rice hull cements doped with chromium

This work describes the synthesis, hydration and durability behavior of β-Ca(2)SiO(4) doped with chromium. β-Ca(2)SiO(4) is a component of commercial cement. Rice hull is an agricultural residue containing about 10% of silica as inorganic constituent. The controlled burning of rice hull was used to obtain this biogenic silica, used as starting material. In many situations chromium is added during cement preparation in order to promote encapsulation, at temperatures around 1500°C. The synthesis presented here is completed at 800°C, causing a substantial reduction in energy consumption. Moreover, chromium is chemically bonded to cement crystal, which is safer than simple physical encapsulation. Results show that chromium can be inserted into the structure of β-Ca(2)SiO(4) up to 1% (molar ratio). Hydration degree and durability studies show that insertion of chromium causes no deleterious effects on physical and chemical properties of these doped materials when compared to β-pure Ca(2)SiO(4).     

The performance of rolling production schedules in a process industry

In this paper we study lot-sizing and changeover decisions in production schedules that are implemented on a rolling-horizon basis. The study is carried out by comparing production schedules for the packaging operations of a pharmaceutical company that produces various products on several capacitated production lines. The schedules are obtained by solving a mixed-integer programming formulation by using a heuristic procedure. We examine the effects of the number of periods in the planning horizon, the starting inventory and the demand fluctuation on the schedules. We show empirically that the saving in annual production cost diminishes rapidly as more demand periods are added to the planning horizon. Computational results are reported.     

The histamine releasers crotamine, protamine and compound 48/80 activate specific proteases and phospholipases A2

Crotamine, a basic, myonecrotic, histamine-releasing neurotoxin, was isolated from Crotalus durissus terrificus venom. Carboxypeptidase A was shown to be activated by crotamine when acting upon N-carbobenzoxyglycil-L-phenylalanine. However the activity of carboxypeptidase B upon the substrate hippuryl-L-arginine was not enhanced by this toxin. Teh basic histamine releasers protamine and compound 48/80 also activated carboxypeptidase A. These three agents activated both alpha-chymotrypsin when acting upon acetyl-L-tyrosine ethyl ester and also five snake venom phospholipase-like myotoxins acting upon egg yolk phosphatidylcholine. These findings suggest that the action of these agents during histamine release may involve the participation of specific intermediary hydrolases which, upon activation, would enhance their cytolytic effects on the sequence of events which lead to granule extrusion and histamine release from mast cells.     

Quantitative determination of physical and chemical measurands in honey by near-infrared spectrometry

Fourier transform near-infrared spectroscopy (FT-NIR) was evaluated to quantitatively determine 24 different measurands in honey. The reference values of 421 honey samples of different botanical origins were determined by classical physical and chemical methods. Partial least squares regression was used to develop the calibration models for the measurands studied. These calibrations were then validated using independent samples and proved satisfying accuracies for the determination of water (standard error of prediction: 0.3 g/100 g), glucose (1.3 g/100 g), fructose (1.6 g/100 g), sucrose (0.4 g/100 g), total monosaccharide content (2.6 g/100 g) as well as fructose/glucose ratio (0.09) and glucose/water ratio (0.12). The prediction accuracy for hydroxymethylfurfural, proline, pH-value, electrical conductivity, free acidity and the minor sugars maltose, turanose, nigerose, erlose, trehalose, isomaltose, kojibiose, melezitose, raffinose, gentiobiose, melibiose, maltotriose was poor and unreliable. The results demonstrate that near-infrared spectrometry is a valuable, rapid and non-destructive tool for the quantitative analysis of some measurands related to the main components in honey.     

A model study for release of plasticizers from polymer films through vapor phase

A model has been applied to release of plasticizers from polymer films through vapor phase, for which the overall rate of release may be generally determined by evaporation of the plasticizer from the surface of the film, and/or by migration to the surface at below saturation in the polymer. The experimental system employed made use of n-butyl formate, diethyl-phthalate, di-n-butylphthalate, and N,n-butylbenzenesulfonamide as model molecules in polycaprolactam films, both with the aims of studying undesirable loss of plasticizers, and of simulating a model able to envisage releasing, at a constant rate, of any desired additive, with relatively high solubility and vapor pressure, to the content of packaging films. Experimental measurements were made (at 298–333 K) by investigating in a suitable cell the permeation of plasticizers both at concentrations below and above the saturation limit. Rate of evaporation of plasticizers from the membrane surface above the saturation limit, measured in this cell, were found to coincide satisfactorily with those calculated by application of the mass transfer theory to evaporation from a stationary liquid into a stirred gas, at a known velocity of gas flowing past the surface. From these latter rates and solubilities, the mass transfer coefficients H for evaporation could be obtained, as well as from experimental time lags the diffusivities D_p through the polymer membrane. In the light of the theoretical model a correlation was found between activation energies of H and evaporation enthalpies of the model molecules.     

Azoic dyes derived from 1-aryl-5-methyl-3-hydroxypyrazoles

The potentialities for 1-aryl-5-methyl-3-hydroxypyrazoles as intermediates in the field of dyes have been analysed. Some azoic derivatives have been synthesized and both electronic spectra and tinctorial properties on various substrates (wool, nylon, polyester, plasticized PVC) examined. The effect of substituents on the position of the long wavelength absorption maxima is discussed in terms of Hammett σ constants and interesting relationships are obtained. For each application the most important technical properties are assessed and significant fastness to various agents is evaluated.Finally a comparison with properties of similar pyrazol-5-one derivatives is made.     

DNA damage by PAH and repair in a marine sponge

The sponge Tethya lyncurium from the Northern Adriatic has been used as an experimental species.A method is outlined for preparation of DNA which yields a highly purified DNA with a double-strand (ds) molecular weight of 25 M-dalton between single-strand (ss) breaks, which when properly damaged can be cut opposite to ss-breaks with nuclease s₁. The molecular weights of the resulting ds-DNA pieces and their distribution has been evaluated by electron microscope photographs.Sponges exposed to benzo[a]pyrene (BaP) in the dark only incorporate BaP-derivatives (BaPD) in small amounts, if any. However, in the presence of light, derivatization to BaP derivatives enables effective coupling to occur, as shown previously (R. K. Zahn et al., 1981). Sponges were exposed to radiolabeled BaP in the presence of light. Coupling of BaPD to the DNA as well as the induction of ss-breaks were measured.Light-mediated coupling is concentration dependent from 0.01 – 20 ppb BaP with a correlation coefficient of r = 0.84.Under conditions of possible repair, ss-breaks completely disappear from sponge DNA in the course of three weeks while a substantial fraction of the BaP derivatives persists.Double label experiments show that substantial DNA synthesis occurs during this time. Pollution causes a decrease of the molecular weight of unnicked DNA, re-incubation in clean water an increase. A DNA species of 24 M-dalton seems to play a critical role. If its percentage in the DNA population drops below a critical level, recovery is not longer possible. DNA damage by PAH and repair in sponges seems to differ from that of most eucaryotes.     

The normal spectral emittance of erbium,dysprosium and samarium above 1000 K

An apparatus for measuring the normal spectral emittance (λ = 0.645 μ.) of metals with very high vapor pressures has been designed and used for erbium, dysprosium and samarium at temperatures above 1000 K. The samples are maintained in an argon atmosphere at a pressure slightly above atmospheric pressure. The measured normal spectral emittances are: Erbium, (solid), ∈ _nλ = 0.372 ± 0.011; (liquid), ∈ _nλ = 0.372 ± 0.011; Dysprosium, (solid), ∈ _nλ = 0.631 – 1.889 × 10^–4 T (deg K); (liquid), ∈ _nλ = 0.297 ± 0.088; Samarium, (solid), ∈ _nλ = 0.437 ± 0.030; (liquid, estimated), ∈ _nλ = 0.437 ± 0.03. TERRY S. KING, formerly Undergraduate Research Helper. DORAB N. BARIA, formerly NSF Presidential Intern and Post-Doctoral Fellow. Prepared for the Energy Research and Development Administration under Contract No. W-7405-eng-82.     

Effect of surface conditions on the normal spectral emittance of titanium and zirconium between 1000 and 1800 K

The normal spectral emittance of Ti and Zr was obtained in the temperature range 1100 to 1800 K and wavelength 0.645 μ for electrochemically polished, mechanically polished and 60 grit ground surfaces at a pressure below 10^-8 mm Hg. The emittance at the melting point of both metals was obtained by extrapolation of an empirical equation fitted to the experimental data obtained for the electrochemically polished surface and was found to be in good agreement with reported values. The considerable grain growth on the surface affected the emittance. The emittance was found to increase with temperature up to 1300 K and then decreased with further increase in temperature. Formarly a National Science Foundation Presidential Intern and an Ames Laboratory-USAEC Postdoctoral Fellow, Iowa State University, Ames, Iowa.     

Photochemical grafting of acrylated azo dyes onto polymeric surfaces,IV. Grafting of 4-(N-ethyl-N-2-acryloxyethyl)amino-4′-nitro-azobenzene onto cellulose

Photochemically induced grafting and graft-polymerization of 4-(N-ethyl-N-2-acryloxyethyl)amino-4′-nitro-azobenzene I , brought into contact in the solid state with cellulose by evaporation of solvent from monomer solutions, has been investigated kinetically at 30°C. Two constant rate periods were observed. The first one was interpreted on the basis of a self-sensitized grafting mechanism of monomeric or oligomeric species of I , photochemically initiated by hydrogen abstraction from the cellulose surface. The second one was explained as a self-sensitized photochemically induced graft-polymerization of I on the first grafted layer. Some particular features, such as concurrent photodegradation of the first grafted layer at low surface coverage, are discussed in the light of the proposed mechanism.