Graft polymerization of acrylic monomers onto starch fractions. III. Effect of carbohydrate structure

Grafted PMMA was isolated by the acid hydrolysis method. Weight-average and number-average molecular weights were determined by gel permeation chromatography. The number-average molecular weight of the grafted chains was about 475,000 for amylopectin and 403,000 for amylose. The number of grafted chains (mmol) ranged from 2.4 × 10^?3 to 4.6 × 10^?3 for amylopectin graft copolymers and from 2.9 × 10^?3 to 6.8 × 10^?3 for those of amylose. These results were related to others obtained from ceric ion consumption studies. The values suggest that amylopectin, because of its complex structure, favors a higher consumption of ceric ion in homopolymerization reactions and inhibits the initiation reactions of the copolymerization.     

The principles and theory of high-speed titrations by flow injection analysis

The highly reproducible concentration gradients formed between an injected sample zone and the carrier stream in flow injection analysis are exploited for titrations based on measuring the time span between points of identical gradient dispersion. Comparison of the experimental data with theoretical models, has made it possible to locate the position and physical dimension of a single mixing stage, which at medium dispersion of the sample zone allows the entire titration cycle, including sampling and washout periods, to be completed within less than 30 s. The capability of this high-speed titration technique is demonstrated for acid—base, compleximetric and iodimetric titration procedures.     

The normal coordinate analysis of hydrogen bonded adducts of chloroacetic acids with dimethyl sulphoxide

The modified valence force field and the potential energy distribution were calculated for adducts of mono-, di-, and trichloroacetic acids with dimethyl sulphoxide. The calculated force constants gave a good fit to the experimental frequencies of normal adducts and their OD and CD₃ analogues. The hydrogen bond strength increases from mono- to trichloroacetic acid and this is reflected in the decrease of the K_O-H force constant and increase of k_O?h.     

Oxygen reduction on electrode surfaces modified by foreign metal ad-atoms: Lead ad-atoms on gold

Oxygen reduction on gold is considerably catalysed by foreign metal ad-atoms. The catalytic effects of lead have been studied in more detail as most illustrative. The two-electron reduction of O₂ to HO₂^? on Au changes into a four-electron process on Au modified by lead. In the potential region where AuOH constitutes the surface, the interaction of Pb ions with AuOH causes catalytic effects. At more negative potentials, on bare Au surface, the underpotential deposition of Pb ad-atoms gives rise to the catalytic effects.At AuOH surface modified by Pb ions the O₂ reduction involves a “series” mechanism, with only minute quantities of HO₂^? leaving the electrode surface. The reduction of HO₂^? is considerably catalysed. The mechanism of this reaction is changed from the rate-determining chemical step into the charge-transfer rate-determining step. The rate-determining step for O₂ reduction involves the first charge transfer: O₂+e→O₂^?(ads)The mechanism of HO₂^? formation is uncertain, while its reduction most probably involves a direct process. There are indications that on Au surface with Pb ad-atoms a “parallel” mechanism may be operative.The catalytic effect originates in the interaction of Pb²⁺ with AuOH surface, which considerably reduces a partial negative charge on OH. Such a surfaces, as well as that of Au covered by Pb ad-atoms, are more suitable for adsorption of O₂, O₂^? and HO₂^? which considerably alters the free energy of adsorption of these species.     

Flow injection analysis : Part IV. Stream sample splitting and its application to the continuous spectrophotometric determination of chloride in brackish waters

The rapid determination of chloride in water samples based on spectrophotometric measurement of iron(III)thiocyanate has been adapted to Flow Injection Analysis. The simple manifold allows a routine sampling rate of 300 samples/hour, and evidence is presented that 500 samples/hour are possible. For increased accuracy in the measurement of samples of widely varying chloride content, the sample is split in the reagent stream so that the relevant absorbance of the split sample zones varies from 1:2 to 1:10 allowing expansion of the analytical range without loss of accuracy.     

Simple and quick rotational temperature determination in N2-containing discharge plasma

A quick spectroscopic method of rotational temperature determination based on the low-resolution emission spectrum of the N₂ (v=2v=()) vibronic band profile of the second positive system iras developed. The new method of molecular gas temperature determination was used in an rf glow discharge excited in N₂ and N₂ + Ar + B₂ H₆ gas mixture at u pressure range 500–13011 Pa. This method of molecular gas temperature measurement is applicable to nonisothermic plasmas used in plasma-chemical reactors.     

The effects of strawberry tree (Arbutus unedo L.) water leaf extract and arbutin upon kidney function and primary DNA damage in renal cells of rats

Abstract

Although strawberry tree (Arbutus unedo L.) leaves have long been used as a herbal remedy, insufficient information is available on their nephrotoxicity. We assessed the safety of strawberry tree water leaf extract and its key component arbutin, administered per os to Lewis rats of both genders at 200?mg/kg b.w./day for 14 and 28 days. The effects of the tested compounds on DNA integrity in renal cells was evaluated using alkaline comet assay, while kidney function was studied using serum creatinine and urea levels. Strawberry tree water leaf extract showed high biocompatibility with kidney tissue. It did not impair DNA integrity of renal cells and kidney function, either in male or female rats. However, exposure to single arbutin affected the levels of primary DNA damage in renal cells which could be related to metabolic conversion of arbutin into hydroquinone, whose nephrotoxicity has previously been proven.     

Spectrofluorometric trace determination of cerium(III) in sodium hexametaphosphate solutions

The use of sodium hexametaphosphate in the spectrofluorometric determination of trace amounts of cerium(III) ions is described. Sodium hexametaphosphate acts as a specific reagent for enhancing the fluorescence intensity of cerium(III) in aqueous solutions. The apparent excitation and fluorescence wavelength used are 304 and 344 nm, respectively. Maximum fluorescence intensity is obtained by irradiating Ce(III) dissolved in 5.346 g/l sodium hexametaphosphate solution at room temperature. The fluorescence varies linearly with the concentration of cerium(III) in the range of 0.001-60 microg/ml. The coefficient of variation for 45 microg/ml Ce(III) in 5.346 g/l sodium hexametaphosphate solution is 1. The quenching effects of other lanthanides and some inorganic anions are given. This technique permits a direct and rapid determination of cerium(III) in rare earth mixtures and cerium concentrates.     

Born-Floquet theory of electron-atom collisions in the presence of a laser field

We present a theory of fast electron-atom collisions in the presence of a strong laser field, which treats the interaction of the laser field with both the projectile electron and the target atom in a fully non-perturbative way. The theory is illustrated by considering the laser-assisted “elastic” scattering of fast electrons by atomic hydrogen, for non-resonant as well as resonant cases.     

Time-energy uncertainty and relativistic canonical commutation relations in quantum spacetime

It is shown that the time operatorQ ⁰ appearing in the realization of the RCCR's [Q,P^v]=–jhg^v, on Minkowski quantum spacetime is a self adjoint operator on Hilbert space of square integrable functions over _m =×v _m , where is a timelike hyperplane. This result leads to time-energy uncertainty relations that match their space-momentum counterparts. The operators Q appearing in Born's metric operator in quantum spacetime emerge as internal spacetime operators for exciton states, and the condition that the metric operator should possess a ground exciton state assumes the significance of achieving minimal spacetime4-momentum uncertainty in fundamental standards for spacetime measurements.Supported in part by NSERC research grant No. A5206.