bluuebunny/crossref_metadata_2025_split huggingface dataset:
A numerical evaluation of SAR distribution and temperature changes around a metallic plate in the head of a RF exposed worker
Authors: McIntosh Robert L. , Anderson Vitas , McKenzie Raymond J. 
Published: May 2005

AbstractThe 1998 International Commission for Non‐Ionising Radiation (ICNIRP) Guidelines for human exposure to radiofrequency (RF) fields contain a recommendation to assess the potential impact of metallic implants in workers exposed up to the allowable occupational field limits. This study provides an example of how numerical electromagnetic (EM) and thermal modelling can be used to determine whether scattered RF fields around metallic implants in workers exposed to allowable occupational ambient field limits will comply with the recommendations of relevant standards and guidelines. A case study is performed for plane wave exposures of a 50 mm diameter titanium cranioplasty plate, implanted around 5–6 mm under the surface of the forehead. The level of exposures was set to the ambient power flux density limits for occupational exposures specified in the 1998 ICNIRP guidelines and the current 1999 IEEE C95.1 standard over the frequency range 100–3000 MHz. Two distinct peak responses were observed. There was a resonant response for the whole implant at 200–300 MHz where the maximum dimension of the implant is around a third of the wavelength of the RF exposure. This, however, resulted in relatively low peak specific energy absorption rate (SAR) levels around the implant at the exposure limits. Between 2100–2800 MHz, a second SAR concentrating mechanism of constructive interference of the wave reflected back and forth between the air‐scalp interface and the scalp‐plate interface resulted in higher peak SARs that were within the allowable limits for the ICNIRP exposures, but not for the IEEE C95.1 exposures. Moreover, the IEEE peak SAR limits were also exceeded, to a lesser degree, even when the implant was not present. However, thermal modelling indicated that the peak SAR concentrations around the implant did not result in any peak temperature rise above 1 °C for occupational exposures recommended in the ICNIRP guidelines, and hence would not pose any significant health risk. Bioelectromagnetics 26:377–388, 2005. © 2005 Wiley‐Liss, Inc.
The effect of buffers and chelators on the reaction of luminol with Fenton's reagent near neutral pH
Authors: Bottu G. 
Published: May 2005

AbstractThe chemiluminescence of the system luminol +Fe2+ + H2O2 was measured in aqueous buffer at pH 7.2. In veronal (5,5‐diethybarbiturate) buffer, the luminescence is strongly quenched by ethanol and mannitol, but only weakly by t‐butanol, benzoate and superoxide dismutase (SOD); complexing Fe2+ with 1,10‐phenanthroline or 2,2′‐dipyridyl causes a decrease of light production that can be partially obviated by the simultaneous addition of SOD. In phosphate buffer, the luminescence is higher than in veronal and it is efficiently quenched by all four OH · quenchers and by SOD. In Tris buffer, no light production is observed as long as the Fe2+ is not complexed. When Fe2+ is complexed by pyrophosphate or phytate, there is a strong chemiluminescence in all three buffers, which is quenched by all four OH · quenchers and by SOD. When Fe2+ is complexed by EDTA or DTPA, very little luminescence is observed. The luminol analogue phthalhydrazide, which was suggested by Merényi and Lind as a reliable OH · detector, can replace luminol only in phosphate buffer, and thus turns out to be very specific indeed for free OH ·.
Detection of substances with alcoholic or phenolic hydroxyl groups by generation of hydrogen peroxide with imidazole and peroxyoxalate chemiluminescence
Authors: Nozaki Osamu , Iwaeda Toshinao , Kato Yoshio 
Published: May 2005

AbstractOn‐line detection of substances with an alcoholic or phenolic hydroxyl group using imidazole and peroxyoxalate chemiluminescence was investigated qualitatively using a flow‐injection method. The substances tested included six polyphenols, five monophenols and six sugars. After incubation at 80°C with an imidazole buffer (pH 9.5) the substances were detected by peroxyoxalate chemiluminescence. The polyphenols tested (e.g., pyrogallol, purpurogallin, and dopamine) showed the strongest light emission. The sugars with hydroxyl groups (e.g., fructose and lactose) and the monophenols (e.g., phenol, serotonin, and β‐estradiol) produced only a weak light emission. Reaction of hydroxyl compounds and imidazole generated hydrogen peroxide. Imidazole served two roles, it catalysed the reaction with the hydroxyl compound and initiated peroxyoxalate chemiluminescence on‐line. A novel reactor formed by packing glass beads into a flow cell (Teflon) of a chemiluminometer improved the sensitivity of light detection.
Chemiluminescence sandwich enzyme immunoassay for determination of human granulocyte colony stimulating factor (G‐CSF)
Authors: Aoyagi Shigeo , Arasawa Kazue , Matsuyuki Akira , Kamatchi Shin‐ichi , Fukushima Masafumi , Ohsawa Nakaaki 
Published: May 2005

AbstractA chemiluminescence sandwich enzyme immunoassay, using a glucose oxidase (GO) label, was developed for detecting attomole amounts of human granulocyte colony stimulating factor (G‐CSF). Purified goat F(ab′)2 immobilized on a bead and purified goat Fab′ labelled with GO were selected in combination with a chemiluminescent detection system comprising luminol and ferricyanide. The detection limits for G‐CSF were 4amol/assay (1 pg/mL) in buffer solution and 10 amol/assay (2.5 pg/mL) in human serum. Coefficients of variation within assay and between assay ranged from 5.5% to 7.8% and from 3.4% to 16.0%, respectively. The G‐CSF content of serum from normal healthy individuals was measurable using this method. G‐CSF in 24 normal human sera showed a mean value of 19.3 pg/mL and ranged from 3.6 to 83.0 pg/mL.
Flow injection analysis of riboflavin with chemiluminescence detection using a N‐halo compounds–luminol system
Authors: Safavi A. , Karimi M. A. , Nezhad M. R. Hormozi 
Published: May 2005

AbstractA chemiluminescent method for the determination of riboflavin is described. The method is based on the chemiluminescence (CL) generated during the oxidation of luminol by N‐bromosuccinimide (NBS) and N‐chlorosuccinimide (NCS) in alkaline medium. It was found that riboflavin could greatly enhance this CL intensity when present in the luminol solution. Based on this observation, a new flow‐injection CL method for the determination of riboflavin is proposed in this paper. The detection limits were 7.5 ng[sol ]mL and 3.5 ng[sol ]mL of riboflavin for the NBS– and NCS–luminol CL systems, respectively. The relative CL intensity was linear, with riboflavin concentration in the range 19–600 ng[sol ]mL and 600–2000 ng[sol ]mL for the NBS–luminol CL system, and 12–200 ng[sol ]mL and 200–2000 ng[sol ]mL for the NCS–luminol CL system. The results obtained for the assay of pharmaceutical preparations compared well with those obtained by the official method and demonstrated good accuracy and precision. Copyright © 2005 John Wiley & Sons, Ltd.
A new on‐line micellar‐enhanced photochemically‐induced fluorescence method for determination of phenylurea herbicide residues in water
Authors: Irace‐Guigand Sandrine , Leverend Emilie , Seye Mame Diabou Gaye , Aaron Jean Jacques 
Published: May 2005

AbstractA new flow injection analysis micellar‐enhanced photochemically induced fluorescence (FIA–MEPIF) method was developed for the determination of four phenylurea herbicides, including isoproturon, néburon, linuron and diuron. On‐line photoconversion under UV irradiation of these herbicides into strongly fluorescent photoproducts was performed in buffered aqueous solutions and in the presence of surfactants [sodium dodecyl sulphate (SDS) or cetyl trimethyl ammonium chloride (CTAC)] at micellar concentrations. The MEPIF and FIA parameters were optimized. The analytical figures of merit for the determination of the four herbicides were satisfactory, with concentration linear dynamic ranges over about one to two orders of magnitude, detection limits of 0.33–0.92 mg[sol ]L and relative standard deviations of 1.3–11%, according to the compound. Application to the analysis of fortified tap water samples yielded good recovery values (91–103%, according to the herbicide). Our results show that the on‐line MEPIF–FIA method is simple, versatile, sensitive and can be easily applied to quantify pollutant residues in multiresidue systems. Copyright © 2005 John Wiley & Sons, Ltd.
Study on the effect of thiamine on the metabolism of yeast by intrinsic fluorescence
Authors: Wang Jun , Cai Ruxiu , Xu Jing , Liu Zhihong 
Published: May 2005

AbstractThiamine in living human bodies exists mainly as diphosphate, which works as a co‐enzyme of the sugar metabolism system (active vitamin B1). Thiamine deficiency brings many clinically significant problems, such as dysphoria, quadriplegia and dyspepsia. Intrinsic fluorescence has an advantage over the extrinsic fluorescence of an unperturbed environment during investigation, especially in complex systems such as biological cells and tissues. Cellular fluorescence provides a sensitive index of the functional state of a living cell (1). Different amounts of thiamine were added to culture medium and the fluorescence of tryptophan and NADH from yeast was determined. When the thiamine concentration was greater than 0–0.16 µg[sol ]mL, the intensity of tryptophan fluorescence increased linearly, whereas the NADH fluorescence decreased. When the thiamine concentration was above 0.24 µg[sol ]mL, the fluorescence of tryptophan and NADH was almost unchanged. We concluded that low thiamine concentration in culture medium had a large effect on the growth of Saccharomyces cerevisiae and possible reasons are discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Determination of DNA base compositions from melting profiles in dilute buffers
Authors: Owen R. J. , Hill L. R. , Lapage S. P. 
Published: May 2005

AbstractEquations were determined for the dependency of the melting temperature (Tm) of DNA upon the logarithm of the sodium ion concentration, for four DNA samples of widely different base compositions (θGC). The slopes of these Tm versus log M equations wore found to decrease with increasing θG Cof the samples. An empirical equation relating Tm, log M (Na+) and θG C was derived, which also accounts for differences in Tm versus log M slopes. Data from the literature for some synthetic polynucleotides and for the crab(Cancer pagarus) satellite poly AT are discussed in relation to the above finding. The changes in Tm versus log M slopes with θG C are interpreted in terms of changes in the thermodynamic parameters ΔS and ΔH with base composition.
Conformational studies on a modified poly‐L‐tryptophan: Circular dichroism and optical rotatory dispersion of poly‐2‐(2‐nitrophenylsulfenyl)‐L‐tryptophan and of random copolymers of L‐tryptophan and 2‐(2‐nitrophenylsulfenyl)‐L‐tryptophan
Authors: Peggion Evaristo , Fontana Angelo , Cosani Alessandro 
Published: May 2005

AbstractOptical rotatory dispersion (ORD) and circular dichroism (CD) measurements were carried out on a block copolymer, (γ‐ethyl DL‐glutamate)160 (L‐Trp)32, in which the tryptophan sequence has been modified to various extents by using 2‐nitrophenylsulfenyl chloride. The CD spectrum of the completely modified copolymer exhibits bands in some of the regions of maximum absorption of the sidechain chromophores. In the peptide absorption region the spectrum is similar to that reported in the literature for polypeptides in the α‐helical conformation. When the extent of modification of the tryptophan sequence is progressively reduced, there is a gradual change in the ORD spectra of the copolymers. On the basis of these data the assumption was made that no conformational change occurs on proceeding from the pure unmodified tryptophan sequence to the completely modified sequence. The results are discussed in connection with the study of possible conformational effects arising from selective chemical modification of tryptophan residues in proteins.
Optical rotation of some α‐1,4‐linked glucopyranosides in the system H2O–DMSO and solution conformation of amylose
Authors: Dintzis F. R. , Tobin R. 
Published: May 2005

AbstractThe specific rotation of starch components, corrected for refractive index variation, exhibits a discontinuity in the region of the water–dimethyl sulfoxide (H2O–DMSO) system that corresponds to the composition of the complex 2H2O–DMSO. This discontinuity is a property dependent upon the presence of a number of consecutively linked α‐1,4 glucose units and, therefore, must reflect a change in symmetry of a segment, of polymer chain. The optical rotation of amylose between 26.5 and 92.5°C. does not change in DMSO and is only slightly lowered in water at the higher temperature. The behavior of amylose in both DMSO and H2O is like that of a random coil, as indicated by viscosity and sedimentation measurements. These results may be interpreted either as being compatible with models of amylose in solution in which the polymer backbone has helical twist, or as indicating removal of strong interactions between polymer chain segments by a good solvent.
Matching of single‐strand breaks to form double‐strand breaks in DNA
Authors: Freifelder David , Trumbo Bruce 
Published: May 2005

AbstractSingle‐strand breaks (ssb) in opposite strands of DNA can be sufficiently near that a double‐strand break (dsb) results. A theory is presented by which the maximum number h of base pairs which cannot prevent double‐strand breakage can be determined from the rates of production of ssb and dsb. The assumptions required to derive the necessary equations as well as the range of validity of the equations are discussed in detail. In the experiments ssb and dsb were produced by x‐irradiation in buffers which do not eliminate indirect effects and were measured by analytical ultracentrifugation. Values of h have been determined in low and high ionic strength and in low ionic strength over a range of temperatures. The values, 2.64 and 15.8, were obtained for high and low ionic strength, respectively.
Helix sense of poly‐γ‐p‐chlorobenzyl L‐glutamate
Authors: Erenrich Eric H. , Andreatta Rudolph H. , Scheraga Harold A. 
Published: May 2005

AbstractPoly(γ‐p‐chlorobenzyl L‐glulamate), for which theoretical calculations have shown only a small difference in energy between the left‐ and right‐handed α‐helices, has been synthesized and its screw sense determined by ORD in various solvents. In all solvents studied, a right‐handed α‐helix has been observed.
The Lifson‐Allegra theories of the helix–coil transition for random copolymers: Comparison with exact results and extension
Authors: Poland Douglas , Scheraga Harold A. 
Published: May 2005

AbstractThe theories of the helix–coil transition of Lifson, Lifson and Allegra, and Allegra for random copolymers are compared with the exact results of Lehman and McTague, as was done by Fink and Crothers in an earlier test of the approximate theories of Fixman and Zeroka, Reiss et al, and Montroll and Goel. The Fixman‐Zeroka theory is the best approximation to the exact result (under the conditions used), and the Allegra theory is next best, the calculated slope of the transition curve in the Allegra theory being too small by a factor of two. An alternative derivation of the Allegra approximation, using the method of sequence generating functions, is given, and the resulting equations are of very simple form. A hybrid method, based on the work of Lifson and Allegra, is also developed here; it involves a technique of successive approximations, and reduces to the Allegra theory in first order. The fourth‐order approximation gives a slope that is too small by 10%; however, the value of the slope, extrapolated to infinite order of approximation, converges to the exact result‐ of Lehman and Mc‐Tague. By using illustrative calculations of helix–coil transition curves, some physical insight into the behavior of a copolymer in the transition region is provided: it is found that an important feature determining the shape of the transition curve is the variation in composition over the correlation length. The question of the application of copolymer theory to DNA is discussed.
Optical anisotropy of synthetic polynucleotides. II. Calculation of π‐electron polarizability of uracil and adenine
Authors: Takashima Shiro 
Published: May 2005

AbstractThe π‐electron polarizability of conjugated base molecules such as uracil and adenine are calculated semiempirically by using molecular orbital theories. The Hüekel method and the self‐consistent‐field (SCF) theory are used in the present calculation. The theoretical values obtained by the Hüekel method are consistently larger than the experimental results. The values obtained by the SCF theory are in good agreement with observed values. It is clearly demonstrated that the SCF method is better than the Hükel method for the calculation of polarizability. The polarizability of the adenine–uracil pair is calculated as the sum of the polarizabilities of adenine and uracil and also calculated by solving the eigenvalue problem for the A–U pair as an entity. The second method gives considerably larger polarizability than the first method. Discussions are presented and it is demonstrated that the second method is the correct way to calculate the polarizability of the A–U pair.
Binding of alcohols to the peptide CO‐group of poly‐L‐proline in the I and II conformation. I. Demonstration of the binding by infrared spectroscopy and optical rotatory dispersion
Authors: Strassmair H. , Engel J. , Zundel G. 
Published: May 2005

AbstractThe binding of n‐butanol, benzyl alcohol, and trifluoroethanol to polyproline I (all peptide bonds in cis configuration) and II (all peptide bonds in trans configuration) has been demonstrated. It was found by infrared spectroscopy that hydrogen bonds are formed between the CO groups of the polymer and the OH groups of the alcohols. Their strength increases from n‐butanol via benzyl alcohol to trifluoroethanol. The binding of benzyl alcohol could also be followed by optical rotatory dispersion due to the fact that the electronic transitions of the benzyl ring are rendered optically active by the binding to the polymer.
Deformation behavior of erythrocyte ghost
Authors: Blais J. J. B. P. , Geil P. H. 
Published: May 2005

AbstractBiological membranes consist mainly of lipids and proteins. At present, the structure of the lipid phase appears to be established, but hypotheses on the molecular organization of the protein are difficult to support. Thus the deformation behavior of whole human erythrocyte ghosts, ghosts after the selective removal of lipids and ghosts stripped of lipids as well as nonlipid components have been examined in the hope of securing indirect information on the organization of the protein. It has been found that large localized deformations result in partial membrane failure and long uniformly wide fibrils, frequently in excess of 3000 Å, are drawn across the rupture. These data are interpreted in terms of currently favored membrane models and the possibility of a fibrous membrane framework consisting predominantly of protein is reviewed. The behavior of the membrane in its various stages of extraction is compared and contrasted to that of synthetic polymer films of known organization.
Effect of pressure on the temperature‐dependent association of β‐casein
Authors: Payens T. A. J. , Heremans K. 
Published: May 2005

AbstractThe effect of pressure on the temperature‐dependent association of β‐casein was studied by the method of light scattering. Between 1 and 1500 kg/cm2, β‐casein is reversibly depolymerized, indicating an increase in partial specific volume of the protein with association. Possible mechanisms for association are discussed. At still higher pressures reversible reassociation is observed, which is ascribed to conformational changes in the β‐casein molecule.
Optical anisotropy of oriented deoxyribonucleic acid films of different water content
Authors: Wetzel H. , Zirwer D. , Becker M. 
Published: May 2005

AbstractUltraviolet absorption and dichroism measurements on oriented films of calf thymus deoxyribonucleic acid (DNA) at varying degrees of hydration show a structural hysteresis which occurs within a relative humidity of 0 to 65% RH. This hysteresis is interpreted on the basis of a model which assumes the existence of structure‐stabilizing hydrogen water bridges in the DNA double helix.
Solution properties of synthetic polypeptides. V. Helix–coil transition in poly(β‐benzyl L‐aspartate)
Authors: Hayashi Yoshihisa , Teramoto Akio , Kawahara Kazuo , Fujita Hiroshi 
Published: May 2005

AbstractSimple approximate expressions have been derived from the theory of Zimm and Bragg for use in the analysis of experimental data on the helix‐coil transition in polypeptide. On the basis of the resulting expressions practical procedures are proposed to determine two basic parameters characterizing a thermally induced transition, i.e., helix initiation parameter σ and enthalpy change for helix formation, ΔH. They have been applied to the data for poly(β‐benzyl L‐aspartate) (PBLA) with the result: σ = 1.6 × 10−4 and ΔH = −450 cal/mole for PBLA in m‐cresol; σ = 0.6 × 10−4 and ΔH = 260 cal/mole for PBLA in chloroform containing 5.7 vol‐% of dichloroacetic acid. This result gives evidence that σ may change not only from one polypeptide to another but also for a given polypeptide in different solvents. The change in limiting viscosity number [η] accompanying the transition was measured in the same solvents. The curve of [η] versus helical content had a relatively monotonic shape for the chloroformdichloroacetic acid solutions as compared with that for the m‐cresol solutions, indicating that [η] depended largely on σ. Provided that [η] is a direct measure of the mean‐square radius of gyration, 〈S2〉, the results are consistent with the theoretical predictions of Nagai and of Miller and Flory for 〈S2〉.
Changement de structure de la poly‐L‐proline à l'état solide par hydratation: Etude par spectrométrie infra‐rouge
Authors: De Lozé C. , Josien M. L. 
Published: May 2005

AbstractFilms of poly‐L‐proline I and II have been hy drated by water vapor and their infrared spectra analysed between 1250 and 3500 cm−1. Forms I and II behave differently. Water binds to the carbonyl of form II through hydrogen bridges and, when released by drying, leaves the polypeptide conformation unchanged. In form I, complex formation with water seems to proceed through a different mechanism involving more than the carbonyls. Hydration of form I yields a partial irreversible transition to form II. Successive hydration and drying of the film brings the transition to completion. This I → II transition in the solid state has a cooperative character; its mechanism is discussed. Poly‐L‐prolines I and II also absorb vapors of aliphatic alcohols but not change in conformation is observed.
Stereochemistry of nucleic acids and polynucleotides. IV. Conformational energy of base‐sugar units
Authors: Lakshminarayanan A. V. , Sasisekharan V. 
Published: May 2005

AbstractIn this paper, the preferred conformations of the bases with respect to the sugar in various base‐sugar units are worked out using criteria of potential energy. The van der Waals type of intercations between nonbonded atoms is represented by a 6‐12 function and the electrostatic interactions have been calculated in the monopole approximation using Coulomb's law. The torsional contributions to the total energy have been neglected. It is found that in general the pyrimidines have preferred anti contributions (as described by Donohue and Trueblood) and purines have both syn and anti and conformations. Certain differences between differently puckered riboses in regard to the above general tendency are discussed. The conclusions, in general, conform with the results obtained by us earlier with the use of hard‐sphere potential and are also supported by observations on conformations of nucleotides and nucleotides in crystal structure.