bluuebunny/crossref_metadata_2025_split huggingface dataset:
Band Theory, Valence Bond, and Tight-Binding Calculations
Authors: Löwdin Per-Olov 
Published: April 2005

In the theory of the electronic structure of crystals, the fundamental features of the band theory, the valence bond method, and the tight-binding approximation are reviewed. The band theory is studied on the basis of the Hartree-Fock scheme, and the Bloch functions are formed by a projection technique. The main methods for calculating Hartree-Fock functions in a solid are briefly discussed. The advantages and disadvantages of the band theory and the valence bond method are emphasized, and special attention is paid to the correlation error.
In connection with the tight-binding approximation, the importance of the continuum part and of the approximate linear dependencies is stressed. It is shown that a complete orthonormal set of translationally connected atomic orbitals may be constructed as a convenient basis for this approach. The implication of the virial theorem in interpreting the cohesive properties of the ionic crystals is further emphasized.
Some recent refinements of band theory are then discussed. It is shown that a large part of the correlation error can be removed by permitting ``different orbitals for different spins.'' This leads to a scheme intermediate between band theory and valence bond method and, by means of a single parameter, one can obtain an essential lowering of the energy curve and the correct asymptotic behavior for separated atoms or constituents. This approach may be generalized to an extension of the Hartree-Fock scheme, where the total wave function is defined as a projection of a Slater determinant.
The band theory can be further refined and connected to the exact solution of the many-electron Schrödinger equation of the crystal by means of an extension of the self-consistent-field scheme, utilizing the so-called reaction operator here exactly defined by means of a simple partitioning technique. The various types of self-consistent field theories are finally compared.
Studies on the Substructure of Real Crystals by Optical and Magnetic Resonance Methods
Authors: Bansigir K. G. , Schneider E. E. 
Published: April 2005

Direct ultramicroscopic studies and measurements of the optical scattering spectrum of ``pure'' and doped alkali halide crystals are described showing the existence of elementary scattering centers and of assemblies of such centers. The elementary scatterers are established to be impurity precipitates of dimensions not exceeding a few hundred angstroms. The assemblies lead to characteristic ultra-microscopically visible diffraction images representing decorations of branch points of a semi-organized network of dislocations which reflect the state of strain and deformation in the subgrains of the mosaic structure of the single crystals. With increasing temperature the number of elementary scatterers decreases as impurities enter the host lattice into true solid solution, and the size of the assemblies diminishes.
Electron spin resonance experiments on doped alkali halides are discussed which provide direct information on the process of dissolution and reprecipitation of impurity ions. Results on strong exchange effects in the electron spin resonance of the systems MnCl2–NaCl and MnCl2–KCl are presented which are explained in terms of the substructure of very small impurity precipitates deduced from the optical investigations.
Reactions among Point Defects in Alkali Halides
Authors: Lidiard A. B. 
Published: April 2005

Existing knowledge of point defects and their interactions in uncolored alkali halide crystals is briefly reviewed. Attention is drawn to recent experimental and theoretical work which indicates that vacancy pairs are not highly mobile defects. This has important implications for some hypotheses on the kinetics of color center reactions at low temperatures.
This knowledge of defects in uncolored crystals is then applied to a discussion of the reactions which may take place between F centers and impurity ions in additively-colored doped crystals and the theoretical possibilities are compared with experimental information on Z centers. Consideration of the thermodynamic equilibria in these reactions seems to eliminate the Z1 and Z2 centers of Pick as possible causes of either of the Z1 and Z2 absorption bands in KCl. (The Z2 model of Pick is identical with the Z1 model of Seitz and is a divalent impurity cation which has trapped an electron.) Two possible centers for the Z2 band presen tthemselves; (a) an associate of an F center with a divalent cation and (b) an associate of an F center with an impurity-vacancy pair (the Z2 model of Seitz). The structure of the Z1 center is not resolved by these considerations. Attention is drawn to some paradoxical experimental results on Z1 and Z2 centers and further experiments to resolve outstanding questions are suggested.
Filamentary Impact Ionization in Compensated Germanium at 4.2°K
Authors: Melngailis I. , Milnes A. G. 
Published: April 2005

An experimental study is made of filamentary impact ionization breakdown observed in germanium doped with both group III and group V elements at liquid helium temperature.
The approximate size of the filament at various current values after ionization is estimated from the measurement of voltage-current characteristics of small cross section bars with high current pulses. Measurements are also made with cylindrical ``tecnetron'' structures in which the conduction channel can be reduced to very small areas by reverse bias of a ring-shaped p-n junction alloyed around a small cylindrical bar. Results of the two experiments are consistent. Near the lowest current value at which ionization can be sustained (about 40 μa), the approximate filament diameter is 10−3 cm.
Thermal and Electrical Transport in InAs-GaAs Alloys
Authors: Hockings E. F. , Kudman I. , Seidel T. E. , Schmelz C. M. , Steigmeier E. F. 
Published: April 2005

The thermal conductivity, Seebeck coefficient, and electrical resistivity have been measured as a function of temperature for various impurity concentrations and alloy compositions. Room-temperature measurements of Hall mobility and the optical determination of electron effective masses have been made.
n-type alloys between 50 and 70 mole % InAs, doped with selenium to give room-temperature resistivities of 4 to 8×10−4Ω·cm, give an optimum figure of merit. The maximum figure of merit at 700°K was measured to be 0.98×10−3 deg−1· p-type alloys (30%–70% InAs) doped with zinc gave a maximum figure of merit of only 0.4×10−3 deg−1 at 700°K. The room-temperature Hall mobilities and Seebeck coefficients of the p-type alloys are lower than might be anticipated. The electron effective masses were found to vary uniformly with composition.
An Examination of Collaborative Planning Effectiveness and Supply Chain Performance
Authors: Petersen Kenneth J. , Ragatz Gary L. , Monczka Robert M. 
Published: April 2005

SummaryMany organizations are attempting to gain a competitive advantage by integrating their suppliers more thoroughly into key supply chain processes. This calls for greater strategic and operational cooperation between buyer and supplier firms, often involving some degree of collaborative planning. Advances in information technology are making it possible for firms to share planning information more quickly and easily. This study surveyed purchasing executives whose firms are involved in collaborative planning with suppliers to examine several factors that support effective planning and the impact that effective collaborative planning has on performance in the buying firm. The results show that effective collaborative planning is dependent on the level of trust and the quality of information shared between firms.
Purchasing's Internal Service Performance: Critical External and Internal Determinants
Authors: Fredendall Lawrence D. , Hopkins Christopher D. , Bhonsle Amit 
Published: April 2005

SummaryThis article examines the importance of purchasing's level of internal and external cooperation on its internal service performance and how leadership influences both internal and external cooperation. Results found that visionary leadership increases purchasing's internal and external cooperation, which in turn improves purchasing's internal service performance. The data were obtained from a survey of 2,500 Institute for Supply Management™ members, and were analyzed using structural equation modeling. The implications for practicing managers and for future research are discussed.
Sourcing Indirect Spend: A Survey of Current Internal and External Strategies for Non‐Revenue‐Generating Goods and Services
Authors: Cox Andrew , Chicksand Daniel , Ireland Paul , Davies Tony 
Published: April 2005

SummaryThis article provides evidence about the current sourcing strategies for indirect spend from a survey of 124 organizations. The study found that, despite the recent prominence of reverse auctions and outsourcing options, the most frequently cited external sourcing management approach for indirect spend is long‐term collaboration with preferred suppliers. There was also evidence that indirect spend suffers from a lack of internal support, maverick purchasing, and fragmentation of spend within the organization.
An investigation of the effect of privatization of retail sales of alcohol on consumption and traffic accidents in Alberta, Canada
Authors: Trolldal Björn 
Published: April 2005

ABSTRACTAims  Privatization of the retail sale of alcohol in Alberta took place primarily between the end of the 1980s and the beginning of the 1990s. The aim of this study was to evaluate the effects of this privatization on alcohol sales and on the incidence of fatal motor vehicle traffic accidents in the province.Data and method  Interrupted time‐series analysis (ARIMA) with a quasi‐experimental control area design was used, and all series were differenced to remove long‐term trends. Canada, with the exception of Alberta, was the control area. The effects of privatization were measured by means of created privatization variables. In the analyses of the effects of privatization on alcohol sales, the inhabitants’ disposable income and alcohol prices were used as control variables. The study period was 1950–2000. When effects on the number of fatal motor vehicle traffic accidents were analysed the number of road motor vehicle registrations was used as a control variable, and the study period was 1950–98.Findings  Privatization had a significant permanent effect on the sale of spirits, but the effect was not large enough to affect total sales. The effect on wine and beer sales was not significant. There was no significant effect on the number of fatal motor vehicle traffic accidents.Conclusion  The fact that sales on the wholesale level continued to be monopolized, along with the fact that alcohol sales were never allowed in ordinary grocery stores, may explain the lack of any larger effects of privatization on alcohol sales in Alberta.
Age of onset of drinking and the use of alcohol in adulthood: a follow‐up study from age 8–42 for females and males
Authors: Pitkänen Tuuli , Lyyra Anna‐Liisa , Pulkkinen Lea 
Published: April 2005

ABSTRACTAim  To investigate longitudinally for both genders the relation between the age of onset of drinking and several indicators of alcohol use.Design and setting  In the Finnish Jyväskylä Longitudinal Study of Personality and Social Development, data have been collected by interviews, inventories, and questionnaires. Data on alcohol consumption was gathered at ages 14, 20, 27, 36 and 42 years; behavioural data at age 8.Participants  A total of 155 women and 176 men; 90.4% of the original sample consisting of 12 complete school classes in 1968.Measurements  The age of onset of drinking was determined based on participants’ responses that were closest to the actual age of onset of drinking. Four indicators of the adult use of alcohol were used: frequency of drinking, binge drinking, Cut‐down, Annoyed, Guilt, Eye‐opener (CAGE) and Malmö modified Michigan Alcoholism Screening Test (Mm‐MAST). Socio‐emotional behaviour at age 8 was assessed using teacher ratings and peer nominations.Findings  Early onset of drinking was related to the four indicators of the use of alcohol in adulthood both in men and women. The level of adult alcohol use and alcohol problems was significantly higher in men. The risk for heavy drinking was highest in men and women if drinking was started at less than age 16 years. Socio‐emotional behaviour and school success at age 8 did not predict the age of onset of drinking.Conclusions  Delaying the initiation of drinking from early adolescence to late adolescence is an important goal for prevention efforts. No clear risk group for early initiators of drinking could be identified on the basis of preceding behaviour among 8‐year‐olds.
Iatrogenic effects of psychosocial interventions for substance use disorders: prevalence, predictors, prevention
Authors: Moos Rudolf H. 
Published: April 2005

ABSTRACTAims  To examine the prevalence and personal and intervention‐related predictors of potential iatrogenic effects associated with psychosocial interventions for substance use disorders and provide a conceptual framework to guide further research on such effects.Method  A review of relevant studies focuses on the prevalence and predictors of potential iatrogenic effects of psychosocial treatment and prevention programs for substance use disorders.Results  Between 7% and 15% of patients who participate in psychosocial treatment for substance use disorders may be worse off subsequent to treatment than before. In addition, several controlled trials of substance use prevention have shown some apparent iatrogenic effects, including more positive expectations about substance use and a rise in alcohol use and alcohol‐related problems. Probable person‐related predictors of deterioration associated with treatment include younger age and unmarried status, more serious current diagnoses and substance use problems and more psychiatric and interpersonal problems. Probable intervention‐related predictors of deterioration include lack of bonding; lack of monitoring; confrontation, criticism and high emotional arousal; deviancy modeling; and stigma, low or inappropriate expectations and lack of challenge.Conclusion  A significant minority of individuals with substance use problems appear to deteriorate during or shortly after participation in treatment or prevention programs. Safety standards and monitoring procedures are needed to routinely identify potential adverse consequences of intervention programs; research is needed to clarify whether deterioration is due to iatrogenic effects of interventions and to identify new approaches to counteract any such effects.
Randomized controlled trial of a web‐based computer‐tailored smoking cessation program as a supplement to nicotine patch therapy
Authors: Strecher Victor J. , Shiffman Saul , West Robert 
Published: April 2005

ABSTRACTAim  To assess the efficacy of World Wide Web‐based tailored behavioral smoking cessation materials among nicotine patch users.Design  Two‐group randomized controlled trial.Setting  World Wide Web in England and Republic of Ireland.Participants  A total of 3971 subjects who purchased a particular brand of nicotine patch and logged‐on to use a free web‐based behavioral support program.Intervention  Web‐based tailored behavioral smoking cessation materials or web‐based non‐tailored materials.Measurements  Twenty‐eight‐day continuous abstinence rates were assessed by internet‐based survey at 6‐week follow‐up and 10‐week continuous rates at 12‐week follow‐up.Findings  Using three approaches to the analyses of 6‐ and 12‐week outcomes, participants in the tailored condition reported clinically and statistically significantly higher continuous abstinence rates than participants in the non‐tailored condition. In our primary analyses using as a denominator all subjects who logged‐on to the treatment site at least once, continuous abstinence rates at 6 weeks were 29.0% in the tailored condition versus 23.9% in the non‐tailored condition (OR = 1.30; P = 0.0006); at 12 weeks continuous abstinence rates were 22.8% versus 18.1%, respectively (OR = 1.34; P = 0.0006). Moreover, satisfaction with the program was significantly higher in the tailored than in the non‐tailored condition.Conclusions  The results of this study demonstrate a benefit of the web‐based tailored behavioral support materials used in conjunction with nicotine replacement therapy. A web‐based program that collects relevant information from users and tailors the intervention to their specific needs had significant advantages over a web‐based non‐tailored cessation program.
Gamma‐glutamyltransferase in fine‐needle liver biopsies of subjects with chronic hepatitis C
Authors: Paolicchi A. , Marchi S. , Petruccelli S. , Ciancia E. , Malvaldi G. , Pompella A. 
Published: April 2005

Summary.  Serum gamma‐glutamyltransferase (GGT) is considered as a sensitive but rather nonspecific marker of hepatobiliary disease, including chronic hepatitis C virus (HCV) infection. Although its increase in HCV infection is associated with poor response to interferon‐α (IFN‐α) and poor prognosis, there is little knowledge of the reasons of its increase during disease.Immunohistochemistry and enzyme histochemistry were performed on fine‐needle biopsies of subjects with HCV infection. GGT was detected in the lumen of bile ducts and in bile canaliculi. Furthermore, in subjects with elevated serum GGT, immunoreactive and catalytically active GGT was also detected on the sinusoidal surface of hepatocytes and diffuse cytoplasmic positivity appeared in isolated hepatocytes and hepatocellular foci. Antigen unmasking procedures showed the presence of GGT in the cytoplasm of mature and immature bile cells and of inflammatory cells. These results suggest that during chronic HCV infection there is a general enhancement of GGT activity within the liver. As the activity of several inflammatory mediators, such as leukotrienes, nitric oxide, and interleukins is modulated by GGT activity, the present findings suggest a direct relationship between serum GGT, enhanced intrahepatic GGT activity and prognosis and therapeutic outcome of chronic HCV infection.
Evidence of selection for low cognate amino acid bias in amino acid biosynthetic enzymes
Authors: Alves Rui , Savageau Michael A. 
Published: April 2005

SummaryIf the enzymes responsible for biosynthesis of a given amino acid are repressed and the cognate amino acid pool suddenly depleted, then derepression of these enzymes and replenishment of the pool would be problematic, if the enzymes were largely composed of the cognate amino acid. In the proverbial ‘Catch 22’, cells would lack the necessary enzymes to make the amino acid, and they would lack the necessary amino acid to make the needed enzymes. Based on this scenario, we hypothesize that evolution would lead to the selection of amino acid biosynthetic enzymes that have a relatively low content of their cognate amino acid. We call this the ‘cognate bias hypothesis’. Here we test several implications of this hypothesis directly using data from the proteome of Escherichia coli. Several lines of evidence show that low cognate bias is evident in 15 of the 20 amino acid biosynthetic pathways. Comparison with closely related Salmonella typhimurium shows similar results. Comparison with more distantly related Bacillus subtilis shows general similarities as well as significant differences in the detailed profiles of cognate bias. Thus, selection for low cognate bias plays a significant role in shaping the amino acid composition for a large class of cellular proteins.
The McbR repressor modulated by the effector substanceS‐adenosylhomocysteine controls directly the transcription of a regulon involved in sulphur metabolism ofCorynebacterium glutamicumATCC 13032
Authors: Rey Daniel A. , Nentwich Svenja S. , Koch Daniel J. , Rückert Christian , Pühler Alfred , Tauch Andreas , Kalinowski Jörn 
Published: April 2005

SummaryIn a recent proteomics study we have shown that themcbRgene ofCorynebacterium glutamicumATCC 13032 most probably encodes a transcriptional repressor of the TetR type, which regulates the expression of at least six genes involved in the synthesis of sulphur‐containing amino acids. By means of DNA microarray hybridizations we detected 86 genes with enhanced transcription in anmcbRmutant when compared with the wild‐type strain. Bioinformatic analysis identified the inverted repeat 5′‐TAGAC‐N6‐GTCTA‐3′ as a consensus sequence within the upstream region of 22 genes and operons, suggesting that the transcription of at least 45  genes is directly controlled by the McbR repressor. These 45 genes encode a variety of functions in  (S‐adenosyl)methionine  and  cysteine  biosynthesis, in sulphate reduction, in uptake and utilization of sulphur‐containing  compounds  and  in  transcriptional regulation. The function of the inverted repeat motif as potential McbR binding site in front of the geneshom,cysI,cysK,metKandmcbRwas verified experimentally by competitive electrophoretic mobility shift analysis. A systematic search for the potential effector substance modulating the function of McbR revealed that onlyS‐adenosylhomocysteine prevented the binding of McbR to its target sequence. These results indicate that the transcriptional repressor McbR directly regulates a set of genes comprising all aspects of transport and metabolism of the macroelement sulphur inC. glutamicum. As the activity of McbR is modulated byS‐adenosylhomocysteine, a major product of transmethylation reactions, the results point also to a novel regulatory mechanism in bacteria to control the biosynthesis ofS‐adenosylmethionine.
Bacillus subtilis antibiotics: structures, syntheses and specific functions
Authors: Stein Torsten 
Published: April 2005

SummaryThe endospore‐forming rhizobacterium Bacillus subtilis– the model system for Gram‐positive organisms, is able to produce more than two dozen antibiotics with an amazing variety of structures. The produced anti‐microbial active compounds include predominantly peptides that are either ribosomally synthesized and post‐translationally modified (lantibiotics and lantibiotic‐like peptides) or non‐ribosomally generated, as well as a couple of non‐peptidic compounds such as polyketides, an aminosugar, and a phospholipid. Here I summarize the structures of all known B. subtilis antibiotics, their biochemistry and genetic analysis of their biosyntheses. An updated summary of well‐studied antibiotic regulation pathways is given. Furthermore, current findings are resumed that show roles for distinct B. subtilis antibiotics beyond the ‘pure’ anti‐microbial action: Non‐ribosomally produced lipopeptides are involved in biofilm and swarming development, lantibiotics function as pheromones in quorum‐sensing, and a ‘killing factor’ effectuates programmed cell death in sister cells. A discussion of how these antibiotics may contribute to the survival of B. subtilis in its natural environment is given.