bluuebunny/crossref_metadata_2025 huggingface dataset:
The CUSCORE test and the q‐interval in cluster analyses of colon cancer and of lymphoma among asbestos workers
Authors: Chen R. , Froom P.
Published: September 2003

Exposure to a carcinogen is likely to be reflected by temporal clustering of cancer cases among the community members. Detection of such clustering is a complicated task in general and more so in a small workplace community with low turnover rate. In this study we applied the CUSCORE test and the q‐interval statistic to lymphoma and colon cancer death data among 2200 asbestos workers. The CUSCORE test was applied in order to identify clusters, and the q‐interval was used to provide clues related to the cause of the cluster. We also evaluated and tested the data according to the standardized mortality ratio (SMR). Significant increases in both colon cancer and lymphoma among asbestos workers in Israel (1987–1997) were demonstrated by the CUSCORE test but not so by the SMR. The fact that an apparent clustering was observed from the pattern of the q‐intervals leads to the conclusion that the detected clusters are real. Copyright 2003 John Wiley & Sons, Ltd.
Minimizing predictability while retaining balance through the use of less restrictive randomization procedures
Authors: Berger Vance W. , Ivanova Anastasia , Deloria Knoll Maria
Published: September 2003

The interpretation of between‐group comparisons is facilitated by the creation of treatment groups that are similar to each other in baseline composition. To prevent treatment effects from being confounded with time effects, most trials use restricted randomization to force balance. An unintended consequence of these restrictions is that they create patterns that allow for the prediction of future treatment allocations, and hence selection bias, especially in unmasked trials. In fact, the more restrictive the allocation procedure, the greater the potential for selection bias. It was decided, in the context of a recent clinical trial comparing two dosing schedules of paclitaxel and carboplatin for advanced stage IIIB/IV non‐small‐cell lung cancer, that the randomized block procedure could not simultaneously protect sufficiently against both selection and chronological bias. In this paper we detail our development of the maximal procedure. The maximal procedure takes as input the extent of chronological bias allowed by the randomized block procedure, then matches it, but does so with fewer restrictions. This feature makes the maximal procedure more resistant to selection bias than the randomized block procedure is. Published in 2003 by John Wiley & Sons, Ltd.
Consequences of exposure measurement error for confounder identification in environmental epidemiology
Authors: Budtz‐Jørgensen Esben , Keiding Niels , Grandjean Philippe , Weihe Pal , White Roberta F.
Published: September 2003

Non‐differential measurement error in the exposure variable is known to attenuate the dose–response relationship. The amount of attenuation introduced in a given situation is not only a function of the precision of the exposure measurement but also depends on the conditional variance of the true exposure given the other independent variables. In addition, confounder effects may also be affected by the exposure measurement error. These difficulties in statistical model development are illustrated by examples from a epidemiological study performed in the Faroe Islands to investigate the adverse health effects of prenatal mercury exposure. Copyright © 2003 John Wiley & Sons, Ltd.
A simulation‐based confidence band for drug concentrations in blood: an application to a clinical phase I trial
Authors: Yafune Akifumi , Ishiguro Makio
Published: September 2003

Since drug concentrations in blood are usually related to the effectiveness and toxicity, a confidence band for the drug concentrations gives useful information for the treatment. This paper proposes a simulation‐based approach for constructing confidence bands for drug concentrations in blood. The confidence band covers the whole profile of the drug concentrations with a specified probability. The proposed approach presupposes that actual concentrations of a subject fluctuate randomly around a curve specified by an appropriate pharmacokinetic model and the subject‐specific pharmacokinetic parameters. The confidence band is constructed by taking into account both the random fluctuations of the actual concentrations and the statistical uncertainty of the parameter estimates. The proposed approach is applied to a simulation study and an actual phase I trial. Copyright © 2003 John Wiley & Sons, Ltd.
Bayesian analysis of structural equation models with dichotomous variables
Authors: Lee Sik‐Yum , Song Xin‐Yuan
Published: September 2003

Structural equation modelling has been used extensively in the behavioural and social sciences for studying interrelationships among manifest and latent variables. Recently, its uses have been well recognized in medical research. This paper introduces a Bayesian approach to analysing general structural equation models with dichotomous variables. In the posterior analysis, the observed dichotomous data are augmented with the hypothetical missing values, which involve the latent variables in the model and the unobserved continuous measurements underlying the dichotomous data. An algorithm based on the Gibbs sampler is developed for drawing the parameters values and the hypothetical missing values from the joint posterior distributions. Useful statistics, such as the Bayesian estimates and their standard error estimates, and the highest posterior density intervals, can be obtained from the simulated observations. A posterior predictive p‐value is used to test the goodness‐of‐fit of the posited model. The methodology is applied to a study of hypertensive patient non‐adherence to medication. Copyright © 2003 John Wiley & Sons, Ltd.
Estimating regression models with unknown break‐points
Authors: Muggeo Vito M. R.
Published: September 2003

This paper deals with fitting piecewise terms in regression models where one or more break‐points are true parameters of the model. For estimation, a simple linearization technique is called for, taking advantage of the linear formulation of the problem. As a result, the method is suitable for any regression model with linear predictor and so current software can be used; threshold modelling as function of explanatory variables is also allowed. Differences between the other procedures available are shown and relative merits discussed. Simulations and two examples are presented to illustrate the method. Copyright © 2003 John Wiley & Sons, Ltd.
A chain of evidence with mixed comparisons: models for multi‐parameter synthesis and consistency of evidence
Authors: Ades A. E.
Published: September 2003

Multi‐parameter evidence synthesis is a generalization of meta‐analysis in which several parameters are estimated jointly. Here this approach is applied to a common form of data structure in which mixed pairwise comparisons are made between treatments in a ‘chain of evidence’ structure. The data set investigated here, which first appeared in the confidence profile method literature, features three types of data relating to thrombolytic treatment following acute myocardial infarction. There is information on reperfusion (coronary patency) following treatment, information on survival in reperfused and non‐reperfused patients (conditional survival), and independent information on the effect of treatment on survival without specifying reperfusion state (overall survival). The objective of this study is to explore models for combining these three types of evidence within a single model, and some of the evidence consistency issues that arise. Bayesian Markov chain Monte Carlo methods are used to fit two models. The first, proposed in the confidence profile literature, assumes there are no differences between studies in baseline effects (equal study effects). The second model assumes fixed treatment effects but allows for study differences in baseline reperfusion and conditional survival rates by assuming random study effects. The equal study effects model fits the data poorly, and cross‐validation shows that the overall survival evidence is not consistent with the reperfusion and conditional survival evidence under this model. The evidence appears to be consistent within the more loosely structured random study effects model, but results are sensitive to prior assumptions about the between‐study variance. The inconsistency between the three evidence types relates to overall survival, rather than to the effect of treatment on survival. Multi‐parameter evidence synthesis, with suitable checks for evidence consistency, can be used to help determine whether chains of evidence ‘add up’ epidemiologically within an overall model, and to construct parameter distributions for an entire model simultaneously, consistent with all the available data. Copyright © 2003 John Wiley & Sons, Ltd.
On the non‐inferiority of a diagnostic test based on paired observations
Authors: Lu Ying , Jin Hua , Genant Harry K.
Published: September 2003

Non‐inferiority of a diagnostic test to the standard or the optimum test is a common issue in medical research. Often we want to determine if a new diagnostic test is as good as the standard reference test. Sometimes we are interested in an inexpensive test that may have an acceptably inferior sensitivity or specificity. While hypothesis testing procedures and sample size formulae for the equivalence of sensitivity or specificity alone have been proposed, very few studies have discussed simultaneous comparisons of both parameters. In this paper, we present three different testing procedures and sample size formulae for simultaneous comparison of sensitivity and specificity based on paired observations and with known disease status. These statistical procedures are then used to compare two classification rules that identify women for future osteoporotic fracture. Simulation experiments demonstrate that the new tests and sample size formulae give the appropriate type I and II error rates. Differences between our approach and the approach of Lui and Cumberland are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Heterogeneity and transferring practices: implementing flow manufacturing in multiple plants
Authors: Maritan Catherine A. , Brush Thomas H.
Published: September 2003

Adopting new practices to develop capabilities and enhance competitiveness is a goal for many firms. This study of a corporate initiative to implement flow manufacturing in multiple plants highlights some elements of the interaction between the content of a complex practice, the sources of the practice knowledge, and the characteristics and competitive priorities of the recipients of the practice. Heterogeneity among the plants, stemming from both differences in resource endowments and differences in choices made by managers, presents challenges to achieving firm‐wide distinctiveness. Copyright © 2003 John Wiley & Sons, Ltd.
Doing the right thing and knowing the right thing to do: why the whole is greater than the sum of the parts
Authors: Makadok Richard
Published: September 2003

This paper models the joint impact of two determinants of profitable resource advantages: the accuracy of managers' expectations about the future value of a resource, and the severity of agency problems that cause managers' interests to diverge from those of shareholders. While the impact of each of these factors on resource‐investment decisions has been considered in isolation, their joint interaction effect has never been examined. The model generates the following set of testable hypotheses: Managers of firms with agency problems will, on average, tend to under‐invest (relative to what shareholders would ideally like them to do) in resources of uncertain value. This under‐investment will be most severe for those resources where managers' information indicates a low expected value (i.e., risky bets), and will actually be reversed (i.e., over‐investment) for those resources where managers' information indicates a high expected value (i.e., safe bets). Two levers can be used to reduce the degree of this under‐investment: reducing the severity of the agency problems, or improving the accuracy of managers' expectations. Based on their interaction effect, these two levers are shown to be complementary in the sense that they work better together at reducing under‐investment than either one does in isolation. Therefore, future research on the genesis of competitive advantage should examine agency and governance issues along with, not apart from, resource‐based issues. Copyright © 2003 John Wiley & Sons, Ltd.
The organizational routines factor market paradox
Authors: Knott Anne Marie
Published: September 2003

The resource‐based view (RBV) of strategy holds that superior organizational routines can be a source of value if and only if there is an isolating mechanism preventing their diffusion throughout industry. Generally this isolating mechanism is taken to be the tacitness of the routines. However, the existence of franchises, a market for organizational routines, poses a challenge to this RBV—if the routine is to be conveyed across a market, it can't be tacit. This paper examines the necessary and sufficient conditions of the RBV to find the weak link leading to the paradox of explicit, yet valuable franchise routines. Copyright © 2003 John Wiley & Sons, Ltd.
An asymmetry‐based view of advantage: towards an attainable sustainability
Authors: Miller Danny
Published: September 2003

The resource‐based view of the firm postulates that sustainable abnormal rents can accrue to firms having valuable, rare, inimitable, non‐substitutable resources and capabilities. Given these criteria, sustainable resources are hard to attain. Our study of some two dozen firms shows how some of them were able to overcome this dilemma by building not so much on resources and capabilities as on asymmetries. Asymmetries are typically skills, processes, or ‘assets’ a firm's competitors do not and cannot copy at a cost that affords economic rents. They are rare, inimitable and non‐substitutable, although not connected to any engine of value creation, and, in fact, often act as liabilities. By discovering and reconceptualizing these asymmetries, embedding them within a complementary organizational design, and leveraging them across appropriate market opportunities, many firms were able to turn asymmetries into sustainable capabilities. Copyright © 2003 John Wiley & Sons, Ltd.
Corporate effects and dynamic managerial capabilities
Authors: Adner Ron , Helfat Constance E.
Published: September 2003

Corporate effects in variance decomposition capture heterogeneity of business performance derived from factors internal to firms at the corporate level. Most estimates of corporate effects do not include effects associated with fluctuations in returns over time, except insofar as the fluctuations affect the average corporate return for the time period in question. Exclusion of the time‐varying dimension of the corporate effect makes it difficult to fully understand the effect of corporate strategy and the actions of corporate managers, particularly in response to a changing environment. The evidence in this article shows that within a single industry, where managers face the same external environment, time‐varying corporate effects associated with corporate level managerial decisions are statistically significant. We introduce the concept of dynamic managerial capabilities to underpin the finding of heterogeneity in managerial decisions and firm performance in the face of changing external conditions. Copyright © 2003 John Wiley & Sons, Ltd.
The payments perspective: micro‐foundations of resource analysis
Authors: Lippman Steven A. , Rumelt Richard P.
Published: September 2003

Problems in the micro‐foundations of neoclassical theory, especially in partial equilibrium analysis, are being imported into the resource‐based view. This paper critiques neoclassical theory and proffers new concepts more suited to strategy scholars. In particular, we develop the concepts of simple rents, rent sensitivity analysis, and the payments perspective. Copyright © 2003 John Wiley & Sons, Ltd.
Financial Issues in Campus Recreation
Authors: Taylor Howard , Canning William F. , Brailsford Paul , Rokosz Frank
Published: September 2003

Campus recreation centers, originally quasi‐academic facilites, have evolved since the early 1980s: first into campus amenities and then into auxiliary business enterprises. Financial issues affecting campus recreation have changed accordingly and are discussed in this chapter.
Selected Accountability and Assessment Issues
Authors: Schuh John H.
Published: September 2003

This chapter provides an overview of strategies that can be used to demonstrate accountability in financial issues in student affairs.
The Financial Environment of Student Affairs
Authors: Schuh John H.
Published: September 2003

This chapter examines factors that influence higher education finance, trends in revenue and expenditures of institutions of higher education, and current strategies used to meet financial challenges.
Comparing Financial Issues in Public and Private Institutions
Authors: Claar Joan M. , Scott Hazel J.
Published: September 2003

The authors compare and contrast financial issues in public and private colleges and universities. A case study illustrates the financial environments in which these types of institutions operate.
Financing Health and Counseling Services
Authors: Keeling Richard P. , Heitzmann Dennis
Published: September 2003

This chapter discusses the fundamentals of financing health and counseling centers and also identifies contemporary issues related to financing these two services.
Contemporary Issues in Student Housing Finance
Authors: Ryan Mary Ann
Published: September 2003

This chapter presents contemporary financial issues in student housing programs framed through the topical areas of occupancy management, facilities, new construction, residential life programs, technology, and residential dining.
Evaluation of the Degree of Starch Gelatinization by a New Enzymatic Method
Authors: Di Paola Romina D. , Asis Ramon , Aldao Mario A. J.
Published: September 2003

In this work, a new enzymatic method is proposed to evaluate the degree of starch gelatinization in starchy food and feed. The procedure developed is based on the fact that the gelatinization process enhances the chemical reactivity of inert starch granules towards amylolytic enzymes. Aqueous suspensions of maize starch were treated at different temperatures to obtain different degrees of gelatinization, from 25 °C (control without gelatinization) until 95 °C. Heated samples were then incubated with a glucoamylase. The enzymatic activity was measured by the glucose released during the digestion time by using a standard glucose oxidase method. The initial velocity value of the enzymatic reaction (Vi) was selected as the parameter to quantify the degree of starch gelatinization (DG). Changes in granule morphology and the starch available for hydrolysis were evaluated by photomicrographs. The new method was standardized and compared with DSC and viscosity measurements in order to check its efficiency, considering the DG observed by photomicrographs. A good agreement was observed between the DG calculated by Vi and by DSC (correlation coefficient r = 0, 97), thus Vi reflect the degree of starch gelatinization as well as DSC. These results show that the developed enzymatic procedure is an effective method to evaluate the DG in starchy foods and feeds.
Starch Paste Stickiness is a Relevant Native Starch Selection Criterion for Wet‐end Paper Manufacturing
Authors: Blennow Andreas , Bay‐Smidt Anne Mette , Leonhardt Peter , Bandsholm Ole , Madsen Marianne H.
Published: September 2003

The correct choice of selection and quality criteria is critical for most starch applications. In this study, a set of different potato starches, selected for a large variation in natural phosphate content and final viscosity, was cationised and tested in a laboratory scale wet‐end paper manufacturing process. Analysis of further parameters expected to be critical for processing, including amylose content and starch granule size, was also performed. Since no significant correlation was found between any of these parameters and paper processing, further attempts were made to find structural or physico‐chemical explanations for the paper processing performance. Hence, several additional parameters of the starches were determined including amylopectin chain length pattern, phosphate substitution, molecular size distribution, pasting‐texture properties and fragility of the gelatinised granules. Among these parameters, the best correlation found to paper filler retention was stickiness of the starch as measured by texture analysis. The starches that performed best in the paper trials showed rapid granule bursts that could be readily estimated from the width of the pasting curve peaks. Light microscopy of non‐soluble remnant starch obtained after gelatinisation of starch under dilute conditions revealed a high proportion of broken granular structures. It is hypothesised that the degree of phosphorylation, together with a hitherto unknown molecular parameter that is related to starch granule fragility, determines starch paste stickiness, which in turn is an important parameter for wet‐end paper manufacturing.
Mechanical Properties of White Salted Noodles from Near‐isogenic Wheat Lines with Different wx Protein‐Deficiency
Authors: Ishida Nanako , Miura Hideho , Noda Takahiro , Yamauchi Hiroaki
Published: September 2003

Flour with a low amylose content produces a desirable texture in white salted noodles (WSN). In order to understand the impact of amylose content on noodle texture, flours of similar quality but different starch characteristics must be compared and analyzed because the characteristics of the protein contained in the flour also affect the mechanical properties of WSN. In this study, eight genotypes of near‐isogenic wheat with different compositions of the Wx‐proteins involved in amylose synthesis were used to study the relationship between the mechanical properties of WSN and their amylose content in starch. Results of the study indicated that the breaking force/breaking deformation value of WSN made from the eight lines decreased and that softer noodles were obtained when the amylose content was lower. The gels made from flours and starches of the eight lines decreased in maximum compression stress, in line with the lowering of amylose content. These results show that the mechanical properties of WSN are determined primarily by the amylose content of the flour and the properties of the starch gel. Sensory evaluations of the WSN indicated that the noodles from the flours of single‐null types, which lack either the Wx‐B1 or Wx‐D1 proteins, and doublenull types, which lack the Wx‐A1 and Wx‐D1 proteins, especially the latter, had desirable textures.
Effect of Amylose Content on Gelatinization, Retrogradation and Pasting Properties of Flours from Different Cultivars of Thai Rice
Authors: Varavinit Saiyavit , Shobsngob Sujin , Varanyanond Warunee , Chinachoti Pavinee , Naivikul Onanong
Published: September 2003

Presently, rice cultivars are categorized according to amylose content into three groups: low, medium and high amylose content cultivars. The correlation of amylose content with gelatinization properties, retrogradation, and pasting properties of eleven cultivars of Thai rice were investigated. Rice flour was prepared from milled rice by the wet grinding process. Onset (To), peak (Tp) and conclusion (Tc) temperatures of gelatinization, (determined by DSC) were found to be highly positively correlated with amylose levels. This correlation could be used for prediction of amylose content of rice flour. Low amylose starch could also be characterized by low degree of retrogradation (%R). The data obtained from RVA‐viscograms (peak viscosity, breakdown, setback, and pasting temperature) can be used only for characterization of the group of low amylose starches (waxy rice). It was demonstrated that low amylose rice starch provided the highest peak viscosity and breakdown and the lowest setback and pasting temperature among the groups investigated.
Starch Properties in Different Lines of an old Hungarian Wheat Variety, Bánkúti 1201
Authors: Rakszegi Mariann , Batey Ian L. , Vida Gyula , Juhász Angéla , Bedő Zoltán , Morell Matthew K.
Published: September 2003

The old Hungarian wheat variety, Bánkúti 1201 was previously divided into lines on the basis of high molecular weight (HMW) glutenin subunit composition. In this work the starch properties of these lines were studied. The amylose contents of the lines ranged from 14.4% to 24.2%, which means a wide variation. The Rapid Visco Analyser (RVA) peak viscosity of the starch ranged from 232 to 372 Rapid Visco Units (RVU) and the enthalpy of gelatinisation (ΔH) measured by Differential Scanning Calorimetry (DSC) varied between 8.3 and 16.3 J/g. To study the relationship between the different lines on the basis of starch properties, Hierarchical Cluster Analysis was carried out based on RVA, DSC and HPLC results. Five groups of Bánkúti lines could be distinguished on the basis of these traits. According to the results, Bánkúti lines heterogeneous with respect to their HMW glutenin composition are also heterogeneous for their starch properties. Nevertheless, there was no correlation between the variability in protein composition and starch properties.
Reactivity in the System Copper/Arsenic/Sulfur II. The Formation of CuAsS, (Lautite)
Authors: Müller A. , Blachnik R.
Published: September 2003

The reaction pathways during the synthesis of CuAsS have been studied with the DTA in the range 25 — 810 °C with a heating rate of 10 K/min. Educts, intermediates, and products were characterized by X‐ray diffraction at room and elevated temperatures. Educts were the corresponding elements and the binary compounds As4S4, As2S3, Cu3—xAs, Cu5—δAs2, Cu2S, and CuS. The 13 examined educt mixtures can be divided into four groups specified by their thermal effects observed during the reaction. Mixtures of group I contain copper arsenides and arsenic sulfides, those of group II and III arsenic and copper sulfides, and arsenic sulfides and copper, respectively. Group IV includes mixtures showing individual reactions. In all cases the reaction to CuAsS proceeds stepwise. The reaction is not completed at 574 °C, the decomposition temperature of CuAsS, because the product is still associated with Cu12+xAs4+yS13 , As, and to a lesser amount with Cu1.81S. Nevertheless, a consecutive run in which the samples were heated above the liquidus temperature shows no exothermic reaction effect. When the mixtures were cooled at 10 K/min after the runs, no CuAsS was found in the X‐ray experiments. Only Cu12+xAs4+yS13 and As were then observed.
Investigations on Chemical Vapour Transport of Intermetallic Phases in the System Co/Fe/Si
Authors: Boldt R. , Reichelt W. , Bosholm O. , Oppermann H.
Published: September 2003

The ternary phases existing on the quasi binary section CoSi/FeSi and CoSi2/β‐FeSi2 have been investigated by solid state reactions and chemical transport. The solid solution serie CoxFe1‐xSi can be described as a regular solution. The transport behaviour calculated is in good agreement with the experiments. The phases have been characterized by X‐ray powder diffraction, EDX and ICP‐OES. The temperature dependence of the resistivity has been measured from 20 K up to room temperature on single crystals.
Kinetically Controlled Solid State Reactions in the System InCl/SnCl2
Authors: Beck H. P. , Kallmayer V.
Published: September 2003

This paper reports on studies on the reaction of InCl with SnCl2 to form ternary halides. The reaction route is investigated by x‐ray investigations at different temperatures. Depending on the modification of InCl as educt and on the temperature conditions the reaction follows different pathways which may include intermediate redox reactions of the type In+ + Sn2+ → In3+ + Sn0.
Nitridation of V5Al8 films with NH3 by Rapid Thermal Processing (RTP)
Authors: Lewalter H. , Kolbesen B. O.
Published: September 2003

V5Al8 films (thickness about 100 nm) were deposited on sapphire substrates by RF‐sputtering and nitridated with NH3 at 600‐1250 °C (1 min) in a RTP system. The as deposited and nitridated films were investigated by ESCA (electron spectroscopy for chemical analysis), XRD (X‐ray diffraction), XRR (X‐ray reflectometry), AFM (atomic force microscopy) and SEM (scanning electron microscopy). Formation of an aluminum nitride layer at the surface and precipitation of V(Al) in the bulk was found. In the temperature regime from 600 °C to 900 °C a considerable amount of oxygen is incorporated in the aluminum nitride layer. The roughness of the surface increased with increasing temperature and at 1250 °C a partially detaching of the AlN layer could be observed.
Preparation, Crystallographic, Spectroscopic and Magnetic Characterization of Low‐Valency Nitridometalates Li2[(Li1‐xMx)N] with M = Cu, Ni
Authors: Niewa R. , Huang Z.‐L. , Schnelle W. , Hu Z. , Kniep R.
Published: September 2003

Thermogravimetric and difference thermal analyses show that the reactions of lithium nitride with the transition metals Cu and Ni under molecular nitrogen to form phases Li2[(Li1‐xMIx)N] take place above 673 K. The maximum weight gains are reached at 926 K and 968 K for M = Cu and Ni, respectively. At higher temperatures, the ternary phases Li2[(Li1‐xMIx)N] decompose, limiting the substitutional level x. In the temperature range of 773 K — 873 K, the successful synthesis of Li2[(Li1‐xNiIx)N] (0 < x ≤ 0.85(1)) single phase products is demonstrated. Maximum substitution obtained for the Cu phases is xmax= 0.43(1). The dependence of the lattice parameters of the hexagonal unit cell on x is almost linear. The magnetic moment of M strongly depends on x. At low x the magnetic moments in phases with M = Ni are presumably enhanced by orbital effects. A decrease of μeff with x to μeff(x = 1) → 0 is explained by delocalization of the magnetic moments and by the gradual formation of a metal for the hypothetical compound Li2[NiN] (x = 1). XAS spectroscopy at the transition metal K‐edges shows that Cu and Ni principally correspond to d10‐ and d9‐configurations, respectively.
Nucleation of CuGa Phases on the MgO(100) Surface
Authors: Geudtner Gerald , Jug Karl
Published: September 2003

MSINDO calculations are presented for the coadsorption of Cu and Ga atoms as clusters and islands on the MgO(100) surface. The surface is simulated by a (8 × 8 × 3) Mg96O96 cyclic cluster. The relative number of Cu and Ga atoms was varied in order to understand the influence of copper rich and gallium rich phases. It was found that the copper atoms have a dominating influence on the structural arrangement in mixed phases. The adsorption sites of Cu and Ga atoms are preferably O atoms, but in mixed phases these sites are usually occupied by Cu atoms.
Theoretical Investigation of the Solid State Reaction of Silicon Nitride and Silicon Dioxide forming Silicon Oxynitride (Si2N2O) under Pressure
Authors: Kroll Peter , Milko Matus
Published: September 2003

The high‐pressure behavior of Si2N2O is studied for pressures up to 100 GPa using density functional theory calculations. The investigation of a manifold of hypothetical polymorphs leads us to propose two dense phases of Si2N2O, succeeding the orthorhombic ambient‐pressure polymorph at higher pressures:a defect spinel structure at moderate pressures and a corundum‐type structure at very high pressures. Taking into account the formation of silicon oxynitride from silicon dioxide and silicon nitride and its pressure dependence, we propose five pressure regions of interest for Si2N2O within the pseudo‐binary phase diagram SiO2‐Si3N4: (i) stability of the orthorhombic ternary phase of Si2N2O up to 6 GPa, (ii) a phase assemblage of coesite, stishovite, and β‐Si3N4 between 6 and 11 GPa, (iii) a possible defect spinel modification of Si2N2O between 11 and 16 GPa, (iv) a phase assemblage of stishovite and γ‐Si3N4 above 40 GPa, and (v) a possible ternary Si2N2O phase with corundum‐type structure beyond 80 GPa. The existence of both ternary high‐pressure phases of Si2N2O, however, depends on the delicate influence of configurational entropy to the free energy of the solid state reaction.
Chemical Reactivity of Tetrasulfur Tetranitride: Synthesis, Physical Properties, and Structural Characterization of the Amorphous Phase Cu7S4N4
Authors: Irsen Stephan H. , Kroll Peter , Dronskowski Richard , Weirich Thomas E. , Epple Matthias
Published: September 2003

Tetrasulfur tetranitride, S4N4, reacts with elemental Cu within inert solvents to a black‐blue material of approximate composition Cu7S4N4 which is totally amorphous to X‐rays and which cannot be made crystalline by either thermal treatment or electron radiation. Cu7S4N4 explodes if heated above 234 °C or when subjected to mechanical shock to eventually yield copper(I) sulfide; this together with the characteristic infrared spectrum of Cu7S4N4 indicates the presence of molecular S4N4 units inside the amorphous phase. The metastable nature of Cu7S4N4 is also mirrored by electron microscopy which furthermore allows the structural characterization of its degradation products. Based on experimental EXAFS data offering characteristic Cu—N and Cu—S distances, a theoretical crystalline approximant of Cu7S4N4 was suggested and structurally optimized by density‐functional total‐energy calculations including periodic boundary conditions. This model incorporates a central S4N4 unit bonded to three shells of Cu atoms of different functionalities; in addition, a partial rupture of the S4N4 unit is likely to allow for a lowering of the total energy of the metastable phase. The latter observation supports the impossibility to make Cu7S4N4 crystallize using 4N4 crystallize using whatever kind of measures.
Alkaline Metal Stannide‐Stannates: ‘Double Salts’ with Zintl Sn and Stannate SnO Anions
Authors: Frisch Gero , Hoch Constantin , Röhr Caroline , Zönnchen Peter , Becker Klaus‐Dieter , Niemeier Dirk
Published: September 2003

Using the reduction of tin oxides with the elemental alkaline metals rubidium and cesium, stannide stannates have been synthesized which contain Zintl anions [Sn4]4— (i.e. Sn—I) and isolated oxostannate ions [SnO3]4— (i.e. Sn+II) together with further oxide ions for charge compensation. The crystal structures of the three compounds A23.6Sn7.4O13.2 = A23.6[Sn4][SnO3]3.4[O]3 (A = Rb 1a: monoclinic, P21/c, a = 2174.2(6), b = 1137.0(6), c = 2373.6(6) pm, β = 116.11(2)°, Z = 4, R1 = 0.056; A = Cs 1b: monoclinic, P21/c, a = 2042.6(6), b = 1185.4(3), c = 2481.1(7) pm, β = 97.06(2)°, Z = 4, R1 = 0.075) and Cs48Sn20O21 = Cs48[Sn4]4[SnO3]4[O]7[O2] (2 monoclinic, P2/c, a = 1701.8(3), b = 877.4(2), c = 4556.9(7) pm, β= 101.47(1)°, R1 = 0.093) have been determined on the basis of single crystal data. The transparency of the compounds allowed the recording of raman spectra of the anion [Sn4]4—. The 119Sn Moessbauer spectrum of the rubidium compound shows a singulet in good agreement with RbSn, overlapping a doublet caused by Sn2+ in the asymmetrical environment of the strongly electronegative oxygen ligands of SnO.
Shape Controlling Synthesis — Formation of Fe3Si by the Reaction of Iron with Silicon Tetrachloride and Crystal Structure Refinement
Authors: Schütte M. , Wartchow R. , Binnewies M.
Published: September 2003

Pure Fe3Si is formed by the reaction of an iron‐wire with SiCl4‐vapor at a reaction temperature of 1000 °C and a SiCl4‐pressure of 2 bar. Remarkable is the fact that the outer shape of the used iron wire has not been changed during the reaction. The crystal structure of Fe3Si was determined using single crystal methods. Fe3Si crystallizes in the space group Fm3m. The lattice parameters depend on the composition.
Reactivity, Syntheses, and Crystal Structures of Na5[MO2][X] with M = Co+, Ni+, Cu+; X = CO32—, SO42—, SO32—, S2—, and Na25[CuO2]5[SO4]4[S]
Authors: Amann Peter , Möller Angela
Published: September 2003

Na5[CuO2][CO3], Na5[CuO2][SO3], Na5[CuO2][S], and Na5[CuO2][SO4] were obtained as single crystals and powders from reactions of Na2O, Cu2O, and Na2X with X = CO32—, SO32—, S2—, and SO42—, respectively. A redox reaction between CdO and Co metal occurs in the presence of Na2O and Na2X, yielding Na5[CoO2][X] with X = CO32— and S2—. From a mixture of Na2SO4, CdO and Na2O in Ni‐containers we observed the formation of Na5[NiO2][S] single crystals. Single crystals of Na25[CuO2]5[SO4]4[S] can be grown by annealing Na5[CuO2][SO3] at 600 °C, leading to the decomposition of SO32—, yielding SO42— and S2— at 550 °C. The structures have been determined from single crystal data and powder data. All structures contain the isolated complex [MO2]3— in a dumb‐bell like arrangement. The main feature of these compounds is that the anions SO42—, SO32—, CO32— and S2— are not connected to the transition metal. The formation of Na5[CuO2][X] (X = S2—, SO42—, SO32—, CO32—) has been studied by thermal analysis and in situ X‐ray diffraction techniques. Infrared spectra confirm the presence of SO42—, SO32—, and CO32—, respectively, in the structures.
The Reactivity of Cr‐Te Superlattice Reactants and of Co‐deposited Cr‐Te Films: Studies with in‐situ X‐ray Diffractometry
Authors: Herzog Sabine , Kraschinski Sven , Bensch Wolfgang
Published: September 2003

The reactivity of a Cr‐Te multilayer film consisting of 326 Cr/Te double‐layers with about 88(3) at% Te was investigated with in‐situ X‐ray diffraction. The occurrence of a superstructure reflection caused by the multilayer system is observed. During the annealing procedure between 80 and 90 °C the layer‐by‐layer arrangement is destroyed and elemental Te crystallizes. After 6 h isothermal annealing at 140 °C CrTe3 starts to crystallize. The amount and the crystal size of CrTe3 increase with raising temperature and Te is consumed during the growth process. At 220 °C the formation of crystalline Cr2Te3 is observed and between 220 and 260 °C CrTe3 is completely decomposed into Cr2Te3. The two Cr tellurides grow as highly textured materials. The size of CrTe3 crystals is significantly larger than that of Cr2Te3. For a co‐deposited Cr‐Te film with composition 77(3) at% Te the tri‐telluride and elemental Te crystallize simultaneously. The texture of CrTe3 is less pronounced and different reflections of the tri‐telluride occur besides the (h00)‐reflections. Up to 160 °C a pronounced increase of the crystallite size is observed and the crystals are significantly larger than those obtained with the multifilm sample. At 130 °C the crystallization kinetics seem to be controlled by nucleation.
Vanadium Nitride Films Formed by Rapid Thermal Processing (RTP): Depth Profiles and Interface Reactions Studied by Complementary Analytical Techniques
Authors: Berendes A. , Galesic I. , Mertens R. , Bock W. , Oechsner H. , Warbichler P. , Hofer F. , Theodossiu E. , Baumann H. , Kolbesen B. O.
Published: September 2003

The nitridation of vanadium films in molecular nitrogen and ammonia using a RTP‐system was investigated. The V films were deposited on silicon substrates covered by 100 nm thermal SiO2. For a few experiments sapphire substrates were used. Nitride formation at high temperatures (900 and 1100 °C) and interface reactions and diffusion of oxygen out of the SiO2‐layer into the metal lattice at moderate temperatures (600 and 700 °C) were studied. For characterisation complementary analytical methods were used: X‐ray diffraction (XRD) for phase analysis, secondary neutral mass spectrometry (SNMS) and Rutherford Backscattering (RBS) for acquisition of depth profiles of V, N, O, C and Si, transmission electron microscopy (TEM) in combination with electron energy filtering for imaging element distributions (EFTEM) and recording electron energy loss spectra (EELS) to obtain detailed information about the initial stages of nitride, oxide and oxynitride formation, respectively, and the microstructure and element distributions of the films. In these experiments the SiO2‐layer acts as diffusion barrier for nitrogen and source for oxygen causing the formation of substoichiometric vanadium oxides and oxynitrides near the V/SiO2‐interface primarily at temperatures ≤ 900 °C. At a temperature of 1100 °C just a small amount of oxynitride forms near the interface because rapid diffusion of nitrogen and fast formation of VN (diffusion barrier for oxygen) inhibit the outdiffusion of oxygen into the metal layer. In the 600 °C regime, in argon atmosphere oxynitride phases observed in the surface region of these films originate from reaction of residual oxygen in the argon gas, whereas NH3 as process gas does not lead to oxide or oxynitride formation at the surface (apart from the oxidation caused by storage). NH3 seems to support the diffusion of oxygen out of the SiO2‐layer. During the decomposition of ammonia at higher temperatures hydrogen is formed, which could attack the SiO2. In contrast, sapphire substrates do not act as oxygen source in the 600 °C regime and change the nitridation behaviour of the vanadium films.
Solid State Metathesis Reactions in Various Applications
Authors: Gibson Katharina , Ströbele Markus , Blaschkowski Björn , Glaser Jochen , Weisser Martina , Srinivasan Radhakrishnan , Kolb Heinz‐Jürgen , Meyer Hans‐Jürgen
Published: September 2003

Solid state metathesis reactions have been studied in fused silica tubes, by differential thermal analysis, and by X‐ray powder diffraction. A selection of reactions between metal (La, Nb, and Ni) chlorides and lithium nitride or lithium acetylide were investigated to get more insight into reaction pathways and intermediate reaction stages that may be adopted on course of the formation of metal nitrides or carbides. Intermediate compounds are considered to be important because they can control the reactivity of a system. Such compounds were traced by changing the molar ratios of reaction partners away from the salt‐balanced binary metal nitride or carbide target compositions.

New preparative perspectives are discovered when metal chlorides were reacted with lithium nitridoborate or lithium cyanamide. Due to their reductive nature towards several d‐block metal chlorides, (BN2)3‐ and (CN2)2‐ react to form metals or metal nitrides plus X‐ray amorphous BN, and probably C3N4. With lanthanum chloride they can react to form nitridoborates and nitridocarbonates. The metathesis reaction between lithium cyanamide and cyanuric chloride (C3N3Cl3) instead of metal chloride was studied for the synthesis of C3N4.
Investigations of Reactivity and Magnetic Properties of Nanostructured Iron Oxide within Mesoporous Silica Materials
Authors: Köhn Ralf , Fröba Michael
Published: September 2003

The change in reactivity for nanostructured iron oxide within mesoporous silica materials is demonstrated. Iron oxides were incorporated into the pore system of MCM‐41 and MCM‐48 silica materials and characterized by powder X‐ray diffraction and nitrogen physisorption. Iron oxide shows significant changes in the reducibility by hydrogen compared to comparable bulk iron oxide phases. Partially reduced iron oxides within the mesoporous host were characterized by X‐ray absorption spectroscopy and SQUID measurements.
Contributions on Thermal Behaviour and Crystal Chemistry of Anhydrous Phosphates. XXXIV [1] Oxygen Equilibrium Pressures in Ternary Systems M / P / O (M = Co, Ni) and Heats of Formation of Anhydrous Cobalt(II) and Nickel(II) Phosphates
Authors: Blum Matthias , Teske Klaus , Glaum Robert
Published: September 2003

Oxygen equilibrium pressures have been measured in the temperature range 800 °C to 1000 °C by coulometric/potentiometric techniques for several equilibrium regions in the ternary systems M / P / O (M = Co, Ni). In both systems oxygen coexistence pressures of three‐phase equilibrium solids phosphide/phosphate are about 3 to 5 orders of magnitude smaller than p(O2) above the corresponding Ms / MOs system.

Heats of formation ΔfH°298 and standard entropies S°298 for the phosphates have been obtained from 2nd and 3rd law evaluation of the temperature dependence of the oxygen coexistence pressures. Thermodynamic data from literature for the phosphides of cobalt and nickel and estimated heat capacities for the anhydrous phosphates Co3(PO4)2, Co2P2O7, Ni3(PO4)2, Ni2P2O7 and Ni2P4O12 were used for these calculations. Thus obtained enthalpies and entropies are compared to results from thermodynamic modelling of observed solid phase equilibria in the ternary systems M / P / O (M = Co, Ni).
Surface Core Level Shifts of Yb Films in the Multilayer, Monolayer and Submonolayer Range
Authors: Müller F. , Stöwe K.
Published: September 2003

Surface core level shifts in Yb and other rare earth elements, as well as in their compounds, arise from a reduced band width of the 5d band, caused by the reduced coordination at surface sites, with the strength and direction of the shifts depending on the occupation of the 5d band. If the coordination, or more exactly, the local symmetry is considered to be the decisive factor for changing the band width, it is obvious to look for core level shifts even at the interface of two solids. In order to investigate such interface core level shifts, thin Yb films of thicknesses from the multilayer down to the submonolayer range, grown on a polycristalline W substrat, were investigated by photoelectronspectroscopy. It was found, that for decreasing film thicknesses, the ratio of the surface to bulk related 4f intensities increases systematically, and finally, for thicknesses of one up to two monolayers, only the broad, surface related part of the Yb 4f doublet can be observed. For Yb coverages fewer than one monolayer, there is a sudden shift of this remaining doublet towards the Fermi energy, which must result from a reduced occupation of the Yb 5d band due to an electron transfer from Yb to W at the interface.
The Oxidation of Heterogeneous Tl/Ni/P‐Alloys — Preparation and Crystal Structures of the Thallium Nickel Phosphates TlNi4(PO4)3, Tl4Ni7(PO4)6, and Tl2Ni4(P2O7)(PO4)2
Authors: Panahandeh Ahmad , Jung Walter
Published: September 2003

Single crystals of the first anhydrous thallium nickel phosphates were prepared by reaction of heterogeneous Tl/Ni/P alloys with oxygen. TlNi4(PO4)3 (pale‐yellow, orthorhombic, space group Cmc21, a = 6.441(2)Å, b = 16.410(4)Å, c = 9.624(2)Å, Z = 4) crystallizes with a structure closely related to that of NaNi4(PO4)3. Tl4Ni7(PO4)6 (yellow‐brown, monoclinic, space group Cm, a = 10.711(1)Å, b = 14.275(2)Å, c = 6.688(2)Å, β = 103.50(2)°, Z = 8) is isotypic with Na4Ni7(PO4)6, and Tl2Ni4(P2O7)(PO4)2 (brown, monoclinic, space group C2/c, a = 10.389(2)Å, b = 13.888(16)Å, c = 18.198(3)Å, β = 103.1(2)°, Z = 8) adopts the K2Ni4(P2O7)(PO4)2 structure. Tl2Ni4(P2O7)(PO4)2 could also be prepared in nearly single phase form by reaction of Tl2CO3, NiO, and (NH4)2HPO4.
In Situ Study of the Surface Oxidation of FeCr Alloys Using Grazing Incidence X‐ray Absorption Spectroscopy (GIXAS)
Authors: Janssen Joachim , Rumpf Holger , Modrow Hartwig , Rablbauer Ralf , Frommeyer Georg , Hormes Josef
Published: September 2003

The surface oxidation of FeCr alloys with 18, 28, and 43 mass‐% Cr was investigated in situ using grazing‐incidence X‐ray absorption spectroscopy (GIXAS) at the chromium and iron K‐edges. Oxidation in air was monitored in situ in the temperature range from 290 K to 680 K. The standard GIXAS data analysis is extended for the treatment of a single layer model in order to estimate the chromium concentrations of the oxide layer and of the near‐interface substrate as well as the oxide layer thickness. XANES analysis shows transitions from b.c.c. Fe to corundum type Fe2O3 and from b.c.c. Cr to corundum type Cr2O3. The initial oxide layers are 1.1‐1.4 nm thick and contain 60‐90 mass‐% chromium, while the near‐interface substrate is depleted in Cr. During heating, iron oxide growth dominates up to 560‐600 K. Then the chromium oxide layer loses its passivation effect and Cr oxidation sets in.