bluuebunny/crossref_metadata_2025_split huggingface dataset:
The reproducible acquisition of comparative liquid chromatography/tandem mass spectrometry data from complex biological samples
Authors: Stewart Ian I. , Zhao Li , Le Bihan Thierry , Larsen Brett , Scozzaro Salvatore , Figeys Dan , Mao Guo Dong , Ornatsky Olga , Dharsee Moyez , Orsi Chris , Ewing Rob , Goh Theo 
Published: June 2004

AbstractAn in‐depth study of the reproducibility of data acquired for comparative proteomics analysis using a prototype two‐stage heated laminar flow chamber fitted to a commercial high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) instrument was undertaken. The study is based on 24 replicate samples from four independent membrane preparations derived from two matched breast cancer cell lines. Variation and reproducibility in the data were evaluated at several levels highlighting the relative efficiency and variability of the acquisition routines used. Specifically, variation in the number and relative intensities of chromatographic peaks eluted from the LC column, precursor ion selection and sequence identification were evaluated. On average, approximately 6500 chromatographic peaks were generated for each acquisition with a corresponding coefficient of variance (CV) of less than 20%. Precursor ion selection and sequence identification averaged 1380 and 780 events per acquisition sample, respectively, with corresponding CVs of less than 10% for each. The reproducibility in the precursor ion selection was typically better than 60% between similar replicates. Using protein and peptide internal standards, it was found that the CV in retention time across the gradient between two acquisition pairs was typically less than 5%, whereas the average intensity ratio was 1.0 (expected) with a CV approaching 20%. An evaluation of the intensity ratios calculated from endogenous peptide sequences, identified across the acquisition set, indicated a CV of ∼30%. Similarly, the CV associated with the top 1000 peptides indicated a mean and median of 28.4 and 26.95%. For a given acquisition pair it was also found that ∼11% of the chromatographic peaks eluting from the column were linked to a sequence or identified. For these experiments, less than 10% of the peak pairs had absolute ratios greater than 2.0 and of those only ∼10% had sequences linked to them. For each matched acquisition set on average 406 proteins were identified with a CV of less than 10%. Of the proteins that were identified approximately 30% had at least one predicted trans‐membrane domain, indicating a four‐fold increase over a crude homogenate sample with only minor enrichment. During these experiments it was found that the interface did not significantly alter the relative charge state distribution of ions, nor did it introduce significant interference from background ions. The interface was capable of 24‐hour acquisition cycles. Copyright © 2004 John Wiley & Sons, Ltd.
Robust Bayesian prediction of subject disease status and population prevalence using several similar diagnostic tests
Authors: Evans Richard B. , Erlandson Keith 
Published: June 2004

AbstractSometimes several diagnostic tests are performed on the same population of subjects with the aim of assessing disease status of individuals and the prevalence of the disease in the population, but no test is a reference test. Although the diagnostic tests may have the same biological underpinnings, test results may disagree for some specific animals. In that case, it may be difficult to determine disease status for individual subjects, and consequently population prevalence estimation becomes difficult. In this paper, we propose a robust method of estimating disease status and prevalence that uses heavy‐tailed sampling distributions in a hierarchical model to protect against the influence of conflicting observations on inferences. If a subject has a test outcome that is discordant with the other test results then it is downweighted in diagnosing a subject's disease status, and for estimating disease prevalence. The amount of downweighting depends on the degree of conflict among the test results for the subject. Copyright © 2004 John Wiley & Sons, Ltd.
Monitoring change in spatial patterns of disease: comparing univariate and multivariate cumulative sum approaches
Authors: Rogerson Peter A. , Yamada Ikuho 
Published: June 2004

AbstractProspective disease surveillance has gained increasing attention, particularly in light of recent concern for quick detection of bioterrorist events. Monitoring of health events has the potential for the detection of such events, but the benefits of surveillance extend much more broadly to the quick detection of change in public health. In this paper, univariate and multivariate cumulative sum methods for disease surveillance are compared. Although the univariate method has been previously used in the context of health surveillance, the multivariate method has not. The univariate approach consists of simultaneously and independently monitoring the disease rate in each region; the multivariate approach accounts explicitly for any covariation between regions. The univariate approaches are limited by their lack of ability to account for the spatial autocorrelation of regional data; the multivariate methods are limited by the difficulty in accurately specifying the multiregional covariance structure. The methods are illustrated using both simulated data and county‐level data on breast cancer in the northeastern United States. When the degree of spatial autocorrelation is low, the univariate method is generally better at detecting changes in rates that occur in a small number of regions; the multivariate is better when change occurs in a large number of regions. Copyright © 2004 John Wiley & Sons, Ltd.
Diagnostic test accuracy and prevalence inferences based on joint and sequential testing with finite population sampling
Authors: Su Chun‐Lung , Gardner Ian A. , Johnson Wesley O. 
Published: June 2004

AbstractThe two‐test two‐population model, originally formulated by Hui and Walter, for estimation of test accuracy and prevalence estimation assumes conditionally independent tests, constant accuracy across populations and binomial sampling. The binomial assumption is incorrect if all individuals in a population e.g. child‐care centre, village in Africa, or a cattle herd are sampled or if the sample size is large relative to population size. In this paper, we develop statistical methods for evaluating diagnostic test accuracy and prevalence estimation based on finite sample data in the absence of a gold standard. Moreover, two tests are often applied simultaneously for the purpose of obtaining a ‘joint’ testing strategy that has either higher overall sensitivity or specificity than either of the two tests considered singly. Sequential versions of such strategies are often applied in order to reduce the cost of testing. We thus discuss joint (simultaneous and sequential) testing strategies and inference for them. Using the developed methods, we analyse two real and one simulated data sets, and we compare ‘hypergeometric’ and ‘binomial‐based’ inferences. Our findings indicate that the posterior standard deviations for prevalence (but not sensitivity and specificity) based on finite population sampling tend to be smaller than their counterparts for infinite population sampling. Finally, we make recommendations about how small the sample size should be relative to the population size to warrant use of the binomial model for prevalence estimation. Copyright © 2004 John Wiley & Sons, Ltd.
The multiple‐record systems estimator when registrations refer to different but overlapping populations
Authors: Zwane Eugene N. , van der Pal‐de Bruin Karin , van der Heijden Peter G. M. 
Published: June 2004

AbstractIn multiple‐record systems estimation it is usually assumed that all registration relate to the same population. In this paper, we develop a method which can be used when the registrations relate to different populations, in the sense that they cover, for example, different time periods or regions. We show that under certain conditions ignoring that the registrations relate to different populations results in correct estimates of population size. The EM algorithm is presented as a method that can be used for more general problems. The parametric bootstrap is used to construct a confidence interval. The proposed method is then applied to a data set with five registrations of neural tube defects, that cover different time periods. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling associations between time‐to‐event responses in pilot cancer clinical trials using a Plackett–Dale model
Authors: Tibaldi Fabián , Barbosa Franz Torres , Molenberghs Geert 
Published: June 2004

AbstractThis work was motivated by the need to find surrogate endpoints for survival of patients in oncology studies. The goal of this article is to determine associations between five time‐to‐event outcomes coming from three clinical trials for non‐small cell lung cancer. To this end, we propose to use the multivariate Dale model for time‐to‐event data introduced by Tibaldiet al. (Stat. Med. 2003). We fit the model to these data, using a pseudo‐likelihood approach to estimate the model parameters.We evaluate and compare the performance of different dimensional models and we relate the Dale model association parameter, i.e. the odds ratio, to well‐known quantities such as Kendall's τ and Spearman's ρ. Finally, the results are discussed with a perspective on surrogate marker validation. Some suggestions are made regarding further studies in this field. Copyright © 2004 John Wiley & Sons, Ltd.
Learning to teach physics through inquiry: The lived experience of a graduate teaching assistant
Authors: Volkmann Mark J. , Zgagacz Marta 
Published: June 2004

AbstractThis investigation examines the difficulties encountered by one graduate teaching assistant as she taught Physics for Elementary Education, a large‐enrollment, inquiry‐based science course taught at a public Midwestern university. The methodological approach of hermeneutic phenomenology served as the lens to investigate the research question, “What is the lived experience of a graduate teaching assistant as she learned to teach physics through inquiry to elementary education students?” We summarize the findings in terms of the blending of two conceptual frameworks: orientations to science teaching and professional identity. We learned that fundamental beliefs about the nature of science support certain orientations, and if those beliefs remain unchallenged, then the orientation is unlikely to change. Finally, we discuss implications for strategies that may assist college‐level instructors with changing their orientation to teaching science. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 584–602, 2004
Zwei Mercuri‐Ammin‐Komplexe: [Hg(NH3)2][HgCl3]2 und [Hg(NH3)4](ClO4)2
Authors: Nockemann Peter , Meyer Gerd 
Published: June 2004

Abstract[Hg(NH3)2][HgCl3]2 (1) wird durch Sättigen einer äquimolaren wässrigen Lösung von HgCl2 und NH4Cl mit Hg(NH2)Cl bei 75 °C dargestellt. 1 kristallisiert orthorhombisch in der Raumgruppe Pmna mit den Gitterparametern a = 591, 9(1) pm, b = 800, 3(1) pm, c = 1243, 3(4) pm, Z = 2. Die Struktur besteht aus linearen [Hg(NH3)2]2+‐Einheiten und T‐förmigen [HgCl3]—‐Anionen. Die Koordinationssphären des Quecksilbers werden durch Chlorid‐Ionen „effektiv”︁ zu gestauchten hexagonalen Bipyramiden bzw. zu verzerrten Oktaedern ergänzt. Einkristalle von [Hg(NH3)4](ClO4)2 (2) wurden durch Einleiten von gasförmigem Ammoniak in eine auf unter 10 °C gekühlte Quecksilber(II)‐perchlorat‐Lösung erhalten. 2 kristallisiert monoklin in der Raumgruppe P21/c mit den Gitterparametern a = 791, 52(9) pm, b = 1084, 3(2) pm, c = 1566, 4(2) pm, β = 120, 352(1)°, Z = 4. Die Struktur besteht aus gestauchten [Hg(NH3)4]2+‐Tetraedern und Perchlorat‐Anionen. Die Packung der Schweratome Hg und Cl ist demBaddeleyit‐(α‐ZrO2)‐Typ analog.
X‐Ray Single Crystal Refinement and Superconductivity of La3Ni2B2N3
Authors: Blaschkowski Björn , Meyer H.‐Jürgen 
Published: June 2004

AbstractCrystalline samples of La3Ni2B2N3 were synthesized using solid state metathesis reactions from combinations of La, LaCl3, NiCl2 together with Li3BN2. The structure was determined by single crystal X‐ray diffraction (I4/mmm (No. 139), a = 372.95(2) pm, c = 2056.3(2) pm, R1 = 0.027, wR2 = 0.062) and confirmed earlier results from neutron powder diffraction. La3Ni2B2N3 contains BN units capping square planar Ni layers. Isolated nitrogen atoms reside in La6 octahedra. Magnetic measurements on several bulk samples exhibit superconductivity at temperatures below 14.6 K.
Synthesis and Spectroscopic Characterization of a Complex of 1, 10‐Phenanthroline with Magnesium
Authors: Dimitrov Georgi D. , Atanassova Maria S. 
Published: June 2004

AbstractThe complex [Mg(1, 10‐phenanthroline)3(NO3)2]·9H2O has been synthesized. It forms crystals having the shape of sheaves with very thin filaments. The compound has been characterized by UV, IR, NMR and mass spectra. The UV and mass spectra are indicative of an electron density transfer from NO3— to Mg2+. On the base of the spectroscopic studies a model of the crystal structure has been proposed.
Syntheses and Structures of Trilithium Cyclotriphosphazenates Equipped with 2‐Halo‐aryl Substituents
Authors: Rivals Frederic , Steiner Alexander 
Published: June 2004

AbstractHexakis (2‐halo‐anilino) cyclotriphosphazenes (2‐X‐C6H4NH)6P3N3 {X = F (1d), Cl (1e), Br (1f)} were prepared by refluxing mixtures of hexachloro cyclotriphosphazene, 2‐haloaniline and triethylamine in toluene and characterized by single crystal X‐ray diffraction. 1d, 1e and 1f were reacted with nBuLi in thf. Reactions were monitored with 31P NMR. Addition of three equivalents of nBuLi yields lithium complexes of trianionic phosphazenates [{(thf)2Li}3{(2‐X‐C6H4N)3(2‐X‐C6H4NH)3P3N3}] {X= F (2d), Cl (2e) and Br (2f)}. 2d, 2e and 2f were structurally characterized by X‐ray diffraction, which reveals monomeric cis‐metalated phosphazenates featuring central P3N3 ring systems of chair conformation. Lithium ions reside in three N(eq)‐P‐N(endo) chelation sites at one face of the P3N3 ring system. Li…X distances are rather long (> 3Å) indicating no Li‐X interactions.
Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 36 [1] Parametrische Analyse der optischen Spektren eines orientierten Tris(hydrotris(1‐pyrazolyl)borato)praseodym(III)‐Einkristalls
Authors: Amberger Hanns‐Dieter , Reddmann Hauke , Apostolidis Christos , Kanellakopulos Basil 
Published: June 2004

AbstractDie Absorptions‐ und Lumineszenzspektren von polykristallinem Tris(hydrotris(1‐pyrazolyl)borato)‐praseodym(III) (PrTp3) wurden sowohl bei Raumtemperatur als auch bei tiefen Temperaturen vermessen. Bei Raumtemperatur konnten zusätzlich die „polarisierten”︁ Lumineszenzspektren eines kleinen orientierten PrTp3‐Einkristalls aufgenommen werden. Auf der Grundlage dieser spektroskopischen Befunde konnte das zugrundeliegende Kristallfeld‐Aufspaltungsmuster abgeleitet und durch Anpassung der offenen Parameter eines phänomenologischen Hamilton‐Operators simuliert werden, wobei eine reduzierte r.m.s.‐Abweichung von 17.3 cm—1bei 37 Zuordnungen erzielt wurde. Auf Basis dieser Parameter werden sowohl die vom Pr3+‐Zentralion wahrgenommene globale, als auch die von einem Tp‐Liganden hervorgerufene individuelle Ligandenfeldstärke bestimmt, nephelauxetische und relativistische nephelauxetische Effekte abgeschätzt sowie die experiment‐orientierten nichtrelativistischen und relativistischen Molekülorbital‐Schemata im f‐Bereich aufgestellt.
A New Monomer for π‐Conjugated Polymers — Synthesis and Characterization of Bis((Z)‐5‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole‐4‐yl)monosulfane
Authors: Schäper Jan , Hahn Josef , Pantenburg Ingo , Scherer Harald 
Published: June 2004

AbstractBis((Z)‐5‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole‐4‐yl)monosulfane (6), a molecule consisting of two diphenyldithiafulvene units connected by a sulfur bridge, was synthesized by the selective lithiation of (Z)‐4‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole (7a) at the endocyclic double bond and by subsequent reaction of the lithiated intermediate with bis(phenylsulfonyl)sulfane. Since this reaction sequence proceeded with retention of configuration, of three possible isomers (E, E, Z, E, and Z, Z) only the Z, Z form was obtained. On the basis of the X‐ray structure analysis and the NMR‐spectroscopic characterization of 6 supplemented by the NMR parameters of (E)‐ and (Z)‐4‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole, it was demonstrated that two characteristic 5J coupling constants of the proton at the exocyclic double bond indicate the configuration (Z or E) of disubstituted dithiafuvene derivatives.
Synthesis and Crystal Structure of Bis(methyltriphenylphosphonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [PMePh3]2[TeBr6(SeBr2)2], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion
Authors: Janickis Vitalijus , Herberhold Max , Milius Wolfgang 
Published: June 2004

AbstractBrown crystals of [PMePh3]2[TeBr6(SeBr2)2] (1) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr6(SeBr2)2]2— anion contains a nearly regular [TeBr6] octahedron where the four equatorial bromo ligands each have developed a bond to the SeII atom of a SeBr2 molecule. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV—Br distances are in the range 2.67—2.72Å, and the SeII—Br bond lengths in coordinated SeBr2 molecules in the range 2.33—2.34Å.
(C2H10N2)[BPO4F2] — Structural Relations between [BPO4F2]2— and [Si2O6]4—
Authors: Huang Ya‐Xi , Schäfer Gerd , Borrmann Horst , Zhao Jing‐Tai , Kniep Rüdiger 
Published: June 2004

Abstract(C2H10N2)[BPO4F2] — Strukturbeziehungen zwischen [BPO4F2]2— und [Si2O6]4—Colourless crystals of (C2H10N2)[BPO4F2] were prepared from mixture of ethylendiamine, H3BO3, BF3 · C2H5NH2, H3PO4 and HCl under mild hydrothermal conditions (220 °C). The crystal structure was determined by single crystal methods (triclinic, P1¯ (no. 2), a = 451.85(5) pm, b = 710.20(8) pm, c = 1210.2(2) pm, α = 86.08(1)°, β = 88.52(2)°, γ = 71.74(1)°, Z = 2) and contains infinite tetrahedral zweier‐single‐chains {[BPO4F2]2—} which are isoelectronic (48e—) with the polyanions {[Si2O6]4—} of the pyroxene family.
Darstellung, Charakterisierung und Reaktionsverhalten von Natrium‐ und Kaliumhydridosilylamiden R2(H)Si—N(M)R′ (M = Na, K) — Kristallstruktur von [(Me3C)2(H)Si—N(K)SiMe3]2·THF
Authors: Schneider Jan , Popowski Eckhard , Reinke Helmut 
Published: June 2004

AbstractDie Alkalimetallhydridosilylamide R2(H)Si—N(M)R′ 1a‐Na—1d‐Na und 1a‐K—1d‐K (a: R = Me, R′ = CMe3; b: R = Me, R′ = SiMe3; c: R = Me, R′ = Si(H)Me2; d: R = CMe3, R′ = SiMe3) wurden durch Reaktion der entsprechenden Hydridosilylamine 1a—1d mit dem Alkalimetall M (M = Na, K) in Gegenwart von Styrol oder mit Alkalimetallhydrid MH (M = Na, K) dargestellt. Mit NaNH2 in Toluol reagierte Me2(H)Si—NHCMe3 (1a) nicht unter Metallierung, sondern unter nucleophiler Substitution des H(Si)‐Atoms zum Amid Me2(NaNH)Si—NHCMe3 (5). Die Reaktion von Me2(H)Si—NHSiMe3 (1b) mit NaNH2 in Toluol ergab ein Gemisch von Me2(NaNH)Si—NHSiMe3 und Me2(H)Si—N(Na)SiMe3 (1b‐Na). Die Hydridosilylamide wurden spektroskopisch charakterisiert. Die spektroskopischen Daten dieser Amide und der entsprechendenLithiumderivate werden diskutiert. Die 29Si‐NMR‐chemischen Verschiebungen und die 29Si—1H‐Kopplungskonstanten homologer Alkalimetallhydridosilylamide R2(H)Si—N(M)R′ (M = Li, Na, K) sind vom Alkalimetall abhängig. Mit Zunahme des ionischen Bindungsanteils in der M—N‐Bindung M = K > Na > Li erfahren die 29Si‐NMR‐Signale eine Hochfeldverschiebung und die 29Si—1H‐Kopplungskonstanten werden mit Ausnahme der Verbindungsreihe (Me3C)2(H)Si—N(M)SiMe3 kleiner. Von den Amiden 1a‐Na—1c‐Na und 1a‐K—1c‐K wurde das Reaktionsverhalten gegenüber Chlortrimethylsilan in Tetrahydrofuran (THF) und n‐Pentan untersucht. In THF reagieren die Amide wie die analogen Lithiumamide in hohen Ausbeuten zu den entsprechenden N‐silylierten Verbindungen Me2(H)Si—N(SiMe3)R′ (2a—2c). Die Umsetzung der Natriumamide mit Chlortrimethylsilan im unpolaren Lösungsmittel n‐Pentan ergibt aus 1a‐Na das Cyclodisilazan [Me2Si—NCMe3]2 (8a), aus 1b‐Na und 1c‐Na Gemische von Cyclodisilazan [Me2Si—NR′]2 (8b, 8c) und N‐silylierter Verbindung 2b, 2c. Im Gegensatz zu 1b‐Na und 1c‐Na sowie den analogen Lithiumamiden reagieren 1b‐K und 1c‐K mit Chlortrimethylsilan in n‐Pentan in hoher Ausbeute zu den N‐Silylierungsprodukten 2b, 2c.Das Amid [(Me3C)2(H)Si—N(K)SiMe3]2·THF (9) kristallisiert in der Raumgruppe C2/c mit Z = 4. Die zentrale Einheit des Moleküls ist ein planarer K2N2‐Vierring. Ein Kaliumatom ist durch zwei Stickstoffatome, das andere durch zwei Stickstoffatome und ein Sauerstoffatom koordiniert. Weiterhin bestehen in 9 K···H(Si)‐ und K···CH3‐Kontakte. Die K—N‐Abstände im K2N2‐Ring unterscheiden sich nur unwesentlich.
Ein Praseodymsalz der Dichloressigsäure: [Pr(HCl2C—COO)3(H2O)3]2(HCl2C—COOH)(H2O)2
Authors: Meyer Gerd , Bromant Claudia 
Published: June 2004

AbstractA Praseodymium Salt of Dichloroacetic Acid: [Pr(HCl2C—COO)3(H2O)3]2(HCl2C—COOH)(H2O)2The new dichloroacetate of praseodymium, [Pr(HCl2C—COO)3(H2O)3]2(HCl2C—COOH)(H2O)2, crystallizes from the solution of „Pr6O11”︁ in dichloroacetic acid. The crystal structure (monoclinic, P21/n, Z = 4, a = 1598.4(2), b = 1600.8(2), c = 1650.8(2) pm, β = 105.57(1)°) contains dimeric building units of the composition [Pr2(HCl2C—COO)6(H2O)6] which are connected to chains. An additional dichloroacetic acid molecule and two crystal water molecules are included between these chains.