bluuebunny/crossref_metadata_2025 huggingface dataset:
Supercritical carbon dioxide extraction of marigold at high pressures: comparison of analytical and pilot‐scale extraction
Authors: Baumann Dietmar , Adler Sven , Grüner Sabine , Otto Frank , Weinreich Bernd , Hamburger Matthias
Published: June 2004

The effects of pressure and co‐solvent on the extraction of anti‐inﬂammatory faradiol esters in marigold (Calendula ofﬁcinalis L.) were investigated by supercritical ﬂuid extraction at laboratory and pilot scales. Pressures higher than 300 bar and modiﬁer (ethanol) concentrations ranging from 0 to 20% (v/v) were used at an extraction temperature of 50 °C. With an analytical extractor, exhaustive extraction of the drug and highest concentrations in the extracts were achieved with 0.5% ethanol at the maximum pressure of 689 bar. Increased modiﬁer concentrations improved the extractability at lower pressure, but the higher amount of total extractables led to a lower concentration of faradiol esters in the extracts. The HPLC ﬁngerprints of the extracts, the yields of total extract and the concentration of faradiol esters obtained with analytical and pilot scale extractors under the same conditions were comparable. Copyright © 2004 John Wiley & Sons, Ltd.
The addition reaction of diamides to 1,2,5‐thiadiazole 1,1‐dioxide derivatives
Authors: Caram José A. , Mirífico María V. , Aimone Silvia L. , Piro Oscar E. , Castellano Eduardo E. , Vasini Enrique J.
Published: June 2004

The reactions of several derivatives of 1,2,5‐thiadiazole 1,1‐dioxide [3,4‐diphenyl‐(1a), 3,4‐bis(p‐methoxyphenyl)‐(1b), phenanthro[9,10‐c]‐(1c) and acenaphtho[1,2‐c]‐1,2,5‐thiadiazole 1,1‐dioxide (1d), 3,4‐diphenyl‐1,2,5‐thiadiazoline 1,1‐dioxide (2a) and 4‐ethoxy‐5‐methyl‐3,4‐diphenyl‐1,2,5‐thiadiazoline 1,1‐dioxide (2b)], with reagents possessing two nucleophilic nitrogen atoms (urea, N,N′‐dimethylurea, thiourea, N‐methylthiourea, N‐ethylthiourea, N‐allylthiourea, N,N′‐diethylthiourea, N,N′‐diphenylthiourea, dithioxamide and sulfamide), were followed by cyclic voltammetry (CV) and UV–visible spectrophotometry in aprotic solvent solution. The products were isolated, characterized by IR, 1H NMR and 13C NMR methods and their structure was confirmed by single‐crystal x‐ray diffraction. Several substrate–nucleophile combinations (1a–d and 2a with some ureas and thioureas) reacted to give good yields of new compounds formed by the addition reaction of the two nitrogen atoms of the nucleophile to the two >CN— double bonds of the 1,2,5‐thiadiazole 1,1‐dioxide ring. Some systems (1a–dithioxamide and 2b–thiourea) did not react, whereas in others (e.g. 1a–sulfamide) a monoaddition equilibrium reaction was observed. Copyright © 2004 John Wiley & Sons, Ltd.
Solid‐phase incorporation of gaseous carbon dioxide into oxirane‐containing copolymers
Authors: Ochiai Bungo , Iwamoto Tokinori , Miyagawa Toyoharu , Nagai Daisuke , Endo Takeshi
Published: June 2004

Carbon dioxide was incorporated into poly(glycidyl methacrylate‐co‐methyl methacrylate) by a solid‐phase reaction, which transformed the pendent oxirane moieties into cyclic carbonate moieties, with quaternary ammonium halide catalysts. The incorporation of carbon dioxide into the copolymer led to soluble carbonate‐containing polymers, whereas the incorporation of carbon dioxide into the glycidyl methacrylate homopolymer produced an insoluble product. The copolymer composition, reaction temperature, and catalyst amount affected the incorporation efficiency and the side reaction that caused crosslinking. Effective incorporation was achieved under the following reaction conditions: the glycidyl methacrylate content was less than approximately 50%, the temperature was greater than the glass‐transition temperature, and the catalyst concentration was 1.5–6 mol %. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3812–3817, 2004
Integrated inherent safety index (I2SI): A tool for inherent safety evaluation
Authors: Khan Faisal I. , Amyotte Paul R.
Published: June 2004

Inherent safety is a proactive approach for loss prevention and risk management. Considering the lifetime costs of a process and its operation, an inherent safety approach can lead to a cost‐optimal option. Inherent safety may be achieved at any stage of process design; however, its application at the early stages of process design yields the best results. Despite being an attractive and cost‐effective approach, the inherent safety methodology is not widely used. Many reasons have been attributed to this lack of widespread use; the nonavailability of systematic tools for the application of inherent safety principles is perhaps the most important reason.

This paper presents a conceptual framework of an integrated inherent safety index (I2SI). It is called an integrated index because the procedure, when fully developed, is intended to consider the life cycle of the process with economic evaluation and hazard potential identification for each option. The I2SI is composed of subindices which account for hazard potential, inherent safety potential, and add‐on control requirements. An application of the I2SI is also discussed. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 136–148, 2004
A major incident prevention program: Ten years of experience12
Authors: Renshaw Frank M.
Published: June 2004

This paper reviews one chemical company's experience in conducting Major Incident Prevention Program studies over the past 10 years in 90 bulk storage and processing units. The value and limitations of dispersion modeling, recurring findings from good practices and emergency response reviews, and dominant strategies for consequence and frequency reduction are outlined. The challenge and benefits posed by the use of quantitative criteria in evaluating and managing residual risk of ongoing operations are also discussed. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 155–162, 2004
One‐electron pseudopotential calculations of electronic properties of NaArn: Low‐energy isomers and absorption spectra
Authors: El Hadj Rhouma M. Ben , Berriche H. , Lakhdar Z. Ben , Spiegelman F.
Published: June 2004

We present a calculation of geometric structures and optical transitions in NaArn clusters. The energy of the system in its ground state is described using additive potentials with VNa‐Ar and VAr‐Ar representing the pair interactions. To find the geometry of the lowest‐energy isomers of NaArn clusters, we use the so‐called basin‐hopping method. The electronic structure of the metal valence electrons in the environment of the rare gas atoms is determined via a procedure close to the ab initio methodology involving e‐Na+ and e‐Ar semilocal pseudopotentials complemented by core polarization operators. The results shows that the absorption spectral features are sensitive to isomer structure. It is clearly the case for transitions close to the 3p levels of Na, which are distorted by the cluster environment. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Theoretical approach for simulation of femtosecond spectra: New strategies for optimal control of complex systems
Authors: Bonac̆ić‐Koutecký V. , Mitrić R. , Hartmann M. , Pittner J.
Published: June 2004

We present the ab initio Wigner distribution approach for simulation of femtosecond pump–probe and pump–dump signals and the new strategy for tailoring the light pulses that allow for optimal control of ultrafast processes. Our ab initio Wigner distribution approach combines the Wigner–Moyal representation of the vibronic density matrix with the ab initio multistate adiabatic and nonadiabatic molecular dynamics “on the fly” involving ground and excited electronic states. This approach allows for accurate simulations of femtosecond signals based on analytic formulation for systems of moderate complexity taking into account all degrees of freedom. For this purpose the following items are needed: (1) temperature‐dependent ground‐state initial conditions; (2) an ensemble of trajectories for the investigation of the dynamics of the system either on the adiabatic electronic excited state or on both the excited and ground states through nonadiabatic coupling; and (3) either the cationic or neutral ground state for the probing step. The goal of optimal control of femtosecond processes is to tailor pump–dump pulses that drive the system via electronically excited state to the desired ground‐state objective with the maximal yield. For the multidimensional systems this is possible only if the connective pathway between initial state and the objective can be ensured and the optimal pathway can be found. We show that these requirements are fulfilled by introducing the concept of the intermediate target in the excited state. Its role is to select the appropriate parts of energy surfaces at the given time delay between the two pulses, allowing us to reach optimally the objective. We illustrate the scope of our approach on nonstoichiometric halide deficient NanFn−1 clusters, which are characterized by strong ionic bonding and one excess electron. The choice of the systems has been made to determine timescales of different processes in the excited states and apply the new strategy for optimal control. This involves the bond breaking leading to (1) periodic geometric rearrangements such as in the case of Na2F or (2) nonadiabatic radiationless decay through conical intersection between the first excited state and the ground state occurring for Na3F2. In the latter case we optimize and analyze the pump and dump pulses to drive the isomerization process in the Na3F2 cluster to the second isomer by suppressing radiationless transition through conical intersection. The shaped pump–dump pulses serve as guidance for the experimental work in progress. Population of one of the two isomers allows us to establish a molecular switch. Such bimodal type of behavior might provide a basic element for information storage. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Using simply contracted basis functions with the Lanczos algorithm to calculate vibrational spectra
Authors: Wang Xiao‐Gang , Carrington Tucker
Published: June 2004

We demonstrate that the combination of simply contracted basis functions and the Lanczos algorithm yields an extremely efficient method for computing vibrational energy levels. We discuss ideas and present some results for HOOH and CH4. The basis functions we use are products of eigenfunctions of reduced‐dimension Hamiltonians obtained by freezing coordinates at equilibrium. The basis functions represent the desired wave functions well yet are simple enough that matrix–vector products may be evaluated efficiently. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Theoretical vibrational spectra of organic ring compounds compared to experiment
Authors: Förner Wolfgang
Published: June 2004

We have studied vibrational infrared (IR) and Raman spectra of several organic ring compounds. These include first cyclobutanecarboxaldehyde (CBA) and cyclohexanecarboxaldehyde (CHA) using density functional theory (DFT) together with a Becke‐3 exchange and Lee–Yang–Parr correlation (B3LYP) functional. DFT in these systems gives a stable and low‐energy gauche‐axial (g‐ax) conformer for both of the molecules together with the experimentally found equatorial conformations. However, on the basis of comparison of the theoretical vibrational spectra of the conformational mixture at 300 K with experimental spectra, the presence of the g‐ax conformer could be ruled out because it would yield extra lines not present in the corresponding experimental spectra. Thus, we concluded that DFT yields properties related to energy derivatives such as minimum geometries and vibrational spectra in fair agreement with experiment, while total energy differencies are not trustworthy when they are small, especially if small linear dependencies in the atomic basis sets applied appear. However, in that case we found that Møller–Plesset perturbation theory of second order (MP2) applied to CBA has the same problems and even does not predict the absolute minimum on the potential hypersurface correctly. Therefore, we applied DFT also to biphenyle (BP) and terphenyle (TP). Again, in BP and TP DFT turned out to yield reliable structures that as far as the important torsional angle between the rings is concerned are even better than MP2. Also, the vibrational spectra are in fair agreement with experimental ones. In BP restricted Hartree–Fock (RHF), DFT and experimental IR spectra all show two intense absorptions around 700 cm−1, while MP2 gives only one intense absorption band in this region. DFT also reproduces the position of these two lines well. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Application of accurate MP2 energies for closed‐shell atoms in examinations of density functionals for 3d10 electron ions
Authors: Jankowski K. , Nowakowski K. , Słupski R. , Flores J. R.
Published: June 2004

Arguments are presented that accurate second‐order Møller–Plesset (MP2) energies, evaluated in calculations involving extensive radial and angular basis sets, followed by careful angular extrapolations (referred to as MP2/CA energies), provide reliable approximations to the correlation energies for the ground states of closed‐shell atomic systems. MP2/CA energies are calculated for the members of the Cu+ isoelectronic series (Cu+, Zn2+, Ge4+, and Kr8+), which belong to the simplest atomic system containing the 3d10 configuration. The most accurate ab initio correlation energies for a 28‐electron isoelectronic series are reported. To exemplify the applicability of the total nonrelativistic energies, obtained as a sum of these energies and accurate Hartree–Fock energies, in examinations of density functionals, density functional theory energies are calculated for various functionals and basis sets and compared with their MP2/CA counterparts. An evaluation of the performance of these functionals is presented. The impact of the limited basis set size on the energy results is estimated. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Extension of the molecular quantum defect orbital methodology to the calculation of intensities and lifetimes for vibronic transitions within electronic Rydberg series of NO
Authors: Velasco A. M. , Bustos E. , Martín I. , Lavín C.
Published: June 2004

Expressions relating explicitly the radiative lifetimes of vibronic states to the electronic transition moment and the absorption oscillator strengths for spin‐allowed transitions have been developed for the first time within the molecular quantum defect orbital (MQDO) methodology. Application to the intensities of the γ(A2Σ+ ← X2Π), ε(D2Σ+ ← X2Π), and (D2Σ+ ← A2Σ+) bands of NO, which are known to be of relevance in atmospheric studies, has been made. The MQDO results are in excellent accord with the measurements available in the literature. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Nonlinear oscillations in the molecular dimer: Asymptotic solutions
Authors: Maximov S. G. , Kuzmenkov L. S. , Guardado Zavala J. L.
Published: June 2004

Nonlinear oscillations in the molecular dimer, composed of two monomers, are investigated, considering an arbitrary number of excitons in the system. The bosonic operators are used to describe the exciton dynamics, that leads to value of the radius of a Bloch sphere that differs from known results. The Hamiltonian of the system is used to reduce the system of equations of motion to a single nonlinear ordinary differential operator equation of the fourth order. Then, the energy of the system is involved in this equation as a parameter. The stability problem is investigated for different energy values. A bifurcation occurs for the energies E > −1/2p. The asymptotic quasiclassical solution for the case E > −1/2p is obtained. The solution contains the number of excitons as a parameter. The quantum solutions can be obtained from the classical solutions using the continual integral technique. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
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

An 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

Sometimes 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

Prospective 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

The 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

In 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

This 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.
Multivariate estimation of the relative dose potency
Authors: Källén Anders
Published: June 2004

As a follow‐up to a previous publication we illustrate how multivariate analysis of dose–response trials can be done, providing single number, relative dose potency, results for the comparison between two treatments, also when a number of variables are measured. 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

This 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

[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

Crystalline 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

The 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

Hexakis (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

Die 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

Bis((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

Brown 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

(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

Die 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

A Praseodymium Salt of Dichloroacetic Acid: [Pr(HCl2C—COO)3(H2O)3]2(HCl2C—COOH)(H2O)2

The 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.
Regioselectivity of 5, 6, 7, 8‐Tetrafluoroquinoline and 6‐X‐Trifluoroquinoline (X = CF3, H) in Reactions with Nucleophiles
Authors: Panteleeva Elena V. , Shteingarts Vitalij D. , Grobe Joseph , Krebs Bernt , Triller Michael U. , Rabeneck Helmut
Published: June 2004

A systematic study of the direction of nucleophilic attack of the nucleophiles Me3MEMe2 (M = Si, Sn; E = P, As), NaOMe, LiR (R = Me, nBu, Ph) and PhMgBr on 5, 6, 7, 8‐tetrafluoroquinoline (1), 6‐CF3‐5, 7, 8‐trifluoroquinoline (2) and 5, 7, 8‐trifluoroquinoline (3) was performed with the aim to develop synthetic routes to specific functional derivatives and to gain a deeper insight into the mechanisms governing the regioselectivity. With the fairly “soft” nucleophiles Me3MEMe2 in general mixtures of 7‐Me2EC‐(main product) and 6‐Me2EC‐derivatives (side product) are formed (Schemes 1, 2, 4). Sulfuration of the isomer mixtures with E = P yields mixtures of the corresponding thiophosphano derivatives. The observed regioselectivity is explained by a concerted action of two factors: (i) The influence of the heteroatom N on the stabilization of the σ‐complex type transition states and (ii) the collective effect of four fluorine substituents favouring 6‐ and 7‐substitution. — The reaction of 1 with sodium methoxide (Scheme 3) was carried out to test the early conclusion on the exclusive formation of 7‐methoxy‐5, 6, 8‐trifluoroquinoline (14) [2], made on the basis of a GC‐analysis. For that purpose the molar ratio 1 : MeO— was varied from 1 : 1.25 over 1 : 1 to 1 : 0.5. — In the reactions of the quinoline precursors 1—3 with the organometallic reagents LiR (R = Me, nBu, Ph) and PhMgBr (Scheme 5) products of the nucleophile‐addition at position 2 were obtained in high yields, which with hydrochloric acid led to 2‐R‐1, 2‐dihydro‐5, 6, 7, 8‐tetrafluoroquinolines. In contact with air or by reaction with MnO2, oxidation to aromatic 2‐R‐5, 6, 7, 8‐tetrafluoroquinolines occurred. To rationalize the observed differences between the “soft” Me3MEMe2 and the “hard” carbon‐centred nucleophiles, two different hypothetic mechanisms are discussed. Since most of the compounds have been obtained in reaction mixtures, the assignment to structural formulae is mainly based on GCMS and CMS analyses together with 1H‐, 19F‐ and 31P NMR data and comparison with literature information and with spectra registered for individual compounds. In addition, the molecular structures of the representatives 6, 20 and 29, determined by X‐ray analyses, prove the structural formulae deduced from the spectra of products.
Polysulfonylamine. CLX [1] Kristallstrukturen von Metall‐di(methansulfonyl)amiden. 10 [2] Die dreidimensionalen Koordinationspolymere M[(CH3SO2)2N] mit M = Kalium, Rubidium, Caesium (isotype Strukturen für M = K, Rb)
Authors: Moers Oliver , Latorre Violeta , Nagel Karl‐Heinz , Blaschette Armand , Jones Peter G.
Published: June 2004

Es werden Tieftemperatur‐Röntgenstrukturen mitgeteilt für KA (monoklin, Raumgruppe P21/c, Z′ = 1), RbA (isotyp und isostrukturell mit KA) und CsA (monoklin, P21/n, Z′ = 1), wobei A— das Anion der starken Stickstoffsäure (MeSO2)2NH bezeichnet. In KA und RbA hat das Anion eine seltene C1‐Konformation, in CsA die Standardkonformation mit zweizähliger Symmetrie. Sämtliche Strukturen beruhen auf dreidimensionalen Koordinationsnetzwerken, in welchen die Kationen durch Wechselwirkungen mit einem (O, N)‐ und einem (O, O)‐chelatisierenden sowie drei κ1 O‐bindenden Anionen eine unregelmäßige (O6N)‐Heptakoordination erreichen; darüber hinaus erhöht sich die Koordinationszahl des Cs+‐Ions infolge eines sehr kurzen (Cs···Cs)‐Kontaktabstands von 422, 5 pm auf den effektiven Wert acht. Die Kristallpackungen der isotypen Verbindungen KA und RbA weisen substrukturelle lamellare Schichten auf; diese bestehen aus einer inneren Kationlamelle sowie Anion‐Monoschichten als äußeren Umhüllungen und werden von sechs unabhängigen Ligand‐Metall‐Bindungen zusammengehalten, während die letzte unabhängige M—O‐Bindung die Schichten zur endgültigen 3D‐Struktur quervernetzt. Im Gegensatz dazu existieren in der Packung von CsA zickzackförmige planare Kationketten (Cs···Cs alternierend 422, 5 und 487, 5 pm, Cs···Cs···Cs 135, 7°); die Ketten sind zwischen Anion‐Monoschichten in der Weise intercaliert, daß jede von vier Anionstapeln umgeben und koordiniert wird und jeder Anionstapel zwei Kationketten miteinander verknüpft. In allen Strukturen treten schwache Wasserstoffbrücken des Typs C—H···A auf.
Synthesis and Molecular Structure of [n‐Bu2(F)SnOSn(F)t‐Bu2]2 — an Unsymmetrically Substituted Tetraorganodistannoxane
Authors: Beckmann Jens , Dakternieks Dainis , Duthie Andrew , Jurkschat Klaus , Schürmann Markus
Published: June 2004

The dimeric tetraorganodistannoxane [n‐Bu2(F)SnOSn(F)t‐Bu2]2 (1) was prepared by the reaction of (t‐Bu2SnO)3 with n‐Bu2SnF2 and characterized in solution by multinuclear NMR spectroscopy and ESI MS spectrometry and in the solid state by 119Sn MAS NMR spectroscopy and single crystal X‐ray diffraction.
Molekül‐ und Kristallstruktur von Quecksilber(II)‐α‐Amino‐γ‐methylmercapto‐butyrat, Hg(Met)2
Authors: Meyer Gerd , Nolte Matthias
Published: June 2004

Molecular and Crystal Structure of Mercuric α‐Amino‐γ‐methyl‐mercapto‐butyrate, Hg(Met)2

The mercuric salt of deprotonated methionine, Hg(Met)2, was obtained as colourless needles from aqueous solutions of methionine and HgCl2 or HgO, respectively. The crystal structure (monoclinic, P21, Z = 2, a = 984, 2(2), 507, 96(6), c = 1574, 2(3) pm, β = 93, 05(2)°; Rall = 0, 055) exhibits formula‐like molecules with strong Hg—N coordination at a distance of 216 pm; one oxygen atom adds to a chelate like N—Hg—O coordination. Stacking of these molecules adds two oxygen atoms of different methionate anions to an effective 2+2+2 „octahedral”︁ coordination around the mercuric ion. Thereby a layer structure parallel (001) is formed with the methyl‐mercapto function on top and bottom of these layers.
Stridulation variability and morphology: an examination in dung beetles of the genus Trypocopris (Coleoptera, Geotrupidae)
Authors: Carisio Loredana , Palestrini Claudia , Rolando Antonio
Published: June 2004

Distress signals produced by dung beetles of the genus Trypocopris (Coleoptera, Geotrupidae) were analysed to test whether interspecific and intraspecific acoustic variability are species‐ and subspecies‐specific and to ascertain to what extent bioacoustic parameters depend upon the morphology of the stridulatory organs (pars stridens). Bioacoustic analyses showed that the three species were clearly differentiated, despite the fact that disturbance stridulations presented the same stereotyped spectrographic pattern. Within each species, most of the subspecies and populations considered were also bioacoustically distinguishable. Subspecies and populations within each species were differentiated with regard to body size and stridulatory organ, and the length of the pars stridens was positively correlated with the width of the coxa, in turn positively correlated with body size. A few spectrographic measures were significantly constrained by the morphology of the stridulatory apparatus; in particular the duration of sound emission was positively correlated with the length of the apparatus and the sub‐pulse rate was negatively related to the distance between two consecutive crests. For T. pyrenaeus, with the largest number of populations sampled, there was no significant correlation between morphological and spectrographic distances, but there were significant positive correlations between morphological and geographical distances and between morphological and genetic distances. It is hypothesized that genetic differentiation might directly affect variability of the stridulatory apparata which would also be indirectly influenced and constrained by external morphological traits (like the width of the coxa and body size). Stridulatory organs, in turn, would affect the ways a few stridulatory traits (especially the temporal ones) change in time and space.
A new hypothesis for species coexistence: male–male repulsion promotes coexistence of competing species
Authors: Mikami Osamu K. , Kohda Masanori , Kawata Masakado
Published: June 2004

We propose a new hypothesis for species coexistence by considering behavioral interactions between individuals. The hypothesis states that repulsive behavior between conspecific males (male–male repulsion) creates space for competing species, which promotes their coexistence. This hypothesis can explain the coexistence of two competing species even when their ecological niches completely overlap in spatially homogeneous environments. In addition, the mechanisms underlying such behavior might play a role in enabling the coexistence of two species immediately after speciation, with little or no niche differentiation, as in the case of cichlid fish communities, for example. Although there is limited evidence supporting this hypothesis, it can nevertheless explain the occurrence of species coexistence and biodiversity, which cannot be explained by previous theories.