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  • 2010-2014  (24)
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  • Industrial Chemistry and Chemical Engineering  (746)
  • ddc:510
  • 1
    Publikationsdatum: 2020-12-11
    Beschreibung: Convexity is an important property in nonlinear optimization since it allows to apply efficient local methods for finding global solutions. We propose to apply symbolic methods to prove or disprove convexity of rational functions over a polyhedral domain. Our algorithms reduce convexity questions to real quantifier elimination problems. Our methods are implemented and publicly available in the open source computer algebra system REDUCE. Our long term goal is to integrate REDUCE as a workhorse'' for symbolic computations into a numerical solver.
    Schlagwort(e): ddc:510
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 2
    Publikationsdatum: 2016-06-30
    Beschreibung: Applications which need exclusive access to a shared resource in distributed systems require a fault-tolerant and scalable mechanism to coordinate this exclusive access. Examples of such applications include distributed file systems and master/slave data replication. We present Flease, an algorithm for decentralized and fault-tolerant lease coordination in distributed systems. Our algorithm allows the processes competing for a resource to coordinate exclusive access through leases among themselves without a central component. The resulting system easily scales with an increasing number of nodes and resources. We prove that Flease ensures exclusive access, i.e. guarantees that there is at most one valid lease at any time.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 3
    Publikationsdatum: 2020-08-05
    Beschreibung: We propose an efficient column generation method to minimize the probability of delay propagations along aircraft rotations. In this way, delay resistant schedules can be constructed. Computational results for large-scale real-world problems demonstrate substantial punctuality improvements. The method can be generalized to crew and integrated scheduling problems.
    Schlagwort(e): ddc:510
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 4
    Publikationsdatum: 2022-01-07
    Beschreibung: In optimal control problems with nonlinear time-dependent 3D PDEs, full 4D discretizations are usually prohibitive due to the storage requirement. For this reason gradient and quasi-Newton methods working on the reduced functional are often employed. The computation of the reduced gradient requires one solve of the state equation forward in time, and one backward solve of the adjoint equation. The state enters into the adjoint equation, again requiring the storage of a full 4D data set. We propose a lossy compression algorithm using an inexact but cheap predictor for the state data, with additional entropy coding of prediction errors. As the data is used inside a discretized, iterative algorithm, lossy coding maintaining an error bound is sufficient.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 5
    Publikationsdatum: 2020-03-11
    Beschreibung: Bovine fertility is the subject of extensive research in animal sciences, especially because fertility of dairy cows has declined during the last decades. The regulation of estrus is controlled by the complex interplay of various organs and hormones. Mathematical modeling of the bovine estrous cycle could help in understanding the dynamics of this complex biological system. In this paper we present a mathematical model of the bovine estrous cycle that includes the processes of follicle and corpus luteum development and the key hormones that interact to control these processes. Focus in this paper is on development of the model, but also some simulation results are presented, showing that a set of equations and parameters is obtained that describes the system consistent with empirical knowledge. Even though the majority of the mechanisms that are included are only known qualitatively as stimulatory or inhibitory effects, the model surprisingly well features quantitative observations made in reality. This model of the bovine estrous cycle could be used as a basis for more elaborate models with the ability to study effects of external manipulations and genetic differences.
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    Sprache: Englisch
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  • 6
    Publikationsdatum: 2022-03-14
    Beschreibung: Learning during search allows solvers for discrete optimization problems to remember parts of the search that they have already performed and avoid revisiting redundant parts. Learning approaches pioneered by the SAT and CP communities have been successfully incorporated into the SCIP constraint integer programming platform. In this paper we show that performing a heuristic constraint programming search during root node processing of a binary program can rapidly learn useful nogoods, bound changes, primal solutions, and branching statistics that improve the remaining IP search.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 7
    Publikationsdatum: 2020-08-05
    Beschreibung: We propose a novel integer programming approach to transfer minimization for line planning problems in public transit. The idea is to incorporate penalties for transfers that are induced by “connection capacities” into the construction of the passenger paths. We show that such penalties can be dealt with by a combination of shortest and constrained shortest path algorithms such that the pricing problem for passenger paths can be solved efficiently. Connection capacity penalties (under)estimate the true transfer times. This error is, however, not a problem in practice. We show in a computational comparison with two standard models on a real-world scenario that our approach can be used to minimize passenger travel and transfer times for large-scale line planning problems with accurate results.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 8
    Publikationsdatum: 2016-06-09
    Beschreibung: The aim of this paper is to devise an adaptive timestep control in the contact--stabilized Newmark method (CONTACX) for dynamical contact problems between two viscoelastic bodies in the framework of Signorini's condition. In order to construct a comparative scheme of higher order accuracy, we extend extrapolation techniques. This approach demands a subtle theoretical investigation of an asymptotic error expansion of the contact--stabilized Newmark scheme. On the basis of theoretical insight and numerical observations, we suggest an error estimator and a timestep selection which also cover the presence of contact. Finally, we give a numerical example.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 9
    Publikationsdatum: 2020-08-05
    Beschreibung: Railway scheduling is based on the principle of the construction of a conflict-free timetable. This leads to a strict definition of capacity: in contrast with road transportation, it can be said in advance whether a given railway infrastructure can accommodate - at least in theory - a certain set of train requests. Consequently, auctions for railway capacity are modeled as auctions of discrete goods -- the train slots. We present estimates for the efficiency gain that may be generated by slot auctioning in comparison with list price allocation. We introduce a new class of allocation and auction problems, the feasible assignment problem, that is a proper generalization of the well-known combinatorial auction problem. The feasible assignment class was designed to cover the needs for an auction mechanism for railway slot auctions, but is of interest in its own right. As a practical instance to state and solve the railway slot allocation problem, we present an integer programming formulation, briefly the ACP, which turns out to be an instance of the feasible assignment problem and whose dual problem yields prices that can be applied to define a useful activity rule for the linearized version of the Ausubel Milgrom Proxy auction. We perform a simulation aiming to measure the impact on efficiency and convergence rate.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 10
    Publikationsdatum: 2022-01-07
    Beschreibung: This paper presents concepts and implementation of the finite element toolbox Kaskade 7, a flexible C++ code for solving elliptic and parabolic PDE systems. Issues such as problem formulation, assembly and adaptivity are discussed at the example of optimal control problems. Trajectory compression for parabolic optimization problems is considered as a case study.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 11
    Publikationsdatum: 2020-08-05
    Beschreibung: In this paper a bottom-up approach of automatic simplification of a railway network is presented. Starting from a very detailed, microscopic level, as it is used in railway simulation, the network is transformed by an algorithm to a less detailed level (macroscopic network), that is sufficient for long-term planning and optimization. In addition running and headway times are rounded to a pre-chosen time discretization by a special cumulative method, which we will present and analyse in this paper. After the transformation we fill the network with given train requests to compute an optimal slot allocation. Then the optimized schedule is re-transformed into the microscopic level and can be simulated without any conflicts occuring between the slots. The algorithm is used to transform the network of the very dense Simplon corridor between Swiss and Italy. With our aggregation it is possible for the first time to generate a profit maximal and conflict free timetable for the corridor across a day by a simultaneously optimization run.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 12
    facet.materialart.
    Unbekannt
    Publikationsdatum: 2020-12-11
    Beschreibung: In solving large polynomial algebraic systems that are too big for standard Gröbner basis techniques one way to make progress is to introduce case distinctions. This divide and conquer technique can be beneficial if the algorithms and computer programs know how to take advantage of inequalities. A further hurdle is the form of the resulting general solutions which often have unnecessarily many branches. In this paper we discuss a procedure to merge solutions by dropping inequalities which are associated with them and, if necessary, by re-parametrizing solutions. In the appendix the usefulness of the procedure is demonstrated in the classification of quadratic Hamiltonians with a Lie-Poisson bracket $e(3)$. This application required the solution of algebraic systems with over 200 unknowns, 450 equations and between 5000 and 9000 terms.
    Schlagwort(e): ddc:510
    Sprache: Englisch
    Materialart: reportzib , doc-type:preprint
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  • 13
    facet.materialart.
    Unbekannt
    Publikationsdatum: 2020-12-11
    Beschreibung: In the paper arguments are given why the concept of static evaluation (SE) has the potential to be a useful extension to Monte Carlo tree search. A new concept of modeling SE through a dynamical system is introduced and strengths and weaknesses are discussed. The general suitability of this approach is demonstrated. A Remark: Among users of the Internet Go server KGS the abbreviation SE is used for 'Score Estimator'. Although different from 'Static Evaluation' a score estimator is easily obtained from static evaluation by adding up probabilities of chains to be alive at the end of the game or points to be owned by White or Black
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    Sprache: Englisch
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  • 14
    Publikationsdatum: 2020-12-11
    Beschreibung: Linear Poisson brackets on e(3) typical of rigid body dynamics are considered. All quadratic Hamiltonians of Kowalevski type having additional first integral of fourth degree are found. Quantum analogs of these Hamiltonians are listed.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 15
    Publikationsdatum: 2020-12-11
    Beschreibung: A classification problem is proposed for supersymmetric %scaling\/-\/in\-va\-ri\-ant evolutionary PDE that satisfy the assumptions of nonlinearity, nondegeneracy, and homogeneity. Four classes of nonlinear coupled boson\/-\/fermion systems are discovered under the weighting assumption $|f|=|b|=|D_t|=\oh$. The syntax of the \Reduce\ package \SsTools, which was used for intermediate computations, and the applicability of its procedures to the calculus of super\/-\/PDE are described.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 16
    Publikationsdatum: 2020-12-11
    Beschreibung: We consider the problem of constructing Gardner's deformations for the $N{=}2$ supersymmetric $a{=}4$--\/Korteweg\/--\/de Vries equation; such deformations yield recurrence relations between the super\/-\/Hamiltonians of the hierarchy. We prove the non\/-\/existence %P.~Mathieu's Open problem on constructing for of supersymmetry\/-\/invariant %Gardner's deformations that %solutions, retract to Gardner's formulas for the KdV equation %whenever it is assumed that, under the %respective component reduction. % in the $N{=}2$ super\/-\/field. the solutions . At the same time, we propose a two\/-\/step scheme for the recursive production of the integrals of motion for the $N{=}2$,\ $a{=}4$--\/SKdV. First, we find a new Gardner's deformation of the Kaup\/--\/Boussinesq equation, which is contained in the bosonic limit of the super\/-\/%$N{=}2$,\ $a{=}4$--\/SKdV hierarchy. This yields the recurrence relation between the Hamiltonians of the limit, whence we determine the bosonic super\/- /Hamiltonians of the full $N{=}2$, $a{=}4$--\/SKdV hierarchy.
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    Sprache: Englisch
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  • 17
    Publikationsdatum: 2020-08-05
    Beschreibung: We provide an introduction into the mathematics of and with paths. Not on the shortest, but hopefully on an entertaining path!
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 18
    Publikationsdatum: 2020-08-05
    Beschreibung: Wir stellen in dieser Arbeit ein mathematisches Optimierungsmodell zur Bestimmung eines optimalen Linienplans vor, das sowohl die Fahrzeiten und die Anzahl der Umstiege berücksichtigt als auch die Kosten des Liniennetzes. Dieses Modell deckt wichtige praktische Anforderungen ab, die in einem gemeinsamen Projekt mit den Verkehrsbetrieben in Potsdam (ViP) formuliert wurden. In diesem Projekt wurde der Linienplan 2010 für Potsdam entwickelt. Unsere Berechnungen zeigen, dass die mathematische Optimierung in nichts einer "Handplanung" des Liniennetzes nachsteht. Im Gegenteil, mit Hilfe des Optimierungsprogramms ist es möglich, durch Veränderung der Parameter mehrere verschiedene Szenarien zu berechnen, miteinander zu vergleichen und Aussagen über minimale Kosten und Fahrzeiten zu machen.
    Schlagwort(e): ddc:510
    Sprache: Deutsch
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  • 19
    facet.materialart.
    Unbekannt
    Publikationsdatum: 2020-12-11
    Beschreibung: The paper gathers evidence showing different dimensions of the game of Go: the continuous and discrete nature of the game and different types of relations between state variables happening on ultra local, local, regional, and global scales. Based on these observations a new continuous local model for describing a board position is introduced. This includes the identification of the basic variables describing a board position and the formulation and solution of a dynamical system for their computation. To be usable as a static evaluation function for a game playing program at least group-wide (regional)aspects will have to be incorporated.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 20
    Publikationsdatum: 2020-08-05
    Beschreibung: The track allocation problem, also known as train routing problem or train timetabling problem, is to find a conflict-free set of train routes of maximum value in a railway network. Although it can be modeled as a standard path packing problem, instances of sizes relevant for real-world railway applications could not be solved up to now. We propose a rapid branching column generation approach that integrates the solution of the LP relaxation of a path coupling formulation of the problem with a special rounding heuristic. The approach is based on and exploits special properties of the bundle method for the approximate solution of convex piecewise linear functions. Computational results for difficult instances of the benchmark library TTPLIB are reported.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 21
    Publikationsdatum: 2020-08-05
    Beschreibung: This paper presents a case study on a railway timetable optimization for the very dense Simplon corridor, a major railway connection in the Alps between Switzerland and Italy. Starting from a detailed microscopic network as it is used in railway simulation, the data is transformed by an automatic procedure to a less detailed macroscopic network, that is sufficient for the purpose of capacity planning and amenable to state-of-the-art integer programming optimization methods. In this way, the macroscopic railway network is saturated with trains. Finally, the corresponding timetable is re-transformed to the microscopic level in such a way that it can be operated without any conflicts among the slots. Using this integer programming based micro-macro aggregation-disaggregation approach, it becomes for the first time possible to generate a profit maximal and conflict free timetable for the complete Simplon corridor over an entire day by a simultaneous optimization of all trains requests. This also allows to to undertake a sensitivity analysis of various problem parameters.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 22
    Publikationsdatum: 2016-06-09
    Beschreibung: The thesis presents the analysis of a reduced model for modulation of internal gravity waves by deep convective clouds. The starting point for the derivation are conservation laws for mass, momentum and energy coupled with a bulk micro-physics model describing the evolution of mixing ratios of water vapor, cloud water and rain water. A reduced model for the identified scales of the regime is derived, using multi-scale asymptotics. The closure of the model employs conditional averaging over the horizontal scale of the convective clouds. The resulting reduced model is an extension of the anelastic equations, linearized around a constant background state, which are well-known from meteorology. The closure of the model is achieved purely by analytical means and involves no additional physically motivated assumptions. The essential new parameter arising from the coupling to a micro-physics model is the area fraction of saturated regions on the horizontal scale of the convective clouds. It turns out that this parameter is constant on the employed short timescale. Hence the clouds constitute a constant background, modulating the characteristics of propagation of internal waves. The model is then investigated by analytical as well as numerical means. Important results are, among others, that in the model moisture (i) inhibits propagation of internal waves by reducing the modulus of the group velocity, (ii) reduces the angle between the propagation direction of a wave-packet and the horizontal, (iii) causes critical layers and (iv) introduces a maximum horizontal wavelength beyond which waves are no longer propagating but become evanescent. The investigated examples of orographically generated gravity waves also feature a significant reduction of vertical momentum flux by moisture. The model is extended by assuming systematically small under-saturation, that is saturation at leading order. The closure is similar to the original case but requires additional assumptions. The saturated area fraction in the obtained model is no longer constant but now depends nonlinearly on vertical displacement and thus on vertical velocity.
    Schlagwort(e): ddc:510
    Sprache: Englisch
    Materialart: doctoralthesis , doc-type:doctoralThesis
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  • 23
    Publikationsdatum: 2022-03-14
    Beschreibung: We propose a hybrid approach for solving the resource-constrained project scheduling problem which is an extremely hard to solve combinatorial optimization problem of practical relevance. Jobs have to be scheduled on (renewable) resources subject to precedence constraints such that the resource capacities are never exceeded and the latest completion time of all jobs is minimized. The problem has challenged researchers from different communities, such as integer programming (IP), constraint programming (CP), and satisfiability testing (SAT). Still, there are instances with 60 jobs which have not been solved for many years. The currently best known approach, lazyFD, is a hybrid between CP and SAT techniques. In this paper we propose an even stronger hybridization by integrating all the three areas, IP, CP, and SAT, into a single branch-and-bound scheme. We show that lower bounds from the linear relaxation of the IP formulation and conflict analysis are key ingredients for pruning the search tree. First computational experiments show very promising results. For five instances of the well-known PSPLIB we report an improvement of lower bounds. Our implementation is generic, thus it can be potentially applied to similar problems as well.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 24
    Publikationsdatum: 2023-11-03
    Beschreibung: In contrast to the well known meshbased methods like the finite element method, meshfree methods do not rely on a mesh. However besides their great applicability, meshfree methods are rather time consuming. Thus, it seems favorable to combine both methods, by using meshfree methods only in a small part of the domain, where a mesh is disadvantageous, and a meshbased method for the rest of the domain. We motivate, that this coupling between the two simulation techniques can be considered as saddle point problem and show the stability of this coupling. Thereby a novel transfer operator is introduced, which interacts in the transition zone, where both methods coexist.
    Schlagwort(e): ddc:510
    Sprache: Englisch
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  • 25
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 409-417 
    ISSN: 0268-2605
    Schlagwort(e): antitumor activity ; cancer cell lines ; dibutyltins ; NCI ; organotins ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This paper reports the activity of four dibutyltin(IV)-N-arylidene-α-amino acid complexes against the National Cancer Institute (NCI) panel of 60 cell lines. The results indicated that three of the organotin complexes (C17H25NO3Sn, C18H27NO3Sn and C20H31NO3Sn) exhibit their highest cytotoxic effect on the NCI-522 (non-small cell lung cancer) cell line. The fourth complex, C21H27NO3Sn, exhibits its highest cytotoxic activity on the cell line RXF-631L (renal cancer). In general, a low to moderate cellular response was observed for all the organotin complexes, with at least one cell line in each subpanel of cells exhibiting a very low growth inhibition response to all the organotin complexes. The low-responding cell lines included HOP-62 (non-small lung cancer), DLD-1 (colon cancer), SF-539 (CNS cancer), SK-MEL-5 (melanoma), IGROV-1 (ovarian cancer) and RPMI-8226 (leukemia). The results also indicated that the compounds did not exhibit any significant subpanel activity and suggested that the compounds were not active in all the cell lines contained in any subpanel. The low to moderate activity of these compounds across the cell lines was attributed to the presence of nitrogen-bearing ligands which prevented the dissociation of the compound and the subsequent binding to DNA. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 449-455 
    ISSN: 0268-2605
    Schlagwort(e): trimethylantimony ; biomethylation ; anaerobic bacteria ; inorganic antimony ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The volatile antimony compound trimethylantimony (TMA) was detected in headspace gases over anaerobic soil enrichment cultures spiked with potassium antimony tartrate. The presence of TMA was variable (12 positives from 104 cultures) and dependent upon both the inoculum source (environmental sample) and enrichment culture conditions. Positives for TMA formation were obtained with variable frequency for four of the six soils tested and for three types of enrichment culture, designed to encourage growth of nitrate-reducing, methane-producing or fermentative bacteria. The identity of the volatile antimony compound produced in each of the three types of enrichment culture was confirmed by gas chromatography-mass spectrometry and gas chromatography-atomic absorption spectroscopy. There was no evidence of any other volatile antimony compound in the headspace gases. These data suggest that the capability to generate TMA is widely distributed in the terrestrial environment and is attributable to different metabolic types of micro-organisms. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 467-467 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 28
    ISSN: 0268-2605
    Schlagwort(e): fungicidal activity ; Ceratocystis ulmi ; triphenyltin(IV) ; tributyltin(IV) ; phenolic bridge ; carboxylate bridge ; polymers ; trigonal bipyramidal structures ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The methods of synthesis, elemental analysis, IR and NMR spectroscopic data and fungicidal activity against Ceratocystis ulmi are reported for a series of triorganotin esters of N-arylidene-ω-amino acids of general formula R3SnOCO(CH2)nN = CHAr (R = Ph, n-Bu; Ar = 2-HOC6H4, 2-HOC10H6; n = 1, 2, 3 and 5). The crystal structures for two of the compounds, tributyltin N-2-hydroxynaphthalidene glycinate (1) and tributyltin N-2-hydroxynaphthalidene-β-alaninate (2), have been determined. Although both of these compounds have a trans-R3SnO2 structure, in compound 1 the carboxylate group is monodentate and the fifth coordination position around the tin atom is taken up by a coordinated phenolic group, whereas in 2 the carboxylate group is bridging. These two examples thus correspond to the two different structures reported for trans-R3SnO2 complexes. Both compounds were found to be active against Ceratocystis ulmi, but there was no significant difference in their levels of biological activity against this particular fungus. Apart from compound 1, the other tributyltin compounds reported are believed to adopt the carboxylate bridging mode shown by compound (2).Crystal data: for 1, crystals monoclinic, space group P21/c, a = 12.9435(11) Å, b = 13.5769(10) Å, c = 15.7715(12) Å, β = 108.919(6)°, Z = 4, Rf = 0.046 and Rw = 0.058 for 1448 significant reflections; for 2, crystals monoclinic, space group C 2/c,a = 24.588(14) Å, b = 9.733(3) Å, c = 27.611(12) Å,β = 113.49(4)°, Z = 8, Rf = 0.053 and Rw = 0.069 for 3822 significant reflections. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
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  • 29
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 878-878 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 30
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 801-807 
    ISSN: 0268-2605
    Schlagwort(e): metal-containing vinylic monomers ; vinylbenzoyl complexes ; cinnamoyl complexes ; tungsten-olefin monomers ; iron-olefin monomers ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of metal-containing vinylic monomers of the type LnM(COC6H4CH=CH2) and LnM (COCH=CHC6H5) [LnM = (η5-C5H5)Fe(CO)2, (η5-C5Me5)Fe(CO)2 and (η5-C5H5)W(CO)3] were prepared by the reaction of the appropriate metal anion with either 4-vinylbenzoyl chloride or cinnamoyl chloride. (η5-C5H5)(CO)2FeCOCH=CH2 was prepared by the reaction of Na[(η5-C5H5)Fe(CO)2] and acryloyl chloride, whereas the compound (η5-C5H5)(CO)2Fe(C6H4CH=CH2) was prepared via a transmetallation reaction using a palladium catalyst. All compounds were fully characterized using FTIR, 1H and 13C NMR spectroscopy and mass spectrometry. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Tab.
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  • 31
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 879-879 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 32
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 793-799 
    ISSN: 0268-2605
    Schlagwort(e): anticancer ; antineoplastic ; ferrocene/ferricenium ; biological redox ; free radical ; polyaspartamide ; tumor ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The ferrocene/ferricenium redox system plays a significant role in biological oxidation, reduction and free-radical reactions. Of particular interest are the findings of earlier investigations which showed certain water-soluble ferricenium salts to possess appreciable antiproliferative activity against various murine tumor lines and a xenografted human colorectal adenocarcinoma. Solubility in water, a prerequisite for efficacious transport and dissipation in central circulation, was then proposed as a principal requirement for the ferrocene complex system to exert antineoplastic activity irrespective of the oxidation state in which it is administered. In order to shed more light on this question, we decided to investigate the antiproliferative properties of polymer-ferrocene conjugates containing the metal complex in the non-oxidized (ferrocene) form while fulfilling the critical requirement of water solubility. To this end, five selected, water-soluble conjugates, synthesized by reversible coupling of 4-ferrocenylbutanoic acid to variously structured polyaspartamides featuring pendant primary amino groups as coupling sites, were tested in vitro against cultured HeLa cells at concentrations up to 50 µg Fe ml-1. Optimal antiproliferative activities, with IC50 in the range of 2-7 µg Fe ml-1, were determined for three compounds possessing tertiary-amine functions susceptible to protonation at physiological pH. Lower activities (IC50 = 45-60 µg Fe ml-1) were demonstrated for two poly(ethylene oxide)-containing conjugates. However, no reasonable structure-performance relationships can be derived at this stage from the small number of compounds tested. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
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  • 33
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 879-880 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 34
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 880-880 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 35
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 855-859 
    ISSN: 0268-2605
    Schlagwort(e): butyltin ; phenyltin ; gibberellates ; antitumour ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis and characterization of di-n-butyl-, tri-n-butyl- and triphenyltin gibberellates are reported. Their antitumour activities in vitro against a panel of seven human tumour cell lines are given and compared with those of drugs used clinically. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 36
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 873-876 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 37
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 531-539 
    ISSN: 0268-2605
    Schlagwort(e): methylmercury ; estuarine sediment ; certification ; (BCR) ; quality control ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Legislation on methylmercury within the European Union (EU), e.g. in food (national regulations) or water (EC Directives), requires that the determinations are of proven quality; thus implies that they should be carried out under strict quality control (QC). One method of achieving good quality control in chemical analysis is to verify the analytical performance of methods by analysing Certified Reference Materials (CRMs). While CRMs of biological matrices (e.g. fish, mussels) are already available, there was a lack of materials for the QC of sediment analysis. This paper describes the preparation of an estuarine sediment reference material, the homogeneity and stability studies and the analytical work performed for the certification of the contents of total mercury and methylmercury. The results of a group of expert laboratories are discussed and the methods used to certify the mass fractions of total mercury (132 ± 3 mg kg-1 on a dry mass basis) and methylmercury (75.5 ± 3.7 μg kg-1 as CH3Hg+ on a dry mass basis) are described. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 571-576 
    ISSN: 0268-2605
    Schlagwort(e): zerovalent metals ; bromoalkyltriphenylphosphonium bromides ; methylmercuric acetate ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Aqueous solutions of bromoalkyltriphenylphosphonium bromides react with zerovalent metals, causing their dissolution. The reaction initially follows second-order kinetics, with the rate depending on both metal and bromide concentrations. Zerovalent metals similarly react with aqueous methylmercuric acetate and other dissolved organometals. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 643-650 
    ISSN: 0268-2605
    Schlagwort(e): tributyltin ; sediment ; degradation ; coastal British Columbia ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Butyltin concentrations in the sediments of two coastal areas of British Columbia, Canada, are reported. Two recent box cores from the deepest basin in the Strait of Georgia were sectioned and analyzed by GC-atomic emission spectrometry. No butyltin compounds were detected above 0.5 μgSn kg-1 (dry weight) in either core. These results are compared to those for a previous (1991) core from the same area. In that study, tributyltin (TBT) concentrations were in the range 1-2 μgSn kg-1 down the core and were higher than those of either of the degradation products, dibutyltin (DBT) and monobutyltin (MBT). Radioisotope dating (210Po-210Pb counting methods) was used to establish the rates of sedimentation of 0.25 and 2.6 cm y-1 at the two sites. Data suggest that a combination of rapid deposition of new, less-contaminated material and degradation of previously deposited butyltin compounds has resulted in the observed absence. Thirty-three surface sediments from the northern BC coastal harbor at Prince Rupert, collected in 1995, were analyzed for butyltin residues by GC-FPD. Concentrations of TBT, DBT and MBT were in the ranges from below the appropriate limit of detection (LOD) to 1262, to 109 and to 37 μgSn kg-1, respectively. TBT/DBT ratios ranged from 0.2 to 62 with most above unity, indicating that there is continuing fresh input of TBT. The sources are almost exclusively large ocean-going vessels that use the harbor for long-term anchorage. These findings are discussed with reference to the global TBT status. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 577-584 
    ISSN: 0268-2605
    Schlagwort(e): organotin ; extraction ; analysis ; GC-FPD ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effects of: (1) the modifier type (methanol and formic, acetic and propionic acids), (2) complexing agents (diethylammonium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate) either with or without acidic modifiers, (3) the extraction temperature (50-80 °C) and pressure (30-50 MPa), (4) the extraction procedure (static-dynamic or dynamic), and (5) the volume of static modifier, on the extraction efficiency of native butyl- and phenyl-tin compounds from sediment, were evaluated comprehensively. The highest extraction efficiency for butyl- and phenyl-tin compounds was obtained at 30 MPa and 50 °C by using CO2 modified with acetic acid (200 μl in the cell). Supercritical fluid extraction (SFE) extracts were hexylated and determined by GC-FPD using a 610 nm bandpass filter without any clean-up step. In summary, the developed analytical procedure is robust (no restrictor clogging; free from FPD interferences), it is low-cost (no complexing agents needed), it has a high sample throughput (〈3 h), it is independent of the matrix for the determination of butyltin compounds in sediment, and it provides the highest precision among the SFE procedures reported for organotin determination. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 585-590 
    ISSN: 0268-2605
    Schlagwort(e): butyltin ; estuarine microcosm ; environmental fate ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A radiotracer experiment was conducted in a controlled experimental ecosystem (microcosm) to determine the persistence and behavior of tributyltin (TBT) under conditions simulating a temperate, shallow estuarine ecosystem. Radiolabeled TBT was introduced to the estuarine microcosm, which contained estuarine water, sediment and fish. TBT and its degradation products were monitored for 40 days. TBT rapidly distributed among the compartments of the microcosm. The TBT half-life in the water column was 2.55 days for the first 11 days and then slowed to 13.4 days. More than 60% of the TBT and its metabolites were found in the sediment, indicating that the sediment was an important sink for butyltins. Higher concentrations of butyltins, relative to the water column concentrations, were found in the surface microlayer. TBT could be bioconcentrated by the fish to levels more than 200 times the exposure concentration, and underwent rapid degradation in the fish body, so that high concentrations of its metabolites were found in the fish. The concentrations of TBT adsorbed on the suspended particles were three orders of magnitude greater than that in dissolved form. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 591-599 
    ISSN: 0268-2605
    Schlagwort(e): arsenic speciation ; LC-ICP-MS ; validation ; urine samples ; background levels ; The Netherlands ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The method validation for the speciation of five arsenic species in urine samples by liquid chromatography hyphenated to inductively coupled plasma mass spectrometry is described. Arsenic species which are identified and quantified in urine samples are the anions of arsenic(III), arsenic(V), monomethylarsonic acid and dimethylarsinic acid, and the cationic arsenobetaine. Detection limits were obtained in the range 0.3-0.4 μg As l-1 while the repeatability was in the range 3-4% (RSD) for concentrations above five times the detection limit. Urine samples could be analysed directly after a ten-fold dilution step. Arsenic compound concentrations were determined in urine samples from a volunteer who consumed a portion of tuna fish high in arsenobetaine. It was found that arsenobetaine was excreted rapidly via the urine with maximum concentrations after 12 h. Nearly complete arsenobetaine excretion was reached after 48 h. Background levels of arsenic compounds were determined in 61 urine samples from non-exposed inhabitants of The Netherlands. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 763-770 
    ISSN: 0268-2605
    Schlagwort(e): siloxane network ; contact angle ; sol-gel reaction ; polydimethylsiloxane ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polydimethylsiloxane (PDMS) hybrid networks have been prepared by the reaction of PDMS(OH)2, average molecular weight 26 × 103, 43.6 × 103 and 58 × 103, and methyltriethoxysilane (MeTEOS, 10-60 wt%) using a dibutyltin dilaurate or dibutyltin diacetate catalyst. By hydrolysis and homo- and co-condensation, MeTEOS forms a siliceous domain (MeSD) and acts as a crosslinker for the PDMS domain. Kinetic studies showed that high MeTEOS and catalyst concentrations and reduction of free surface area favor fast gelation and efficiency in converting MeTEOS to the MeSD. Under the water-sparse conditions utilized, cure was slow and substantial evaporative loss of MeTEOS occurred. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 375-379 
    ISSN: 0268-2605
    Schlagwort(e): granular films ; pulsed laser deposition ; giant magnetoresistance ; microstructure ; magnetic properties ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An investigation into the microstructural properties of CoxAg1 - x films, grown by pulsed laser deposition, as a function of deposition and post-deposition annealing temperature is reported. Surface morphology and microstructure were investigated by XPS, SEM and TEM measurements. Magnetic measurements were used to gain further information on particle size distributions through the analysis of the temperature dependence of the irreversible magnetization. Depending on cobalt content, deposition and post-deposition annealing temperature, the maximum of the cobalt grains diameter distribution was estimated to be in the range 2-6 nm. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
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  • 45
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 381-386 
    ISSN: 0268-2605
    Schlagwort(e): nanoparticles ; magnetic susceptibility ; magnetic anisotropy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The dynamical behavior of γ-Fe2O3 particles dispersed in a polymer have been investigated by a.c. susceptibility and Mössbauer spectroscopy measurements. The effect of interparticle interactions on the relaxation time is satisfactorily described by a superparamagnetic model where the dipolar energy is determined by a statistical calculation for a disordered arrangement of particles with volume distribution and easy axes in random orientations. The results indicate that the single particle anisotropy energy is mainly determined by surface anisotropy and that the energy barrier increases with the interaction strength. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 881-881 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 47
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 881-882 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 48
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 883-884 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 49
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 827-842 
    ISSN: 0268-2605
    Schlagwort(e): Scopulariopsis brevicaulis ; hydride generation ; antimony ; biomethylation ; biotransformation ; solid-phase extraction ; sudden infant death syndrome (SIDS) ; volatile antimony ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cultures of the fungus Scopulariopsis brevicaulis were grown in antimony-rich media. Although volatile compounds of other elements were readily detected in the culture headspace, volatile antimony compounds were formed irreproducibly and at only ultratrace levels. In order to monitor the media for nonvolatile methylantimony compounds, a method of sample preparation was developed, based on solid-phase extraction. This enabled the separation of large quantities of soluble inorganic antimony species from trace amounts of organoantimony compounds before speciation by HG-GC-AAS. By this methodology methylated antimony compounds were detected at concentrations of 0.8- 7.1 µg Sbl-1 in all media in which S. brevicaulis was grown in the presence of antimony(III) compounds. These methylantimony species were not detected in any of the nonliving or medium-only controls. Methylated compounds were not detected where S. brevicaulis was grown in the presence of antimony(V) compounds. This is the first study to show that antimony(III) compounds are biomethylated by S. brevicaulis under aerobic-only growth conditions. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 50
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 51
    ISSN: 0268-2605
    Schlagwort(e): carbohydrate-modified phenylsiloxane ; surfactants ; wetting behaviour ; superspreading ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The dynamic wetting behaviour on a perfluorinated, low-energy solid has been investigated for a carbohydrate-modified phenylsiloxane surfactant. The surfactant concentration, the rate of interface generation and the [solid/liquid interface area] : [liquid/vapour interface area] ratio were varied systematically. Dynamic data for the liquid/vapour (γlv) and solid/liquid (γsl) interfacial tension as well as their Lifshitz-van der Waals and donor-acceptor contributions were determined under strictly controlled conditions. Since γsl reacts sensitively to variations of the surfactant concentration and the rate of interface generation, the covering of the liquid/non-polar solid interface is assumed to be a spreading limiting factor. The corresponding γlv values remain constant and close to those obtained under equilibrium conditions. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 11 Ill.
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  • 52
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 523-529 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 53
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 559-563 
    ISSN: 0268-2605
    Schlagwort(e): tributyltin ; surface microlayer ; dynamic model ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The transport dynamics of tributyltin (TBT) between the surface microlayer and subsurface water were studied in experimental systems which simulated different surface sea states. A dynamic model was derived from a diffusion equation to describe the dynamics of the TBT transport process. With this dynamic model diffusion coefficients were determined, and the effects of surface sea states and temperature on the TBT transport process between the surface microlayer and subsurface water were also studied. Turbulence, breaking waves and elevated temperature can accelerate this transport. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 1 Ill.
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  • 54
    ISSN: 0268-2605
    Schlagwort(e): methylmercury ; analysis ; HPLC- ICP MS ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A novel technique has been developed for the determination of trace amounts of methylmercury in various sample matrices. The newly developed HPLC method makes it possible to separate methylmercury and inorganic mercury with ultrasonic nebulization and detection by ICP MS for different mercury isotopic masses. The isotope-specific detection allows the application of the species-specific isotope addition method for the determination of methylmercury with a correction for artifact formation. The well-known water-vapour distillation method was used in combination with an enriched stable inorganic mercury isotope (200Hg2+) for the separation of methylmercury from various matrices. The subsequent determination of CH3 - 200Hg+ generated from 200Hg2+ was used in the correction for artifact formation during sample preparation. In comparison with a previously developed HPLC coupling technique with HPF-HHPN (high-performance flow/­hydraulic high-pressure nebulization), the stability of the detection procedure was improved considerably. The limit of detection (S/N = 3) for methylmercury was calculated to be about 0.015 μg kg-1. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 55
    ISSN: 0268-2605
    Schlagwort(e): methylmercury ; solid-phase microextraction ; gas chromatography-atomic fluorescence ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An analytical method is described for methylmercury determination in fish and aqueous samples using solid-phase microextraction (SPME) followed by gas chromatography-atomic fluorescence spectrometry (GC-AFS). The procedure involves aqueous-phase derivatization of methylmercury species with sodium tetraethylborate in a sample vial and subsequent extraction with a silica fiber coated with poly-­(dimethylsiloxane). The mercury derivatives are desorbed in the splitless injection port of a gas chromatograph and subsequently analyzed by GC-AFS. The headspace SPME procedure is used and parameters affecting the extraction, adsorption and desorption are evaluated. Results for methylmercury analysis in standard reference material (DORM-2) and fish samples are presented. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
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  • 56
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 635-641 
    ISSN: 0268-2605
    Schlagwort(e): arsenobetaine ; arsenocholine ; non-hygroscopic ; NMR ; FAB MS ; ICP MS ; synthesis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Multigram quantities of arsenobetaine bromide and arsenocholine iodide were synthesized from trimethylarsine using uncomplicated techniques. Arsenobetaine bromide and arsenocholine iodide are both non-hygroscopic. Arsenocholine iodide is, however, light-sensitive and should be used with actinic glassware. Both compounds were characterized by elemental and spectroscopic techniques and found to be suitable for use as primary analytical standards. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
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  • 57
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 659-666 
    ISSN: 0268-2605
    Schlagwort(e): polymers ; polyphosphazenes ; synthesis ; surfaces ; surface reactions ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The macromolecular substitution approach for the synthesis of polyphosphazenes provides access to many different polymers. However, it precludes the use of reagents that contain two or more functional groups because such compounds would cause extensive crosslinking of the chains. This presents a problem because many of the uses for which polyphosphazenes seem ideally suited require the presence of -OH, -COOH, -NH2, -SO3H, -PR2 and other functional units in the side-chain structure. We have developed two approaches to introduce such active sites: (1) protection-deprotection reactions; and (2) direct reactions of active reagents with the organic side-groups of non-functional poly(organophosphazenes). These methods have been applied both at the molecular level and in the form of reactions carried out only at polymer surfaces. The resultant polymers have special properties that are valuable in the micro-encapsulation of sensitive biological agents; in the formation of hydrophobic, hydrophilic, or adhesive surfaces; in crosslinking reactions; and in the development of solid polymer electrolytes, bio-erodible polymers, pH-triggered hydrogels, polymer blends and interpenetrating polymer networks. Overall, more than 700 different polyphosphazenes are now known, and a large number of these are functional macromolecules targeted for specific property combinations and uses. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
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  • 58
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 707-713 
    ISSN: 0268-2605
    Schlagwort(e): polyhedral oligomeric silsesquioxane ; hybrid ; thermoplastic ; polymer ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A diverse and entirely new class of monomer and polymer technology based on polyhedral oligomeric silsesquioxane (POSS) reagents has been developed. POSS reagents are unique in that they are physically large (approx. 15 Å diameter and 1000 amu) and are composed of a robust silicon-oxygen framework that can be easily functionalized with a variety of organic substituents. Appropriate functionalization of POSS cages allows for their incorporation into traditional thermoplastic resins without modification of existing manufacturing processes. The incorporation of POSS segments into linear copolymer systems results in increased glass transition and decomposition temperatures, increased oxygen permeability and reduced flammability and heat evolution, as well as modified mechanical properties relative to conventional organic systems. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 6 Ill.
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  • 59
    ISSN: 0268-2605
    Schlagwort(e): organophosphazenes ; liquid crystals ; phase transition ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Organophosphazenes with a similar mesogenic moiety were prepared and their mesogenicity was studied by differential scanning calorinetry (DSC) measurements and polarizing microsope observations. In cyclotriphosphazenes with alk-­oxybiphenyl and Schiff base moieties, mesomorphic phase transitions were observed, but no mesomorphic phase was observed for the corresponding cyclotetraphosphazenes. In polyphos-­phazenes with an alkoxybiphenyl moiety, no mesomorphic phase was observed. The molecular structure of cyclotriphosphazenes facilitated the formation of a mesomorphic layer structure; in contrast, the formation of a mesomorphic layer structure did not occur in cyclotetraphosphazenes and polyphosphazenes, even though they bore a similar mesogenic moiety. Moreover, in cyclotriphosphazenes with an optically active alkoxybiphenyl group, a smectic C* phase was observed. The spontaneous polarization of the compound was -190 μ C m-2 at 436 K in 25 μ in cell using the triangular-wave method. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 7 Ill.
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  • 60
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 657-657 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 61
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 781-785 
    ISSN: 0268-2605
    Schlagwort(e): phosphonium ; polymer ; monomer ; film ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly(arylene ether) main-chain phosphonium ionomers were successfully synthesized and characterized. The reaction scheme involved first preparing the poly(arylene ether phosphine oxide) by a nucleophilic step or condensation polymerization of bisphenolates on activated aryl halides, wherein phenyl phosphine oxide was the activating group. High-molecular-weight, tough, film-forming polymers were produced with glass transition temperatures of 200°C or higher. The resulting materials were successfully reduced using phenylsilane in refluxing chlorobenzene. The derived phosphine or phosphine/phosphine oxide copolymer was reacted with alkyl halides to produce the phosphonium salts. The resulting materials showed enhanced hydrophilicity and in some cases could be successfully dispersed in water. In addition, chromophores such as Methyl Orange and Methyl Red were combined with the backbone ionomer to produce new film-forming, ionically linked species. The materials are of general interest for situations where water-dispersible intermediates, e.g. coatings, fiber sizings etc. are required. The phosphonium salts can be converted back to the phosphine oxide in fairly high yields by simple thermal methods and in quantitative yield by chemical methods (e.g. the Wittig reaction). © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 1 Ill.
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  • 62
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 681-693 
    ISSN: 0268-2605
    Schlagwort(e): ceramics ; preceramic polymers ; SiNCB composites ; boron nitride ; boron ; silicon ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Our recent work directed at the design, synthesis, characterization and applications of new types of polyborazylene and polyborosilazane polymers is reviewed with a focus on the use of these polymers as processable precursors to BN and SiNCB composites. A design strategy based on the controlled functionalization of preformed polymers with pendant groups of suitable compositions and crosslinking properties has been employed to yield second-generation dipentylamine-polyborazylene (DPA) and pinacolborane-hydridopolysilazane (PIN-HPZ) polymers, which, unlike the parent polyborazylene (PB) and the borazine-hydridopolysilazane (B-HPZ) polymers, are stable as melts and can be easily melt-spun into polymer fibers. Subsequent pyrolyses of these polymer fibers then provide excellent routes to BN and SiNCB ceramic fibers. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 11 Ill.
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  • 63
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 285-291 
    ISSN: 0268-2605
    Schlagwort(e): mushroom ; arsenic speciation ; HPLC-ICP-MS ; dimethylarsinic acid ; arsenobetaine ; trimethylarsine oxide ; toxicological evaluation ; soil contamination ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Samples of the edible mushroom Laccaria amethystina, which is known to accumulate arsenic, were collected from two uncontaminated beech forests and an arsenic-contaminated one in Denmark. The total arsenic concentration was 23 and 77 μg  As g-1 (dry weight) in the two uncontaminated samples and 1420 μg As g-1 in the contaminated sample. The arsenic species were liberated from the samples using focused microwave-assisted extraction, and were separated and detected by anion- and cation-exchange high-performance liquid chromatography with an inductively coupled plasma mass spectrometer as arsenic-selective detector. Dimethylarsinic acid accounted for 68-74%, methylarsonic acid for 0.3-2.9%, trimethylarsine oxide for 0.6-2.0% and arsenic acid for 0.1-6.1% of the total arsenic. The unextractable fraction of arsenic ranged between 15 and 32%. The results also showed that when growing in the highly arsenate-contaminated soil (500-800 μg As g-1) the mushrooms or their associated bacteria were able to biosynthesize dimethylarsinic acid from arsinic acid in the soil. Furthermore, arsenobetaine and trimethylarsine oxide were detected for the first time in Laccaria amethystina. Additionally, unidentified arsenic species were detected in the mushroom. The finding of arsenobetaine and trimethylarsine oxide in low amounts in the mushrooms showed that synthesis of this arsenical in nature is not restricted to marine biota. In order to minimize the toxicological risk of arsenic to humans it is recommended not to consume Laccaria amethystina mushrooms collected from the highly contaminated soil, because of a genotoxic effect of dimethylarsinic acid observed at high doses in animal experiments. © 1998 John Wiley & Sons, Ltd.No Abstract.
    Zusätzliches Material: 2 Ill.
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  • 64
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 299-299 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 65
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 299-301 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 66
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 301-301 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 67
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 301-302 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 68
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 327-335 
    ISSN: 0268-2605
    Schlagwort(e): zinc sulphide ; precipitation ; nanocrystallites ; nanopores ; optical transmission spectroscopy ; vibrational spectroscopy ; Raman spectroscopy ; X-ray diffraction ; transmission electron microscopy ; thermogravimetric analysis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: During the synthesis of ZnS powders by wet chemical precipitation, the formation of nanoporous spheres is observed. The powders have been investigated using thermogravimetric analysis, X-ray diffraction and optical spectroscopies. Nanopore formation can be explained by several stages of growth. The formation of nanoparticles as primary particles is followed by their agglomeration forming secondary particles. These secondary particles are monodispersed spheres with a considerable porosity, because the agglomeration of the nanoparticles is unlikely to be volume-filling. The voids or nanopores formed by this agglomeration process in the secondary particles is estimated to comprise around 35% of the sphere volume. They are mainly filled with water and the residues of the chemical reagents. Water in the pores partially reacts with ZnS and forms hydrated sulphates. The chemical reagents used for the precipitation reactions are also found to be bound to the nanocrystallite's surfaces as ligands in some cases. Depending on the reaction conditions and reagents, the agglomeration of the nanoparticles can also be modified or hindered by the use of complexing agents acting as a sterically stabilizing surface layer on the nanocrystallites. The agglomeration of nanoparticles to larger units being a general phenomenon, this use of complexing agents to control pore formation and agglomerate size should be applicable to other nanocrystalline systems. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 7 Ill.
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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 347-351 
    ISSN: 0268-2605
    Schlagwort(e): α-Fe2O3 ; nanoparticles ; Morin transition ; antiferromagnetism ; weak ferromagnetism ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The magnetic properties of α-Fe2O3 nanoparticles of different shapes (spherical, rhombohedral and acicular), prepared as powders by a chemical route, have been investigated. The particle size effect on the Morin transition (TM = 263 K in the bulk system) have been studied by analyzing the temperature dependence of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization. For spherical (average diameter between 10 and 50 nm) and rhombohedral (edge between 30 and 350 nm) particles, the Morin temperature was found to decrease with decreasing particle size and increasing magnetic field. On the other hand, acicular particles (major axis between 300 and 700 nm, minor axis between 70 and 100 nm) do not show the Morin transition, unless annealed. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 6 Ill.
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  • 70
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 361-365 
    ISSN: 0268-2605
    Schlagwort(e): silicon nanoparticles ; optical properties ; CO2 laser ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Silicon nanoparticles have been synthesized by heating reactant gases with a 500 W CO2 laser. A technique based on scattering of He-Ne laser light by particulates in a reaction flame has been developed for probing the particle size evolution during the process, in order to scale down the particle diameter (under 10 nm). The optical and structural properties of laser-synthesized silicon nanopowders obtained in different runs are reported. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 353-360 
    ISSN: 0268-2605
    Schlagwort(e): surface chemistry ; sodium nanoclusters ; optical spectroscopy ; plasmon excitation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The influence of molecular adsorbate layers on surface plasmon excitation in small supported metal particles has been investigated and exploited to study adsorption reactions on their surfaces. For this purpose sodium nanoclusters on quartz and LiF substrates served as model systems. Their optical transmission spectra are dominated by two maxima which are due to the excitation of surface plasmon resonances in the direction of the long and short axes of the oblate particles. By recording the spectra under ultrahigh-vacuum conditions and, subsequently, after exposure to gases such as O2, N2O, CO2, H2 and N2, changes in the optical spectra can be identified if the clusters are covered by as little as half a molecular monolayer. Depending on the adsorbed molecules, different modifications of the maximum position, the width and the amplitude of the surface plasmon resonances are observed. The results of a series of measurements together with calculations using the quasi-static approximation indicate that the variations in the spectra allow one to distinguish between physisorption and chemisorption, i.e. to characterize the strength of the chemical bond. In addition, diffusion of the molecules into the bulk of the particles can be detected. Particularly interesting is the observation that the clusters can experience a change in their shape if gases such as O2 or CO2 react with their surface. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 72
    ISSN: 0268-2605
    Schlagwort(e): alumina ; nanoporous membranes ; nanocomposites ; templates ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Three different examples have shown that nanoporous alumina membranes serve as ideal templates for the formation of nanostructured materials and also as a support of those materials in composites. The unique properties of such membranes (transparency, chemical resistivity, thermal stability, adjustable pore sizes etc.) and the very simple mode of generating these composites are the benefits of using this inorganic template material.
    Zusätzliches Material: 7 Ill.
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  • 73
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 303-303 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
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  • 74
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 427-433 
    ISSN: 0268-2605
    Schlagwort(e): laser ; chemical vapour deposition ; thin films ; Si/C/H materials ; divinylsilane ; silicon carbide ; polycarbosilane ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transversely excited atmospheric (TEA) CO2 laser-induced decomposition of divinylsilane in the gas phase yields unsaturated C2-C4 hydrocarbons, benzene and vinylsilane, and it represents a convenient process for chemical vapour deposition of thin solid films composed of silicon carbide and polycarbosilane. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
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  • 75
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 435-438 
    ISSN: 0268-2605
    Schlagwort(e): tributyltin ; radiolabelling ; 113Sn ; synthesis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method of synthesis of tributyl[113Sn]tin,­(n/C4H9)3113Sn(IV), from commercially avail-­able inorganic 113Sn(IV) is presented. Inorganic tin is first extracted in diethyl ether and reacted with C4H9MgCl to produce tetrabutyltin, (C4H9)4113Sn, which is then debutylated with HgCl2. The resulting tributyl[113Sn]tin chloride is isolated from the reaction mixture by successive extractions with hexane and aqueous Na2S2O3. The yield is 40-60% and the product obtained is 〉98% pure. It has the same specific activity as the starting 113Sn(IV), i.e. up to 550 MBq mg-1 Sn, making it suitable for use in environmental fate and toxicology studies at concentrations relevant of those found in the aquatic environment. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
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  • 76
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 439-447 
    ISSN: 0268-2605
    Schlagwort(e): high-performance liquid chromatography ; hydride generation ; atomic fluorescence spectrometry ; photo-oxidation ; arsenic speciation ; human urine ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The potential of coupling anion-exchange high-performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation is considered. The effects of hydrochloric acid and sodium tetrahydroborate concentrations on signal-to-background ratio, as well as argon and hydrogen flow rates, were investigated. Detection limits for arsenite, dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate were 0.17, 0.45, 0.30 and 0.38 μg l-1, respectively, using a 20-μl loop. Linearity ranges were 0.1-500 ng for As(III) and MMA (as arsenic), and 0.1-800 ng for DMA and As(V) (as arsenic). Arsenobetaine (AsB) was also determined by introducing an on-line photo-oxidation step after the chromatographic separation. In this case the limits of detection and linear ranges for the different species studied were similar to the values obtained previously for As(V). The technique was tested with a human urine reference material and a volunteer's sample. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 6 Ill.
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  • 77
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 475-478 
    ISSN: 0268-2605
    Schlagwort(e): organomercurials ; symmetrization ; column chromatography ; organomercury halides ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The symmetrization reaction of organomercury(II) chlorides (RHgCl) to R2Hg and HgCl2 in toluene solution under identical conditions using a basic alumina column has been studied­in order to compare the effect of the nature of the R groups on the extent of symmetrization. The efficiency of symmetrization depends markedly on the electron-withdrawing nature of­R, varying from 90-94% for R = trichlorovinyl or phenyl to 11% for R = 2,6-dimethylphenyl.© 1998 John Wiley & Sons, Ltd.
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  • 78
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 515-517 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 79
    ISSN: 0268-2605
    Schlagwort(e): iron ; clusters ; magnetic properties ; laser vaporization ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Clusters of iron produced in a laser vaporization source have been characterized with time-of-flight spectra and deposited on different substrates for production of films of varying thickness. The magnetic properties of these films with thicknesses of 60 and 120 nm were investigated using an alternating gradient magnetometer. The films exhibit mono-domain behavior from a broad size distribution which has been confirmed by transmission electron microscopy. Films were also investigated by Mössbauer spectroscopy, which showed fast relaxation in the particles at room temperature. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
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  • 80
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 485-489 
    ISSN: 0268-2605
    Schlagwort(e): polysulfone ; chelate-modified polysulfone ; DSC ; thermal stability ; X-ray ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chloro-terminated polysulfones with various molecular weights were chemically modified with bis(2,4-dihydroxybenzaldehyde)copper(II). The properties of modified polysulfones are compared with the unmodified ones, and an increase in glass transition temperatures, softening points and reduced viscosities of the former materials was observed. In addition, the chelate-modified polymers exhibited excellent thermal stability properties and semicrystalline patterns. Also, they provided transparent and flexible films. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
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  • 81
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 469-474 
    ISSN: 0268-2605
    Schlagwort(e): asymmetric catalysis ; diethylzinc ; alkylation ; chiral heterocyclic alcohols ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The asymmetric alkylation with diethylzinc of five heterocyclic aldehydes and benzaldehyde (for comparison) has been studied in the presence of two optically active amino alcohols: (S)-2-amino-1-butanol (AB) and (1S,2R)-N,N-dibutylnorephedrine (DBNE). A number of chiral (hetero)aromatic secondary alcohols were synthesized in high yields (95-98%) with enantioselectivity up to 92% enantiomeric excess (ee) in the presence of DBNE catalyst. Optically active thienyl and 4-pyridyl derivatives were prepared for the first time by catalytic asymmetric alkylation. The influence of the amount of DBNE on the enantioselectivity was investigated. In contrast to benzaldehyde, 2-furan- and 2-thiophene-carbaldehydes, in the case of 3- and 4-pyridinecarbaldehydes the ee values depend directly on the catalyst concentration. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 2 Ill.
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  • 82
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 521-521 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 83
    ISSN: 0268-2605
    Schlagwort(e): HPLC-ICP-MS ; cetaceans ; pinnipeds ; arsenic ; arsenobetaine ; arsenocholine ; whales ; seals ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Total arsenic concentrations and the concentrations of individual arsenic compounds were determined in liver samples of pinnipeds [nine ringed seals (Phoca hispida), one bearded seal (Erginathus barbatus)] and cetaceans [two pilot whales (Globicephalus melas), one beluga whale (Deliphinapterus leucus)]. Total arsenic concentrations ranged from 0.167 to 2.40 mg As kg-1 wet mass. The arsenic compounds extracted from the liver samples with a methanol/water mixture (9:1, v/v) were identified and quantified by anion- and cation-exchange chromatography. An ICP-MS equipped with a hydraulic high-pressure nebulizer served as the arsenic-specific detector. Arsenobetaine (0.052-1.67 mg As kg-1 wet mass) was the predominant arsenic compound in all the liver samples. Arsenocholine was present in all livers (0.005-0.044 mg As kg-1 wet mass). The tetramethylarsonium cation was detected in all pinnipeds (〈0.009 to 0.043 mg As kg-1) but not in any of the cetaceans. The concentration of dimethylarsinic acid ranged from 〈 0.001 to 0.109 mg As kg-1 wet mass. Most of the concentrations for methylarsonic acid (〈0.001 to 0.025 mg As kg-1 wet mass) were below the detection limit. Arsenous acid and arsenic acid concentrations were below the detection limit of the method (0.001 mg As kg-1). An unknown arsenic compound was present in all liver samples at concentrations from 0.002-0.027 mg As kg-1. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
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  • 84
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 520-520 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 85
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 520-520 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 86
    ISSN: 0268-2605
    Schlagwort(e): organotin ; N-(2-pyridylmethylene)arylamines ; IR ; NMR ; Mössbauer ; mutagenicity ; sister chromatid exchange ; cell cycle delay ; bone-marrow cells ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Diorganotin(IV) dichloride complexes of the type R2SnCl2·L (R = methyl, ethyl, vinyl, t-butyl, n-butyl or phenyl; L = N-(2-pyridylmethylene)arylamine) have been synthesized and characterized on the basis of IR, NMR and 119Sn Mössbauer studies. Investigation of the complexes indicated that N-(2-pyridylmethylene)arylamines form distorted trans-octahedral complexes with R2SnCl2 similar to the well-known R2SnCl2·L. Cytogenetic toxicology testing has been performed for Et2SnCl2·L4 [L4 = N-(2-pyridylmethylene)-4-toluidine] in mouse bone-marrow cells in vivo since such testing is a regulatory requirement before new drugs are released. This tin compound induced delay in cell-cycle kinetics and sister chromatid exchanges (SCEs) significantly. The effect of Et2SnCl2·L4 was greater when endogenous glutathione (GSH) was depleted by buthionine sulphoximine (BSO). It seems that Et2SnCl2·L4 induces SCEs due to formation of adduct by binding on DNA which could interfere in DNA synthesis and cause delay in cell proliferation. Depletion of GSH could reduce the shielding effect of GSH on chromatin and allows more Et2SnCl2·L4 to bind on DNA. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 1 Ill.
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  • 87
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
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  • 88
    ISSN: 0268-2605
    Schlagwort(e): platinum compound antileukaemic ; cytotoxic ; DNA ; thiosemicarbazone ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: p-Isopropylbenzaldehyde thiosemicarbazone (p-is.TSCN) (1) reacts with [Pt(µ-Cl)(η3-C4H7)]2 to form a dinuclear [Pt(µ-Cl)(p-is.TSCN)]2 complex (2) and a cyclometallated cluster [Pt(p-is.TSCN)]4 (3). Biological testing of these complexes against HL-60 and U-937 human leukemic cells suggest that complexes 2 and 3 may be endowed with important cytotoxic activity properties since they exhibit IC50 values (50% inhibition of cell growth) in the micromolar range, as does the clinically used drug cisplatin (cis-DDP). Analysis of the interaction of compounds 2 and 3 with DNA indicates that the kinetics of DNA platination due to compounds 2 and 3 is faster than that of cisplatin and that after 24 h of incubation most of the platinum centers are bound to DNA. Thus, it is likely that the cytotoxic activity displayed by compounds 2 and 3 may be correlated with their high level of DNA platination. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 1 Ill.
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  • 89
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 880-881 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
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  • 90
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 819-825 
    ISSN: 0268-2605
    Schlagwort(e): monobutyltins ; dibutyltins ; tributyltins ; water ; sediment ; Osaka Bay ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The concentration of tributyltin (TBT) in surface water from Osaka Bay ranged from 0.023 to 0.061 µg l-1 in 1989 and from not detected (ND) to 0.059 µg l-1 in 1990 while the proportion of TBT as a percentage of the total butyltins (BTs) was more than 40%. The concentration of TBT was also surveyed in the Port of Osaka and the Yodo River basin. TBT levels were highest in the estuary (the Port of Osaka), followed by sea areas (Osaka Bay) and rivers (Yodo River basin). A fairly high correlation coefficient between TBT concentration and salinity in water from the estuary and the sea areas was observed. This result shows that the TBT in the estuary water is diluted by seawater. Generally, the TBT concentrations in the water columns were distributed uniformly and the composition of the BTs was also constant. TBT was detected in sediment from Osaka Bay in the range from ND to 0.023 mg kg-1 dry weight with a high ratio of monobutyltin (MBT) to the total BTs. TBT in sediment core was also measured; its concentration decreased with core depth. It was estimated from these measurements that the release of TBT into Osaka Bay began in the 1960s. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 7 Ill.
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  • 91
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 882-883 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 884-884 
    ISSN: 0268-2605
    Schlagwort(e): Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No Abstract
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 861-871 
    ISSN: 0268-2605
    Schlagwort(e): diorganotin ; Pyrimidine ; complex ; Mössbauer ; IR ; NMR ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The complexes formed between the diorganotin(IV) moieties, R2Sn(IV), and the ligand 2-mercaptopyrimidine, (H)SPym, were investigated. Complexes R2SnHal(SPym) and R2Sn(SPym)2 [R = Me, iPr, nBu, iBu, tBu, cyclohexyl(Cy), Ph] were synthesized, and characterized by elemental analysis. In the solid state, chelation of SPym through S and N donors was established by IR spectroscopy, and the nature of the environment of tin centers was investigated by 119Sn Mössbauer spectroscopy. From the dynamics of 119Sn nuclei determined by variable-temperature measurements on representative compounds [Me2SnCl(SPym) and Cy2SnBr(SPym)], as well as by point-charge model treatment of nuclear quadrupole splitting parameters, it was inferred that Me2SnCl-­(SPym) may assume a trans-Me2 octahedral coordination geometry around tin in a monodimensional polymer, or a monomeric trigonal-bipyramidal structure (distorted). The latter type of structure was assigned to the other R2SnHal(SPym) species, while R2Sn(SPym)2 complexes assume a trans-octahedral, or skew trapezoidal, tin environment. In CHCl3-CDCl3 solutions, monomeric species occur (according to vapor-pressure osmometry), where 1H and 13C NMR spectroscopic parameters of SPym indicate the persistence of Sn chelation by S and N donor atoms. The Me2SnCl(SPym) species assume trigonal-bipyramidal structures with a chelating SPym ligand, in CDCl3 and C2H5OH solutions, according to the coupling constants 1J(119Sn,13C), as well as IR and 119Sn Mössbauer spectroscopic data. 119Sn NMR parameters fully correspond with data for the homologous complexes with 2-mercaptopyridine. Copyright © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 601-611 
    ISSN: 0268-2605
    Schlagwort(e): tributyltin ; triphenyltin ; bioavailability ; bioconcentration factors ; humic substances ; pH dependence ; speciation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Bioconcentration of triphenyltin (TPT) and tributyltin (TBT) was studied in the freshwater organisms Daphnia magna (zooplankton), Chironomus riparius (sediment organism) and Thymallus thymallus (fish yolk-sac larvae). TPT bioconcentration factors (BCFs) at pH 8 were highest for Thymallus (2200), followed by Chironomus (680) and Daphnia (190). The differences could not be fully explained by different total lipid contents. Metabolism and lower bioconcentration were observed for TBT in Chironomus. The BCFs of both TBT and TPT were higher at pH 8 than at pH 5, but the difference was much less pronounced than predicted by the octanol-water partition model. This suggests that, besides the hydroxide species (TBTOH and TPTOH), the cations (TBT+ and TPT+) are also taken up by the organisms to some extent and that the octanol-water partition model underestimates the uptake of the charged species. Low concentrations of humic substances (HS) led to small reduction in the bioconcentration of TPT in Daphnia and Thymallus, and a significant reduction occurred at relatively high concentrations of HS (〉10 mg C l-1). The results of this study provide an important basis for future investigations aiming at a better understanding of the bioavailability and fate of TBT and TPT in freshwater ecosystems. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 651-656 
    ISSN: 0268-2605
    Schlagwort(e): butyltin ; TBT ; DBT ; MBT ; beluga whales ; St Lawrence River estuary ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fifty-two beluga whale samples (Six liver samples, and 46 blubber samples including ones from different depths of the fat layer) from the St Lawrence River, Canada, were analyzed for butyltin compounds (mono-, di-, and tri-butyltin) with a view to investigating the occurrence and contamination of butyltin in these animals. A special procedure was also developed for the determination of butyltin compounds in blubber samples with high lipid content (up to 95%). Total-butyltin concentrations in liver samples were found to be much higher than those in the blubber samples. The concentrations of butyltin compounds in blubber samples were observed to be related to their lipid content. Concentration levels of butyltin species in beluga whale were compared with those in other marine vertebrates in other parts of the world. The presence of butyltin compounds in liver and blubber samples suggests the accumulation of these toxicants by beluga whale. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
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  • 96
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 613-620 
    ISSN: 0268-2605
    Schlagwort(e): manganese oxides ; montmorillonite ; kaolinite ; mercury(II) ; methylation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effects of freshwater sediment components such as kaolinite, montmorillonite and birnessite (δ-MnO2) on the biomethylation of mercury(II) in a synthetic growth medium (M-IIY) were assessed. Additions of kaolinite or montmorillonite to media containing mercuriC nitrate [Hg(NO3)2; 12 μg Hg ml-1] had no significant effect on either bacterial growth or the production of methylmercury (CH3Hg+). However, whereas the addition of birnessite resulted in only a small (ca 4%) increase in bacterial growth, it also produced a significant decrease (ca 50%) in the production of CH3Hg+. Further, it was demonstrated that, with the exception of kaolinite, adsorption of mercury(II) onto the sediment components before they were added to the M-IIY medium decreased its bioavailability, i.e., the amounts of CH3Hg+ produced from the adsorbed mercury(II) were significantly lower than those produced from equivalent concentrations of Hg(NO3)2 in the absence of the mineral colloids. In the case of montmorillonite, CH3Hg+ production was decreased by 21% relative to the control system. Most striking was the case of birnessite, in which no CH3Hg+ was detected after a 25 h incubation period and only very small quantities of CH3Hg+ (3-7 ng l-1) were present in the medium after 336 h. These data demonstrate that mineral colloids common in freshwater sediments significantly influence the extent of biomethylation of mercury(II) adsorbed on their surfaces. Birnessite, in particular, is a very effective inhibitor of the biomethylation of surface-bound mercury(II). Therefore, it may be possible to reduce the severity of mercury pollution in some aquatic environments by adding a reactive manganese oxide, such as birnessite, to the system and thereby to inhibit the transformation (methylation) of inorganic mercury(II) into the much more toxic CH3Hg+ species. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 97
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 621-634 
    ISSN: 0268-2605
    Schlagwort(e): quality ; phenytins ; mussel ; Certified Reference Material ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Organotin contamination of the marine environment can be considered one of the main environmental problems in the last 20 years. Starting from the ‘Arcachon case’, monitoring campaigns have been carried out worldwide in order to evaluate the concentration levels of these compounds in the marine environment. In 1987 the EC Standards, Measurements and Testing Programme (formerly BCR) started a ‘tin speciation’ project to assess and improve the quality of measurements in this field and to make available reference materials. Ten years of study within the framework of this project have produced results in the fields of method development and production of reference materials, particularly for butyltins. The quality of the phenyltin analytical results was lower than for butyltins and further efforts are still needed. To overcome this shortfall, the last certification campaign was aimed towards the certification of phenyltins, as well as butyltins, in a candidate mussel certified Reference Material. The results of the homogeneity and stability tests for phenyltins and of the certification campaign are presented here. The preparation of the material and the analytical methods used in the certification campaigns are also described. The certification of phenyltins was hindered by their lack of long-term stability; nevertheless, the exercise provided information about the state-of-the-art of phenyltin measurements in biological samples. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 725-734 
    ISSN: 0268-2605
    Schlagwort(e): precursor ; ceramic ; thermolysis ; silicon ; carbodi-imide ; boron ; hydroboration ; plastic forming ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis, by two different reaction pathways, of boron-modified polysilylcarbodi-imides of general type {B[C2H4Si(R)NCN]3}n (R =­singly bonded organic ligand) and the plastic-forming and the thermal behavior of these polymers are described. Compounds {B[C2H4Si(R)NCN]3}n [2a, R = H; 2b, R = CH3; 2c, R = (NCN)0.5] can be obtained by treatment of the vinyl-substituted polysilylcarbodi-imides [(H2C=CH)(R)SiNCN]n [1a, R = H; 1b, R = CH3; 1c, R = (NCN)0.5] with borane dimethylsulfide BH3·S(CH3)2. The polysilylcarbodi-imides 1a-1c themselves are accessible via the reaction of vinyl-substituted chlorosilanes (H2C=CH)-­(R)SiCl2 with cyanamide H2N-C≡N in the presence of pyridine or by a non-oxide sol-gel process of vinylated chlorosilanes and bis(trimethylsilyl)carbodi-imide, (H3C)3SiN=C=NSi(CH3)3. In the second method for the synthesis of 2a-2c, hydroboration of vinyl-substituted chlorosilanes (H2C=CH)(R)SiCl2 with borane dimethylsulfide, borane trimethylamide or borane triethylamide to yield the tris[(chlorosilyl)ethyl]boranes B[C2H4Si(R)Cl2]3 (3a, R = H; 3b, R = CH3; 3c, R = Cl) is followed by treatment of the as-obtained compounds with bis(trimethylsilyl)carbodi-imide, which results in the formation of the hydroborated polysilylcarbodi-imides 2a-2c. The thermogravimetric behavior of the polymers 1a-1c and 2a-2c up to 2300°C is reported. It is shown that boron-modified polysilylcarbodi-imides are suitable precursors for the preparation of dense bulk ceramics. Therefore, the preparation of green bodies of the hydroborated polysilylcarbodi-imides 2a-2c by plastic forming (PF) is described. A series of experiments points to the fact that the microstructure of the as-obtained ceramic monoliths obtained by subsequent thermolysis of the plastic-formed green bodies is strongly influenced by the conditions during plastic forming. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 9 Ill.
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  • 99
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 715-723 
    ISSN: 0268-2605
    Schlagwort(e): Cubic Silsesquioxanes ; interface ; materials ; hybrids ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cubic silsesquioxanes, [RSiO1.5]x, potentially offer access to organic/inorganic hybrids wherein the exact shape, size and mechanical properties of the inorganic component are perfectly defined. Furthermore, by tailoring the organic functionality bound to silicon, the inorganic/organic interface can also be perfectly defined. Finally, careful selection of the polymerizable groups in the organic moieties can provide good-to-excellent control of the crosslinked density or degree of polymerization of the resulting hybrid materials. Thus, cubic silsesquioxanes may be exceptional model materials for inorganic/organic hybrids. Methods of synthesizing cubes with liquid-crystalline and/or polymerizable organic moieties are described. Some thermal properties are discussed. The catalytic copolymerization of the octavinyldimethylsiloxy-functionalized cube with the octahydridodimethyl-­siloxy-functionalized cube to produce a material with well-defined microporosity and high surface area is described. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 675-680 
    ISSN: 0268-2605
    Schlagwort(e): polymer ; nanocomposites ; silicates ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polymer nanocomposites, especially polymer-layered silicate (PLS) nanocomposites, represent a radical alternative to conventionally (macroscopically) filled polymers. Because of their nanometer-size dispersion, the nanocomposites exhibit markedly improved properties when compared with the pure polymers or conventional composites. These include increased modulus and strength, decreased gas permeability, increased solvent and heat resistance and decreased flammability. In addition to their potential applications, PLS nanocomposites are also unique model systems to study the structure and dynamics of polymers in confined environments. Using both delaminated and intercalated hybrids, the statics and dynamics of polymers confined over distances ranging from the radius of gyration of the polymer to the statistical segment length of the chains can be studied. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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