Models for the description of uniaxially modulated materials

Models which allow an explicit application to structurally modulated substances are reviewed within the frame of a symmetry-based approach starting from discrete lattice theory. Focus is set on models formulated in terms of local variables assigned to discrete crystallographic units (unit cells or parts of them). Especially considered are symmetry-based pseudo spin models. Methods are discussed which permit the handling of the statistical mechanics of such models, the translation of model calculation results to a form allowing the prediction of experimental data, and the theoretical determination of point defect influences.Comment: 25 pages, 10 figures, RevTex, to be published in Ferroelectric

Derivation of symmetry-based pseudo spin models for modulated materials

A general concept for the derivation of symmetry-based pseudo spin Hamiltonians is described. It systematically bridges the gap between the atomistic basis and various pseudo spin models presented in literature. It thus allows the application of the multitude of analytical and numerical procedures derived for the statistical mechanics treatment of the latter to the description of structurally modulated crystals and furnishes a general frame for reviewing these models from a common point of view.Comment: 4 pages, RevTe

Transitions between Phases with Equal Wave Numbers in a Double Ising Spin Model. Application to Betaine Calcium Chloride Dihydrate

A Double Ising Spin model for uniaxially structurally modulated materials exhibits as a special feature phase transitions between phases with equal wave numbers but different pseudo spin configurations. The character of these `internal' transitions is investigated in mean field approximation, with the mean field transfer matrix method, and in Monte Carlo simulations. The structural changes at the transitions are characterized by different strengths of harmonics in a Fourier analysis of the spatial modulation. A dielectric anomaly in the phase diagram of betaine calcium chloride dihydrate (BCCD) and seemingly contradictory structure analyses are explained.Comment: 14 pages, 9 figures, submitted to J. Phys. Condens. Matte

Proceedings of a Workshop on Cosmogenic Nuclide Production Rates

Abstracts of reports from the proceedings are presented. The presentations were divided into discussion topics. The following general topic areas were used: (1) measured cosmogenic noble gas and radionuclide production rates in meteorite and planetary surface samples; (2) cross-section measurements and simulation experiments; and (3) interpretation of sample studies and simulation experiments

Radiation protection culture: a global challenge

The central motto ‘Radiation Protection Culture—A Global Challenge' of the fourth European IRPA Congress is discussed on the basis of the IRPA Guiding Principles Establishing a Radiation Protection Culture and the contributions presented in the plenary sessions of the conferenc

Behavioural and abstractor specifications

AbstractIn the literature, one can distinguish two main approaches to the definition of observational semantics of algebraic specifications. On one hand, observational semantics is defined using a notion of observational satisfaction for the axioms of the specifications and, on the other hand, one can define observational semantics by abstraction with respect to an observational equivalence relation between algebras. In this paper, we present an analysis and a comparative study of the different approaches in a more general framework which subsumes the observational case. The distinction between the different observational concepts is reflected by our notions of behavioural specification and abstractor specification. We provide necessary and sufficient conditions for the semantical equivalence of both kinds of specifications and we show that behavioural specifications can be characterized by an abstractor construction and, vice versa, abstractor specifications can be characterized in terms of behavioural specifications. Hence, there exists a duality between both concepts which allows to express each one by the other. We also study the relationships to fully abstract algebras which can be used for a further characterization of behavioural semantics. Finally, we provide proof-theoretic results which show that behavioural theories of specifications can be reduced to standard theories of some classes of algebras

Entering new areas in known fields: recombinant fusion protein linking recombinant factor VIIa with recombinant albumin (rVIIa-FP) – advancing the journey

ABSTRACTThe novel fusion protein linking recombinant factor VIIa with recombinant albumin (rVIIa-FP) is designed to extend the half-life of recombinant factor VIIa (rFVIIa) and improve the care of hemophilia A or B patients with inhibitors. Preclinical studies in various animal models have demonstrated markedly improved pharmacokinetic and pharmacodynamic properties, as well as prolonged retention in the joint tissues, of rVIIa-FP compared with a commercially available rFVIIa (NovoSeven®). A phase I study in healthy volunteers – the first study in the PROLONG-7FP program – confirmed that rVIIa-FP has a good tolerability profile in doses of up to 1,000μg/kg and has demonstrated enhanced pharmacodynamic activity relative to rFVIIa. The half-life of rVIIa-FP at the highest dose investigated in the study was 8.5hours, which represents a 3- to 4-fold half-life extension compared with rFVIIa. Encouraging results from preclinical and phase I studies have led to the initiation of clinical studies of rVIIa-FP in patients with congenital hemophilia A or B and inhibitors, and in patients with confirmed factor VII deficiency. The results from these studies are awaited with interest by clinicians and patients alike

The Aids policy cycle in Western Europe: From exceptionalism to normalization

In every Western European country the occurrence of Aids has led to exceptional innovations in prevention, patient care, health policy and questions of civil rights. This exception can be explained not only by the fact that a health catastrophe was feared, but also civilizational harm in the field of civil rights. Despite national differences, this brought about similar exceptionalist alliances consisting of health professionals, social movements and those affected. With the failure of a catastrophe to arise signs of fatigue in the exceptionalist alliance and increasing possibilities of medical treatment, exceptionalism in Europe is drawing to a close. The paper elucidates specific aspects of each of the four roughly distinguishable phases in this process: Approx. 1981 - 1986: emergence of exceptionalism. The underlying reasons for exceptionalism are investigated in this paper. Approx. 1986 - 1991: consolidation and performance of exceptionalism. The paper investigates the exceptionalist policy model, more specifically some nationally different factors in the polity and politics that help to explain the different forms of policies. Approx. 1991 - 1996: exceptionalism crumbling, steps toward normalization. The forces driving the process of normalization are investigated. Since 1996: normalization, normality. The changes made in the management of HIV and Aids are elucidated using examples from the fields of health care, primary prevention and drug policies. Aids health-policy innovations, and their risks and opportunities in the course of normalization are investigated. Three possible paths of development are identified: stabilization, generalization and retreat. The chances of utilizing innovations developed in connection with Aids for the modernization of health policy in other fields of prevention and patient care vary from country to country with the degree to which Aids exceptionalism has been institutionalized and the distance of these innovations from medical/therapeutic events. The contribution made by European countries to containing the global Aids crisis is inadequate. --

Continuous-Time Identification of SISO Systems using Laguerre Functions

This paper looks at the problem of estimating the coefficients of a continuous-time transfer function given samples of its input and output data. We first prove that any nth-order continuous-time transfer function can be written as a fraction of the form /spl Sigma//sub k=0//sup n/b~/sub k/L/sub k/(s)//spl Sigma//sub k=0//sup n/a~/sub k/L/sub k/(s), where L/sub k/(s) denotes the continuous-time Laguerre basis functions. Based on this model, we derive an asymptotically consistent parameter estimation scheme that consists of the following two steps: (1) filter both the input and output data by L/sub k/(s), and (2) estimate {a~/sub k/, b~/sub k/} and relate them to the coefficients of the transfer function. For practical implementation, we require the discrete-time approximation of L/sub k/(s) since only sampled data is available. We propose a scheme that is based on higher order Pade approximations, and we prove that this scheme produces discrete-time filters that are approximately orthogonal and, consequently, a well-conditioned numerical problem. Some other features of this new algorithm include the possibility to implement it as either an off-line or a quasi-on-line algorithm and the incorporation of constraints on the transfer function coefficients. A simple example is given to illustrate the properties of the proposed algorithm

δ 15N measurement of organic and inorganic substances by EA-IRMS: a speciation-dependent procedure

Little attention has been paid so far to the influence of the chemical nature of the substance when measuring δ 15N by elemental analysis (EA)-isotope ratio mass spectrometry (IRMS). Although the bulk nitrogen isotope analysis of organic material is not to be questioned, literature from different disciplines using IRMS provides hints that the quantitative conversion of nitrate into nitrogen presents difficulties. We observed abnormal series of δ 15N values of laboratory standards and nitrates. These unexpected results were shown to be related to the tailing of the nitrogen peak of nitrate-containing compounds. A series of experiments were set up to investigate the cause of this phenomenon, using ammonium nitrate (NH4NO3) and potassium nitrate (KNO3) samples, two organic laboratory standards as well as the international secondary reference materials IAEA-N1, IAEA-N2—two ammonium sulphates [(NH4)2SO4]—and IAEA-NO-3, a potassium nitrate. In experiment 1, we used graphite and vanadium pentoxide (V2O5) as additives to observe if they could enhance the decomposition (combustion) of nitrates. In experiment 2, we tested another elemental analyser configuration including an additional section of reduced copper in order to see whether or not the tailing could originate from an incomplete reduction process. Finally, we modified several parameters of the method and observed their influence on the peak shape, δ 15N value and nitrogen content in weight percent of nitrogen of the target substances. We found the best results using mere thermal decomposition in helium, under exclusion of any oxygen. We show that the analytical procedure used for organic samples should not be used for nitrates because of their different chemical nature. We present the best performance given one set of sample introduction parameters for the analysis of nitrates, as well as for the ammonium sulphate IAEA-N1 and IAEA-N2 reference materials. We discuss these results considering the thermochemistry of the substances and the analytical technique itself. The results emphasise the difference in chemical nature of inorganic and organic samples, which necessarily involves distinct thermochemistry when analysed by EA-IRMS. Therefore, they should not be processed using the same analytical procedure. This clearly impacts on the way international secondary reference materials should be used for the calibration of organic laboratory standards. Figure Control chart of the δ 15N value of IAEA-N1, IAEA-NO-3 and NH4NO3 analysed a) with oxygen injection (analytical cycle 70 s, oxygen for 60 s, sample start and stop at 18 s/20 s), b) with oxygen injection (analytical cycle 70 s, oxygen for 60 s, sample start and stop at 0 s/2 s and 5 s/7 s), c) without oxygen injection (analytical cycle 70 s, sample start and stop at 18 s/20 s