Showing papers by "University of Kiel published in 1996"

GPOWER: A general power analysis program

Abstract: GPOWER is a completely interactive, menu-driven program for IBM-compatible and Apple Macintosh personal computers. It performs high-precision statistical power analyses for the most common statistical tests in behavioral research, that is,t tests,F tests, andχ2 tests. GPOWER computes (1) power values for given sample sizes, effect sizes andα levels (post hoc power analyses); (2) sample sizes for given effect sizes,α levels, and power values (a priori power analyses); and (3)α andβ values for given sample sizes, effect sizes, andβ/α ratios (compromise power analyses). The program may be used to display graphically the relation between any two of the relevant variables, and it offers the opportunity to compute the effect size measures from basic parameters defining the alternative hypothesis. This article delineates reasons for the development of GPOWER and describes the program’s capabilities and handling.

Partially Molten Middle Crust Beneath Southern Tibet: Synthesis of Project INDEPTH Results

Abstract: INDEPTH geophysical and geological observations imply that a partially molten midcrustal layer exists beneath southern Tibet. This partially molten layer has been produced by crustal thickening and behaves as a fluid on the time scale of Himalayan deformation. It is confined on the south by the structurally imbricated Indian crust underlying the Tethyan and High Himalaya and is underlain, apparently, by a stiff Indian mantle lid. The results suggest that during Neogene time the underthrusting Indian crust has acted as a plunger, displacing the molten middle crust to the north while at the same time contributing to this layer by melting and ductile flow. Viewed broadly, the Neogene evolution of the Himalaya is essentially a record of the southward extrusion of the partially molten middle crust underlying southern Tibet.

Lot sizing and scheduling: Survey and extensions

Abstract: This contribution summarizes recent work in the field of lot sizing and scheduling. The objective is not to give a comprehensive literature survey, but to explain differences of formal models and to provide some first readings recommendations. Our focus is on capacitated, dynamic, and deterministic cases. To underscore the importance of the research efforts, current practice is described and its shortcomings are exposed. Mathematical programming models where the planning horizon is subdivided into several discrete periods are given for both, approaches that are well-established and approaches which may represent tomorrow's state of the art. Two research directions are discussed in more detail: Continuous time models and multi-level lot sizing and scheduling. The paper concludes with some advice for future research activities.

A genomic polymorphism within the tumor necrosis factor locus influences plasma tumor necrosis factor-alpha concentrations and outcome of patients with severe sepsis.

Abstract: ObjectivesTo determine the allele frequency and genotype distribution of a bi-allelic tumor necrosis factor (TNF) gene polymorphism and plasma TNF-alpha concentrations in postoperative intensive care unit (ICU) patients suffering from severe sepsis.DesignProspective, consecutive entry study of patie

PSPLIB - a project scheduling problem library

Abstract: We present a set of benchmark instances for the evaluation of Solution procedures for single- and multi-mode resource-constrained project scheduling problems. The instances have been systematically generated by the Standard project generator ProGen. They are characterized by the input-parameters of ProGen. The entire benchmark set including its detailed characterization and the best solutions known so-far are available on a public ftp-site. Hence, researchers can download the benchmark sets they need for the evaluation of their algorithms. Additionally, they can make available new results. Depending on the progress made in the field, the instance library will be continously enlarged and new results will be made accessible. This should be a valuable and driving source for further improvements in the area of project type scheduling.

Faecal elastase 1: a novel, highly sensitive, and specific tubeless pancreatic function test.

Abstract: BACKGROUND: Indirect pancreatic function tests available today are unreliable for clinical practice in early chronic pancreatitis due to their low sensitivity in mild and moderate exocrine pancreatic insufficiency. AIM: To evaluate the sensitivity, specificity, and practicability of faecal elastase 1 determination in patients with mild, moderate, and severe exocrine pancreatic insufficiency categorised according to the secretin-caerulein test as "gold standard'. PATIENTS AND METHODS: Faecal and duodenal elastase 1 concentration (commercial enzyme linked immunosorbent assay (ELISA)), faecal chymotrypsin activity, faecal fat analysis, and the secretin-caerulein test were performed on 44 patients with mild (n = 8), moderate (n = 14), and severe (n = 22) exocrine pancreatic insufficiency and 35 patients with gastrointestinal diseases of non-pancreatic origin. Fifty healthy volunteers were studied as normal controls. Morphological examinations were carried out to definitely confirm or exclude chronic pancreatitis. RESULTS: With a cut off of 200 micrograms elastase 1/g stool the sensitivity was 63% for mild, 100% for moderate, 100% for severe, and 93% for all patients with exocrine pancreatic insufficiency, and specificity was 93%. Values for chymotrypsin were 64% (sensitivity) and 89% (specificity). Significant (p < 0.001) correlations were found for faecal and duodenal elastase with duodenal lipase, amylase, trypsin, volume, and bicarbonate output. Individual day to day variations of faecal elastase 1 concentrations were very low (mean CV = 15%) and sample storage at room temperature is possible for at least one week. CONCLUSIONS: Faecal elastase 1 determination proved to be a highly sensitive and specific tubeless pancreatic function test.

On the mechanism of the post-activation depression of the H-reflex in human subjects

Abstract: It was demonstrated that the soleus H-reflex was depressed for more than 10 s following a preceding passive dorsiflexion of the ankle joint. This depression was caused by activation of large-diameter afferents with receptors located in the leg muscles, as an ischaemic block of large-diameter fibres just below the knee joint abolished the depression, whereas a similar block just proximal to the ankle joint was ineffective. The depression of the H-reflex was not caused by changes in motoneuronal excitability, as motor-evoked potentials by magnetic brain stimulation were not depressed by the same passive dorsiflexion. Therefore it was concluded that the long-lasting depression is due to mechanisms acting at presynaptic level. The transmission of the monosynaptic Ia excitation from the femoral nerve to soleus motoneurones was not depressed by the ankle dorsiflexion. The depression thus seems to be confined to those afferents that were activated by the conditioning dorsiflexion. In parallel experiments on decerebrate cats, more invasive methods have complemented the indirect techniques used in the experiments on human subjects. A similar long-lasting depression of triceps surae monosynaptic reflexes was evoked by a preceding conditioning stimulation of the triceps surae Ia afferents. This depression was accompanied by a reduction of the monosynaptic Ia excitatory postsynaptic potential recorded intracellularly in triceps surae motoneurones, but not by changes in the input resistance or membrane potential in the motoneurones. Stimulation of separate branches within the triceps surae nerve demonstrated that the depression is confined to those afferents that were activated by the conditioning stimulus. This long-lasting depression was not accompanied by a dorsal root potential. It is concluded that the long-lasting depression is probably caused by a presynaptic effect, but different from the “classical” GABAergic presynaptic inhibition which is widely distributed among afferent fibres and accompanied by dorsal root potentials. It is more probably related to the phenomenon of a reduced transmitter release from previously activated fibres, i.e. a homosynaptic post-activation depression. The consequences of this post-activation depression for the interpretation of results on spinal mechanisms during voluntary movements in man are discussed.

Experimental investigation of the melting transition of the plasma crystal.

Abstract: Measurements of the melting transition of a Coulomb crystal consisting of dust particles immersed in an rf parallel plate discharge in helium were performed. The dust crystal is shown to be solid at higher gas pressure (120 Pa) and low discharge power (10--20 W). Reducing the gas pressure or increasing the discharge power leads to fluid states of the dust ensemble. Even gaslike states are observed at low pressures of about 40 Pa. The transition is attributed to an increasing effective particle temperature. The phase transition is compared with one-component-plasma and Yukawa models, and with basic predictions of theories for two-dimensional melting. \textcopyright{} 1996 The American Physical Society.

Epidural anaesthesia and spinal haematoma.

Abstract: Purpose Haematoma formation in the spinal canal due to epidural anaesthesia is a very rare but serious complication. This paper presents a comprehensive review of case reports.

Teleconnections Between the Subtropical Monsoons and High-Latitude Climates During the Last Deglaciation

Abstract: The major deglacial intensification of the southwest monsoon occurred at 11,450 ± 150 calendar years before present, synchronous with a major climate transition as recorded in Greenland ice. An earlier event of monsoon intensification at 16,000 ± 150 calendar years before present occurred at the end of Heinrich layer 1 in the Atlantic and parallels the initial rise in global atmospheric methane concentrations and the first abrupt climate changes in the Antarctic; thus, the evolution of the monsoonal and high-latitude climates show teleconnections but hemispheric asymmetries. Superimposed on abrupt events, the monsoonal climate shows high-frequency variability of 1785-, 1450-, and 1150-year oscillations, and abrupt climate change seems to occur when at least two of these oscillations are in phase.

Interactions of sympathetic and primary afferent neurons following nerve injury and tissue trauma.

Abstract: Sympathetic post-ganglionic neurons may be involved in the generation of pain, hyperalgesia and inflammation under pathophysiological conditions. Two categories of influence of the sympathetic neuron on afferent neurons can be distinguished and this distinction seems to be related to whether the coupling between afferent and sympathetic neuron develops after nerve lesion or after tissue trauma with inflammation (Fig. 15): A. Peripheral nerve lesion generates plastic changes of the afferent and sympathetic postganglionic neurons, depending on the type of nerve lesion (e.g. complete, partial). Both afferent and post-ganglionic neurons exhibit degenerative and regenerative changes and unlesioned neurons may show collateral sprouting in the periphery as well as in the dorsal root ganglion. This reorganization of the peripheral neurons may lead to chemical coupling between sympathetic and afferent neurons. The coupling is responsible for sensitization and/or activation of primary afferent neurons by the sympathetic neurons. The mediator probably is norepinephrine, but other substances cannot be excluded. The afferent neuron expresses or upregulates functional adrenoceptors. The type of adrenoceptor involved is probably alpha 2. The coupling may occur at different sites of the primary afferent neuron, e.g. at the lesion site, remote from the lesion site in the dorsal root ganglion or between nonlesioned sympathetic and afferent neurons which show collateral sprouting. The biochemical signals which trigger these changes probably are neurotrophic substances, their receptors which are synthesized by the peripheral neurons, Schwann cells and other cells in response to the peripheral lesions. B. Sympathetic nerve terminals in peripheral tissues may serve as mediator elements in hyperalgesia and inflammation following tissue trauma without nerve lesion. Experiments show that these functions are largely independent of activity in the sympathetic neurons and independent of vesicular release of transmitter substances (such as norepinephrine). Sensitization of nociceptive afferents for mechanical stimuli and venular plasma extravasation in the synovium which are induced by the inflammatory mediator bradykinin are, at least in part, dependent on the sympathetic terminal. The signal to venules and afferent receptors is synthesized and released from the sympathetic terminal or in association with it. It is a prostaglandin (probably PGE2). Sympathetically mediated (neurogenic) inflammation and neurogenic inflammation mediated by afferents may interact reciprocally and enhance the inflammatory process as well as the sensitization of nociceptive afferents. Norepinephrine may also lead to sensitization of nociceptive afferents under inflammatory conditions. This sensitization is presumably mediated by alpha 2-adrenoceptors in the sympathetic varicosities and by a prostaglandin (probably PGI2) which is synthesized and released by or in association with the sympathetic varicosities.

Soluble HLA class I molecules induce apoptosis in alloreactive cytotoxic T lymphocytes.

Abstract: Soluble HLA class I molecules (sHLAs) have been identified in the serum of patients with inflammatory diseases, allografts and autoimmune diseases and in serum of healthy individuals. The biological significance of these molecules, particularly after allogeneic organ transplantation, has been enigmatic. Here we show that primary alloreactive CD8+ T cells interact with sHLA and undergo apoptosis in the absence of a second signal. Ligation of CD28 rescued T cells from death, implying that sHLAs induce apoptosis through selective stimulation of the T-cell receptor. CD95-L was upregulated after cytotoxic T lymphocytes were incubated with sHLAs, and cell death was blocked by a neutralizing anti-CD95-L antibody, suggesting that sHLAs induce endogenous mutual killing of activated T cells. These results provide a molecular basis for the capacity of sHLAs to downregulate T-cell responses, which may be especially relevant to organ transplantation.

Lay persons’ and police officers’ beliefs regarding deceptive behaviour

Abstract: Research on the detection of deception, via non-verbal cues, has shown that people's ability to successfully discriminate between truth and deception is only slightly better than chance level. One of the reasons for these disappointing findings possibly lies in people's inappropriate beliefs regarding ‘lying behaviour’. A 64-item questionnaire originally used in Germany, which targets participants' beliefs regarding truthful and deceptive behaviour, was used. The present study differed from previous research in three ways: (i) instead of a student population, police officers and lay people were sampled, (ii) both people's beliefs regarding others' deceptive behaviour and their beliefs regarding their own deceptive behaviour were examined, and (iii) both non-verbal cues to, and content characteristics of, deceptive statements were examined. Results were consistent with previous studies, which found significant differences between people's beliefs regarding deceptive behaviour and experimental observations of actual deceptive behaviour. Further, police officers held as many false beliefs as did lay people and finally, participants were more accurate in their beliefs regarding their own deceptive behaviour than they were in their beliefs regarding others' behaviour.

Bootstrapping Goodness-of-Fit Measures in Categorical Data Analysis:

Abstract: When sparse data have to be fitted to a log-linear or latent class model, one cannot use the theoretical chi-square distribution to evaluate model fit, because with sparse data the observed cross-table has too many cells in relation to the number of observations to use a distribution that only holds asymptotically. The choice of a theoretical distribution is also difficult when model-expected frequencies are 0 or when model probabilities are estimated 0 or 1. The authors propose to solve these problems by estimating the distribution of a fit measure, using bootstrap methods. An algorithm is presented for estimating this distribution by drawing bootstrap samples from the model-expected proportions, the so-called nonnaive bootstrap method. For the first time the method is applied to empirical data of varying sparseness, from five different data sets. Results show that the asymptotic chi-square distribution is not at all valid for sparse data.

Dissemination of Information in Interconnection Networks (Broadcasting & Gossiping)

Abstract: Considerable attention in recent theoretical computer science is devoted to parallel computing. Here, we would like to present a special part of this large topic, namely, the part devoted to an abstract study of the dissemination of information in interconnection networks. The importance of this research area lies in the fact that the ability of a network to effectively disseminate information is an important qualitative measure for the suitabilty of the network for parallel computing. This follows simply from the observation that the communication among processes working in parallel is one of the main parts of the whole parallel computation. So, the effectivity of information exchange among processors essentially influences the effectivity of the whole computation process.

Alignment and instability of dust crystals in plasmas.

Abstract: Charged dust particulates, forming a layered crystal in the electrode sheath of a rf discharge, are known to show vertical alignment and an onset of characteristic oscillations below a threshold of neutral gas density. Here forces on the particulates due to the formation of positive space-charge clouds below the dust particles are calculated from Monte Carlo calculations of the ion motion in the sheath. The forces are shown to be attractive and nonreciprocal for the different crystal layers. From the Monte Carlo results an analytical lattice model is derived that quantitatively explains the experimental findings. \textcopyright{} 1996 The American Physical Society.

Clinical neurophysiology of tremor.

Abstract: The neurophysiological analysis of tremor has a long tradition. These attempts were directed to understand the mechanisms underlying tremor, on the one hand, and to develop tools to better diagnose the different types of tremor, on the other. Meanwhile, reasonable criteria are available to distinguish between centrally and peripherally mediated tremors. However, no generally accepted means exist to differentiate the different forms of central tremors. Frequency is a useful classifier for cerebellar tremor, rubral tremor, and orthostatic tremor. Although the highest amplitudes are found in Parkinson's disease, this parameter does not well distinguish between the different tremors. Waveform analysis of tremor is a promising tool to separate between the different tremors. Polymyography is pathognomonic for some rare forms of tremor. New approaches to classify tremors are based on positron emission tomography scanning, analysis of ballistic movement, and reflex testing. The means to separate myoclonias from tremors include EEG/EMG correlation techniques, long-latency reflexes, and polymyography. Provided these techniques are applied in the setting of careful clinical analysis of tremor syndromes, they may prove to be helpful in clinical practice.

Structure and stability of the plasma crystal

Abstract: The plasma crystal formed by monodisperse particles trapped in the sheath of an rf discharge is known to show vertically aligned structures. Here, oscillations of the aligned particles are found below a threshold value of gas density as a precursor of the melting transition. Attractive forces due to the formation of a positive space-charge region below the upper particle are calculated from Monte Carlo simulations of ion trajectories in the sheath. The alignment as well as the oscillations of the plasma crystal are explained by a simple model based on the asymmetry of the forces.

Magnesium in the prophylaxis of migraine-a double-blind, placebo-controlled study

Abstract: The migraine prophylactic effect of 10 mmol magnesium twice-daily has been evaluated in a multicentre, prospective, randomized, double-blind, placebo-controlled study. Patients with two to six migraine attacks per month without aura, and history of migraine of at least 2 years, were included. A 4-week baseline period without medication was followed by 12 weeks of treatment with magnesium or placebo. The primary efficacy end-point was a reduction of at least 50% in intensity or duration of migraine attacks in hours at the end of the 12 weeks of treatment compared to baseline. With a calculated total sample size of 150 patients, an interim analysis was planned after completing treatment of at least 60 patients, which in fact was performed with 69 patients (64F, 5M), aged 18-64 years. Of these, 35 had received magnesium and 34 placebo. The number of responders was 10 in each group (28.6% under magnesium and 29.4% under placebo). As determined in the study protocol, this was a major reason to discontinue the trial. With regard to the number of migraine days or migraine attacks there was no benefit with magnesium compared to placebo. There were no centre-specific differences, and the final assessments of treatment efficacy by the doctor and patient were largely equivocal. With respect to tolerability and safety, 45.7% of patients in the magnesium group reported primarily mild adverse events like soft stool and diarrhoea in contrast to 23.5% in the placebo group.