Showing papers by "University of Kiel published in 1995"

Singular Integral Equations

Abstract: Let the function f be defined on I=[a,b] and, possibly, be singular at an interior point c∈(a,b). Recall that the improper integral was defined by $$\int\limits_{a}^{b} {f\left( x \right)} dx: = \mathop{{\lim }}\limits_{{\mathop{{{{\varepsilon }_{1}} \to 0}}\limits_{{{{\varepsilon }_{1}} > 0}} }} \int\limits_{a}^{{c - {{\varepsilon }_{1}}}} {f\left( x \right)} dx + \mathop{{\lim }}\limits_{{\mathop{{{{\varepsilon }_{2}} \to 0}}\limits_{{{{\varepsilon }_{2}} > 0}} }} \int\limits_{{c + {{\varepsilon }_{2}}}}^{b} {f\left( x \right)dx,} $$ if both limits exist (cf. §6.1.3). By Remark 6.1.2a, the improper integral exists for f (x): = |x-c|s with s>-1. For \( f(x): = \frac{1}{{x - c}}({\text{i}}{\text{.e}}{\text{.,s = - 1}}) \) (i.e, s=-1) one obtains $$\int\limits_{a}^{{c - {{\varepsilon }_{1}}}} {\frac{1}{{x - c}}dx} + \int\limits_{{c + {{\varepsilon }_{2}}}}^{b} {\frac{1}{{x - c}}dx = \log \frac{{b - c}}{{c - a}} + \log \frac{{{{\varepsilon }_{1}}}}{{{{\varepsilon }_{2}}}}.} $$ (7.1.1)

The angiotensin AT2-receptor mediates inhibition of cell proliferation in coronary endothelial cells.

Abstract: Angiotensin II (ANG II) is known to be a potent growth promoting factor for vascular smooth muscle cells and fibroblasts but little is known about its influence on growth in endothelial cells. We studied the effects of ANG II on endothelial growth and the role of the angiotensin receptor subtypes involved. Proliferation of rat coronary endothelial cells (CEC) and rat vascular smooth muscle cells (VSMC) was determined by [3H]thymidine incorporation, the MTT-test and by directly counting cells in a coulter counter. Angiotensin AT1- and AT2-receptors were demonstrated by binding studies and by the presence of their respective mRNA through reverse transcription polymerase chain reaction (RT-PCR). In contrast to VSMC, which in culture only express the AT1-receptor, CEC express both, AT1- and AT2-receptors simultaneously up to the third passage. Whereas ANG II stimulated growth of quiescent VSMC, an effect abolished by pretreatment with the AT1-receptor antagonist, losartan, ANG II did not induce proliferation in quiescent CEC. However, after pretreatment of quiescent endothelial cells (< passage 4) with the AT2-receptor antagonist, PD 123177, ANG II induced proliferation. This effect was reversed by additional pretreatment with losartan. ANG II significantly inhibited the proliferation of bFGF-stimulated CEC in a dose-dependent manner by maximally 50%. This effect was prevented by PD 123177 while losartan was ineffective. The AT2-receptor agonist, CGP 42112, mimicked the antiproliferative actions of ANG II, confirming the specificity of the effect. Our results show that the growth modulating actions of ANG II depend on the type of angiotensin receptor present on a given cell. In coronary endothelial cells, the antiproliferative actions of the AT2-receptor offset the growth promoting effects mediated by the AT1-receptor.

Parameterizing eddy-induced tracer transports in ocean circulation models

Abstract: It is shown that the effects of mesoscale eddies on tracer transports can be parameterized in a large-scale model by additional advection and diffusion of tracers. Thus, tracers are advected by the effective transport velocity, which is the sum of the large-scale velocity and the eddy-induced transport velocity. The density and continuity equations are the familiar equations for adiabatic, Boussinesq, and incompressible flow with the effective transport velocity replacing the large-scale velocity. One of the main points of this paper is to show how simple the parameterization of Gent and McWilliams appears when interpreted in terms of the effective transport velocity. This was not done in their original 1990 paper. It is also shown that, with the Gent and McWilliams parameterization, potential vorticity in the planetary geostrophic model satisfies an equation close to that for tracers. The analogy of this parameterization with vertical mixing of momentum is then described. The effect of the Gent ...

Disease concomitance in psoriasis

Abstract: Background : Psoriasis is a multifactorial disease of unknown origin. Objective : Our purpose was to determine the frequency of skin disorders concomitantly seen in patients with psoriasis. Methods : We analyzed data from more than 40,000 patients and calculated sex- and age-adjusted ratios of expected and observed incidence rates of associated disorders. Results : The results demonstrate that, compared with age-matched control patients without psoriasis, cutaneous immune disorders such as allergic contact dermatitis, atopic dermatitis, and urticaria are underrepresented in patients with psoriasis. In contrast, certain systemic disorders such as diabetes, heart insufficiency, and obesity occur significantly more often in patients with psoriasis than in control subjects. Increased resistance to cutaneous bacterial infections was noted only in patients with early-onset psoriasis. Conclusion : Our observations show that a distinct pattern of associated diseases exists in patients with psoriasis. Although systemic disorders such as obesity, diabetes, and heart disease may be related to dietary habits and nutritional status, the relative resistance to cutaneous infections together with decreased immune responsiveness suggest a genetically determined selection.

Intramural Hemorrhage of the Thoracic Aorta Diagnostic and Therapeutic Implications

Abstract: Background Intramural hemorrhage (IMH) was recently identified at necropsy and anecdotally in vivo as a unique aortic syndrome (without entry and with no flap-like intraluminal component, such as overt aortic dissection). However, little is known about diagnosis, prognosis, and outcome of IMH. Methods and Results Between 1983 and 1993, 360 patients from two medical centers with clinical indications of aortic dissection were prospectively evaluated; they presented to the emergency department a median of 3.5 hours after onset of back or chest pain or other suggestive symptoms. Among 195 patients with aortic syndromes, 25 patients (12.8%) were diagnosed to have IMH of the thoracic aorta with no evidence of a primary intimal tear, flap, or overt dissection by multiple noninvasive imaging modalities, including magnetic resonance imaging (n=12), contrast-enhanced computed tomography (n=14), and transesophageal echocardiography (n=3) in random order. There were 16 men and 9 women with a median age of 56±13 years...

On the synthesis of strategies in infinite games

Abstract: Infinite two-person games are a natural framework for the study of reactive nonterminating programs. The effective construction of winning strategies in such games is an approach to the synthesis of reactive programs. We describe the automata theoretic setting of infinite games (given by “game graphs”), outline a new construction of winning strategies in finite-state games, and formulate some questions which arise for games over effectively presented infinite graphs.

Soil compaction processes and their effects on the structure of arable soils and the environment

Abstract: Soils are three-phase systems which undergo changes as soon as the external stresses exceed the internal soil strength, defined by the precompression stress value The three-dimensional stress propagation induces corresponding volumetric soil strain Soil compaction can result either in a higher bulk density or, when soil loading is attended with retarded water fluxes and high dynamic forces, in a completely homogenised soil characterised by a lower bulk density and a predominance of fine pores While in natural soils the structure can be described as macroscopically homogeneous, less careful mechanical treatment or reduced addition of organic substances results in less favourable types of soil aggregates As a result of applied external stresses, physical and chemical processes, such as mass flow and diffusion of water, ions and gases, are at least retarded or even completely altered Both increased bulk density and homogenisation cause decreased aeration and increased penetration resistance, which results in impeded root development Reduced water permeability may result in soil erosion, with serious negative effects on the environment Compacted soil may also contribute to global atmospheric warming due to increased emission of CO2, CH4 and N2O from such soils Anthropogenic changes in soil structure and soil functions remain constant for extended periods of time and efforts to restore deteriorated soil structure very often fail because of excessive loosening and homogenisation, cultivation of too wet soil or, afterwards, ill-adapted soil management practices, resulting in even worse soil properties The present paper gives a summary of relevant work performed by the authors

An international two-stage genome-wide search for schizophrenia susceptibility genes.

Abstract: Schizophrenia is thought to be a multifactorial disease with complex mode of inheritance. Using a two-stage strategy for another complex disorder, a number of putative IDDM-susceptibility genes have recently been mapped. We now report the results of a two-stage genome-wide search for genes conferring susceptibility to schizophrenia. In stage I, model-free linkage analyses of large pedigrees from Iceland, a geographical isolate, revealed 26 loci suggestive of linkage. In stage II, ten of these were followed-up in a second international collaborative study comprising families from Austria, Canada, Germany, Italy, Scotland, Sweden, Taiwan and the United States. Potential linkage findings of stage I on chromosomes 6p, 9 and 20 were observed again in the second sample. Furthermore, in a third sample from China, fine mapping of the 6p region by association studies also showed evidence for linkage or linkage disequilibrium. Combining our results with other recent findings revealed significant evidence for linkage to an area distal of the HLA region on chromosome 6p. However, in a fourth sample from Europe, the 6p fine mapping finding observed in the Chinese sample could not be replicated. Finally, evidence suggestive of locus heterogeneity and oligogenic transmission in schizophrenia was obtained.

Bacteria, fungi and the breakdown of leaf litter in a large river

Abstract: We examined the dynamics of leaf mass loss and microbial biomass associated with decomposing leaf litter in a seventh order river. This was in an attempt to test the hypothesis that fungal contribution to the breakdown process is less important in major rivers than was previously found for headwater streams. Bacterial biomass was estimated from direct cell counts coupled with determinations of bacterial biovolumes. Fungal biomass was estimated on the basis of ergosterol measurements, species-specific conversion factors, and the relative abundance of the dominant fungal species. Sporulation rates of aquatic hyphomycetes were determined by counting conidia released from leaf litter during brief laboratory incubations. Compared to low-order streams, the breakdown of willow, poplar and plane leaves was slow with exponential decay coefficients k ranging from 0.0045 to 0.0091 d-'. Numbers of bacteria first increased exponentially on all leaf species but reached a plateau of almost 108 cells per mg AFDM after 4-8 weeks of leaf submergence. This corresponds to a peak bacterial biomass of 0.3-0.5% of detrital carbon. Fungal biomass attained peaks of 5-10% of detrital carbon after 4-8 weeks and greatly exceeded bacterial biomass at any instance. On average, fungi accounted for 96% of the total microbial (fungal plus bacterial) biomass in leaf litter. Dynamics of sporulation rates of aquatic hyphomycetes were characterized by early peaks of 1.2-1.4 conidia µg-' AFDM d-', followed by sharp declines to about 0.2 µg-' d-'. Peaks occurred before the corresponding peaks in fungal biomass. Rough organic matter budgets suggest that fungi assimilated a minimum of 16-23% of the initial leaf carbon, and accounted for 42-65% of the overall carbon loss from leaves during periods of highest fungal activity. Taken together, these findings indicate that fungi play an eminently important role in the biological transformation of leaf litter even in major rivers. Bacterial contribution is likely to be small in spite of increases in biomass at advanced stages of breakdown. With regard to leaf decomposition, large fluvial systems would thus appear to behave like their headwater counterparts, suggesting that the present results can be generalized for lotic ecosystems.

308 tumor necrosis factor (TNF) polymorphism is not associated with survival in severe sepsis and is unrelated to lipopolysaccharide inducibility of the human TNF promoter.

Abstract: Tumor necrosis factor (TNF) is recognized as a central mediator of sepsis, septic shock, and multiple organ failure. These host reactions are associated with increased TNF levels in circulation, presumably due to increased TNF production. A previously described nucleotide variation at position -308 in the promoter region of the human TNF gene was shown to be associated with the clinical outcome of malaria. In this study we addressed the relevance of the -308 polymorphism for expression of the human TNF gene in response to bacterial endo- toxin in vivo and in vitro. First, we typed 80 patients suffering from severe sepsis and 153 healthy individuals and found no association of the -308 variation with incidence of the disease. In contrast, the NcoI marker in the closely linked lymphotoxin-alpha (LT-alpha) gene showed association with survivaL This discrepancy can be explained by the linkage of the TNFB2(NcoI) allele to the common TNF1 (-308) allele. Second, we generated reporter gene constructs with the promoter deletions and with both -308 variation in the context of the extended human TNF promoter region. Although such constructs were highly inducible by lipopolysaccharide (LPS) in transient transfections into a macrophage cell line, the -308 variation had no significant effect on transcription, consistent with the promoter deletion study. We conclude that the functional consequence of the -308 polymorphism may be unrelated to transcriptional response of the TNF gene to bacterial endotoxin.

Iceberg production, debris rafting, and the extent and thickness of Heinrich layers (H-1, H-2) in North Atlantic sediments

Abstract: The pattern of Heinrich-layer distribution for the last two events (H-1, ∼14.5 and H-2, ∼21.1 ka), mapped from magnetic susceptibility analysis of more than 50 North Atlantic Ocean cores, provides the most detailed information to date on their extent and thickness. An integrated spatial average thickness for the layers is 10–15 cm, and there is a strong distance decay eastward. The pattern of deposition over the North Atlantic is similar for events H-1 and H-2, indicating that icebergs followed similar drift tracks. Rates of iceberg production and sediment flux from the Hudson Strait drainage basin of the North American Laurentide ice sheet, the major iceberg source for the events, were calculated by using a mass-balance approach. This provides an envelope of sedimentation rates and the prediction that it would take between 50 and ∼1250 yr of iceberg sediment delivery to accumulate a Heinrich layer averaging 10 cm thick over the North Atlantic, depending on the model assumptions used. The most likely duration of Heinrich events is 250–1250 yr.

Biochemistry and Role of Sialic Acids

Abstract: Sialic acids mainly occur as terminal components of cell surface glycoproteins and glycolipids, playing as such a major role in the chemical and biological diversity of glycoconjugates. Cell-type-specific expression of glycosyltransferases, particularly of sialyltransferases (Paulson and Colley, 1989; van den Eijnden and Joziasse, 1993), leads to specific sialylation patterns of oligosaccharides which can be considered as key determinants in the makeup of cells. Striking differences have been found in the sialoglycosylation patterns of cells during development, activation, aging, and oncogenesis. Research on the structures, metabolism, and molecular biology, as well as on the biological and clinical importance of sialic acids as components of these glycoconjugates, has therefore intensified during the past several years.

The Role of Temperature Feedback in Stabilizing the Thermohaline Circulation

Abstract: Ocean climate models traditionally compute the surface heat flux with a restoring boundary condition of the form Q = λ(T* − To). This implies an atmosphere of fixed temperature and breaks down when large-scale changes in the ocean circulation are considered, which have a feedback effect on atmospheric temperatures. To include this important feedback, a new thermal boundary condition of the form Q = γ(T* − To) − μ∇2(T* − To) is proposed. This is derived from an atmospheric energy balance model with diffusive lateral heat transport. The effects of this new parameterization are examined in experiments with the GFDL modular ocean model for two model basins. “Conveyor belt” circulation states are compared using traditional mixed boundary conditions and our new coupling. With the new coupling, a realistic temperature contrast is obtained between the North Atlantic and the Pacific, caused by free adjustment of surface temperature to the oceanic heat transport. The results show that a temperature feedbac...

Evidence for a 2 Ga subduction zone: Eclogites in the Usagaran belt of Tanzania

Abstract: U-Pb geochronology on metamorphic minerals from a 35-km-long belt of eclogite-facies rocks in central Tanzania yields a Paleoproterozoic age of 2 Ga for the time of metamorphism. Peak metamorphic conditions found in eclogites (± kyanite) and metapelites reached about 750 °C and 18 kbar. A clockwise pressure-temperature path is deduced from mineral zonations, inclusion relations, and retrograde reaction textures. Near-isothermal decompression can be explained by erosion or tectonically controlled exhumation that followed tectonic thickening of the crust during subduction. Trace and rare earth element geochemistry indicates a mid-ocean ridge basaltlike mantle source for the precursors of the mafic members of the eclogite-facies rock suite. All the observations combined indicate that these high-pressure rocks are the oldest-known large-scale outcrops of eclogites formed during subduction of oceanic lithosphere. Linking eclogite formation to a Paleoproterozoic subduction event adds credibility to models of crust dynamics that advocate the operation of plate-tectonic processes early in Earth9s history. The paucity of Precambrian eclogites may then be addressed as a problem of preservation rather than lack of formation.

A constituent of the chloroplast import complex represents a new type of GTP-binding protein

Abstract: Summary The 34 kDa polypeptide of the outer envelope membranes from pea chloroplasts (OEP 34) is a major constituent of this membrane. OEP 34 is detected on polyacrylamide gels under non-reducing condition in association with OEP 75, the putative protein translocation pore. An antiserum against OEP 34 is able to co-immunoprecipitate the precursor of Rubisco small subunit from a partially purified import complex of chloroplast outer envelope membranes. A full-length cDNA clone coding for pea OEP 34 has been isolated. Analysis of the deduced amino acid sequence revealed typical and conserved sequence motifs found in GTP-binding proteins, making it a new and unique member of this superfamily. OEP 34 behaves as an integral constituent of the outer chloroplast envelope, which is anchored by its C-terminus into the membrane, while the majority of the protein projects into the cytoplasm. OEP 34 does not possess a cleavable N-terminal transit sequence but it is targeted to the chloroplasts and integrated into the outer membranes by internal sequence information which seems to be present in the C-terminal membrane anchor region. Productive integration of OEP 34 into the outer envelope requires, in contrast to other OEPs, protease-sensitive chloroplast surface components and is stimulated by ATR. The GTP binding specificity of OEP 34 is demonstrated by photo-affinity labelling in the presence of [α-32P]GTP. Overexpressed and purified OEP 34 possesses endogenous GTPase activity. These results indicate a possible regulatory function of OEP 34 in protein translocation into chloroplasts.

COSTEP - Comprehensive Suprathermal and Energetic Particle Analyser

Abstract: The COSTEP experiment on SOHO forms part of the CEPAC complex of instruments that will perform studies of the suprathermal and energetic particle populations of solar, interplanetary, and galactic origin. Specifically, the LION and EPHIN instruments are designed to use particle emissions from the Sun for several species (electrons, protons, and helium nuclei) in the energy range 44 keV/particle to > 53 MeV/n as tools to study critical problems in solar physics as well as fundamental problems in space plasma and astrophysics. Scientific goals are presented and a technical description is provided of the two sensors and the common data processing unit. Calibration results are presented which show the ability of LION to separate electrons from protons and the ability of EPHIN to obtain energy spectra and achieve isotope separation for light nuclei. A brief description of mission operations and data products is given.

The formation of disc galaxies in a cosmological context: structure and kinematics

Abstract: We present results concerning the internal structure and kinematics of disk galaxies formed in cosmologically motivated simulations. The calculations include dark matter, gas dynamics, radiative cooling, star formation, supernova feedback and metal enrichment. The initial model is a rigidly rotating overdense sphere with a mass of about 8 10^11 Msol which is perturbed by small scale fluctuations according to a biased CDM power spectrum. Converging, Jeans unstable and rapidly cooling regions are allowed to form stars. Via supernovae, metal enriched gas is returned to the interstellar medium. {}From these initial conditions a galaxy forms which shows the main properties of spiral galaxies: a rotationally supported exponential disk which consists of young stars with about solar metallicity, a slowly rotating halo of old metal poor stars, a bulge of old metal rich stars and a slowly rotating extended halo of dark matter. Bulge, stellar and dark halo are supported by an anisotropic velocity dispersion and have a de Vaucouleurs surface density profile. The flattening of the dark and stellar halo is too large to be explained by rotation only. Whether the flattening of the bulge is caused by an anisotropic velocity dispersion or by its rotation cannot be answered, because of the limited numerical resolution due to gravitational softening. The velocity dispersion and the thickness of the stellar disk increase with the age of the stars. Considering only the young stellar component, the disk is cold (sigma=20 km/sec) and thin (z <1 kpc). The dynamical formation process ends after about 4\,Gyr, when

Taxonomy and Physiology of Phototrophic Purple Bacteria and Green Sulfur Bacteria

Abstract: Anoxygenic phototrophic bacteria have always attracted scientists because of their coloration and ability to perform photosynthesis in the absence of air and without producing oxygen. Despite this common feature of these bacteria, variation in morphological, physiological and molecular properties, including molecular structures of the photosynthetic pigments and the photosynthetic apparatus, is great. This chapter will give a short introduction into the diversity of green sulfur and phototrophic purple bacteria, list some important properties of the species, and indicate important physiological features.

Boundary value problems for elliptic systems

Abstract: Part I. A Spectral Theory of Matrix Polynormials: 1. Matrix polynomials 2. Spectral triples for matrix polynomials 3. Monic matrix polynomials 4. Further results Part II. Manifolds and Vector Bundles: 5. Manifolds and vector bundles 6. Differential forms Part III. Pseudo-Differential Operators and Elliptic Boundary Value Problems: 7. Pseudo-differential operators on Rn 8. Pseudo-differential operators on a compact manifold 9. Elliptic systems on bounded domains in Rn Part IV. Reduction Of A Boundary Value Problem To An Elliptic System On The Boundary: 10. Understanding the L-condition 11. Applications to the index 12. BVPs for ordinary differential operators and the connection with spectral triples 13. Behaviour of a pseudo-differential operator near a boundary 14. The Main Theorem revisited Part V. An Index Formula For Elliptic Boundary Problems In The Plane: 15. Further results on the Lopatinskii Condition 16. The index in the plane 17. Elliptic systems with 2 x 2 real coefficients.

Environmental regulation and the location of polluting industries

Abstract: Does international tax competition in the environmental field lead to undesirably low levels of environmental regulation and to unacceptable disruptions of environmental quality? The paper tries to answer this question in a noncompetitive partial-equilibrium framework. There is one firm that wishes to establish a plant in one ofn countries. The paper shows that tax competition may lead to emission taxes that are either too low or too high. They may be so high that the investment is not undertaken, although this would be optimal if the countries cooperated. On the other end of the spectrum, a scenario in which taxes are driven to zero becomes possible if there are substantial transfrontier pollution effects.