Showing papers by "University of Jena published in 1996"

Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set.

Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.

Stochastic Geometry and Its Applications

Abstract: Mathematical Foundation. Point Processes I--The Poisson Point Process. Random Closed Sets I--The Boolean Model. Point Processes II--General Theory. Point Processes III--Construction of Models. Random Closed Sets II--The General Case. Random Measures. Random Processes of Geometrical Objects. Fibre and Surface Processes. Random Tessellations. Stereology. References. Indexes.

Function spaces, entropy numbers, differential operators

Abstract: 1. The abstract background 2. Function spaces 3. Entropy and approximation numbers of embeddings 4. Weighted function spaces and entropy numbers 5. Elliptic operators Bibliography.

Assessment of the safety and efficacy of the monoclonal anti-tumor necrosis factor antibody-fragment, MAK 195F, in patients with sepsis and septic shock: a multicenter, randomized, placebo-controlled, dose-ranging study.

Abstract: Objective To investigate the safety, biological effects, and efficacy of the anti-tumor necrosis factor (TNF) antibody fragment, MAK 195F, in a phase II trial in patients with severe sepsis.Design Prospective, randomized, open label, placebo-controlled, dose-ranging, multicenter, multinational clini

Molecular determinants for activation and inactivation of HERG, a human inward rectifier potassium channel.

Abstract: 1. The human eag-related potassium channel, HERG, gives rise to inwardly rectifying K+ currents when expressed in Xenopus oocytes. 2. The apparent inward rectification is caused by rapid inactivation. In extracellular Cs+ solutions, large outward currents can be recorded having an inactivation time constant at 0 mV of about 50 ms with an e-fold change every 37 mV. 3. HERG channel inactivation is not caused by an amino-terminal ball structure, as a deletion of the cytoplasmic amino terminus (HERG delta 2-373) did not eliminate inactivation. However, channel deactivation was accelerated about 12-fold at -80 mV. 4. Mutation of S631 to A, the homologous residue of eag channels, in the outer mouth of the HERG pore completely abolished channel inactivation. 5. Activity of HERG channels depended on extracellular cations, which are effective for channel activation, in the order Cs+ > K+ > > Li+ > Na+. The point mutation S631A strongly reduced this channel regulation. 6. By analogy to functional aspects of cloned voltage-gated potassium channels, rectification of HERG, as well as its kinetic properties during the course of an action potential, are presumably governed by a mechanism reminiscent of C-type inactivation.

Green-function approach to the radiation-field quantization for homogeneous and inhomogeneous Kramers-Kronig dielectrics

Abstract: A quantization scheme for the radiation field in dispersive and absorptive linear dielectrics is developed, which applies to both bulk material and multilayer dielectric structures. Starting from the phenomenological Maxwell equations, where the properties of the dielectric are described by a permittivity consistent with the Kramers-Kronig relations, an expansion of the field operators is performed that is based on the Green function of the classical Maxwell equations and preserves the equal-time canonical field commutation relations. In particular, in frequency intervals with approximately vanishing absorption the concept of quantization through mode expansion for dispersive dielectrics is recognized. The theory further reveals that weak absorption gives rise to space-dependent mode operators that spatially evolve according to quantum Langevin equations in the space domain. To illustrate the applicability of the theory to inhomogeneous structures, the quantization of the radiation field in a dispersive and absorptive one-interface dielectric is performed. \textcopyright{} 1996 The American Physical Society.

Magnetic properties of the znfe2o4 spinel

Abstract: Using neutron diffraction (ND), muon-spin rotation/relaxation ($\ensuremath{\mu}\mathrm{SR}$), and $^{57}\mathrm{Fe}$ and $^{67}\mathrm{Zn}$ M\"ossbauer spectroscopy (MS) we investigated magnetic properties of the normal spinel Zn${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$. Inversion is below limits of detection in samples which were slowly cooled from 1200 \ifmmode^\circ\else\textdegree\fi{}C to room temperature. Below ${T}_{N}=10.5$ K the spinel exhibits long-range antiferromagnetic order (LRO). However, already at temperatures of about $T\ensuremath{\approx}10{T}_{N}$ a short-range antiferromagnetic order (SRO) develops which extends through \ensuremath{\approx}70% of the sample volume just above ${T}_{N}$. Below ${T}_{N}$ antiferromagnetic SRO and LRO coexist. At 4.2 K still \ensuremath{\approx}20% of the sample are short-range ordered. The regions exhibiting SRO are very small (\ensuremath{\approx}3 nm). Their fluctuation rates as estimated from $\ensuremath{\mu}\mathrm{SR}$ are in the GHz range. For this reason the SRO above ${T}_{N}$ remains hidden in MS and is only seen in ND and $\ensuremath{\mu}\mathrm{SR}$ with their more appropriate time windows. Although the physical origin of the SRO remains an enigma, our experiments show that it is not caused by partial inversion but rather is an intrinsic property of Zn${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$. Modern ab initio cluster calculations successfully describe the magnetic hyperfine field as well as the electric field gradient tensor at the Fe site as seen by MS.

Discrete self-trapping, soliton interactions, and beam steering in nonlinear waveguide arrays.

Abstract: We investigate the self-trapping phenomenon in one-dimensional nonlinear waveguide arrays. We discuss various approximate analytical descriptions of the discrete self-trapped solutions. We analyze the packing, steering, and collision properties of these solutions, by means of a variational approach and soliton perturbation theory. We compare the analytical and numerical results. \textcopyright{} 1996 The American Physical Society.

Harmonic generation by femtosecond laser-solid interaction: A coherent "water-window" light source?

Abstract: The generation of harmonics by short, intense laser pulses reflected from a solid-density plasma is investigated using particle-in-cell simulation. High irradiance, obliquely incident p-polarized light generates harmonics via relativistic electrons dragged across the vacuum-solid interface. This mechanism does not exhibit the limitation previously predicted for lower intensities of a maximum harmonic ``cutoff'' ${n}_{\mathrm{max}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}{\ensuremath{\omega}}_{p}/{\ensuremath{\omega}}_{0}$. For $I{\ensuremath{\lambda}}^{2}g{10}^{19}\mathrm{W}{\mathrm{cm}}^{\ensuremath{-}2}\ensuremath{\mu}{\mathrm{m}}^{2}$ and modest shelf densities ${N}_{e}{/N}_{\mathrm{crit}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}10$, at least 60 harmonics can be generated with power efficiencies ${P}_{n}{/P}_{1}g{10}^{\ensuremath{-}6}$, suggesting coherent MW x rays with $\ensuremath{\lambda}\ensuremath{\sim}4\mathrm{nm}$ could be generated with a KrF $(248\mathrm{nm})$ pump.

Functional characterization of Kv channel beta-subunits from rat brain

Abstract: 1. The potassium channel beta-subunit from rat brain, Kv beta 1.1, is known to induce inactivation of the delayed rectifier channel Kv1.1 and Kv1.4 delta 1-110. 2. Kv beta 1.1 was co-expressed in Xenopus oocytes with various other potassium channel alpha-subunits. Kv beta 1.1 induced inactivation in members of the Kv1 subfamily with the exception of Kv 1.6; no inactivation of Kv 2.1, Kv 3.4 delta 2-28 and Kv4.1 channels could be observed. 3. The second member of the beta-subunit subfamily, Kv beta 2, had a shorter N-terminal end, accelerated inactivation of the A-type channel Kv 1.4, but did not induce inactivation when co-expressed with delayed rectifiers of the Kv1 channel family. 4. To test whether this subunit co-assembles with Kv alpha-subunits, the N-terminal inactivating domains of Kv beta 1.1 and Kv beta 3 were spliced to the N-terminus of Kv beta 2. The chimaeric beta-subunits (beta 1/ beta 2 and beta 3/ beta 2) induced fast inactivation of several Kv1 channels, indicating that Kv beta 2 associates with these alpha-subunits. No inactivation was induced in Kv 1.3, Kv 1.6, Kv2.1 and Kv3.4 delta 2-28 channels. 5. Kv beta 2 caused a voltage shift in the activation threshold of Kv1.5 of about -10 mV, indicating a putative physiological role. Kv beta 2 had a smaller effect on Kv 1.1 channels. 6. Kv beta 2 accelerated the activation time course of Kv1.5 but had no marked effect on channel deactivation.

Homogeneous synthesis of cellulose p‐toluenesulfonates in N,N‐dimethylacetamide/LiCl solvent system

Abstract: Pure cellulose p-toluenesulfonates (tosylates) with an insignificant formation of chlorodeoxy groups were prepared by reacting cellulose dissolved in a solution of N,N-dimethylacetamide and LiCI with tosylchloride (Tos-CI) in the presence of triethylamine within 24 h at 8°C. Various cellulosic starting materials with a degree of polymerization from 280 to 5 100 were used. The samples obtained were characterized by means of elemental analysis, FTIR and 13C NMR spectroscopy, and their intrinsic viscosities. The rise of the molar ratio of Tos-CI/anhydroglucose unit (AGU) from 0.6 to 9.0 leads to an increase in the degree of substitution (DS) from 0.4 up to a maximum value of 2.3. The cellulose tosylates are readily soluble in common organic solvents like dimethyl sulfoxide (within the whole DS range) and in N,N-dimethylacetamide, N,N-dimethylformamide, acetone, tetrahydrofuran and trichloromethane depending on DS. As revealed by 13C NMR spectroscopy a faster tosylation takes place at the O-6 atom of AGU compared with the O-2/3 atoms. This was additionally confirmed by analysis of the corresponding iododeoxy celluloses synthesized with NaI in acetylacetone. Furthermore, some important properties as stability against alkaline and heat were studied as well.

Silicon carbide: Synthesis and processing

Abstract: Silicon carbide with its outstanding physical properties is a material of choice for special optoelectronic and electronic devices working under extreme conditions. Synthesis as well as processing are complicated compared to other materials. The present paper summarizes some aspects of crystal growth and processing and discusses arising problems.

Endobronchial secretion of interleukin-13 following local allergen challenge in atopic asthma: relationship to interleukin-4 and eosinophil counts

Abstract: We investigated the secretion of interleukin (IL)-13 into the airways in 10 mild allergic asthmatics by employing local allergen challenge, and compared the data both to IL-4 levels and eosinophil numbers obtained by bronchoalveolar lavage (BAL). Appropriate allergen or saline were endoscopically instilled into different airway segments, which were lavaged 10 min and 18 h after allergen or sham challenge. IL-4 and IL-13 were measured in unconcentrated BAL fluid using a double sandwich enzymes-linked immunosorbent assay (ELISA). Endobronchial allergen challenge induced a highly significant increase in the numbers of eosinophils after 18 h in the allergen exposed segment. Ten minutes following allergen exposure, low levels of IL-4 and IL-13 could be detected, whilst concentrations of both cytokines were significantly raised 18 h following local allergen exposure. In contrast to IL-4, the concentration of IL-13 strongly correlated with the eosinophil numbers found 18 h post-allergen challenge. The results suggest that interleukin-13 is actively secreted during the late asthmatic response in mild asthmatic subjects. In view of its action on eosinophils and other cell types, we conclude that interleukin-13, in addition to interleukin-4, may play an important role in the pathogenesis of eosinophil-related inflammation, such as bronchial asthma.

Spectroscopic properties of Eu3+ and Tb3+ ions for local structure investigations of fluoride phosphate and phosphate glasses

Abstract: The relationships between glass structure and spectroscopic properties of the doped ions Eu3+ and Tb3+ are of interest. Eu3+ and Tb3+ ions are used as structure-sensitive ions. The Ω t - parameters of Eu3+ were determined from absorption and emission spectra. The lifetime of the 5D0 state of Eu3+ was calculated from Ω t and compared with the experimentally determined lifetime. The electron-phonon coupling strength and phonon energy were obtained from phonon sideband spectroscopy. The f → d absorption transition of Tb3+ was used for determination of the nephelauxetic parameter. With increasing phosphate content the covalency between rare earth ions and surrounding ligands increases due to substitution of fluoride ions by oxygen ions having higher electron polarizability. This effect leads to increasing nephelauxetic shift, Ω 2 - parameter and electron-phonon coupling strength. In fluoride phosphate glasses, the diphosphate groups dominate the spectroscopic properties of the rare earth ions.

The method of normalization to determine invariants

Abstract: The determination of invariant characteristics is an important problem in pattern recognition. Many invariants are known, which have been obtained either by normalization or by other methods. This paper shows that the method of normalization is much more general and allows one to derive a lot of sets of invariants from the second list as well. To this end, the normalization method is generalized and is presented in such a way that it is easy to apply, thus unifying and simplifying the determination of invariants. Furthermore, this paper discusses the advantages and disadvantages of the invariants obtained by normalization. Their main advantage is that the normalization process provides us with a standard position of the object. Because of the generality of the method, also new invariants are obtained such as normalized moments more stable than known ones, Legendre descriptors and Zernike descriptors to affine transformations, two-dimensional Fourier descriptors and affine moment invariants obtained by combining Hu's moment invariants and normalized moments.

Mutations affecting pigmentation and shape of the adult zebrafish

Abstract: Mutations causing a visible phenotype in the adult serve as valuable visible genetic markers in multicellular genetic model organisms such as Drosophila melanogaster, Caenorhabditis elegans and Arabidopsis thaliana. In a large scale screen for mutations affecting early development of the zebrafish, we identified a number of mutations that are homozygous viable or semiviable. Here we describe viable mutations which produce visible phenotypes in the adult fish. These predominantly affect the fins and pigmentation, but also the eyes and body length of the adult. A number of dominant mutations caused visible phenotypes in the adult fish. Mutations in three genes, long fin, another long fin and wanda affected fin formation in the adult. Four mutations were found to cause a dominant reduction of the overall body length in the adult. The adult pigment pattern was found to be changed by dominant mutations in wanda, asterix, obelix, leopard, salz and pfeffer. Among the recessive mutations producing visible phenotypes in the homozygous adult, a group of mutations that failed to produce melanin was assayed for tyrosinase activity. Mutations in sandy produced embryos that failed to express tyrosinase activity. These are potentially useful for using tyrosinase as a marker for the generation of transgenic lines of zebrafish.

Depolymerization of low-rank coal by extracellular fungal enzyme systems.

Abstract: A miniscale screening system was developed to detect depolymerizing activities of fungi toward low-rank coals. This system was suitable for the determination of changes in molecular masses as well as for the measurement of the enzymes responsible. A total of 486 fungal strains of different ecophysiological and taxonomic groups were tested for their ability to decolorize agar media containing coal-derived humic acids; 38 wood- and litter-decaying basidiomycetes caused a strong bleaching effect and 49 a weak effect. In contrast, micromycetes were proved to be unable to decolorize the coal substances. The wood-decaying fungus Nematoloma frowardii b19 most effectively bleached the medium. It could be demonstrated by gel-permeation chromatography that the strain really depolymerizes the high molecular-mass fractions of coal humic acids by forming fulvic-acid-like compounds. Extracellular enzyme activities of oxidases and peroxidases towards 2,2′-azinobis(3-ethylbenzthiazolinesulphonate) were extractable from the agar media.

Molecular variants of fibronectin and laminin: structure, physiological occurrence and histopathological aspects

Abstract: This review deals with biological and pathological aspects of various isoforms of the matrix molecules fibronectin and laminin. They are generated by different molecular mechanisms: ED-A+ and ED-B+ fibronectin by alternative splicing of pre mRNA, de novo-glycosylated fibronectin by alternative post-translational O-linked glycosylation of the IIICS region, and the laminin isoforms by exchange of single chains of the heterotrimeric molecule. In contrast to the “common” fibronectin, the distribution of ED-B+ and de novo-glycosylated fibronectin is restricted to embryonic tissues; they subsequently reappear in granulation tissue, in fibrosing processes and in tumour stroma. The expression of these so-called oncofetal fibronectins is stimulated by growth factors (TGFβ). The association of the ED-B+ fibronectin with proliferative activity and newly formed vessels identifies this fibronectin variant as a marker of cellular activity in the process of fibrosis and as a suitable agent for the evaluation of tumour angioneogenesis. Initial results suggest a correlation between the amount of ED-B+ and de novo-glycosylated fibronectin in tumour stroma and the behaviour of carcinomas with regard to their invasiveness and propensity for metastatic dissemination. The current nomenclature of the laminin molecule family is presented. The laminin chain constitution of basement membranes switches from embryonic or proliferatively active to adult terminally differentiated tissues [disappearance of the laminin β2 (s) chain] and depends on the tissue type. The discrepancy between the loss of basement membranes (multiple basement membrane defects) in carcinomas and the recently reported increased laminin chain synthesis in these tumours may be explained by abundant laminin chain deposition outside the basement membrane in the carcinoma invasion front, possibly associated with enhanced adhesion of budding tumour cells.

Distribution of Dip-allatostatin I-like immunoreactivity in the brain of the locust Schistocerca gregaria with detailed analysis of immunostaining in the central complex.

Abstract: The distribution and morphology of neurons containing allatostatin-related substances in the brain of the locust Schistocerca gregaria was investigated using an antiserum against Diploptera punctata allatostatin I (Dip-allatostatin I, APSGAQRLYGFGL-amide). In each brain hemisphere, about 550 neurons in the midbrain and 500 neurons in the optic lobe exhibit Dip-allatostatin I-like immunoreactivity, including about eight lateral neurosecretory cells with processes to the retrocerebral complex. All major brain areas except the antennal lobe, the mushroom body, and large parts of the lamina, are innervated by Dip-allatostatin I-immunoreactive processes. Immunostaining in the central complex was studied in detail. The central complex is innervated by more than 260 Dip-allatostatin I-immunoreactive neurons belonging to six different cell types, four sets of tangential neurons and two sets of columnar neurons. These neurons give rise to intense immunostaining in the protocerebral bridge, in several layers of the upper division of the central body, and in the dorsalmost layer of the lower division of the central body. Double-label experiments show colocalization of Dip-allatostatin I- and serotonin-like immunoreactivities in one type of columnar and one type of tangential neurons of the central complex. The similar patterns of Dip-allatostatin I- and galanin message-associated peptide-like immunoreactivities result from cross-reactivity of the anti-galanin message-associated peptide antiserum with Dip-allatostatin I. The results provide further insight into the anatomical and neurochemical organization of the locust central complex and suggest a prominent neuroactive role for Dip-allatostatin I-related peptides in this brain area.

Quantitative determination of hirudin in blood and body fluids

Abstract: Recent clinical studies using hirudin as anticoagulant have demonstrated that an efficient method to determine the current blood level of hirudin is imperative for exact dose finding and adjustment Only the exact determination of the hirudin content in blood, performed within a few minutes, prevents overdosage involving side effects or, otherwise, a subtherapeutic dose regimen Therefore, a method for rapid, sensitive, and reproducible measurement of hirudin in blood, plasma, and other body fluids has been developed The method, which is based on coagulation measurement, is called ecarin clotting time (ECT) In this test, ecarin, a purified enzyme of the Echis carinatus snake venom, acts as a prothrombin activator In contrast to the "solid phase" prothrombin activation by prothrombinase, the ecarin-induced prothrombin activation proceeds in an alternative way, ie, without the need of cofactors, resulting in intermediates such as meizothrombin Compared to thrombin, meizothrombin has a lower procoagulant activity, but it still binds hirudin, which leads to the inhibition of meizothrombin Depending on the sample's concentration of hirudin, ecarin forms a residual, nonhirudin-bound amount of intermediates of the prothrombin-thrombin conversion that are able to concentration-dependently convert fibrinogen to fibrin There is an excellent linear correlation between ECT prolongation and the hirudin content of the sample in a range from 50 to 5,000 ng/mL blood or plasma This allows immediate measurement not only of the therapeutic blood level of hirudin, but also of its concentration in blood following under- or overdosage The ECT method is nearly independent of variations in the sample's content of fibrinogen (from 60% to 100%) and prothrombin (from 20% to 100%) Heparin is not able to catalyze the very low antithrombin inhibition of meizothrombin Therefore, it is also possible to determine hirudin in blood containing varying amounts of heparin Another advantage of the method is that it can be applied to different mechanical measuring systems used in coagulation diagnostics

Molecular characterization of group A streptococcal (GAS) oligopeptide permease (Opp) and its effect on cysteine protease production

Abstract: Bacterial oligopeptide permeases are membrane-associated complexes of five proteins belonging to the ABC-transporter family, which have been found to be involved in obtaining nutrients, cell-wall metabolism, competence, and adherence to host cells. A lambda library of the strain CS101 group A streptococcal (GAS) genome was used to sequence 10,192 bp containing the five genes oppA to oppF of the GAS opp operon. The deduced amino acid sequences exhibited 50-84% homology to pneumococcal AmiA to AmiF sequences. The operon organization of the five genes was confirmed by transcriptional analysis and an additional shorter oppA transcript was detected. Insertional inactivation was used to create serotype M49 strains which did not express either the oppA gene or the ATPase genes, oppD and oppF. The mutation in oppA confirmed that the additional shorter oppA transcript originated from the opp operon and was probably due to an intra-operon transcription terminator site located downstream of oppA. While growth kinetics, binding of serum proteins, and attachment to eukaryotic cells were unaffected, the oppD/F mutants showed reduced production of the cysteine protease, SpeB, and a change in the pattern of secreted proteins. Thus, the GAS opp operon appears to contribute to both protease production and export/processing of secreted proteins.

Photophysiology of turion formation and germination inSpirodela polyrhiza

Abstract: Standardized laboratory techniques for the vegetative growth of the duckweedSpirodela polyrhiza (Lemnaceae), and for formation as well as germination of their turions were described. Increasing photon fluence rates of blue or red light increased the yield of turions. A specific stimulating effect of blue light was demonstrated under autotrophic but not under mixotrophic conditions. Therefore the spectral composition of light is not important in mixotrophic formation of turions whereas in autotrophic formation light sources with a higher portion of blue light are recommended. Dark-grown (etiolated) turions showed accelerated germination and higher germination percentage in comparison with light-grown turions after induction by a single red light pulse. This difference was overcome in continuous red light by speeding up the germination response of light-grown turions. Use of Petri dishes (8 cm3 nutrient solution) instead of Erlenmeyer flasks (50 cm3 nutrient solution) retarded germination response. Especially for long term experiments the use of Erlenmeyer flasks is recommended. Storage of turions for 72 h at 25 ‡C following at 5 ‡C in darkness after-ripening resulted in a decreased lag phase of the light-induced germination both after induction by a single light pulse and in continuous light.

Structure of crystalline phosphates from P-31 double-quantum NMR spectroscopy

Abstract: 31P multiple-quantum solid-state NMR spectroscopy is introduced as a new approach for elucidating internuclear distances between phosphorus nuclei in phosphates. The typical shorter distance between chemically bound groups allows the determination of the chemical network. The method is superior to 31P exchange experiments, which, in principle, provide similar information. Separation of two crystalline Mg2P2O7 phases is observed by both methods, but the double-quantum experiment gives further information of couplings between sites with equal isotropic chemical shifts. In Ca2P6Ol7, which contains Q2 and Q3 groups with large chemical shift anisotropies, the connectivities can be deduced from the double-quantum experiment due to different cross-peak intensities. Our results are in good agreement with X-ray diffraction measurements and suggest applications to other, more complicated phosphates.