Showing papers by "University of Jena published in 1986"

Development of machineable bioactive glass ceramics for medical uses

Abstract: Following a controlled, two-stage phase separation in glasses of the system Na2O/K2OMgOAl2O3SiO2CaOP2O5F, annealing results in both fluorophlogopite and apetite crystallization. The phlogopite mica crystals make the material machineable, whereas the apatite crystals provide for its bioactivity. Animal tests show direct intergrowth with the bone. Bone cells and blood vessels can be found in the immediate neighbourhood of the implant.

Mapping properties of non-linear operators in spaces of Triebel--Lizorkin and Besov type

Abstract: Исследуются свойств а отображений некото рых классов нелинейных оператор ов в прост ранствах типа Бесова и Трибеля — Лизоркина. Для вещественно-значных функций G выводятся условия необходимые для того, чтобы опреде ляемый ими нелинейный операторG: f→ →G(f) осуществлял ограни ченное отображение пространств типаВp,qs(Rn) илиFp,qs(Rn).

Dynamical Screening, Collective Excitations, and Electron–Phonon Interaction in Heterostructures and Semiconductor Quantum Wells. General Theory

Abstract: A theory of dynamical screening in heterostructures and semiconductor quantum wells is developed which contains electron–electron interaction and electron–phonon interaction. In this theory both the types of long-wave optical phonons, LO phonons and interface phonons, which occur in those layered structures are included. An expression is derived for the longitudinal screened interaction of subband electrons in heterostructures and quantum-wells. The obtained screened interaction potential allows the derivation of the total longitudinal dielectric function and the dispersion relation of the coupled intra- and intersubband plasmon-phonon modes. This screened interaction potential is used to develope a dynamically screened and finite-temperature theory of the electron–phonon interaction in heterostructures and quantum wells. The leading-order electron self-energy is disscussed. An analytic expression of the polarization function of the quasi-two-dimensional electron gas is calculated within the random-phase approximation. Further approximations, the plasmon pole approximation and the long-wave approximation are discussed and the resulting analytic expressions of the polarization function are given. Es wird eine Theorie der dynamischen Abschirmung in Heterostrukturen und Quanten-Wells entwickelt. Die dynamische Abschirmung beinhaltet sowohl die Elektron–Elektron- als auch die Elektron–Phonon-Wechselwirkung, wobei in letzterer die zwei Typen von langwellig-optischen Phononen (LO Phononen und Grenzflachen-Phononen), die in solchen schichtformigen Strukturen auftreten, explizit berucksichtigt werden. Das longitudinal abgeschirmte Wechselwirkungs-potential der Subband-Elektronen in Heterostrukturen und Quanten-Wells wird berechnet. Ausgehend von diesem Potential wird ein Ausdruck fur die totale longitudinale dielektrische Funktion und fur die Dispersionsrelation der gekoppelten Intra- und Intersubband-Plasmon–Phonon-Moden abgeleitet. Weiterhin wird aus diesem Potential eine Theorie der dynamisch abgeschirmten Elektron–Phonon-Wechselwirkung bei eindlichen Temperaturen in Heterostrukturen und Quanten-Wells abgeleitet. Die aus dieser Wechselwirkung resultierende Selbstenergie der Elektronen wird diskutiert. Es wird ein analytischer Ausdruck fur die Polarisationsfunktion des quasi-zweidimensionalen Elektronengases in der Random-Phase Approximation abgeleitet. Weitere Naherungen, die Plasmon-Pol-Naherung werden diskutiert und analytische Ausdrucke fur die Polarisationsfunktion abgeleitet.

Studies on lipid and lipoprotein metabolism in rat liver cirrhosis induced by different regimens of thioacetamide administration.

Abstract: Summary In female Wistar rats the animal model of TAA-induced liver cirrhosis has been tested for reliability and usefulness for studies on lipid and lipoprotein metabolism in cirrhosis From our results we draw the following conclusions: 1 Application of 300 mg TAA/1 drinking water from the 4th to the 6th month of life leads in all treated rats to liver cirrhosis which is rather uniformly of micronodular surface morphology Under this treatment the survival rate is about 90 percent 2 Increasing the administered dose (450 and 600 mg/1) and/or extension of TAA administration time (4 or more months) leads to decreasing survival rates, and to a shift from micronodular towards macronodular cirrhosis 3 To produce macronodular cirrhosis it is suggested to extent the application time rather than to increase the dose since in the latter case the survival rate is very low 4 The alterations of lipid and lipoprotein metabolism observed in this animal model, ie decrease of pre-β-lipoproteins, increase of β-lipoproteins, decrease of serum triglyceride concentration and decrease of hepatic VLDL-TG output into the serum are in good agreement with those observed in human cirrhosis Thus, the TAA-induced chronic liver injury proved to be a reliable and useful model for studies on lipid and lipoprotein metabolis in liver cirrhosis

Propagation phenomena of nonlinear film-guided waves: a numerical analysis.

Abstract: The propagation of TE guided waves excited at different points of their dispersion curve has been numerically traced down a thin film bounded by two identical self-focusing media. Several types of nonstationary field evolution have been investigated and identified as transitions between or oscillations around different branches of the dispersion curve.

Relation between renal and hepatic excretion of drugs: I. Phenol red in comparison with p-aminohippurate and indocyanine green

Abstract: Phenol red is a suitable compound for the simultaneous assay of renal and hepatic excretion in the rat. Its elimination has been compared with those of p-aminohippurate (PAH) and indocyanine green (ICG) which are eliminated nearly exclusively via kidneys or liver, respectively. The interruption of one elimination route one day before the experiment, that means bile duct ligation (DL) in the case of ICG or bilateral nephrectomy (NX) in the case of PAH are followed by a slight increase in the elimination via the alternative pathway, but no effective compensation occurs. On the other hand, the renal excretion of phenol red is significantly increased after DL only following administration of high doses. This intensification is caused by an increase in the unbound amount of phenol red depending on the plasma concentration and reflects an enhanced glomerular filtration fraction. The biliary excretion increases significantly after NX, but only after infusion of low doses. The maximal biliary secretion capacity cannot be exceeded following NX, either. The competitive inhibition of phenol red excretion by probenecid supports the findings of NX or DL experiments. An influence of the three test substances on arterial blood pressure has been excluded. The most important factors influencing the switch over from one to the other elimination route seem to be at least in the case of phenol red the amount of unbound substance, the influence of the administered dose on the glomerular filtration, and disturbances in the volume of distribution, e.g. the possible reduction of hepatic uptake after DL.

Curvature measures and random sets II

Abstract: In choosing models of stochastic geometry three general problems play a role which are closely connected with each other: In the present paper second order local geometric properties of random subsets of R d are of interest. These properties are described by signed curvature measures in a measure geometric context. The theory of point processes on general spaces (here on the space of subsets with positive reach) provides an appropriate framework for solving construction and measurability problems. Mean value relations for random curvature measures associated with such set processes are derived by means of invariance properties. Ergodic interpretations of the curvature densities are also given. The appendix provides auxiliary results for random signed Radon measures in locally compact separable Hausdorff spaces.

Virulence properties of escherichia coli strains in patients with chronic pyelonephritis

Abstract: In 50Escherichia coli strains obtained from the bladder puncture urine of patients with chronic pyelonephritis, determinations of virulence properties were performed. All of theE. coli strains isolated from 26 acute episodes of pyelonephritis were found in the smooth form. 30% possessed K 1 antigen, 77% showed the ability to form hemolysin and 30% produced colicin V (aerobactin). Fimbriae (detected by mannose-resistant hemagglutination) were registered in 81%, and plasmids ranging between 50 and 70 Md were demonstrated in 70% of the bacteria. In contrast to this, only 70% of theE. coli strains isolated from 24 patients at an inactive stage of pyelonephritis were found in the smooth form; 10% of these encoded K 1 antigen, 20% hemolysin and 10% colicin V. Plasmids in the range 50 to 70 Md could be found in 30%. On the basis of multivariate analysis of variance and discriminant analysis, it was confirmed that uropathogenic strains possess several virulence properties, mannose-resistant hemagglutination being of particular importance.

Quantum noise in spectral filtering of light

Abstract: The quantum-theoretical description of the action of a spectral filter is given. It is shown that spectral filtering of light is unavoidably connected with quantum noise, which prevents the spectrometer from performing a Fourier analysis even under ideal conditions. The quantum noise is important in the study of spectral properties of nonclassical light fields, such as spectral squeezing in single-atom resonance fluorescence.

Explosive crystallization processes in silicon

Abstract: This paper deals with selfsustaining crystallization processes, the so-called explosive crystallization, in silicon produced by short temperature pulses. By this, crystalline Si layers can be generated on amorphous substrates, e.g. on SiO2, at which liquid and solid-state crystallization processes can take place.

Radiation effects in optoelectronic materials

Abstract: Ion irradiation can be used to modify the physical properties of optoelectronic materials in well defined regions and consequently, to produce integrated circuits in surface layers. In most cases, the change of physical properties such as the refractive index, the absorption coefficient, the density and the conductivity are strongly influenced by the radiation damage which is caused by the ion implantation process. So, the study of the generation, transformation and annealing of radiation defects as their connection with the physical properties of the materials is very important. A review of the effect of radiation damage on the properties of essential optoelectronic materials as SiO2 and LiNbO3 will be given in this paper. It deals mainly with the mechanism of defect generation, the annealing of defects by thermal treatment and the optical properties of materials affected with defects. The main results are: There exists a uniform dependence of the primary damage (i.e. without essential defect tr...

Relation between renal and hepatic excretion of drugs: II. Age-dependence of phenol red excretion in comparison with those of p-aminohippurate and indocyanine green

Abstract: The excretory functions of kidney and liver do not develop simultaneously during the maturation of an individual Therefore age related differences in the relation between renal and hepatic drug excretion could be expected In this study the excretion of p-aminohippurate (PAH) and indocyanine green (ICG) as model substances for nearly exclusive excretion via kidney or liver, respectively, have been compared with that of phenol red eliminated both via kidneys and liver (3:1) Experiments were performed on rats between the 10th and 105th days of life For PAH and ICG the typical age courses of renal or hepatic excretion have been confirmed Both urinary and biliary phenol red excretion show an influence of age, however, renal elimination reaches adult values as early as at the 20th day of life Furthermore the age relation concerning compensation of the loss of kidney or liver excretory functions has been studied Neither after nephrectomy (NX) nor after bile duct ligation (DL) the PAH or ICG elimination via the alternative pathway, respectively, were quantitatively increased Thus a compensation of the interruption of the main elimination route does not occur in all ages In contrast, phenol red excretion into urine and bile increases distinctly after DL or NX This increase becomes even significant after administration of suitable doses of phenol red saturating transport capacities of liver or kidney The compensation is first of all caused by passive pharmacokinetic changes Active compensatory mechanisms have not been proved

Near‐Edge Optical Absorption Behaviour in Weakly Damaged Ion‐Implanted GaAs

Abstract: The long exponential absorption tail near the fundamental absorption edge occuring in weakly damaged ion implanted GaAs is investigated in dependence on the ion species (N+, Ar+, Zn+, and Cd+ ions are used) and on the ion fluence. The results show that characteristic native defects are responsible for the observed absorption behaviour. The near edge absorption coefficient as well as the characteristic tailing energy increase with the energy density deposited in nuclear processes and reach both a maximum value for a critical energy density. From the optical measurements and considering the results of temperature dependent RBS measurements conclusions are made concerning the nature of defects in the weakly damaged GaAs layers. Der exponentielle Absorptionsauslaufer im Bereich der Fundamentalabsorptionskante schwach geschadigter ionenimplantierter GaAs-Schichten wird in Abhangigkeit von der Art der implantierten Ionen (N+, Ar+, Zn+, Cd+) und von der Ionendosis untersucht. Die Ergebnisse zeigen, das das beobachtete Absorptionsverhalten im bandkantennahen Bereich durch charakteristische Eigendefekte verursacht wird. Sowohl der Absorptionskoeffizient als auch die mit dem Anstieg des Absorptionslausaufers verknupfte charakteristische Energie nehmen mit wachsender nuklear deponierter Energiedichte zu und erreichen Maximalwerte fur eine kritische Energiedichte. Aus den Ergebnissen der optischen Messungen und unter Berucksichtigung von Resultaten temperaturabhangiger RBS-Messungen werden Schlusfolgerungen bezuglich der Natur der Defekte in schwach geschadigten GaAs-Schichten gezogen.

Phenomenological Theory of Explosive Solid Phase Crystallization of Amorphous Silicon. II. Dynamical Processes

Abstract: The autocatalytic or “explosive” solid-phase crystallization is due to the feed back of the liberated latent heat to the kinetics of the phase transition. The dynamics of the explosive solid-phase nucleation (ESPN) is studied by use of a model containing phenomenologically the coupling between matter and energy transport in crystallizing amorphous layers of silicon on insulators. The effect of lateral moving explosive crystallization fronts (wave front solution) discussed in part I of this paper is investigated by solving the coupled reaction-diffusion equations numerically. The evolution of the wave fronts (ignition and dying out) is discussed in dependence on the conditions of the initial temperature distribution, the heat losses and the competitive nucleation processes in the layer. Optimum conditions of ignition and spreading are found. Die autokatalytische oder „explosive” Festphasenkristallisation ist zuruckzufuhren auf die Ruckkopplung freigesetzter latenter Warme des Phasenubergangs auf dessen Kinetik. Die Dynamik der explosiven Festphasennukleation (ESPN) wird unter Verwendung eines Modells, das die Kopplung zwischen Masse- und Energietransport in kristallisierenden amorphen Siliziumschichten phanomenologisch enthalt, untersucht. Der Effekt sich lateral ausbreitender explosiver Kristalli-sationsfronten, der im Teil I dieser Arbeit erortert wurde, erfahrt eine voll zeitabhangige Behandlung durch numerische Losung der gekoppelten Reaktions-Diffusionsgleichungen. Die Entwicklung der Wellenfronten (Zundung und Verloschen) wird in Abhangigkeit von den Bedingungen der Anfangstemperaturverteilung, den Warmeverlusten und der Konkurrenznukleation in der Schicht diskutiert. Optimale Zund- und Ausbreitungsbedingungen werden gefunden.

Picosecond study of energy transfer. Deviations from Förster theory — evidence for an inhomogeneous spatial distribution of molecules

Abstract: We have investigated long-range dipole—dipole energy transfer between several laser dyes in solution. Time-resolved absorption and fluorescence experiments on a picosecond excite-and-probe-beam spectrometer and a single-photon counting equipment have been carried out to measure the excitation depletion of the donor (Rh 6G) and the rise of the excitation of the acceptors (DOTC, cresylviolet, oxazine) as a function of the acceptor concentration. An unexpected very rapid and effective energy transfer has been been found, even at very low acceptor concentrations. Forster radii R0 have been determined for each dye combination. At high acceptor concentrations these R0 values agree well with those calculated from spectra data, but rather large deviations have been found at low acceptor concentrations. The observed deviations from the common Forster law are tentatively explained in terms of a modified Forster model which takes into account an inhomogeneous distribution of molecules in solution.

RBS and optical investigations of defects in weakly damaged GaAs

Abstract: Weakly damaged GaAs layers were investigated by optical transmission and reflection measurements and the Rutherford backscattering (RBS) channeling technique. The samples show characteristic near edge optical properties which are caused by high concentrations of point defects. The analysis of the temperature dependence of the RBS minimum yield points at the existence of slightly displaced lattice atoms with concentrations ≳ 50 at.%. The results suggest, in agreement with those of the optical measurements, that vacancies, antisite defects and/or complexes are responsible for the high concentration of slightly displaced atoms.

Rigidly rotationg perfect fluids

Abstract: A class of stationary rigidly rotating perfect fluids in General Relativity is investigated. This class which is characterized by zero Simon tensor contains only the Wahlquist solution and its limits. It is shown how a recently given solution follows from the Wahlquist solution by a limiting procedure. Eine Klasse stationarer, starr rotierender idealer Flussigkeiten in der Allgemeinen Relativitatstheorie wird untersucht. Diese Klasse, die durch verschwindenden Simon-Tensor gekennzeichnet ist, enthalt nur die Wahlquist-Losung und ihre Limites. Es wird gezeigt, wie eine kurzlich angegebene Losung aus der Wahlquist-Losung durch eine Limesbildung hervorgeht.

Nondeterministic turing machines with modified acceptance

Abstract: The complexity classification of problems defined by restricting NP-complets problems to those instances having unique solutions requires still finer hierarchies within BC(NP) (the Boolean closure of NP) than that introduced in [Wec 85] (see also [WeWa 85], [GuWe 85], [CaHe 85] and [KoSc 85]) which will be called the Hausdorff hierarchy generated by NP. In this paper an extremely fine hierarchy within BC(NP) is proposed. The classes of this hierarchy are characterized by nondeter-ministic polynomial time Turing machines with suitably modified acceptance notions (Section 2). Complete sets for the classes of the hierarchy are presented in Section 5. The hierarchy is studied under relativizations (Sections 3 and 5). Section 4 yields more insight in the structure of the hierarchy.

On the na+ self-diffusion and electrical conductivity of Na2O-B2O3-SiO2 glasses derived from the Na2O·2SiO2 glass

Abstract: Five borosilicate glasses, whose composition is deduced from that of the disilicate glass (Na 2 O·2SiO 2 ). are investigated for hydrolytic durability and for Na + transport properties. The motion of the Na + ions is studied by measurements of the 22 Na tracer-diffusion coefficients D * and of the electrical conductivity σ in dependence on temperature. The deduced activation parameters ( E A.D , D 0 : E A.σ , σ 0 ) and the Haven ratio H R = D * / D n are discussed in relation to Na + concentration and to structural features of the glasses. The results are compared with the behaviour of binary sodium silicate glasses with related Na + concentrations.

Correlation between protein data in normal lumbar CSF and morphological findings of choroid plexus epithelium: a biochemical corroboration of barrier transport via tight junction pores

Abstract: Specific "reference areas" were derived from relationships between the proteins prealbumin, albumin, alpha 1-acid glycoprotein, alpha 2-macroglobulin, total transferrin, IgG, IgA, IgM, and the corresponding total protein in normal lumbar CSF samples. The procedure for calculating the boundary lines of these reference areas was carried out on the basis of double standard deviations in subgroups with total protein differences of 50 ml/l within the whole range of 150-400 ml/l CSF. The resulting biochemical data, hydrodynamic radii of the individual proteins investigated, and van Deurs' and Koehler's morphological findings on the existence of pores in the barrier-forming tight junctions of the choroid plexus epithelium could be surprisingly well correlated with one another, although these morphological findings were obtained in choroid plexus of the rat brain. The correlation allowed the conclusion that proteins undergo ultrafiltration via a pattern of tight junction pores with various diameters. However, the molecular mechanism seems to include an additional facilitating component.