Showing papers by "University of Jena published in 1985"

Electron–Phonon Interaction in Dielectric Bilayer Systems. Effect of the Electronic Polarizability

Abstract: A quantum-mechanical theory of the electron–(long-wave optical) phonon interaction in dielectric bilayer systems is developed. The operator describing the interaction between an electron and the phonon modes of the bilayer system is calculated including the electronic polarizability. All polarization eigenmodes together with their dispersion relation are derived and discussed. The dispersion curves of the surface phonons are calculated and presented for various cases in graphical form. The interaction of electrons outside and inside the bilayer system is studied and the coupling functions are calculated and discussed and they are shown in graphical form. Es wird eine quantenmechanische Theorie der Elektron–(langwellig-optischen) Phonon-Wechselwirkung in dielektrischen Doppelschichtsystemen entwickelt. Dabei wird der Einflus der elektronischen Polarisierbarkeit auf die Struktur des Hamilton-Operators der Wechselwirkung der Elektronen mit den Phononen berucksichtigt. Es werden alle Polarisationseigenmoden und die dazu gehorenden Dispersionsrelationen abgeleitet und diskutiert. Die Dispersionskurven der Oberflachen-Phononen werden fur verschiedene Falle berechnet und graphisch dargestellt. Die Wechselwirkung von Elektronen, welche sich innerhalb und auserhalb des Doppelschichtsystems befinden, wird untersucht und die Kopplungsfunktionen werden fur verschiedene Falle berechnet und graphisch dargestellt.

Interface reactions between machinable bioactive glass‐ceramics and bone

Abstract: A new biomaterial for bone substitution, a "machinable bioactive glass-ceramic" has been developed. The material contains two main crystal phases, mica and apatite, and is therefore machinable and bioactive. It has the advantage to be workable by the surgeon, if necessary, during operation. The preparation method of this glass-ceramic is described. Different types of the material can be produced in dependence of the composition, nucleation, and crystallization of the basic glass. In vivo and in vitro investigations showed a characteristic solubility of the material. A Ca-phosphate-rich interface layer with apatite crystals (from the basic glass-ceramic) and a thickness of about 5-10 micrometers grows as solid-state reaction between glass-ceramic and bone. This interface reaction is interpreted as a chemical process which includes a slight solubility of the glass-ceramic and a solid state reaction between the stable apatite crystals in the glass-ceramic and the bone.

On the Boolean closure of NP

Abstract: By endowing usual nondeterministic Turing machines with new modes of acceptance we introduce new machines whose computational power is bounded by that of alternating Turing machines making only one alternation. The polynomial time classes of these machines are exactly the levels of the Boolean closure of NP which can be defined in a natural way. For all these classes natural problems can be found which are proved to be ≤ m P -complete in these classes.

On solutions of one-dimensional stochastic differential equations without drift

Abstract: We consider the stochastic differential equation dX t =b(X t )dW t , t≧0, where b is a real-valued (universally) measurable function and W is a Wiener process. In the previous paper [8] the authors have shown that a nontrivial weak solution of this equation exists for all initial distributions if and only if b−2 is locally integrable. However, the uniqueness in law fails in general. In the present paper we give a complete description of all solutions by construction from a so-called fundamental solution. The fundamental solution has no sojourn time in the zeros of b and the general solution can be obtained from it by time delay in the zeros of b. Furthermore, some properties of solutions are investigated. Thus we characterize the set of all strong Markov solutions and a certain class of Markov solutions. We construct examples of Markov solutions which are not strong Markov. Finally, we study the representation property of solutions. In the Appendix, a few results on the time change of arbitrary strong Markov continuous local martingales and perfect additive functionals of them are collected. The basic method of the paper consists in a systematic use of random time change.

Nonlinear guided waves in saturable nonlinear media.

Abstract: The behavior of nonlinear waves guided by a film configuration with a nonlinear cladding is investigated. The intensity-dependent dielectric function of the cladding is characterized by saturation effects. The field patterns that arise are discussed, and the dispersion relations are derived. Several dispersion curves are plotted. The results are compared with those familiar from nonlinear guided-wave propagation along configurations with Kerr-like cladding dielectric functions.

Nature and significance of microbial cometabolism of xenobiotics

Abstract: Microbial cometabolism, i.e. "transformation of a non-growth substrate in the obligate presence of a growth substrate or another transformable compound" (Dalton and Stirling 1982) is a whole-cell phenomenon physiologically based on coupling of different catabolic pathways at the cellular level. It is frequently observed in transformation of xenobiotic non-growth substrates by individual microbial species. Transformation processes of this type are usually mediated by appropriate non-specific enzymes of the peripheric cellular metabolism able to modify a variety of substances other than their natural substrates. The precise mechanisms of coupling between metabolism of xenobiotic non-growth substrates and of particular additional carbon substrates may be different depending on the substrates and the microbial species involved. However, experimental data indicate that the primary function of the respective additional carbon substrates is to supply either energy, cofactors or metabolites for the different cellular events involved in the transformation process (e.g. uptake of the xenobiotic non-growth substrate, functioning of appropriate degradative enzymes of the peripheric cellular metabolism). Cometabolism of xenobiotics involves nothing special or novel from the standpoint of biochemistry. On the contrary, there are numerous examples where the turnover of particular natural compounds by certain aerobic or anaerobic microorganisms is essentially based on coupling of different catabolic pathways at the cellular level by transfer of hydrogen (i.e. reducing power) and/or energy between two or more enzymatic reactions. Synthetic chemicals which resist total degradation by individual microbial species may undergo mineralization due to complementary catabolic sequences mediated by certain multispecies microbial associations with cometabolic transformations being the initial steps. Although taking place in certain natural habitats (e.g. rhizospheres, sewage), microbial cometabolism of xenobiotics in natural ecosystems occurs with slow rates since the respective cometabolizing populations are generally small and will not increase in number or biomass in response to the introduced chemicals. However, under conditions of axenic microbial cultures, high concentrations of biomass, and appropriate substrate mixtures cometabolism of synthetic chemicals may be a useful technique of considerable practical importance to accumulate biochemical products at high yields. In addition, cometabolic capabilities of wild-type microorganisms may serve as a tool for the construction of microbial strains with a new degradative potential for recalcitrant xenobiotic compounds.

The international collaborative study establishing the first international standard for timothy (Phleum pratense) grass pollen allergenic extract

Abstract: A selected candidate international reference preparation of timothy grass (Phleum pratense)-pollen extract was studied together with two other freeze-dried timothy pollen allergenic extracts in a multinational study. The collaborators used RAST inhibition, histamine release, quantitative immunoelectrophoresis (crossed immunoelectrophoresis/crossed radioimmunoelectrophoresis and rockets), isoelectric focusing, and other methods. The total allergenic potencies measured in RAST inhibition were evaluated for validity of linearity and parallel-line response. The relative concentrations of some important individual allergenic components were measured. The relative potencies for the total allergenic activity and the timothy components studied in each preparation were expressed relative to the selected candidate. This preparation was established in 1983 by the World Health Organization expert committee on biologic standardization as the international standard for timothy grass pollen extracts with assigned units of 100,000 IU per ampule.

Analysis of a mode-locked ring laser: chirped-solitary-pulse solutions

Abstract: We present measurements on mode-locked ring dye lasers that demonstrate the role of self-phase modulation in the saturable absorber dye. The resulting bandwidth increase plays an essential role in ultrashort pulse generation, because it leads to intracavity pulse compression in the presence of normally dispersive components. The role of various intracavity components (glass, coatings) in intracavity compression is analyzed. As opposed to extracavity compression, measurements of pulse amplitude and phase show that the nonlinear phase modulation can be completely compensated. The interaction of the light pulse with the absorber is analyzed using Maxwell–Bloch equations. Next, we find the steady-state solution for the problem of pulse propagation through an infinite periodic medium containing all the essential intracavity elements (bandwidth-limiting filter, amplifier, absorber, dispersive component). The condition that the solitary pulses be unchirped enables us to determine the optimum intracavity dispersion, which, in agreement with the experimental data, leads to the shortest pulses.

Glass formation and properties of chalcogenide systems XXXII. RDF studies on the structure of vitreous Ge2S3 and Ge2Se3

Abstract: Studies on the structure of the bulk glasses GeS2 with the aid of X-ray diffraction measurements and RDF calculations are reported which are supported by pair function calculations based on a wire model constructed by hand which has been approximated in three steps in order to guarantee the isotropy criteria and the experimental density preferentially taking into consideration the bond parameters of the high temperature modification of crystalline GeS2. Because of the comparatively sufficient accordance between the model RDF and the experimental RDF up to the third peak and with respect to the peak positions even up to the fifth maximum the glass structure can be approached by a three-dimensional connected network of GeS 4 2 units, about one fourth of which are edge shared with a GeSGe angle distribution of 85–145° and a maximum at about 115°. The RDF of vitreous GeSe2 is discussed in comparison with GeS2.

Compression of picosecond pulses from a solid-state laser using self-phase modulation in graded-index fibers.

Abstract: We report the compression by a factor of 7 of 2-μJ pulses of 5-psec duration from a mode-locked Nd:phosphate glass laser. The pulses were chirped and their spectrum broadened while traveling through a graded-index core fiber. After amplification to 500 μJ, they were finally compressed by traveling through a dispersive delay line, and 0.7-psec pulse widths were achieved.

The distribution of a proctolin-like immunoreactive material in the terminal ganglion of the cockroach, Periplaneta americana L.

Abstract: Neurons with proctolin-like immunoreactivity were mapped in the terminal ganglion of Periplaneta americana. The effect of different fixation methods on the variability of immunostaining is described and discussed. The appearance of immunoreactive presynaptic terminals, described here for the first time in insects, points to a function of proctolin as neurotransmitter or neuromodulator in the central nervous system of P. americana besides its known role in the periphery. Proctolin-like immunoreactivity was shown in pre- and postsynaptic profiles. Synaptic contacts are described in detail.

Redox reactions in condensed oxide systems: III. Glass formation and properties in the Bi2O3P2O5 system

Abstract: Glass formation in the system (Bi2O3)x(P2O5)1−x is reported by application of a pre-reaction technique on Bi2O3/H3PO4 mixtures of a mole ratio of 1:6 followed by evaporation and calcination yielding amorphous Bi3P7O22 as a starting material which can be reproducibly transformed into a light glass Bi2P4O13 at 1000°C or into a dark brown glass Bi4(P2O7)3 at 1200°C by melting without any action on Pt. Holding the former for some time at 1200°C before casting results in a black brown glass, and the latter yields a nearly colourless glass at 1000°C in both cases without changing the composition. It is found that the reversible variation of the absorption spectrum is caused by a very small liberation of oxygen from the melt at the higher temperature or by entrance of air at the lower temperature, respectively. The properties of the glasses are compared. Some tenths up to some per cents of Bi in a lower oxidation state are formed depending on the temperature. Light scattering measurements indicate the formation of clusters in the dark kinds of glasses.

Detection of two ornithine carbamoyltransferases in a phaseolotoxin-producing strain of Pseudomonas syringae pv. phaseolicola

Abstract: The phaseolotoxin-producing Pseudomonas syringae pv. phaseolicola strain 1321 contains two ornithine carbamoyltransferases which differ in resistance to phaseolotoxin. Whereas ornithine carbamoyltransferase 1 (OCT 1) is inhibited at low concentrations of phaseolotoxin, ornithine carbamoyltransferase 2 (OCT 2) is insensitive to phaseolotoxin. The activity of the insensitive enzyme is correlated with the amount of toxin formed.

Freeze-fracture observations of Corynebacterium glutamicum: the occurrence of an outer membrane-like structure and the influence of temperature on the cytoplasmic membrane

Abstract: In order to elucidate temperature-dependent morphological changes in the cell envelope of the Gram-positive L-lysine-overproducing Corynebacterium glutamicum 9366 we carried out freeze-fracture investigations of native cells and studied their fatty acid composition. In addition to the cytoplasmic membrane C. glutamicum possesses at the periphery of the cell an additional fracture plane which is unusual in Gram-positive bacteria and is designated here as outer membrane-like structure. The fracture faces of this layer display a distinguishable appearance in several regions of the cell. Bacteria grown at various temperatures showed changes in the relation of the saturated to unsaturated fatty acids. We demonstrated that the cytoplasmic membrane was affected by these changes in the fatty acid composition.

Redox reactions in condensed oxide systems II. Variation of the structure of vanadium phosphate glasses in dependence on the oxidation state of vanadium

Abstract: The glass formation range in the systems V2O5VO2P2O5 and VO2V2O3P2O5 has been determined by melting V2O5 or VO2 together with P4O10 or utilizing H3PO4, respectively, in the series (VzOz/2)1−x(PO2.5)x with 0.2 < x < 0.8 in air taking care to realize equilibrium conditions.v Glass transition temperature, chemical durability and conductivity measurements indicate two distinct ranges which are discussed in terms of a structural model. The values are compared with data from the literature.

Laser Induced Defects in GaAs Layers

Abstract: Annealing of ion implanted GaAs layers as well as irradiation of unimplanted samples with nanosecond laser pulses is connected with the formation of exponential absorption tails near the fundamental absorption edge with the dependence K ˜ exp [ħω(E)−1] on the photon energy. Identical behaviour is found in weakly damaged ion implanted layers. The observed high near edge absorption is connected with almost no refractive index change. The characteristic energy E is independent on the implanted ion species and increases with the nuclear deposited energy density and the laser energy density from about ≈ 0.1 eV up to a maximum value of 0.52 eV. The defects responsible for this behaviour act as compensating centers for free carriers. The experimental findings and the missing pronounced absorption tail in irradiated silicon supports the conclusion that defects typical for compound semiconductors are produced. Assuming high concentrations of vacancies and anti-site defects the experimentally found values for E can be explained from theoretical calculations. Die Ausheilung von ionenimplantierten GaAs-Schichten und die Bestrahlung nicht implantierten Materials mit Nanosekunden-Laserimpulsen fuhrt zur Ausbildung exponentieller Auslaufer des Absorptionskoeffizienten nahe der Bandkante der Form K ˜ exp [ħω(E)−1]. Identisches Verhalten wird auch in schwach geschadigten implantierten Schichten nachgewiesen, die erhohte Absorption ist mit keiner merklichen BrechzahlvergrosBerung verbunden. Die charakteristische Energie E ist unabhangig von der Art der implantierten Ionen und wachst mit der nuklear deponierten Energiedichte und der Laserenergiedichte von 0,1 eV bis zu einem Sattigungswert von 0,52 eV. Die fur dieses Verhalten verantwortlichen Defekte fuhren zur Kompensation der n-Leitung. Aus den experimentellen Befunden und unter Berucksichtigung der Tatsache, das in Si derart ausgepragte Auslaufer des Absorptionskoeffizienten nahe der Bandkante nicht beobachtet werden, wird auf die Bildung von fur Verbindungshalbleiter typischen Eigendefekten geschlossen. Unter der Annahme hoher Vakanzen- und anti site-Defektkonzentrationen konnen die experimentell gefundenen Werte fur E theoretisch erklart werden.

Phenomenological theory of explosive solid phase crystallization of amorphous silicon

Abstract: Considering the crystallization in amorphous semiconducting material as a phase transition of first kind a model of a lateral spreading out crystallization process is developed, which takes into account the feed back of the released latent heat to the kinetics of nucleation and growth of crystallites. Deciding between solid and liquid phase crystallization a classification of explosive crystallization phenomena will be given. Model calculations are carried out for lateral moving explosive fronts of solid-phase epitaxy and solid-phase nucleation. From the dependence of the velocity of the front on the substrate temperature derived in the case of stationarity it becomes evident, that the explosive solid-phase epitaxy should be impossible in silicon and the explosive solid-phase nucleation can initiate explosive liquid-phase processes. Indem man die Kristallisation in amorphem Halbleitermaterial als einen Phasenubergang erster Art betrachtet, wird ein Modell eines sich lateral ausbreitenden Kristallisationsprozesses entwickelt, welches die Ruckkopplung der freigesetzten latenten Warme auf die Kinetik der Keimbildung und des Kristallitwachstums berucksichtigt. Indem man zwischen Fest- und Flussigphasenkristallisation unterscheidet, wird eine Klassifikation der explosiven Kristallisationsphanomene moglich. Fur sich lateral bewegende Explosivfronten der Festphasenepitaxie und der Festphasennukleation werden Modellrechnungen durchgefuhrt. Aus der unter der Bedingung der Stationaritat abgeleiteten Abhangigkeit der Frontgeschwindigkeit von der Substrattemperatur wird deutlich, das die explosive Festphasenepitaxie in Si unmoglich sein sollte und die explosive Festphasennukleation explosive Flussigphasenprozesse zunden kann.

Effect of neonatal sympathectomy by 6-hydroxydopamine on renal hemodynamic parameters in adult rats

Abstract: Summary Newborn rats were sympathectomized with 6-hydroxydopamine (6-OHDA) (10 mg/ 100 g b.w., once daily on the first 4 postnatal days). Hemodynamic parameters were determined at the 55th d of life. In comparison to non-sympathectomized control rats the blood pressure and total peripheral resistance of 6-OHDA treated animals were significantly diminished whereas the cardiac output was enhanced. In sympathectomized rats the resistance values of the whole kidney as well as of the cortex and outer medulla were lower than in control animals. No redistribution of renal blood flow was detectable. The results show a long lasting effect of neonatal denervation by 6-OHDA at least up to the 55th d of life.

Diffusion and recrystallization processes during annealing of N+‐ and P+‐implanted LiNbO3

Abstract: The stability of ion irradiation induced defects and refractive index changes in LiNbO3, is examined in the temperature region 300 K ≦ TA ≦ 1370 K using the results of RBS, volume expansion, and reflection measurements. Due to the destruction of the crystal structure the activation energy of the Li2O-diffusion in RBS-amorphous layers is reduced to (0.62 ±; 0.07) eV. Thereby at temperatures TA > 700 K a mixed phase of LiNbO3 and LiNb3O8, can be formed. The restoration of the LiNbO3 crystal structure takes place in connection with the equalization of the Li2O-concentration by diffusion from the substrate into the layer during annealing at TA = 1370 K. Die Stbilitat der durch Ionenimplantation in LiNbO3 erzeugten Defekte und Brechzahlanderun-gen wird im Temperaturbereich 300 K ≦ TA ≦ 1370 K mit RBS-, Volumendilatations- und Reflexionsmessungen untersucht. Infolge der Zerstorung der Kristallstruktur ist die Aktivierungs-energie fur die Li2O-Diffusion in den RBS-amorphen Schichten auf (0,62 ± 0,07) eV herabgesetzt. Dadurch kann sich bei Temperaturen TA > 700 K eine Mischphase von LiNbO3 und LiNb3O8 bilden. Die Wiederherstellung der LiNbO3-Struktur erfolgt im Zusammenhang mit dem Ausgleich der Li2O-Konzentration durch Diffusion vom Sabstrat in die Schicht wahrend einer Temperung bei 1370 K.

Biochemical and substructural studies on hepatic and serum lipoprotein metabolism after acute liver injury induced by thioacetamide in rats

Abstract: The effect of an acute liver injury induced by thioacetamide (TAA) on hepatic and serum lipoprotein metabolism in rats was studied using biochemical and ultrastructural methods. A single dose of 100 mg TAA/kg body weight caused within 48 h a decrease of hepatic triglyceride (TG) output into the serum by about 50% in comparison to the controls. The steady state of serum TG concentration from 24 to 96 h after TAA treatment implies that the clearance of TG from serum must be diminished to the same extent as the hepatic TG output was found to decrease. Moreover, the TAA treatment caused changes in the electrophoretic mobility as well as in the concentration and composition of circulating serum-lipoproteins. The electrophoresis revealed a decrease in the alpha-band, which can be explained by the decrease in the high density lipoproteins (HDL) total lipid concentration. The pre-beta-migrating band disappeared, whereas a broad beta-mobility band appeared, which most likely consists of a mixture of very low density lipoproteins (VLDL) and low density lipoproteins (LDL) as can be concluded from the changes in concentration and composition of lipids in both fractions. For a better visualization of the VLDL-forming capability in perilobular and centrolobular liver parenchymal cells of the TAA-treated animals the VLDL secretion blocking agent colchicine was used. It was shown that in comparison with colchicine-treated controls the VLDL secretory products are accumulated at a considerably lower rate manifested in a diminution of VLDL clusters, secretory vesicle size and the number of intravesicular VLDL particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of the dispersion relations of nonlinear slab-guided waves

Abstract: The dispersion relations of TE-polarized nonlinear guided waves (NGW) were investigated in detail. These waves travel along a dielectric slab embedded between two different nonlinear media. A simple relation between the effective nonlinear dielectric constants was established. All dispersion curves exhibit a particular transition point, where one evanescent field maximum changes from a virtual into a real one, and vice versa. Depending on the type of the remaining invariant evanescent field maximum, all NGW's split into two families. The lowest-order membres of every family play a particular role. The power flux supported by a NGW is derived, too.