Showing papers by "University of Jena published in 1989"

Rational points of bounded height on Fano varieties

Abstract: a prime pe7Z. Let V be an algebraic variety defined over F and lI~ a metrized line bundle on V, i.e., a system (L, ]'],) consisting of a line bundle L and a family of Banach v-adic metrics on L | F,, for all v's satisfying well-known conditions (cf. [1], Chap. VI). Then we can define a height function hL: X ( F ) ~ I R by the formula h~(x)= ~ Is(x)[[ 1, where s is a local section of L non-vanishing

The Boolean hierarchy II: applications

Abstract: The Boolean Hierarchy I: Structural Properties [J. Cai et al., SIAM J. Comput ., 17 (1988), pp. 1232–252] explores the structure of the boolean hierarchy, the closure of NP with respect to boolean ...

Phaseolotoxin production by Pseudomonas syringae pv. phaseolicola: The influence of temperature

Abstract: Phaseolotoxin (N-sulphodiaminophosphinyl-ornithyl-alanyl-homoarginine) is a phytotoxic secondary metabolite produced by Pseudomonas syringae pv. phaseolicola. The production of the phytotoxin is strongly regulated by temperature. The optimal temperature for phaseolotoxin production is 18 °C. Temperatures in the range between 18 °C and 30 °C inhibit the production of phaseolotoxin in an increasing manner. By temperature shift experiments and the inhibition of protein synthesis by chloramphenicol it was demonstrated, that the synthesis of enzymes related to toxin synthesis and not the regulation of the activity of the responsible enzyme system is affected by higher temperatures.

Osteoarthritis and bone: osteologic types of osteoarthritis of the hip.

Abstract: To assess prognosis and indications for allografting articular surfaces, osteological examination is of increasing importance. In this study 93 femoral heads of patients with primary osteoarthritis could be differentiated into three osteologic types using histomorphometry: (1) the osteosclerotic type (77% of cases), (2) the hyperostotic type, with excessive neogenesis of bone all over the femoral head and increased formation of osteophytes (10% of cases), and (3) the osteopenic type, with decreased bone mass and features of bone remodelling, a greater occurrence of subchondral cysts, and small osteophytes (8% of cases). Radiological and clinical features to distinguish these groups are given. The consequences for pathogenesis and clinical practice are discussed.

Coronatine production by Pseudomonas syringae pathovars: Screening method and capacity of product formation†

Abstract: The hypertrophy of potato tuber tissue caused by coronatine could be developed into a semiquantitative screening method. A correlation between coronatine concentration and hypertrophy was demonstrated. 53 strains of P. syringae pv. glycinea and 9 strains of P. syringae pv. tomato were tested for coronatine production using this method. 24 of the investigated Pseudomonas syringae pv. glycinea strains failed to produce detectable amounts of coronatine. The remaining 29 produced coronatine in various quantities. The yields of these strains differed in orders of magnitude. The strains of P. syringae pv. tomato showed an analogous behaviour. It is assumed that coronatine is a virulence factor, which is of importance for the severing of plant diseases, implicated in the establishment of the bacteria in the plant tissue.

Glutathione synthesis and export in experimental liver cirrhosis induced by thioacetamide: relations to ultrastructural changes.

Abstract: Micro-and macronodular experimental liver cirrhosis was induced in female rats by administration of 0.03% thioacetamide (TAA) in drinking water for 3 or 6 months, respectively. The glutathione (GSH) status (content, synthesis, export) and ultrastructural changes of liver were investigated 14 d after withdrawal of TAA. The hepatic level of GSH was increased after 6 months TAA treatment. The levels of oxidized glutathione (GSSG) were not changed after 3 months or 6 months TAA administration. The GSH synthesis was not disturbed in the cirrhotic livers; only the ratio between the 2 synthesizing enzymes was changed in macronodular liver cirrhosis. The plasma GSH content was reduced in both cases, independent of the stage of liver cirrhosis. The electron microscopic studies on cirrhotic rat livers revealed a series of characteristic structural changes, such as disorganization and total lack of the microvilli border, appearance of basement membrane-like deposits within the narrowed space of Disse, disappearance of the highly porous endothelial cell lining and partly an intensively detoriated blood supply within the pseudolobules. It is suggested that all these changes may contribute to a disturbance of the GSH export from the hepatocytes into the blood. It is very likely, however, that the alterations of the sinusoidal cell surface play the most important role. 1. The GSH/GSSG redox potential is shifted in favour of the reduced form in this cirrhosis model. This shift seems to be connected with later stages of cirrhogenesis. 2. A GSH export disturbance is responsible for the decreased plasma GSH level in liver cirrhosis.

Neuropeptides--occurrence and functions in insects.

Abstract: Article de synthese sur les neuropeptides (de mammiferes et d'invertebres) identifies chez les insectes

Distribution of GABA-like immunoreactive neurons in the optic lobes of Periplaneta americana

Abstract: Specific antisera against protein-conjugated γ-aminobutyric acid (GABA) were used in immunocytochemical staining procedures to study the distribution of the putative GABA-like immunoreactive neurons in the optic lobes of Periplaneta GABA-like immunoreactive structures are evident in all three optic neuropil regions Six different populations of GABAergic neurons, whose perikarya are grouped around the medulla, are found within the optic lobe The number of these immunoreactive cells varies greatly and corresponds to the number of ommatidia of the eye In the proximal part of the lamina, a coarse network of GABA-positive fibres is recognizable These are the processes of large field tangential cells whose fibres pass through the distal surface of the medulla A second fibre population of the lamina is made up of the processes of the centrifugal columnar neurons whose perikarya lie proximally to the medulla The medulla contains 9 layers with GABAergic elements of variable immunoreactivity Layers 1, 3, 5, 7 and 9 exhibit strong labelling, as a result of partial overlapping of the processes of centrifugal and centripetal columnar neurons, tangential fibres and/or lateral processes of perpendicular fibres and (possibly) processes of amacrines A strong immunoreactivity is found in the proximal and distal layers of the lobula

Relationship of Microscopic and Macroscopic Theories for Long‐Wavelength Optical Phonons in GaAs‐AlAs Superlattices

Abstract: A critical comparison is made of the lattice-vibrational properties resulting within the macroscopic continuum model and a closely parallel microscopic force-constant model. The elastic and electric forces are treated in the same manner. However, the atomic structure of matter and the bulk phonon dispersion are neglected in the continuum approach. For that reason it cannot explain the optical frequency spectrum of a superlattice even not in the long-wavelength limit. On the other hand, the principal line shape of the atomic displacement patterns for optical phonons can be satisfactorily described by envelopes, at least, if the arbitrariness inherent any theory neglecting dispersion is utilized in an appropriate way. This holds particularly for modes which are not accompanied by long-range electric fields. For the other modes — the p-polarized symmetrical phonons propagating not parallel to the superlattice axis — the problem of identification appears additionally since the interface character restricted to four modes in the dispersionless continuum approach is distributed among all symmetrical phonons within the microscopic theory. Es wird ein kritischer Vergleich der Gitterschwingingseigenschaften, wie sie aus dem makrosko-pischen Kontinuumsmodell bzw. einem parallelen mikroskopischen Kraftkonstantenmodell resultieren, durchgefuhrt. Die elastischen und elektrischen Krafte werden gleich behandelt, die Dispersion der Volumenphononen aber in der Kontinuumsnaherung vernachlassigt. Deswegen kann diese auch nicht im langwelligen Grenzfall das optische Phononenspektrum eines Supergitters erklaren. Andererseits kann im Rahmen der Kontinuumsapproximation die Linienform der atomaren Auslenkungen in befriedigender Weise durch Einhullende beschrieben werden, zumindestens wenn mit der Unbestimmtheit, die jeder dispersionsfreien Theorie inharent ist, geeignet umgegangon wird. Diese Aussage gilt besonders fur die Moden, die nicht von langreichweitigen elektrischen Feldern begleitet werden. fur die anderen Moden — die p-polarisierten symmetrischen Phononen, die sich nicht parallel zur Supergitterachse ausbreiten — taucht zusatzlich das Problem der wechselseitigen Identifizierung auf, da der Grenzflachencharakter, der in der dispersionsfreien Kontinuumsnaherung auf vier Moden beschrankt ist, in der mikroskopischen Theorie auf alle symmetrischen Phononen verteilt wird.

Theory of Duality in Mathematical Programming

Abstract: Contents: Convex sets and convex functions.- Theory of duality.- Dual problems of optimization.- Literature.- Notation Index.- Subject Index.

Defects in Weakly Damaged Ion‐Implanted GaAs and Other III–V Semiconductors

Abstract: Under definite implantation conditions (small ion masses, sufficiently small ion fluences, and high implantation temperature) in III–V compounds weakly damaged layers are produced, which exhibit characteristic properties near the optical edge and an only slight increase of dechanneling of backscattered light ions. Especially for GaAs, InP, and GaP an exponential dependence of the near edge absorption coefficient on the photon energy according to K ∼ exp (ħω/E1) with E1 = 0.52 eV for GaAs, 0.33 eV for InP, and 0.6 eV for GaP is observed. From theoretical considerations it is concluded that this behaviour is connected with the existence of high concentrations of complexes containing antisite defects and vacancies. Combining optical measurements with TEM and measurements of the temperature dependence of the dechanneling gives further information about the structure of weakly damaged GaAs layers. The results of a complex analysis of weakly damaged GaAs and other III–V compound layers and first ideas about the damage structure in such layers are discussed. In III–V-Verbindungshalbleitern entstehen unter bestimmten Implantationsbedingungen (niedrige Ionenmassen, hinreichend niedrige Ionendosis und hohe Implantationstemperatur) schwach geschadigte Schichten, die charakteristische optische Eigenschaften im Bereich der Bandkante aufweisen und zu einer nur geringen Erhohung der Dekanalisierung ruckgestreuter leichter Ionen fuhren. Insbesondere findet man in GaAs, InP und GaP im Bereich der Bandkante eine exponentielle Anhangigkeit des Absorptionskoeffizienten von der Photonenenergie entsprechend K ∼ ∼ exp (ħω/E1) mit E1 = 0,52 eV fur GaAs, 0,33 eV fur InP und 0,6 eV fur GaP. Aus theoretischen Untersuchungen kann gefolgert werden, das dieses Verhalten mit der Existenz einer hohen Konzentration von Defektkomplexen verbunden ist, die Antisite-Defekte und Vakanzen enthalten. Erganzende Untersuchungen mittels TEM und zur Temperaturabhangigkeit der Dekanalisierung liefern weitere Informationen uber die Struktur der schwach geschadigten GaAs-Schichten. Es werden die Ergebnisse einer komplexen Analyse schwach geschadigter GaAs- und anderer III—V-Halbleiterschichten und erste Vorstellungen uber die Struktur der Defekte in diesen Schichten diskutiert.

Investigation of defects in weakly damaged ion implanted GaAs layers

Abstract: From the analysis of the near edge optical properties it has previously been concluded that weakly damaged ion implanted GaAs layers contain high concentrations of point defect complexes consisting preferably of vacancies and anti-site defects. The investigation of the temperature dependence of the dechanneling of light ions provides further information about the structure of such layers. With this method it was shown that, in room temperature nitrogen implanted GaAs, slightly and heavily displaced atoms exist with mean values of the displacement distance r a = 0.018 nm and r a = 0.065 nm from the atomic strings, respectively. The concentrations of the two defect types varies with the ion fluence. The results indicate that defect annealing and recombination during room temperature implantation of GaAs produces a resulting damage structure consisting of point defect complexes which contain vacancies and anti-site defects. As the implant fluence is increased the formation of further defects (interstitials also) becomes probable.

Robuste Statistik in der analytischen Chemie

Abstract: The fundamentals of robust statistics are explained in their importance for analytical chemistry Robust statistical techniques are resistant against uncertainties concerning the data, like outliers or divergencies from the normal distribution The efficiency of several medians and robust confidence intervals is demonstrated by means of examples The bases of robust regression are described and the advantages of its use are shown for practically relevant examples

Measurement of X‐ray diffraction angles of perfect monocrystals with high accuracy using a single crystal diffractometer

Abstract: The aberrations and with that the systematic corrections for a single crystal diffractometer measurement according to the BOND method are derived from one general expression in a closed analytic way. Thus, all possible effects are included and calculated correctly. In comparison with the hitherto existing seperate derivation of aberrations it appears that the results of already known aberrations change in some cases and new aberrations appear. On this basis it is possible to measure lattice parameters as well as wavelengths with accuracies in the order of 10−7d and 10−7λ, respectively, on a BOND diffractometer. Es werden Aberrationen und damit die systematischen Korrekturen fur eine Einkristall-Diffraktometer-Messung nach der BOND-Methode von einem allgemeinen Ausdruck in einer geschlossenen analytischen Weise hergeleitet. Damit konnen alle moglichen Effekte erfast und korrekt berechnet werden. Ein Vergleich mit der bisherigen separaten Herleitung der einzelnen Aberrationen zeigt, das sich bei den schon bekannten Aberrationen in einigen Fallen die Ergebnisse andern und das neue Aberrationen erscheinen. Auf dieser Grundlage ist es moglich, mit einem BOND-Diffraktometer sowohl Gitterparameter als auch Wellenlangen mit Genauigkeiten in der Grosenordnung von 10−7d bzw. 10−7λ zu messen.

Diffraction analysis of three-dimensional volume gratings with arbitrary boundaries

Abstract: On the basis of two-dimensional coupled-wave theory, the diffraction of finite bounded beams with arbitrary profiles by nonuniform, arbitrarily bounded mixed volume gratings is described, taking into account deviations from the Bragg condition, attenuation of the modulation depth, and constant absorption. The resulting differential equations are solved numerically with a two-dimensional Runge–Kutta method. The quality of the diffracted beam is influenced strongly by the deviation from the Bragg case. Planar finite gratings in contrast to crossed-beam gratings, show a smoothing effect of the diffraction characteristics. This is also found for crossed-beam gratings with a moderate attenuation. It is demonstrated that the amplitude profiles of the grating writing beams and the readout beams have a strong influence on the intensity profiles of the diffracted beams.

New aspects of the semiempirical theory of 27Al-chemical shift and its application to glasses

Abstract: In the first part of the paper the semiempirical theory of nuclear shielding is extended to the case of the 27Al-chemical shift. The central point is a more precise interpretation of the formula for the dependence of the bond polarity on the electronegativity of the bond partners. The theory gives only a general guideline for the change of the chemical shift with substitution in the first coordination sphere. Using the form of the parabola obtained for the dependence of the chemical shift on the electronegativity of the bond partner it is possible to give an explanation for the large span of shifts in the case of neighbours with high electronegativity like oxygen. In the second part of the paper the recently developed bond polarization theory is applied to explain the influence of substituents in the second coordination sphere on the 27Alchemical shift. This theory establishes a linear correlation between the bond polarization energy and the chemical shift. The bond polarization energy can be calculated o...