Showing papers by "University of Hamburg published in 1974"

On the spectral dissipation of ocean waves due to white capping

Abstract: The effect of white capping on the spectral energy balance of surface waves is investigated by expressing the white-cap interactions in terms of an equivalent ensemble of random pressure pulses. It is shown first that the source function for any non-expansible interaction process which is weak-in-the-mean is quasi-linear. In the case of white capping, the damping coefficient is then shown to be proportional to the square of the frequency, provided the wave scales are large compared with the white-cap dimensions. The remaining free factor is determined indirectly from consideration of the spectral energy balance. The proposed white-capping dissipation function is consistent with the structure of the energy balance derived from JONSWAP, and the existence of a δ−5 spectrum governed by a non-local energy balance between the atmospheric input, the nonlinear energy transfer and dissipation. However, closure of the energy balance involves hypotheses regarding the structure of the atmospheric input function which need to be tested by further measurements. The proposed set of source functions may nevertheless be useful for numerical wave-prediction. According to the model, nearly all the momentum transferred across the air-sea interface enters the wave field. For fetchlimited and fully developed spectra in a stationary, uniform wind field, the drag coefficient remains approximately constant. However, for more general wind conditions, this will not be the case and the wave spectrum should be included in an accurate parameterisation of the air-sea momentum transfer.

Use of synchrotron radiation in X‐ray diffraction topography

Abstract: Synchrotron radiation which is emitted into a narrow cone and which has a continuous spectrum was succesfully used in X-ray topography. The exposure time to take a set of topographs (a transmission Laue pattern) from a silicon crystal on a fine grain film with a geometric resolution of a few microns turned out to be as short as some seconds. As an example for the use of the new method the contrast formation of a defect in the Laue pattern of topographs was analysed in detail. For this purpose the relative integrated intensities of different orders of reflections were calculated. They and the calculated values of extinction distances were used to estimate the image width of a dislocation whose Burgers vector could be determined. Synchrotronstrahlung, die ein kontinuierliches Spektrum besitzt und in eine schmale Keule emittiert wird, wurde erfolgreich in der Rontgentopographie benutzt. Es erwies sich, das die Belichtungszeit, um mehrere Topographen (ein Laue-Bild mit Transmissionsverfahren) von einem Silizium-Einkristall auf einen feinkornigen Film mit gutem Auflosungsvermogen aufzunehmen, nur einige Sekunden betragt. Als Beispiel fur die Anwendung der neuen Methode wurde die Kontrastbildung eines Defektes im Laue-Bild der Topographen analysiert. Zu diesem Zweck wurden die relativen integrierten Intensitaten der Reflexe verschiedener Ordnungen berechnet. Diese und die berechneten Werte der Extinktionslangen wurden zur Abschatzung der Bildbreite einer Versetzung, deren Burgers-Vektor bestimmt werden konnte, benutzt.

Stability and equilibrium states

Abstract: For an infinite dynamical quantum system idealized as aC*-algebra acted upon by time-translations automorphisms in an asymptotically abelian way, we propose to characterize equilibrium states by the three properties of stationarity, stability for local perturbations of the dynamics, and relative purity. We show that a state with these properties either gives rise to a one-sided energy spectrum or is a KMS- (i.e. essentially a limit Gibbs-) state.

Product states for local algebras

Abstract: Let ℛ( )⊂ℛ(ℋ) and ℛ( ) ⊂ℛ(ℋ) be the von Neumann algebras associated with the space-tiem regions and respectively in the vacuum representation of the free neutral massive scalar field. For suitably chosen spacelike separated regions and it is proved that there exists a normal product state ϕ of ℛ(ℋ), Some consequences for the algebraic structure of the local rings are pointed out.

Konformationsanalyse, V. Einfluß des anomeren und inversen anomeren Effektes auf Konformationsgleichgewichte von N-substituierten N-Pentopyranosiden

Abstract: Konformationsgleichgewichte von N-substituierten N-Pentopyranosiden wurden untersucht. Der anomere Effekt nimmt bei Substitution am C-1 durch nachstehende Gruppen in folgender Reihe ab: > OAc > N3 > NHCOCF3 > NHCOC6H4OCH3-(p) ≃ NHCO- C6H4NO2-(p) > NH2 ≃ NHAc ≃ (C6H5)3]Cl⊖ > Imidazoliumsalz ≃ Pyridiniumsalz. Bei der NH2-Gruppe ist kein anomerer und inverser anomerer Effekt nachweisbar. Die Imidazolium- und Pyridinium-Verbindungen 33 und 31 zeigen inversen anomeren Effekt, wodurch in der α-D-xylo-Reihe Inversion zur triaxialen 1C4(D)-Konformation eintritt. Dem C1N1-Dipol wird ein uberwiegender Einflus auf den anomeren Effekt zugemessen. Der Substituent mit negativiertem Stickstoff weist den grosten anomeren Effekt auf, der bei Protonierung des Ylids zur (C6H5)3]Cl⊖-Gruppe vollstandig verschwindet. Conformational Analysis, V. Influence of the Anomeric and Reverse Anomeric Effect on Conformational Equilibria of a N-Substituted N-Pentopyranosides The conformational equilibria of N-substituted N-pentopyranosides have been investigated. The anomeric effect decreases with substitution at C-1 by the following groups in the order: > OAc > N3 > NHCOCF3 > NHCOC6H4OCH3-(p) ≃ NHCOC6H4NO2-(p) > NH2 ≃ NHAc ≃ (C6H5)3]Cl⊖ > imidazolium salt ≃ pyridinium salt. Neither an anomeric effect nor a reverse anomeric effect was detectable with the NH2-group. The imidazolium and pyridinium compounds 33 and 31 show a reverse anomeric effect, whereby in the α-D-xylo-series inversion to the triaxial 1C4(D) conformation takes place. a predominant influence on the anomeric effect is attributes to the C1N1 dipole. The substituent with a negatively charged nitrogen shows the largest anomeric effect, which completely disappears upon protonation of the ylid to (C6H5)3]Cl⊖.

The vertical structure of the atmospheric planetary boundary layer in undisturbed trade winds over the atlantic ocean

Abstract: During the Atlantic Expedition 1965 and the Atlantic Tradewind Experiment (ATEX) 1969, shipborne aerological measurements were obtained in order to investigate the thermodynamical and kinematic structure of the planetary boundary layer in low latitudes. Under suppressed convection, the subdivision of this layer into five sub-regions was found to be a rather permanent feature. Enhanced cumulus convection effects a smoothing of the thermodynamical discontinuities and leads sometimes to a destruction of the trade inversion. Due to the surface pressure distribution and the thermal wind distribution in the lower atmosphere, the actual wind speed and direction are nearly constant with height below cloud base. In the cloud layer up to the inversion, the wind speed generally decreases and the air flow tends to become more zonal.

Konformationsanalyse, III. exo‐Anomerer Effekt und Circulardichroismus von Glycopyranosylaziden

Abstract: Tetra-O-acetyl-pentopyranosen und Penta-O-acetyl-hexopyranosen setzen sich mit Trimethylsilylazid bei Gegenwart von BF3 oder SnCl4 leicht zu den entsprechenden Glycosylaziden 1a bis 11 um (Tab. 1). Es entsteht stets nur das anomere Glycosylazid, in dem die Azidogruppe und 2-OAc „trans” zueinander angeordnet sind. In Glycosylaziden sind die Bindungen ClNx und NxNz in der Weise polarisiert, das der Dipol in beiden Fallen zum Nx weist. Hieraus wird abgeleitet, das bei Glycosylaziden wie bei Methylglycosiden ein exo-anomerer Effekt wirksam sein sollte, der die Konformeren 9 und 12 stark bevorzugt. Die Anwendung der Azid-Oktantenregel sagt fur das α-D-Glycosylazid 12 einen negativen, fur das β-D-Glycosylazid 9 einen positiven Cotton-Effekt voraus. Messungen des Circular-dichroismus stimmen mit diesen Voraussagen gut uberein, was fur einen exo-anomeren Effekt bei Glycosylaziden spricht. Conformational Analysis, III. exo-Anomeric Effect and Circular Dichroism of Glycopyranosyl Azides Tetra-O-acetyl-aldopentopyranoses and penta-O-acetyl-aldohexopyranoses react readily with trimethylsilyl azide in the presence of BF3 or SnCl4 to afford the corresponding glycosyl azides 1a – 11 (table 1). Only the anomeric glycosyl azide having the azido group „trans” to the 2-acetoxy group is obtained in each case. The polarization of the ClNx and NxNz bonds in glycosyl azides is such that in both cases the dipole is directed toward Nx. It can be deduced that glycosyl azides, like methyl glycopyranosides, should exhibit an exo-anomeric effect which strongly favors the conformers 9 and 12. The application of the azide-octant rule predicts a negative Cotton effect for the α-D-glycosyl azide 12 and a positive effect for the β-D-glycosyl azide 9. Circular dichroism measurements are in good agreement with these predictions, indicating the operation of an exo-anomeric effect in the glycosyl azides.

Elektronenmikroskopische Untersuchungen an Paulinella chromatophora Lauterborn, einer Thekamöbe mit blau-grünen Endosymbionten (Cyanellen)

Abstract: Die Feinstruktur der Cyanellen vonPaulinella chromatophora sowie die Bildung und Struktur der Kieselschuppen, die das Gehause dieser Thekamobe aufbauen, wurden untersucht. Die beiden wurstformigen Cyanellen besitzen eine 6–13 nm dicke Wandschicht. Sie liegen eingeschlossen in Vesikeln im Cytoplasma des Wirtes. Das Chromatoplasma der Cyanelle enthalt 15–20 konzentrisch angeordnete Thylakoide, Plastoglobuli und Phycobilisomen. Das Centroplasma enthalt polyedrische Korper. Das Gehause der Thekamobe besteht aus verkieselten rechteckigen Schuppen, die sehr regelmasig zum Gehause zusammengefugt sind. Die Schuppen haben eine komplizierte Feinstruktur. Sie entstehen, vielleicht unter Mitwirkung von Mikrotubuli, vor der Zellteilung in Vesikeln, die wahrscheinlich aus Zisternen des einzigen Dictyosomes der Thekamobe hervorgehen. Dieses Dictyosom liegt dem Zellkern am aboralen Pol derPaulinella an. Hexagonale Korper (Virionen?) werden aus dem Zellkern und dem Cytoplasma des Wirtes beschrieben.

Thiophile Addition von Phenyllithium an Thioketene

Abstract: Bei −78°C reagieren die Dialkylthioketene 1a–d mit Phenyl- und Methyllithium unter thiophiler Addition zu den Thioathern 3a–d und 4. Die carbenoide Zwischenstufe konnte fur 2c mit Kohlendioxid und mit Methyljodid zu 7 und 8 abgefangen werden. Bei Raumtemperatur gehen die Carbenoide 2b–d α-Eliminierung zu den Alkylidencarbenen 15b–d ein, die zu den Butatrienen 13b–d, den Alkenen 14b–d und fur 15d zum CH-Insertionsprodukt 16 weiterreagieren. Thiophilic Addition of Phenyllithium to Thioketenes At −78°C the dialkylthioketenes 1a–d react with phenyl-and methyllithium in thiophilic additions to give the thioethers 3a–d and 4. The carbenoid intermediate 2c could be trapped with carbon dioxide or methyl iodide to 7 and 8. At room temperature α-elimination occurs in the carbenoids 2b–d with formation of the alkylidencarbenes 15b–d, which react further to yield the butatrienes 13b–d, the alkenes 14b–d, and in the case of 15d to give the CH-insertion product 16.

On the morphology of the human Sertoli cell.

Abstract: As revealed by light microscopical investigations the human Sertoli cell presents different appearances according to the pattern of infranuclear cytoplasmic inclusions. Although two or three stages of spermatogenesis are seen in a single cross section of a seminiferous tubule the Sertoli cells all show virtually the same features in such a cross sectioned tubule. The different appearances are also evident under the electron microscope. Although no obvious correlation was found with the stages of spermatogenesis in the seminiferous epithelium, the Sertoli cell appearances described here may be assumed to represent different metabolic situations. Other features of Sertoli cell ultrastructure are discussed such as the presence of residual bodies in the apical cytoplasm, glycogen-rich areas protruding towards the tubular lumen or the extracellular space, and membrane bound, round structures, found between the membranes of the smooth endoplasmic reticulum and resembling the “microbodies” of steroid producing cells.

Light and electron microscopical analysis of cell types in human seminoma.

Abstract: Samples of solid tumours were obtained from six patients with classical seminoma, either from the center or the periphery of the tumour as well as from macroscopically normal-looking testioular tissue. The tissues were examined by light and electron microscopy. In different places of the affected testis, three different tumour cell types were found: The tumour cells of type 1 show characteristics of human embryonic germinal cells, those of type 3 being the more differentiated and forming most of the tumoral mass. Hence classical seminoma is formed not only by large clear cells as stated in the literature, but instead by more cell types, as described in the present work.

Turbulent fluxes of momentum, heat and water vapor in the atmospheric surface layer at sea during ATEX

Abstract: The vertical turbulent fluxes have been determined during the Atlantic Trade Wind Experiment (ATEX) both by direct and profile methods. The drag coefficient obtained from direct measurements was c D = 1.39 × 10−3. A distortion of the wind profile due to wave action could be demonstrated, this produced an increased drag coefficient estimated by the profile method. The dissipation technique using the downwind spectrum gave a lower drag coefficient of 1.26 × 10−3, probably due to non-isotropic conditions (the ratio of vertical to downwind spectrum at high frequencies scattered considerably with an average of 1 instead of 4/3). From direct measurements, the sensible heat flux showed a poor correlation with the bulk parameter product Uδθ, contrary to the heat flux obtained from profiles. It is shown that this is due to the higher frequency part of the cospectrum, say above 0.25 Hz, which contributes more than 50 % of the total flux. Determination of the heat flux from temperature fluctuations by the dissipation method would be in agreement with the direct determination only if the corresponding Kolmogoroff constant were 2.1 instead of 0.8. For the vertical flux of water vapor obtained from profiles, the bulk transfer coefficient was 1.28 × 10−3.

De- and regeneration of the bulbospinal serotonin neurons in the rat following 5,6-or 5,7-dihydroxytryptamine treatment.

Abstract: In an attempt to determine the conditions which permit central 5-HT neurons to respond to a chemical injury of their axons by sprouting and regeneration, the pattern and time-course of recovery of 5-HT concentrations and regrowth of bulbospinal 5-HT axons were evaluated in rats subjected to intraventricular treatment with either 75 μg 5,6- or 150 μg 5,7-DHT While 5,6-DHT treatment is followed by a significant recovery of 5-HT concentrations in the telodiencephalon, brainstem and upper part of the spinal cord within 3 months, there is no significant restoration of the severely depleted 5-HT levels in the telodiencephalon and spinal cord, and only limited recovery in 5-HT content of the brainstem preparation after 5,7-DHT

Apical dominance in roots of Pisum sativum L

Abstract: The influence of several natural and synthetic hormones on apical dominance of pea roots was investigated. Extracts of roots decapitated just before extraction or 12 h earlier were compared in a lateral root formation assay, in the Amaranthus assay for cytokinins and the Avena coleoptile assay. Indole-3-acetic acid shows a strong promotive effect on the initiation of lateral roots. Gibberellic acid has no significant effect. Abscisic acid and its presumable precursor xanthoxin show a strong inhibitory effect, and so do all cytokinins investigated (kinetin, benzyladenine, and zeatin). Decapitation of roots caused a significant increase in the number of lateral root primordia within 12 h. Paper chromatograms of root extracts indicate the presence of at least two inhibitors of lateral root formation in the alkaline fraction, and of two promoters in the acid fraction. The amount of both inhibitors seems to decrease if the tip of the main root is removed 12 h before extraction whereas the promoters of lateral root formation do not change in their concentration. The Amaranthus test shows cytokinin activity in the region of one of the two inhibitors, and this activity decreases after decapitation. The second inhibitor has the Rf of xanthoxin; it inhibits the growth of Avena coleoptiles and its activity also decreases after decapitation.

Reflection spectroscopy on monoclinic crystals

Abstract: The properties of the dielectric tensor of a monoclinic crystal are reviewed and the nature of transverse excitations is pointed out. Reflection equations for normal incidence on the (010) plane and (001) plane are presented, by use of which full information on all tensor components may be obtained from reflection measurements and Kramers- Kronig analysis. A reflection equation for oblique incidence on faces ( h 1 , O, h 3 ) with plane of incidence (010) and transverse magnetic polarization allows the comparison of reflectance spectra calculated from the dielectric tensor components with respective experimental spectra. Simple model calculations related to exciton structures in molecular crystals and quasi one-dimensional materials are displayed.

The significance of calcium in insulin secretion. Ultrastructural studies on identification and localization of calcium in activated and inactivated B cells of mice.

Abstract: Calcium plays an important role in the release of insulin. When the GBHA [glyoxal bis (2-hydroxyanil)] reaction is employed, calcium can be clearly demonstrated by light microscope in pancreatic islets of mice. The specificity of this finding has now been proved by elemental X-ray analysis. Electron microscopically, certain cations can be visualized by a precipitation technique using potassium pyroantimonate as the precipitating agent. In the B cell of mice this technique reveals a characteristic precipitation pattern. Elemental X-ray analysis suggests that the precipitates contain high amounts of calcium. The pattern of the precipitates changes dependent on the functional state of the B cell. In normoglycemia the deposits are mainly associated with the granule membranes, the cell membranes and the cytoplasmic matrix. In hypoglycemia there is a shift of precipitates into the endoplasmic reticulum and the mitochondria, which are thought to be storage organelles for intracellular calcium. The deposits within the halos of the numerous secretory granules, are diminished. In hyperglycemia there is a marked ion translocation across the cell membrane to its inner surface and particularly into the halos of the secretory granules, while the deposit content of mitochondria and endoplasmic reticulum is decreased. Within the saccules of the secretory granules, the deposits sometimes seem to impregnate a filamentous network, which encloses the secretory granule and cannot be seen by conventional electron microscopical preparations. The morphological data suggest that emiocytosis of hormone granules is associated with a release of cellular calcium. The presented observations in treated and untreated animals extend and support the conceptions on the specific role of calcium within the insulin releasing mechanism of the B cell.

Black holes in static electrovac space--times

Abstract: The theorem of Israel which characterizes the Reissner-Nordstrom solutions as the only well behaved asymptotically flat electrovac spaces with a simple regular horizon is extended by weakening the assumptions. Critical points of the gravitational potential are not a priori excluded and the topology of the eguipotential surfaces is not restricted. The regularity of the horizon is formulated in terms of bounds for certain geometrical quantities and the assumption of existence, in some extension, of a bifurcation surface for the horizons is not made. The possibilities of non-static or non-conservative electromagnetic fields in a static space-time are discussed and excluded by physical arguments.

Some applications of dilatation invariance to structural questions in the theory of local observables

Abstract: In a dilatation-invariant theory it is shown that there is a unique locally normal dilatation-invariant state. Furthermore a gauge transformation of a local algebra cannot be implemented by a unitary operator from the local algebra. If the local field algebras are factors then so are the local observable algebras. The superselection structure of the theory can be determined locally.