Showing papers by "Ludwig Maximilian University of Munich published in 1973"

Direct calculation of ionization potentials of closed-shell atoms and molecules

Abstract: Vertical ionization potentials, electron affinities and information about quasi-particles can be obtained by using the technique of the single-particle propagator. The expansion of the self-energy part up to third order perturbation theory can be evaluated numerically, but does not lead, in most cases, to satisfying results. A theoretical and numerical analysis of the diagrammatic expansion of the self-energy part requires the introduction of a renormalized interaction and renormalized hole and particle lines.

Improved calculations of ionization potentials of closed-shell molecules

Abstract: A theory recently developed for atoms and molecules is applied to the calculation of the main poles of one-particle Green's functions in the low-energy region and their pole strengths for the molecules F2, H2O, C2H2 and H2CO. The poles corresponding to occupied orbitals compare well with the experimental vertical ionization potentials (VIP's). In particular the sequence of the VIP's of F2 which is not reproduced by Koopmans' theorem (breakdown) is re-established. The corresponding pole strengths are found to have values around 0·9.

Membrane leakage in Bacillus subtilis 168 induced by the hop constituents lupulone, humulone, isohumulone and humulinic acid

Abstract: The bactericidal activity of the hop constituents lupulone, humulone, isohumulone and humulinic acid against Bacillus subtilis 168 is shown to result from primary membrane leakage. This process leads to complete inhibition of active transport of α-methyl-d-glucopyranoside and several amino acids into whole bacteria and isolated membrane vesicles within 5 min at 37°C at the corresponding minimal inhibitory concentrations of 1, 2, 25 and 250 μg/ml, respectively. Inhibition of the respiratory chain, of protein, RNA and DNA synthesis seems to be a secondary event.

Membrane specializations in the form of regular membrane-to membrane attachment sites in Paramecium : a correlated freeze-etching and ultrathin-sectioning analysis

Abstract: The outer membrane complex of Paramecium was investigated by ultrathin-sectioning techniques and by freeze-etching of unfixed cells without cryoprotectants. Granules were found in the freeze-etched cortical membrane complex in a highly ordered arrangement; morphometric analyses and partial disruption of this membrane complex showed that some of these granular membrane specializations (which we call types a, b, e, f, g ) represent membrane-to-membrane attachment sites. Type a : granules arranged in rings (single or double), 300 nm in diameter, connect plasmalemma and alveolar membranes around trichocysts. Type b : within these a -type rings, a concentric zone (180 nm diameter) of granules connects plasma membrane and trichocyst membrane. Type c : the trichocyst membrane further contains a central ring or patch, 80 nm in diameter, of rather large granules where it is in contact with the crystalline trichocyst matrix. Type d: ‘ciliary necklaces’ are formed by groups of triple rows of 3-6, most frequently 5 granules, with 21-nm periodicity. Rows of granules also connect the alveolar membranes to the apical portion of the trichocyst membrane (type e ) and the alveolar membrane to the plasmalemma around cilia (type f ). Type g : the inner alveolar membrane displays an intense granularity and contains double rows of granules along alveolar septa at attachment sites between 2 alveolar membranes. Upon experimental discharge of the majority of trichocysts only the innermost concentric circles of membrane-bound granules of this region ( b - and c -type) disappeared from the plasmalemma, while the outermost a -type rings of granules persisted for a longer time. Among other possible functions, these regular membrane-to-membrane attachments are likely to maintain the specific cellular shape.

1,3‐Dipolare Cycloadditionen, 74. Orientierungsphänomene bei Cycloadditionen aliphatischer und aromatischer Nitriloxide an α,β‐ungesättigte Carbonester2)

Abstract: Aufgrund der Umsetzungen von siebzehn Nitriloxiden mit funf α,β-ungesattigten Carbonsaureestern wird der Einflus von Substituenten im 1,3-Dipol auf die Isomerenverteilung im Produkt, d. h. also auf das Verhaltnis der beiden Additionsrichtungen, studiert. Das Orientierungsverhalten wird im wesentlichen von der elektronischen Struktur des Nitriloxid-Systems diktiert und nur untergeordnet vom Substituenten beeinflust. Energetisch gesehen, bewegen sich die Substituenten-Effekte bei den funf Modell-Dipolarophilen zwischen ΔΔG≠ = 0.8 und 2.0 kcal/mol. Der Einflus der Substituenten auf die konkurrierenden Richtungen der [π4S + π2S]-Cycloadditionen wird im Rahmen des Houkschen Ansatzes der MO-Storungstheorie6) diskutiert; sterische Effekte uberlagern sich den elektronischen. — Samtliche Addukte werden analytisch und durch NMR-Spektren charakterisiert. Die Substituenten-Einflusse auf τ- und J-Werte der Ringprotonen von 2-Isoxazolinen und Isoxazolen werden ermittelt. 1,3-Dipolar Cycloadditions, 74. Orientation Phenomena in Cycloadditions of Aliphatic and Aromatic Nitrile Oxides to α,β-Unsaturated Carboxylic Esters The additions of seventeen nitrile oxides to five α,β-unsaturated carboxylic esters have been studied to determine the influence of a substituent in the 1,3-dipole on the isomer distribution in the product, i.e., on the ratio of the two directions of addition. The regiochemistry is mainly dictated by the electronic structure of the nitrile oxide system, and is influenced only to a minor extent by substituents. The substituent effects measured for the five model dipolarophiles, energywise, are between ΔΔG≠ = 0.8 and 2.0 kcal/mole. The influence of substituents is discussed within Houk′s MO perturbation treatment6); steric effects are superimposed. — All adducts have been characterized by analyses and n.m.r. spectra. The influences of substituents on τ and J values of the ring protons of 2-isoxazolines and isoxazoles have been determined.

Optimal Reliability Design of a System: A New Look

Abstract: The reliability literature offers an abundance of methods for the optimal design of systems under some constraints. In most of the papers, the problem considered is: given reliabilities of each constituent component and their constraint-type data, optimize the system reliability. This amounts to the assignment of optimal redundancies to each stage of the system, with each component reliability specified. This is a partial optimization of the system reliability. At the design stage, a designer has many options, e.g., component reliability improvement and use of redundancy. A true optimal system design explores these alternatives explicitly. Our paper demonstrates the feasibility of arriving at an optimal system design using the latter concept. For simplicity, only a cost constraint is used, however, the approach is more general and can be extended to any number of constraints. A particular cost-reliability curve is used to illustrate the approach.

An immunological study of human brain tumors concerning the brain specific proteins S-100 and 14.3.2

Abstract: The distribution of the brain specific proteins, S-100 and 14.3.2, was studied in 80 human brain tumors by means of immunofluorescence and immunoprecipitation techniques. The following observations were made: 1. Both the S-100 and 14.3.2 proteins were shown to be present within nerve cells of human frontal lobes. 2. Both the S-100 and the 14.3.2 proteins were shown to be present in the cells of such gliomas as glioblastomas, astrocytomas, spongioblastomas and acoustic neurinomas and some oligodendrogliomas. 3. The 14.3.2 protein, but not the S-100 protein, could be demonstrated in ependymomas, plexus papillomas and chromophobe adenomas of the pituitary and in three polymorphous oligodendrogliomas. 4. None of the proteins were found to be present in necrotic areas of brain tumors or in meningiomas and brain metastases.

A simple method for measuring red cell deformability in models of the microcirculation

Abstract: By measuring the flow rate of 10% red blood cell suspensions and of clear plasma through Nuclepore® sieves, the deformability of human red blood cells can be quantified. The relative flow rate ( $$\dot V_{rel} $$ ) of red cell suspensions through the 5 μm pores at a driving pressure of 50 mm H2O is a direct measure of the red cell deformability in geometrical and dynamical models of the living microcirculation. $$\dot V_{rel} $$ is about 0.7, it is largely independent of temperature between 4°C and 37°C, but highly dependent upon the pH of the sample. Reduction of $$\dot V_{rel} $$ can be found in blood from patients suffering from various diseased states.

Stimulated Short-Wave Radiation due to Single-Frequency Resonances of χ ( 3 )

Abstract: Single laser pulses at 9455 ${\mathrm{cm}}^{\ensuremath{-}1}$ can generate spectra out to 30 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ without self-focusing. Experimental data for water are explained by primary and secondary stimulated four-photon processes.

1,3-Dipolare Cycloadditionen, 70. Additionen des Benzonitriloxids an olefinische und acetylenische Dipolarophile

Abstract: Benzonitriloxid (2) bildet mit monosubstituierten Athylenen und Acetylenen 2-Isoxazoline (3–10) und Isoxazole (29, 42), bei denen der Rest in der 5-Position erscheint. Ein Gemisch der beiden moglichen Orientierungsisomeren (17/18, 19/20) geht aus den Additionen an β-substituierte Styrole hervor. Abweichend verhielt sich β-Pyrrolidinostyrol, aus dem mit Benzonitriloxid nur 3,4-Diphenyl-5-pyrrolidino-2-isoxazolin (22) entsteht. Auch bei anderen Enaminen diktiert die Aminfunktion ungeachtet sterischer Effekte diese Additionsrichtung. Die Stereospezifitat der Cycloaddition wurde an den cis-trans-isomeren 2-Butenen und Stilbenen dargetan (13–16). Neben Cyclopenten wurde auch das reaktionstragere Cyclohexen zur Reaktion gebracht (36, 37). Das labile bicyclische Primaraddukt des Cyclooctatetraens (38) erleidet einen elektrocyclischen Ringschlus zum tricyclischen Produkt 39. 1,3-Dipolar Cycloadditions, 70. Additions of Benzonitrile Oxide to Olefinic and Acetylenic Dipolarophiles Benzonitrile oxide (2) forms with monosubstituted ethylenes and acetylenes 2-isoxazolines (3–10) and isoxazoles (29, 42) substituted in the 5-position. β-Substituted styrenes yield a mixture of two possible orientation isomers (17/18, 19/20), except β-pyrrolidinostyrene, which produces only 3,4-diphenyl-5-pyrrolidino-2-isoxazoline (22). In other enamines, too, the amino function dictates this direction of addition notwithstanding steric effects. The stereospecificity of the cycloaddition has been shown by the reactions of the cis-trans-isomeric 2-butenes and stilbenes (13–16). Besides cyclopentene the less reactive cyclohexene could be combined with benzonitrile oxide (36, 37). The labile bicyclic primary adduct of cyclooctatetraene (38) undergoes electrocyclic ring closure to form the tricyclic product 39.

Diurnaler Säurerhythmus bei Tillandsia usneoides: Untersuchungen über den Weg des Kohlenstoffs sowie die Abhängigkeit des CO2-Gaswechsels von Lichtintensität, Temperatur und Wassergehalt der Pflanze

Abstract: Tillandsia usneoides, in the common sense a non-succulent plant, exhibits CO2 exchange characterized by net CO2 dark fixation during the night and depression of CO2 exchange during the day. Malate has been demonstrated to accumulate during CO2 dark fixation and to be converted to carbohydrates in light. Thus, T. usneoides exhibits CAM like typical succulents.

Dependency of Pial Arterial and Arteriolar Diameter on Perivascular Osmolarity in the Cat: A Microapplication Study

Abstract: The effect of perivascular osmolarity on the diameter of pial arteries was studied in cats by the microapplication technique. Between 251 and 360 mosmoles/liter, concentration-response curves were obtained for single vessels. Constriction occurred when perivascular osmolarity was decreased below 317 mosmoles/liter, and dilation occurred at osmolarities above this value. The effect was the same whether the osmolarity was changed by addition of mannitol or NaCl. Reduction of sodium concentration from 156 to 133 mEq/liter at constant osmolarity did not affect arteriolar diameter, but greater reductions in sodium concentration induced vasoconstriction. The results indicate that the resistance of pial arteries can be influenced by local changes in perivascular osmolarity.

Electrophysiological-histological studies on some functional properties of visual cells and second order neurons of an insect retina

Abstract: Intracellular potential recording in combination with a histological technique of cell identification and localization of the recording site was used to get some results about information processing properties of an insect retina on the cellular level.

Water-soluble and pentanol-extractable proteins in human brain normal tissue and human brain tumours, with special reference to s-100 protein

Abstract: Disc electrophoretic separation of water-soluble and pentanol-extractable protein from normal human brain and human brain tumours (glioblastoma, neurinoma and medulloblastoma) on 10 per cent polyacrylamide gels showed minor differences between tissues. After disc electrophoresis ependymomal tumour cells contained high concentrations of a rapidly migrating anodic protein fraction which was immunologically distinct from S-100 protein. After electrophoresis of normal brain grey matter in a continuous buffer system, a rapidly migrating anodic protein fraction which was immunologically distinct from S-100 protein was found, and this protein fraction had a similar relative mobility to that of ependymomal tumour cells. This protein fraction was present to a low extent in human normal white matter, but absent from neurinoma and glioblastoma. In a continuous buffer system at least two separable protein fractions, immunologically equivalent to S-100 protein, were observed in normal human brain. The more anodic of these two fractions was shown to be present in relatively high amounts in neurinomas, and may be of Schwann cell origin. Additional S-100 protein could be extracted from residual material remaining after removal of water-soluble proteins; 2.8-10 per cent of the water-soluble S-100 in normal material, and 0.1-0.6 per cent of that present in tumour material, was extractable from the water-insoluble residue by pentanol.

1,3-Dipolare Cycloadditionen, 73. Relative Dipolarophilen- Aktivitäten bei Cycloadditionen des Benzonitriloxids

Abstract: Die Konkurrenz von Dipolarophilen-Paaren um Benzonitriloxid,. In situ aus Benzohydroximoylchlorid (4) freigesetzt, ergab die sich uber 4 Zehnerpotenzen erstreckenden relativen Additionskonstanten von 39 Dipolarophilen. Benzonitriloxid gehort zu den 1,3-Dipolen, die sowohl mit elektronen-armen als auch mit elektronen-reichen Mehrfachbindungen rascher reagieren als mit gewohnlichen Alkenen und Alkinen. Die Kombination mit den bekannten Orientierungsverhaltnissen erbrachte partielle Geschwindigkeitskonstanten der beiden Additionsrichtungen. Die Additivitat der Substituenten-Beitrage zur freien Aktivierungsenergie ist nur naherungsweise erfullt. — Die spezifische Dipolarophilen-Skala des Benzonitriloxids sowie die Orientierungsphanomene werden im Lichte neuer MO-storungstheoretischer Behandlungen von Sustmann und Houk diskutiert. Die Aktivitatssequenz wird mit denjenigen des Diphenylnitrilimins und des N-Methyl-C-phenylnitrons verglichen. 1,3-Dipolar Cycloadditions, 73. Relative Dipolarophile Activities in Cycloadditions of Benzonitrile Oxide The cornpetition of pairs of dipolarophiles for benzonitrile oxide, liberated in situ from benzohydroximoyl chloride (4), allows evaluation of the relative addition constants of 39 dipolarophiles which cover a range of four powers of ten. Benzonitrile oxide belongs to the type of 1,3-dipoles which react faster both with electron-deficient and electron-rich multiple bonds than with common alkenes and alkynes. Combination of these data with the known orientations provides the partial rate factors for the two directions of cycloaddition. The additivity of substituent contributions to the free energy of activation is only fulfilled to a first approximation. — The specific dipolarophile scale of benzonitrile oxide, as well as the orientation phenomena, are discussed in the light of the new MO perturbation treatments of Sustmann and Houk. The dipolarophile activity sequence of benzonitrile oxide is compared with those of diphenylnitrilimine and N-methyl-C-phenylnitrone.

Übergangsmetall‐Carben‐Komplexe, LIV. Synthese von übergangsmetall‐carbonyl‐ylid‐Komplexen aus übergangsmetall‐carbonyl‐carben‐Komplexen

Abstract: Durch Umsetzung sekundarer und tertiarer Alkylphosphine PX3 [X3 = (CH3)3, (C2H5)3, (n-C4H9)3, (CH3)2H] mit den (Alkoxycarben)- bzw. (Alkylthiocarben)pentacarbonyl-Komplexen von Chrom(0) und Wolfram(0), (CO)5Cr[C(OCH3)C6H5], (CO)5W[C(OCH3)CH3] und (CO)5W[C(SCH3)CH3], bei tiefen Temperaturen wurden unter Addition der Phosphine an das Carbenkohlenstoffatom entsprechende Ylid-pentacarbonylmetall-Komplexe (CO)5 M[C(PX3) (YCH3)(Z)] (M = Cr, W; Y = O, S; Z = CH3, C6H5) erhalten. Die Strukturen der schwach gelblichen, diamagnetischen, z T. sehr thermolabilen Verbindungen wurden durch Analyse, IR-, NMR- und Massenspektren gesichert. Die partielle thermische Reaktion von (CO)5Cr[C(P(CH3)2H)(OCH3)(C6H5)] in Aceton zu (CO)5Cr{P(CH3)2[CH(OCH3)(C6H5)]} wurde nachgewiesen. Transition Metal Carbene Complexes, LIV. Synthesis of Transition Metal Carbonyl Ylide Complexes from Transition Metal Carbonyl Carbene Complexes Secondary und tertiary alkylphosphines PX3 [X3 = (CH3)3, (C2H5)3, (n-C4H9)3, (CH3)2H] react with (alkoxycarbene)- or (alkylthiocarbene)pentacarbonyl complexes of chromium(0) and tungsten(0),(CO)5Cr[C(OCH3)C6H5], (CO)5W[C(OCH3)CH3] and (CO)5W[C(SCH3)CH3], at low temperatures to give the corresponding ylidepentacarbonylmetal complexes (CO)5M[C(PX3)(YCH3)(Z)] (M = Cr, W; Y = O, S; Z = CH3, C6H5) under addition of the phosphines to the carbene carbon atom. The structures of the pale yellow, diamagnetic, and partially very thermolabile compounds were established by analysis, i.r., n.m.r., and mass spectra. The partial thermal conversion of (CO)5Cr[C(P(CH3)2H)(OCH3)(C6H5)] in acetone was shown to yield (CO)5Cr{P(CH3)2[CH(OCH3)(C6H5)]}.

Morphological and autoradiographical investigations on experimental carcinogenesis and polyp development in the intestinal tract of rats and mice.

Abstract: Most types of neoplastic lesions seen in human intestinal mucosa were reproduced experimentally in rats and mice after application of 1,2-dimethylhydrazine. Tumor distribution displayed dose-related variations. The relative tumor frequency in the small intestine rose after higher dosage of the carcinogen, with preponderance of the upper segments. Furthermore there were certain species specific differences between rats and mice concerning the tumor distribution within the large intestine.

Raman Difference Spectroscopy with the Rotating Cell

Abstract: A simple technique is described which makes it possible to record Raman difference spectra of binary liquid systems. The main feature is a divided rotating Raman cell for liquids and a gated electronic system. The cancellation of solvent lines in the Raman spectrum of a solution is demonstrated on a 1:1 mixture of CCl4 and CHCl3 and on an MnO4−-H2O solution. Further advantages of this technique are accurate wavenumber shift measurements (e.g., the isotopic lines of ν1 in CHCl3) and correction of the intensity error of Raman lines obtained from highly absorbing solutions (e.g., I2-CHCl3).