Showing papers by "University of Bonn published in 1972"
TL;DR: In this paper, the authors consider the problem of finding a non-abelian free group with a solvable normal subgroup R such that R is locally finite (i.e., every jinite subset generates a $nite subgroup).
894 citations
TL;DR: In this paper, a linear representation of a given category is given by a map V associating with any morphism ϕ: a→e of K a linear vector space map V(ϕ): V(a)→V(e).
Abstract: LetK be the structure got by forgetting the composition law of morphisms in a given category. A linear representation ofK is given by a map V associating with any morphism ϕ: a→e ofK a linear vector space map V(ϕ): V(a)→V(e). We classify thoseK having only finitely many isomorphy classes of indecomposable linear representations. This classification is related to an old paper by Yoshii [3].
862 citations
TL;DR: A simple and direct fluorescence staining procedure is described by which chromosomal segments of constitutive heterochromatin and (in the mouse) sites of repetitious DNA can be visualized in mammalian chromosomes with a benzimidazol derivative “33258 Hoechst” belonging to a class of DNA-binding fluorochromes different from compounds of the Q-series.
324 citations
TL;DR: The substrate specificity of the catechol-O-methyltransferase, purified from human liver 380-fold, has been tested with a variety of compounds, and under standard assay conditions, 2-hydroxy-17β-estradiol was the preferred substrate for the enzyme, as compared with epinephrine and other catechols tested.
Abstract: The substrate specificity of the catechol-O-methyltransferase, purified from human liver 380-fold, has been tested with a variety of compounds. Catechol estrogens, as well as catechol amines are methylated to their corresponding monomethyl ethers. The relation of the rates of methylation of catechol estrogens and catechol amines depended on enzyme and substrate concentration; under standard assay conditions, 2-hydroxy-17β-estradiol was the preferred substrate for the enzyme, as compared with epinephrine and other catechols tested. Km-values for 2-hydroxy-17β-estradiol were 15 μm, for 2-hydroxy-estrone 20 μm, for 2-hydroxy-estriol 25 μm and for-hydroxy-estrone 20 μm. For epinephrine and norepinephrine, Km-values of 300 μm and 200 μm, respectively, were obtained. The ratio of formation of the isomeric monomethyl ethers of catechol estrogens varied between 1.3 and 95, depending on the substrate incubated. On the basis of kinetic studies with different enzyme preparations, different inhibitors and different c...
276 citations
TL;DR: The comparative study of the phylogeny of social behavior in both families uncovers remarkable convergences of patterns from asocial to permanent-social via periodical-social species of spiders.
Abstract: Whereas most spiders are asocial, species in eight families are known to live all their life in communities and are thus “permanent-social.” Their special attributes are: tolerance, interattraction, and cooperation. These peculiarities must have been achieved step by step several times independently. Periodic-social spiders have been studied as a link between asocial and permanent-social spiders. In two families—the cribellate Eresidae and ecribellate Theridiidae—different steps of periodic sociality have been discovered, from brood-care to feeding by regurgitation. The comparative study of the phylogeny of social behavior in both families uncovers remarkable convergences of patterns from asocial to permanent-social via periodical-social species of spiders.
213 citations
TL;DR: In this paper, the use of emitters which have been activated at high temperature in Field Ionization and Field Desorption mass spectrometry offers some important advantages over the usual emitter type activated at room-temperature.
Abstract: The use of emitters which have been activated at high temperature in Field Ionization and Field Desorption mass spectrometry offers some important advantages over the usual emitter type activated at room-temperature. Higher thermal stability of the microneedles is achieved and the emitters are extremely resistant to chemical attack. It becomes possible to induce a thermal fragmentation of solid compounds adsorbed on the emitter surface between room-temperature and approximately 2000°C. The field anodes may be re-used many times without loss of quality. The problem of mass references is solved in Field Ionization/Field Desorption-Mass Spectrometry when high temperature emitters are used. The Field Ionization mass spectra of perfluorokerosene (PFK) and perfluorotributylamine display peaks in the mass range between m/e 50 to 800, with a resolution of up to 30000 (10% valley definition). A short description of a rapid and easy activation to produce high temperature microneedles is given.
The following abbreviations are used throughout this paper:— Text
Table Text. HT High Temperature
RT Room-Temperature
BAT Best Anode Temperature
HR High Resolution
MS Mass Spectrometry/Spectrum/Spectra
EI Electron Impact
FI Field Ionization
CI Chemical Ionization
FD Field Desorption
182 citations
TL;DR: The examination of the possible homology or heterology by breeding procedures revealed the surprising fact that independence, partial or heterobrachial homology of the metacentric chromosomes prevail among mice from different geographical areas.
Abstract: Cytogenetic studies of feral mice (M. musculus) from various but predominantly Alpine areas of Switzerland, carried out on random samples collected by spot-checks, established the widespread existence of metacentric chromosomes in the somatic karyotype. Despite the finding of the common occurrence of some of the metacentrics in different places, the examination of the possible homology or heterology by breeding procedures revealed the surprising fact that independence, partial or heterobrachial homology of the metacentric chromosomes prevail among mice from different geographical areas. Thus, the general picture is that of an array of different metacentric chromosomes derived from independent events of Robertsonian variation in the process of evolution. — While heterozygosity with independent metacentrics within a Robertsonian system may have a bearing on the fertility rate of a given mouse population, a more severe impairment of the reproductive capacity must be taken into account in mouse populations which possess different metacentrics with mono- or heterobrachial homologies. These conditions favour the assumption of the existence of a selective system of reproductive barriers further subdividing the species in many, more or less stable, micro-populations. — The chromosomal arms (telocentrics) involved in the formation of the metacentric chromosomes could be identified by Q- and G-banding techniques in combination with the results of crossbreeding, and were assigned to the corresponding telocentric autosomes of the mouse (Comm. Standard. Genet. Nomenclat. for Mice, 1972). Most of the telocentric autosomes of the mouse are included in one or more of the metacentrics found in the feral populations. By means of their isolation in separate lines, these metacentrics may be useful in experimental biology as marker chromosomes of defined identity carrying known linkage groups.
143 citations
TL;DR: The hypothesis is put forward that the vertical bundles of dendrites are the morphological substrate of the vertical functional units deduced from electrophysiological observations.
Abstract: In frontal and tangential paraffin sections through the sensory-motor cortex of the rabbit, vertical bundles of dendrites have been found. Each bundle consists of several apical dendrites of layer V pyramids and extends through layer IV into layer III/II where the dendrites begin to ramify. Electron microscopy reveals that within the bundle some of the dendrites approach each other so closely as to be separated by the extracellular space only. A vertical bundling of dendrites has, also been found in various regions of the sensory-motor cortex of the cat. — The hypothesis is put forward that the vertical bundles of dendrites are the morphological substrate of the vertical functional units deduced from electrophysiological observations.
114 citations
93 citations
TL;DR: In this article, a three-dimensional model for the annual and semiannual variations of the thermosphere is presented in which energy and diffusive mass transport associated with the global circulation are considered in a self-consistent form.
Abstract: A three-dimensional model for the annual and semiannual variations of the thermosphere is presented in which energy and diffusive mass transport associated with the global circulation are considered in a self-consistent form It is shown that these processes play a major role in the thermosphere dynamics and account for a number of temperature and compositional phenomena
92 citations
TL;DR: In this paper, the authors investigate the bootstrap for the hadronic mass spectrum, which has been proposed by Hagedorn and Frautschi, and derive the sum rules which relate the asymptotic parameters of the spectrum, especially the maximal temperature, to its low mass part.
TL;DR: Field desorption mass spectrometry is a proper method to analyse substances of low volatility, for example free peptides, and even those containing unprotected arginine and histidine which do not yield useful electron or chemical ionization mass spectra.
TL;DR: In this paper, a one-boson exchange potential (OBEP) represented in momentum space and a helicity state basis is used to calculate the nuclear phase shifts up to 330 MeV, the deuteron and two-nucleon low-energy data.
TL;DR: A comparative analysis of the developmental processes as well as the fine structure of the microgametes of these species and those of other Sporozoa is presented.
Abstract: The fine structure of the microgamonts and microgametes of coccidia and related groups was investigated and is herein described and diagrammatically depicted. Particular attention is given to the developmental processes during the differentiation of the microgametes. The species included in the study are: Eimeria perforans, E. maxima, E. tenella, E. auburnensis, E. falciformis, and Toxoplasma gondii. A comparative analysis of the developmental processes as well as the fine structure of the microgametes of these species and those of other Sporozoa is presented.
TL;DR: In this paper, it was shown that the V-N Franck-Condon absorption maximum may differ significantly from the energy of the absorption maximum with which it is often equated, and in particular it is found in the case of theπ→π* singlet-singlet excitation of ethylene that the ΔE fixmee value overestimates the most probable vibrational transition energy (7.89 eV) by some 0.4 eV.
Abstract: Ab initio calculations for CH2 twisting and CC stretching vibrational wavefunctions and energy levels are reported for various electronic states of ethylene C2H4. Electronic transition moments between these states are also obtained to allow a calculation of the oscillator strengths for vibrational transitions involved in various electronic band systems; from this study it is concluded that thevertical electronic energy differenceΔE
e may differ significantly from the energy of the absorption maximumΔE
max with which it is often equated. In particular it is found in the case of theπ→π
* singlet-singlet excitation of ethylene that theΔE
e value overestimates the most probable vibrational transition energy (7.89 eV) by some 0.4 eV, thereby offering an explanation for the fact that previous attempts to predict the location of theV-N Franck-Condon absorption maximum have consistently obtained substantially higher results than the 7.66 eV value actually observed. Similar calculations for various Rydberg species and for theN-T transition are also found to obtain a quite consistent representation of the electronic spectrum of this system.
TL;DR: In this paper, a two-body radiative recombination at a rate of 4.2 × 10 −18 cm 3 molecule −1 sec −1 and a three-body process with O 2 as the third body was shown to coincide with the overall termolecular combination of NO with O.
TL;DR: Application of the crossover theorem showed that the passage of sugar molecules across the cell membrane is affected by regulatory alterations of the flux as well, and analysis of the kinetic data points to membrane transport as the rate limiting step of glycolytic flux.
TL;DR: In this article, a new Methode zur reproduzierbaren Darstellung des I-tetragonalen Gitters entwickelt: Durch Pyrolyse von BBr3− CH4-H2-Gemischen bei 1200 °C an Ta-Substraten entsteht ein borreiches tetragonales Borcarbid der Zusammensetzung B48B2C2 (Gitterkonstanten: a = 8,722 A and c = 5,080 A
Abstract: Zusammenfassung Das von Hoard et al. als “I-tetragonales Bor” bezeichnete B48B2 lasst sich in reiner Form nicht darstellen. Wir haben eine neue Methode zur reproduzierbaren Darstellung des I-tetragonalen Gitters entwickelt: Durch Pyrolyse von BBr3− CH4-H2-Gemischen bei 1200 °C an Ta-Substraten entsteht ein borreiches tetragonales Borcarbid der Zusammensetzung B48B2C2 (Gitterkonstanten: a = 8,722 A und c = 5,080 A ), wahrend durch Pyrolyse von BBr3N2H2-Gemischen bei 1400 °C an BN-Substraten ein borreiches tetragonales Bornitrid der Zusammensetzung B48B2N2 (Gitterkonstanten: a = 8,646 A und c = 5,127 A ) gebildet wird. In diesen tetragonalen BC- und BN-Phasen (Raumgruppe: P42/nnm) wird das instabile Gitter B48B2 durch Besetzung von Lucken im tetragonalen Ikosaedergerust durch Bor und C- bzw. N-Atome stabilisiert. Durch Einkristalluntersuchungen zur Bestimmung der absoluten Elektronendichte in den Lucken des Ikosaedergerusts konnten wir uber Fourier-Schnitte und durch Ausgleichsrechnungen die C- bzw. N-Atome und die B-Einzelatome auf den Zwischenikosaederplatzen lokalisieren und eine eindeutige Zuordnung vornehmen. Im Unterschied zum Strukturvorschlag von Hoard et al. fur das (theoretische) B48B2 werden die Ikosaederbrucken in ( 0 01 2 ) von C- bzw. N-Atomen gebildet.
TL;DR: In this article, it is suggested that elastic interactions across shared edges of neighbored Cu II polyhedra dominate in the first case, leading to all the "long axes" of the Jahn-Teller-distorted octahedra aligned along the tetragonal c axis and the "short axes"aligned along the a axes.
TL;DR: In this article, the results of an analysis of πO, π+ and π− photoproduction, using the very recent and accurate data of the π −/π+ ratio measured at Bonn, were reported.
TL;DR: In this paper, the authors investigated the glykosylation of steroid alcohols with cis-halogenoses in the presence of various silver salts and found that in many cases the silver salts of 2-, 3-, and 4-hydroxyalkanoic acids as well as of 1.3-and 1.4-dicarboxylic acids proved to be superior to the commonly used Ag2CO3 or Ag2O.
Abstract: Bei der Glykosylierung von Steroidalkoholen (u.a. 4 und 9–12, R == OH) mit cis-Halogenosen in Gegenwart verschiedener Silbersalze erwiesen sich die von 2-, 3-und 4-Hydroxy-carbonsauren sowie von 1.3- und 1.4-Dicarbonsauren den ublichen Salzen in vielen Fallen als uberlegen. Gute Ausbeuten (an 5, 7–12) wurden dann erhalten, wenn im Anion des Silbersalzes durch eine Nachbargruppenbeziehung die Bildung der 1-O-Acyl-glucose zugunsten der Glykosidbidung eingeschrankt ist. Die Reaktion verlauft in Diathylather am besten und ist besonders auch zur Glykosylierung von chemisch empfindlichen Alkoholen gut geeignet.
Studies on Glycoside Synthesis, IV. Novel Silver Salts in Glycoside Synthesis
The glykosylation of steroid alcohols (e.g. 4, and 9–12, R==OH) with cis-halogenoses in the presence of various silver salts was investigated. In many cases the silver salts of 2-, 3-, and 4-hydroxyalkanoic acids as well as of 1.3- and 1.4-dicarboxylic acids proved to be superior to the commonly used Ag2CO3 or Ag2O. Good yields (5, 7–12) were obtained in cases in which neighbouring group effects within the anion limit the formation of 1-O-acylglycoses in favour of glycoside formation. The reaction takes place most readily in diethyl ether and is well suited for the glycosylation of chemically sensitive alcohols.
TL;DR: Mesozoic sedimentary rocks in the basement of the volcanic islands of Lanzarote and neighboring Fuerteventura indicate that at least part of the Canary Archipelago is underlain by continental crust.
Abstract: Struthious and aepyornithoid eggshells from Tertiary calcareous sediments on Lanzarote prove the presence, until about 12 million years ago, of large flightless birds. The calcarenite horizon is recognized as an old land surface. Mesozoic sedimentary rocks in the basement of the volcanic islands of Lanzarote and neighboring Fuerteventura indicate that at least part of the Canary Archipelago is underlain by continental crust. Separation of the eastern Canaries from Africa raight have been by rifting, and a land connection might still have existed in the lower Pliocene.
TL;DR: It is difficult to imagine that on the level of orb-weaving cribellate spiders became ecribellate by reducing the cribellum, so these specialised webs must have developed on both sides independently and are the result of a convergent evolution.
Abstract: Orb-webs are highly developed and can be understood as the best technical solution of the problem how to place capture-threads in the most efficient and economical way. They are built by cribellate and ecribellate spiders. Phylogenetical relations between some families of Cribellate and Ecribellate cannot be ignored, but for some important reasons it is difficult to imagine that on the level of orb-weaving cribellate spiders became ecribellate by reducing the cribellum. Thus, these specialised webs must have developed on both sides independently and are the result of a convergent evolution. Steps leading from primitive use of threads for capturing insects to the typical and latter modified orb-webs of Cribellate and Ecribellate can be discerned.
TL;DR: In this article, the resonance absorption of CO (A 1 Π → X 1 Σ + ) fourth positive bands was used to excite CO molecules selectively into the ν′ = 0 and ν − − 1 vibrational levels of the A 1 − Π state.
TL;DR: In this article, a three-dimensional model of the thermosphere dynamics is developed in terms of the eigenfunctions of the atmospheric system, and a three dimensional model for the external heat inputs like solar XUV-radiation and corpuscular heating during geomagnetic storms is derived.
TL;DR: Two-dimensional time dependent diffusion model for phase delay between thermospheric density and temperature is proposed in this paper, where phase delay is defined as the delay between temperature and density.
Abstract: Two-dimensional time dependent diffusion model for phase delay between thermospheric density and temperature
TL;DR: The gewohnliche hexagonale Form of Tantalnitrid, eTaN (B35-Typ), geht bei 20 bis 100 kbar und 800 bis 960 °C in eine Hochdruckform ϑ-TaN(WC-Typ) uber.
Abstract: Die gewohnliche hexagonale Form von Tantalnitrid, e-TaN (B35-Typ), geht bei 20 bis 100 kbar und 800 bis 960 °C in eine Hochdruckform ϑ-TaN (WC-Typ) uber. Diese Form zeigt nach Abkuhlen und Druckentlastung bei Normalbedingungen eine Hohere Dichte und kleinere Ta−N-Abstande als die Niederdruckform e-TaN.
TL;DR: Histochemical precipitation of sodium and chloride in the apical region suggests that all types have basically the same function of salt absorption.
Abstract: The tracheal gills of 16 species of mayfly larvae were studied with regard to the chloride cells. The ephemerid chloride cells occur as two main types: single cells and cell complexes. The single chloride cells are characterized by deep tubular or slit-like infoldings of the apical cell membrane, whereas the chloride cell complexes show numerous intercellular channels resulting from cellular interdigitation at the basolateral side. According to the structural organization of the apices, the ephemerid chloride cells may be classified into caviform, coniform, bulbiform and filiform types. In the caviform type (single chloride cell), the apex retracts to form an apical cavity similar to teleost chloride cells. In the other types (chloride cell complexes), there is a progressive extension of the central cell apex into or beyond the cuticle in the form of cones, bulbs or filaments. The common feature of all types is the differentiation of the cuticle into thin porous plates or envelopes covering or surrounding the various forms of apices. Histochemical precipitation of sodium and chloride in the apical region suggests that all types have basically the same function of salt absorption. The population of the various types differs with the species. However, there seem to be some taxonomic regularities with respect to the families. No relation was found between the types of chloride cells and habitat of the species.