Showing papers by "University of Bonn published in 1974"

Individualized configuration selection in CI calculations with subsequent energy extrapolation

Abstract: A configuration selection method for CI calculations is discussed and applied in which the energy lowering produced in a secular equation by the addition of a given test species to a series of dominant configurations is used as an ordering parameter. Configurations with energy lowerings below a given energy cut-off value are not included in the final secular equations but instead a method of estimating the combined effect of the neglected species on the corresponding non-selected CI results is developed. The influence of the choice of main configurations used in the selection process is given close examination as well as the importance of the MO basis employed in the treatment as a whole; in the latter case a non-iterative procedure for obtaining approximate natural orbitals for such calculations is suggested. The resulting configuration selection procedure is equally applicable to all types of electronic states in any nuclear geometry and the results of the associated CI calculations are seen to be essentially equivalent to a complete treatment in which all single- and double-excitation species with respect to aseries of dominant configurations in a given state are included.

Precision measurements of the nuclear magnetic dipole moments of6Li,7Li,23Na,39K and41K

Abstract: Using the atomic beam magnetic resonance method and using the technique of separated oscillatory fields in combination with the triple resonance method the ratiosgI/gJ of the stable alkali isotopes Li, Na and K in the2S1/2-ground state have been measured at magnetic fields of about 3 kOe. Frequency shifts analogous to the Bloch-Siegert-shift, expected from theory, were observed and eliminated by extrapolation to vanishing rf-field strength. The results, uncorrected for atomic diamagnetism, are:6Li:gI/gJ=−0.22356978(10)·10−37Li:gI/gJ=−0.59042719(10)·10−323Na:gI/gJ=−0.40184406(40)·10−339K:gI/gJ=−0.07088613 (6)·10−341K:gI/gJ=−0.03890837 (4)·10−3 Furthermore, the hyperfine structure splitting constants in the2S1/2-ground states have been determined. Using the most precise absolutegJ-values available so far one can calculate absolute values for the uncorrectedgI- factors. The results are:Δν/MHz −gI·1036Li: 228.2052590(30) 0.4476540 (3)7Li: 803.5040866(10) 1.1822130 (6)23Na: 1771.6261288(10) 0.8046108 (8)39K: 461.7197202(14) 0.14193489(12)41K: 254.0138720(20) 0.07790600 (8) By comparing the absolutegI- factors with measurements received by the NMR-method, the chemical shifts of the NMR-frequencies caused by the hydrate surrounding of the alkali ions in the NMR-probe are determined.

The Extraterrestrial UV-Background and the Nearby Interstellar Medium

Abstract: Recent measurements of the extraterrestrial UV- and EUV-radiation, and the various theoretical approaches used in explaining the measured features of these radiations are reviewed. Whereas the structures and intensities of extraterrestrial EUV-radiation are essentially undetermined up to now, the observations of the extraterrestrial UV-sky give a clear indication of the existence of neutral interstellar hydrogen within the solar system. The effects of solar radiation pressure, and of temporal variations and spatial asymmetries in the solar radiations, on the structure of the extraterrestrial Lα sky are investigated in detail, and the various attempts to derive interstellar parameters from the interpretation of the measured Lα intensities are discussed. From these discussions the local interstellar medium is established as a tenuous hot intercloud H i-medium. The amount of its relative motion against the solar system cannot be reliably fixed. Further activities concerning the measurement of extraterrestrial UV- and EUV-radiation features are suggested that may be highly valuable in clarifying the outstanding problems.

An example of unirational surfaces in characteristic p

Abstract: § 1. Let p be an odd prime number, and n a natural number such that n @ 0 (modp). Let X, denote the Fermat surface of degree n x~ + x~ + x~ + x,~ = 0 0 ) defined over a field k of characteristic p. Then Xn is a non-singular irreducible surface, which is rational only for n N 3, K 3 for n = 4, and of general type for n ~ 5. In this note, a surface X will be called unirational if its function field k(X) has a finite extension, which is a purely transcendental extension of dimension two over the constant field k. For the sake of simplicity, we assume that the constant field k is algebraically closed. Proposition 1. Suppose that there is a power q = pV o f p such that q----1 (modn). Then X , is unirational. Proof. (i) First let us consider the case n = q + 1. By an obvious change of coordinates, we can rewrite (t) as

The travelling salesman problem and a class of polyhedra of diameter two

Abstract: A class of polytopes is defined which includes the polytopes related to the assignment problem, the edge-matching problem on complete graphs, the multi-dimensional assignment problem, and many other set partitioning problems. Modifying some results due to Balas and Padberg, we give a constructive proof that the diameter of these polytopes is less than or equal to two. This result generalizes a result obtained by Balinski and Rusakoff in connection with the assignment problem.

Das tympanalorgan von Gryllus bimaculatus Degeer (saltatoria, gryllidae)

Abstract: Das Tympanalorgan von Gryllus bimaculatus Degeer liegt an der lateralen Wand der vorderen Trachee and schliest sich unmittelbar an das Subgenualorgan an. Es besteht aus 3 eng beieinanderliegenden Abschnitten: dem proximalen Absehnitt (10–12 Scolopidien), den Scolopidien des hinteren Tympanalnervs (10–12 Scolopidien) and einem distalen Absehnitt (35–40 Scolopidien). Ein Scolopidium des Tympanalorgans besteht aus folgenden Zellen: einer bipolaren Sinneszelle, die sich nach distal in einen Sinnesfortsatz mit einem Sinnescilium fortsetzt, einer oder zwei Gliazellen, einer proximalen Hullzelle, der Stiftzelle (= 1. Hullzelle), der Kappenzelle (= 2. Hullzelle) und der akzessorischen Zelle (= 3. Hullzelle). Das Sinnescilium ist mit einem langen, sich aufspaltenden Wurzelfaden im Sinnesfortsatz verankert. An der Cilienbasis befinden sich zwei Basalkorper. Die Spitze des Ciliums reicht in einen Stiftkopf, der wie bei alien hemimetabolen Insekten nicht massiv ist. Unterhalb des Stiftkopfes erweitert sich die Cilie zu einer Ciliendilatation, deren Zentrum elektronendichtes Material enthalt. Die Cilie verlauft in einem extrazellularen Raum, der durch Stutzstrukturen innerhalb der Stiftzelle, den Wandrippen, aufrecht gehalten wird. Das Organ hat an der lateralen Wand des Beines eine schmale Anheftungsstelle; die Verankerung in der Epidermis erfolgt uber die akzessorischen Zellen.

Changes of extent of neuro-vascular contacts and number of neuro-glial synaptoid contacts in the pituitary posterior lobe of dehydrated rats.

Abstract: The posterior lobe of the hypophysis consists of neurosecretory nerve fibres and glial cells, both abutting on the perivascular space of sinusoidal capillaries. Nerve fiberes and glial cells are connected with each other by a high number of synaptoid contacts. Several ultrastructural changes following dehydration have been described by other authors. This study presents the data of some morphometric investigations on normal and dehydrated rats. The relative extent of neuro-vascular contacts is not contstant; it increases significantly from 52 (±2.8)% in normal rats to 67(±1.2)% in rats with a dehydration time of 3 days. Correspondingly the extent of glio-vascular contacts is diminished. In addition, water-deprived animals show a clear increase in the number of neuro-glial synaptoid contacts with 3.1 (±0.4) per square unit nervous tissue compared to 2.1 (±0.3) per Square unit in untreated controls. These results indicate a dynamic motility of neuronal and glial elements depending on functional conditions, as was found for the external layer of the median eminence. Furthermore there seems to be a relationship between secretory activity and the number of neuroglial synaptoid contacts.

Darstellung silylierter Alkylen‐bisiminophosphorane und ihre Cyclisierung mit Phosphor(V)‐fluoriden

Abstract: Die Synthese neuartiger, silylierter Bisiminophosphorane des Typs Ph2P(NSi(CH3)3)(CH2)(n)PPh2(NSi(CH3)3) 2a, b und c mit n = 1, 2, 3 und des analog gebauten cyclischen Silins 5 erfolgt durch Umsetzung der betreffenden Alkylenbisphosphine mit Silylaziden. Die offenkettigen Vertreter 2a und b werden von atherischer HCl desilyliert; sie kondensieren – ebenso wie 5 – mit den Fluorphosphoranen PhxPF5–x(x = 0, 1) unter Fluorsilanabspaltung zu den ionischen, partiell fluorierten Diphosphazaphosphonium-Ringsystemen 7a, b und 8. Die Identifizierung und Charakterisierung der Reaktionsprodukte erfolgt vor allem durch 19F- und 31P-NMR-Spektroskopie. The Preparation of Silylated Alkylene-Bisiminophosphoranes and the Cyclisation with Phosphorus(V) Fluorides thereof New silylated bisiminophosphoranes of the type Ph2P(NSi(CH3)3)(CH2)n Ph2P(NSi(CH3)3) 2a, b and c (n = 1, 2, 3) and the similary structured cyclic siline 5 are prepared by reaction of the corresponding alkylene-bisphosphines with silylazides. Using etheric HCl, the opened chain compounds 2a and b, are desilylated; they undergo condensation reactions with fluorophosphoranes PhxPF5–x(x = 0, 1) – the same as 5 – splitting off fluorosilane forming the partially fluorinated ionic diphosphaza-phosphonium ring systems 7a, b and 8.

Hilbert modular surfaces and the classification of algebraic surfaces

Abstract: Introduction Around 1900 Hilbert, Hecke ([7]), Blumenthal ([2]) and others started the study of certain 2-dimensional complex spaces, which are closely related to the classification of special types of 2-dimensional abelian varieties. These complex spaces can easily be described. In fact, let n be a natural number, n > 1, which is square free and let K = Q q/n). Then, if o K is the ring of algebraic integers of K, the group SLz(oK) operates in a natural way on ~ • ~ and on ~ • ~ where ~ is the upper and ~ the lower half plane of C. The quotients of See • ~ and Jg x J g by the action of SL2(ov,) are the 2-dimensional complex spaces mentioned above. If the field K has a unit of negative norm, then the two actions on ~ • ~ and ~ • J g are isomorphic. This is true if n is a prime congruent 1 rood 4, the only case we shall consider in this paper. Therefore, from now on we assume that K= Q (l,/p), where p is a prime congruent 1 mod 4. The complex space Jg x .)~/SLz(oK) can be compactified by means of a finite number of points, called the cusps, to a compact 2-dimensional complex space. After resolving the cusps and also the quotient singularities on ~ x ~ / S L 2 (OK) , both in a canonical, explicit way, a nonsingular compact complex surface Y(R) is obtained, which in fact is an algebraic surface. The field of meromorphic (i. e. rational) functions on Y(p) is isomorphic to the field of meromorphic functions of • ~ / S L 2 (OK). On the other hand, although no complete classification of algebraic surfaces is known, there exists a rough classification in several classes (for most of which the surfaces contained in that class can be classified completely, at least in principle). In big outline this classification was already known to the italian school, but its precise formulation (this time also covering the non-algebraic case) and many of the proofs involved are due to Kodaira. Now the question considered in this paper is the following: where are the surfaces Y(p) to be placed in the rough classification of algebraic surfaces?

Zur Charakterformel gewisser Darstellungen halbeinfacher Gruppen und Lie-Algebren.

Abstract: Ist Gk eine universelle Chevalley-Gruppe fiber einem unendlichen K/Srper k der Charakteristik p 4: 0, so gibt es zu jedem dominanten Gewicht 2 des zugeh6rigen Wurzelsystems eine irreduzible, algebraische Darstellung von Gk zum h6chsten Gewicht 2. Deren (formaler) Charakter Zk(2) ist yon der Form Zk(2)---~a, a(2', 2)Z(2') mit 2' dominant und a(2', 2)e2g, wobei ):(2') der Charakter der irreduziblen Darstellung von G~ zum h6chsten Gewicht 2' ist. Nach Humphreys ([7]) gibt es eine (affine) Spiegelungsgruppe Wk, so dab a(2', 2)+0 nut ftir 2'e Wk.(2) m6glich ist. Dies wurde allerdings nur bewiesen, wenn p gr613er als die Coxeter-Zahl des Wurzelsystems ist, was wir yon nun an annehmen wollen. (Dank der Arbeit [4] ist diese Voraussetzung bei einem Teil der Ergebnisse aberflfissig, wenn der Typ ..4 nist.) Schreiben wir a(w, 2) statt a(w.(2), 2) ftir we Wk. Die Spiegelungsgruppe Wk definiert Kammern. Sind 2 und 2' dominante Gewichte, die im Innern derselben Kammer C liegen, so zeigen wir in Theorem 1, dab a(w, 2)=a(w, 2') ist. Schreiben wit dann a(w, C) statt a(w, 2). Wir k6nnen in zwei disjunkte Teilmengen Ca und Cb zerlegen und ftir ein dominantes Gewicht 2 e C die (endliche) Summe_ ~,~w~a(w, C) z(w.(2)) bilden. Dann zeigen wir, dab diese Summe ;(~(2) fiir 2e C, (Theorem 1) und gleich Null ffir 2e C b (Theorem 2) ist. Ftir jedes dominante 2 gibt es genau eine Kammer C mit 2e C,. Daher sagt Theorem 1: Kennen wir Zk(2) fiir je ein dominantes Gewicht 2 im Innern jeder Kammer, in der fiberhaupt ein dominantes Gewicht liegt, so kennen wir alle Zk(2). Theorem2 liefert uns Beziehungen zwischen verschiedenen a(w, C) fiJr festes C. Ganz ~ihnliche Aussagen gelten ffir g~:, die Lie-Algebra von Gr und deren irreduziblen Darstellungen, die yon h/Schsten Gewichtsvektoren erzeugt werden. Man ersetzt oben )~(2') durch den Charakter der ,,gr613ten\" Darstellung zum h6chsten Gewicht 2' und W k durch eine Untergruppe der Weylgruppe. Diese verschiedenen Ergebnisse werden einheitlich dargestellt. Dazu betrachten wir statt gr deren einhfillende Algebra U und ersetzen Gk durch Uk = Ue| wobei Ue die Kostantsche Z-Form von U ist. Die betrachteten endlichdimensionalen Uk-Moduln sind auch Gk-Moduln; sie sind genau dann far Gk einfach, wenn sie es fiir Us sind.

Non-empirical SCF and Cl Study of the ground and excited states of thioformaldehyde

Abstract: Ab initio SCF and Cl calculations are reported for ground and various low-lying Rydberg and valence excited states of thioformaldehyde H2CS. A double-zeta basis of near Hartree-Fock quality is employed in this work and the importance of polarization functions is also assessed. The calculations indicate uniformly larger CX bond lengths in this system than for H2CO in the corresponding electronic states; they also lind potential minima for H2CS non-planar nuclear conformations in the (n,π*) and (π,π*) excited states but in each case the calculated inversion barriers are seen to be smaller than those encountered in formaldehyde. The vertical transition energies to the various excited states studied are also found to be significantly smaller in H2CS than in H2CO but the order of electronic states is concluded to be virtually identical for the two systems. The lowest-lying excited states are the 3,1(n,π*) species calculated at 1.84 and 2.17 eV respectively; the first two allowed transitions are indicated to be the Rydberg species (n,sR) and (n,pxR) at 5.83 and 6.62 eV. These are followed by the two allowed transitions σ → π* and π → π* at 7.51 and 7.92 eV respectively, both well below the first ionization limit in H2CS. The much smaller splitting between the 3,1(π,π*) species in H2CS than in H2CO is attributed to the relatively diffuse charge distribution of the sulfur atom compared to that of oxygen.

Immunohistochemical demonstration of a CRF-associated neurophysin in the external zone of the rat median eminence.

Abstract: In picric acid-formalin fixed, paraplast embedded median eminence sections from normal and bilaterally adrenalectomized rats, the amount of “Gomori-positive” neurosecretory material and the amount of protein, cross reacting against a porcine neurophysin-II antiserum were determined. In normal rats, “Gomori-positive” substances and neurophysin were confined to the internal zone of the median eminence. After adrenalectomy, however, “Gomori-positive” granules and a neurophysin-like protein also became apparent in the external zone. Their amount increases, if the animals are treated with DOCA from the 15th to the 21st day after the operation. The distribution of the neurophysin-like protein in the external zone is similar to that of the “Gomori-positive” granules. Since the granules are regarded as a morphological correlate of the corticotropin-releasing factor (CRF) it is assumed, that the protein, appearing in the external zone after adrenalectomy and cross-reacting against the neurophysin antiserum is a CRF-associated neurophysin. For this substance the name “CRF-neurophysin” is proposed.

Botrydial, ein Sesquiterpen‐Antibiotikum aus der Nährlösung des Pilzes Botrytis cinerea

Abstract: Aus der Nahrlosung des Pilzes Botrytis cinerea wurden das antibiotisch wirksame Botrydial (3) und sein Dihydroderivat (1) isoliert. Durch eine Folge chemischer Umwandlungen, verbunden mit der Anwendung spektroskopischer Methoden, insbesondere einer detaillierten Analyse der NMR-Spektren, wurden ihre Konstitutionsformeln abgeleitet. Botrydial liegt ein bicyclisch nicht-isoprenoides Sesquiterpenskelett zugrunde. Botrydial, a Sesquiterpene Antibiotic from the Culture Solution of the Fungus Botrytis cinerea The antibiotic botrydial (3) and its dihydro derivative (1) were isolated from the culture solution of the fungus Botrytis cinerea. Their structural formulas were elucidated by means of a series of chemical transformations together with the application of spectroscopic methods, especially a detailed analysis of the n.m.r. spectra. The basic skeleton of botrydial is a bicyclic, non-isoprenoid sesquiterpene system.

AB initio calculation of vertical transition energies of the C2H2 molecule

Abstract: Various ab initio SCF and Cl treatments are reported for the acetylene molecule in ground and excited states at its fixed linear equilibrium geometry. The results speak in favor of the former analysis of the vacuum UV absorption spectra of C 2 H 2 given by Wilkinson according to which above the XC state an allowed transition to a linear upper state (XD) and two allowed transitions with broad bands (XE and XF) to non-linear upper states are present. The calculated order and spacing of the excited states does not support the new analysis given by Jungen according to which only one allowed transition (XF) and a forbidden one to a linear upper state (XD) should appear between 1250 and 1360 A.

Pyrolysis mass spectrometric studies on nucleic acids

Abstract: Two different mass spectrometric techniques have been used to analyse the products resulting from Curie-point pyrolysis of nucleic acids: low voltage ionization quadrupole mass spectrometry and high resolution field ionization mass spectrometry. The spectra obtained with both techniques are in good agreement with one another. As already indicated by the low resolution spectra, the high resolution spectra proved that most of the peaks originate from the carbohydrate moiety of the nucleic acid. Micrograms of DNA/RNA can be distinguished very easily by use of these key fragments, although the bases themselves are not found. Some significant pyrolysis mechanisms are proposed.

Accuracy and limitations of the pseudopotential method

Abstract: Two model potential approximations to the pseudopotential operator are discussed. Suitable simple expressions for an atomic model potential with angular projection are given, the parameter values of which can be fitted to reproduce the Rydberg series rather accurately. Calculations on atomic states with several valence electrons from the first two and a half rows of the periodic system show that energies of chemical interest are accurate to 0.0–0.2 eV. The pseudo-wave functions have an accuracy of a few %.