Showing papers by "University of Bonn published in 1978"

Applicability of the multi-reference double-excitation CI (MRD-CI) method to the calculation of electronic wavefunctions and comparison with related techniques

Abstract: Implementation of a multi-reference double-excitation CI (MRD-CI) method is discussed and its results are compared with those of related techniques. This approach employs a configuration selection procedure to order the various generated species according to their energy-lowering capability and then uses an energy extrapolation procedure based on perturbation theory to obtain suitably accurate estimates of the eigenvalues of the entire MRD-CI space. By employing this selection procedure it is possible to test from 2000 to 4000 symmetry-adapted functions (SAF's) per second of CPU time on an IBM 370–168 system, thereby allowing one to apply the energy extrapolation quite conveniently to CI spaces consisting of several hundred thousand species. By systematically increasing the number of reference configurations in the MRD-CI it is clear that the limit of a full CI can be approached and as a result such a computational procedure appears to be generally valid for any type of electronic state and for any nuclea...

An Analysis of the Greedy Heuristic for Independence Systems

Abstract: The worst case behaviour of the greedy heuristic for independence systems is analyzed by deriving lower bounds for the ratio of the greedy solution value to the optimal value. For two special independence systems, this ratio can be bounded by 1/2, for two other independence systems, it converges with increasing problem size to zero. The main theorem states that for every independence system ( E , F ) the ratio is bounded by I/k, k such that ( E , F ) can be represented as the intersection of k matroids.

Elastic Electron Scattering from He 3 and He 4 at High Momentum Transfer

Abstract: Experimental values of $^{3}\mathrm{He}$ ($^{4}\mathrm{He}$) elastic structure functions up to momentum transfer ${q}^{2}=4.0 (2.4)$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ are presented. They are compared to calculations using three- and four-body wave functions and to asymptotic models.

On the Computational Complexity of Integer Programming Problems

Abstract: Recently much effort has been devoted to determining the computational complexity for a variety of integer programming problems. In this paper a general integer programming problem is shown to be NP-complete; the proof given for this result uses only elementary linear algebra. Complexity results are also summarized for several particularizations of this general problem, including knapsack problems, problems which relax integrality or non-negativity restrictions and integral optimization problems with a fixed number of variables.

Moufang plane and octonionic quantum mechanics

Abstract: It is shown that the usual axioms of one-particle Quantum Mechanics can be implemented with projection operators belonging to the exceptional Jordan algebraJ 8 3 over real octonions. Certain lemmas on these projection operators are proved by elementary means. Use is made of the Moufang projective plane. It is shown that this plane can be orthocomplemented and that there exists a unique probability function. The result of successive, compatible experiments is shown not to depend on the order in which they are performed, in spite of the non-associativity of octonion multiplication. The algebra of observables and the action of the exceptional groupF 4 is studied, as well as a possible relation with the color group SU(3) and quark confinement.

Ab initio MRD-CI study of ethane: The 14–25 eV PES region and Rydberg states of positive ions

Abstract: Ab initio calculations of the MRD-CI type are reported for various states of the C 2 H 6 + ion in two different nuclear geometries and the results are compared with the experimentally observed ethane PES in the 14–25 eV region. The calculated vertical IP values for ionization out of the 1e u , 2a 2u and 2a 1g MO's respectively agree well with the locations of the three ionization maxima in this spectral range. The analogous findings for excitation out of the relaxed ionic ground state find several relatively low-lying species which occupy a 2pσ* MO in addition to states resulting from simple ionization of the neutral molecule. A number of Rydberg states are also calculated at the relaxed-ion geometry, from which results it is determined that the quantum defects for such species are from 0.40–0.45 units smaller than for their counterparts in neutral systems; these findings are clearly consistent with a decrease in the core penetrability of the Rydberg electron as the effective charge is increased to Z = 2.

Fermentative Metabolism of Hydrogen-evolving Chlamydomonas moewusii

Abstract: The anaerobic metabolism of Chlamydomonas moewusii under both light (160 lux) and dark conditions has been examined using manometric and enzymic techniques. During anaerobiosis starch is broken down to glycerol, acetate, ethanol, CO(2), and H(2). The release of CO(2) and H(2) comes to an end when the starch pool is depleted.There are only slight differences in the ratio of the end products of fermentation between light and dark metabolism. In the light, glycerol production is diminished and H(2) evolution is enhanced, whereas the production rate of all other end products generally does not change.

Coulomb effects in three-body reactions with two charged particles

Abstract: We present the details of a novel approach to the treatment of Coulomb effects in atomic and nuclear reactions of the three-body type in which two of the particles are charged. Based on three-body integral equations the formalism allows the practical calculation of elastic, inelastic, rearrangement, and breakup processes with full inclusion of the Coulomb repulsion or attraction in a mathematically correct way. No restrictions need to be made concerning the form of the short-range interactions between the three pairs. A particular virtue of our method lies in the fact that it corroborates, and gives precise meaning to, the intuitively anticipated conception of how to describe such reactions.

Effects of anticonvulsant drugs on thyroid hormones in epileptic children.

Abstract: ummary Long-term therapy with valproate, phenytoin (diphenylhydantoin, DPH), primidone, carbamazepine, and combinations of these produced considerable alterations in the thyroid hormonal state in epileptic children (n = 125). These consist of decreases in protein-bound iodine (PBI), thyroxin (T4), free T4, triiodothyronine (T3), and to a lesser extent in thyrotropin hormone (TSH). In carbamazepine and antiepileptic combination therapy, statistically significant increases of total cholesterol were confirmed. The changes described are dose dependent for valproate, DPH, and carbamazepine. They are based on a displacement of thyroxin and T3 from their protein-binding sites, as well as on a more rapid conversion and metabolism of T4 and T3. In the TRH test, marked TSH stimulation resulted in 8% of our 50 tested patients, suggesting a hypothyroid state. The lack of increase of basic TSH in the majority of the treated children could result from a hypothalamic effect of the anticonvulsant drugs that might result in a TRH inhibition. Furthermore, in a greater number of the treated children it must be assumed that a latent form of hypothyroidism exists. RESUME Chez l'enfant epileptique le traitement anticonvulsif chronique entraine: avec le valproate une diminution significative de la concentration sdrique de T4 et de T3; avec le diphenylhydantoine, une diminution des PBL T4, FT4, et T3; avec la primidone une diminution des PBL T4, et FT4; avec la carbamazepine une diminution des PBI T4, FT4, et T3 et une augmentation significative du cholesterol serique. La combinaison de ces differ-ents produits provoque la diminution la plus importante des PBL T4, et FT4, tandis que la concentration du cholesterol serique augmente statistiquement. Ces diverses modifications sont dependantes des dosages en valproate, DPH, et carbamazepine. La concentration serique de TSH n'est pas augmentee chez la plupart des sujets traites avec les difftrents produits anticonvulsifs. Cependant. chez environ 5% des enfants traites (n = 125) on observe une valeur du niveau de base de TSH legerement augmentee. Les tests TRH (n = 50) entrainent chez environ 8% des sujets une elevation marquee de TSH. Chez 3 sujets on observe un hypothroidisme hypothalamique secondaire. Chez un autre sujet les modifications dans le systeme des hormones thyroi'diennes doivent etre interpretees comme un hypothyroidisme primaire. Ces effets des produits anticonvulsifs peuvent etre en rapport avec un deplacement competitif des hormones thyroidiennes de leur liaison aux proteines plasma-tiques, une acceleration du “turnover” de T4, et une dventuelle inhibition de la liberation hypothalamique de TRH. RESUMEN En ninos epilepticos la administracion prolongada de valproato produce una reduccion estadistica de las concentraciones sericas de T4 y T3. El tratamiento prolongado de difenilhidantoina disminuye significa-tivamente el PBI, T4, FT, y T3. La administracion aislada de primidona resulta en una disminucion significativa del PBI, T4, y FT4 mientras que el tratamiento con carbamazepina conduce a una reduccion estadistica de las concentraciones de PBI, T4, FT4, y T3 produciendo, a la vez, un aumento significativo del colesterol serico. La combinacion de medica-mentos provoca las mayores reducciones de PBI, T4, y FT4, a la vez que el colesterol serico aumenta estadisticamente. Los citados resultados dependen de las dosis de valproato, DPH, y carbamazepina. El TSH basico no aumento en la mayoria de los enfermos tratados con diversas medicaciones anticonvulsivas. Sin embargo en el 5% de los ninos tratados (n = 125) se registraron valores basicos de TSH ligeramente mas elevados. Los tests de TRH (n = 50) produjeron, en el 8% de los enfermos, un marcado aumento de la TSH. En 3 pacientes se observo un hipotiroidismo hipotalimico secundario. En otro enfermo los cambios en el sistema hormonal tiroideo deben interpretarse como un hipotiroidismo primario. Los efectos de las medicaciones anticonvulsivas deben ser producidas por un desplazamiento competitive de las hormonas tiroideas de sus puntos de union a las proteinas plasmaticas, por una produccion mas rapida de T4 y por una posible inhibicion de la liberacion hipotalamica de TRH. ZUSAMMENFASSUNG Valproat, Diphenylhydantoin, Primidon, Carbamaze-pin und die antikonvulsiven Kombinationsbehand-lungen filhren bei Kindern zu erheblichen Beeintrach-tigungen des Schilddrusenhormonsystems. Sie bestehen in Erniedrigungen des proteingebundenen Jodes, des Thyroxins, des freien Thyroxins, des Trijodthyronins und im geringerem Umfange des thyreotropen Hormones. Unter Cabamazepinbehandlung und antikonvulsiver Kombinationsbehandlung werden statistisch signifikante Erhohungen des Gesamtcho-lesterins festgestellt. Die beschriebenen Veranderungen sind bei Valproat, Diphenylhydantoin und Carbamaze-pin dosisabhangig. Sie beruhen auf einer Verdran-gung des Thyroxins und des Trijodthyronins aus ihren EiweiBbindungen, sowie in einer rascheren Konver-sion und Metabolisierung von T3 und T4. Im TRH-Test ergaben sich bei 8% der Patienten starke TSH Stimulationseffekte, so das das Vorliegen einer Hypo-thyreose als gesichert erscheint. Die Nichterhohung der basalen TSH Konzentrationen in der uberwiegen-den Mehrzahl der mit Antikonvulsiva behandelten Kinder konnte auf einer hypothalamen Wirkung der Antikonvulsiva beruhen, die die TRH-Wirkung auf die Hypophyse inhibieren wtirde. Bei einem grOBerem Prozentsatz unserer mit Antikonvulsiva behandelten Kinder und Jugendlichen muB eine leichte latente hypothyreote Stoffwechsellage angenommen werden.

Atomic transition probabilities from the relativistic pseudopotential approach

Abstract: The 'relativistic pseudopotential approach' is applied to the calculation of electric-dipole transition probabilities in the valence shell of heavy atoms. An adequate transition operator is derived. The lowest spin-allowed and spin-forbidden transitions of the heavier group I and II elements and a series of higher transitions of Ca I and II, Cs, I, Ba I and II, Au I and Hg I are calculated. The influence of the core-valence correlation is investigated with Hameed's core-polarisation correction.

Changes in the level of octopine during the escape responses of the scallop,Pecten maximus (L.)

Abstract: 1. The activities of octopine dehydrogenase (ODH) and α-glycerophosphate dehydrogenase (GDH) were determined in several tissues ofPecten maximus. The ratios of ODH/GDH were 13 for the adductor muscle, 9 for the mantle and 3 for the digestive gland and the gill. Therefore, the main pathway for the glycolytic re-oxidation of NADH seemed to be via the formation of octopine. 2. During burst activity the level of arginine phosphate in the adductor muscle declined concurently with an increase in arginine. Little octopine, however, accumulated until the animals were exhausted; the main increase in octopine concentration took place during the beginning of the subsequent rest period. 3. It is concluded that inPecten maximus there is no “flare-up” of glycolysis during burst activity. Instead the increased demand for ATP is met by the breakdown of arginine phosphate. Octopine accumulates later, possibly due to a stimulation of glycolysis brought about by the activation of phosphofructokinase by AMP at low levels of arginine phosphate.

Evidence for interactions between the energy-dependent transport of sugars and the membrane potential in the yeast Rhodotorula gracilis (Rhodosporidium toruloides)

Abstract: A membrane potential (inside negative) across the plasma membrane of the obligatory aerobic yeastRhodotorula gracilis is indicated by the intracellular accumulation of the lipid-soluble cations tetraphenylphosphonium and triphenylmethylphosphonium. The uptake of these ions is inhibited by anaerobic conditions, by uncouplers, by addition of diffusible ions, or by increase of the leakiness of the membrane caused by the polyene antibiotic nystatin. The membrane potential is strongly pH-dependent, its value increasing with decreasing extracellular proton concentration. Addition of transportable monosaccharides causes a depolarization of the electrical potential difference, indicating that the H+-sugar cotransport is electrogenic. The effect on the membrane potential is enhanced by increasing the sugar concentration. The half-saturation constants of depolarization ford-xylose andd-galactose were comparable to those of the corresponding transport system for the two sugars. All agents that depressed the membrane potential inhibited monosaccharide transport; hence the membrane potential provides energy for active sugar transport in this strain of yeast.