Beugung am Kegel elliptischen Querschnitts und die Sommerfeldsche Lösung des Halbebenenproblems

Übersicht In dieser Arbeit wird die Beugung am Kegel elliptischen Querschnitts behandelt. Wir leiten zwei Greensche Funktionen ab, die der Dirichlet- bzw. der Neumann-Bedingung auf dem Kegel genügen und die Ausstrahlungsbedingung erfüllen. Das Randwertproblem wird zurückgeführt auf die Lösung eines zweiparametrigen Eigenwertproblems mit zwei gekoppelten Laméschen Differentialgleichungen. Wir analysieren insbesondere die Beugung einer ebenen Welle an der sektorförmigen Fläche. Im Grenzfall eines Sektoröffnungswinkels von 180° gehen die Reihenentwicklungen unter Zuhilfenahme eines speziellen Gegenbauerschen Additionstheorems und einer erzeugenden Funktion für Besselfunktionen mit ganzzahligem und halbzahligem Index über in die Sommerfeldsche Lösung des Halbebenenproblems.

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Diffraction by an elliptic cone and Sommerfeld's half-plane solution

Contents In this article we examine the diffraction by an elliptic cone. We derive two Green's functions satisfying the Dirichlet-resp. Neumann-condition on the boundary of the cone. The boundary value problem is reduced to a two-parametric eigenvalue problem with two coupled Lamé equations. We analyse the diffraction of a plane wave by a plane angular sector. In the limiting case of a sector angle of 180° the series expansions pass — using a special form of Gegenbauer's addition theorem and the generating function for Bessel functions with integral and half-integral indices — into Sommerfeld's half-plane solution.

     

The effect of core modelling on the self-force and self-energy of a dislocation

A verification example is solved using a core model recently introduced in a FEM approach to dislocation dynamics. The core model is compared to the more accepted cut-off procedures. It is demonstrated that these procedures give the correct self-force if the cut-off distance is selected properly. The cut-off procedures do however have some grave weaknesses. These limit their usefulness to a restricted number of problems.     

Carbachol, an acetylcholine receptor agonist, enhances production in rat aorta of 2-arachidonoyl glycerol, a hypotensive endocannabinoid

Orphanin FQ/nociceptin binds with high affinity to the orphan opioid receptor-like/K-3 (ORL1/KOR-3) clone, and stimulates feeding. The present study demonstrated that antisense oligodeoxynucleotides directed against either exons 1, 2 or 3 of the ORL1/KOR-3 clone reduced orphanin FQ/nociceptin-induced hyperphagia. A missense probe was ineffective. Naltrexone dose-dependently reduced orphanin FQ/nociceptin-induced hyperphagia. These data suggest that the receptor responsible for orphanin FQ/nociceptin-induced hyperphagia is encoded by the ORL1/KOR-3 clone.     

Studies on the interactions of metal oxides and Na2 SO4 at 1100 and 1200 K in oxygen

The interaction of different metal oxides such as Co₃O₄, NiO, Al₂O₃, Cr₂O₃, Fe₂O₃ and SiO₂ with Na₂SO₄ at a temperature of 1100 and 1200 K in flowing oxygen has been studied. The thermogravimetric studies for each system were carried out as a function of Na₂SO₄ in the mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis and the morphologies of the reaction products were characterized using metallography and scanning electron microscopy (SEM). The formation of products was also investigated by thermodynamic computation of free energies of the reactions and the study of relevant equilibrium phase diagrams. The soluble species in the aqueous solutions of the reaction products were determined quantitatively using atomic absorption spectrophotometry. The high temperature interaction products usually contain a 3-phase structure namely, Na₂O·M₂O _x , M₂O _x and metal sulphide and/or metal sulphate. The formation of Na₂O·M₂O _x depends upon the solid state solubility of metal oxide in the molten salt at high temperatures. Under limited solubility conditions Na₂O·M₂O _x is invariably formed, but as soon as this condition is relaxed the oxide. M₂O _x , precipitates and forms a separate phase.     

Interactions of histaminergic and serotonergic neurons in the hypothalamic regulation of prolactin and ACTH secretion

Serotonergic and histaminergic neuronal systems are both involved in mediation of the stress-induced release of the pituitary hormones prolactin (PRL) and ACTH. We investigated the possibility of an interaction between serotonin (5-HT) and histamine (HA) in regulation of PRL and ACTH secretion in conscious male rats. Animals were pretreated systemically with antagonists to 5-HT1, 5-HT2 or 5-HT3 receptors prior to intracerebroventricular (icv) administration of HA. The 5-HT1 + 2 receptor antagonist methysergide prevented and the 5-HT2 receptor antagonist LY 53857 attenuated the HA-induced PRL release while the 5-HT3 receptor antagonist ondansetron had no effect on this response. None of the three 5-HT receptor antagonists affected the ACTH response to HA. Specific blockade of HA synthesis by alpha-fluoromethylhistidine or blockade of postsynaptic HA receptors by icv infusion of the H1 receptor antagonist mepyramine or the H2 receptor antagonist cimetidine inhibited the PRL response to 5-HT or to the 5-HT precursor 5-hydroxytryptophan (5- HTP) given in combination with the 5-HT reuptake inhibitor fluoxetine (Flx). Blockade of the histaminergic system had no effect on the ACTH response to serotonergic stimulation. The H3 receptors are inhibitory HA receptors. Systemic pretreatment with the H3 receptor agonist R(alpha)methylhistamine, or the H3 receptor antagonist thioperamide had no effect on the hormone response to activation of the serotonergic system by 5-HTP plus Flx. We conclude that the serotonergic and histaminergic neuronal systems interact in their stimulation of PRL secretion, but not in their stimulation of ACTH secretion. This interaction involves serotonergic 5-HT1 and 5-HT2 receptors and histaminergic H1 and H2 receptors. Furthermore, the previously observed inhibitory effect of the H3 receptor agonist R(alpha)methylhistamine on stress-induced PRL and ACTH release seems not to be exerted by activation of presynaptic H3 receptors located on serotonergic neurons but rather on histaminergic neurons.     

Synthesis of enantiomerically pure 1-O-phosphocholine-2-O-acyl-octadecane and 1-O-phosphocholine-2-N-acyl-octadecane

This is the first report on the chemical synthesis of enantiomerically pure R- or S-1-O-phosphocholine-2-O-acyl-octadecanes and R- or S-1-O-phosphocholine-2-N-acyl-octadecanes. From a structural point of view these phospholipids are intermediates between phosphatidylcholine and sphingomyelin. The synthesis of these model compounds is based on R- or S-1.2-O-isopropylidene-glyceraldeyde for chain elongation in a Wittig reaction with pentadecane-triphenylphosphine bromide. The resulting 1.2-O-isopropylidene-octadec-3-en is converted to R- or S-1.2-octadecanediol by catalytic hydrogenation of the double bond and by acidic removal of the isopropylidene protecting group. Tritylation of R- or S-1.2-octadecanediol results in the general intermediates R- or S-1-O-trityl-2-hydroxy-octadecane. These are the key intermediates for the synthesis of the phosphatidylcholine- or sphingomyelin-like end products. R- or S-1-O-phosphocholine-2-O-acyl-octadecane is obtained from the tritylated intermediates via benzylation in position 2, acidic detritylation and conversion of the R- or S-1-hydroxy-2-benzyl-octadecanes to the respective phosphocholines via the phosphoethanolamines. Catalytic hydrogenolysis of the benzyl group results in R- or S-1-O-phosphocholine-2-hydroxy-octadecane, which is converted to the phosphatidylcholine-like end products by acylation. R- or S-1-O-phosphocholine-2-N-acyl-octadecane is obtained from the tritylated intermediate by conversion of the R- or S-2-hydroxy group into the N-phthalimido group, which is achieved by inversion of the configuration using the Mitsunobu reaction with phthalimid. After acidic detritylation, the product is converted to the respective S- or R-1-O-phosphocholine derivative in a similar sequence of reactions. The phthalimido group is converted to the 2-amino group, and acylation results in the sphingomyelin-like end products.     

A benchmark on the calculation of kinetic parameters based on reactivity effect experiments in the CROCUS reactor

Measurements in the CROCUS reactor at EPFL, Lausanne, are reported for the critical water level and the inverse reactor period for several different sets of delayed supercritical conditions. The experimental configurations were also calculated by four different calculation methods. For each of the supercritical configurations, the absolute reactivity value has been determined in two different ways, viz.: (i) through direct comparison of the multiplication factor obtained employing a given calculation method with the corresponding value for the critical case (calculated reactivity: ρ_calc); (ii) by application of the inhour equation using the kinetic parameters obtained for the critical configuration and the measured inverse reactor period (measured reactivity: ρ_meas). The calculated multiplication factors for the reference critical configuration, as well as ρ_calc for the supercritical cases, are found to be in good agreement. However, the values of ρ_meas produced by two of the applied calculation methods differ appreciably from the corresponding ρ_calc values, clearly indicating deficiencies in the kinetic parameters obtained from these methods.     

Automated estimation of rock fragment distributions using computer vision and its application in mining

Size distribution of rock fragments obtained from blasting and crushing in the mining industry has to be monitored for optimal control of a variety of processes before reaching the final grinding, milling and the froth flotation processes. Whenever feasible, mechanical sieving is the routine procedure to determine the cumulative rock weight distribution on conveyor belts or free falling off the end of transfer chutes. This process is tedious and very time consuming, even more so if a complete set of sieving meshes is used. A computer vision technique is proposed based on a series of segmentation, filtering and morphological operations specially designed to determine rock fragment sizes from digital images. The final step uses an area-based approach to estimate rock volumes. This segmentation technique was implemented and results of cumulative rock volume distributions obtained from this approach were compared to the mechanical fragment distributions. The technique yielded rock distribution curves which represents an alternative to the mechanical sieving distributions.