On the axisymmetric interaction of a rigid disc with a semi-infinite solid

An analytical treatment is presented for the determination of the response of a vertically-loaded disc embedded in a semi-infinite elastic medium. By means of Love's method of potential and a set of relaxed boundary conditions, the mixed boundary value problem is formulated as dual integral equations with the aid of Hankel transforms. On the reduction of the dual integral equations to a Fredholm integral equation which features a closed-form kernel, solutions to the inclusion problem are computed. In addition to including existing solutions for zero and infinite embedment as degenerate cases, the present analysis reveals a severe boundary-layer phenomenon which is apt to be of significance to this class of problems in general. As illustrations, numerical results on the load-displacement relation, the response of the embedding medium, as well as the contact load distribution are included.

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Résumé Une solution analytique est présentée pour déterminer la réponse d'un disque rigide horizontal chargé verticalement et enfoui dans un milieu semi infini élastique. En utilisant la méthode des potentiels de Love et en imposant un ensemble de conditions aux frontières de type mixte, le problème est formulé à l'aide d'une paire d'équations intégrales au moyen de la transformée d'Hankel. On réduit la paire d'équations intégrales à une simple équation intégrale de type Fredholm pour laquelle on obtient une expression analytique du kernel. En plus d'inclure les solutions classiques d'un disque enfoui à une profondeur nulle ou infinie, le présent travail révèle certains aspects de ce problème général d'interaction, aspects qui n'apparaissent pas nécessairement dans les études précédentes. Une méthode est exposée pour le traitement numérique des différentes intégrales rencontrées. Sont inclus, à titre d'exemples, la distribution de la contrainte verticale de contact, le ratio force-déplacement, et quelques caractéristiques concernant la réponse du milieu.

     

Doppler-free two-photon millimeter wave transitions in OCS and CHF3

Doppler-free two-photon rotational transitions J = 13<--<--11 and J = 12<--<--10 of OCS and J = 8<--<--6 and J = 7<--<--5 of CHF (3) were detected in the frequency range 134-156 GHz, using a novel, highly sensitive intracavity-jet technique. The sub-Doppler narrowing of the observed peaks (down to 40 kHz full width at half maximum as compared to 300 kHz of the Doppler width) demonstrates the potential of this new technique for high precision millimeter wave spectroscopy. The possibilities of the further reduction of the two-photon absorption line widths are considered.     

Results of prescribing Q-curvature on S n

Using a flow approach, generalizing previous results from Chen and Xu [12] and Ho [20], an existence result of prescribing Q-curvature on the even-dimensional standard sphere S ⁿ as a given positive function f was obtained under suitable assumptions on the Morse index of f. In this note, we prove a more general existence result by assuming only that f is positive somewhere.     

Folding simulations with novel conformational search method

A novel scheme for fast conformational search has been developed by combining the replica exchange method (REM) with the generalized effective potential concept. The new method, referred to Q-REM [S. Jang et al. Phys. Rev. Lett. 91, 058305 (2003)], is expected to provide a useful alternative to the conventional REM for effective conformational sampling of complex systems. The authors have performed folding simulations of the Trp-cage miniprotein using Q-REM. All atom level simulations with generalized Born solvent access-area solvation model show that successful folding can be observed with much smaller number of replicas in Q-REM compared to the conventional REM. It can be concluded that the new method has potential to significantly improve sampling efficiency, allowing simulations of more challenging systems.     

Scalar curvature of <Emphasis Type="Italic">QR</Emphasis>-submanifolds with maximal <Emphasis Type="Italic">QR</Emphasis>-dimension in a quaternionic projective space

In this paper we derive an integral formula on an n-dimensional, compact, minimal QR-submanifoldM of (p−1) QR-dimension immersed in a quaternionic projective space QP ^(n+p)/4. Using this integral formula, we give a sufficient condition concerning with the scalar curvature of M in order that such a submanifold M is to be a tube over a quaternionic projective space.     

Reaction of 2,2-dinitromalononitrile with arylalkenes

2,2-Dinitromalononitrile reacted with phenylethene and 1-phenylpropene through intermediate aci-nitromalononitrile ester and subsequent 1,3-dipolar cycloaddition of the second alkene molecule with formation of substituted 5-phenyltetrahydroisoxazole-3,3-dicarbonitriles. Reactions of 2,2-dinitromalononitrile with 2-phenylpropene or p-methoxyphenylethene resulted in the formation of 2-(1-aryl-2-nitroethyl)-2-nitromalononitriles. 1,1-Diarylethenes reacted with 2,2-dinitromalononitrile to give conjugated 1,1-diaryl-2-nitroethenes due to steric hindrances.     

Ceria-promoted oxygen reduction reaction in Pd-based electrocatalysts

PdCo-ceria electrocatalyst is synthesized on carbon support in a size of a few nm by colloid method. Enhanced oxygen reduction reaction (ORR) kinetics of PdCo is observed in the presence of ceria similarly as confirmed for PtCo-ceria in a half cell experiment. In addition, there appears a positive shift of the ORR onset potential of PdCo-ceria compared to PdCo while PtCo-ceria shows no such an apparent shift of onset potential. These effects of ceria on the ORR onset potential and the ORR kinetics are more remarkable as temperature increases. To get the most of oxygen storage and supply capacity of ceria, a high temperature proton exchange membrane fuel cell (PEMFC) is fabricated using PdCo-ceria as a catalyst at the cathode. Ceria effects on the ORR of PdCo-ceria catalyst are realized in the form of higher OCV and lower Tafel slope compared to PdCo catalyst in the PEMFC single cell performance. Enhancements in both ORR kinetics and ORR onset potential are very attractive features of ceria as a co-catalyst in the development of a non-Pt ORR electrocatalyst.     

Synthesis,Structural Characterisation and Stereochemical Investigation of Chiral Sulfur‐Functionalised N‐Heterocyclic Carbene Complexes of Palladium and Platinum

Palladium and platinum complexes containing a sulfur‐functionalised N‐heterocyclic carbene (S‐NHC) chelate ligand have been synthesised. The absolute conformations of these novel organometallic S‐NHC chelates were determined by X‐ray structural analyses and solution‐phase 2D ¹H–¹H ROESY NMR spectroscopy. The structural studies revealed that the phenyl substituents on the stereogenic carbon atoms invariably take up the axial positions on the Pd‐C‐S coordination plane to afford a skewed five‐membered ring structure. All of the chiral complexes are structurally rigid and stereochemically locked in a chiral ring conformation that is either (R_s,S,R)‐λ or (S_s,R,R)‐δ in both the solid state and solution.     

Electric conductivity of porous glass modified by oxides of bivalent cobalt, nickel, and copper

Multiply repeated operations of porous glass impregnation by aqueous solutions of bivalent cobalt, nickel, and copper nitrates followed by the thermal decomposition of the deposited salts provide a gradual accumulation of oxides in the carrying agent. In all cases, as the surface of glass open channels is filled with oxides, a section of substantial increase in conductance is detected, in which a tentative oxide monolayer is formed. Relations established between conductivity and its activation energy are treated on the basis of the conception of intervalence mechanism of electron transfer in the systems under consideration.