998 resultados para H(1S)-H(1S) COLLISIONS


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The coadsorption of NO and O-2 on Ag(110) surface has been studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and in situ Raman spectroscopy. The existence of oxygen enhances the adsorption of NO by forming the NOx species, that is, NO2 and NO3, and the NO in turn as a promotor facilitates the cleavage of the dioxygen bond, forming the surface atomic oxygen species having the same spectral characteristics as those produced using oxygen at high pressure. The oxygen species generated by the interaction is composed of two parts. One is produced directly by the decomposition of surface NO-O-2 complex at ca 625 K, which raised an O 1s feature at 530.5 eV and is absent at ca 800 K, while the another with an O 1s binding energy of 529.2 eV emerges at higher temperatures and shows similar properties as the reported gamma-state oxygen which bound tightly on restructured silver surface. The exposure to NO and O-2 causes noticeable changes in the morphology of the Ag(110) surface and the flat terraces superseded by small (ca 0.1 mu m) pits, and particles with typical diameters of a few micrometres were formed at elevated temperatures. (C) 1999 Elsevier Science B.V. All rights reserved.

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Three optically active Schiff-base ligands have been prepared by condensation of 2-hydroxyacetophenone with (IR,2R)-(-)-1,2-diaminocyclohexane, (1S,2S)-(-)1,2-diphenylethylenediamine or R-(+)-2,2'-diamino-1,1'-binaphthalene, respectively. The products have been characterized by their IR, H-1- and C-13-NMR spectra.

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The first calculation of triangular flow ν3 in Au+Au collisions at √sNN = 200A GeV from an event-by-event (3 + 1) d transport+hydrodynamics hybrid approach is presented. As a response to the initial triangularity Ie{cyrillic, ukrainian}3 of the collision zone, ν3 is computed in a similar way to the standard event-plane analysis for elliptic flow ν2. It is found that the triangular flow exhibits weak centrality dependence and is roughly equal to elliptic flow in most central collisions. We also explore the transverse momentum and rapidity dependence of ν2 and ν3 for charged particles as well as identified particles. We conclude that an event-by-event treatment of the ideal hydrodynamic evolution startingwith realistic initial conditions generates the main features expected for triangular flow. © 2010 The American Physical Society.

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MAPKKK dual leucine zipper-bearing kinases (DLKs) are regulators of synaptic development and axon regeneration. The mechanisms underlying their activation are not fully understood. Here, we show that C. elegans DLK-1 is activated by a Ca(2+)-dependent switch from inactive heteromeric to active homomeric protein complexes. We identify a DLK-1 isoform, DLK-1S, that shares identical kinase and leucine zipper domains with the previously described long isoform DLK-1L but acts to inhibit DLK-1 function by binding to DLK-1L. The switch between homo- or heteromeric DLK-1 complexes is influenced by Ca(2+) concentration. A conserved hexapeptide in the DLK-1L C terminus is essential for DLK-1 activity and is required for Ca(2+) regulation. The mammalian DLK-1 homolog MAP3K13 contains an identical C-terminal hexapeptide and can functionally complement dlk-1 mutants, suggesting that the DLK activation mechanism is conserved. The DLK activation mechanism is ideally suited for rapid and spatially controlled signal transduction in response to axonal injury and synaptic activity.

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A study of proton-proton collisions in which two b hadrons are produced in association with a Z boson is reported. The collisions were recorded at a centre-of-mass energy of 7TeV with the CMS detector at the LHC, for an integrated luminosity of 5:2 fb-1. The b hadrons are identified by means of displaced secondary vertices, without the use of reconstructed jets, permitting the study of b-hadron pair production at small angular separation. Differential cross sections are presented as a function of the angular separation of the b hadrons and the Z boson. In addition, inclusive measurements are presented. For both the inclusive and differential studies, different ranges of Z boson momentum are considered, and each measurement is compared to the predictions from different event generators at leading-order and next-to-leading-order accuracy. Copyright CERN.

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By analyzing measured infrared absorption of pure CH4 gas under both "free" (large sample cell) and "confined" (inside the pores of a silica xerogel sample) conditions we give a demonstration that molecule-molecule and molecule-surface collisions lead to very different propensity rules for rotational-state changes. Whereas the efficiency of collisions to change the rotational state (observed through the broadening of the absorption lines) decreases with increasing rotational quantum number J for CH4-CH4 interactions, CH4-surface collisions lead to J-independent linewidths. In the former case, some (weak) collisions are inefficient whereas, in the latter case, a single collision is sufficient to remove the molecule from its initial rotational level. Furthermore, although some gas-phase collisions leave J unchanged and only modify the angular momentum orientation and/or symmetry of the level (as observed through the spectral effects of line mixing), this is not the case for the molecule-surface collisions since they always change J (in the studied J=0-14 range).

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Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field ΦFV=(η0,η+) that couples the first and third generation quarks (q1, q3) via a Lagrangian term LFV=ξ13ΦFVq1q3. These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2fb-1 collected by the Collider Dectector at Fermilab II detector in pp̄ collisions at s=1.96TeV are analyzed for evidence of the MxFV signature. For a neutral scalar η0 with mη0=200GeV/c2 and coupling ξ13=1, ∼11 signal events are expected over a background of 2.1±1.8 events. Three events are observed in the data, consistent with background expectations, and limits are set on the coupling ξ13 for mη0=180-300GeV/c2. © 2009 The American Physical Society.

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This paper describes the first measurement of b-quark fragmentation fractions into bottom hadrons in Run II of the Tevatron Collider at Fermilab. The result is based on a 360pb-1 sample of data collected with the CDF II detector in pp̄ collisions at s=1.96TeV. Semileptonic decays of B̄0, B-, and B̄s0 mesons, as well as Λb0 baryons, are reconstructed. For an effective bottom hadron pT threshold of 7GeV/c, the fragmentation fractions are measured to be fu/fd=1.054±0.018(stat)-0.045+0.025(sys)±0. 058(B), fs/(fu+fd)=0.160±0.005(stat)-0.010+0.011(sys)-0.034+0.057(B), and fΛb/(fu+fd)=0.281±0.012(stat)-0.056+0.058(sys)-0.087+0.128(B), where the uncertainty B is due to uncertainties on measured branching ratios. The value of fs/(fu+fd) agrees within one standard deviation with previous CDF measurements and the world average of this quantity, which is dominated by LEP measurements. However, the ratio fΛb/(fu+fd) is approximately twice the value previously measured at LEP. The approximately 2σ discrepancy is examined in terms of kinematic differences between the two production environments. © 2008 The American Physical Society.

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This study utilized the latest computing techniques to analyze the driver's cab of a railroad vehicle colliding with deformable objects. It explored the differences between a collision with a deformable object and a collision with a rigid object. It also examined the differences between a collision with a large simple shaped object and a collision with a life-like object. Tools of analysis included vehicle dynamics analysis and finite element analysis.

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Using thermosetting epoxy based conductive adhesive films for the flip chip interconnect possess a great deal of attractions to the electronics manufacturing industries due to the ever increasing demands for miniaturized electronic products. Adhesive manufacturers have taken many attempts over the last decade to produce a number of types of adhesives and the coupled anisotropic conductive-nonconductive adhesive film is one of them. The successful formation of the flip chip interconnection using this particular type of adhesive depends on, among factors, how the physical properties of the adhesive changes during the bonding process. Experimental measurements of the temperature in the adhesive have revealed that the temperature becomes very close to the required maximum bonding temperature within the first 1s of the bonding time. The higher the bonding temperature the faster the ramp up of temperature is. A dynamic mechanical analysis (DMA) has been carried out to investigate the nature of the changes of the physical properties of the coupled anisotropic conductive-nonconductive adhesive film for a range of bonding parameters. Adhesive samples that are pre-cured at 170, 190 and 210°C for 3, 5 and 10s have been analyzed using a DMA instrument. The results have revealed that the glass transition temperature of this type of adhesive increases with the increase in the bonding time for the bonding temperatures that have been used in this work. For the curing time of 3 and 5s, the maximum glass transition temperature increases with the increase in the bonding temperature, but for the curing time of 10s the maximum glass transition temperature has been observed in the sample which is cured at 190°C. Based on these results it has been concluded that the optimal bonding temperature and time for this kind of adhesive are 190°C and 10s, respectively.

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The coagulation and fibrinolytic systems are linked by the thrombin-thrombomodulin complex which regulates each system through activation of protein C and TAFI, respectively. We have used novel assays and techniques to study the enzymology and biochemistry of TAFI and TAFIa, to measure TAFI activation in hemophilia A and protein C deficiency and to determine if enhancing TAFI activation can improve hemostasis in hemophilic plasma and whole blood. We show that TAFIa not TAFI attenuates fibrinolysis in vitro and this is supported by a relatively high catalytic efficiency (16.41μM-1s-1) of plasminogen binding site removal from fibrin degradation products (FDPs) by TAFIa. Since the catalytic efficiency of TAFIa in removing these sites is ~60-fold higher than that for inflammatory mediators such as bradykinin it is likely that FDPs are a physiological substrate of TAFIa. The high catalytic efficiency is primarily a result of a low Km which can be explained by a novel mechanism where TAFIa forms a binary complex with plasminogen and is recruited to the surface of FDPs. The low Km also suggests that TAFIa would effectively cleave lysines from FDPs during the early stages of fibrinolysis (i.e. at low concentrations of FDPs). Since individuals with hemophilia suffer from premature fibrinolysis as a result of insufficient TAFI activation we quantified TAFI activation in whole blood from hemophilic subjects. Both the rate of activation and the area under the TAFI activation time course (termed TAFIa potential) was determined to be reduced in hemophilia A and the TAFIa potential was significantly and inversely correlated with the clinical bleeding iii phenotype. Using a novel therapeutic strategy, we used soluble thrombomodulin to increase TAFI activation which improved the clot lysis time in factor VIII deficient human plasma and hemophilic dog plasma as well as hemophilic dog blood. Finally, we briefly show in a biochemical case study that TAFI activation is enhanced in protein C deficiency and when afflicted individuals are placed on Warfarin anticoagulant therapy, TAFI activation is reduced. Since TAFIa stabilizes blood clots, this suggests that reducing TAFI activation or inhibiting TAFIa may help restore blood flow in vessels with pathological thrombosis.