Atom-atom potential in rotational line broadening for molecular gases: Application to CO lines broadened by CO,N2, O2 and NO

Linewidths in CO-CO, CO-N₂, CO-C₂ and CO-NO collisions have been calculated using an improved potential for atom-atom interactions in addition to the first-order terms of the electrostatic interaction. The energy parameters characterizing the Lennard-Jones potential have been estimated previously from second virial coefficients. Overall agreement between calculated and experimental linewidths (particularly for CO-O₂ mixtures for which the electrostatic contributions are weak) is thus obtained without any adjustable parameters. It is concluded that the atom-atom potential describes the angular dependence of the short-range forces in molecular collisions fairly adequately.     

On the Neighbor Sum Distinguishing Index of Planar Graphs

Let c be a proper edge coloring of a graph with integers . Then , while Vizing's theorem guarantees that we can take . On the course of investigating irregularities in graphs, it has been conjectured that with only slightly larger k, that is, , we could enforce an additional strong feature of c, namely that it attributes distinct sums of incident colors to adjacent vertices in G if only this graph has no isolated edges and is not isomorphic to C₅. We prove the conjecture is valid for planar graphs of sufficiently large maximum degree. In fact an even stronger statement holds, as the necessary number of colors stemming from the result of Vizing is proved to be sufficient for this family of graphs. Specifically, our main result states that every planar graph G of maximum degree at least 28, which contains no isolated edges admits a proper edge coloring such that for every edge of G.     

Hydrogen CARS thermometry in a high-pressure H2–air flame. Test of H2 temperature accuracy and influence of line width by comparison with N2 CARS as reference

This work describes a further step towards the determination of the temperature accuracy of H₂ Q-branch CARS (Coherent Anti-Stokes Raman Scattering) at high pressure with regard to the influence of the H₂ line widths. In laminar steady H₂/air flames in the pressure range 1–15 bar and at fuel-rich conditions with stoichiometries between two and four, quasi-simultaneous temperature measurements were performed with H₂ and N₂ CARS. The temperature values deduced from H₂ CARS are in good agreement with the reference temperature from N₂ CARS. The influence of different line-width contributions on the accuracy of H₂ Q-branch thermometry was investigated in detail. Received: 10 April 2001 / Revised version: 22 May 2001 / Published online: 18 July 2001     

A small molecule promotes mitochondrial fusion in Mammalian cells

Mitochondrial dynamics: An image-based screen identified a small molecule, M1, that specifically promotes the fusion of fragmented mitochondria and protects cells from mitochondrial-fragmentation-associated cell death. Mechanistic studies revealed that M1 shifts the mitochondrial dynamic balance towards fusion.     

2‐Distance Coloring of Sparse Graphs

For graphs of bounded maximum average degree, we consider the problem of 2‐distance coloring, that is, the problem of coloring the vertices while ensuring that two vertices that are adjacent or have a common neighbor receive different colors. We prove that graphs with maximum average degree less than and maximum degree Δ at least 4 are 2‐distance ‐colorable, which is optimal and improves previous results from Dolama and Sopena, and from Borodin et al. We also prove that graphs with maximum average degree less than (resp. , ) and maximum degree Δ at least 5 (resp. 6, 8) are list 2‐distance ‐colorable, which improves previous results from Borodin et al., and from Ivanova. We prove that any graph with maximum average degree m less than and with large enough maximum degree Δ (depending only on m) can be list 2‐distance ‐colored. There exist graphs with arbitrarily large maximum degree and maximum average degree less than 3 that cannot be 2‐distance ‐colored: the question of what happens between and 3 remains open. We prove also that any graph with maximum average degree can be list 2‐distance ‐colored (C depending only on m). It is optimal as there exist graphs with arbitrarily large maximum degree and maximum average degree less than 4 that cannot be 2‐distance colored with less than colors. Most of the above results can be transposed to injective list coloring with one color less.     

Measurement of hadronic production of the χ1++(3507) and the χ2++(3553) through their radiative decay to Jϕ

The _χ1⁺⁺(3507) and the _χ2⁺⁺(3553) states have been observed in the Goliath spectrometer at the CERN SPS in 185 GeV/cπ^?-Be collisions. Their radiative decays contribute 27.7% (for the χ₁⁺⁺) and 12.8% (for the χ₂⁺⁺) to $\text{J}\text{?}$ production. At this energy, their cross sections are 65±19 nb and 96±29 nb, respectively     

Vibrational dephasing effects and motional narrowing in the isotropic Raman Q branch of HD

Important motional narrowing has been previously experimentally observed by Dion and May in the isotropic Raman Q branch of pure gaseous HD in the fundamental vibrational band. A recent theoretical calculation of the present authors, in good agreement with these experiments, has shown that for pure HD only rotational mechanisms are efficient. In this paper, an infinite order treatment of the vibrational dephasing effects for HD perturbed by rare gases indicates an important role of these last effects in the broadening of the individual lines (particularly in the 0–2 band) leading to a significant decrease of the motional narrowing in the resulting band profile at high density.     

A master equation for S(q,ω) leading to the hydrodynamic regime for simple fluids

A master equation relating the coherent and incoherent dynamical structure factors S(q, ω) and S_S(q, ω) is introduced on the basis of physical arguments suggested by previous theories. It is shown that, once S_S(q, ω) and the first six moments of S(q, ω) are known, the resulting expression for S(q, ω) contains the correct hydrodynamic regime as well as the free particle behaviour. The relationships thus introduced between the transport coefficients and the molecular quantities are compared to the experimental data for liquid argon. Molecular dynamics data are also well reproduced.