Observation of the C2H2-N2O van der Waals complex in the overtone range using CW-CRDS

A slit nozzle supersonic expansion containing C2H2 (246 sccm) and N2O (355 sccm) seeded into Ar (1260 sccm) is investigated using CW cavity ring-down spectroscopy, in the 1.5 μm range. The C2H2-N2O van der Waals complex is observed around the 2CH acetylenic band. Despite strong perturbations, 117 b-type lines are assigned. Their combined fit with published microwave data leads to new upper state and improved lower state rotational constants. The Lorentzian width of the assigned line profiles sets the mean lifetime to 1.6 ns. The rotational temperature is estimated to be 15 K from the comparison between observed and simulated spectra. © 2008 Elsevier B.V. All rights reserved.

Déficits immunitaires primaires: diagnostic, prise en charge, quelques perspectives.

Severe primary immunodeficiencies (PID) are rare; their global incidence is comparable to that of childhood leukemia; they include more than 100 different entities. Clinical manifestations are: unusually severe or frequent infections or infections that do not respond to adequate treatment; an increased risk of certain malignancies; sometimes auto-immune manifestations. Delayed diagnosis and management of PID can lead to severe and irreversible complications or to death. PID can become manifest only in the adult; in common variable immune deficiency, the median age at diagnosis is between the 2nd and the 3rd decade of life. PID are often transmitted genetically; recent progresses in molecular biology have allowed more precise and earlier, including antenatal, diagnosis. Molecular treatment of 3 infants with a severe immunodeficiency has recently been achieved in April 2000. Those progresses were mostly based on the study of immunodeficiency databases. We present here the work of a Belgian group specialized in PID; meetings have started in June 1997. This group establishes guidelines for the diagnosis and treatment of PID, adapted to the local situation. The elaboration of a national register of PID is also underway; this has to provide all guaranties of anonymity to patients and families. Such a register already exists at the European level; it has provided the basis for new diagnostic and therapeutic possibilities. The inclusion of Belgian data in this register should allow essential progresses essential for our patients.

Ab initio investigation of C2H2/X Van der Waals complexes (X=Noble gas, CO2, N2O)

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The C2H2-Ar van der Waals complex

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Investigation of acetylene-containing van der Waals complexes by cavity ring-down spectroscopy and ab initio calculations

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Quel dispositif utiliser pour la consultation d’une encyclopédie en ligne ?Impact des modalités d’interaction sur la performance et les processus cognitifs

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12C2H2-Ar van der Waals complex

New theoretical and experimental results on the acetylene-Ar van der Waals complex are presented and the literature is reviewed. New ab initio calculations at the MP2 level were performed using large basis sets with diffuse functions and taking into account the basis set superposition error. It was found that the structure of acetylene is not significantly altered by the complexation and that its vibrational frequencies are only slightly lowered. Finally, it was observed that the calculated properties of the complex (structure, vibrational spectrum, bond dissociation energy) are not sensitive to the structure imposed on acetylene. Experimentally, acetylene-Ar was produced in a supersonic expansion under experimental conditions corresponding to 9 K rotational temperature. Thanks to the performances of CW-CRDS detection, the Ka = 0 ← 1, 1 ← 0, and 2 ← 1 sub- bands of the v1 + v3 band could be recorded and resolved and most of their lines assigned. Upper-state rotational constants were fitted, however not including the upper Ka = 2 state, which shows K-doubling the opposite of the expected. The Lorentzian width of most line profiles sets the mean lifetime to some 7.5 ns. Local perturbations affecting line positions and/or line widths are demonstrated. Additional series of lines tentatively attributed to acetylene-Ar are discussed.© 2009 American Chemical Society.

Accurate ground-state potential energy surfaces of the C2H2–Kr and C2H2–Xe van der Waals complexes

Accurate ab initio intermolecular potential energy surfaces (IPES) have been obtained for the first time for the ground electronic state of the C 2H2-Kr and C2H2-Xe van der Waals complexes. Extensive tests, including complete basis set and all-electron scalar relativistic results, support their calculation at the CCSD(T) level of theory, using small-core relativistic pseudopotentials for the rare-gas atoms and aug-cc-pVQZ basis sets extended with a set of 3s3p2d1f1g mid-bond functions. All results are corrected for the basis set superposition error. The importance of the scalar relativistic and rare-gas outer-core (n.1)d correlation effects is investigated. The calculated IPES, adjusted to analytical functions, are characterized by global minima corresponding to skew T-shaped geometries, in which the Jacobi vector positioning the rare-gas atom with respect to the center of mass of the C2H2 moiety corresponds to distances of 4.064 and 4.229Å, and angles of 65.22° and 68.67° for C 2H2-Kr and C2H2-Xe, respectively. The interaction energy of both complexes is estimated to be -151.88 (1.817 kJ mol-1) and -182.76 cm-1 (2.186 kJ mol-1), respectively. The evolution of the topology of the IPES as a function of the rare-gas atom, from He to Xe, is also discussed. © 2012 Taylor and Francis.