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  • American Institute of Physics (AIP)  (4)
  • Blackwell Publishing Ltd  (4)
  • American Chemical Society (ACS)
  • 1990-1994  (8)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    The Cs(7P)+H2→CsH+H reaction. I. Angular scattering measurements by Doppler analysis (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 434-444 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Cs(7P)+H2→CsH (X 1Σ+) (v‘=0,J‘)+H reaction has been studied in a crossed-beam experiment, with electronic excitation of Cs atoms and laser-induced fluorescence detection of CsH products. The Doppler technique has been applied to determine the center of mass angular scattering probability of CsH products, for all rotational levels between 1 and 14 (in v‘=0) and for various values of the collision energy between 0.03 and 0.13 eV. We have used two complementary arrangements of the analysis laser beam: With a "parallel'' arrangement (the laser beam is along the collision axis), the shape analysis of fluorescence profiles leads directly to the angular scattering probability but experimental constraints limit the range of measurements; with a "perpendicular'' arrangement (the laser beam is perpendicular to the collision plane), fluorescence profiles are symmetrical and "forward'' contributions cannot be separated from "backward'' ones. However, extensive shape analyses have been performed with this perpendicular arrangement, since the direction of scattering was determined earlier by recording several profiles with the parallel arrangement. For the title reaction, it is shown unambiguously that, in the center of mass, CsH products scatter preferentially at small angle, in the forward direction with respect to the Cs initial velocity. The angular scattering probability varies with the collision energy but is independent of the rotational level of the product molecule (thus of its recoil velocity). These results are compatible with the harpooning mechanism which was suggested for the reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459543
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  • 2
    Electronic Resource
    Electronic Resource
    The Cs(7P)+H2→CsH+H reaction. II. Rotationally resolved total cross sections (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3347-3360 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Cs(7P)+H2→CsH(X 1Σ+)(v‘=0,J‘)+H harpooning reaction has been studied in a crossed-beam experiment, with electronic excitation of Cs atoms and laser-induced fluorescence detection of CsH products performed in a coherent saturation regime. Measurements of reactive cross sections have been achieved as a function of two parameters: The collision energy Ec (0.015≤Ec≤0.15 eV) and the rotational quantum number J‘ of CsH products (0≤J‘≤16, in v‘=0). For Ec=0.09 eV, the total reactive cross sections corresponding to the two 7P fine structure levels of Cs are σ(Cs(7P1/2)+H2)=4.2×10−16 cm2 and σ(Cs(7P3/2)+H2)=10−16 cm2. These cross sections are much smaller than expected for a harpooning reaction. This is interpreted from ab initio potential energy and quantal dynamics calculations which show that the efficiency of the photochemical reaction (Cs atoms in the 7P state) is limited by the quenching processes associated with the underlying potential energy surfaces connected with Cs atoms in the 6S, 6P, 5D, and 7S states. From the present measurements, one deduces that the rate of these quenching processes is larger than 90%. The rotational distributions of products in v‘=0 measured at two collision energies (Ec=0.045 and 0.09 eV) are close to "prior'' statistical distributions, with the same "surprisal.'' The energy dependence of rotationally resolved cross sections (J‘ fixed, Ec variable) confirms the reaction thresholds and shows that there is no potential barrier higher than 0.015 eV on the entrance valley and the exit valley of the reactive system; it is in agreement with the dependence predicted by hemiquantal dynamical calculations performed in the frame of a harpooning model. The uncertainty on the measurement of absolute cross sections is larger than 70%, but of the order of 20% for relative cross sections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460840
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  • 3
    Electronic Resource
    Electronic Resource
    Transient Overmodification of Collagen I and III in a Hyperplastic Callus from a Patient with Osteogenesis Imperfecta Type IV (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 580 (1990), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1990.tb17987.x
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  • 4
    Electronic Resource
    Electronic Resource
    Ab initio study of the potential energy surfaces of doublet valence and Rydberg states of FCO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3973-3980 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Multireference configuration interaction calculations (MRD-CI) were carried out in order to obtain the bending and stretching potential energy curves of several low-lying electronic states of the fluoroformyl radical FCO. The study of interactions between valence and Rydberg states as well as that of the dissociative behavior is included in the investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467515
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  • 5
    Electronic Resource
    Electronic Resource
    Ab initio investigation of the vibrational structure of absorption and emission spectra of FCO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3981-3988 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of an ab initio study of the vibrational structure of several electronic spectral systems of FCO are presented. An interpretation of hitherto recorded spectra, as well as a prediction of features of yet unobserved electronic transitions is given. The absorption spectra observed in the uv spectral region are ascribed to the transitions involving the first excited states of 2A' and 2A‘ character. The emission spectrum obtained by Toby and Toby [J. Phys. Chem. 85, 4071 (1981)] is assigned to the transition X 2A'←2 2A‘. Reassignment of some observed vibrational bands is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467516
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  • 6
    Electronic Resource
    Electronic Resource
    An alternative method for paediatric anaesthetic induction: critical incidents and historical antecedents (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Pediatric anesthesia 3 (1993), S. 0 
    Details
    ISSN: 1460-9592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This prospective study was undertaken to examine the safety and to review the historical antecedents of an alternative method of paediatric anaesthetic induction other than halothane by mask. Two-thousand and five ASA I, II and III patients, 1 month-16 years of age initially received 70% N2O in O2 via a flavour-scented mask for 1–3 min, until adequate sedation was achieved. Venous cannulation was then undertaken, followed by an intravenous induction with thiopentone, and either atracurium or suxamethonium. The anaesthetist noted the occurrence of specific critical incidents during induction: excitement, coughing, vomiting, airway obstruction, laryngospasm, bradycardia for age, hypotension and/or hypoxaemia. The frequencies of all eight specific critical incidents on induction were extremely low in all ages. The studied alternative method of paediatric anaesthetic induction may be safer and more applicable in diverse clinical settings than a conventional halothane mask induction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9592.1993.tb00058.x
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  • 7
    Electronic Resource
    Electronic Resource
    Adhesin regulatory genes within large, unstable DNA regions of pathogenic Escherichia coli: cross-talk between different adhesin gene clusters (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 11 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The uropathogenic Escherichia coli strain 536 possesses two large, unstable DNA regions on its chromosome, which were termed pathogenicity islands (pais). Deletions of pais, which occur with relatively high frequency in vitro and in vivo, lead to avirulent mutants. The genetic determinants for production of haemolysin (Hly) and P-related fimbriae (Prf) are located in one of these islands. Deletion of this pathogenicity isiand (paill) not only removes the hly- and prf-specific genes, but also represses S fimbriae (Sfa), although the sfa genes of this virulence factor are not located on paill. We have identified two regulatory genes, prfB and prfl, of the prf gene cluster that are homologous to the sfa regulatory genes staB and SfaC, respectively. Mutations in sfaB and sfaC that inhibit transcription of the major fimbrial subunit gene sfaA were complemented by the homologous prf genes, suggesting communication between the two fimbrial gene clusters in the wild-type strain. Chromosomal mutagenesis of the two prf regulators in strain 536 repressed transcription of sfaA, detected by Northern hybridization and a chromosomal sfaA-lacZ fusion. In addition, haemagglutination assays measured a lower level of S fimbriae in these mutants. Expression of the cloned prf regulators in trans reversed the effect of the mutations; furthermore, constitutive expression of prfB or prfl could also overcome the repression of S fimbriae in a strain that had lost the pathogenicity islands. Virulence assays in mice established that the prf mutants were less virulent than the wild-type strain. The results demonstrate that cross-regulation of two unlinked virulence gene clusters together with the co-ordinate loss of large DNA regions significantly influences the virulence of an extraintestinal E. coli wild-type isolate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00336.x
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  • 8
    Electronic Resource
    Electronic Resource
    Sulphide tolerance and adaptation in the California killifish, Fundulus parvipinnis, a salt marsh resident (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 42 (1993), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hydrogen sulphide is a toxicant naturally produced in hypoxic marine sediments, hydrocarbon and brine seeps and hydrothermal vents. The California killifish, a salt marsh resident, is remarkably tolerant of sulphide. The 50% lethal concentration is 700 μM total sulphide in 96 h, and 5 mM in 8 h (determined in flow-through, oxygenated sea water). Killifish exposed to sulphide produce thiosulphate which accumulates in the blood. The cytochrome c oxidase (a major site of toxicity) of the killifish is 50% inhibited by 〈1 μM sulphide. Killifish liver mitochondria are poisoned by 50–75 μM sulphide but can oxidize 10–20 μM sulphide to thiosulphate. Sulphide causes sulphhaemoglobin formation (and impairment of oxygen transport) at 1–5 mM in vitro and to a small extent at 2 mM in vivo. Killifish blood neither catalyses sulphide oxidation significantly nor binds sulphide at environmental (low) sulphide concentrations. Exposure to 200 μM and 700 μM sulphide over several days causes significant increases in lactate concentrations, indicating shift to anaerobic glycolysis. However, individuals with the most lactate die. In terms of diffusible H2S, the killifish can withstand concentrations two to three orders of magnitude greater than would poison cytochrome c oxidase. The high sulphide tolerance of the killifish, particularly of concentrations typical of salt marshes, can be explained chiefly by mitochondrial sulphide oxidation. Sulphide tolerance and mitochondrial sulphide oxidation in the killifish have a constitutive basis, i.e. do not diminish in fish held in the laboratory in sulphide-free water for 1–2 months, and are improved by prior acclimation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1993.tb00381.x
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