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  • 1
    Electronic Resource
    Electronic Resource
    A state-selected study of the ion–molecule reactions O+(2D,2P)+H2O (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 928-933 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-selected absolute cross sections for H2O+ and OH+ formed by the O+(2D,2P)+H2O reactions have been measured in the center-of-mass collision energy (Ec.m.) range of (approximate)0.10–30 eV. The charge transfer cross sections for O+(2D)+H2O are significantly higher than those for O+(4S)+H2O. This observation is attributed to the increased number of accessible exothermic product channels for O+(2D)+H2O. While the H2O+ cross sections for O+(2P)+H2O are comparable to those from O+(4S)+H2O at Ec.m.≥1 eV, the H2O+ cross sections for O+(2P)+H2O at Ec.m.〈1 eV are substantially lower than those for O+(4S)+H2O. The lower H2O+ cross sections observed for O+(2P)+H2O are rationalized as due to further dissociation of excited charge transfer H2O+ ions and/or the efficient competition of the OH++OH product channel. The cross sections for OH+ from O+(2D,2P)+H2O are significantly greater than those from O+(4S)+H2O. The majority of OH+ ions from O+(2D,2P)+H2O are associated with exothermic channels corresponding to the formation OH+(X 3Σ−,1Δ,A 3Π)+OH. The comparison of the sum (σT) of the cross sections for H2O+ and OH+ from O+(4S)+H2O to those from O+(2D)+H2O and O+(2P)+H2O shows that σT's for O+(4S)+H2O and O+(2P)+H2O are comparable, whereas the σT values for O+(2D)+H2O are greater than those for O+(4S)+H2O and O+(2P)+H2O. The σT values are found to conform with the 1/Ec.m. dependence at low Ec.m.'s, indicating that the ion–dipole interaction plays an important role in the formation of the long-lived collision complexes. The high cross sections for H2O+ and OH+ from O+(2D,2P)+H2O observed here suggest that these reactions should be included in the simulation of the H2O+ and H3O+ ion density data obtained in space-borne mass spectrometric experiments. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473172
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  • 2
    Electronic Resource
    Electronic Resource
    Absolute state-selected total cross sections for the ion–molecule reactions O+(4S,2D,2P)+H2(D2) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 564-571 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Absolute total cross sections for the state-selected reactions of O+(4S,2D,2P)+H2 (D2) have been measured in the center-of-mass collision energy (Ec.m.) range of 0.02–12 eV. The cross sections for OH+ (OD+) from O+(2D)+H2 (D2) are slightly higher than those from O+(4S)+H2 (D2), whereas the OH+ (OD+) cross sections from O+ (2P)+H2 (D2) are (approximate)40% lower than those from O+(4S)+H2 (D2) and O+ (2D)+H2 (D2). At Ec.m.〈0.5 eV, the total cross sections for OH+ (OD+) from O+ (4S)+H2 (D2) and O+(2D)+H2 (D2) are in accord with those predicted by the Langevin–Gioumousis–Stevenson model. Significantly higher cross sections are observed for H+ (D+) and H2+ (D2+) from O+(2D)+H2 (D2) and O+(2P)+H2 (D2), as compared to those from O+(4S)+H2 (D2). The exothermic nature of the O+(2D,2P)+H2 (D2) charge transfer collisions accounts for the high cross sections observed for H2+ (D2+). While the H+ (D+) ions observed in the O+(4S)+H2 (D2) reaction are identified with the H+ (D+)+O+H channel, the H+ (D+) ions from the reactions involving O+(2D) and O+(2P) are associated mostly with the H+ (D+)+OH (OD) channel, the formation of which obeys the spin-conservation rule. The comparison of the sum (σT) of cross sections for OH+ (OD+), H2+ (D2+), and H+ (D+) from O+(4S)+H2 (D2) to those from O+(2D)+H2 (D2) and O+(2P)+H2 (D2) shows that the σTs for O+(4S)+H2 (D2), O+(2D)+H2 (D2), and O+(2P)+H2 (D2) at Ec.m.〈0.5 eV are comparable. At Ec.m.〉0.5 eV, the σTs for O+(2P)+H2 (D2) are greater than those for O+(2D)+H2 (D2), which in turn are greater than those for O+(4S)+H2 (D2). This observation is attributed to the increase in the number of accessible product channels for reactions involving the excited O+(2D) and O+(2P) reactant ions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473395
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  • 3
    Electronic Resource
    Electronic Resource
    A state-selected study of the ion–molecule reactions O+(4S,2D,2P)+N2 (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1373-1381 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Absolute state-selected cross sections for the reactions O+(4S,2D,2P)+N2→N2++O, NO++N, and N++NO (and/or N++N+O) have been measured in the center-of-mass collision energy (Ec.m.) range of 0.06–40 eV employing the differential retarding potential method and the O+(2D) and O+(2P) ion state-selection schemes we developed recently. Charge transfer is the overwhelming product channel for the O+(2D)+N2 and O+(2P)+N2 reactions. Contrary to the results of previous experiments, the charge transfer cross sections for O+(2P)+N2 are found to be 30%–100% greater than those for O+(2D)+N2. This observation suggests that N2 is an excellent quenching gas for O+(2D,2P). While the Ec.m. dependencies for the cross sections of NO+ from O+(4S)+N2 and O+(2D)+N2 are similar, exhibiting a broad maximum in the Ec.m. range of 1.5–8 eV, the cross section for NO+ from O+(2P)+N2 is found to decrease as Ec.m. is decreased. The N+ signal observed in the O+(4S)+N2 reaction is attributed to the formation of N++N+O. The pathway of O++N2→N++NO to generate N+ is strongly suggested as the major channel in the reactions of O+(2D,2P)+N2, as evidenced by the observation of N+ well below the thermochemical thresholds of O+(2D,2P)+N2→N++N+O. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474087
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  • 4
    Electronic Resource
    Electronic Resource
    A differential retarding potential method for improving ion-beam kinetic energy resolution (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3724-3728 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a differential retarding potential (DRP) method for improving the kinetic energy resolution of a reactant ion beam for scattering experiments. This method allows ion-molecule reaction absolute total cross-section measurements to be performed down to thermal energies using the simple electrostatic aperture ion lenses of a tandem quadrupole mass spectrometric ion-molecule reaction apparatus, even though the reactant ions are formed originally with a broad kinetic energy distribution. To illustrate the principle of the DRP method, examples are given for its application to reactant ion beams prepared in an electron impact ion source and in an ion-molecule reaction ion source. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145217
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  • 5
    Electronic Resource
    Electronic Resource
    State selection of O+(4So,2Do,2Po) using resonance dissociative charge transfer of He+(Ne+, Ar+)+O2 and radio frequency multipole ion guide techniques (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2871-2878 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: By controlling the collision energies for dissociative charge transfer collisions of He+(Ne+,Ar+) +O2 in a rf octopole ion guide gas cell, and by applying appropriate effective ion trapping potentials to the rf octopole ion guide, we show that state-selected O+(4So), O+(2Do), and O+(2Po) reactant ion beams with high purities and usable intensities can be prepared for scattering experiments. This experimental scheme, which makes possible the enrichment of an ionic species with a lower kinetic energy distribution in a rf multipole ion guide, should be useful for state selection of other excited atomic ions by using appropriate dissociative charge transfer or dissociative photoionization processes. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145571
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  • 6
    Electronic Resource
    Electronic Resource
    Dissipation mechanisms in pendulums and their implications for gravitational wave interferometers (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 544-553 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a precise test of the dissipation dilution effect in the transverse wire mode quality factors in pendulums. Several excess loss mechanisms are diagnosed in detail, with special attention paid to dissipation from sliding friction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148692
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  • 7
    Electronic Resource
    Electronic Resource
    Nonconservative Ostwald ripening of dislocation loops in silicon (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2956-2958 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the effects of the proximity of the surface on the ripening behavior of dislocation loops in preamorphized silicon. Starting from well-defined initial conditions, we have varied the location depth of the loops by successive chemical removal of surface layers and measured changes of the size–distribution function during subsequent annealing by means of transmission electron microscopy. Our results show that the amount of Si atoms bound in the loops is not conserved during annealing and that the loop location depth has a prominent effect on the ripening kinetics. Both these observations prove the nonconservative nature of Ostwald ripening of dislocation loops near wafer surfaces. In addition, we observed different ripening kinetics for annealing in vacuum and in Ar which show that different boundary conditions at the surface are established during annealing in these two ambients. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122642
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  • 8
    Electronic Resource
    Electronic Resource
    PREPARATION OF SYNAPTOSOMES AND VESICLES WITH SODIUM DIATRIZOATE (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Synaptosomes were prepared from rat brain on a continuous gradient of sodium diatrizoate and compared with synaptosomes obtained on a discontinuous sucrose gradient. The yield of synaptosomal protein using diatrizoate was double that obtained with sucrose. No significant differences in quality between the two preparations were found based on measurement of: β-glucuronidase, RNA polymerase, 2′,3′-cyclic nucleotide 3′-phosphohydrolase, total and Na+, K+ -ATPase, acetylcholinesterase, lactic acid dehydrogenase, glucose utilization, and serotonin uptake. Electron microscopy showed the vesicles in the diatrizoate synaptosomes to be better preserved. Vesicles prepared on diatrizoate segregated into two distinct bands which differed in electron microscopic appearance and enzyme activity. The less dense vesicles were smaller, had much higher Mg2+ -ATPase activity, and a lower content of acetylcholinesterase than the more dense vesicles. The less dense vesicle preparation was very homogeneous morphologically, free of myelin and mitochondria, and contained occasional organelle fragments and double membrane structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1974.tb10746.x
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  • 9
    Electronic Resource
    Electronic Resource
    Absolute total cross sections for the ion–molecule reaction O+(4So)+H2O (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5100-5101 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Absolute total cross sections for H2O+ and OH+ formed by the O+(4So)+H2O reaction have been measured in the center-of-mass collision energy (Ec.m.) range of ≈0.1–60 eV. The cross sections for H2O+ are greater than those reported previously. The structure observed in the cross section curve for OH+ suggests that the OH++OH channel is produced at Ec.m.≈0.1–5.0 eV via a long-lived complex mechanism, while the OH++O+H channel is formed at Ec.m.≈5–60 eV by a short range charge transfer-predissociation pathway. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469561
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  • 10
    Electronic Resource
    Electronic Resource
    Expression of the ipomoelin gene from sweet potato is regulated by dephosphorylated proteins, calcium ion and ethylene (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A wound-inducible cDNA, ipomoelin (IPO) was isolated from the subtraction library of sweet potato (Ipomoea batatas cv. Tainung 57) and used as a molecular probe to investigate the transduction pathway of wounding signal within plant cells. Following mechanical wounding of the leaves of sweet potato, IPO mRNA accumulation peaked at 6 h and then continuously declined. However, IPO gene expression in the apical unwounded leaves began at 6 h after wounding and continued for a further 10 h. Besides mechanical wounding, methyl jasmonate (MeJA) was identified as a signal transducer leading to the accumulation of IPO mRNA. Treatment with salicylic acid reduced the production of IPO mRNA, further supporting the involvement of the octadecanoid pathway in the signal transduction of wounding in sweet potato. In addition, ethylene was involved in the signal pathway and induced the expression of the IPO gene. Furthermore, the application of okadaic acid, a protein phosphatase inhibitor, blocked the accumulation of IPO mRNA induced by MeJA or ethylene, indicating that activation of the IPO gene by both MeJA and ethylene was via dephosphorylated proteins. The presence of a calcium ion chelator or channel blockers also inhibited the expression of the IPO gene after wounding. However, investigation by confocal scanning microscopy further pointed out that mechanical wounding rather than the application of MeJA induced the accumulation of the calcium ion. These results may indicate that the calcium ion is also involved in the activation of IPO mRNA. In addition, wounding signals the accumulation of calcium ion first and then stimulates the biosynthesis of MeJA in sweet potato. Hence, the reaction sequence of signal transducers, including the calcium ion, MeJA and protein kinase/phosphatase, in the wounding signalling pathway of sweet potato is suggested in this report.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0016-8025.2003.01062.x
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