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  • 1
    Electronic Resource
    Electronic Resource
    Spectra and structure of small ring compounds. XLVIII. Conformational stability of methylcyclobutane from low frequency Raman data of the gas (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 545-551 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The low frequency (500–80 cm−1) Raman spectra of gaseous methylcyclobutane, c-C4H7CH3, and methyl-d3-cyclobutane have been recorded. A series of Q branches beginning at 161 cm−1 for the light molecule and 154 cm−1 for the d3 compound with successive transitions falling to lower frequencies have been assigned to the ring puckering vibrations of both the low energy equatorial and high energy axial conformers. These data have been fitted to an asymmetric potential function of the form: V(cm−1)=(4.78±0.10)×105X4−(3.08±0.04)×104X2 +(2.18±0.1)×104X3 with an assumed reduced mass of 160 amu for the light compound. Utilizing this potential the difference between the puckering angles for the two conformers was calculated to be 4.3° with the equatorial conformer having the larger value of 20.7°. A similar potential was obtained for the d3 molecule. The energy difference between the equatorial and axial forms was found to be 247±20 cm−1 (706 cal/mol) and a barrier of 641±20 cm−1 (1.83 kcal/mol) was found for the interconversion. Experimental values for the ΔH of both the liquid (354±179 cm−1) and gas (295±75 cm−1) from relative intensities of different Raman band pairs over 85 and 37 °C temperature ranges, respectively, were found to be consistent with the value obtained from the potential function. These results are compared to the corresponding quantities for similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452305
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  • 2
    Electronic Resource
    Electronic Resource
    Superspace formulation of general massive gauge theories and geometric interpretation of mass-dependent Becchi–Rouet–Stora–Tyutin symmetries (2000)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 41 (2000), S. 7304-7332 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A superspace formulation is proposed for the osp(1,2)-covariant Lagrangian quantization of general massive gauge theories. The superalgebra osp(1,2) is considered as subalgebra of the superalgebra sl(1,2)∼osp(2,2) which may be considered as the algebra of generators of the conformal group in a superspace with two anticommuting coordinates. The mass-dependent (anti)Becchi–Rouet–Stora–Tyutin symmetries of proper solutions of the quantum master equations in the osp(1,2)-covariant formalism are realized in that superspace as invariance under translations combined with mass-dependent special conformal transformations. The Sp(2) symmetry—in particular the ghost number conservation—and the new ghost number conservation are realized in the superspace as invariance under symplectic rotations and dilatations, respectively. The new ghost number conservation is generally broken by the choice of a gauge. The transformations of the gauge fields and the full set of necessarily required (anti)ghost and auxiliary fields under the superalgebra sl(1,2) are determined both for irreducible and first-stage reducible theories with closed gauge algebra. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288496
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  • 3
    Electronic Resource
    Electronic Resource
    The osp(1,2)-covariant Lagrangian quantization of reducible massive gauge theories (1999)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 40 (1999), S. 6189-6208 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The osp(1,2)-covariant Lagrangian quantization of irreducible gauge theories is generalized to L-stage reducible theories. The dependence of the generating functional of Green's functions on the choice of gauge in the massive case is discussed and Ward identities related to osp(1,2) symmetry are given. Massive first-stage theories with closed gauge algebra are studied in detail. The generalization of the Chapline–Manton model and topological Yang–Mills theory to the case of massive fields are considered as examples. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.533086
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  • 4
    Electronic Resource
    Electronic Resource
    Free Radical Reactions with Inorganic Covalent Hydrides: a Route to Polyfluoroalkyl Silicon Compounds (1956)
    [s.l.] : Nature Publishing Group
    Nature 178 (1956), S. 808-808 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Alkylsilyl radicals should be more reactive than trihalogenosilyl radicals, and a general study of their chemistry has been initiated. In particular, their reactions with olefins provide a useful new route for the synthesis of silicon compounds, and especially of polyfluoroalkyl silicon compounds. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/178808a0
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  • 5
    Electronic Resource
    Electronic Resource
    Decomposition and nanocrystallization in reactively sputtered amorphous Ta–Si–N thin films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1986-1991 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nanocrystallization process of reactively sputtered thin amorphous Ta–Si–N films is investigated by anomalous small angle x-ray scattering (ASAXS) and x-ray diffraction (XRD). Changes in the microstructure in Ta40Si14N46 films, density variations in the amorphous matrix, decomposition, formation, and growth of nanocrystals after vacuum anneals at different temperatures in the range between 800 and 1000 °C are observed and the results of the different techniques are compared. From a Fourier analysis of ASAXS intensities the nanostructure of the investigated ternary system is derived using a model of hard spheres according to Guinier and Fournet. ASAXS investigations indicate that the noncrystalline samples can be described by a monophase fit and the crystallized samples by a bimodal-phase fit, the latter results being consistent with XRD which identifies TaN and Ta5Si3 phases. Detailed analysis shows that TaN nanograins of approximately 2 nm size develop after a decomposition process. Larger grains of Ta5Si3 are observed in addition to the TaN grains if annealing is performed at temperatures higher than 950 °C. The aim of these investigations is to give a generally applicable explanation of the barrier failure mechanism for Ta–Si–N diffusion barriers, which is actually observed at temperatures below the crystallization temperature if the films are used in contact with Cu or Al. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388173
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  • 6
    Electronic Resource
    Electronic Resource
    Spectral characteristics of plasma emission during ArF excimer laser ablation of YBa2Cu3O7 (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 469-471 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to characterize the laser ablation process as it relates to the deposition of high Tc superconducting thin films, optical emission spectra produced during ArF excimer laser ablation of the high Tc superconductor YBa2Cu3O7 were studied. The population of excited states within the gas phase blow-off material depends strongly on excimer laser fluence at 193 nm. Ablation using relatively low excimer laser fluences produces a significant fraction of YO in the gas phase. The plasmas derived from ablation of targets made from the high Tc material are similar to plasmas observed from ablation of the individual components BaCO3, CuO, and Y2O3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101555
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  • 7
    Electronic Resource
    Electronic Resource
    IgH class switching and translocations use a robust non-classical end-joining pathway (2007)
    [s.l.] : Nature Publishing Group
    Nature 449 (2007), S. 478-482 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Immunoglobulin variable region exons are assembled in developing B cells by V(D)J recombination. Once mature, these cells undergo class-switch recombination (CSR) when activated by antigen. CSR changes the heavy chain constant region exons (Ch) expressed with a given variable region ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06020
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  • 8
    Electronic Resource
    Electronic Resource
    NMR structure of inactivation gates from mammalian voltage-dependent potassium channels (1997)
    [s.l.] : Nature Publishing Group
    Nature 385 (1997), S. 272-275 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The functional properties of inactivation domains of Kv channels have been analysed in studies combining electrophysiological measurements with site-direct mutagenesis. Both electrostatic and hydrophobic interactions were found to determine the affinity of the ball domain for its binding site in ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/385272a0
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  • 9
    Electronic Resource
    Electronic Resource
    Applicability of effective medium theory to ferroelectric/ferrimagnetic composites with composition and frequency-dependent complex permittivities and permeabilities (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1655-1660 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-frequency (1 MHz–1 GHz) transmission line measurements were used to determine the composition and frequency-dependent complex permittivities and complex permeabilities of ferroelectric/ferrimagnetic (barium titanate and a magnesium-copper-zinc ferrite) composites. The effective medium rules of Maxwell–Garnett give both lower and upper bounds for the effective permittivities and permeabilities and yield accurate estimates of the bulk electric and magnetic properties at low volume fill fraction of either component provided the proper host matrix is chosen. Bruggeman theory yielded the best predictive values for the permittivity and permeability over the entire composition range. In all cases these complex quantities were shown to be constrained by Bergman–Milton bounds. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361010
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  • 10
    Electronic Resource
    Electronic Resource
    Surface modification during scanning tunneling microscope measurements on YBa2Cu3O7 thin films (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7774-7777 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: During scanning tunneling microscopy measurements on YBa2Cu3O7 thin films with positive sample bias voltages, different kinds of surface modifications appear. While in the topography condition no surface modification occurs, the cleaning and etching conditions irreversibly change the surface topography. In the deformation condition a strong elastic deformation of the tip and/or the surface is observed. It is shown that field evaporation of material from the surface to the tip is responsible for the observed surface modification. In consequence, the tip is contaminated with different oxides. Localized states in the oxides make resonant tunneling of electrons through the oxide layer possible. The configuration of these localized states determines the kind of surface modification by the scanning tunneling microscope. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357955
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