Search Results - (Author, Cooperation:A. Gomes)

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  1. 1
    Staff View
    Publication Date:
    2018-02-21
    Publisher:
    American Physical Society (APS)
    Print ISSN:
    1539-3755
    Electronic ISSN:
    1550-2376
    Topics:
    Physics
    Keywords:
    Liquid Crystals
    Published by:
    http://www.aps.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Staff View
    Publication Date:
    2018-02-10
    Publisher:
    American Chemical Society (ACS)
    Print ISSN:
    0022-3263
    Electronic ISSN:
    1520-6904
    Topics:
    Chemistry and Pharmacology
    Published by:
    http://www.acs.org/

    Latest Papers from Table of Contents or Articles in Press
  3. 3
    Staff View
    Publication Date:
    2013-07-05
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Adaptation, Physiological ; Anoxia/*genetics/metabolism ; Bacterial Proteins/genetics/metabolism ; Binding Sites ; Chromatin Immunoprecipitation ; Gene Expression Profiling ; *Gene Regulatory Networks/genetics ; Genomics ; Lipid Metabolism/genetics ; Metabolic Networks and Pathways/*genetics ; Models, Biological ; Mycobacterium tuberculosis/drug effects/*genetics/*metabolism/physiology ; Oxygen/pharmacology ; Proteolysis ; RNA, Messenger/genetics/metabolism ; Reproducibility of Results ; Sequence Analysis, DNA ; Transcription Factors/genetics/metabolism ; Tuberculosis/metabolism/microbiology
    Published by:
    http://www.nature.com/

    Latest Papers from Table of Contents or Articles in Press
  4. 4
    Almeida, A. Gomes
    Springer
    Published 1964
    Staff View
    ISSN:
    1436-5073
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Chemistry and Pharmacology
    Description / Table of Contents:
    Summary A radiochemical method is described for determining the endogenic respiration of bacterial spores. A nutrient solution for the cultivation of radioactive bacteria was obtained by the assimilation of radioactive carbon dioxide with the aid of a green leaf and its extraction with water and acid. These bacteria were separated from the nutrient medium by means of isotonic sodium chloride solution and brought to the spore stage. The specific activity of the spores in the best experiments was 3 · 103 disintegrations per minute and milligram spores. About 30 mg of the spores were kept suspended in sodium chloride solution at a particular temperature for the respiration experiments. Subsequently, the radioactive carbon dioxide evolved during this incubation was driven out by means of a known amount of inactive carbon dioxide, absorbed in alkali, and finally precipitated with barium. The carbon dioxide liberated from the precipitate was measured in a gas counting tube. The radioactivity serves as a measure of the respiration of the spore suspension. At room temperature the spore respiration is approximately three times higher than at 0° C, at 37° about 9 times higher. The vegetative forms ofBacillus mesentericus respire 1,7% of their dry mass per hour. Assuming that this consists of 50% carbon and that the respiratory coefficient is equal to 1, this endogenic respiration corresponds to a $$Q_{O_2 }$$ value of 16. The endogenic respiration of the spores is 255 times smaller than that of the vegetative forms. This corresponds to a $$Q_{O_2 }$$ -value of 0,06. The lowering of the respiration performance in the spore state is very noteworthy from the standpoint of the metabolic economy.
    Abstract:
    Résumé On décrit une méthode radiochimique pour déterminer la respiration endogène de spores bactériennes. On obtient une solution nutritive pour les bactéries radioactives en faisant assimiler du gaz carbonique radioactif par une feuille verte et en effectuant l'extraction par l'eau et par un acide. Elles sont séparées du bouillon de culture par une solution isotonique de chlorure de sodium et utilisées pour la multiplication des spores. L'activité spécifique des spores a atteint 3 · 103 désintégrations par minute et par milligramme de spores avec la meilleure expérience. Pour les expériences portant sur la respiration, on a maintenu en suspension 30 mg environ de spores, à température déterminée dans une solution de chlorure de sodium. Le gaz carbonique radioactif qui avait pris naissance pendant cette incubation a été finalement chassé par une quantité connue de gaz carbonique inactif, absorbé par de la soude, puis précipité par le baryum. On a dosé avec un tube compteur pour gaz le CO2 libéré par le précipité. On utilise la radioactivité comme mesure de la respiration par les spores en suspension. A température ambiante, la respiration des spores est environ 3 fois plus forte qu'à 0° C et à 37° environ 9 fois plus. Les formes végétatives deBacillus mesentericus respirent 1,7% de leur poids sec par heure. En supposant que celui-ci soit constitué par 50% de carbone et que le coefficient respiratoire soit égal à un, cette respiration endogène correspond à une valeur $$Q_{O_2 }$$ de 16. La respiration endogène des spores est 255 fois plus petite que celle des formes végétatives. Il lui correspond une valeur $$Q_{O_2 }$$ de 0,06. Du point de vue de l'économie du métabolisme des bactéries, la diminution du pouvoir respiratoire pendant la multiplication des spores constitue un phénomène très intéressant.
    Notes:
    Zusammenfassung Eine radiochemische Methode zur Bestimmung der endogenen Atmung von Bakteriensporen wird beschrieben. Durch Assimilation von radioaktivem Kohlendioxid mit Hilfe eines grünen Blattes und dessen Extraktion mit Wasser und Säure wird eine Nährlösung für die Züchtung radioaktiver Bakterien gewonnen. Diese wurden vom Nährboden mit isotoner Kochsalzlösung getrennt und zur Versporung gebracht. Die spezifische Aktivität der Sporen war im besten Versuch 3 · 103 Zerfälle pro Minute und Milligramm Sporen. Für die Atmungsversuche wurden etwa 30 mg Sporen bei bestimmter Temperatur in Kochsalzlösung in Suspension gehalten. Anschließend wurde das während dieser Inkubation entwickelte radioaktive Kohlendioxid mit einer bekannten Menge inaktiven Kohlendioxids ausgetrieben, in Lauge absorbiert und schließlich mit Barium gefällt. Das aus dem Niederschlag freigesetzte Kohlendioxid wurde im Gaszählrohr gemessen. Die Radioaktivität dient als Maß für den veratmeten Teil der Sporensuspension. Bei Zimmertemperatur liegt die Sporenatmung etwa dreimal, bei 37° etwa neunmal höher als bei 0° C. Die vegetativen Formen vonBacillus mesentericus veratmen pro Stunde 1,7% ihrer Trockenmasse. Unter der Annahme, daß diese zu 50% aus Kohlenstoff besteht und daß der respiratorische Koeffizient gleich 1 ist, entspricht diese endogene Atmung einem $$Q_{O_2 }$$ -Wert von 16. Die endogene Atmung der Sporen ist 255mal kleiner als die der vegetativen Formen. Ihr entspricht ein $$Q_{O_2 }$$ -Wert von 0,06. Vom Standpunkt der Stoffwechselökonomie der Bakterien ist die Herabsetzung der Atmungsleistung bei der Versporung sehr bemerkenswert.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1007/BF01218069

    Articles: DFG German National Licenses
  5. 5
    Zamora, S. ; da Silva, C. M. ; Schmidt, J. E. ; Livi, F. P. ; Gomes, A. A.

    [S.l.] : American Institute of Physics (AIP)
    Published 1991
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The lattice parameters and the saturation magnetization are measured for the series of intermetallic compounds A(Fe,B)2, A=Zr, Hf and B=Si and Al, with concentrations less than 15%. The magnetization measurements and the lattice parameter behavior are qualitatively discussed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.349907

    Articles: DFG German National Licenses
  6. 6
    Sommer, R. L. ; Schmidt, J. E. ; Gomes, A. A.

    [S.l.] : American Institute of Physics (AIP)
    Published 1993
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    In this article, the power spectra of the Barkhausen noise of Ni1−xMnx is presented. The measurements were made in the ferromagnetic phase at several temperatures and manganese concentrations in order to map the effects of the degree of disorder and of the temperature on domain wall dynamics. Measurements in standard ferromagnetic materials were also made to compare the dynamics in both cases.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.353678

    Articles: DFG German National Licenses
  7. 7
    de Oliveira, N. A. ; Gomes, A. A. ; Troper, A.

    [S.l.] : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The hyperfine fields and the local magnetic moments in a series of alloys of isoelectronic transition impurities diluted in iron are discussed. We intend to show that, even within a very simplified model, period effects for isoelectronic impurities at the beginning of an n-d series (e.g., Sc, Y, and Lu) are dominated by the charge difference effect, inducing a very strong repulsive potential. We find that the local impurity magnetic moments are very close to each other, leading to hyperfine fields, in fair agreement with experimental data. Our calculation accounts for the general trends of the local impurity moments in ferromagnetic Fe, despite quantitative deviations that do occur, due to the very simple structure of this model. We point out, however, that our calculation is a starting point for a more refined one, dealing with rare-earth impurities (such as Eu, Gd, and Tb) placed in the Fe host, where the strong charge effects are present, together with f-spin scattering.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.355377

    Articles: DFG German National Licenses
  8. 8
    Gomes, A. S. L. ; de Araujo, Cid B. ; Ainslie, B. J. ; Craig-Ryan, S. P.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1990
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We report the observation of amplified spontaneous emission in silica-based single-mode optical fibers doped with Tm3+. Frequency upconverted emission was observed in a number of visible and near-infrared lines after pumping by 1064 nm radiation. The upconversion process is induced via the nonlinear absorption of the infrared beam and enhanced by stimulated Raman scattering in the fiber, leading to amplified spontaneous emission in the blue (∼473 nm) region.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.103924

    Articles: DFG German National Licenses
  9. 9
    Acioli, L. H. ; Gomes, A. S. L. ; Hickmann, J. Miguel ; de Araujo, Cid B.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1990
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The characterization and application of a new source of incoherent light for studies of ultrafast processes in condensed matter is described. It is based on the stimulated Raman effect in monomode optical fibers and has a coherence time of ∼80 fs. As an application, we have measured the homogeneous dephasing time of CdSxSe1−x-doped glasses and obtained a value of 14±4 fs for above-gap excitation at room temperature.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.102939

    Articles: DFG German National Licenses
  10. 10
    Gomes, A. S. L. ; de Araujo, Cid B.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.102054

    Articles: DFG German National Licenses
  11. 11
    Acioli, L. H. ; Gomes, A. S. L. ; Rios Leite, J. R. ; de Araujo, Cid B.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Wave mixing experiments are reported using two infrared and one visible laser beams which are incident on a semiconductor doped glass. The mixing process produces infrared to visible image conversion via the material electronic nonlinearity with fast (less than 20 ps) time response.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.101183

    Articles: DFG German National Licenses
  12. 12
    Acioli, L. H. ; Gomes, A. S. L. ; Leite, J. R. Rios

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1988
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The optical susceptibilities of CdSxSe1−x -doped glasses were observed up to χ(11) using a spatially resolved phase-matched multiwave mixing technique. Using a pulsed dye laser tuned near the band gap, measurements were performed for ||χ(3)||, ||χ(5)||, and ||χ(7)|| in four different commercial filter glasses.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.99781

    Articles: DFG German National Licenses
  13. 13
    Novak, M. A. ; Gomes, A. M. ; Rapp, R. E.

    [S.l.] : American Institute of Physics (AIP)
    Published 1998
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The magnetic properties of the Mn12ac molecular cluster were studied by complex susceptibility and specific heat measurements. Extensive ac susceptibility measurements done under a magnetic field on good quality single crystals and zero field powder sample specific heat results indicate that the usual uniaxial Hamiltonian, as well as the recently proposed fourth order corrections, are not enough to account for all the observations. Very low temperature specific heat data indicate the presence of zero field splitting of the ground state which is much larger than expected. Finally, specific heat measurements done under a magnetic field permitted us to observe and measure the lattice spin relaxation by calorimetric methods with time constants that are in agreement with the magnetic relaxation measurements. © 1998 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.367830

    Articles: DFG German National Licenses
  14. 14
    Gomes, A. M. ; Novak, M. A.

    [S.l.] : American Institute of Physics (AIP)
    Published 2000
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We present a comparison of the field dependence of the relaxation times observed for Mn12Bz, (Bz=benzoate) spin cluster, and its derivative containing one extra electron, r-Mn12Bz. At low temperatures Mn12Bz has a total spin S=10, while for the reduced sample r-Mn12Bz the spin of the ground state is S=19/2. Theory predicts that half integer spin should not present quantum tunneling, the so-called spin parity effect. We show evidence from experiments that quantum tunneling is partially inhibited in the reduced species. Low temperature magnetization hysteresis loops of the reduced variety do not show well-defined steps. In addition, the ac susceptibility as a function of the field also does not show a clear resonance at the expected level crossing fields, as seen in the nonreduced sample. © 2000 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.372594

    Articles: DFG German National Licenses
  15. 15
    Muniz, R. Bechara ; d'Albuquerque e Castro, J. ; Troper, A. ; Gomes, A. A.

    [S.l.] : American Institute of Physics (AIP)
    Published 1988
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We have numerically calculated the magnetic susceptibilities which appear in the Hartree–Fock instability criterion for actinide 3d transition-metal intermetallic compounds. This calculation is based on a previous tight-binding description of these actinide-based compounds [A. Troper and A. A. Gomes, Phys. Rev. B 34, 6487 (1986)]. The parameters of the calculation, which starts from simple tight-binding d and f bands are (i) occupation numbers, (ii) ratio of d-f hybridization to d bandwidth, and (iii) electron-electron Coulomb-type interactions.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.340776

    Articles: DFG German National Licenses
  16. 16
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Ion velocity distributions generated in a 0.53-μm laser-produced plasma are studied with a Thomson parabola diagnostic at 5×1013 W/cm2. Ions are observed in a narrow energy range. However, for velocities 〉4×105 m/s the distribution dN/dV decreases exponentially and the temperatures deduced from these distributions are in good agreement with those given by x-ray emission.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.336249

    Articles: DFG German National Licenses
  17. 17
    Gomes, A. S. L. ; Gouveia-Neto, A. S. ; Margulis, W. ; Taylor, J. R.

    [S.l.] : American Institute of Physics (AIP)
    Published 1986
    Staff View
    ISSN:
    1089-7623
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Electrical Engineering, Measurement and Control Technology
    Notes:
    Excited by the frequency doubled optically compressed 10-ps pulses from a cw mode-locked Nd:YAG laser, the amplified output from a GaAs photoconductive device was used to drive a synchronously operated Photochron IIA streak camera at 300-MHz sweep rates. A temporal jitter of ±6 ps was measured which was limited by the driving laser pulse width and amplitude stability.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1139093

    Articles: DFG German National Licenses
  18. 18
    Ma, H. ; Gomes, A. S. L. ; de Araujo, Cid B.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1991
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A two-color "z'' scan method is introduced to characterize the nonlinear refraction of optical materials in their absorptive region. We demonstrate the method by measuring the sign and the magnitude of the frequency nondegenerate nonlinearity in the absorptive region of semiconductor doped glasses.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.105933

    Articles: DFG German National Licenses
  19. 19
    Petrov, D. V. ; Gomes, A. S. L. ; de Araújo, Cid B.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Spatial modification of a Gaussian beam by reflection on a surface of a high-absorbing material is investigated experimentally. A theoretical description in a geometrical-optics approach is given. The usefulness and sensitivity of the method for applications in measuring laser induced surface deformation and Kerr-like nonlinear coefficients is discussed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.112175

    Articles: DFG German National Licenses
  20. 20
    de Araújo, Cid B. ; Gomes, A. S. L. ; Srivastava, R.

    Woodbury, NY : American Institute of Physics (AIP)
    Published 1995
    Staff View
    ISSN:
    1077-3118
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The operation of an all-optical switch in a rare-earth doped channel waveguide is described. The switching mechanism is based on an optically induced intramodal energy exchange, driven by a resonantly enhanced nonlinearity of a Nd3+ ion. Switching times around 410 μs at a repetition rate of 1 kHz was demonstrated. © 1995 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.114040

    Articles: DFG German National Licenses