Search Results - (Author, Cooperation:G. P. Srivastava)
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1Latest Papers from Table of Contents or Articles in PressH. M. Tütüncü, Ertuǧrul Karaca, H. Y. Uzunok, and G. P. Srivastava
American Physical Society (APS)
Published 2018Staff ViewPublication Date: 2018-05-15Publisher: American Physical Society (APS)Print ISSN: 1098-0121Electronic ISSN: 1095-3795Topics: PhysicsKeywords: Superfluidity and superconductivityPublished by: -
2Latest Papers from Table of Contents or Articles in PressStaff View
Publication Date: 2018-09-11Publisher: American Physical Society (APS)Print ISSN: 1098-0121Electronic ISSN: 1095-3795Topics: PhysicsKeywords: Inhomogeneous, disordered, and partially ordered systemsPublished by: -
3Latest Papers from Table of Contents or Articles in PressStaff View
Publication Date: 2018-07-27Publisher: American Physical Society (APS)Print ISSN: 1098-0121Electronic ISSN: 1095-3795Topics: PhysicsKeywords: Surface physics, nanoscale physics, low-dimensional systemsPublished by: -
4Latest Papers from Table of Contents or Articles in PressT. Raj ; K. Rothamel ; S. Mostafavi ; C. Ye ; M. N. Lee ; J. M. Replogle ; T. Feng ; M. Lee ; N. Asinovski ; I. Frohlich ; S. Imboywa ; A. Von Korff ; Y. Okada ; N. A. Patsopoulos ; S. Davis ; C. McCabe ; H. I. Paik ; G. P. Srivastava ; S. Raychaudhuri ; D. A. Hafler ; D. Koller ; A. Regev ; N. Hacohen ; D. Mathis ; C. Benoist ; B. E. Stranger ; P. L. De Jager
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-05-03Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: Adaptive Immunity/genetics ; Alleles ; Alzheimer Disease/ethnology/genetics ; Autoimmune Diseases/ethnology/*genetics ; Autoimmunity/*genetics ; CD4-Positive T-Lymphocytes/*immunology ; Ethnic Groups/genetics ; Genetic Predisposition to Disease/ethnology/*genetics ; Genome-Wide Association Study ; Humans ; Immunity, Innate/genetics ; Monocytes/*immunology ; Multiple Sclerosis/ethnology/genetics ; Neurodegenerative Diseases/ethnology/*genetics ; Parkinson Disease/ethnology/genetics ; Polymorphism, Single Nucleotide ; Quantitative Trait Loci ; Rheumatic Fever/ethnology/genetics ; TranscriptomePublished by: -
5Articles: DFG German National LicensesNagpal, Alka ; Gupta, R. S. ; Srivastava, G. P.
[S.l.] : American Institute of Physics (AIP)
Published 1991Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Electrical properties of (p)aSi:H-(n)GaAs heterojunction were investigated by measuring current-voltage and capacitance-voltage characteristics. The experimental results are interpreted in accordance with a generalized a-c junction model. The built-in potential of the heterojunction and the gap-state density in the chemical vapor deposition (p)aSi:H were obtained from the capacitance-voltage characteristics.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesStaff View
ISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: The current-voltage characteristic of polycrystalline titanium-substituted lithium ferrites has been measured at temperatures above room temperature. At voltages below a critical value an Ohmic relationship is observed, while it obeys a power-law relationship (i∝Vα, where α is a temperature-dependent constant) above the critical voltage. At low voltages conduction is determined by the boundary layer, whereas at higher voltages, the current in the solid is mainly due to the space-charge-limited carriers. ac conductivity (σac) and dielectric permittivity (ε') show a large temperature-dependent dispersion in the 5–10-MHz range. The experimental results indicate that titanium substitution suppresses all these parameters. The dielectric relaxation has a very large relaxation intensity. In the theoretical model the temperature- and frequency-dependent layer properties are inserted into Koop's model and the theoretical dispersion curves are obtained. The agreement of these data with the experimental findings is remarkable.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesStaff View
ISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: We present detailed ab initio density functional calculations of equilibrium atomic geometry, electronic states, and chemical bonding for the adsorption of elemental S on Si(001). Following recently reported room temperature low-energy electron diffraction, Auger electron spectroscopy, thermal desorption spectroscopy, and work function measurements by Papageorgopoulos et al. [Phys. Rev. B 55, 4435 (1997)], three different adsorption models have been studied: hemisulfide (2×1) structure, monosulfide (1×1) structure, and disulfide (1×1) structure. For hemisulfide and monosulfide structures, the calculated location of S above the Si(001) surface is in excellent agreement with the experiment. An analysis of surface free energy suggests that, in the allowed range of S chemical potential, the monosulfide structure is more stable than the hemisulfide and disulfide structures. A signature of desorption of the SiS unit is obtained from the study of the disulfide structure. © 1998 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesKuanr, B. K. ; Singh, P. K. ; Kishan, P. ; Kumar, N. ; Rao, S. L. N. ; Singh, Prabhat K. ; Srivastava, G. P.
[S.l.] : American Institute of Physics (AIP)
Published 1988Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: The electric, dielectric permittivity, loss tangent, microwave power absorption, and hysteresis loop parameters were studied on a series of cobalt-substituted lithium titanium ferrites. The experimental results indicate that cobalt substitution affect all these parameters. The observed dispersion in conductivity and dielectric permittivity with frequency and temperature are in accordance with Maxwell–Wagner model while the microwave and hysteresis loop properties can be interpreted with the help of Dionne's exchange isolation model.Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesChilana, G. S. ; Gupta, R. S. ; Srivastava, G. P.
[S.l.] : American Institute of Physics (AIP)
Published 1986Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Bulk unipolar diodes are majority-carrier three-layer (n-p-n) semiconductor diodes in which the current flows due to the thermionic emission of majority carriers over a barrier formed in the bulk of the material. Expressions for the barrier height of two typical bulk unipolar diodes, namely a bulk barrier diode (n++p+n) and a p-plane barrier diode (n+p++n), are derived. The functional dependence of the barrier height on various technological parameters is discussed. The two diodes are quite similar in their structure and characteristics. However, the p-plane barrier diode is more suitable as a majority-carrier diode. The variation of ideality factor and the saturation current of these diodes is shown to be very similar to the metal semiconductor diode.Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesGupta, R. S. ; Chilana, G. S. ; Srivastava, G. P.
[S.l.] : American Institute of Physics (AIP)
Published 1986Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: A modified model of a triangular barrier diode has been proposed and analyzed by considering the effect of low to moderate p-type doping in the two intrinsic regions. The presence of such acceptor impurities is shown to increase the effective barrier height. The functional dependence of barrier height, saturation current, and ideality factor on various technological parameters is discussed. A method to determine the barrier height and effective Richardson constant has also been suggested. The high-speed switching behavior of this diode is shown to improve.Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesChilana, G. S. ; Gupta, R. S. ; Srivastava, G. P.
[S.l.] : American Institute of Physics (AIP)
Published 1985Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: Bulk barrier diodes are majority carrier diodes, in which the current is given by the thermionic emission of carriers over a barrier present in the bulk of the material. The height of this barrier depends on the dopings of the various layers of the diode, which has a p+np or n+pn structure. In this paper, different ways to determine this barrier height and its controlling parameters, have been suggested by considering the effect of temperature on the current and the applied voltage of the device.Type of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesStaff View
ISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: The atomic structures of four possible models for the adsorption of Zn on GaAs(001)–(2×4) are investigated by means of a first-principles pseudopotential technique. Our calculations suggest that Zn atoms adsorb preferentially in trench (third layer) sites. All structures are characterized by the breaking of the arsenic dimer and the formation of two mixed dimers in the vertical plane containing the original As–As dimer. The Zn atom lies 0.16 Å higher than the As atoms, and the mixed dimer has a bond length of 2.31 Å. All other structural features for the four models studied (e.g., minimum interplanar distance, and remaining As dimer bond lengths) retain the characteristics of the free surface. © 2000 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesSrivastava, G. P. ; Jacob, Mohan V. ; Jayakumar, M. ; Bhatnagar, P. K.
[S.l.] : American Institute of Physics (AIP)
Published 1997Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: The real and imaginary parts of the surface impedance of YBCO superconductors have been studied at different microwave power levels. Using the relations for the critical current density and the grain boundary resistance, a relation for calculating the power dependence of the surface resistance has been obtained. Also, a relation to find the resonant frequency of a superconducting microstrip resonator at various input power levels has been derived. Measurements have been carried out on various microstrip resonators to study the variation of surface resistance and resonant frequency at different rf power levels. The experimental results are in good agreement with theoretical results. © 1997 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesMiotto, R. ; Srivastava, G. P.
College Park, Md. : American Institute of Physics (AIP)
Published 2001Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: Using a first-principles pseudopotential method we have studied the adsorption and dissociation of NH3, PH3, and AsH3 on the Si(001)–(2×1) surface. Apart from the existence of a barrier for the adsorption of the precursor state for arsine, we observe that the global behavior for the chemisorption of the XH3 molecules considered in this work is as follows: the gas phase XH3 adsorbs molecularly to the electrophilic surface Si atom and then dissociates into XH2 and H, bonded to the electrophilic and nucleophilic surface silicon dimer atoms, respectively. The energy barrier, corresponding to a thermal activation, is much smaller than the usual growth temperature, indicating that all three molecules will be observed in their dissociated states at room temperature. All adsorbed systems are characterized by elongated Si–Si dimers that are (almost) symmetric in the dissociative case but asymmetric in the molecular case. According to our first-principles calculations, all XH3 and XH2 systems retain the pyramidal geometry observed for the gas molecules. Our calculated vibrational spectra further support the dissociative model for the XH3 molecules considered here. © 2001 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesStaff View
ISSN: 1436-5065Source: Springer Online Journal Archives 1860-2000Topics: GeographyPhysicsDescription / Table of Contents: Zusammenfassung Ergebnisse von in der Zeit von 1967–1969 in Poona mit örtlichen Blitzzählern durchgeführten Gewitterbeobachtungen werden vorgelegt. Wenn je Stunde mehr als zwanzig Impulse auf einem 5 V/m-Zähler registriert werden, kann eine positive Korrelation zwischen der durchschnittlichen Gesamtippuloszahl und der Anzahl der Tage, an denen Donner gehört wurde, festgestellt werden. Es wird gezeigt, daß, obwohl ein einzelnes isoliertes Gewitter das normale Bild der Gewittertätigkeit in einem Monat oder in einer Jahreszeit verfälschen kann, ein langfristiger statistischer Durchschnitt mit größerer Zuverlässigkeit als besserer Index für elektrische Aktivität genommen werden kann als die gegenwärtige „akustische” Methode der Gewitterbeobachtung.Notes: Summary The results of thunderstorm observations made with local lightning flash counters at Poona during 1967–1969 are presented. A positive correlation between the average total count when the count exceeds 20 per hour on a 5V/m counter, and the number of days per month when thunder is heard has been established. The diurnal and seasonal variations in thunderstorm activity are described. It is seen that although a single isolated storm can vitiate the normal pattern of thunderstorm activity in a month or season, a long term statistical average can be taken with a greater degree of confidence as a better index of electrical activity than the current aural method of observation of thunderstorms.Type of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesStaff View
ISSN: 1434-601XSource: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract Electric susceptibility of ethyl chloride has been determined in the microwave region at 8,780 mc/s over a pressure range of 10 cm to 75 cm of mercury, and a temperature range of 263° K to 353° K. It has been found that the total susceptibility, at constant temperature, varies almost linearly with pressure. The contribution due to quantised transitions to total susceptibility has been calculated from the data on absorption measurements and it is found to be 0·45 × 10−3. Since most of this contribution is due to zero frequency transitions, no measurable dispersion is observed in this region. It has been found possible to determine the values of dipole moment and the sum of atomic and electronic polarisations from the data on temperature variation of susceptibility. The values are μ=2·06 × 10−18 e.s.u and (P A +P E )=22·70. These results are in fair agreement with those obtained earlierType of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesStaff View
ISSN: 1434-601XSource: Springer Online Journal Archives 1860-2000Topics: PhysicsType of Medium: Electronic ResourceURL: -
18Articles: DFG German National LicensesStaff View
ISSN: 1434-601XSource: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract Dispersion of millimeter waves due to ethyl chloride in the range ν=1·34 cm−1 to 1·44 cm−1 is computed by means of quantum mechanical formulas. It is found that dispersion is due to (i) contribution of sixR branch rotational lines in the region considered, (ii) contribution ofR branch lines away from the region and (iii) the contribution ofQ branch lines at zero wavenumber. The maximum variation in the susceptibility is 1·9 × 10−5 and occurs at ν=1·39 cm−1 due to combined contribution of transitions at 1·3878 cm−1, 1·3902 cm−1 and 1·3927 cm−1.Type of Medium: Electronic ResourceURL: -
19Articles: DFG German National LicensesStaff View
ISSN: 1420-9071Source: Springer Online Journal Archives 1860-2000Topics: BiologyMedicineNotes: Zusammenfassung Vom Zuckerrohr-Mosaik-Virus befallene Zuckerrohrblätter weisen eine höhere Peroxidase- und eine niedrigere Katalaseaktivität auf gegenüber den Enzymaktivitäten gesunder Blätter.Type of Medium: Electronic ResourceURL: -
20Articles: DFG German National LicensesStaff View
ISSN: 1420-9136Source: Springer Online Journal Archives 1860-2000Topics: GeosciencesPhysicsDescription / Table of Contents: Zusammenfassung Messungen der luftlelektrischen Leitfähigkeit und des atmosphärischen Potentialgradienten werden berichtet, welche mit ballongetragenen Radiosonden in der freien Atmosphäre über Indien ausgeführt worden sind. Oberhalb der Austauschschicht vermindert sich das Potentialgefälle exponentiell mit der Höhe, während die Leitfähigkeitsprofile das dazu spiegelbildliche Bild zeigen. In der Troposphäre werden jedoch grosse Änderungen des Potentialgefälles und der Leitfähigkeit im Zusammenhang mit Wolken, Dunst, Staub und mit anderen meteorologischen Erscheinungen und mit Raumladungseffekten beobachtet. Auch in der Stratosphäre werden signifikante, wenn auch kleine Änderungen beobachtet, welche mit der Existenz von Aerosolschichten zusammen zu hängen scheinen. Das gesamte atmosphärische Potential wurde aus den integrierten Potential-gefällekurven berechnet zu 300 kV als Mittel gefunden; dieses Ionosphärenpotential zeigt Veränderungen um diesen Mittel in Form von Tagesgängen und Jahresgängen.Notes: Summary Results of measurements of atmospheric electrical potential gradient and conductivity in the free atmosphere using balloon borne radiosondes made at a few stations in India are presented. The potential gradient generally decreases exponentially with height above the exchange layer and the electrical conductivity profiles show corresponding mirror image symmetry. Large variations of electrical potential gradient and conductivity are, however, observed in the troposphere closely associated with clouds, dust and haze and other local meteorological phenomena and space charge effects. Significant though small variations are also observed in the stratosphere, which appear to be associated with the existence of aerosol layers. From an analysis of integrated potential profiles the total atmospheric potential has been calculated and found to have a mean value of 300 kV; the ionospheric potential varies diurnally and seasonally about the mean.Type of Medium: Electronic ResourceURL: