P. D. Singh

Madan Mohan Malaviya University of Technology

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A. A. de Almeida

Universidade de São Paulo

W. F. Huebner

Los Alamos National Laboratory

G. C. Sanzovo

Universidade Estadual de Londrina

C. M. Andreazza

Universidade Estadual Paulista (Unesp)

J. A. de Freitas Pacheco

Observatoire de la Côte d’Azur

D. C. Boice

Scientific Consulting Group

Amit Pathak

Banaras Hindu University

S. J. C. Landaberry

National Observatory

Sanjay Kumar Soni

Madan Mohan Malaviya University of Technology

W. J. Maciel

Universidade de São Paulo

Cooperative Institutions

Children's Defense Fund

126

Fermi National Accelerator Laboratory

124

Istituto Nazionale di Fisica Nucleare

116

University of Bologna

Duke University

Argonne National Laboratory

University of Florida

Yale University

Instituto de Física de Cantabria

Universidad de Cantabria

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The Formation of CN and CN⁺by Direct Radiative Association

The Astrophysical Journal (2000)

P. D. Singh C. M. Andreazza

Rate coefficients for direct radiative association of carbon and nitrogen atoms to form CN, and of carbon ions and nitrogen atoms to form CN + ions, are calculated for temperatures in the range of 300 to 14,700 K. For the CN molecule, the rate coefficients can be represented by the standard expression, kCN(T) = 7.87 × 10-19(T/300)0.056 exp(-96.0/T) cm3 s-1 for temperatures between 300 and 2700 K and kCN(T) = 1.37 × 10-18(T/300)-0.128 exp(-520.1/T) cm-3 s-1 at T > 2700 K. For the CN+ ion, the corresponding expression is k(T) = 1.08 × 10-18(T/300)0.071 exp(-57.5/T) cm-3 s-1 for the temperature range studied. Calculated rate coefficients kCN are about 2 orders of magnitude lower than the canonical value used in the modeling of the chemistry of various astrophysical environments.

Carbon fibers

Atmospheric temperature range

10.1086/309023

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Citations (16)

Dust colors, dust release rates, and dust-to-gas ratios in the comae of six comets

Astronomy and Astrophysics Supplement Series (1996)

G. C. Sanzovo P. D. Singh W. F. Huebner

In an attempt to find correlations between properties of comets, we determine the dust colors, dust release rates, and dust-to-gas mass ratios in the comae of Comets Bowell (1980 b = 1982 I), Bradfield (1979 l = 1979 X), Brorsen-Metcalf (1989 o = 1989 X), Giacobini-Zinner (1984 e = 1985 XIII), Levy (1990 c = 1990 XX), and Stephan-Oterma (1980 g = 1980 X) using a uniform and systematic analysis of the continuum fluxes measured at optical wavelengths. We assume that the continuum fluxes observed in these comets are from light scattered by micrometer-sized dust particles. The color of the dust is blue, relative to the Sun, in Comets Bradfield (1979 X) and Brorsen-Metcalf (1989 X); both comets have a low dust-to-gas mass ratio (). Comets Giacobini-Zinner (1985 XIII) and Stephan-Oterma (1980 X) have an intermediate dust-to-gas mass ratio (), whereas Comets Levy (1990 XX) and Bowell (1982 I) have a high dust-to-gas mass ratio (). The continuum flux from dust particles in comets with intermediate to high dust-to-gas mass ratios is in general red, relative to the Sun. However, the color changes to blue in these comets when the dust-to-gas mass ratios are low relative to their peak values.

Mass ratio

10.1051/aas:1996294

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Citations (25)

An analysis of spectrophotometric observations of comets Austin (1982g) and Bradfield (1980t)

Earth Moon and Planets (1989)

P. D. Singh K. Sinha B. M. Tripathi Heloisa M. B. Roberty

Production rate

Vaporization

Coma (optics)

Ultraviolet

10.1007/bf00114102

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Citations (2)

The photodissociation lifetimes of the NH radical in comets

Astronomy and Astrophysics (1987)

P. D. Singh Ruth Gruenwald

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Citations (9)

Photodissociation lifetime of 32S2 molecule in comets

Earth Moon and Planets (1986)

A. A. de Almeida P. D. Singh

Production rate

10.1007/bf00057603

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Citations (26)

The Radiative Association of C and S, C⁺and S, Si and O, and Si⁺and O

The Astrophysical Journal (1997)

C. M. Andreazza P. D. Singh G. C. Sanzovo

10.1086/303580

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Citations (7)

Mass Loss Rates of Three Comets

Springer eBooks (1992)

P. D. Singh W. F. Huebner D. C. Boice I. Konno E. Scalise

10.1007/978-94-011-2761-5_110

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The radiative association of Si and N atoms, C and O atoms, and C atoms and S+ ions

Monthly Notices of the Royal Astronomical Society (2002)

P. D. Singh G. C. Sanzovo Antonio Carlos Borin Fernando R. Ornellas

Potential energy curves for the SiN.X2Σ+ and A2Πi electronic states, and the SiN(A2Πi-X2Σ+) transition moment function (TMF) are obtained at the MRCI level of theory, with a SA-CASSCF zero-order wavefunction. These potential energy curves and TMF are used to compute radiative association rate coefficients of Si and N atoms for temperatures in the range 300-14 700 K. Rate coefficients for radiative association of carbon and oxygen atoms for the formation of CO, and carbon atoms and sulphur ions for the formation of CS+, are also calculated for temperatures in the range 300-14 700 K. These radiative association rate coefficients (k) are fitted to the standard equation where A=2.02×10−19 cm3 s−1, α=0.029 and β=83.9 for the SiN molecule. The corresponding values for the CO molecule are 3.09×10−17 cm3 s−1, 0.325 and 1629, and those for the CS+ ion are 2.01×10−18 cm3 s−1, 0.066 and 300.9. Radiative association of C and O atoms occurs with emissions of the first overtone band at 2.3 μm and the fundamental band at 4.6 μm found in the ejecta of Supernova 1987A and novae.

Einstein coefficients

10.1111/j.1365-2958.2008.06311.x-i1

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Citations (25)

The hydroxyl ion in interstellar clouds

Astronomy and Astrophysics (1980)

P. D. Singh A. A. de Almeida

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Citations (4)

Regression equations for spirometry in children aged 6 to 17 years in Delhi region.

PubMed (2012)

Sunil K. Chhabra V K Vijayan M. Sohel Rahman Vinod Mittal P. D. Singh

Most of the studies carried out in India to develop regression equations for spirometry in children are now several years-to-decades old and had used equipment and measurement protocols that have since changed. Prediction equations using the current standardisation protocols for spirometry are not available. The lung health of the population may have changed too.To develop regression equations for spirometry for children aged 6 to 17 years of north Indian origin in Delhi region.School children of north Indian origin, as determined by mother tongue and parentage, aged 6 to 17 years were screened by a health questionnaire and physical examination and those found "normal" underwent spirometry according to the standardised procedure recommended by the American Thoracic Society/European Respiratory Society (ATS/ERS) task force in 2005. Pearson's correlation analysis was carried out to identify the predictor variables for spirometric parameters. Prediction equations were developed using the multiple linear regression procedure. The independent variables were entered in sequence of height, age and weight. R2, adjusted R2 and R2 change, standard errors of the estimate (SEE), and estimates of regression coefficients were obtained and the goodness of fit was examined.Data was obtained in 365 boys and 305 girls. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1) peak expiratory flow rate (PEFR), forced expiratory flow rate at 50% and 75% exhalation of vial capacity (F50 and F75) and mean forced expiratory flow rate over the middle 50% of the vital capacity (F25-75) showed moderate to strong correlations with age, height and weight in both boys and girls. In both genders, the equations explained very high variability of FVC, FEV1 and PEFR as shown by the R2 values. The explained variability for flow rates was lesser, with that for F75 being the least.Regression equations for spirometry variables for children of north Indian origin in Delhi region have been developed. These represent the first such effort from India after the publication of the ATS/ERS task force 2005 guidelines on standardisation of spirometry.

Vital capacity

Exhalation

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Citations (19)