000021   Yi K W;Lee M Y (Life Sci Dep, College of Sci, Soonchunhyang Univ, Asan PO Box 97, Chungnam, 336-745, Korea) : Environmental stress-induced extracellular isoperoxidase RC3 from rice. J envir Biol 2003, 24(1), 17-22.

2 tables, 28 ref

000020   Saha S K (Indian Institute of Astrophysics, , Bangalore-560 034) : Speckle interferometric technique for astronomical observations. J Optics 2003, 32(1), 37-56.

The speckle imaging is a photographic technique that resolves objects viewed through severely distorted media. The results are insensitive to the errors caused by apparent size of the isoplanatic patch and the telescope aberrations. Short descriptions of the atmospheric turbulence and its effect on the flat wavefront from a stellar source is presented; the shortcomings of the conventional long-exposure images in the present of Earth's atmosphere are discussed. The advantages of the speckle interferometric technique over conventional imaging are enumerated. The technical details of the method, basic Fourier optics, data analysis procedures are also described. The data processing methods that are implemented in Indian Institute of Astrophysics, in order to decipher Fourier phase are also described also.

11 illus, 41 ref

000019   Mohanty U K;Das T K (NO, Regional Institute-VI, CMPDI Ltd, Bhubaneswar) : Surveying through GPS and its utilisation in surface mines. Indian Min Engng J 2002, 41(6), 27-30.

^ccr1 illus, 3 tables, 5 ref

024870   Mathew B;Subramaniam A;Bhavya B (NO, Indian Institute of Astrophycis, Bangalore-560 034) : Spectroscopic study of a few herbig Ae/Be stars in young open clusters. Bull Astr Soc India 2010, 38(1), 35-52.

Presents the spectroscopic study of 5 Herbig Ae/Be stars in young open clusters. These are identified from a survey of emission-line stars in young open clusters. The Herbig Ae/Be stars are found to show a linear correlation in H_alpha equivalent width versus reddening corrected (H-K_s) colour plot, with a clear offset from the distribution of Classical Be stars. The candidates are found to show near infrared excess which was revealed through de-reddened (J-H) versus (H-K_s) colour-colour diagram and spectral energy distribution. From optical/near-IR photometry and spectroscopy, we suggest that Bochum 6-1, IC 1590-1 and NGC 6823-1 are Herbig Be while IC 1590-2 and NGC 7380-4 are Herbig Ae candidates. Bochum 6-1 is an interesting Herbig B[e] star with a high H_alpha equivalent width of -206 A, which is the highest among the surveyed stars. We combined the optical and near-IR photometry to estimate the duration of star formation in the clusters, Bochum 6, IC 1590, NGC 6823 and NGC 7380. We found ongoing star formation in all these clusters, with an appreciable number of pre-main sequence stars. The age of these Herbig Ae/Be stars, estimated using pre-main sequence isochrones, were found to range between 0.25-3 Myr. IC 1590 is found to be an interesting young cluster (<126> 4 Myr) with 3 emission stars, each belonging to Herbig Ae, Herbig Be and Classical Be respectively. All the four clusters studied here were found to be forming stars for the last 10 Myr.

8 illus, 41 ref

020896   Singh S;Saxena R (P.G. Deptt. of Zoology, Govt. of Autonomous College, Satna (M.P.)) : Land use / land cover change study in Chitrakoot and its environ's using remote sensing technique. Ecol Envir Conserv 2002, 8(1), 33-6.

Changes in land use/land cover over a period of 20 years were studied. using space based satellite remote sensing technique in part of Chitrakoot area of Satna district falling withing the state boundary of M.P. and is a well known historical place of district. The environmental changes in and around the study area have been clearly identified, mapped and monitored by the visual comparison of land use/ land cover maps, which was prepared by using SOI topomaps of year 1974-75 and space brone remote sensing satellite data of Year 1996, using visual interpretation technique along with revenue map of the area. Results shows rapid environmental changes in land use/land cover as well as socio-cultural scenario of the study area.

1 tables,8 ref

019874   Anand S;Vaishya J S;Kandpal H C (Optical Radiation Standards, National Physical Laboratory, Dr K S Krishnan Marg, New Delhi-110 012) : Correlation-induced spectral changes - a review, recent researches and applications. MAPAN 2002, 17(2), 43-66.

Since the discovery of the phenomenon of correlation-induced spectral shift also known as the Wolf Effect, a lot of studies have been conducted. The research that has been done in the last one and a half decade on theory and on experiments conducted to verify the theoretical predictions and also showing the applications of the studies on correlation-induced spectral changes. In addition some important experiments on spectral switches and dynamic scattering conducted recently in NPL, New Delhi. The experimental studies on spectral switches may find applications in the construction of the spectrum selective optical interconnects. The studies on non-Doppler wavelength shift due to dynamic multiple scattering may explain some of the long-standing controversies in galaxy-quasar red shift.

^iia19 illus, 76 ref

018790   Navabi A A;Riazi N (Inst for Advanced Studies in Basic Sci, , Zanjan, Iran) : Is the age problem resolved?. J Astrophys Astr 2003, 24(1-2), 3-10.

The cosmological, astrophysical, and nucleocosmochronological methods for estimating the age of the universe and the corresponding uncertainties have been comparatively studied. It has led to the conclusion that the new measurements of cosmological parameters, and the recent estimates of the age of globular clusters have led to the gradual disappearance of the age problem from the arena of modern cosmology.

1 illus, 27 ref

018789   Ishwara-chandra C H;Dwarakanath K S; Anantharamaiah K R (National Center for Radio Astorphysics, TIFR, Post Bag 3, Ganeshkhind, Pune-411 007) : GMRT detection of HI 21 cm associated absorption towards the z = 1.2 red quasar 3C 190. J Astrophys Astr 2003, 24(1-2), 37-43.

Reports the GMRT detection of associated HI 21 cm-line absorption in the z≅ 1.1946 red quasar 3C 190. Most of the absorption is blue-shifted with respect to the systemic redshift. The absorption, at <126> 647.7 MHz, is broad and complex, spanning a velocity width of <126> 600 kms^-1. Since the core is self-absorbed at this frequency, the absorption is most likely towards the hotspots. Comparison of the radio and deep optical images reveal linear filaments in the optical which overlap with the brighter radio jet towards the south-west. Suggests that most of the HI 21 cm-line absorption could be occurring in the atomic gas shocked by the south-west jet.

1 illus, 1 table, 24 ref

018788   Dwivedi B N;Mohan A;Pandey V S (Applied Physics Dep, Institute of Technology, Banaras Hindu Univ, Varanasi-221 005) : MHD seismology of the solar corona. Curr Sci 2003, 84(11), 1388-90.

3 illus, 13 ref

018787   Bharadwaj S;Pandey S K (Physics and Meteorology & Center for Theoretical Studies Dep, I.I.T., Kharagpur 721 302) : Hi fluctuations at large redshifts: II - the signal expected for the GMRT. J Astrophys Astr 2003, 24(1-2), 23-35.

For the GMRT, the expected signal from redshifted HI emission is calculated at two frequency bands centered at 610 and 325 MHz. The study focuses on the visibility-visibility cross-correlations, proposed earlier as the optimal statistical estimator for detecting and analyzing the signal. These correlations directly probe the power spectrum of density fluctuations at the redshift where the radiation originated, and thereby provide a method for studying the large scale structures at large redshifts. Presents detailed estimates of the correlations expected between the visibilities measured at different baselines and frequencies. Analytic fitting formulas representing the salient features of the expected signal are also provided. These will be useful in planning observations and deciding an optimal strategy for detecting this signal.

7 illus, 3 tables, 11 ref

018786   Basu D (Physics Dep, Carleton Univ, Ottawa, ON K1S 5B6, Canada) : The Hubble relation for a comprehensive sample of QSOs. J Astrophys Astr 2003, 24(1-2), 11-21.

A correlation between redshifts (z) and apparent magnitudes (V) (Hubble relation) of Quasi Stellar Objects (QSOs) has long been sought. Such a correlation exists for galaxies whose redshifts are of cosmological origin. However, a plot of the two quantities representing the Hubble diagram ofr QSOs exhibits, in general, wild scatter. This raises the question whether redshifts of QSOs are cosmological. On the other hand, most luminous QSOs in groups, and subsamples with particular properties have been reported to show the Hubble relation. Analyses all optically non-variable QSOs in a comprehensive sample. In the analysis the objects have been grouped into certain intervals of apparent magnitudes. Correlations obtained between redshifts and magnitudes are all statistically robust. Also, the Hubble relation in the usual form V = 5 log z + C is obeyed very convincingly for QSOs with V<60> 19.5.

3 illus, 2 tables, 16 ref

016755   Padma Kumari B;Trimbake H K;Londhe A L;Jadhav D B (NO, Indian Institute of Tropical Meteorology, Pune-411 008) : A case study of twilight probing of the atmosphere during leonid meteor shower 2001. Curr Sci 2003, 84(9), 1238-41.

Twilight sounding method is used to retrieve the vertical distribution of the dust particles throughout the middle atmosphere. The photometry observations of the twilight sky brightness were carried out during the Great Leonid meteor storm of November 2001 at a tropical inland station Pune (18°32′N, 73°51′E), India. This experiment gave an opportunity to monitor height distribution of meteoric dust between 16 and 150 km. Normalization of the current set of data with a reference data set shows the evidence of influx of the fine meteor dust with a broad peak at around 80 km in the evening twilight of November 18, the day of meteor storm peak, and its subsequent descent to the lower due to this meteor shower at the peak of distribution is about seven times the normal.

3 illus, 17 ref

016754   Majumdar D (Theory Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, kolkata-700 064) : A possible explanation for MACHOs: a candidate for dark matter-from quark-hadron phase transition. Curr Sci 2003, 84(9), 1179-80.

5 ref

016753   Gupta S P;Sekar R;Acharya Y B (NO, Physical Research Laboratory, Navarangpura, Ahmedabad-380 009) : A new plasma wave over low latitude ionosphere during leonid meteor strom. Curr Sci 2003, 84(10), 1340-2.

Leonid meteor strom is a unique astronomical event that occurs once in 33 years. In order to investigate the effect of Leonid meteor strom over low latitude ionosphere, rocket measurements of plasma parameters were carried out on 18 and 20 November 1999 from Sriharikota, India. The meteoric activity was at its peak on 18 November 1999. Results obtained on plasma waves using a high frequency Langmuir probe revealed for the first time, an experimental evidence for the presence of sub-meter scale size plasma wave over low latitude E-region. The peak amplitude of the plasma wave occurs at 105 km with a magnitude of ″4% of ambient electron density. The ambient plasma conditions during these measurements imply that the causative mechanism for the generation of this plasma wave is different from well known gradient drift waves.

2 illus, 13 ref

000157   Unnikrishnan C S;Gillies C T;Ritter R C (Gravitation Group, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Evidence for the quantum birth of our universe. Pramana J Phys 2002, 59(2), 369-74.

Present evidence for a nonsingular origin of the Universe with intial conditions determined by quantum physics and relativistic gravity. In particular, established that the present temperature of the microwave background and the present density of the Universe agree well with our predictions from these intial conditions, after evulution to the present age using the Einstein-Friedmann equation. Remarkably, the quantum origin for the Universe naturally allows its evolution at exactly the critical density. Discussed the consequences of these results to some fundamental aspects of quantum physics in the early Universe.

7 ref

000068   Singh R N (Dep of Applied Physics, Institute of Technology, Banaras Hindu University, Varanasi-221 005) : Lightning-generated electromagnetic wave emission from jupiter's atmosphere. Curr Sci 2003, 84(8), 980-2.

^ssc30 ref

000067   Choudhary D P (Udaipur Solar Observatory, Physical Research Laboratory, , Udaipur-313 001) : The question of life and death of sunspots. Curr Sci 2003, 84(1), 14-6.

^ssc1 illus, 19 ref

000064   Apte M;Mahajani P;Vahia M N (NO, , Rupali Society, Vile Parle (East), Mumbai-400 057) : Possible errors in historical dates: error in correction from Julian to Gregorian calendars. Curr Sci 2003, 84(1), 21-2.

^ssc1 tables, 5 ref

011689   Choudhary K N;Choudhary A K S (NO, A V College of Engineering, Sangrur) : Production planning. Ind Engng J 2003, 32(4), 4-6.

A linear programming model has been discussed.

2 tables

010505   Singh G N;Shrivastava P K (Dep of Physics, Sudarshan Degree college, Lalgaon, Distt.Rewa-486 115) : Two types of solar plasma streams and their association with geomagnetic and interplanetary indices. Acta Cienc Indica-Phys 2002, 28(2), 83-6.

Solar wind stream are continuously blowing from solar corona into interplanetary space. These high speed wind plasma streams are separated into two categories. The corotating and flare generated streams. These separation are categorized on the basis of their various physical properties. The two typical examples for our analysis. First event of Aug. 25 to Sep. 2,1989 identifie as Flare generated streams. The another event of August 14-19, 1990 is identified as corotating streams. Analysis of this event indicated that both types of plasma stream are responsible in producing geomagnetic disturbances. flare generated streams are found more effective in producing geomagnetic as well as interplanetary disturbances. Interpress the relationship of high solar wind streams with geomagnetic disturbances in existing theories.

5 ref

010504   Sharma R P (Variable Energy Cyclotron centre, , 1/AF, Bidhan Nagar) : The solar system. Phys Educ 2002, 19(2), 101-26.

The soloar system members have been described in the brief and efforts have been made to include the latest available information, wherever possible. The various space crafts are exploring some of these bodies and some of the crafts have already crossed the boundary of the planetary system. More crafts are being planned for detailed exploration that will qualitatively enhance our knowledge about the solar system and evolution of life in it and eventually help in exploitation of the solar system for the benefit of the mankind and other forms of life.

9 illus, 5 ref

010503   Ojha D K;Sivrani T;Parthasarathy M;Omont A; Ganesh S;Simon G (NO, T.I.F.R., Homi Baba Road, Colaba, Mumbai-400 005) : Spectroscopic observations of first ISOGAL sources. Bull Astr Soc India 2000, 28(4), 697-705.

Infrared Space Observatory Galactic survey at 7 and 15μm of <126> 22 deg² of the inner galactic disk and bulge, has detected several hundred thousand sources. Combining ISOGAL survey with I, J, H, K_s data of DENIS (Deep Near Infrared Survey of the Southern Sky) and 2MASS (The Two Micron All Sky Survey), has provided a completely new insight of infrared galactic stars. proposed a limited preliminary program of low resolution spectroscopy with the 2.3-meter telescope of VBO (Vainu Bappu Observatory, Kavalur, India) on ISOGAL sources, with the double purpose : confirm or help to establish the criteria of identification from ISOGAL+DENIS/2MASS data of a few classes of important sources (subclasses of dusty AGB stars, dusty young stars, extreme red giants, supergiants, etc.), observe a number of stars which look peculiar. Presents the spectra of a few sources observed in 6 ISOGAL fields.

2 illus, 1 table, 4 ref

010502   Lakhina G S (NO, Indian Institute of Geomagnetism, Colaba, Bombay-400 005) : Magnetic reconnection. Bull Astr Soc India 2000, 28(4), 593-646.

Magnetic reconnection is considered as a basic plasma process which efficiently converts magnetic energy to plasma kinetic energy accompanied by changes in the topology of the magnetic field configuration. It prohibits the excessive build-up of magnetic energy in the current sheets encountered in astrophysical and space plasmas. Some of the important theories concerning magnetic reconnection are described in a simple manner. The difference between magnetic reconnection and diffusion is emphasized. The difference between magnetic reconnection and diffusion is emphasized. The aim of this review is to high light the physical ideas of magnetic reconnection with the help of mathematical tools. For the purpose of illustration, applications of magnetic reconnection to solar flares and magnetospheric substorms are discussed.

36 illus, 118 ref

010501   Chattopadhyay R (NO, Haripal G.D. Institution, Khamarchandi-712 405) : Covariation of critical frequency of F₂-layer and relative sunspot number. Bull Astr Soc India 2000, 28(4), 657-63.

Seasonal and overall covariation of relative sunspot number and the critical frequency of F₂-layer of the terrestrial inonosphere has been investigated and the results have been obtained; There is a strong correlation between the relative sunspot number and the critical frequency of F₂-layer of ionosphere. There exist alternate similar and dissimilar zones in the seasonal variation pattern of the relative sunspot number and critical frequency of F₂-layer. Critical frequency of F₂-layer increases nonlinearly with relative sunspot number reaching a maximum at sunspot maximum. An empirical equation cooecting critical frequency of F₂-layer with relative sunspot number has been derived by applying least square method of curve fitting which gives values of critical frequency of F₂-layer very close to the experimentally obtained values of the same.

2 illus, 1 table, 10 ref

010500   Brijesh Kumar;Sagar R;Rautela B S;Srivastava J B;Srivastava R K (U.P. State Observatory, , Manora Peak, Naini Tal-263 129) : Sky transparecy over Naini Tal : a retrospective study. Bull Astr Soc India 2000, 28(4), 675-86.

Presents an analysis of the atmospheric extinction coefficients measured during 1964 to 1999 in broad-band photometric passbands at U.P. State Observatory, Naini Tal. The extinction properties are also studied from the monochromatic extinction measurements carried out during 1970 to 1978. It is observed that except the yearly variation, no noticeable long term variation in extinction has been found over last 35 years. The extinctions in the ultraviolet region were found low at Naini Tal in comparison to other sites in the world. The extinctions due to aerosols are observed to be the minimum.

6 illus, 2 table, 27 ref

010499   Barman S K (NO, Milki H.S. School, Puratuli, Barmanpara, Malda-732 101) : Linear polarization of binaries II. Phase function : WQ<. Bull Astr Soc India 2000, 28(4), 665-73.

Presents a method of calculating linear polarizations in close binaries whose surfaces are distorted due to tidal and rotational forces. Limb-darkening effect has been taken into account. Particles of different sizes are embedded in the outer atmosphere. The law of differential rotation of the primary is considered in analytic form: Ω = b₁ + B₂ W² + b₃ w⁴, where b₁, b₂ and b₃ are constants and w is the distance of a point P (rθ,φ) from the axis of rotation of the primary. The atmosphere is assumed to be non-grey, plane-parallel and the phase function is WQ^<126> (μ) Q^<126>' (μ'). Calculations are done with respect to rest frame fixed at the centre of the primary, polar radius (r₀) of the primary, wave-length (λ) of the incident light, radius of a particle (1) and angle of inclination (β) with respect to the line of sight. It is noticed that polarization increases with an increase of the radius r_p steadily; polarization increases with an increase of the radius of the particle (1), polarization increases with an increase of the mass-ratio q. The method of solution has been applied to several late type binaries to calculate disk integrated linear polarization of light emitted by them.

4 illus, 1 table, 13 ref

010498   Anupama G C (Indian Institute of Astrophysics, , Bangalore) : Indian astronomical observatory - high-altitude station of optical-infrared astronomy. Bull Astr Soc India 2000, 28(4), 647-56.

2 illus, 1 ref

010497   Anandrao B G;Nanda Kumar M S;Jog N S;Patel R T (NO, Physical Research Laboratory, Ahemadabad-380 009) : NIFS : a near infrared imaging fabry-perot spectrometer. Bull Astr Soc India 2000, 28(4), 687-95.

Describes a Near-Infrared Imaging Fabry-Perot Spectrometer (NIFS) operating in the K band to provide a maximum spectral resolution of 2000-3000 over two optional fields of view of <126>2' X 2' and 4' X 4' with plate scales of 0.5" and 1" / pixels respectively. N I F S is an add-on instrument to an existing infrared camera with a 256X256 HgCdTe array detector. The instrument is operational with a 1.2 m telescope to primarily work on star forming regions and starburst galaxies which strongly emit in several diagnostically important lines within the K band. The design, testing and operation of NIFS are discussed in the light of preliminary observations made on the Orion Molecular Cloud Complex.

4 illus, 2 tables, 15 ref

023890   Liu H B;Yang J K;Tan J C;Su D Z;Wang W L;Li X J;Jia H (NO, National Univ of Defense Technology, Changsha, Hunan-410 073, Email: yuhan120483@yahoo.com.cn) : Focal adjustment for star tracker. Def Sci J 2010, 60(6), 678-82.

Technique of measuring intensity distribution and size of spot image developed has been discussed, which is especially suitable for defocus adjustment in ground test of star tracker. A novel approach for choosing a proper defocusing position has been proposed based on collimator, Gaussian surface fitting method, and other ordinary instruments. It proves to be practical and adequate in the development of distant object tracking such as star tracker.

6 illus, 11 ref

009495   Chrysoulakis N (Foundation for Research and Technology - Hellas, Institute of Applied and Computational Mathematics, Regional Analysis, FORTH - ICAM, Vassilika Vouton, P.O. Box 1527, GR-71110, Heraklion, Crete, Greece) : Energy in the urban environment: use of terra/aster imagery as a tool in urban planning. J Indian Soc Remote Sens 2002, 30(4), 245-54.

Terra/ASTER imagery has been analysed together with in-situ spatial data to examine the potential of multi-spectral remote sensing to support urban planning. The potential of ASTER imagery to support energy budget estimation has also been examined by defining and mapping some microclimatic parameters for the centre of the city of Athens. Images in visible, near infrared and thermal infrared areas of the electromagnetic spectrum have been processed to define the urban land cover and topographic characteristics as well as to estimate the spatial distributions of vegetation, visible reflected radiation and brightness temperature. It has been found that ASTER multi-spectral imagery enables a better understanding of energy aspects, their causes and effects, providing an important addition to conventional methods of monitoring the urban environment.

7 illus, 18 ref.

008385   Garg S C et al (National Physical Laboratory, , New Delhi - 110 012) : RPA aeronomy experiment onboard the Indian satellite SROSS-C2 - Some important aspects of the payload and satellite. Indian J Radio Space Phys 2003, 32(2), 5-15.

An aeronomy payload of retarding potential analyser (RPA) consisting of an electron RPA and a potential probe (PP), designed and developed at the National Physical Laboratory, New Delhi, was flown onboard the Indian satellite SROSS-C2 on 4 May 1994, for making in situ measurements of F-region ionospheric plasma. The objective of the mission. Investigates the characteristics and energetics of the equatorial and low latitude ionosphere / thermosphere over the Indian region. The SROSS-C2 was a spin-stabilized orbiting satellite placed in an elliptical orbit having orbit inclination of 46.3°. The payload made simultaneous sampling of electron and ion plasma in the altitude range of 420-620 km for more than half a solar cycle from minima to maxima of the 23rd solar cycle activity. During initial phase of the mission, measurements were made in a higher orbit for a limited period of two months, while the satellite apogee was at 930 km keeping the perigee same. The total ion density, electron and ion temperatures, ion composition, supra-thermal electron flux and irregularities in electron and ion densities along the satellite orbit can be derived from the measurements. Some important aspects of the scientific payloads, the satellite and its orbital configuration, which are important in understanding the payload operation in space for data collection including the analysis of data and their interpretations, are described.

6 illus, 3 tables, 14 ref

007364   Ubachukwu A A;Chukwude A E (Physics and Astronomy Dep, University of Nigeria Nsukka, Nigeria) : On the relativistic beaming and orientation effects in core-dominated quasars. J Astrophys Astr 2002, 23(3-4), 235-42.

Investigates the relativistic beaming effects in a well-defined sample of core-dominated quasars using the correlation between the relative prominence of the core with respect to the extended emission (defined as the ratio of core- to lobe- flux density measured in the rest frame of the source) and the projected linear size as an indicator of relativistic beaming and source orientation. Based on the orientation-dependent relativistic beaming and source orientation paradigm for high luminosity sources in which the Fanaroff-Riley class-II radio galaxies form the unbeamed parent population of both the obe- and core-dominated quasars which are expected to lie at successively smaller angles to the line of sight. Finds that the flows in the cores of these core-dominated quasars are highly relativistic, with optimum bulk Lorentz factor, Y_opt <126> 6-16, and also highly anisotropic, with an average viewing angle, <126> 9°-16°. Furthermore, the largest boosting occurs within a critical cone angle of ≈ 4°-10°.

3 illus, 37 ref

007363   Sharma S;Narayan A (Mathematics Dep, Bhilai Institute of Technology, Durg-491 001) : Non-linear oscillation of inter-connected satellites system under the combined influence of the solar radiation pressure and dissipative force of general nature. Bull Astr Soc India 2001, 29(2), 115-26.

The non-linear oscillation of inter-connected system about its equilibrium position in the neighabourhood of main resonance ω=1, under the combined effects of the solar radiation pressure and the dissipative forces of gerneral nature has been discussed. It is found that the oscillation of the system gets disturbed when the frequency of the natural oscillation approaches the resonance frequency.

7 illus, 23 ref

007362   Sanyal S (High Energy and Cosmic Ray Centre, North Bengal Univ, Darjeeling-734 430) : Cosmic ray air showeers in the knee energy region. Pramana J Phys 2003, 60(3), 443-51.

The cosmic ray extensive air showers in the knee energy region have been studied by the North Bengal University array. The differential size spectra at different atmospheric depths show a systematic shift of the knee towards smaller shower size with the increase in atmospheric depth. The measured values of spectral indices at below and above the knee are - 2.45±0.03 and - 2.91±0.05 respectively. Measurements at different atmospheric depths correspond to the same values within the error limits both for below and above the knee. The present experimental results have been compared with similar such experiments.

6 illus, 37 ref

007361   Sagar R et al (NO, State Observatory, Manora Peak, Nainital-263 129) : Optical and radio observations of the bright GRB 010222 afterglow: evidence for rapid synchrotron cooling. Bull Astr Soc India 2001, 29(2), 91-106.

Reports photometric observations of the optical afterglow of GRB 010222 in V, R and I passbands carried out between 22-27 February 2001 at Nainital. Determined the CCD Johnson BV and Cousins RI photometric magnitudes for 31 stars in the field of GRB 010222 and used them to calibrate measurements as well as other published BV RI photometric magnitudes of the GRB 010222 afterglow. Constructed the light curve of the afterglow emission B, V, R and I passbands, and from a broken power-law fit determined the early and late time power-law flux decay indices as 0.74±0.05 and 1.35±0.04 respectively. Steepening in the flux decay seems to have started around 0.7 day after the burst. Negligible Galactic extinction amounting E(B-V)=0.023 mag is derived in the direction of the GRB. Derived the value of the spectral index in the X-ray to optical region to be 0.61±0.02 and 0.75±0.02 at Δt=0.35 and 9.13 day. Attempted radio observations of the afterglow from RATAN-600 telescope during 23-26 February 2001 and from the Giant Metrewave Radio Telescope on 8 March 2001, yielding upper limits of <126> 5 mJy at 3.9 GHz and <126> 1 mJy at 610 MHz respectively. The millimeter wave observations obtained with the IRAM Plateau de Bure Interferometer during 24 asnd 25' February 2001 and 16 March 2001 at 93 GHz and 230 GHz also indicate no flux detection from the afterglow. The light curve and the spectrum indicate the synchrotron cooling frequency lies in the sub millimeter region, which also explains the observed sub-millimeter excess. Attributing the observed break in the light curve to the sideways expansion of collimated ejecta, estimated a jet opening angle of <126> 2.0n^1/8 deg.

4 illus, 3 tables, 63 ref

007360   Porwal M C;Sharma L;Roy P S (Indian Institute of Remote Sensing, National Remote Sensing Agency, 4, Kalidas Road, P.B. NO. 135, Dehra Dun-248 001) : Stratification and mapping of Ephedra gerardiana Wall. in Poh (Lahul and Spiti) using remote sensing and GIS. Curr Sci 2003, 84(2), 208-12.

The somlata plant (Ephedra gerardiana Wall.) has acquired importance in Indian medicine because it yields alkaloids that are effective in the treatment of asthma and hay fever. Tincture of Ephedra is used for cardiac and circulatory stimulation. Its demand as medicine has intensified the pressure on landscapes bearing this species. This has necessitated bioprospection and active planning to ensure safe conservation of the existing gene pool and sustainable utilization of this land resource. On account of its importance, an attempt has been made, using remote sensing and geographical information system to identify and map Ephedra-dominated sites. IRS ICD/1D LISS-III false colour composite has been used for stratification of E. gerardiana bearing landscape in the study. Test sites were used to evaluate the mapping results and promising accuracy has been achieved. The study highlights the possibility of mapping E. gerardiana in complex terrain conditions. Through this study it is also emphasized that the methodology can be used for bioprospection of species in the whole Lahul and Spiti district.

4 illus, 2 tables, 16 ref

007359   Patil K D (Math Dep, B D Coll of Engng, Sewagram, Wardha-442 001) : Gravitational collapse in higher-dimensional charged-Vaidya space-time. Pramana J Phys 2003, 60(3), 423-31.

Gravitational collapse of higher-dimensional charged-Vaidya space-time has been analyzed. It has been shown that singularities arising in a charged null fluid in higher dimension are always naked violating at least strong cosmic censorship hypothesis (CCH), though not necessarily weak CCH. It has been shown that earler conclusions on the occurrence of naked singularities in four-dimensional case can be extended essentially in the same manner in 5D case also.

34 ref

007358   Pant D N;Oli S (Math Dep, Kumaun Univ, Nainital-263 002) : Bianchi type I string cosmologies. Pramana J Phys 2003, 60(3), 433-41.

By making use of Letelier's form of energy-momentum tensor for a cloud of stringdust some classes of solutions of general relativistic field equations which describe cosmological string-dust models in Bianchi type I space-time have been pesented. Some of the classes of models obey Takarbayashi's equation of state whereas a class of models exhibits inflation in the initial stage. Two of the classes presented here have Kasner's space-time as past asymptote.

7 ref

007357   Naik S;Rao A R;Chakrabarti S K (NO, Tata Institute of undamental Research, Homi Bhabha Road, Mumbai-400 005) : Fast transition between high-soft and low-soft states in GRS 1915+105: evidence for a critically viscous accretion flow. J Astrophys Astr 2002, 23(3-4), 213-33.

Presents the results of a detailed analysis of RXTE observations of class ω (Klein-Wolt et al. 2002) which show an unusual state transition between high-soft and low-soft states in the Galactic microquasar GRS 1915+105. Indicates that the basic accretion disk structure during both dip and non-dip regions of class ω is similar, but differ only in intensity. To explain these observations, invokes a model in which the viscosity is very close to critical viscosity and the shock wave is weak or absent.

6 illus, 5 tables, 24 ref

007356   Manchanda R K (NO, Tata Institute of Fundamental Research, Colaba, Mumbai-400 005) : Spectral variability in hard X-rays and the evidence for a 13.5 years period in the bright quasar 3C273. J Astrophys Astr 2002, 23(3-4), 243-58.

Reports the observation of nearst quasar 3C273 made with LASE instrument on November 20th, 1998 as a part of our continuing programme of ballon borne hard X-ray observations in the 20-200keV band using high sensitivity Large Area Scintillation counter Experiment. Data clearly show a steep spectrum in the 20-200keV with power law spectrical index 2.26±0.07. This is in complete contrast to the reported data from OSSE and BeppoSAX which suggest the value of 1.3 to 1.6 for the power law index in the X-ray energy band, but is quite consistent with the value derived for the high energy gamma ray data. A single power law fit in the X-ray and gamma ray energy bands points to a common origin of these photons and the absence of spectral break around 1MeV as suggested in literature. Reanalyzed the available data to study the temporal variability of the spectrum in the hard X-ray band. Analysis reveals that 50 keV flux from the source, shows a strong modulation with a period of about 13.5 years. The analysis of the optical light curve of the source also supports the 5000 day period. Discuses the emission mechanism and the possible sites for X-ray photons along with the implcations of the long term periodicity with respect to source geometry.

6 llus, 31 ref

007355   Manchanda R K (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400 005) : Spectral measurements of Cyg X-3: a thermal source embedded in hot plasma within a cold shell. J Astrophys Astr 2002, 23(3-4), 197-212.

The spectral variability at hard X-ray energies above 30 keV can provide crucial input for the unified picture. Presents spectral observations of Cyg X-3, made in the on-going survey of galactic and extragalactic X-ray sources in the 20-200 KeV energy region, using large Area Scintillation counter Experiment. The data show a clear power-law photon spectrum of the dN/dE <126> E^-2.8 in the 20 to 130 keV energy range. A comparison with earlier data suggests the band is conserved at all time for a given luminosity level irrespective of the state. Proposes that this behaviour can be explained by a simple geometry in which a thermal X-ray source is embedded in a hot plasma formed by winds from the accretion disk within a cold shell. The high/soft and low/hard X-ray states of the source are simply the manifestation of the extent of the surrounding scattering medium in which the seed photons are Comptonized and hot plasma can be maintained by either the X-ray driven winds or the magneto-centrifungal winds.

8 illus, 58 ref

007354   Kaushal R S (Phy and Astrophys Dep, Univ of Delhi, Delhi-110 007) : Stability of extended scalar diquark stars vis-a-vis soliton stars. Pramana J Phys 2003, 60(3), 461-7.

Motivated by relatively large values of the maximum mass (8.92M) and radius (50.7 km) obtained for an extended scalar diquark star within the framework of an effective φ⁴-theory some interesting observations are made with regard to the stability of stellar objects describable in general in terms of the polynomial field theories.

2 illus, 29 ref

007353   Gupta V K;Tuli V;Singh S;Anand J D;Goyal A (Dep of Physics and Astrophysics, University of Delhi, Delhi-110 007) : Radial oscillations of neutron stars in strong magnetic fields. Pramana J Phys 2002, 59(3), (NULL).

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities. The magnetic BPS equation of state (EOS) has been used which is similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.

5 illus, 1 table, 13 ref

007352   Giacobbe F W (Chicago Res Center/American Air Liquide Inc., , 5230 South East Avenue, Countryside, Illinois 60525, USA) : Maximum stellar iron core mass. Pramana J Phys 2003, 60(3), 415-22.

An analytical method of estimating the mass of a stellar iron core, just prior to core collapse, is described. The method employed depends, in part, upon an estimate of the true relativistic mass increase experienced by electrons within a highly compressed iron core, just prior to core collapse, and is significantly different from a more typical Chandrasekhar mass limit approach. This technique produced a maximum stellar iron core mass value of 2.69 x 10³⁰ kg (1.35 solar masses). This mass value is very near to the typical mass values found for neutron stars in a recent survey of actual neutron star masses. Although slightly lower and higher neutron star masses may also be found, lower mass neutron stars are believed to be formed as a result of enhanced iron core compression due to the weight of non-ferrous matter overlying the iron cores within large stars. And, higher mass neutron stars are likely to be formed as a result of fallback or accretion of additional matter after an initial collapse event involving an iron core having a mass no greater than 2.69 x 10³⁰ kg.

1 table, 18 ref

007351   Dubey S C;Mishra A P (Physics Dep, Government Girl's College, Sidhi-486 661) : Study of the solar wind streams associated with intense geomagnetic storms. Bull Astr Soc India 2001, 29(2), 127-34.

A set of 50 intense geomagnetic storms with time duration <62> 3 for during the solar maximum was period (1989-91) of solar cycle 22 have been analyzed. The study has a unique importance because the maximum phase of solar cycle 22 solar peaks exceptional containing compared to previous 21 solar cycles. Recent work demonstrated some important characteristics and different solar and interplanetary associations of 50 selected storm events. Out of 50 storm events, it has been found that maximum numbers of intense geomagnetic storms are associated with transient disturbances in solar wind streams, which cause strong interplanetary shocks in interplanetary medium, whereas, a few number of intense geomagnetic storms are associated with corotating flows in solar wind streams. Two intense geomagnetic storm events associated with corotating flows and transient disturbances respectively have been described and has beenconcluded that kind of solar wind does not effect the general characteristics and variation trends of different phases of storms. The association of supersonic shocks and magnetic clouds with intense geomagnetic storms have also been discussed.

2 illus, 1 table, 19 ref

007350   Caranicolas N D (Physics Dep, Section of Astrophysics, Astronomy and Mechanics, University of Thessa, 540 06 Thessaloniki, Greece) : Connecting global to local parameters in barred galaxy models. J Astrophys Astr 2002, 23(3-4), 173-83.

Presents connections between global and local parameters in a realistic dynamical model, describing motion in a barred galaxy. Expanding the global model in the vicinity of a stable Lagrange point, finds the potential of a two-dimensional perturbed harmonic oscillator, describes local motion near the centre of the global model. The frequencies of oscillations and the coefficients of the perturbing terms are not arbitrary but are connected to the mass, the angular rotation velocity, the scale length and the strength of the galactic bar. The local energy is also connected to the global energy. A comparison of the properties of orbits in the global and local potential is also made.

6 illus, 16 ref

007349   Bhattacharya D (NO, Raman Research Institute, Bangalore-560 080) : Flat spectrum gamma ray burst afterglows. Bull Astr Soc India 2001, 29(2), 107-14.

Temporal behaviour of GRB afterglow light curve is derived for the case where the electron energy distribution is relatively hard, with the power-law index plying between 1.0 and 2.0. It is shown that the expected behaviour will be the same as that for p <62> 2.0 if the upper cutoff in the electron energy distribution evolves in direct proportion to the bulk Lorentz factor of the blast wave.

22 ref

007348   Bagla J S (NO, Harish-Chandra Research Institute, Chhatnag Road, Jhunsi) : TreePM: a code for cosmological N-body simulations. J Astrophys Astr 2002, 23(3-4), 185-96.

Describes the TreePM method for carrying out large N-Body simulations to study formation and evolution of the large scale structure in the Universe. This method is a combination of Barnes and Hut tree code and Particle-Mesh code. It combines the automatic inclusion of periodic boundary conditions of PM simulations with the high resolution of tree codes. This is done by splitting the gravitational force into a short range and a long range component. Describes the splitting of force between these two parts.

4 illus, 1 table, 17 ref

006221   Sundara Raman K;Ramesh K B;Selvendran R (NO, Indian Institute of Astrophysics, Kodaikanal-624 103) : Spot and filament rotation in a sigmoidal flare. Bull Astr Soc India 2001, 29(1), 77-88.

The role played by the rotation of the umbrae in a sunspot with respect to the Hα filament in inducing magnetic shear for the sigmoidal brightening is reported. Carried out these studies by using photoheliogram and filtergram data. In the absence of vector magnetogram at Kodaikanal, an alternative method has been attempted to evaluate shear by carefully analyzing the photospheric and chromosphric environment of the solar active regions. it has been found that a large value of shear change observed in the active region is responsible for the triggering of a sigmidal related flare.

5 illus, 2 tables, 37 ref

006220   Stalin C S et al (NO, State Observatory, Manora Peak, Naini Tal-263 129) : Seeing and microthermal measurements near Devasthal top. Bull Astr Soc India 2001, 29(1), 39-52.

Microthermal measurements show that most of the contribution to seeing comes from the - - 18 m slab of the atmosphere with a mean value of 0."86. A significant decrease in turbulence over the height of the mast is noticed with a mean value of telescope at a height of 0."22 for the 12 - 18 m slab. A seeing of <126> 0."6 can be achieved by locating the telescope at a height of <126> 13 m above the ground.

8 illus, 4 tables, 13 ref