Indian Journal of Pure and Applied Physics

ISSN: 0019-5596

 

CODEN:IJOPAU 41(4) 249-336(2003)
VOLUME 41 NUMBER 4  APRIL  2003

 

CONTENTS

 

Nuclear Physics

Comparison of calibration procedures of iridium-192 sources used in high dose rate brachytherapy system

Alok Kumar *, Sudama Singh & Sushma Agrawal

 

 

253

Atomic and Molecular Physics

Spectral and normal coordinate analysis of 5,6-dihydro-5-methyl uracil

V Krishnakumar* & R Ramasamy

 

258

Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics

Effect of mass transfer on free convection in MHD flow of a viscous fluid

Atul Kumar Singh

 

262

Acoustic and solvation behaviour of N-iodoacetamide in water+DMSO and water+ CH3CN

J Ishwara Bhat* & N S Shree Varaprasad

275

Physics of Gases, Plasmas and Electric Discharges

Statistical mechanics and thermodynamics for a mixture of bosons and fermions

K M Khanna* & Ayodo Y Kennedy

 

280

Parametric instability of a lower hybrid wave in a dusty plasma

J K Sharma & J Parashar*

290

Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties

Comparative dielectric study of mono, di and trihydric alcohols

R J Sengwa

 

295

Pseudopotential dependence of supercondctuing state parameters of Be-Al metallic glasses

Smita Sharma, Haniph Khan & K S Sharma

301

Preparation, characterization and dielectric studies of K1-xNaxNbO3

Manish Uniyal, K Singh,Sunil Bhatt, S C Bhatt, R P Pant, D K Suri & B S Semwal*

305

Simple device, technique-cum-software for measurement of refractive index of liquid medium using 00 grade slip-gauge concept

Mrityunjay Karfa*, Mukesh Kumar, Vijay Kumar, Arif Sanjid &Shampa Karfa

310

Study of pulse dispersion and spot-sizes in simple and multimode nearly graded optical fibres

Y K Chaudhari, E G Nehete, I I Pattanashetti, U S Raikar & M K Soudagar*

314

Magnetic fluid based separator: Design and development

 Kinnari Parekh

319

Geophysics, Astronomy and Astrophysics

Scaling theory and dimensional arguments for periodic solutions of spring-block model

Mohammad Reza Sarkardei* & Roy L Jacobs

 

323

News Scan

Advances in nanotechnology and Raman spectroscopy

J B Dhawan

 

331

Errata

332

*The corresponding author has been indicated by (*) mark in case of papers with more than one author

 

 

 

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April  2003, pp. 253-257

 

 

Comparison of calibration procedures of iridium-192
sources used in high dose rate brachytherapy system

Alok Kumar*, Sudama Singh & Sushma Agrawal*

*Radiation Oncology, Regional Cancer Centre, Indira Gandhi Institute of Medical Sciences, Patna

A N College, Patna

 

Received 16 August 2002; revised 20 February 2003; accepted 10 March 2003

 

 

Calibration of iridium-192 high dose rate (HDR) brachytherapy sources has been compared by using two independent systems. Two types of calibration systems, well-type chamber (SDS), and field dosimeter (0.6 cc graphite thimble) with nucletron calibration jig have been compared. A number of measurements have been performed to calibrate the six iridium-192 sources according to national/international protocol during the clinical half-life of the iridium-192 source. All influencing factors like room-scattering, positional errors and accuracy of source position etc. have been taken care of, because the accuracy of source position itself within the applicator can lead to an error of 1.2% for the radial distance of 10 cm used in the calibration jig. Taking the 0.6 cc graphite thimble results as reference, percentage root mean square error (RMS) value of 0.33% for well-type chamber has been observed. It has been found that, both the calibration systems are equally good and can determine accurate and quick source calibration with careful measurements. Further, it should be mandatory to calibrate the source, prior to use of the source for the treatment of patients.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 258-261

 

 

Spectral and normal coordinate analysis of
5,6-dihydro-5-methyl uracil

V Krishnakumar & R Ramasamy*

Post Graduate Department of Applied Physics, Nehru Memorial College, Puthanampatti 621 007

*Department of Physics, Shanmugha College of Engineering, Tirumalaisamudram 613 402

 

Received 25 June 2002; accepted 10 March 2003

 

 

The FTIR spectrum of 5,6-dihydro-5-methyl uracil has been recorded in the region 4000-100 cm-1 and the normal coordinate analysis has been carried out by assuming Cs point group symmetry. All the normal modes of vibrations are assigned and calculations of potential energy distribution are also performed.

 

 

 

 

Indian J Pure & Applied Physics

Vol. 41, April  2003, pp. 262-274

 

 

Effect of mass transfer on free convection in
MHD flow of a viscous fluid

Atul Kumar Singh

Department of Mathematics, VSSD College, Kanpur 208 002

 

Received 31 October 2001; revised 29 April 2002; accepted 16 July 2002

 

 

The present study deals with effect of mass transfer on free convective flow of a viscous, electrically conducting fluid, through a porous medium, past an infinite vertical porous plate with constant suction, under the influence of uniform magnetic field, applied normal to the plate. The problem is solved, analytically, for velocity, temperature, concentration field and the expressions for skin-friction, rate of heat and mass transfer, has been obtained. The results obtained have been presented, numerically, through graphs and tables for externally cooled plate (Gr>0) and externally heated plate (Gr<0), to observe the effects of various parameters.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 275-279

 

 

Acoustic and solvation behaviour of N-iodoacetamide
in water + DMSO and water + CH3CN

J Ishwara Bhat & N S Shree Varaprasad

Department of Chemistry, Mangalore University, Mangalagangothri  574 199

E-mail : bhatij@yahoo.com

 

Received 16 September 2002; revised 1 February 2003; accepted 10 February 2003

 

 

The ultrasonic velocity and density at different concentrations of N-iodoacetamide in water, DMSO, CH3CN and different compositions (V/V) of  H2O + DMSO and H2O + CH3CN have been measured at 303 K. The data obtained are used to evaluate adiabatic compressibility, apparent molar compressibility, intermolecular free length, specific acoustic impedance, relative association and solvation number. These results was used to calculate limiting molar compressibility f0k. Guckers relation has been verified. Formation of complex at 50% DMSO and 20% CH3CN has been identified. These data are utilized in the qualitative study of ion-ion and ion-solvent interactions.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 280-289

 

 

Statistical mechanics and thermodynamics for
a mixture of bosons and fermions

K M Khanna1 & Ayodo Y Kennedy2

Department of Physics, Moi University, Box 1125 Eldoret, Kenya

E-mails: 1. profkmkhanna@hotmail.com 2. yudah2000@yahoo.com

 

Received 30 July 2002; accepted 8 November 2002

 

 

A statistical distribution model is developed for a mixture of bosons and fermions with different concentrations. The bosons and fermions are assumed to be interacting via a pair interaction. The most probable distribution  in energy and the partition function are derived. Thermodynamic quantities such as entropy, internal energy and specific heat are obtained in terms of the partition function. The values of the internal energy, specific heat and entropy increase as the concentration of helium-3 in the mixture decreases.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 290-294

 

 

Parametric instability of a lower hybrid wave in a dusty plasma

J K Sharma & J Parashar

Department of Applied Physics, Samrat Ashok Technological Institute, Vidisha (MP) 464 001

 

Received 15 January 2002; revised 19 September 2002; accepted 2 January 2003

 

 

Dust acoustic mode in a magnetized dusty plasma is strongly modified by the presence of a high amplitude lower hybrid wave. The non-linear coupling between the two produces two lower hybrid sidebands. The latter, in conjunction with the pump lower hybrid wave, exerts a ponderomotive force on the electrons, driving the low frequency dust-acoustic mode. The variations in the charge of the dust due to electron and ion attachment introduce linear damping in the high frequency modes. At high powers, when the growth rate exceeds the frequency of the dust-acoustic mode, the parametric process goes over to a reactive quasimode decay.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 295-300

 

 

Comparative dielectric study of mono, di and trihydric alcohols

R J Sengwa

Microwave Research Laboratory, Department of Physics, JNV University, Jodhpur 342 005

 

Received 19 August 2002, revised 20 January 2003; accepted 25 March 2003

 

 

Measured values of dielectric permittivity e and dielectric loss e of ethyl alcohol (monohydric alcohol), ethylene glycol (dihydric alcohol) and glycerol (trihydric alcohol) over the whole frequency range of dielectric absorption i..e. ~10MHz to 20 GHz, at 25 C have been reported. The values of e and e of de-ionized water have also been reported in the same frequency range. The dielectric dispersion behaviour of ethylene glycol obey the Cole-Cole model while for ethyl alcohol and water molecules it can be described by Debye model. In case of glycerol, dielectric dispersion shows the Cole-Davidson type dielectric dispersion. The static dielectric constant eo, high frequency limiting dielectric constant e, average relaxation time to, dielectric distribution parameter a or b, free energy of activation DFt and Kirkwood correlation factor g have been determined for these hydrogen-bonded liquids. The values of eo and to are interpreted in terms of number of carbon atoms and the number of hydroxyl group/s present in the molecular structure. The effect of viscosity and intermolecular association on the average relaxation time of these molecules has been recognized. Intramolecular group rotations due to breaking and reforming of hydrogen bonds have also been discussed by considering the observed values of e-nD2 (nD, square of refractive index) and the corresponding dielectric dispersion models of these liquids containing different number of hydroxyl groups in their molecular structures.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 301-304

 

 

Pseudopotential dependence of superconducting state
parameters of Be-Al metallic glasses

Smita Sharma, Haniph Khan1 & K S Sharma2

Department of Physics, Government Dungar College, Bikaner, Rajasthan 334 001

1Department of Physics, MSJ Government College, Bharatpur, Rajasthan 321 001

2OSD, Higher Education, Government of Rajasthan, Jaipur, Rajasthan

 

Received 28 November 2002; revised 21 February 2003; accepted 11 March 2003

 

 

The BCS-Eliasberg-McMillan model for the metallic superconductors has been extended for the theoretical investigation of superconductivity in metallic glasses and has been used to obtain superconducting state parameters, i.e. electron-phonon coupling strength (l), Coulomb pseudopotential (*), transition-temperature (Tc), isotope effect exponent (a) and effective interaction strength (NOV) of metallic glasses. The binary system Be1-c Alc (at c=10 and 30 at %) has been investigated by employing three different forms of pseudopotential in conjunction with RPA form of dielectric screening. It is observed that, the present formulation almost reproduces the experimental Tc values for the two glasses. It has also been observed that, the Rowell's Tc equation, predicted for elemental superconductors, does not work well for metallic glasses.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 305-309

 

 

Preparation, characterization and dielectric studies of K1-xNaxNbO3

Manish Uniyal, K Singh, Sunil Bhatt, S C Bhatt, R P Pant*, D K Suri*& B S Semwal

Dielectric and Ultrasonic Laboratory, Department of Physics, HNB Garhwal University, Srinagar, Garhwal 246 174

*National Physical Laboratory, New Delhi 110 012

 

Received 8 October 2002; revised 2 January 2003; accepted 31 January 2003

 

 

Ceramic pellets of K1-xNaxNbO3 system (for x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7) have been prepared by solid-state reaction method and sintering process. The prepared samples were characterized by XRD technique. All prepared samples show orthorhombic structure at room temperature. Frequency variations of dielectric constant, loss tangent, and electrical conductivity have been investigated, at room temperature, in the frequency range 1-40 MHz. It is observed that, dielectric constant decreases as sodium is mixed by a step of 10 % in potassium niobate.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 310-313

 

 

Simple device, technique-cum-software for measurement
of refractive index of liquid medium using
00 grade slip-gauge concept

Mrityunjay Karfa, Mukesh Kumar, Vijay Kumar & Arif Sanjid

Dimension Metrology Section, National Physical Laboratory, New Delhi 110 012

and

Shampa Karfa

Maharshi Dayanand University, Study Centre, C543, Vikas Puri New Delhi 110 018

 

Received 21 May 2002; revised 27 December 2002; accepted 15 January 2003

 

 

It is possible to substitute relatively large length measurements by far smaller length measurements, by use of 00 grade slip-gauge concept, thereby curtailing temperature-affected (expansion coefficient induced) error, proportionately, and to quite a low level. The suggested technique utilizes the advantage. Thus, accrued and improved refractive index values of various liquid medium can be obtained because of greater offsetting of temperature-affected length measurement errors.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 314-318

 

 

Study of pulse dispersion and spot-sizes in single and multimode nearly graded optical fibers

Y K Chaudhari & E G Nehete

Department of Physics, Bhusawal Arts, Science. & PO Nahata Commerce College, Bhusawal

I I Pattanshetti & U S Raikar

Department of Physics, Karnatak University, Dharwad

and

M K Soudagar

Department of Physics, Shivaji University, Kolhapur  416 004

 

Received 8 October 2001; revised 23 January 2003; accepted 28 February 2003

 

 

Effect of small departures in the graded index profiles of optical fibers on the pulse-widths, field distributions and spot-sizes of LP01 mode has been examined. Expressions for s-intermodal and - intramodal pulse-widths are obtained for multimode graded fibers having a flat continuation in their index profiles. The field distribution of LP01 mode in single mode nearly parabolic fiber is determined by solving the wave equation and near field rms and Petermann - 2 spot-sizes are obtained. The calculated s-values are found to consistently increase both with the increase in distortion in a given a-profile and profile dispersion in index profiles with a 3. For a given v-number, the distortion effect leads to a decrease in either spot-size; also the rms spot-size is larger in magnitude than Petermann - 2 spot-size for a given distortion.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 319-322

 

 

Magnetic fluid based separator: Design and development

Kinnari Parekh

Laboratory of Magnetic Fluids, Department of Physics, Bhavnagar University, Bhavnagar 364 002

 

Received 24 December 2002; revised 27 January 2002; accepted 10 February 2003

 

 

Salient features of a magnetic fluid based separator, which can be used to recover certain non-magnetic materials from waste materials like automobile scraps, industrial wastes, household electrical appliances, etc., have been described. The magneto-hydrostatic separator is built using the phenomenon of levitation of non-magnetic objects submerged in a magnetic fluid when influenced by a gradient magnetic field. A prototype model is fabricated in the laboratory, using permanent ferrite magnets. The detailed study about the geometry and requirement of properties of magnetic fluid are discussed. The test results  of this model are also described.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 323-330

 

 

Scaling theory and dimensional arguments for
periodic solutions of spring-block model

Mohammad Reza Sarkardei1,2 & Roy L Jacobs1

1Mathematics Department, Imperial College of Science, 180 Queens Gate, London, SW7 2BZ, UK

2Physics Department, Az-Zahra University, Vanak, Tehran, 19834, Iran

 

Received 20 September 2002; revised 18 February 2003; accepted 6 March 2003

 

 

Earlier, the authors have studied a one-dimensional version of the Burridge-Knopoff model [Burridge R & Knopff L, Bull Seismol Soc Am, 57 (1967) 341] of N-site chain of spring-blocks with stick-slip dynamics. Their numerical analysis and computer simulations lead to a set of different results corresponding to different boundary conditions [Gutenberg B & Richter C F, Ann Geofis, 9 (1956) 1]. The authors showed that, there are stable periodic solutions in a parameter space. They have presented elsewhere, arguments to justify the occurrence of lower edges of the window [Carlson J M & Langer J S, Phys Rev Lett, 62 (1989) 2632]. The authors follow here, the same arguments and show that the lower and upper edges of the window can be understood in terms of simple scaling arguments and can be presented as a function of two dimensionless parameters. They try to understand the origin of the results and give a theory to explain them. An improved formula for lower threshold driving velocity will be presented, which is in a good agreement with their numerical experiments inside the parameters window of periodic solutions. Also, they discuss different types of instability occurring in the system.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, April 2003, pp. 331-331

 

 

NEWS SCAN

 

Advances in nanotechnology & Raman spectrsocpy

 

 

Raman scattering is achieved by sending light through a sample and measuring how the light is scattered. The technique can provide more detailed structural information about nanostructure than other imaging techniques, because it measures unique vibrational modes of the material being studied. Though many new methods have been introduced such as scanning probe techniques, optical tweezers and atomic force microscopy. But, advances in nanotechnology rely more on studies, which can manipulate individual structures on the nanoscale. Although these ultra-high resolution-imaging techniques can detect the presence of very small objects, they cannot actually see them.