008850   Verma M K;Ayyer A;Debliquy O;Shishir Kumar; Chandra A V (Dep of Phys, Indian Inst of Technol, Kanpur-208 016, Email: mkv@iitk.ac.in) : Local shell-to-shell energy transfer via nonlocal interactions in fluid turbulence. Pramana J Phys 2005, 65(2), 297-310.

Analytically computes the strength of nonlinear interactions in a triad, and the energy exchanges between wave-number shells in incompressible fluid turbulence. The computation has been done using first-order perturbative field theory. In three dimensions, magnitude of triad interactions is large for nonlocal triads, and small for local triads. However, the shell-to-shell energy transfer rate is found to be local and forward. This result is due to the fact that the nonlocal triads occupy much less Fourier space volume than the local ones. The analytical results on three-dimensional shell-to-shell energy transfer match with their numerical counterparts. In two-dimensional turbulence, the energy transfer rates to the nearby shells are forward, but to the distant shells are backward; the cumulative effect is an inverse cascade of energy.

6 illus, 25 ref

008849   Verma K K;Soni K R (Microwave Laboratory Dep of Phys, Malaviya Natn Inst of Technol, Jaipur-302 017, Email: kkverrnaphd@rediffmail.com) : Theoretical study of two-element array of equilateral triangular patch microstrip antenna on ferrite substrate. Pramana J Phys 2005, 65(3), 501-12.

The radiation characteristics of a two-element array of equilateral triangular patch microstrip antenna on a ferrite substrate are studied theoretically by considering the presence of bias magnetic field in the direction of propagation of electromagnetic waves. It is found that the natural modes of propagation in the direction of magnetic field are left- and right-circularly polarized waves and these modes have different propagation constants. In loss-less isotropic warm plasma, this array antenna geometry excites both electromagnetic (EM) and electroacoustic plasma (P) waves in addition to a nonradiating surface wave. In the absence of an external magnetic field, the EM- and P-waves can be decoupled into two independent modes, the electroacoustic mode is longitudinal while the electromagnetic mode is transverse. The far-zone EM-mode and P-mode radiation fields are derived using vector wave function techniques and pattern multiplication approaches. The results are obtained in both plasma medium and free space. Some important antenna parameters such as radiation conductance, directivity and quality factor are plotted for different values of plasma-to-source frequency.

10 illus, 4 tables, 11 ref

008848   Upadhyaya K S;Singh A K;Pandey A;Pathak S N (Dep of Phys, K.N. Government P.G. Coll Gyanpur, Sant Ravidas Nagar, Bhadohi-221 304) : Lattice vibrational properties of transition metal carbides (TiC, ZrC and HfC). Pramana J Phys 2005, 64(2), 299-304.

Lattice vibrational properties of transition metal carbides (TiC, ZrC and HfC) have been presented by including the effects of free-carrier doping and three-body interactions in the rigid shell model. The short-range overlap repulsion is operative up to the second neighbour ions. An excellent agreement has been obtained between theory and experiment for their phonon dispersion curves and Debye temperature variations. It is concluded that the contributions of free-carrier doping and three-body interactions are essential for the description of the lattice dynamics of these carbides.

4 illus, 1 table, 23 ref

008847   Unnikrishnan C S (Gravitation Grp, Tata Inst of Fundamental Res, Homi Bhabha Road, Mumbai-400 005, Email: unni@tifr.res.in) : The incompatibility between local hidden variable theories and the fundamental conservation laws. Pramana J Phys 2005, 65(3), 359-79.

Discusses in detail the result that the Bell's inequalities derived in the context of local hidden variable theories for discrete quantized observables can be satisfied only if a fundamental conservation law is violated on the average. This result shows that such theories are physically nonviable, and makes the demarcating criteria of the Bell's inequalities redundant. Shows that a unique correlation function can be derived from the validity of the conservation law alone and this coincides with the quantum mechanical correlation function. Thus, any theory with a different correlation function, like any local hidden variable theory, is incompatible with the fundamental conservation laws and space-time symmetries. The results are discussed in the context of two-particle singlet and triplet states, GHZ states, and two-particle double slit interferometry. Some observations on quantum entropy, entanglement, and nonlocality are also discussed.

5 illus, 11 ref

008846   Tripathi M N;Bhandari C M (Dep of Phys, Univ of Allahabad, Allahabad-211 002, Email: omrnadhav27@rediffmail.com) : Material parameters for thermoelectric performance. Pramana J Phys 2005, 65(3), 469-79.

The thermoelectric performance of a thermoelement is ideally defined in terms of the so-called figure-of-merit Z = α²σ/λ, where α, σ and λ refer respectively to the Seebeck coefficient, electrical conductivity and thermal conductivity of the thermoelement material. However, there are other parameters which are fairly good indicators of a material's thermoelectric 'worth'. A simple yet useful performance indicator is possible with only two parameters - energy gap and lattice thermal conductivity. This indicator can outline all potentially useful thermoelectric materials. Thermal conductivity in place of lattice thermal conductivity can provide some additional information about the temperature range of operation. Yet another performance indicator may be based on the slope of α vs. In σ plots, α plotted against In σ shows a linear relationship in a simplified model, but shows a variation with temperature and carrier concentration. Assuming that such a relationship is true for a narrow range of temperature and carrier concentration, one can calculate the slope m of α vs. In σ plots against temperature and carrier concentrations. A comparison between the variation of ZT and slope m suggests that such plots may be useful to identify potential thermoelectric materials.

5 illus, 2 tables, 19 ref

008845   Tomar B S;Babu K S;Sudarshan K;Tripathi R (Radiochemistry Div, Bhabha Atom Res Cent, Mumbai-400 085, Email: bstomar@apsara.barc.ercet.in) : Angular momentum transfer in incomplete fusion. Pramana J Phys 2005, 64(2), 221-7.

Isomeric cross-section ratios of evaporation residues formed in ¹²C+⁹³Nb and ¹⁶0+⁸⁹Y reactions were measured by recoil catcher technique followed by off-line γ-ray spectrometry in the beam energy range of 47.4-77.5 MeV for ¹²C and 57.6-93.3 MeV for ¹⁶O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical de-excitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.

4 tables, 22 ref

008844   Tiwari V B;Mishra S R;Rawat H S;Singh S;Ram P;Mahendale S C (Laser Phys Div, Cent for Advd Technol, Indore-452 013, Email: vbtiwari@cat.ernet.in) : Laser frequency stabilization and large detuning by Doppler-free dichroic lock technique: Application to atom cooling. Pramana J Phys 2005, 65(3), 403-11.

Presents results of a study of frequency stabilization of a diode laser (A = 780 nm) using the Doppler-free dichroic lock (DFDL) technique and its use for laser cooling of atoms. Quantitative measurements of frequency stability were performed and the Allan variance was found to be 6.9 x 10^-11 for an averaging time of 10 s. The frequency-stabilized diode laser was used to obtain the trapping beams for a magneto-optic trap (MOT) for Rb atoms. Using the DFDL technique, the laser frequency could be locked over a wide range and this enabled measurement of detuning dependence of the number and temperature of cold atoms using a relatively simple experimental set-up.

6 illus, 13 ref

008843   Tiwari R K (Dep of Math and Computer Applic, Government Model Sci Coll, Rewa 486 001) : Collineations of the curvature tensor in general relativity. Pramana J Phys 2005, 65(1), 43-8.

Curvature collineations for the curvature tensor, constructed from a fundamental Bianchi Type-V metric, are studied. Concern with a symmetry property of space-time which is called curvature collineation, and briefly discusses the physical and kinematical properties of the models.

18 ref

008842   Thakur A;Negi N S;Ahluwalia P K (Dep of Phys, Himachal Pradesh Univ, Shimla-171 005, Email: anil-t2001@yahoo.com) : Electrical resistivity of NaPb compound-forming liquid alloy using ab initio pseudopotentials. Pramana J Phys 2005, 65(2), 349-58.

Study of electrical resistivity of compound-forming liquid alloy, NaPb, is presented as a function of concentration. Hard sphere diameters of Na and Pb are obtained through the interionic pair potentials evaluated using Troullier and Martins ab initio pseudopotential, which have been used to calculate the partial structure factors S(q). Considering the liquid alloy to be a ternary mixture, Ziman formula, modified for complex formation has been used for calculating resistivity of binary liquid alloys. Form factors are calculated using ab initio pseudopotentials. The results suggest that Ziman formalism, when used with ab initio pseudopotentials, are quite successful in explaining the electrical resistivity data of compound-forming binary liquid alloys.

6 illus, 2 tables, 34 ref

008841   Suzuki A;Dutt R;Bhaduri R K (Dep of Phys, Tokyo Univ of Sci, Tokyo 162-8601, Japan, Email: akira@rs.kagu.tus.ac.jp) : Supersymmetric quantum mechanics for two-dimensional disk. Pramana J Phys 2005, 65(1), 49-59.

Infinte square well potential in one dimension has a smooth supersymmetric partner potential which is shape invariant. Study generalization of this to two dimensions by constructing the supersymmetric partner of the disk billiard. Author has find that the property of shape invariancc is lost in this case. Nevertheless, the WKB results are significantly improved when SWKB calculations are performed with the square of the superpotential. It has also study the effect of inserting a singular flux line through the center of the disk.

6 illus, 1 table, 23 ref

008840   Srinivasan R (Raman Res Inst, , C V Raman Avenue, Sadashivanagar, Bangalore-560 080, Email: rsv@rri.res.in) : Spintronics:principles. Resonance 2005, 10(9), 53-62.

Spintronics is creating new excitement in the scientific world. In part 1 of this two part article, Deal in an elementary fashion with the principles of spintronics.

7 illus, 15 ref

008839   Solunke M B;Sharma P U;Pandya M P;Lakhani V K;Modi K B;Venugopal Reddy P;Shah S S (Dep of Phys, Dr B.A.M. Univ, Aurangabad-431 004, Email: kunalbmodi2003@yahoo.com) : Ultrasonic studies of aluminium-substituted Bi(Pb)-2223 superconductors. Pramana J Phys 2005, 65(3), 481-90.

The compositional dependence of elastic properties of Al³⁺-substituted Bi(Pb)-2223 superconducting system with the general formula Bi_1.7-xAl_xPb_0.3Sr₂Ca_2-Cu₃O_y (x = 0.0, 0.1, 0.2 and 0.3) have been studied by means of ultrasonic pulse transmission (UPT) technique at 1 MHz (300 K). The elastic moduli of the specimens are computed and corrected to zero porosity. The observed variation of elastic constants with aluminium substitution has been explained on the basis of the strength of interatomic bonding. The applicability of heterogeneous metal mixture rule for estimating elastic constants and transition temperature has been tested.

2 illus, 5 tables, 19 ref

008838   Singh J;Chandra R;Raina P K;Rath P K (Dep of Phys, Univ of Lucknow, Lucknow-226 007, Email: pkrath_lu@yahoo.co.in) : Two-neutrino double β decay of <. Pramana J Phys 2005, 65(3), 517-22.

The two-neutrino double beta decay of ⁹⁶Zr isotope for 0⁺ → 2⁺ transition has been studied in the PHFB model. In the earlier work, the reliability of the intrinsic wave functions of ⁹⁶Zr and ⁹⁶Mo isotopes has been established by obtaining an overall agreement between a number of theoretically calculated spectroscopic properties as well as half-lives of 2v ββ decay for 0⁺ → 0⁺ transition and the available experimental data. In the work, the half-life of 2v <98>β decay for 0⁺ → 2⁺ transition T^2v_1/2(0⁺ → 2⁺) has been calculated using the same set of intrinsic wave functions.

1 table, 25 ref

008837   Shukla A;Raina P K;Rath P K (Dep of Phys and Meteorology, Indian Inst of Technol, Kharagpur-721 302, Email: ashukla@iphy.iitgp.ernet.in) : Exploring effective interactions through transition charge density study of <. Pramana J Phys 2005, 64(2), 207-20.

Transition charge densities (TCD) for 0⁺ → 2⁺₁ excitation have been calculated for ^70,72,74,76Ge nuclei within microscopic variational framework employing 2p_3/2, 1f_5/2 2p_1/2 and 1g_9/2 valence space. The calculated TCDs for different monopole variants of Kuo interaction are compared with available experimental results. Other sys-tematics like reduced transition probabilities B(E2) and static quadrupole moments Q(2) are also presented. It is observed that the transition density study acts as a sensitive probe for discriminating the response of different parts of effective interactions.

1 illus, 40 ref

008836   Shinkevich S;Studenikin A (Dep of Theoretical Phys, Moscow St Univ, 119992, Moscow, Russia, Email: studenik@srd.sinp.msu.ru) : Relativistic theory of inverse beta-decay of polarized neutron in strong magnetic field. Pramana J Phys 2005, 65(2), 215-44.

Relativistic theory of the inverse beta-decay of polarized neutron, v_e + n → p + e^-, in strong magnetic field is developed. For the proton wave function author use C the exact solution of the Dirac equation in the magnetic filed that enables one to account exactly for effects of the proton momentum quantization in the magnetic field and also for the proton recoil motion. The effect of nucleons anomalous magnetic moments in strong magnetic fields is also discussed. Examin the cross-section for different energies and directions of propagation of the initial neutrino accounting for neutron polarization. It is shown that in the super-strong magnetic field the totally polarized neutron matter is transparent for neutrinos propagating antiparallel to the direction of polarization. The developed relativistic approach can be used for calculations of cross-sections of the other URCA processes in strong magnetic fields.

11 illus, 48 ref

008835   Shankar P N;Kidambi R (Computational and Theoretical Fluid Dynamics Div, Natn Aerospace Laboratories, Bangalore-560 017, Email: pn_shankar55@rediffmail.com) : The constancy of the contact angle in viscous liquid liquid motions with pinned contact lines. Pramana J Phys 2005, 65(1), 107-16.

Considers motion initiated in a viscous liquid in a smooth walled container. The liquid is initially at rest under uniform pressure from an inert gas of negligible inertia. It has shown that if the contact line is pinned and the interface is single valued, the contact angle has to remain constant throughout the motion. This is true even for motions of finite amplitude. Some implications of the result are discussed.

10 ref

008834   Shankar P N (NO, , 33/1 Kasturba Road Cross, Bangalore-560 001, Email: pn_shankar55@rediffmail.com) : The shape of an axisymmetric bubble in uniform motion. Pramana J Phys 2005, 65(3), 437-55.

Considers in a frame fixed to a bubble translating with steady speed U the inviscid, axisymmetric, irrotational motion of the liquid past it. If all speeds are normalized by U and lengths by T/1/2ρU², where T is the surface tension of the liquid-bubble interface, it can be shown that the unknown bubble shape and field depend on a single parameter Γ = (p_b - p_∞)/1/2 ρU², 1 alone, where the pressures are the ones in the bubble and far away respectively. When is very large the bubble is almost spherical in shape while for Γ ≤ Γ* ≈ - 0.315, bubbles whose exteriors are simply connected do not exist. Solve the non-linear, free boundary problem for the whole range Γ* <60> Γ <60> ∞ by the use of an analytical representation for the bubble shape, a surface singularity method to compute potential flows and a generalized Newton's method to continue in Γ. Apart from providing explicit representations for bubble shapes and detailed numerical values for the bubble parameters, showed that the classical linearized solution for large Γ is a very good approximation, surprisingly, to as low values of Γ as 2. Also shows that Miksis et al [1] is inaccurate over the whole range and in serious error for large and small Γ. These have been corrected.

9 illus, 3 tables, 28 ref

008833   Sarwe S B;Saraykar R V (Dep of Math, S.F.S. Coll, Seminary Hill, Nagpur-440 006, Email: sbsarwe_ngp@sancharnet.in) : Stability of naked singularity arising in gravitational collapse of Type I matter fields. Pramana J Phys 2005, 65(1), 17-33.

Considering gravitational collapse of Type I matter fields, author prove that, given an arbitrary C²-mass function M(r,v) and a C¹ -function h (r,v) (through the corresponding C¹-metric function v (t r)), there exist infinitely many choices of energy distribution function b(r) such that the 'true' initial data (M,h (r,v)} leads the collapse to the formation of naked singularity. Further provs that the occurrence of such a naked singularity is stable with respect to small changes in the initial data. It remarks that though the initial data leading to both black hole (BH) and naked singularity (NS) form a 'big' subset of the true initial data set, their occurrence is not generic. The terms 'stability' and 'genericity' are appropriately defined following the theory of dynamical systems. The particular case of radial pressure pr(r) has been illustrated in details to get a clear picture of how naked singularity is formed and how, it is stable with respect to initial data.

13 ref

008832   Roy A K (Dep of Chem and Biochem, Univ of California, Los Angeles, CA 90095, USA, Email: akroy(c)chem.ucla.edu) : The generalized pseudospectral approach to the bound states of the Hulthen and the Yukawa potentials. Pramana J Phys 2005, 65(1), 1-15.

Generalized pseudospectral (GPS) method is employed to calculate the bound states of the Hulthen and the Yukawa potentials in quantum mechanics, with special emphasis on higher excited states and stronger couplings. Accurate energy eigenvalues, expectation values and radial probability densities are obtained through a non-uniform and optimal spatial discretization of the radial Schrodinger equation. Results accurate up to thirteen to fourteen significant figures are reported for all the 55 eigenstates of both these potentials with n ≤ 10 for arbitrary values of the screening parameters covering a wide range of interaction. Furthermore, excited states as high as n= 17 have been computed with good accuracy for both these potentials. Excellent agreement with the available literature data has been observed in all cases. The n <62> 6 states of the Yukawa potential has been considerably improved over all other existing results currently available, while the same for Hulthen potential are reported for the first time. Excepting the 1s and 2s states of the Yukawa potential, the method surpasses the accuracy of all other existing results in the stronger coupling region for all other states of both these systems. This offers a simple and efficient scheme for the accurate calculation of these and other screened Coulomb potentials.

3 illus, 6 tables, 48 ref

008831   Rayaprol S;Sampathkumaran E V (Dep of Condensed Matter Phys and Material Sci, Tata Inst of Fundamental Res, Homi Bhabha Road, Colaba, Mumbai-400 005, Email: sampath@tifr.res.in) : Negative chemical pressure effects induced by Y substitution for Ca on the 'exotic' magnetic behavior of the spin-chain compound, Ca₃Co₂O₆. Pramana J Phys 2005, 65(3), 491-500.

The magnetic behavior of a solid solution, Ca_3-xY_xCo₂O₆, based on the 'exotic' spin-chain compound, Ca₃Co₂O₆, crystallizing in K₄CdCl₆-derived rhombohedral structure is investigated. Among the compositions investigated (x = 0.0, 0.3, 0.5, 0.75 and 1.0), single-phase formation persists up to x = 0.75, with the elongation of the c-axis. The investigations reveal that the temperature at which the 'so-called' 'partially disordered antiferromagnetic structure' sets in (which occurs at 24 K for the parent compound, x - 0.0) undergoes gradual reduction with the substitution of Y for Ca, attaining the value of about 2.2 K for the nominal x = 1.0. The trend observed in this characteristic temperature is opposite to that reported under external pressure, thereby establishing that Y substitution exerts negative chemical pressure. Anomalous steps observed in the isothermal magnetization at very low temperatures (around 2 K) for x = 0.0, which have been proposed to arise from 'quantum tunneling effects' are found to vanish by a small substitution (x = 0.3) of Y for Ca. Systematics in AC and DC magnetic susceptibility behavior with Y substitution for Ca have also been probed. Believes that the results involving the expansion of chain length without disrupting the magnetic chain may be useful to the overall understanding of the novel magnetism of the parent compound.

7 illus, 1 table, 14 ref

008830   Rao D K;Patel H S;Jain B;Gupta P K (Biomed Applics Sect, Cent for Advd Technol, Indore-452 013, Email: kdivakar@cat.ernet.in) : Time-gated optical imaging through turbid media using stimulated Raman scattering: Studies on image contrast. Pramana J Phys 2005, 64(2), 229-38.

Report the development of experimental set-up for time- gated optical imaging through turbid media using stimulated Raman scattering. The studies on the contrast of time-gated images show that for a given optical thickness, the image contrast is better for sample with lower scattering coefficient and higher physical thickness, and that the contrast improves with decreasing value of anisotropy parameters of the scatterers. These results are consistent with time-resolved Monte Carlo simulations.

8 illus, 18 ref

008829   Ramachandran R (The Inter-University Cent for Astronomy and Astrophys, Univ of Pune Campus, Pune-411 007, Email: rr@iucaa.ernet.in) : Chiral soliton model vs. pentaquark structure for ξ (1540). Pramana J Phys 2005, 65(3), 381-9.

The exotic baryon ξ⁺ (1540 MeV) is visualized as an expected (iso) rotational excitation in the chiral soliton model. It is also argued as a pentaquark baryon state in a constituent quark model with strong diquark correlations. Contrasts these two points of view; observes the similarities and differences between the two pictures. Collective excitation, the characteristic of chiral soliton model, points toward small mixing of representations in the wake of SU(3), breaking. In contrast, constituent quark models prefer near 'ideal' mixing, similar to ω - φ mixing.

19 ref

008828   Ram Kripal;Shukla A K (Dep of Phys, Univ of Allahabad, Allahabad-211 002, Email: akshukal10@rediffmail.com) : Absorption spectrum of Mn<. Pramana J Phys 2005, 65(1), 153-7.

Optical absorption is a tool to investigate the site symmetry of metal ion and associated distortion in doped single crystals. It provides the energy of different orbital levels of metal ion and separation among them. Mn²⁺ ions in various single crystals and glasses have been the subject of recent investigations [1-3]. Studied optical absorption spectra of Mn²⁺ doped diammonium hexaaquamagnesium (II) sulfate in order to obtain the energy level ordering using matrices of Tanabe and Sugano [4] and to discuss the associated distort ion.

5 illus, 1 table, 12 ref

008827   Rajan K G;Jestin Lenus A (Mater Sci Div, Indira Gandhi Cent for Atom Res, Kalpakkam 603 102, Email: kg@igcar.ernet.in) : X-ray excited optical luminescence studies on the system BaXY (X,Y=F, Cl, Br, I). Pramana J Phys 2005, 65(2), 323-38.

Reports the experimental observations on the x-ray excited optical luminescence (XEOL) along with the afterglow and colour center features found for the barium salts, represented by the formula, BaXY, where X and Y are the halides. The system thus consists of four dihalides (BaF₂, ... ,BaI₂) and six mixed halides (BaFCl,... ,BaBrI). To start with, it was found that on two of the binary halides of barium, BaClI and BaBrI, no literature exists, and so these were prepared for the first time and their crystal structures were determined. An X-ray generator of 3-kW rating was next coupled to a spectrometer via a high throughput fiberoptic sensor for recording the luminescence spectra under x-irradiation. Also presented are the observations on the BaXY compounds in which about 0.1 mole% of Eu²⁺ was doped, in order to study the efficiency between the prompt luminescence and the photostimulated luminescence in these compounds. The crystal structure varies from fluorite (BaF₂), to matlockite (BaFX) and finally to orthorhombic (BaCl₂, ..., BaBrI) for these compounds. Hence searching for systematics and empirical relations in the observed XEOL behaviour of these compounds is still a challenging problem.

2 illus, 2 tables, 47 ref

008826   Peng Y Z (Dep of Math, Huazhong Univ of Sci and Technol, Wuhan 430074, P. R. China, Email: yanzepeng@163.corn) : Exact periodic wave solutions to the generalized Nizhnik-Novikov-Veselov equation. Pramana J Phys 2005, 64(2), 159-69.

The extended mapping method with symbolic computation is developed to obtain exact periodic wave solutions to the generalized Nizhnik-Novikov-Veselov equation. Limit cases are studied and new solitary wave solutions and triangular periodic wave solutions are obtained. The method is applicable to a large variety of non-linear partial differential equations, as long as odd- and even-order derivative terms do not coexist in the equation under consideration.

6 illus, 16 ref

008825   Peng Y Z (Dep of Math, Huazhong Univ of Sci and Technol, Wuhan 430074, P.R. China, Email: yanzepeng@163.com) : Exact periodic waves and their interactions for the (2+1)-dimensional KdV equation. Pramana J Phys 2005, 65(2), 177-83.

By means of the singular manifold method we obtain a general solution involving three arbitrary functions for the (2+1)-dimensional KdV equation. Diverse periodic wave solutions may be produced by appropriately selecting these arbitrary functions as the Jacobi elliptic functions. The interaction properties of the periodic waves are investigated numerically and found to be nonelastic. The long wave limit yields some new types of solitary wave solutions. Especially the dromion and the solitoff solutions obtained possess new types of solution structures which are quite different from the basic dromion and solitoff ones reported previously in the literature.

3 tables, 30 ref

008824   Pathania Y;Ahluwalia P K (Dep of Phys, Himmachal Pradesh Univ, Shimla-171 005, Email: yogyatapathania@yahoo.com) : Molecular dynamics, study of two- and three-dimensional classical fluids using double Yukawa potential. Pramana J Phys 2005, 65(3), 457-68.

Carrie out a molecular dynamics simulation, of two- and three-dimensional double Yukawa fluids near the triple point. Compares some of the static and dynamic correlation functions with those of Lennard - Jones, when parameters occurring in double Yukawa potential are chosen to fit Lennard-Jones potential. The results are in good agreement. However, when repulsive and attractive parameters occurring in double Yukawa potential are varied, it found distinct differences in static and dynamic correlation functions. Also compare the two-dimensional correlation functions with those of three-dimensional to study the effect of dimensionality, near the triple point region.

7 illus, 3 tables, 12 ref

008823   Pandey J D;Dey R;Sanguri V;Chhabra J;Nautiyal T (Departmept of Chem, Univ of Allahabad, Allahabad 211 002, Email: drranjan@hotmail.com) : A comparative study of non-linearity parameter for binary liquid mixtures. Pramana J Phys 2005, 65(3), 535-40.

The investigation comprises of theoretical evaluation of acoustic non-linearity parameter, B/A for equimolar binary mixtures, viz. chlorobenzene or 1-chloronaphthalene with a series of normal alkanes (n-C_n, n = 6, 8, 10, 12, 14, 16), and with a series of highly branched alkanes (br-C_n, n = 6, 8, 12, 16), viz. 2,2-dimethylbutane (br-C₆), 2,2,4-trimethylpentane (br-Cs), 2,2,4,6,6-pentamethylheptane (br-C₁₂) and 2,2,4,4,6,8,8-heptamethylnonane (br-C₁₆). Tong and Dong method, ther-moacoustical method, Hartmann relation and Ballou relation have been employed to evaluate B/A. A comparative study of B/A values obtained from the aforementioned methods has been made. The results are discussed on the basis of structural orientations of normal and branched alkanes.

3 tables, 16 ref

008822   Pandey B;Verma H C (Dep of Phys, Indian Inst of Technol, Kanpur-208 016, Email: ncverma@utk.ac.in) : Phase changes in Fe_72-xAl₂₈Cr_x (x = 0, 2, 4, 6) alloys due to mechanical strain. Pramana J Phys 2005, 64(2), 281-90.

Fe_72-xAl₂₈Cr_x alloys (x = 0,2,4,6) are made by arc melting a mixture of constituent elements in stoichiometric proportion, in argon atmosphere. The ingots so obtained are filed to make powder samples thereby giving them substantial mechanical deformation. It is observed that as-powdered samples show hyperfine field distribution typical of α-phase, where the atoms are randomly distributed on the available sites. Annealing at 900°C for 60 h leads to preferential occupation of lattice sites by the atoms and this results in better defined groups of hyperfine magnetic field (HMF) which can be associated with specific configuration in the neighbourhood of probe iron atoms. The average HMF is found to decrease sharply with increasing Cr concentration even though the net chromium concentration remains low (≤ 6 at%). The results show that cold working on samples is very important in changing the atomic ordering and must be taken into account if properties of equilibrium phases are probed.

4 illus, 2 tables, 18 ref

008821   Pandey B P;Dutta A (NO, New York St Univ at Buffalo, New York 14214, USA, Email: bppandey02@yahoo.com) : The Bohm criterion for a dusty plasma sheath. Pramana J Phys 2005, 65(1), 117-24.

The formation of the sheath in a dusty plasma is investigated. The Bohm criterion is derived for two different cases: when electrons are in thermodynamic equilibrium and dust grains provide the immobile, stationary background and when both electrons and ions are in thermodynamic equilibrium and dust grains are moving. In the first case, Bohm criterion gets modified due to the fluctuation of the charge on the grain surface. In the second case, the collisional and Coulombic drag play important role in determining the Bohm criterion.

10 ref

008820   Nath P P;Sarkar S;Joarder R N (Dep of Phys, Jadavpur Univ, Kolkata-700 032, Email: rnj@juphys.ernet.in) : An effective pair potential for liquid semiconductor, Se: Structure and related dynamical properties. Pramana J Phys 2005, 65(1), 125-35.

Effective pair potential of liquid semiconductor Se is extracted from its experimental structure factor data using an accurate liquid state theory and this shows important basic features. A model potential incorporating the basic features of the structure factor extracted potential is suggested. This model potential is then used to describe through low-order perturbation theory, the structure and related dynamical properties like self-diffusion coefficient and shear viscosity of this complex liquid over a wide range of temperatures.

7 illus, 2 tables, 24 ref

008819   Narayana K R;Seetharami Reddy B;Raju S S; Seshi Reddy T;Lakshmi Narayana S;Premachand K;Rao B M;Murti M V R; Mombasawala L S (Dep of Nuclear Phys, Andhra Univ, Visakhapatnam-530 003, Email: bsr-au@yahoo.com) : Evidence for resonance electron transfer in photon excited X-ray satellite spectra of fluorine compounds. Pramana J Phys 2005, 65(2), 285-90.

KαL^-1/KαL⁰ intensity ratio of fluorine is measured in five fluorine compounds with a crystal spectrometer. An anomalous reduction of this intensity ratio was observed in KF and SrF2, which is attributed to resonance electron transfer from the metal ion to the spectator vacancy in the fluorine ion. KαL²/KαL⁰ intensity ratio of fluorine is also measured. The measured relative intensities are compared with the theoretical estimates of Aberg.

2 illus, 3 table, 9 ref

008818   Narasimha R (Roddam Narasimha Jawaharlal Nehru Cent for Advd Scientific Res Jakkur, , Bangalore-560 064, Email: raddam@cais.iisc.ernet.in) : The challenge of fluid flow what one can and cannot do. Resonance 2005, 10(9), 7-22.

Equations for an incompressible viscous fluid are water down. They assume that the fluid is continuous (no voids, for example), and that the state of internal stress in the fluid depends linearly on the local rate of strain that the fluid experiences during its motion. The principles of conservation of mass and momentum are then sufficient to obtain the partial differential equations that govern the motion: one expressing continuity or conservation of mass, and three scalar equations (constituting one vector equation) each of which expresses conservation of momentum in an independent direction. Because fluid velocity and pressure depend in general on both space and time, the governing equations are partial differential equations. The term that is responsible for the difficulty of solving these equations is what may be called the advective acceleration, written as (u. grad) u in the text. This term represents the acceleration experienced by a fluid particle, originally at a given position and time, as it moves a short interval of time later to a neighbouring position where the fluid velocity is slightly different. Because the increment in velocity and the distance travelled by the particle both depend on the velocity field, this advective acceleration is nonlinear in the fluid velocity. This nonlinearity has profound consequences, and results in all the complexities that we see in the motion of even such common fluids as air and water.

4 illus

008817   Nadgaran H;Elahi P (Dep of Phys, Coll of Sci Shiraz Univ, Shiraz 71454, Iran, Email: nadgaran@susc.ac.in) : The analytical investigation of the super-Gaussian pump source on the thermal, stress and thermo-optics properties of double-clad Yb:glass fiber lasers. Pramana J Phys 2005, 65(1), 95-105.

Fiber lasers have attracted considerable attention when their power can realistically be scaled to kilowatt level and beyond. Assum that the fiber core and first clad are exposed to a pump source with a super-Gaussian profile of order four. The effects of this non-uniform heat deposition on thermal, stress and thermo-optics properties such as temperature-dependent change of refractive index and thermally induced stress have been comprehensively studied and their equations analytically derived.

9 illus, 18 ref

008816   Morgan J A (NO, The Aerospace Corporation, P.O. Box 92957, Los Angeles, CA 90009, USA, Email: John.A.Morgan@aero.org) : Parity and the spin-statistics connection. Pramana J Phys 2005, 65(3), 513-6.

A simple demonstration of the spin-statistics connection for general causal fields is obtained by using the parity operation to exchange spatial coordinates in scalar product of a locally commuting field operator, evaluated at position x, with the same field operator evaluated at -x, at equal times.

20 ref

008815   Mohrhoff U (NO, Sri Aurobindo Int Cent of Educ, Pondicherry-605 002, Email: ujm@auromail.net) : The Pondicherry interpretation of quantum mechanics. Pramana J Phys 2005, 64(2), 171-85.

An overview of the Pondicherry interpretation of quantum mechanics is presented. This interpretation proceeds from the recognition that the fundamental theoretical framework of physics is a probability algorithm, which serves to describe an objective fuzziness (the literal meaning of Heiaenberg's term 'Unscharfe', usually mistranslated as 'uncertainty') by assigning objective probabilities to the possible outcomes of unperformed measurements. Although it rejects attempts to construe quantum states as evolving onto-logical states, it arrives at an objective description of the quantum world that owes nothing to observers or the goings-on in physics laboratories. In fact, unless such attempts are rejected, quantum theory's true ontological implications cannot be seen. Among these are the radically relational nature of space, the numerical identity of the corresponding relata, the incomplete spatio-temporal differentiation of the physical world, and the consequent top-down structure of reality, which defies attempts to model it from the bottom up, whether on the basis of an intrinsically differentiated space-time manifold or out of a multitude of individual building blocks.

1 illus, 45 ref

008814   Mishra V;Sr1Vastava V D;Kataria S K (Electron Div, Bhabha Atom Res Cent, Trombay, Mumbai-400 085, Email: eld@magnum.barc.ernet.in) : Role of guard rings in improving the performance of silicon detectors. Pramana J Phys 2005, 65(2), 259-72.

BARC has developed large-area silicon detectors in collaboration with BEL to be used in the pre-shower detector of the CMS experiment at CERN. The use of floating guard rings (FGR) in improving breakdown voltage and reducing leakage current of silicon detectors is well-known. It has been demonstrated that FGRs can also be used to improve the spectroscopic response of silicon detectors. The results have been confirmed by carrying out α-particle (≈ MeV) and γ-ray (60 keV) spectroscopies with the FGR floating or biased and the underlying physics aspect behind the change in spectra is explained. Although reduction in leakage current after biasing one of the guard rings has been reported earlier, the role of a guard ring in improving the spectroscopic response is reported for the first time. Results of TCAD simulations for silicon detectors with the guard ring under different biasing conditions have been presented. Low yield in producing large-area silicon detectors makes them very costly. However, with one of the FGRs biased even a detector having large surface leakage current can be used to give the same response as a very good detector. This makes the use of large-area silicon detectors very economical as the yield would be very high (<62> 90%).

10 illus, 1 table, 19 ref

008813   Mishra R K;Mishra R A (Computer and I.T. Sect, Trop For Res Inst, Jabalpur-482 001, Email: rkm_30@yahoo.com) : Unusually low-amplitude anisotropic wave-train events of cosmic ray intensity during 1981-1994. Pramana J Phys 2005, 64(2), 197-206.

Investigation has been made for unusually low-amplitude anisotropic wave train events (LAE) for cosmic ray intensity data of Deep River neutron monitoring station during the period 1981-94. It has been observed that the phase of diurnal anisotropy remains in the same co-rotational direction for most of the LAEs while the phase shifts to early hours for some of the LAEs in diurnal anisotropy. During minimum solar activity, LAEs have been observed to be dominant. Solar wind plasma (SWP) parameters, interplanetary magnetic field and various features at solar disk have also been studied. The amplitude remains low continuously for most of the days while the phase shifts to earlier hours. Occurrence of LAE is independent of the nature of interplanetary magnetic field (IMF).

6 illus, 36 ref

008812   Mishra M;Konar S (Dep of Appl Phys, Birla Inst of Technol, Mesra, Ranchi-835 215, Email: skonar@bitmesra.ac.in) : Induced focusing and conversion of a Gaussian beam into an elliptic Gaussian beam. Pramana J Phys 2005, 65(3), 425-36.

Presents an investigation of the induced focusing in Kerr media of two laser beams, the pump beam and the probe beam, which could be either Gaussian or elliptic Gaussian or a combination of the two. Used variational formalism to derive relevant beam-width equations. Among several important findings, the finding that a very week probe beam can be guided and focused when power of both beams are well below their individual threshold for self-focusing, is a noteworthy one. It has been found that induced focusing is not possible for laser beams of any wavelength, and beam radius. In case both beams are elliptic Gaussian, It is shown that when power of both beams is above a certain threshold value then the effective radius of both beams collapses and collapse distance depends on power. Moreover, it has been found that induced focusing can be employed to convert a circular Gaussian beam into an elliptic Gaussian beam.

5 illus, 28 ref

008811   Medhat M E;Abdel-Hafiez A A;Awaad Z;Ali M A (Expl Nuclear Phys Dep, Nuclear Res Cent, Cairo, Egypt, Email: medhatme@yahoo.com) : A package for gamma-ray spectrum analysis and routine neutron actination analysis. Pramana J Phys 2005, 65(2), 245-58.

A package for gamma spectrum analysis (PGSA) was developed using object-oriented Borland C++ design for MS-windows. This package consists of five programs which can be used for gamma-ray spectrum analysis and routine neutron activation analysis. The advantages of PGSA are its simple algorithms and its need for only minimum amount of input information.

13 illus, 1 table, 6 ref

008810   Mathur S;Ahuja B L (Dep of Phys, Coll of Sci Campus M.L. Sukhadia Univ, Udaipur-313 001, Email: blahuja@yahoo.com) : On the bremsstrahlung background correction to the high-energy Compton spectroscopy. Pramana J Phys 2005, 65(1), 159-64.

Methodology for bremsstrahlung (BS) background correction to extract a true Compton profile in high-energy Compton scattering experiments is presented. The BS background profiles for Hg, computed within the Born approximation, estimated for different values of incident energy. It is seen for the first time that the BS background contribution in high-energy Compton profile experiments like those employing third generation synchrotron radiation sources comes out to be significant and non-linear. Further, it is found that the incorporation of BS correction in data reduction of such an experiment performed on Hg at 662 keV energy helps in reconciliation of theory and experiment.

1 illus, 1 table, 15 ref

008809   Man Mohan;Singh A K;Jha A K;Singh N (Dep of Phys and Astrophys, Univ of Delhi, Delhi-110 O70, Email: aloksinghjha@yahoo.co.in) : Fine structure energy levels, oscillator strengths and lifetimes of chlorine-like chromium. Pramana J Phys 2005, 65(1), 75-84.

Relativistic calculations for the evaluation of energy levels, oscillator strengths, transition probabilities and lifetimes for Cr VIII ion. Use has been made of configuration interaction technique by including Briet-Pauli approximation. The energies of various levels from the ground state to excited levels of 3s3p⁶, 3s²3p⁴3d, 3s²3p⁴4s, 3s²3p⁴4d of Cr VIII are given in LSJ coupling scheme after fine-tuning and are compared with the experimental results compiled in the NIST Data Base. Many new lines have been predicted which have not appeared so far in the NIST Data.

6 tables, 13 ref

008808   Malathi M;Sabesan R;Krishnan S (Dep of Phys, Vellore Inst of Technol, Vellore-632 014, Email: malathi_murugesan@yahoo.co.in) : Studies of linear correlation factor of dielectric polarization and excess dipolar free energies of amides in apolar solvents. Pramana J Phys 2005, 65(3), 529-34.

The Kirkwood-Frohlich correlation factor (g), Eyring's parameters G and G* and the dipolar excess free energies of dilute solutions of formamide, acetamide, N-methyl acetamide, N,N-dimethyl formamide and N, N-dimethyl acetamide in 1,4-dioxan/benzene were obtained from a measurement of their static dielectric permittivities at 308 K. The fluid structure of these amides is discussed. Both in formamide and acetamide a dimeric linear chain with the individual dipoles more or less parallely oriented is preferred. In N-methyl acetamide, the antiparallel orientation of dipoles at lower concentrations turns into a parallel orientation with increase of concentration. In tertiary amides, with increase of concentration, parallel orientation of dipoles with global value of g tending to unity is observed. The dipolar excess free energy of mixing in a given solvent is of the order primary amide <62> secondary amide <62> tertiary amide.

1 table, 23 ref

008807   Mak M K;Harko T (Dep of Phys, The Univ of Hong Kong, Pokfulam Road, Hong Kong SAR, P.R. China, Email: mkmak@vtc.edu.hk) : Relativistic compact objects in isotropic coordinates. Pramana J Phys 2005, 65(2), 185-92.

Presents a matrix method for obtaining new classes of exact solutions for Einstein's equations representing static perfect fluid spheres. By means of a matrix transformation, reduc Einstein's equations to two independent Riccati-type differential equations for which three classes of solutions are obtained. One class of the solutions corresponding to the linear barotropic-type fluid with an equation of state p = γρ is discussed in detail.

19 ref

008806   Lagzi I (Dep of Phys Chem, Eotvos Univ, P.O. Box 32, Pazmany Peter setany 1. A, Budapest, H-1518, Hungary, Email: lagzi@vuk.chem.elte.hu) : Liesegang patterns Complex formation or precipitate in an electric field. Pramana J Phys 2005, 64(2), 291-8.

Formation of 1D Liesegang patterns was studied numerically in precipitation and reversible complex formation of precipitate scenarios in an electric field. The Ostwald's supersaturation model reported by Buki, Karpati-Smidroczki and Zrinyi (BKZ model) was extended further. In the presence of an electric field the position of the first and the last bands (X_{n) measured from the junction point of the outer and the inner electrolytes can be described by the function Xn = a1τn^1/2 + a2τn + a3, where τn is the time elapsed until the nth band formation, a1, a2; and a3 are constants. The variation of the total number of bands with different electric field strengths (ε) has a maximum. For higher ε one can observe a moving precipitation zone that becomes wider due to precipitation and reversible complex formation.}

6 illus, 30 ref

008805   Kundu A;Chakrabarti B;Das T K (Dep of Phys, Univ of Calcutta, 92 A.RC. Road, Kolkata-700 009, Email: anasuya09@yahoo.co.uk) : Application of potential harmonic expansion method to BEC: Thermodynamic properties of trapped <. Pramana J Phys 2005, 65(1), 61-74.

Adopts the potential harmonics expansion method for an ab initio solution of the many-body system in a Bose condensate containing interacting bosons. Unlike commonly adopted mean-field theories, the method is capable of handling two-body correlation properly. It disregard three- and higher-body correlations. This simplification is ideally suited to dilute Bose Einstein condensates, whose number density is required to be so small that the interparticle separation is much larger than the range of two-body interaction to avoid three- and higher-body collisions, leading to the formation of molecules and consequent instability of the condensate. In the method are can incorporate realistic finite range interactions. Calculates energies of low-lying states of a condensate containing ²³Na atoms and some thermodynamical properties of the condensate.

8 illus, 1 table, 19 ref

008804   Kocis L (Peranga Court Unit 4, 43 Fifth Ave., Sandgate, QLD 4017, Australia, Email: l_kocis@hotmail.com) : Semi-classical limit of relativistic quantum mechanics. Pramana J Phys 2005, 65(1), 147-52.

It is shown that the semi-classical limit of solutions to the Klein-Gordon equation gives the particle probability density that is in direct proportion to the inverse of the particle velocity. It is also shown that in the case of the Dirac equation a different result is obtained.

2 ref

008803   Jain A P;Parashar J (Dep of Appl Phys, Samrat Ashok Technological Inst, Vidisha-464 001, Email: jparashar@indiya.com) : Excitation of surface plasma waves over corrugated slow-wave structure. Pramana J Phys 2005, 65(2), 311-21.

Microwave propagating along vacuum-dielectric-plasma interface excites surface plasma wave (SPW). A periodic slow-wave structure placed over dielectric slows down the SPW. The phase velocity of slow SPW is sensitive to height, periodicity, number of periods, thickness and the separation between dielectric and slow-wave structure. These slow SPW can couple the microwave energy to the plasma and can sustain the discharge. The efficiency of the power coupling is few per cent and is sensitive to separation between dielectric and slow-wave structure.

4 illus, 16 ref

008802   Gupta S K;Hayashi Y;Jain A;Karthikeyan S; Kawakami S;Ravindran K C;Tonwar S C (Tata Inst of Fundamental Res, Homi Bhabha Rd, Mumbai-400 005, Email: gupta@grapes.tifr.res.in) : A high-performance, low-cost, leading edge discriminator. Pramana J Phys 2005, 65(2), 273-83.

High-performance, low-cost, leading edge discriminator has been designed with a timing performance comparable to state-of-the-art, commercially available discriminators. A timing error of 16 ps is achieved under ideal operating conditions. Under more realistic operating conditions the discriminator displays a timing error of 90 ps. It has an intrinsic double pulse resolution of 4 ns which is better than most commercial discriminators. A low-cost discriminator is an essential requirement of the GRAPES-3 experiment where a large number of discriminator channels are used.

9 illus, 9 ref

008801   Ferencz O E (Space Res Grp, Eotvos Univ, Geophysical Department, H-1518, Budapest, P.O. Box 32, Hungary, Email: spacerg@sas.elte.hu) : Full-wave solution of short impulses in inhomogeneous plasma. Pramana J Phys 2005, 64(2), 249-68.

The problem of real impulse propagation in arbitrarily inhomo-geneous media will be presented on a fundamentally new, general, theoretical way. The general problem of wave propagation of monochromatic signals in inhomogeneous media was enlightened in [1]. The earlier theoretical models for spatial inhomogeneities have some errors regarding the structure of the resultant signal originated from backward and forward propagating parts. The application of the method of inhomogeneous basic modes (MIBM) and the complete full-wave solution of arbitrarily shaped non-monochromatic plane waves in plasmas made it possible to obtain a better description of the problem, on a fully analytical way, directly from Maxwell's equations. The model investigated is inhomogeneous of arbitrary order (while the wave pattern can exist), anisotropic (magnetized), linear, cold plasma, in which the gradient of the one-dimensional spatial inhomogeneity is parallel to the direction of propagation.

4 illus, 9 ref