ISA

Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surfaces at room temperature

Das A K;Dev B N;Sundaravel B;Zluo E;Xu J B

Total energy calculation of perovskite, BaTiO3, by self-consistent tight binding method
Cong B T;Huy P N A;Schelling P K;Halley J W

000090 Cong B T;Huy P N A;Schelling P K;Halley J W (Faculty of Physics, Hanoi University of Science, 334 Nguyen Trai Street, Hanoi, Vietnam) : Total energy calculation of perovskite, BaTiO3, by self-consistent tight binding method. Bull Mater Sci 2003, 26(1), 155-8.

Results of numerical computation on some characteristics of BaTiO3 such as total energy, constant, density of states, band structure etc using self-consistent tight binding method have been presented. Besides strong Ti-O bond between 3d on titanium and 2p orbital on oxygen states, weak hybridization between the Ba 6s and O 2p states have been included. The results are compared with those of other more sophisticated methods.

6 illus, 2 tables, 14 ref

Simple explanation for the reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite
Cong B T;Huy P N A;Long N H;Long D D

000089   Cong B T;Huy P N A;Long N H;Long D D (Faculty of Physics, Hanoi University of Science, 334 Nguyen Trai Street, Hanoi, Vietnam) : Simple explanation for the reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite. Bull Mater Sci 2003, 26(1), 151-4.

The reentrant magnetic phase transition in Pr0.5Sr0.41Ca0.09MnO3 perovskite is explained using the Ising spin model on the square lattice with mixed ferromagnetic and antiferromagnetic exchange interactions. It is shown using numerical calculations that this effect is strongly affected by the external magnetic field and lattice disorder.

4 illus, 7 ref

Quantum contact interactions
Cheon T

000088   Cheon T (Laboratory of Physics, Kochi University of Technology, Tosa Yamada, Kochi-780 8502, Japan) : Quantum contact interactions. Pramana J Phys 2002, 59(2), 311-19.

The existence of several exotic phenomena, such as duality and spectral anholonomy is pointed out in one-dimensional quantum wire with a single defect. The topological structure in the spectral space which is behind these phenomena is identified.

2 illus, 14 ref

Mutually unbiased bases
Chaturvedi S

000087   Chaturvedi S (School of Physics, University of Hyderabad, Hyderabad-500 046) : Mutually unbiased bases. Pramana J Phys 2002, 59(2), 345-50.

After a brief review of the notion of a full set of mutually unbised bases in an N-dimensional Hilbert space. Summaries the work of Wootters and Fields (W K Wootters and B C Fields, Ann. Phys. 191, 363 (1989)) which gives an explicit construction for such bases for the case N=p<^>r, where p is a prime. Further, shows how, by exploiting certain freedom in the Wootters-Fields construction, the task of explicitly writing down such bases can be simplified for the case when p is an odd prime. In particular, the results entirely in terms of the character vectors of the cyclic group G of order p. Also analyses the connection between mutually unbiased bases and the representations of G.

8 ref

Application of genetic algorithms to hydrogenated silicon clusters
Chakraborti N;Prasad R

000086   Chakraborti N;Prasad R (Physics Dep, Indian Institute of Technology, Kanpur-208 016) : Application of genetic algorithms to hydrogenated silicon clusters. Bull Mater Sci 2003, 26(1), 127-30.

Application of biologically inspired genetic algorithms has been discussed to determine the ground state structure of a number of Si-H clusters. The total energy of a given configuration of a cluster has been obtained by using a non-orthogonal tight-binding model and the energy minimization has been carried out by using genetic algorithms and their recent variant differential evolution. Results for ground state structures and cohesive energies for Si-H clusters are in good agreement with the earlier work conducted using the simulated annealing technique. The results obtained by genetic algorithms turn out to be comparable and often better than the results obtained by the simulated annealing technique.

1 illus, 17 ref

Thermally stimulated discharge current (TSDC) and dielectric constant of semiconducting glasses
Burghate D K;Deogaonkar V S;Sawarkar S B; Yawale S P;Pakade S V

000085   Burghate D K;Deogaonkar V S;Sawarkar S B; Yawale S P;Pakade S V (Physics Dep, Polytechnic Badnera, Amravati-444 701) : Thermally stimulated discharge current (TSDC) and dielectric constant of semiconducting glasses. Bull Mater Sci 2003, 26(2), 267-71.

Results of thermally stimulated discharge current (TSDC) and dielectric constant for 40PbO-60Bi2O3 glass thermoelectrets are presented. Measurements of TSDC and dielectric constant, ε`, have been carried out in the temperature range 30-300°C. The thermoelectrets were prepared at different polarizing fields. The various observed peaks in the thermograms are discussed on the basis of space charge polarization. The trap energy is evaluated from the Garlick-Gibson plot of initial rise method. Similarly other parameters such as relaxation time, charge release etc are evaluated.

4 illus, 1 table, 27 ref

Structures of Mn clusters
Briere T M;Sluiter M H F;Kawazoe Y

000084   Briere T M;Sluiter M H F;Kawazoe Y (NO, Institute for Materials Research, Thoku University, Aoba-ku, Sendai 980-8577, Japan) : Structures of Mn clusters. Bull Mater Sci 2003, 26(1), 115-6.

The geometries of several Mn clusters in the size range Mn<>13-Mn23 are studied via the generalized gradient approximation to density functional theory. For the 13- and 19-atom clusters, the icosahedral structures are found to be most stable, while for the 15-atom cluster, the bcc structure is more favoured. The clusters show ferrimagnetic spin configurations.

2 illus, 7 ref

Generic entangling through quantum indistinguishability
Bose S;Home D

000083   Bose S;Home D (Centre for Quantum Computation, Clarendom Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, England) : Generic entangling through quantum indistinguishability. Pramana J Phys 2002, 59(2), 229-34.

Presents a general scheme for entangling any degree of freedom of two uncorrelated identical particles from independent sources by a combination of two-particle interferometry and which-way detection. Shows that this entanglement generation procedure works for completely random initial states of the variable to be entangled. Also demonstrates a curious complementarity exhibited by scheme and its applications in estimating the generated entanglement as a function of wave packet overlap at the beamsplitter.

2 illus, 16 ref

Projector augmented wave method: ab initio molecular dynamics with full wave functions
Blochl P E;Forst C J;Schimpl J

000082   Blochl P E;Forst C J;Schimpl J (Clausthal University of Technology, Institute for Theoretical Physics, Leibnizstr. 10, D-38678 Clausthal-Zellerfeld, Germany) : Projector augmented wave method: ab initio molecular dynamics with full wave functions. Bull Mater Sci 2003, 26(1), 33-41.

A brief introduction to the projector augmented wave method is given and recent developments are reviewed. The projector augmented wave method is an all-electron method for efficient ab initio molecular dynamics simulations with full wave functions. It extends and combines the traditions of existing augmented wave methods and the pseudopotential approach. Without sacrificing efficiency, the PAW method avoids transferability problems of the pseudopotential approach and it has been valuable to predict properties that depend on the full wave functions.

2 illus, 37 ref

Effect of alloying on the electronic structure and magnetic properties of Fe, Co and Ni with Au and Ag
Bhattacharjee A;Ahmed M;Mookerjee A;Halder A

000080   Bhattacharjee A;Ahmed M;Mookerjee A;Halder A (Physics Dep, University of Dhaka, Dhaka 100, Bangladesh) : Effect of alloying on the electronic structure and magnetic properties of Fe, Co and Ni with Au and Ag. Bull Mater Sci 2003, 26(1), 199-205.

Self-consistent, augmented space recursion technique has been used to study the electronic structure and magnetic properties of alloys of the transition metals, Fe, Co and Ni with the noble metals, Ag and Au. Effect of local environment and the hybridization between the constituent bands on the electronic and magnetic properties.

9 illus, 1 table, 13 ref

Highly efficient deep ultraviolet generation by sum-frequency mixing in a BBO crystal pair
Bhar G C;Kumbhakar P;Chatterjee U;Chaudhary A K;Kokh A

000079   Bhar G C;Kumbhakar P;Chatterjee U;Chaudhary A K;Kokh A (Laser Lab., Phys Dep, Burdwan University, Burdwan-713 104) : Highly efficient deep ultraviolet generation by sum-frequency mixing in a BBO crystal pair. Pramana J Phys 2002, 59(1), 69-74.

Generation of deep ultraviolet radiation at 210 nm by Type-I third harmonic generation is achieved in a pair of BBO crystals with conversion efficiency as high as 36%. the fundamental source is the dye laser radiation pumped by the second harmonic of a Q-switched Nd: YAG laser. A walk-off compensated configuration with the BBO crystal pair has enabled us to realize such a high conversion efficiency in the interaction.

3 illus, 1 tables, 11 ref

Bianchi type I inflationary universe in general relativity
Bali R;Jain V C

000078   Bali R;Jain V C (Math Dep, Univ of Rajasthan, Jaipur-302 004) : Bianchi type I inflationary universe in general relativity. Pramana J Phys 2002, 59(1), 1-7.

Investigated Bianchi type I inflationary universe in the presence of massless scalar field with a flat potential. To get an inflationary solution. Considered a flat region in which potential V is constant. The inflationary scenario of the model is discussed in detail.

10 ref

Control of a coupled map lattice model for vortex shedding in the wake of a cylinder
Balasubramanian G;Olinger D J;Demetriou M A

000077   Balasubramanian G;Olinger D J;Demetriou M A (Mechanical Engineering Dep, Worcester Polytechnic Institute, Worcester, MA 01609-2280, USA) : Control of a coupled map lattice model for vortex shedding in the wake of a cylinder. Pramana J Phys 2002, 59(1), 91-111.

Studies the addition of control terms into the highly efficient CML models and explored the resulting dynamics. Proportional, adaptive proportional and discontinuous non-linear (DNL) control methods were used to derive the control laws. The first method employed occasional proportional feedback. The adaptive method used spatio-temporal feedback control. The DNL method used a discontinuous feedback linearing Zation procedure, and the controller was designed for the resulting linearized system using eigenvalue assignment. These techniques were applied to a modeled vortex dislocation structure in the wake of a vibrating cable in uniform freestream flow. Parallel shedding patterns were achieved for a range of forcing frequency-forcing amplitude combinations studied to validate the control theory. The adaptive proportional and DNL methods were found to be more effective than the proportional control method due to the incorportation of a spatially varying feedback gain across the cylinder span. The DNL method was found to be the most efficient controller of the low-order CML model. The required control level across the cable span was correlated to the 1/1 lock-on behavior of the temporal cricle map.

1 illus, 31 ref

Ground state structures and properties of Si3Hn(n=1-6) clusters
Balamurugan D;Prasad R

000076   Balamurugan D;Prasad R (Physics Dep, Indian Institute of Technology, Kanpur-208 016) : Ground state structures and properties of Si3Hn(n=1-6) clusters. Bull Mater Sci 2003, 26(1), 123-5.

The ground state structures and properties of Si3Hn (1≤n <131<>F255>6) clusters have been calculated using Car-Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. Cohesive energy per particle and first excited electronic level gap of the clusters have been studied as a function of hydrogenation. Hydrogenation is done till all dangling bonds of silicon are saturated. The results show that over coordination of hydrogen is favoured in Si3Hn clusters and the geometry of Si3 cluster does not change due to hydrogenation. Cohesive energy per particle and first excited electronic level gap study of the clusters show that Si3H6 cluster is most stable and Si3H3 cluster is most unstable among the clusters considered.

3 illus, 17 ref

Quantum space times in the year 2002
Balachandran A P

000075   Balachandran A P (Physics Dep, Syracuse University, Syracuse, New York 13244-1130, USA) : Quantum space times in the year 2002. Pramana J Phys 2002, 59(2), 359-68.

Reviews certain emergent notions on the nature of space-time from noncommutative geometry and their radical implications. These ideas of space-time are suggested from developments in fuzzy physics, straing theory, and deformation quantization. The review focuses on the ideas coming from fuzzy physics. finds models of quantum space-time like fuzzy S<^>4 on which states cannot be localized, but which fluctuate into other manifolds like CP<^>3. New uncertainty principles concerning such lack of localizability on quantum space-times are formulated. Such investigations show the possibility of formulating and answering questions like the probability of finding a point of a quantum manifold in a state localized on another one. additional striking possibilities indicated by these developments is the (generic) failure of CPT theorem and the conventional spin-statistics connection. They even suggest that Plancks constant may not be a constant, but an operator which does not commute with all observables. All these novel possibilities arise within the rules of conventional quantum physics, and with no serious input from gravity physics.

12 ref

International activites on standards and standardization for the evaluation of material properties to support free trade.
Bahng G W

000074   Bahng G W (NO, Korea Reasearch Institute of Standards and Science, PO Box 102, Yusoung Daejeon-305-600) : International activites on standards and standardization for the evaluation of material properties to support free trade.. MAPAN 2003, 18(Jan-Mar), 283-9.

With the emergence of the WTO system, the alignment of standards in testing, calibration and accreditation has become one of the critical problems to achieve the goal of free trading system. Particularly,the importance of confirmity assessment in trade was already noted in 1994 agreement on Technical Barriers on Trade. In 1999, 38 National Metrology Institutes signed a Mutual Recognition Arrangement at BIPM. In order to secure the equivalence in calibration among the NMIs who signed on the MRA, BIPM launched a program known as 'Key Comparision'. In 2001, laboratory accreditation bodies of ILAC signed MRA to promote the acceptance of test and calibration data. The aim of the ILAC MRA ia to develop a global network of accredited testing and calibration laboratories to realize the free trade. Having recognized the vital importance of materials measurement and testing technology in trade, the G7 countries already initiated in 1987 a multilateral program known as the Versailles Project on Advanced Materials and Standards(VAMAS) and they have been cooperating eacg other for the last 15 years. Now it became a worldwide concern with the increase of trade in material products and it is no more a problem that could be dealt by the G7 countries only. Recently, APMP approved to set-up ad-hoc working group in materials properties evaluation to promote development of standards in materials testing and standardization through international cooperation. In this paper the detailed international cooperation is discussed.

1 table

Developments in quantum information processing by nuclear magnetic resonance: Use of quadrupolar an dipolar couplings
Anil Kumar;Ramanathan K V;Mahesh T S;Sinha N; Murali K V R

000073   Anil Kumar;Ramanathan K V;Mahesh T S;Sinha N; Murali K V R (Department of Physics, Sophisticated Instruments Facility, Indian Institute of Science, Bangalore-560 012) : Developments in quantum information processing by nuclear magnetic resonance: Use of quadrupolar an dipolar couplings. Pramana J Phys 2002, 59(2), 243-54.

Use of dipolar and quadrupolar couplings for quantum information processing (QIP) by nuclear magnetic resonance (NMR) is described. In these cases, instead of the individual spins being qubits, the 2<^>n energy levels of the spin-system can be treated an an n-qubit system. It is demonstrated that QIP in such systems can be carried out using transition-selective pulses, in CH,v>3CN, <^>13CH3CN, <^>7Li(I=3/2) and <^>133Cs (I=7/2), oriented in liquid crystals yielding 2 and 3 qubit systems. Creation of pseudopure states, implementation of logic gates and arithmetic operations (half-adder and subtractor) have been carried out in these systems using ransition-selective pulses.

4 illus, 3 tables, 51 ref

Third-generation muffin-tin orbitals
Andersen O K;Saha-Dasgupta T;Ezhov S

000072   Andersen O K;Saha-Dasgupta T;Ezhov S (NO, Max-Planck Institut fur Festkorperforschung, D-70569, Stuttgart, Germany) : Third-generation muffin-tin orbitals. Bull Mater Sci 2003, 26(1), 19-26.

By the example of sp<^>3-bonded semiconductors, 3rd-generation muffin-tin orbitals (MTOs) are illustrated. It is demonstrated that they can be downfolded to smaller and smaller basis sets: sp<^>3d<^>10, sp<^>3, and bond orbitals. For isolated bands, it is possible to generate Wannier functions a priori. Also for bands, which overlap other bands, Wannier-like MTOs can be generated a priori. Hence, MTOs have a unique capability for providing chemical understanding.

8 illus, 20 ref

Ion transport in Au<
Anand Kumar R;Chandramani R

000071   Anand Kumar R;Chandramani R (Physics Dep, Bangalore University, Bangalore-560 056) : Ion transport in Au<. Bull Mater Sci 2003, 26(2), 255-9.

Undoped KDP and KDP crystals containing KI/NaI with/without gold doping were grown by slow evaporation technique. All the grown crystals were γ-irradiated using <^>60Co source. Electrical conductivity measurements were carried out on all these crystals perpendicular to the unique direction before and after γ-irradiation. Results show that the conductivity of KDP crystals increases with the addition of KI/NaI and with gold doping as well as upon rise in temperature. Computed values of activation energies from the conductivity measurements are given. For all the grown crystals, dielectric constant measured as a function of frequency.

9 illus, 2 tables, 11 ref

Fractal patterns on the onset of coherent structures in a coupled map lattice
Ambika G;Menon K

000070   Ambika G;Menon K (Phys Dep, Maharaja's College, Cochin-682 011) : Fractal patterns on the onset of coherent structures in a coupled map lattice. Pramana J Phys 2002, 59(1), 155-61.

Reports the formation of Cantor set-like fractals during the develpment of coherent structures in a coupled map lattic (CML). The dependence of these structures on the size of the lattice as well as the first three dimensions of the associated fractal patterns are analyzed numerically.

5 illus, 29 ref

Critical exponents in the transition of chaos in one-dimensional discrete systems
Ambika G;Sujatha N V

000069   Ambika G;Sujatha N V (Phys Dep, Maharaja's College, Cochin-682 011) : Critical exponents in the transition of chaos in one-dimensional discrete systems. Pramana J Phys 2002, 59(1), 9-18.

Repors the numerically evaluated critical exponents associated with the scaling of generalized fractal dimensions during the transition from order to chaos. the analysis is carried out in detail in the context of unimodal and bimodal maps representing typical one-dimensional diserete dynamical systems. The behavior of Lyapunov exponents (LE) in the cross over region is also studied for a complete characterization.

6 illus, 2 tables, 21 ref

Generalized Reynolds equation for non-Newtonian ferrofluids
Verma D K;Rathish Kumar B V;Sinha P

000057   Verma D K;Rathish Kumar B V;Sinha P (Department of Mathematics, Narmada College of Science and Commerce, Zadeshwar, Bharuch-392 011) : Generalized Reynolds equation for non-Newtonian ferrofluids. Indian J Engng Mater Sci 2003, 10(1), 41-9.

A generalized form of Reynolds equation is derived for viscoelastic ferrofluid lubrication in the presence of a constant magnetic field applied transversely to the flow. As a particular case, one-dimensional form of it is used to study the characteristics of a squeeze film. It is observed that the effect of viscoelastic parameter is to reduce the load capacity of the bearing even in the case of magnetic fluid.

5 illus, 19 ref

Strokes flow past a fluid prolate spheroid
Satya Deo;Datta S

000053   Satya Deo;Datta S (Department of Mathematics, University of Allahabad, Allahabad, U.P.-211 002) : Strokes flow past a fluid prolate spheroid. Indian J pure appl Math 2003, 34(5), 755-64.

The Strokes flow problem of a viscous incompressible fluid past a fluid prolate spheroid parallel to its axis of revolution is investigated. Explicit expressions are obtained fro both the external and internal flow fields. The drag force experienced by the fluid prolate spheroid is evaluated. Special well-known cases and some new results are then deduced.

5 ref

Eigen value approach to second dynamic problem of micropolar elastic solid
Rajneesh Kumar;Ranjit Singh;Chadha T K

000050   Rajneesh Kumar;Ranjit Singh;Chadha T K (Department of Mathematics, K. U., Kurukshetra-136 119) : Eigen value approach to second dynamic problem of micropolar elastic solid. Indian J pure appl Math 2003, 34(5), 743-54.

The dynamic problem of micropolar elastic solid has been investigated by employing eigen value approach after applying Laplace and the Fourier transformations. An example of infinite space was concentrated force at the origin has been presented to illustrate the application of the approach. The integral transforms have been inverted by using a numerical technique to obtain the components of microrotation, displacement, force stress and couple stresses in the physical domain. Numerical results for these quantities are given and illustrated graphically.

6 illus, 13 ref

Change in entropy of Universe
Yadav R P;Gangwar P K

011757   Yadav R P;Gangwar P K (Department of Physics, Govt. P.G. College, Bilaspur (Pilibhit)-262 201) : Change in entropy of Universe. Acta Cienc Indica-Phys 2002, 28(3), 121-8.

Chester-Chisnell-Whitham method has been used to study the propagation of spherical converging weak shock wave in non-uniform medium. Assuming an initial density distribution law as ρ₀ = ρ`r^-w, where, ρ` is the density at the axis of symmetry/centre and w is a constant, analytical relation for shock velocity has been derived. The expressions for change in entropy of the medium immediately behind the shock have also been obtained. Finally, the results accomplished here have also been compared with earlier results as well as with those for strong shock. It is found that change in entropy increases as shock propagates in the medium. This agrees with the universal law of increase of entropy.

13 illus, 15 ref

Weak hydromagnetic cylindrical shock waves in a rotating gas
Yadav M

011756   Yadav M (Department of Physics, Govt. P.G. College, Kotdwara-246 149, Pauri) : Weak hydromagnetic cylindrical shock waves in a rotating gas. Acta Cienc Indica-Phys 2002, 28(3), 155-60.

The propagation of weak diverging cylindrical shock waves through an ideal and rotating gas in presence of a magnetic field having all the three components of the form, H²_r₀ = ηrH²_z₀ (η is a constant), H²θ₀ = rH²_z₀ and H_z₀ as constant, taking an initial density distribution of the form ρ₀ = ρ`r^w. Expressions for flow variables have been derived and their numerical estimates have been computed at permissible shock front locations.

2 illus, 1 tables, 18 ref

Evaluation of radiation in the environment of Sulaimaniyah (Iraq) in the pre-war period
Upadhyay P N;Prasad A

011755   Upadhyay P N;Prasad A (Department of Physics, Nalanda Mahila College, Biharsharif-803 101) : Evaluation of radiation in the environment of Sulaimaniyah (Iraq) in the pre-war period. Acta Cienc Indica-Phys 2002, 28(3), 161.

Presents some results on the evaluation of radiation in Sulaimaniyah (Iraq). The finding relies on the basis of detection of high energy charged particles produced by cosmic rays and other sources of radiation, if any. In the pre-war period of Iraq and Iran, no such radiation was found which could pollute the environment there.

illus, tables, ref

Behaviour of dσ/dΩ ~ Pπ for backward elastic scattering π<
Upadhyay P N

011754   Upadhyay P N (Department of Physics, Nalanda Mahila College, Biharsharif-803 101) : Behaviour of dσ/dΩ ~ Pπ for backward elastic scattering π<. Acta Cienc Indica-Phys 2002, 28(4), 177-8.

Presents an account of the results of the data analysis of the backward π^-p -<62> π^-p elastic scattering. A narrow range of incident pion beam momentum between 599MeV/c to 670 MeV/c has been selected to investigate the dσ/dΩ~ Pπ plot. There is possibilty of a peak at Pπ = 630MeV/c.

1 illus, 1 table, 2 ref

Analysis of the π<
Upadhyay P N

011753   Upadhyay P N (Department of Physics, Nalanda Mahila College, Biharsharif-803 101) : Analysis of the π<. Acta Cienc Indica-Phys 2002, 28(4), 975-6.

Present an account of results obtained by analysing π^- backward elastic scattering in the range of Pπ656 to 703.3 MeV/c. An enhancement at Pπ682MeV/c was found. The result is in agreement with those of others.

1 illus, 5 ref

The a₂<
Upadhyay P N

011752   Upadhyay P N (Department of Physics, Nalanda Mahila College, Biharsharif-803 101) : The a₂<. Acta Cienc Indica-Phys 2002, 28(4), 214-19.

Presents some results on the a₂^- (1320) meson produced in the π^-p→a₂^-p interaction near its production threshold. The a₂ enhancements have been observed for its 3π and 1π^- = neutral decay modes. The last channel signifies a₂ → ηπ^- with η→ all neutrals. No split in the a₂ (1320) mass has been observed.

4 illus, 4 ref

Study of the π<
Upadhyay P N

011751   Upadhyay P N (Department of Physics, Nalanda Mahila College, Biharsharif-803 101) : Study of the π<. Acta Cienc Indica-Phys 2002, 28(4), 181-2.

Presents an account of the results obtained by analysing the π^-p data for elastic scattering in the range off pion beam momentum, Pπ of 1339 MeV/c to 1635 MeV/c. No dip or peak has been found in the yield curve over 0.38 ≤ <157>t<157> ≤ 0.79(GeV/c)². It is attributed to a smooth change in the number events with a variation in Pπ in this range.

7 ref

Some results on the differential cross-section of the backward π<
Upadhyay P N

011750   Upadhyay P N (Department of Physics, Nalanda Mahila College, Biharsharif-803 101) : Some results on the differential cross-section of the backward π<. Acta Cienc Indica-Phys 2002, 28(4), 179-80.

Presented an account of some results on the variation of differential cross-section with a change in incident pion beam momentum Pπ between 599 MeV/c to 710 MeV/c. The data cannot be explained by straight line behaviour with high confidence level.

1 illus, 1 table, 4 ref

Temperature variations of vanderwaal's constants
Thakur M L;

011749   Thakur M L; (P.G. Department of Physics, T.M. Bhagalpur-812 007, ) : Temperature variations of vanderwaal's constants. Acta Cienc Indica-Phys 2002, 28(4), 221-9.

Temperature variations of the both vanderwaal's constants are found to be same and they decrease with temperature. L-J (m,n) potential model is not found to be applicable in the calculation of vanderwaal's constant 'a'. The theoritical and experimental results in respect of temperature variation of 'a' confirm the validity of vanderwaal's potential model. The potential energy suitable for 'a' is constant and attractive in nature.

1 illus, 13 tables, 16 ref

Ionization chamber wall correction factors in measuring air kerma for gamma rays
Takata N;Kurosawa T;Koyama Y

011748   Takata N;Kurosawa T;Koyama Y (Ionizing Radiation Section, NMIJ/AIST, Tsukuba-305-8568, Japan) : Ionization chamber wall correction factors in measuring air kerma for gamma rays. MAPAN 2003, 18(Jan-Mar), 223-8.

Attenuation and gamma rays scattered in ionization chamber wall must be corrected for in absolute air kerma measurement. The correction factor is determined by measuring the variation in chamber response as a function of wall thickness in the full build-up region, extrapolating linearly to infer the response at zero wall thickness, and applying the correction factor to account for the center of electron production. Bielajew calculated the correction factor using the Monte carlo method and found that chamber response should not be extrapolated linearly with wall thickness. Non-linear extrapolation is due to the non linear scalling of effective wall thickness. AIST uses 2 graphite cylinderical ionization chambers of different sizes to measure air kerma in ⁶⁰Co and ¹³⁷Cs gamma ray fields. These chambers are placed at a 45-degree angle to gamma ray beams so gamma ray attenuation does not increase at end or side walls. Until recently, we determined correction factors for attenuiation and scatter by measurement, but resulting values were not logically valid, so applied Monte Carlo calculation. Differences between values obtained experimentaly and by calculation for AIST ionization chambers were small, compared to the relatively large differences obtained for almost all ionization chambers at other NMIs, possibly because only AIST ionization chambers are placed at a 45-degree angle to gamma ray beams.

3 illus, 1 table, 12 ref

Ultrasonic velocity and excess thermodynamic parameters of the binary mixtures of 3-methoxy acetophenon and 4-chloro acetophenone containing dimethyl sulphoxide as common component
Subramanyam Naidu P;Prabhakara Rao N;Ravindra Prasad K

011747   Subramanyam Naidu P;Prabhakara Rao N;Ravindra Prasad K (Department of Physics, S. V. U. P. G. Centre, Kavali-524 201) : Ultrasonic velocity and excess thermodynamic parameters of the binary mixtures of 3-methoxy acetophenon and 4-chloro acetophenone containing dimethyl sulphoxide as common component. J pure appl Ultrasonics 2002, 24(2), 36-46.

Ultrasonic velocities have been measured in the binary mixtures of 3-methoxy acetophenone and 4-chloro acetophenone containing dimethyl sulphoxide as a common component in the temperature range 30-50°C. The excess thermodynamci parameters like β^E, Π^E, L_f^E, V^E, etc. have been compued and their variation with conentration is discussed in the light (context) of the molecular interactions like diple, charge transfer, dispersive forces, etc. In both the mixtures, strong AB interactions appear to be predominant while in the first mixture i.e., with 3-methoxy acetophenone, weak bonding dispersive forces are also indicated.

16 illus, 4 tables, 24 ref

Systematic hardness measurements on single crystals and polycrystalline blanks of cesium halides
Sirdeshmukh D B;Geeta Krishna P;Subhadra K G

011746   Sirdeshmukh D B;Geeta Krishna P;Subhadra K G (Physics Dep, Kakatiya University, Warangal-506 009) : Systematic hardness measurements on single crystals and polycrystalline blanks of cesium halides. Bull Mater Sci 2002, 25(3), 203-07.

Vickers and knoop hardness measurements were carried out on CsBr and CsI single crystals. Polycrystalline blanks of CsCl, CsBr and CsI were prepared by melting and characterized by X-ray diffraction. Vickers hardness measurements were carried out on these blanks. The hardness values were correlated with the lattice constant and the Schottky defect formation energy.

4 illus, 1 table, 20 ref

Phonons in mixed superionic fluorites (BaF₂)_1-x(LaF₃)_x
Sinha M M

011745   Sinha M M (NO, , ) : Phonons in mixed superionic fluorites (BaF₂)_1-x(LaF₃)_x. Bull Mater Sci 2002, 25(6), 459-62.

2 illus, 16 ref

Fermion local charged boson model and cuprate superconductors
Sinha K P;Kakani S L

011744   Sinha K P;Kakani S L (Research laboratory of Electronic, Massachusetts Institute of Technology, Cambridge MA 02139 USA) : Fermion local charged boson model and cuprate superconductors. Proc Natn Acad Sci India-Sect A 2002, 72(3), 153-214.

Detailed features of combined lochon and phonon mediated pairing mechanism are presented a contact with the normal and superconducting state properties of HTSC.

19 illus, 21 ref

Study of cosmic ray storm of February 2000
Shrivastava P;Shrivastava P K;Chamadia P K

011743   Shrivastava P;Shrivastava P K;Chamadia P K (Department of Physics, Govt. New Science College, Rewa-486 001) : Study of cosmic ray storm of February 2000. Acta Cienc Indica-Phys 2002, 28(4), 245-9.

Slow decrease in cosmic ray intensity followed by a slow recovery in cosmic ray decrease is called cosmic ray storm. Such a significant event of cosmic ray storm is noted in February 11 to 16, 2000 which occurs during the high solar activity period of sunspot cycle 23. In this work we have done a systematic study to derive relationship between cosmic ray decrease and geomagnetic disturbances. Results of analysis indicate a strong relationship between geomagnetic activity and cosmic ray intensity on short term basis.

3 illus, 6 ref

Method employing STM for the estimation of relative changes in the work function of modified metal tips
Sharma R B;Vinod C P;Kulkarni G U

011742   Sharma R B;Vinod C P;Kulkarni G U (Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P O, Bangalore-560 064) : Method employing STM for the estimation of relative changes in the work function of modified metal tips. Bull Mater Sci 2002, 25(3), 247-9.

I-z spectroscopy measurements using a scanning tunnelling microscope (STM) were carried out to determine the change in the work function of a W tip following one monolayer (1 ML) deposition of Ni and subsequent annealing at 700 K. The variation in the actual gap voltage obtained from the I-z data of the clean tip was used in the calculation. The estimated values of the change in work function, 0.16 eV and 0.59 eV, for as-deposited and annealed tips, respectively match closely with the reported values. The method is generally applicable to chemically modified metal tips.

2 illus, 12 ref

Simultaneous measurements of thermal conductivity and diffusivity of Se₈₀ In_20-xIn_x (x=2, 4, 6 and 10) chalcogenide glasses at roomtemperature
Saxena N S;Imran M M A;Singh K

011741   Saxena N S;Imran M M A;Singh K (Physics Dep, University of Rajasthan, Jaipur-302 004) : Simultaneous measurements of thermal conductivity and diffusivity of Se₈₀ In_20-xIn_x (x=2, 4, 6 and 10) chalcogenide glasses at roomtemperature. Bull Mater Sci 2002, 25(3), 241-5.

Measurements of thermal conductivity and thermal diffusivity of twin pellets of Se₈₀Te_20-xIn_x (x=2, 4, 6 and 10) glasses, prepared under a load of 5 tons were carried out at room temperature using transient plane source (TPS) technique. The measured values of both thermal conductivity and diffusivity were used to determine the specific heat per unit volume of the said materials in the composition range of investigation. Results indicated that both the values of thermal conductivity and thermal diffusivity increased with the addition of indium at the cost of tellurium whereas the specific heat remained almost constant. This compositional dependence behaviour of the thermal conductivity and diffusivity has been explained in terms of the iono-conveialent type of bond which In makes with Se as it is incorporated in the Se-Te glass.

6 illus, 10 ref

On the symmetry of phosphorous doped ZnSe
Sankar N;Ramachandran K

011740   Sankar N;Ramachandran K (Theoretical Physics Dep, Madurai Kamaraj University, Madurai - 625 021) : On the symmetry of phosphorous doped ZnSe. Bull Mater Sci 2002, 25(4), 329-34.

The site symmetry of P doped ZnSe is analysed in detail, as the recent experiments suggest two possible symmetries T_d and C_3v. The reduction to C_3v is attributed to the presence of natural impurity, Ga. Calculations based on molecular model and Green's functions suggest that the symmetry C_3v is possible with ZnSe : P when Jahn Teller distortion of about <126> 0.2 Å (towards one of Zn atom) is assumed. This has been supported by other experiments.

2 illus, 7 tables, 15 ref

Development of diamond coated tool and its performance in machining Al-11
Sahoo B;Chattopadhyay A K;Chattopadhyay A B

011739   Sahoo B;Chattopadhyay A K;Chattopadhyay A B (Mechanical Engineering Dep, Indian Institute of Technology, Kharagpur-721 302) : Development of diamond coated tool and its performance in machining Al-11. Bull Mater Sci 2002, 25(6), 487-91.

An attempt has been made to deposit CVD diamond coating conventional carbide tool using hot filament CVD process. ISO grade K10 turning inserts with SPGN 120308 geometry were used to deposit diamond coating. This diamond coating well covering the rake surface, cutting edges and flank surfaces could be successfully deposited. the coatings were characterized by SEM, XRD and Raman spectroscopy for coating quality, morphology etc. Performance of diamond coated tool relative to that of uncoated carbide tool was evaluated in turning Al-11% Si alloy under dry environment. The diamond coated tool outperformed the uncoated carbide tool which severely suffered from sizeable built-up edge formation leading not only to escalation of cutting forces but also poorer surface finish. In contrast, the diamond coated tool, owing to chemical inertness of diamond coating towards the work material, did not show any trace of edge built-up even in dry environment and could maintain low level of cutting forces and remarkably improved surface finish.

11 illus, 2 table, 8 ref

Focal shift in an imaging system with polarization phase modulated aperture plane
Roy Chaudhury D;Bhattacharya K;Chakroborty A K

011738   Roy Chaudhury D;Bhattacharya K;Chakroborty A K (Dep of Appl Physics, Calcutta University, Chandra Road, Kolkata-700 009) : Focal shift in an imaging system with polarization phase modulated aperture plane. J Optics 2002, 31(3), 117-28.

The concept of polarization phase has been utilized to introduce a circularly symettric phase step in the aperture plane of an imaging system. Since the polarization phase can be controlled by variation of the polarization parameters involved, the effective focal length of the imaging system can be varied within a small range. In the proposed technique, the modification of the focal length is obtained by rotating a retarder at the input of the imaging system. A study of the PSFs at the shifted focal planes shows that the quality of the image in these plaes is comparable to that produced by a diffraction-limited system at Gaussian focus. The focal plane displacement achievable is about 300μm of a f/10 system at 550 nm.

6 illus, 29 ref

Tunneling of electrons through semiconductor superlattices
Roy C L

011737   Roy C L (Dep of Physics and Meteorology, Indian Institute of Technology, Kharagpur-721 302) : Tunneling of electrons through semiconductor superlattices. Bull Mater Sci 2002, 25(6), 469-71.

Report a study of tunneling of electrons through semiconductor sperlattices (SSL); specially, we have analysed diverse features of transmission coefficient of SSL. The SSL considered is Ga_0.7Al_0.3As-GaAs which has been drawing considerable attention during the recent past on account of some typical features of its band structure.

3 illus, 4 ref

Interreflection calculation under daylight by monte carlo method
Roy B;Bandyopadhya S R

011736   Roy B;Bandyopadhya S R (Illumination Engineering Laboratory, Dep of Electrical Engng, Jadavpur, , Kolkata-700 032) : Interreflection calculation under daylight by monte carlo method. J Optics 2002, 31(3), 95-104.

Describes the theoritical basis of determining interreflected component of Daylight Factor (DF) by applying Monte Carlo method. A model room is considered for this stimulation. The method is quite simple and yields a good accuracy of calculation. The theoritical results are then compared with the results obtained by applying Finite Element for the same room.

2 illus, 1 table, 8 ref

Study of fragment mass distribution in the impact fragmentation of glass slides
Ray S;Basak S

011735   Ray S;Basak S (NO, Presidency College, Kolkata) : Study of fragment mass distribution in the impact fragmentation of glass slides. Phys Educ 2002, 19(3), 211-21.

Describes a simple experiment involving 'pathology micro-slides' which were allowed to fall from various heights and undergo fragmentation. Fragments from a given height of fall were collected and their mass distribution was determined. Founds the following relation between the mass of an average fragment (m_av) and the height of fall (h): m_av ~h^-1.7. Fragment mass verses frequency of occurence, i.e. the mass distribution, for different heights of fall, are also given in this report.

4 illus, 4 tables

Spectroscopic properties of II-VI semiconductors with killer impurities (Fe, Co and Ni)
Rastogi N;Saxena M;Agarwal A;Rastogi S;Singh S

011734   Rastogi N;Saxena M;Agarwal A;Rastogi S;Singh S (Department of Sciences and Humanities, Moradabad Institute of Technology, Moradabad-244 001) : Spectroscopic properties of II-VI semiconductors with killer impurities (Fe, Co and Ni). Acta Cienc Indica-Phys 2002, 28(3), 113-16.

The spectral distribution of photocurrents in II-VI semiconductor samples when it is doped with the killer impurities Fe, Co and Ni modify the photo conducting characteristics. It is found that at different wavelengths the spectral distribution of photocurrent for all the samples with Fe, Co and Ni show a broad spectrum and it is observed that ZnS : Cu, O has one band while all other photoconductors have two bands. The photosensitivity of the copper peak when the sample is droped with Co, increases and the charge transfer between Cu and Co suggest that the sensitivity of copper peak increase in presence of Co because the charge is transferred from Co to Cu ions.

1 illus, 22 ref

Investigations of surface characterization of silicone rubber due to tracking phenomena under a.c. and d.c. voltages
Rao U M;Abdul Majeed S S M S;Venkataseshaiah C;Sarathi R

011733   Rao U M;Abdul Majeed S S M S;Venkataseshaiah C;Sarathi R (Dep of Electrical Eng, Indian Institute of Technology, Chennai-600 036) : Investigations of surface characterization of silicone rubber due to tracking phenomena under a.c. and d.c. voltages. Bull Mater Sci 2002, 25(6), 473-5.

Tracking phenomena has been studied with silicone rubber material under the a.c. and d.c. voltages following IEC-587 standards. The surface condition of the tracked zone was analysed using wide angle X-ray diffraction (WAXD) and thermogravimetric differential thermal analysis (TG-DTA) studies. The tracking time was different for a.c. and d.c. voltages.

6 illus, 1 table, 4 ref