019289   Behnke T (NO, Deutsches Elektronen Synchroton, Notkestrasse 65, D-22603 Hamburg, Germany, Email: ties.behnke@desy.de) : The LDC detector concept. Pramana J Phys 2007, 69(5), 697-702.

In preparation of the experimental program at the international linear collider (ILC), the large detector concept (LDC) is being developed. The main points of the LDC are a large volume gaseous tracking system, combined with high precision vertex detector and an extremely granular calorimeter. The main design force behind the LDC is the particle flow concept.

3 illus, 2 ref

019288   Ananthanarayan B (Centre for High Energy Physics, Indian Institute of Science, Bangalore-560 012, Email: anant@cts.iisc.ernet.in) : Probing space-time structure of new physics with polarized beams at the international linear collider. Pramana J Phys 2007, 69(5), 849-54.

At the international linear collider large beam polarization of both the electron and positron beams will enhance the signature of physics due to interactions that are beyond the standard model. Here we review our recently obtained results on a general model-independent method of determining for an arbitary one-particle inclusive state the space-time structure of such new physics through the beam polarization dependence and angular distribution of the final state particle.

2 tables, 7 ref

019287   Ajay Kumar;Misra D;Kelkar A H;Kadhane U R; Tribedi L C;Thulasiram K V (NO, Tata Institute of Fundamental Research, Colaba, Mumbai 400 005, Email: lokesh@tifr.rfis.in) : High resolution X-ray crystal spectrometer to study electron and heavy-ion impact atomic collisions. Pramana J Phys 2007, 68(6), 983-94.

Studieds fast ion-atom and electron-atom collision processes using a reconditioned high resolution X-ray spectrometer. The X-rays, generated by the collisions, are dispersed by a curved ADP crystal (Johansson geometry) and detected by a gas proportional counter. A self-written Lab VIEW based program has been used to give precise and controlled movement to the crystal and for data acquisition. The performance was tested by detecting the Kα diagram and satellite lines of several elements. The Kα satellite lines of Al have been studied in collision with 3-12 keV electrons and 40 MeV C⁴ ions. In ion collisions as large as four L-vacancies are created simultaneously with the K-vacancy, compared to two satellites in case of the e-impact. In addition, we have measured the X-rays from H-, He- and Li-like Si ions which arise due to the electron loss/capture process in highly charged 80 MeV Si⁷ ions in collision with thin carbon foil. Approximate charge state distribution has been obtained using this new technique.

7 illus, 22 ref

018218   Tiwari M;Singh R A (Physics Dep, Dr H S Gour University, Sagar-470 003) : Three site hole hopping in high Tc superconductors. Indian J pure appl Phys 2008, 46(2), 139-44.

Dynamics of holes containing three site hole hopping and parallel hopping has been studied. A new type of hole-hole correlation is discussed. The effect of three site term and parallel hopping term on hole-hole correlation has been investigated.

018217   Tharayil N J;Raveendran R;Vaidyan A V (Physics Dep, Sree Narayana College, Kollam, Kerala, Email: nishajohntharayil@yahoo.co.in) : Synthesis and characterization of nanosized cobalt-manganese spinel oxide. Indian J pure appl Phys 2008, 46(1), 47-53.

Nanoparticles of cobalt-manganese oxide were prepared by chemical co-precipitation method by decomposition of their respective metal chlorides, sodium carbonate and ethylene diamene tetra acetic acid (EDTA). The heat treatment of the ground precursor powders at their respective decomposition temperature and beyond, results in the evolution of heat from the combustion of the residual carbonaceous material. This facilitates the reaction among the constituent metal ions and the formation of the desired oxide phase at low temperature. The average crystallization size was determined from X-ray diffraction line broadening and the diffractogram was compared with JCPDS data to identify the crystallographic phase of the particle. The shift in d--value due to the nano nature was also analyzed.The internal elastic micro strain was calculated and it was seen that as the particle size increases strain decreases. The effect of sintering on the particle size was also analyzed. The nano nature of the mixed oxide was also analyzed from the TEM and AFM studies. The FTIR studies have been used to confirm the formation of metal oxide. The characteristic stretching and bending frequencies of the sample were also analyzed. The absorption spectra of the material in the UV-Vis -NIR range were recorded. Strong absorption bands are observed to occur at 550 nm and a weak band around 730nm. From the analysis of absorption spectra, the cobalt-manganese oxide (sintered at 500°, 700° and 900°C) have been found to have direct band gaps ranging from 2.07 to 1.59 eV.

018216   Thakur A;Mathur P;Singh M (Physics Dep, H P University, Summer Hill, Shimla-171 005, Email: at_phy_hpu@yahoo.co.in) : Controlling the properties of Mn-Zn ferrites at high frequency by substituting In<. Indian J pure appl Phys 2008, 46(1), 42-6.

The effect of substitution of In³⁺ and Al³⁺ ions on the electrical and magnetic properties of Mn-Zn spinel ferrites has been investigated. The substitution of In³⁺ ions in place of Fe³⁺ ions resulted in an increase of lattice parameter, because of the larger size of the substituted ions, whereas lattice parameter decreased on substituting Al³⁺ ions in place of the Fe³⁺ ions, owing to their smaller size. The dc resistivity was found to increase with the substitution of In³⁺ and Al³⁺ ions in the Mn-Zn ferrite system. The improvement in the dc resistivity has been observed at the expense of deterioration in the magnetic properties of Al³⁺ substituted Mn-Zn Ferrites. A significant reduction in the value of initial permeability, saturation magnetization and Curie temperature was observed with successive increase of Al³⁺ ions. The saturation magnetization and initial permeability were found to increase with incorporation of In³⁺ ions. A marked increase in the value of initial permeability was found for the Mn_0.4Zn_0.6In_0.5Fe_1.5O₄ ferrites. The Curie temperature was found to decrease with an increase of In³⁺ ion concentration. Possible mechanisms contributing to these processes have been discussed.

018215   Suresh Kumar B;Rajendra Babu K (Physics Dep, Mahathma Gandhi College, Thiruvananthapuram-695 004) : Effect of L-arginine, L-histidine and glycine on the growth of KDP single crystals and their characterization. Indian J pure appl Phys 2008, 46(2), 123-6.

Optically good quality single crystals of pure and amino acid doped KDP have been grown by slow evaporation method at constant temperature (40°C). The effect of amino acid dopants on the growth and characterization of KDP crystals has been studied. The grown crystals are characterized by density, melting point determination and X-ray powder diffraction. The presence of functional groups of crystals are qualitatively analysed from FTIR spectra. Thermal properties like decomposition temperatures and weight loss have been reported from the TGA and DTA analysis. The transparency of the grown crystals has been confirmed using UV-Vis spectra. It has been found that SHG efficiency of KDP, containing amino acids is higher than pure KDP crystals. Dielectric behaviour of pure and doped samples has been studied at a temperature range 30 - 180°C and a constant frequency 1 kHz.

018214   Sunandana C S (School of Physics, University of Hyderabad, Hyderabad-500 046, Email: csssp75@yahoo.co.in) : Contemporary issues in glass science. Indian J pure appl Phys 2008, 46(1), 7-11.

Glasses-including non-oxide glasses-continue to be investigated for basic understanding and potential applications. The inter-related issues: glass formation as a self-organization process, glass transition, fast-ion relaxation in glasses, nanocrystallization and mixed alkali effect have been presented. Last two issues in the light of relevant experimental work including our own work on tellurite glasses have been focussed.

018213   Sukhvir Singh;Arora M;Ram Kishore (NO, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110 012, Email: sukhvir@mail.nplindia.ernet.in) : Estimation of measurement uncertainty in characterization of materials using transmission electron microscope (TEM) at NPL, India. MAPAN 2007, 22(4), 263-8.

TEM is one of the very sophisticated, sensitive and accurate tool for carrying out microstructural detailed investigations of the materials in terms of their crystallographic structure, lattice imaging, phase identification, different variety of defects present, particle size and shape analysis etc. at the nano scale level. The accuracy and efficiency of electron microscope depends upon the magnification and resolution of the instrument. In the investigations, thermally evaporated thin films of high purity gold deposited on KCl substrate under high vacuum conditions (of the order of 10-6 torr) and thin films of aluminium were synthesized by sputtering on amorphous silicon grown by PECVD technique. These films were characterized by using Transmission Electron Microscope (TEM) make JEOL, model JEM 200CX operated at 120, 160 and 200 kV accelerating voltages. The deposition process of gold nanoparticles and other materials was precisely monitored to get high quality, stable and with repeatable sized uniform particles. These films were thoroughly scanned under TEM at high magnification of the order of 200,000 X. The aim of these studies is to find the size of different small and big sized particles and evaluate the associated measurement uncertainty as per the standard GUM document.

4 illus, 3 tables, 14 ref

018212   Singh Y P;Nijhawan S K;Anjula (NO, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110 012, Email: ypsingh@mail.nplindia.ernet.in) : Realization of copper fixed point in sealed cell for calibration of noble metal thermocouples on ITS-90. MAPAN 2007, 22(4), 269-75.

Calibration of noble metal thermocouples requires quite reliable temperature sources to provide traceability of measurement directly or indirectly to ITS-90. The freezing point of Cu is one of the defined fixed points on ITS-90 and is very useful practical reference temperature between Au and Pd melting points for calibration and evaluation of high temperature thermocouples. Reports the realization of freezing point of Cu (1084.62°C) in the form of sealed cell by noble metal thermocouples of Pt-10%Rh/Pt (Type-S) and Pt-13%Rh/Pt (Type-R) using a three zone heating furnace. The sealed cell is made of ultra high purity graphite to contain 6N purity Cu metal. The melting and freezing points of Cu were measured and found to be reproducible within better than 0.001mV. No apparent difference between melting and freezing temperature was observed at heating/cooling rate of 0.5°C/ min. The individual difference at Cu-point, measured by each thermocouple with respect to the value as stated in the ITS-90, is lying within the overall uncertainty of measurement associated with the realization of Cu point. The expanded uncertainty of measurement associated with the realization of freezing temperature of Cu was evaluated and expressed. The Cu point as measured with Type-S thermocouple is reported to be 1084.62°C ±0.36°C and that with Type-R thermocouple is reported to be 1084.62°C ± 0.33°C.

3 illus, 1 table, 9 ref

018211   Singh Y P (NO, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110 012, Email: ypsingh@mail.nplindia.ernet.in) : Evaluation and exrpession of uncertainty in the calibration of screw type industrial lamps using photoelectric pyrometer. MAPAN 2007, 22(4), 235-45.

Describes the details of estimation and expression of uncertainty by universal method in the temperature measurement and calibration of special type of industrial ribbon lamp (screw type) by comparing it against spectral photoelectric linear pyrometer in the high temperature range above 1000 °C using high stability transfer standard tungsten lamps. It is an indirect calibration where the photocurrent generated by the radiating lamp provides a means to compare the temperature. The intensity of radiation depends upon the current flowing through the lamp, which is precisely measured. Thus the lamp is calibrated in terms of temperature versus the current flowing through it. A sufficient number of data were taken on the measurement of photocurrent of radiating lamps to calculate the uncertainty in the temperature with a confidence-level of 95% approximately for a normal probability distribution. The calculation of uncertainty was supported by a case study on calibrating industrial lamps, one at 1000 °C and the other at 2200 °C. The results of calibration are reported to be 1000 °C ± 2.54 °C for lamp No.192A (lamp current 4.9916 A) and 2200°C ±3.64 °C for lamp No.952B (lamp current 17.8459 A) respectively.

2 illus, 5 tables, 11 ref

018210   Singh R;Tripathi S K;Kumar S (Physics Dep, Christ Church College, Kanpur- 208 001) : Role of Cu additive in the density of localized states in α-Ge₂₀Se₈₀ glassy alloy. Indian J pure appl Phys 2008, 46(1), 38-41.

The dc conductivity at high electric fields in vacuum evaporated amorphous thin films of Ge₂₀Se₈₀ and (Ge₂₀Se₈₀)98Cu₂ glassy alloys has been measured. Current-voltage (I-V) characteristics have been measured at various fixed temperatures. In these samples, ohmic behaviour is observed at low electric fields. However, at high electric fields (E<126>10⁴V/cm), non ohmic behaviour is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC, the density of defect states (DOS) near Fermi level has been calculated. An increase in DOS has been found when we incorporate Cu in the pure binary -Ge₂₀Se₈₀ glassy system. The peculiar role of Cu as a third element in the binary -Ge₂₀Se₈₀ glassy alloy is also discussed.

018209   Saraf A K;Tiwari M (Physics and Electronics Dep, Dr Harisingh Gour Vishwavidyalaya, Sagar) : Gaussian minimum shift keying systems with additive white Gaussian noise. Indian J pure appl Phys 2008, 46(1), 65-70.

The basic properties of an I-Q Gaussian minimum shift keying (GMSK) with additive white Gaussian noise have been investigated. The probability of error for non-fading and fading channels of communication has been analyzed and discussed. The hardware realization is simple and straight forward like minimum shift keying (MSK) system. Some analytical results have been achieved and compared with machine computed GMSK results of others. The modular circuits are available for VLSI design. Thus, the system developed is suitable for VLSI design of GMSK.

018208   Ritter M;Dziomba T;Hemmleb M;Koenders L; Kranzmann A (NO, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany, Email: martin.ritter@bam.de) : 3D-calibration method for the quantitative SPM measurement of hardness indenters. MAPAN 2007, 22(3), 167-75.

Introduces the application of a new 3D calibration method for the calibration of scanning probe microscopes (SPM) in order to be able to obtain faster and better quantitative topography measurements for the determination of technical, dimensional and geometrical surface parameters. The applied 3Dcalibration routine is based on spatially distributed reference landmarks (nanomarkers), and, not only determines the scale factors in all dimensions but also the coupling factors as shear between all coordinate axes in one step. Shows that the 3D-calibration method is a valuable alternative and enhancement to existing calibration strategies that conventionally apply two calibration steps, i.e., separate determinations of the calibration parameters for lateral and vertical scales. As an application example to technical surfaces, a hardness micro-indenter measured by SPM is discussed. The uncalibrated data, the conventionally calibrated data, and, the 3D-calibrated data are compared and analyzed.

11 illus, 4 tables, 23 ref

018207   Rangolia M K;Chhantbar M C;Tanna A R;Modi K B;Baldha G J;Joshi H H (Physics Dep, Saurashtra University, Rajkot-360 005) : Magnetic behaviour of nano-sized and coarse powders of Cd-Ni ferrites synthesized by wet-chemical route. Indian J pure appl Phys 2008, 46(1), 60-4.

Nano particles having particle size in the range (80 -100Å) for compositions (x = 0.2, 0.4, 0.6, 0.8) of Cd_xNi_1-xFe₂O₄ spinel ferrite system are prepared by chemical co-precipitation route. The structural and magnetic properties have been studied by X-ray diffraction, magnetization, susceptibility and ⁵⁷Fe Mossbauer spectroscopy measurements, before and after high temperature annealing. The magnetic behaviour is explained by invoking the concept of superparamagnetism assuming core-shell structure of the nano-particles.

018206   Ranbir Singh;Kaushik B K;Quamara J K (Applied Physics Dep, National Institute of Technology, Kurukshetra-136 119) : Multiple relaxation investigations in polyetherimide: Thermally stimulated depolarization current technique. Indian J pure appl Phys 2008, 46(2), 127-33.

Thermally stimulated depolarization current (TSDC) technique has been used for investigating various dielectric relaxation processes in polyetherimide. The TSD currents in the temperature range 20°-250°C (in certain cases up to 300°C) were obtained as functions of polarizing field (E_p; 20-350 kV/cm), polarizing temperature (T_p; 60° -180°C), poling time (t_p; 0.5-2 h), sample thickness (d; 25-120 μm), heating rate (h; 2°-6°C/min), and storage time (ts; 0-552 h). The current maxima in the TSDC spectra reveal the presence of two major relaxation processes termed as β- (around 130°C) and α- (around 190°C), associated with dipolar relaxation and space-charge relaxation processes, respectively. However, in certain cases, we observe merging of β- and α-relaxation processes to become the αβ-relaxation process (140°-180°C). The observed dependence of the peak temperature T_m on polarizing temperature and poling time indicates a continuous distribution of relaxations. The high E_p/T_p samples also show a relaxation (ρ) around 260°C associated with charge injection phenomenon. The low temperature region of TSDC spectra (30°-70°C) shows the presence of a weak relaxation (β'), considered as a satellite of the main dipolar relaxation process. The activation energies for various relaxation processes have been calculated using Bucci plot method.

018205   Ramachandra Prasad V;Bhaskar Reddy N (Mathematics Dep, Madanapalle Institute of Technology and Science, Madanaplle-517 325, Email: rcpmaths@yahoo.com) : Radiation and mass transfer effects on an unsteady MHD convection flow past a semi-infinite vertical permeable moving plate embedded in a porous medium with viscous dissipation. Indian J pure appl Phys 2008, 46(2), 81-92.

An unsteady, two-dimensional, hydromagnetic, laminar mixed convective boundary-layer flow of an incompressible, Newtonian, electrically-conducting and radiating fluid along a semi-infinite vertical permeable moving plate with heat and mass transfer is analyzed, by taking into account the effect of viscous dissipation. The plate moves with a constant velocity in the direction of fluid flow while the free stream velocity follows an exponentially increasing small perturbation law. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and non-harmonic functions. Numerical evaluation of the analytical results is performed and graphical results for velocity, temperature and concentration profiles within the boundary layer and tabulated results for the skin-friction coefficient, Nusselt number and Sherwood number are presented and discussed. It is observed that, when the radiation parameter increases, the velocity and temperature decrease in the boundary layer, whereas when thermal and solutal Grashof increase, the velocity increases.

018204   Rakshit B;Srivastava V;Sanyal S P;Jha P K; Ravindran T R;Arora A K (Physics Dep, Barkatullah University Bhopal, Bhopal-462 026, Email: spsanyal@sancharnet.in) : Vibrational spectroscopy and phonon dispersion of GaSb. Indian J pure appl Phys 2008, 46(1), 20-2.

The lattice vibrational properties of III-V semiconductor compound, GaSb have been investigated experimentally using Raman scattering and Fourier Transform Infrared spectroscopic techniques. The experimental results by both the techniques show a sharp peak around 222 cm^-1. The experimental results have been analyzed using deformable bond approximation (DBA), whose formalism is a simplified version of deformation dipole model (DDM). The calculated phonon dispersion curves for GaSb, are in excellent agreement with the available inelastic neutron scattering data. The results will be useful to characterize the nano-structured GaSb.

018203   Patel K;Negi P S (NO, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110 012, Email: kpatel@mail.nplindia.ernet.in) : Simple approach to measure the gain of horn antenna and its error analysis using the three-antenna method. MAPAN 2007, 22(4), 257-61.

Evaluation of uncertainty in measurement is always an exciting and difficult task at the same time, since it depends on the measurement set up and associated technique used even for the same parameter. Presents the uncertainty evaluation in the gain measurement setup using the three-antenna gain method, a well-established method for determining the antenna gain and polarization parameters. Experimental studies have been performed for the gain measurement of three pyramidal horns in the frequency range 8.2 GHz to 12.4 GHz at frequency steps of 500 MHz. The measured gain values for the three horns varied from 17.5 dB to 22.5 dB and its associated expanded uncertainty for k=3 estimated to within ± 0.3 dB through out the measured frequency range. The comparison of computed gains using the aperture dimension and gain measurements using the three-antenna gain method along with the associated uncertainties is reported.

6 illus, 2 tables, 8 ref

018202   Morrell R;Roebuck B (NO, National Physical Laboratory, Teddington, Middlesex, UK, Email: bryan.roebuck@npl.co.uk) : Quantitative challenges in characterising the mechanical properties of hard materials. MAPAN 2007, 22(3), 153-66.

Hard materials present significant metrological challenges in order to characterise, in particular, their mechanical properties. For example, when measuring hardness the indentations are small and difficult to measure accurately. In addition, deformation processes can be dimension and microstructure dependent, so the choice of indentation load requires significant underpinning research to ensure that the measured values are repeatable and reproducible. Often, surface mechanical measurements result in the development of small cracks. These also require characterisation and, with careful quantitative measurements, can reveal information on hard material toughness.

12 illus, 3 tables, 24 ref

018201   Mishra V;Jain S C;Nahar Singh;Poddar G C; Kapur P (NO, Central Scientific Instruments Organisation, Chandigarh-160 030) : Fuel adulteration detection using long period fiber grating sensor technology. Indian J pure appl Phys 2008, 46(2), 106-10.

Adulteration of petrol and diesel with kerosene is a common malpractice in India because kerosene has been made easily accessible at a price much cheaper than that of petrol and diesel. Such adulteration results in increased pollution, decrease in engine or machine performance, reduced lifetime of components, lower returns for money of the buyers and decrease in availability of kerosene to the needy people. There is no standard technique that is followed universally for detection of adulteration level. In this study, application potential of long period fiber grating (LPFG) sensor technology to detect fuel adulteration has been investigated. It was possible to detect presence of 10% contaminant in petrol and diesel using LPFG technique whereas the traditional technologies are able to detect presence of about more than 20% of the same.

018200   Mingard K P;Roebuck B;Bennett E G;Thomas M; Wynne B P;Palmiere E J (Engineering and Process Control Div, National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK, Email: ken.mingard.npl.co.uk) : Meterological aspects of electron backscattering diffraction in characterising hot deformation grain structures. MAPAN 2007, 22(3), 177-200.

Electron Backscattering Diffraction as a routine tool to characterise microstructure has rapidly grown in use this century because of improvements to both software and hardware which have enabled highly detailed crystallographic information to be acquired automatically from large areas of a polished specimen within a relatively short time. However, selection of the appropriate operating parameters before acquisition and choice of methods of manipulating and interpreting the large quantity of data at the end of the map all affect the final results significantly, even on relatively simple single or two phase materials. The metrology of grain size measurement in representative engineering alloys is considered to illustrate these issues of data acquisition and analysis. Choice of step size in producing EBSD maps of hot deformed alloys is shown to be critical, especially in cases of partial recrystallisation where a bimodal distribution exists. Inappropriate use of noise reduction methods can lead to significant changes in grain size. Methods of reporting grain sizedistributions over large areas with gradients in grain size are discussed, and the ability of EBSD to select particular subgroups by grain size, orientation or aspect ratio are shown to be very useful to enable visualisation of the effects of deformation. The higher resolution of EBSD in comparison with optical methods leads to smaller grain sizes being reported by EBSD, although broad trends may be followed by both techniques.

16 illus, 2 tables, 15 ref

018199   Liakath Ali Khan F;Sivagurunathana P;Asghar J (Physics Dep, Islamiah College, Vaniyambadi, Tamilnadu-635 752, Email: shamisardar@yahoo.com) : FTIR study of hydrogen bonding interactions between alkyl esters and hexanol, p-cresol in carbon tetrachloride. Indian J pure appl Phys 2008, 46(1), 12-9.

The effect of hydroxyl group in hexanol and p-cresol on the carbonyl vibration of representative compounds belonging to methyl methacrylate, ethyl methacrylate and butyl methacrylate in carbon tetrachloride has been studied by FTIR spectroscopic method. The integrated intensities and change in dipole moments for O-H and C=O bonds were calculated. Utilizing Nash method, the formation constant and free energy of the 1:1 complexes have been calculated. The formation constant and free energy change values vary with chain length of acrylic esters, which suggests that the strengths of the intermolecular hydrogen bonds (O-H_O=C) are dependent on chain length of acrylic esters. The strength of the intermolecular C=O: HO bonds is shown to be dependent on the basicity of the C=O group of alkyl esters and the acidity of the proton donor.

018198   Liakath Ali Khan F;Sivagurunathan P;Asghar J (Physics Dep, Islamiah College, Vaniyambadi, Tamilnadu-635 752) : Dielectric relaxation studies of alkyl acrylates with phenol derivatives in carbon tetrachloride using microwave absorption techniques. Indian J pure appl Phys 2008, 46(1), 54-9.

The dielectric relaxation of alkyl acrylates (methyl acrylate, ethyl acrylate and butyl acrylate) with phenol derivatives (p-cresol, p-chlorophenol, 2,4-dichlorophenol and p-bromophenol) has been measured at microwave frequency 9.37 GHz in dilute solution of carbon tetrachloride at 308K. Different dielectric parameters like dielectric constant ε' and dielectric loss ε" at microwave frequency, static dielectric constant ε_° and dielectric constant ε_∞ at optical frequency have been determined. The relaxation time and activation energy have been determined using the measured dielectric data. The results show a linear dependence of relaxation time on alkyl chain length of acrylic esters and acidity of phenol derivatives. Comparative study of free energy of activation for the dielectric relaxation and viscous flow suggests that the process of viscous flow involves greater interference by neighbours than does dielectric relaxation, as the latter takes place by rotation only whereas the viscous flow involves both rotational and translational motion. The validity of the single frequency equation of Higasi et al. Bull Chem Soc Japan, 44(1971)988. For multiple relaxation time τ₁ is found to be function of the hydrogen bonding strength of phenolic hydrogen whereas the group rotation relaxation time τ₂ is a function of the steric interaction of proton donor. The relaxation time is maximum at 50:50 mol% ratio.

018197   Kuryan S;Abraham R;Isac J (NO, St Stephen's College, , Kollam, Kerala) : (NULL). Indian J pure appl Phys 2008, 46(1), 32-2.

Samarium barium copper oxalate (SmBaCuOx) crystals were grown using silica gel technique by the diffusion of a mixture of samarium chloride, barium chloride and cuprous nitrate into the test tube having the set gel containing oxalic acid. The grown crystals were characterized by X-ray diffraction analysis, Inductively Coupled Plasma Atomic Emission analysis and microhardness measurements. The variation of dielectric constant ε_r and dielectric loss D in the frequency range100Hz - 1MHz has been studied and reported. The electrical conductivity of SmBaCuOx crystals was found to increase with increase of frequency.

018196   Kude V P;Khairnar R S (Applied Physics Dep, MGM College of Engineering, Nanded, Maharashtra, Email: rk2kin@yahoo.com) : Fabrication and numerical evaluation of the tapered single mode optical fiber: detection of change in refractive index. Indian J pure appl Phys 2008, 46(1), 23-9.

The fabrication of the tapered single mode fiber has been carried out. The tapered fiber is numerically evaluated for propagation behaviour of light by means of bound rays and tunneling rays in tapered portion. The nature of bound and tunneling rays as a function of refractive index is observed numerically, which shows that tapered portion of the fiber is suitable for sensor application. To make the fiber sensitive to refractive index of the medium other than core medium, it is etched up to fiber core using hydrofluoric acid (HF). The sensitivity of the sensor has been studied by varying the diameter of the etched portion in the fiber. The tapered portion is dipped in the DMSO solution having various molarity thereby exhibiting different refractive indices. The optical signal is passed through the fiber and output signal intensity has been measured with a wide wavelength photo-detector. The output intensity measured in voltage is found to be linearly dependent on the refractive indices surrounding the etched portion of the fiber. The result shows that the tapered single mode optical fiber is sensitive to refractive index of liquid at short (1 meter) as well as long (1.8 km) length of optical fiber. It also reveals that a distant detection and sensing can be carried out by a single mode tapered fiber sensors.

018195   Joseph L;Anuradha R;Kulkarni D B;Shaha V V (NO, Bhabha Atomic Research Centre, Mumbai-400 085, Email: leena@barc.gov.in) : Standardization of silver-110m at BARC, India. MAPAN 2007, 22(4), 225-9.

Radioactive solution of ^110mAg was standardized using the 4πβ-γ??coincidence method by efficiency extrapolation and using a calibrated high-pressure gamma ion chamber. This radionuclide is a β-γ emitter with a very complex decay scheme. The activity concentrations obtained by the coincidence method and secondary method on reference date of May 15, 2005 are 208.28(0.96) kBq/g and 209.04(2.72) kBq/g respectively and are in good agreement within the quoted uncertainty limits. The results have also been confirmed by participating in the International Reference System (SIR) of BIPM. Detailed uncertainty budget for both the methods are also included.

4 illus, 1 table, 11 ref

018194   Hsu S M (Mechanical and Aerospace Engineering Dep, George Washington University, ) : Nanometrology: an issue of scale. MAPAN 2007, 22(3), 201-7.

Advent of nanotechnology promises unprecedented economic and technological growth. As the length scale shrinks, measurement precision at ever smaller scales becomes a critical issue in ensuring the metrological accuracy and precision to fulfill the aspirations of nanotechnology. However, the precision and accuracy of nanoscale measurements are limited by instrumentation capabilities and the laws of physics. Describes the four aspects of Nanometrology: dimensional metrology, image metrology, force metrology, and materials metrology.

5 illus, 25 ref

018193   Gunasekaran S;Uthra D (Spectrophysics Research Lab, Pachaiyappa's College, Chennai-600 030, Email: uthra_13@yahoo.com) : Fourier transform infrared and Fourier transform Raman spectra and normal coordinate analysis of ethyleneimine. Indian J pure appl Phys 2008, 46(2), 100-5.

Ethyleneimine (C₂H₅N) also known as dimethyleneimine, azirane, aziridine is a toxic chemical that finds variety of uses in industries. It is volatile, highly reactive, corrosive and is considered as a potential carcinogen, but widely used in the paper, lacquer and photography industries. This molecule has eighteen fundamental modes of vibration under Cs point group distributed as Γ_vib = 10A' + 8A''. In the present paper, normal coordinate analysis has been carried out for the molecule ethyleneimine with an orthonormal set of symmetry coordinates by using Wilson's F-G matrix method. A satisfactory vibrational band assignment has been made in terms of normal modes of vibration using Fourier transform infrared and Fourier transform Raman spectroscopy. A reasonable set of potential constants was evaluated and found to be in good agreement with literature. The potential energy distribution has been evaluated which confirms the frequency assignment done, thus, providing a strong support to the present work.

018192   Ghosh D;Deb A;Pal S;Ghosh J (Nuclear and Particle Physics Research Centre, Physics Dep, Jadavpur University, Kolkata-700 032) : Self-affine multiplicity fluctuation of grey tracks in π<. Indian J pure appl Phys 2008, 46(2), 93-9.

Fluctuation characteristics of protons produced in π^--AgBr interactions at 350 GeV/c have been investigated in cosθ, φ and X_cosθ-X_φ phase spaces. Xcosθ and Xφ Factorial moment methodology has been used for the analysis. In two-dimensional analysis, fluctuation characteristics have been studied both in self-similar and self-affine space. No scaling behaviour is observed in the full bin-range. For in-depth study, full bin range is divided into different sub-bins. Fluctuation analysis into different sub-bins confirms the scaling law in a particular bin only. The analysis provides an indication of self-affine fluctuation pattern in this bin. X_cosθ and X_φ.

018191   Gaur M S;Ramlal;Shukla P;Saxena P;Tiwari R K (Physics Dep, Hindustan College of Science and Technology, Farah (Mathura) U P, Email: mulayamgaur@rediffmail.com ) : Thermally stimulated discharge current and fractional polarization studies in polyimide (Kapton-H) samples. Indian J pure appl Phys 2008, 46(2), 118-22.

In order to understand the relaxation processes responsible for thermally charged polyimide (PI) samples, the thermally stimulated discharge currents (TSDC) and fractional polarization thermally stimulated discharge current (FPTSDC) have been recorded. FPTSDC study is found to be having dipolar as well as space charge relaxation. The appearance of the second peak (i.e. β peak) at different poling field indicated that this peak is attributed to dipolar relaxation in polyimide. The peak position and activation energy do not change with the poling field (V_p), but it is very sensitive to the poling temperature (T_p). The magnitude of peak current has been found to vary with poling field and temperature. The poling field seems to change the reorientation of dipoles associated with β peak. The γ (first peak) and β (second peak) peaks were attributed to the motion of the side chain and the dipole-orientation associated with the residual reactive groups, respectively. The α peak (third peak) may be due to the space charge polarization or due to charge injected from the electrode. The activation energy and charge released have been found to vary with the poling field, poling temperature and poling time for this peak. FPTSDC spectra are showing two peaks which correspond to dipolar and space charge relaxation , respectively and are in good agreement with TSDC.

018190   De P (Physics Dep, Gobardanga Hindu College, University of Calcutta, P O Khantura-743 273, Email: pdeghc@yahoo.co.in) : Effect of substrate-epitaxy interface doping profile on the series resistance and mm wave performance of Si IMPATT diode. Indian J pure appl Phys 2008, 46(1), 33-7.

The effect of abrupt and exponential type of doping profiles in the transition region of epitaxy-substrate interfaces (nn⁺⁺ and pp⁺⁺) on the parasitic resistance and mm wave properties of double drift region low-high-low (n⁺⁺nn⁺npp⁺pp⁺⁺) Si IMPATT diode suitable for 35 GHz window frequency have been simulated. The results show that the negligible width of the nn⁺⁺ (0.016 μm) and pp⁺⁺ (0.015 μm) substrate-epitaxy interface regions over the total depletion layer width of 2.0 μm with realistic exponential doping gradient rather than its hypothetical abrupt nature, severely degrade the maximum avalanche region breakdown field at the junction, negative resistance, negative conductance as well as the power conversion efficiency; in other way increasing simultaneously the value of drift region electric field, punch through condition and the series resistance of the diode.

018189   Caravaggio M;Beciet G M M;Maria P D (NO, Dott. Ing. SCANDURA & FEM S.r.l., , Email: caravaggio@scandura.it ) : Pressure balances for industrial applications up to 120 MPa. MAPAN 2007, 22(4), 231-4.

Design and development of a series of pressure balances, operating in liquid media up to 120 MPa and in gas media up to 12 MPa, have been started during a recent collaboration between the Italian company SCANDURA & FEM and the I.N.RI.M (Italian National Research Institute of Metrology) in Italy. The details of the project design for the pressure balance in liquid media up to 120 MPa are presented here. The chosen strategy has been decided in such a way to produce a compact pressure balance easy to move, but at the same time equipped with all the measuring sensors needed to compensate the errors due to the main influence quantities. The main metrological characteristics of some pistoncylinder units were experimentally carried out and some interesting results are presented here.

3 illus, 3 ref

018188   Calla O P N;Mishra S K;Bohra D;Khandelwal N; Kalla P;Sharma C;Gathania N;Bohra N;Shukla S (NO, International Centre for Radio Science, Jodhpur) : Design a tunable cavity resonator for complex permittivity measurement of low-loss material at L band. Indian J pure appl Phys 2008, 46(2), 134-8.

The value of loss tangent (tanδ) of the low loss material is of the order of 10^-4. There are different methods used to measure loss tangent as well as complex permittivity. Out of different methods, Cavity Resonator method is the best method for the measurement of complex permittivity of low loss materials i.e. teflon, duroid, polystyrene and stycast. In this present paper, a cylindrical cavity resonator is designed and fabricated in the frequency range 2.2-2.3 GHz and the complex permittivity of low loss material teflon using cavity resonator method has been measured.

018187   Baral K C;Nath G (Physics Dep, Salipur College, Salipur, Cuttack-754 202) : Diffusion and transport phenomena in a collisional magnetoplasma with temperature anisotropy. Indian J pure appl Phys 2008, 46(2), 111-7.

The theory of collisional cross field diffusion and transport of a fully ionised singly charged plasma particles is analysed theoretically at the onset of an induced anisotropy (T_II≠T_⊥) in plasma temperatures where T_II and T_⊥ represent the components of temperature along the magnetic field direction and the direction perpendicular to it, respectively. The modified diffusion transport coefficients like the electrical resisitivity (η_⊥ ) and thermal conductivity (K) are found to decrease significantly with increase in the thermal ratio (T_II/T_⊥) while both the ExB drift velocity and the thermoelectric coefficient (λ) remain independent of the thermal anisotropy. However, in the limiting approximation (T_II=T_⊥), the results agree with the early isotropic works of Rosenbluth and Kaufmann, Phys Rev, 1 (1958) 109, Goldstone and Rutherford [IOP Publishing 1995, Braginskil (1965)].

018186   Balachandran S;Rudramoorthy R (School of Energy, PSG Coll of Technol, Coimbatore-641 004) : Thermal energy efficiency improvements in knitwear industry in Tirupur of India. J Text Ass 2007, 68(3), 124-31.

Study report quantifies savings that can be achieved by changes in operational procedures, as well as by using more energy efficient equipment, concluding that more efficient use of energy can not only cut costs but also help address environmental concerns.

3 illus, 7 tables, 6 ref

018185   Bahng G W;Cho S J;Lee H M (NO, Korea Research Institute of Standards and Science (KRISS), POB. 102 Yuseong, Daejeon 305-600, Republic of Korea, Email: gwbahng@mail.kriss.re.kr) : Technical approach to establish traceability in materials in materials metrology. MAPAN 2007, 22(3), 145-51.

Materials metrology is becoming an increasingly important international issue as the world economy moves into global system. To reduce technical barrier on trade through providing equivalency among NMIs, CIPM has arranged the MRA in 1998. To make this arrangement effective, establishment of traceability system is necessary as is required by ISO 17025. However, this is not an easy task for materials metrology because materials properties are commonly procedure-dependent. Because of this characteristic, it is not as straightforward as in physical measurement. In fact, both reference procedure and reference material are very essential components to establish traceability chain in materials metrology. Ttechnical approach to establish a traceability chain in materials metrology is discussed with an example of hardness measurement.

5 illus, 1 table, 6 ref

018184   Arif Sanjid M;Chaudhary K P;Singhal R P (NO, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi-110 012, Email: sanjid@mail.nplindia.ernet.in) : Feasible method to validate measurement software FLaP used in automatic gauge block interferometer to enforce ISO/IEC 17025:2005. MAPAN 2007, 22(4), 247-55 .

In the field of industrial engineering and dimensional metrology, gauge blocks occupy highest position in hierarchy for realization of length. National Physical Laboratory, New Delhi, India (NPLI) calibrates reference grade gauge blocks ranging in size from 0.5 mm to 300 mm against stabilized red and green laser radiations using an automatic gauge block interferometer, model: GBI-300. A measurement software FLaP programmed by the manufacturer of GBI-300 is used to evaluate length of gauge blocks. As per stipulation in ISO/IEC 17025, the instrumentation of GBI-300 is to be calibrated. The validation of measurement software FLaP used is also essential. NPLI has developed two measurement software programs as per FLaP algorithm. The results produced by NPLI developed software programs and FLaP are compared for a set of gauge block measurement data. In order to validate the measurement software program FLaP, a mathematical model is proposed to quantify similarity of the results thus produced.

1 illus, 3 tables, 6 ref

017147   Yadav B S;Israt Ali;Pradeep Kumar;Yadav P (Molecular Spectroscopy and Biophysics Laboratory, Physics Dep, D N (PG) College, Meerut-250 002, , Email: israt_tomar@yahoo.com) : FTIR and laser Raman spectra of 2-hydroxy-5 - methyl-3-nitro pyridine. Indian J pure appl Phys 2007, 45(12), 979-83.

The FTIR and laser Raman spectra of 2-hydroxy-5-methyl-3-nitro pyridine have been recorded in the region 4000-400cm^-1 and 4000-50cm^-1, respectively. Both the spectra have been analyzed on the basis of Cs point group symmetry and the observed bands have been assigned to the different specific modes of vibrations. The assignments of FTIR and laser Raman bands of said molecule are made on the basis of magnitude and relative intensities of the observed bands. The assignments made for the complex molecule under investigation are in good agreement with the earlier work on some pyridine derivatives.

017146   Verma H C (Physics Dep, Indian Institute of Technology Kanpur, Kanpur-208 016, Email: hcverma@iitk.ac.in) : Mossbauer studies of CuFe-72% alloy. Indian J pure appl Phys 2007, 45(10), 851-5.

Cu-Fe alloy with 72 at % of iron in powder form is prepared using simultaneous electrodeposition from a common electrolytic bath. Mossbauer spectra of the as-prepared sample show a superposition of quadrupole doublet with a large line broadening and a small component of a six line Mossbauer spectrum which has been characterized to be pure iron phase. As the samples are annealed, more and more segregation of magnetic part takes place. The linewidth and the quadrupole splitting of the residual doublet change in a correlated fashion and go through a maximum at 300°C. The crucial factor responsible for line broadening seems to be defect distribution and oxygen/hydrogen incorporation during electrodeposition and alloying. The phase-segregated iron on heating is in oxidized form (hematite and magnetite) most probably due to reaction with oxygen incorporated at the time of deposition.

017145   Venugopalan K (Physics Dep, Mohanlal Sukhadia University, Udaipur-313 001, Email: venu@mlsu.org) : Hyperfine interactions in Heusler systems. Indian J pure appl Phys 2007, 45(10), 783-9.

Recently, there has been a new surge of interest in Heusler alloys because of possible use of these alloys as materials for spin electronic devices. Heusler alloys also offer excellent systems for studying magnetic interactions. These alloys can be held at various degrees of order and also allow systematic substitution of one or more of the constituents. The magnetic and transport properties of these alloys can, therefore, be modified through such methods. Hyperfine interactions studies in a disordered Heusler system Fe2CrAl using Mossbauer spectroscopy, have been presented. The disorder present in the system is reflected in the X-ray diffraction and M”ssbauer spectra. The system behaves like a normal ferromagnet even in the presence of disorders.

017144   Veerabhadra Rao A;Srinivasa Reddy M;Ravi Kumar V;Veeraiah N (Physics Dep, Acharya Nagarjuna University PG Centre, Nuzvid 521 201, Email: nvr8@rediffmail.com) : Dielectric dispersion in PbO-PbF₂-B₂O₃ glass system doped with Cr₂O₃. Indian J pure appl Phys 2007, 45(11), 926-34.

PbO-PbF₂-B₂O₃ glasses containing different concentrations of chromium ions (introduced as Cr₂O₃) ranging from 0 to 0.4 mol % were prepared. The dielectric properties i.e., constant ε', loss tanδ, ac conductivity σ_ac over a range of frequency and temperature of Pb glasses have been carried out. The results have been analyzed in the light of different oxidation states of chromium ions with aid of the data on differential scanning calorimetry, infrared, optical absorption and ESR spectra. The analysis indicates that when the concentration of chromium ions is up to <126> 0.3 mol %, these ions mostly exist in Cr³⁺ state, occupy network-modifying positions with CrO₆ structural units and at about 0.4 mol % a part of chromium ions seems to exist in Cr⁶⁺ state, adopting network forming positions with CrO₄^2- structural units and causing an increase in the insulating strength of the glass.

017143   Vaidyanathan G;Sekar R;Hemlatha R (Physics Dep, Pondicherry Engineering college, Pondicherry 605 014, Email: gvn_pec@yahoo.com) : Effect of coriolis force on soret driven ferrothermohaline convection in a medium of sparse particle suspension. Indian J pure appl Phys 2007, 45(8), 666-73.

In ferrofluids three components namely core, surfactant and carrier fluids coexist. Thermal convection in a multicomponent fluid has wide applications in industrial, ionospheric and geothermal systems. The effect of magnetic fields along the vertical axis on a soret driven thermohaline convective instability in a ferrofluid saturating rotating porous medium has been examined using linear stability analysis. The infinitely spread fluid layer is assumed to be contained in between two free flat conducting boundaries. The exact solutions for stationary and oscillatory instabilities are obtained. It is found that the stationary instability is possible for Taylor numbers up to 100. When the values of Taylor number are greater than 100, the system is found to stabilize through oscillatory mode. The calculations made on this study are shown graphically.

017142   Usha Chandra (High Pressure Physics Lab, Physics Dep, University of Rajasthan, Jaipur-302 004, Email: ushac_jp1@sancharnet.in) : High pressure Mossbauer spectroscopy. Indian J pure appl Phys 2007, 45(10), 790-4.

Pressure induces myriad changes in materials by bringing order/ disorder, by changing electronic hybridization and by inducing chemical reactions. High-pressure Mossbauer spectroscopy using Diamond Anvil Cell, a well recognized tool to investigate various types of phase transitions in materials, has been studied.

017141   Upadhyaya S B;Kant K;Joshi R;Sonkawade R G; Chakarvarti S K;Sharma G S (Physics Dep, B S A College, Mathura, Uttar Pradesh) : Radon-thoron and their progeny dosimetry in the environment of LPG bottling plant using plastic track detectors. Indian J pure appl Phys 2007, 45(11), 880-3.

The inhalation dose rates and annual effective dose contribution from the mixed field of radon and thoron present in the environment of LPG bottling plant were measured, as it is very much essential from health and hygiene point of view of the workers in the plant. The radon and thoron concentration and the inhalation dose were found to vary from 7.78±2.02 to 59.01±5.57 Bq/m³, 1.16±0.28 to 65.08±5.09 Bq/m³ and 0.23 to 2.29 mSv/y, respectively. The concentration of radon daughters was found to vary from 0.84 to 6.38 mWL, the concentration of thoron daughters from 0.03 to 1.76 mWL, the annual exposure due to radon and thoron daughters, collectively, from 0.036 to 0.273 WLM, the life time fatality risk from 0.11 x10^-4 to 0.82 x10^-4 and the annual effective dose from radon and thoron (PAEC) from 0.14 to 1.06 mSv/y.

017140   Tiwari R P;Thakur S N;Singh R A (Physics Dep, Banaras Hindu University, Varanasi-221 005, Email: rasinzh@yahoo.co.uk ) : High resolution electronic absorption spectrum of 1, 3, 5-trifluorobenzene. Indian J pure appl Phys 2007, 45(7), 569-72.

The near ultraviolet electronic absorption spectrum of 1,3,5 trifluorobenzene has been photographed on a 10.6 m concave grating spectrograph. The electronic forbidden transition ¹A'₂ ← ¹A'₁ is explained as arising due to perturbation of the electronic state by non-totally symmetric vibration v₆. Besides v₆ , the other modes of e' species v₈, v₉, v₁₈, and v₁₉ are also active and give rise to false origins. The vibrational frequencies for v₉, v₁₈, v₁₉, v₈, v₁₃, v₁ and v₁₆ modes in the first electronic excited state ¹A'₂ are reported for the first time.

017139   Thomas P C;Aruna S;Madhavan J;Ittyachan R; Pragasam J A;Jesudurai J G M;Prabha K;Sagayaraj P (Physics Dep, Bharathi Women's College, North Chennai-600 108) : Growth and thermal studies of non-linear optical L-argininium diiodate L-argininium dinitrate and L-argininium hydrochloride bromide single crystals. Indian J pure appl Phys 2007, 45(7), 591-5.

Single crystals of L-argininium diiodate (LADI), L-argininium dinitrate (LADN) and L-argininium hydrochloride bromide (LAHClBr) were grown by slow solvent evaporation technique at room temperature. The grown crystals were characterized by X-ray diffraction, Differential Thermal Analysis (DTA), Thermogravimetric analysis (TGA) and Differential Scanning calorimetry (DSC). LADI crystallizes in the orthorhombic system, with space group P212121 . The XRD data prove that both LADN and LAHClBr crystals are monoclinic in structure with P21 space group. LADN is found to be thermally more stable than LADI and LAHClBr crystals.

017138   Thakor P B;Gajjar P N;Jani A R (Physics Dep, Veer Narmad South Gujarat University, Udhna Magdalla Road, Surat-395 007) : Structural study of some d shell liquid metals. Indian J pure appl Phys 2007, 45(6), 509-13.

The Charged Hard Sphere (CHS) reference system is applied to study the structure of some d shell liquid metals viz; Sc, Zr, Pd, La and Pt. The structure factor S(q), pair distribution function g(r), inter atomic distance r₁ and coordination number n1 are calculated using a well established pseudopotential. The latest local field correction function (S) due to Sarkar et al. (Ref. 18) is applied to introduce the exchange and correlation effects. It is found that the present results are in good agreement with experimental data. Thus the CHS reference system alongwith the present model potential is found capable of explaining the structural information of some d shell liquid metals.

017137   Tahir M;Bhattacharya K;Ghosh A;Chakraborty A K (Applied Optics and Photonics Dep, Calcutta Univ, 92, Acharya Prafulla Chandra Road, Calcutta-700 009) : Simulation of the effects of phase and amplitude coatings of lens aperture using a retarder as a zonal mask. J Optics 2007, 36(3), 123-35.

Modification of imaging properties of lens using phase and amplitude coatings on the lens aperture is well known. The fact that the use of polarization masks on lens aperture also modifies the imaging properties of a lens is pretty well established. Seidel aberrations of a lens can also be reduced by using proper zonal polarization masks. In this paper we have studied the effects of a retarder used as a zonal mask on the aperture of a diffraction-limited lens on tis imaging properties. It is shown that changes in the retardance and the orientation of the retarder can simulate the effects of phase and amplitude coating on the lens aperture on the imaging characteristics of the lens.

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017136   Swati D (Physics Dep, MMV, Banaras Hindu Univ, Varanasi-221 005, Email: swati@bhu.ac.in) : In silico comparison of bacterial strains using mutual information. J Biosci, Bangalore 2007, 32(6), 1169-84.

Fast-sequencing throughput methods have increased the number of completely sequenced bacterial genomes to about 400 by December 2006, with the number increasing rapidly. These include several strains. In silico methods of comparative genomics are of use in categorizing and phylogenetically sorting these bacteria. Various word-based tools have been used for quantifying the similarities and differences between entire genomes. The simple di-nucleotide frequency comparison, codon specificity and k-mer repeat-detection are among some of the well-known methods. Mutual Information function, which is a measure of correlations and a concept from Information Theory, is very effective in determining the similarities and differences among genome sequences of various strains of bacteria such as the plant pathogen Xylella fastidiosa, marine Cyanobacteria Prochlorococcus marinus or animal and human pathogens such as species of Ehrlichia and Legionella. The short-range three-base periodicity, small sequence repeats and long-range correlations taken together constitute a genome signature that can be used as a technique for identifying new bacterial strains with the help of strains already catalogued in the database. There have been several applications of using the Mutual Information function as a measure of correlations in genomics but this is the first whole genome analysis done to detect strain similarities and differences.

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