http://nopr.niscair.res.in/handle/123456789/8224 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8358 Title: Development of an experimental arrangement for precise measurement of angular distribution of ultrasound scattering <br/> <br/>Authors: Saha, Ratan K; Roy, Manas K; Karmakar, Subhajit; Saha, Saibal; Sen, Swapan K <br/> <br/>Abstract: This paper describes step-by-step development of a custom-made measurement system and also provides an assessment of the reliability of the set-up. The angular distribution of the scattered field generated by a sufficiently long cylindrical scatterer in water medium has been measured by this system. The measured values have been compared with the theoretical results to validate the instrument. The theoretical curves have been obtained by using the Faran’s theory [<i style="">J Acoust Society of</i> <i style="">America</i>, 23(4) (1951) 405]. In this study, an acoustic wave of frequency 2.19 MHz emitted by a medical ultrasound source has been employed to provide energy to the scattering object. Two steel wires of different gauges (0.68mm and 0.91mm in diameter) with size parameters k<i style=""><img src='/image/spc_char/alpha.gif' border=0> </i> ≈ 3.12 and 4.17, respectively, have been taken as prototype scatterers. Here, k is the wave number of the incident wave and <i style=""><img src='/image/spc_char/alpha.gif' border=0> </i> is the radius of the target. Our results show that the system is stable, capable of precise scattering measurements and measured values are reproducible. The system has also the flexibility of incorporating scatters of different shapes and also ultrasound probes of different frequencies. <br/> <br/>Page(s): 661-669 Tue, 29 Aug 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8357 Title: Study of ion and electron beam irradiation effects in Al-Sb bilayer thin films <br/> <br/>Authors: Mangal, R K; Singh, M; Vijay, Y K; Avasthi, D K <br/> <br/>Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> Thin films having uniform thicknesses of aluminium over different thicknesses of antimony were prepared by thermal evaporation (resistive heating) method at the pressure 10^-5torr. The samples were irradiated by Ag¹²⁺heavy ions of energy 160 Mev at the fluence 2.2<img src='/image/spc_char/cross.gif' border=0>10¹³ ions/cm². The similar set of these films have also been irradiated by electron beam having energy 10 keV for two hours. The optical absorption spectra and Rutherford back scattering analysis have been carried out for these films. X-ray diffraction spectra of virgin as well as ion irradiated sample, show orthorhombic structure of the films. These results show that the inter diffusion of bilayer with irradiation effects. It is also suggested that ion beam irradiation gives the better results in comparison to electron beam. These results confirm the mixing of Al/Sb bilayer by irradiation process. </smarttagtype> <br/> <br/>Page(s): 685-689 Tue, 29 Aug 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8356 Title: Role of inter-site hybrid interactions in itinerant ferromagnetism <br/> <br/>Authors: Dua, Piyush; Panwar, Sunil; Singh, Ishwar <br/> <br/>Abstract: The role of inter-site hybrid interactions in deciding ferromagnetic state in the itinerant electron (narrow band) systems like some of the transition metals has been studied. We have considered Hubbard like tight binding model alongwith exchange and hybrid interactions. All interactions have been treated within mean-field approximation. It is found that hybrid interactions play significant role at zero as well as finite temperatures in deciding on-set of ferromagnetic state. The variation of effective mass of up and down spin electrons in ferromagnetic state as a function of temperature has been studied. The magnetic susceptibility, optical conductivity and magnetoresistance as a function of temperature have also been studied. <br/> <br/>Page(s): 677-684 Tue, 29 Aug 2006 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8355 Title: Vibrational spectra and thermodynamics of biomolecule: 5-chlorocytosine <br/> <br/>Authors: Rastogi, V K; Palafox, M A; Lang, Kamil; Singhal, S K; Soni, R K; Sharma, Rekha <br/> <br/>Abstract: The laser Raman and IR spectra of biomolecule 5-chlorocytosine have been recorded in solid phase. The vibrational spectra have been analysed assuming planar geometry and C_s point group symmetry for the molecule and observed fundamentals have been assigned to different normal modes of vibrations. The studies indicate that the features that are characteristic of the vibrational spectra of cytosine and its derivatives are retained by the spectrum of 5-chlorocytosine and it exists in amino-oxo form in solid phase. The validity of empirical relation ν_s = 345.5 + 0.876 ν_asym suggests the equivalence of the two NH bonds of the NH₂ group. The observed fundamental frequencies are used to calculate the thermodynamic functions, namely, the enthalpy, entropy, heat capacity and the free energy were also computed in the temperature range 200-1000K using the rigid-rotor harmonic oscillator approximation. For this purpose, the fundamental wavenumbers obtained in the present study were taken, while the structural parameters were taken from literature. <br/> <br/>Page(s): 653-660 Tue, 29 Aug 2006 22:58:59 GMT