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    Wyświetlanie 1-6 z 6
    Tytuł:
    Evidence of Formation of $Co_{x}Cu_{1-x}$ Nanoparticles with Core-Shell Structure
    Autorzy:
    Dhara, S.
    Chowdhury, R.
    Bandyopadhyay, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402071.pdf
    Data publikacji:
    2015-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.75.Fk
    61.05.cp
    75.60.-d
    Opis:
    We have prepared $Co_{x}Cu_{1-x}$ granular alloys with Co contents (x ≈ 0.01-0.30) by chemical reduction. Samples are characterized by X-ray diffraction and transmission electron microscopy yielding particles of mean diameter 8-20 nm formed in fcc phase. The branching in ZFC/FC magnetization behavior confirm superparamagnetism in the samples, characterized by blocking temperature distributions which represent variations in particle size and inhomogeneities of their chemical compositions. Magnetic field dependence of magnetization show hysteresis loops, and the magnetization at any temperature 4-300 K is a combination of ferromagnetism and superparamagnetism. The saturation moment of Co for the ferromagnetism part increases with the Co content. But the coercive fields $(H_{C})$ and magnetic anisotropy of the particles do not vary with Co concentration. Annealed samples exhibit exchange bias in the range 20-150 Oe at 4 K. The results indicate formation of nanoparticles of CoCu alloy in a core-shell type structure with Co being concentrated near the core.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 4; 533-535
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Vanadium Substitution of Cobalt in $NdCo_2Si_2$
    Autorzy:
    Chowdhury, R.
    Dhara, S.
    Bandyopadhyay, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402070.pdf
    Data publikacji:
    2015-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.20.Lp
    75.50.Gg
    75.50.Ee
    75.50.Cc
    75.50.Dd
    Opis:
    In NdCo₂Si₂, partial substitution of Co by V having a larger atomic radius results in negative pressure affecting the magnetic properties of the compound. The samples $Nd(Co_{1-x}V_{x})_Si_2$ (x=0, 0.20, 0.35) have been prepared and characterized using X-ray diffraction. The parent compound NdCo₂Si₂ is antiferromagnetic with $T_{N}$ of 34 K whereas the temperature dependence of inverse susceptibility in the doped samples show ferrimagnetic behaviour below 45 K. From the magnetic field dependence of magnetization and the coercive fields obtained from hysteresis loops, the doped samples exhibit ferromagnetism below ≈ 20 K. The specific heat studies compare the magnetic transitions in the parent and doped samples. $Nd(Co_{0.65}V_{0.35})_2Si_2$ shows a magnetoresistance of 15% at 4 K.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 4; 530-532
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Assessment of bird diversity as bioindicators in two parks, Kolkata, India
    Autorzy:
    Chowdhury, R.
    Sarkar, S.
    Nandy, A.
    Talapatra, S.N.
    Powiązania:
    https://bibliotekanauki.pl/articles/11495.pdf
    Data publikacji:
    2014
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    assessment
    bird diversity
    bioindicator
    vehicular traffic
    vehicular pollution
    urban park
    biomonitoring
    landscape change
    park
    Calcutta city
    India
    Opis:
    The trees of parks and gardens support many species, the survival of urban-dwelling species mainly bird species. Birds amongst other species provide a wide range of environmental and social functions to cities and urban dwellers. The present study aims to know bird diversity in two parks as bioindicator of automobile air pollution exposure, landscape changes and/or human interactions. The study areas were selected as per heavily-populated neighborhoods, nearby office buildings, nearby roads and continuous vehicular movements, human interactions as visitors, where high levels of human disturbance are common. The study was carried out at 2 sampling stations viz (i) Elliot park and (ii) Agri-horticulture Society. The bird species diversity was studied by qualitative and quantitative assessment. Indices were Species richness, Index of Dominance, Relative abundance, Shannon-Wiener Diversity Index and Evenness Index for birds for all selected sites were calculated using the statistical formulae. The present results as bioindicators bird species clearly indicate that the bird species are very few in numbers in both the parks. When comparison made between both the parks, it was observed less number of bird varieties (16 types) in Elliot park than varieties (9 types) more less in number in Agri-horticulture society. This study is a preliminary assessment of bird diversity but further researches are needed in relation to biochemical and genetic damage study as well as air pollution load by using instruments. In the present study it was concluded that the less numbers of birds and their different diversity indices were found a decreasing trends, though there no attempt has been made on physico-chemical properties of present air pollutants. The less number of varieties of bird species are as tolerant bioindicators, which may be due to the vehicular pollution and/or human interference and/or landscape changes due to nearby neighborhood blocks, office and residential buildings, continuous movement of vehicles etc.
    Źródło:
    International Letters of Natural Sciences; 2014, 11, 2
    2300-9675
    Pojawia się w:
    International Letters of Natural Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Coupled Nonlinear System in (2+1) Dimension and Overturning Solitons
    Autorzy:
    Ghosh, C.
    Chowdhury, A. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1945350.pdf
    Data publikacji:
    1996-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    02.90.+p
    52.35.Nx
    52.35.Sb
    Opis:
    Coupled nonlinear integrable systems in (2+1) dimension are generated from a matrix Schrodinger-type inverse problem and solved explicitly to demonstrate a new phenomenon of overturning. Both, the two- and three-dimensional graphical depictions of the solution are presented. Our analysis is an extension of the uncoupled case reported earlier by Bogoyavlenskii. A unique feature of the solution is the occurrence of arbitrary functions of (y, t) in its functional form, which significantly changes the behaviour of the solution.
    Źródło:
    Acta Physica Polonica A; 1996, 89, 4; 459-466
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On Darboux-Bäcklund Transformation and Positon Type Solution of Coupled Nonlinear Optical Waves
    Autorzy:
    Sen, D. C.
    Chowdhury, A. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2014041.pdf
    Data publikacji:
    2000-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    02.30.+g
    52.35.Mw
    52.35.Sb
    Opis:
    A Darboux-Bäcklund transformation is used to obtain a positon type solution of the nonlinear equations describing the propagation of coupled nonlinear optical pulses.This form of the positon solution is then compared with that obtained by the special limiting procedure applied to a two-soliton solution. It is observed that though the algebraic form of the two solutions is different yet both of these have singularities and the position of the singularities remains on the similar curve in the (x,t) plane. We also depict the form of these solutions graphically. Finally, it may be added that the method of Darboux-Bäcklund transformation is convenient for generating more than one-positon solution.
    Źródło:
    Acta Physica Polonica A; 2000, 98, 1-2; 3-10
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Measurement of radioactive impact of the gas well accident on environment of Sylhet division in Bangladesh
    Autorzy:
    Chakraborty, S. R.
    Saha, K. K.
    Rahman, A. K. M. R.
    Kamal, M.
    Chowdhury, M. I.
    Alam, Md. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/411611.pdf
    Data publikacji:
    2013
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Natural gas well accident
    Environmental radioactivity
    Public exposure etc
    Opis:
    The main goal of this study is to carry out the public exposure contribution from radioactive materials occurring due to the accident of natural gas exploration well of Sylhet division in Bangladesh. This study has been performed by using a gamma spectrometry of Genie 2000 software embedded PC-based High Purity Germanium (HPGe) detector system. The measured activity concentrations of naturally occurring radionuclides 232Th, 226Ra, and 40K have been in the public safety limit on the environment of the study areas. The specific activity of detected anthropogenic radionuclide 137Cs has been found to be very little with a mean value of 1.65 ± 0.61 and 1.13 ± 0.57 Bq•kg–1 in the Magurchhera and Haripur gas field area respectively.
    Źródło:
    International Letters of Chemistry, Physics and Astronomy; 2013, 9, 1; 48-60
    2299-3843
    Pojawia się w:
    International Letters of Chemistry, Physics and Astronomy
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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