IOSR-JAP   Volume-6 ~ Issue-4 ~ July-August 2014

ABSTRACT: Pure ZnS nanoparticles, MnS/ZnS and PbS/ZnS core/shell nanostructures are prepared by simple chemical method. UV studies reveal that the optical band gap increases for the samples in which the core with a small band gap is surrounded by the shell having a large band gap. There is a blue shift observed in all the samples. Comparing with the pure ZnS nanoparticles, MnS/ZnS and PbS/ZnS core/shell nanostructures, PL studies show that there is slightly enhanced blue emission and an additional green emission.
Subject classification: PACS: 61.46.-w,78.67.-n,81.07.-b,81.07.Wx.

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ABSTRACT: In the present report preliminary studies on synthesis and growth of ZnO nanocrystals have been reported. ZnO precursors were prepared by precipitation method from Zinc nitrate and Ammonia in aqueous solutions at a pH value9.0 .ZnO nanocrystals were then synthesized by heating the precursor in a muffle furnace at temp 350°C for 3 hours and allowed to cool to room temperature. The precursors and synthesized nanoparticles were characterized by X-Ray diffraction (XRD) and the results showed a single phase wurtzite structure for ZnO nanoparticles. It was found that the synthesized ZnO nanocrystals have wurtzite structures with a=b=3.214 Å and c=5.154 Å. Crystallite size was calculated using Debye_Scherrer's equation and the average crystallite size from first three peaks was found to be 55.18 nm. The morphology of prepared ZnO nanopowders was characterized by scanning electron microscope (SEM). From the compositional analysis by Energy dispersive analysis of X-ray (EDX) it was confirmed that Zinc and oxygen are present in the sample. Optical characterization was done to study other characters. Diffuse reflectance spectroscopy (DRS) results shows that the band gap of ZnO nanoparticles is 3.20eV.

Keywords: ZnO, nanoparticles, precipitation, XRD, SEM, band gap

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ABSTRACT: In this paper we report our results on radon exhalation rate of soil as well as indoor radon concentration of a few places of Karbi Anglong District of Assam. The technique of passive method has been adopted using LR-115 (type-II) plastic detector. Significant variations in radon exhalation rate and indoor radon concentration have been observed for the studied locations. The minimum and maximum values of radon exhalation rate as found for the present investigation are 348.37±17.4 mBqm-2h-1 (10.52±0.52 mBqkg-1h-1) and1864.2±92.7 mBqm-2h-1(56.29±2.8 mBqkg-1h-1 ).For indoor radon concentration the minimum and maximum values as found from this study are 81.26±4.06 Bqm-3and 277.78±13.89 Bqm-3.

Keywords: Radon exhalation rate, Indoor radon concentration, LR-115, Plastic detector.

[1]. BARC Report (2003): No.BARC/2003/E/026, pp.1-43. Sen, M., Mishra, R., Tripathy, S. P., Sinha, D., Kulshreshtha, A., Dwivedi, K.K., Deka, P. C., and Bhattacharjee, B., (1998). J. Assam Sci. Sco., 39(3), 105- 116.
[2]. Dwivedi, K. K., Mishra, R., Tripathy, S. P., Kulshreshtha, A., Sinha, D., Srivastava, A., Deka, P., Bhattacharjee, B., Ramachandran, T.V.and Nambi, K.S.V., (2001). Radiation Measurement 33, 7-11.
[3]. Eappen,K.P., Mayya, Y.S., Calibration factors for LR-115(Type-II) based radon radon thoron discriminating dosimeter ,Vol.38, issue 1,(2004) ,Radiation Measurement pp.5-17.
[4]. Abu-Jarad F, 1988, Applications of nuclear track detectors for radon related measurements, Nuclear Track Radiation Measurement,15, 525
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ABSTRACT: ZnO and ZnO/CuO nanocomposite were successfully synthesized by Sol-Gel technique. The crystal structure was investigated by X- ray diffraction technique and the molecular structure was studied by Fourier transformation infrared. Atomic force microscopy was used to study the topological properties of the prepared thin films. The optical properties were studied and the optical band gap were evaluated from the x-axis intercepts at (αhυ)2=0 and found to be decreased from 3.27 to 3.26 eV as the dopant increased. ZnO and ZnO/CuO nanocomposite were used as interfacial layer on schottky diode. The technical parameters such as ideality factor and the barrier height were found to be increased from 3.7 to 6.5 and from 0.59 to 0.62 eV respectively as the dopant were increased. Keywords: ZnO; CuO; Composite; optical Properties; Schottky diode;

[1]. Seval Aksoy and Yasemin Caglar, Effect of ambient temperature on electrical properties of nanostructure n-ZnO/p-Si heterojunction diode, Superlattices and Microstructures, (51), 2012 ,613–625.
[2]. O. Lupana, Th. Pauportea, I.M. Tiginyanu, V.V. Ursaki, H. Heinrich and L. Chowc, Optical properties of ZnO nanowire arrays electrodeposited on n- and p-type Si(111): Effects of thermal annealing, Materials Science and Engineering B,(176), 2011, 1277– 1284.
[3]. H.E. Brown, J. Phys. Chem. Solids, (15), 1960, 86.
[4]. Seong Gook Cho, Tschang-Uh Nahm and Eun Kyu Kim, Deep level states and negative photoconductivity in n-ZnO/p-Si hetero-junction diodes, Current Applied Physics, ( 14), 2014, 223-226.
[5]. O. Lupan, T. Pauporte and B. Viana, Low-Voltage UV-Electroluminescence from ZnO-Nanowire Array/p-GaN Light-Emitting Diodes, Adv. Mater. (22), 2010, 3298–3302.

ABSTRACT: Cadmium doped nickel-cobalt ferrite with chemical formula Ni0.8-xCo0.2CdxFe2O4 (x=0.1, 0.2 and 0.3) is prepared by standard double sintering ceramic method. Electric and dielectric properties of nickel cobalt cadmium ferrite are investigated. Formation of single phase is confirmed by X-ray Diffraction pattern. The average grain size of the samples is determined by scanning electron micrographs. The D.C resistivity (ρ) is determined as a function of temperature in the range 300K-1073K by two probe method. Dielectric constant (έ) is determined by measuring capacitance (Cp). Variations of Dielectric constant (έ) with frequency as well as temperature are studied. A.C. conductivity (σac) is derived from dielectric constant (έ) and loss tangent (tan δ) values

Keywords: Dielectric properties. Electric properties, NiCoCd Ferrite, SEM, XRD.

[1] Andris Sutka, Rainer Parnab, Gundars Mezinskisa, Vambola Kisandb, Sensors and Actuators B 192 (2014) 173– 180.
[2] Anuj Jain, Ravi Kant Baranwal, Ajaya Bharti, Z. Vakil, and C. S. Prajapati, The Scientific World Journal ,Volume 2013, Article ID 790359, 7 pages.
[3] Ovidiu Caltun, Ioan Dumitru, Marcel Feder, Nicoleta Lupu, Horia Chiria, Journal of Magnetism and Magnetic Materials 320 (2008) e869–e873.
[4] R.K. Kotnala , Jyoti Shah, Bhikham Singh, Hari kishan, Sukhvir Singh, S.K. Dhawan, A. Sengupta, Sensors and Actuators B 129 (2008) 909–914.
[5] R.C. Kambale, P.A. Shaikh, S.S. Kamble, Y.D. Kolekar, Journal of Alloys and Compounds 478 (2009) 599–603.
[6] V.L. Mathe, R.B. Kamble, Materials Research Bulletin 43 (2008) 2160–2165

ABSTRACT: The knowledge of the conduction mechanisms in a Schottky barrier is essential to calculate the Schottky barrier parameters and to explain the observed effects. In the present work, we report temperature-dependent current-voltage characteristics of (Mo/Au)/Al0.26Ga0.74N/GaN/Si/ Schottky barrier diodes. Measurements were performed in the temperature range of 80 -300 K.Results have been explained based on the thermionic emission mechanism with lateral inhomogeneity at the (Mo/Au/AlGaN/GaN/Si) interface. As is shown, the barrier height ΦB0 as well as the ideality factor n exhibit an important temperature dependence and the anomaly resulting from this dependence has been explained by invoking two sets of Gaussian distributions at the metal/semiconductor interface for temperature ranging from 80 K to 160 K and from 160K to300 K, respectively. It is also found that the values of Rs obtained from Cheung's method strongly depend on temperature and decrease with decreasing temperature.

Keywords: Schottky barrier, Current–voltage characteristics, Ideality factor, Inhomogeneity, Thermionic emission.

[1]. H. Mosbahi, M. Gassoumi, I.Saidi, H.Mejri, C. Gaquière, M.A. Zaidi,H. Maaref. Current Applied Physics. 13, (2013) 1359.
[2]. F. Iucolano, F. Roccaforte, F. Giannazzo, V. Raineri, J. Appl. Phys. 104 (2008).
[3]. S. Arulkumaran, T. Egawa, H. Ishikawa, M. Umeno, T. Jimbo, IEEETrans. Electron Devices 48 (2001) 573e580.
[4]. I. Dokmee, S. Altindal, Semicond. Sci. Technol. 21 (2006) 1053.
[5]. A. Gumus, A. Trust, N. Yalcin, J. Appl. Phys. 91 (2002) 245.
[6]. P. Chattopadhyay, D.P. Haldar, Appl. Surf. Sci. 143 (1999) 287

ABSTRACT: Meterological data for thirty years (1980-2009) from three whether stations which are Bauchi Yola and Maiduguri were analyzed to determine the comfort and discomfort period using Temperature humidity indices and wind chill index. Monthly variation of THI was shown to be a mirror image of WCI. No cold, bitter cold episodes were recorded throughout the investigation. The months with heat stress are April, May, June, July, August, September and October while the remaining months which are January, February, March, November and December mostly bring comfortable sensation for all the states investigated except Yola which records heat stress in the month of March. Bauchi and Yola record severe heat stress in the month of April and May where 100% of man and animal are not comfortable due to hot and humid weather. Percentage frequencies of the annual THI and WCI for the thirty years observed were also reported.

Keywords: Temperature-Humidity Index, Wind-Chill Index, Heat stress, Percentage Frequency

[1]. Adeniyi, M. O. (2009). Determination of Heat Stress Index In The Tropical Urban Area Of Ibadan, Southwest Nigeria. International Journal Of Natural and Applied Sciences, 5(3): 235-243.
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ABSTRACT: Here in this article, the reader is made to think again on the universal saying, "Energy is constant in this universe." In the end of the article the reader will think twice about the energy content in a living organism. As it is said that the total energy in this universe is constant, at the end of the article the reader will try to think that the energy in living organisms is decreasing with time!!! Keywords: Energy, Life.

[1]. http://www.quanta-gaia.org/dobson/PhysicsOfIllusion.html
[2]. http://en.wikipedia.org/wiki/Life
[3]. http://hyperphysics.phy-astr.gsu.edu/hbase/biology/enercyc.html

ABSTRACT: Westudy the electroniclifetimesinmolecularjunctionsusingthe Keldyshnonequilibrium Green function (NEGF)model.It isfoundthattwocharacteristictime scaleswhichgovern theelectrontunneling phenomena. One is the electroniclifetime in whichelectronicenergy in the molecularelectronic state dissipatesinto the right/leftelectrode or vibrational mode,the otheris the residence time due to virtual excitationof electronsbetweenthe twoelectrodes and the molecularelectronic state.And using a set of the parameterswhichcharacterize the molecularjunction, we show that the molecularvibrationalfrequency, the position ofthe electronicstate of the molecule, the strength of electron-vibration coupling(via the electron-phonon interaction) and the distance between the molecule and the electrodes(via the molecule-electrodecoupling)representsubstantial contributions that affect the electroniclifetime in molecularjunctions, as result all are represent important parameters to determine the nature and the mechanisms of electron transport in molecularjunctions.

Keywords: Molecular junctions, green function method, inelastic electron tunneling, vibrational excitation, electron-phonon interaction, electronic lifetimes.

[1]. P. Darancet, J. R. Widawsky, H. J. Choi, L. Venkataraman, and J. B. Neaton, "Quantitative Current-Voltage Characteristics in Molecular Junctions from First Principles," Nano letters, vol. 12, pp. 6250-6254, 2012.
[2]. J. E. Morris and K. Iniewski, Nanoelectronic device applications handbook: CRC Press, 2013.
[3]. A. Saffarzadeh, F. Demir, and G. Kirczenow, "Mechanism of the enhanced conductance of a molecular junction under tensile stress," Physical Review B, vol. 89, p. 045431, 2014.
[4]. R. S. Souto, A. L. Yeyati, A. Martin-Rodero, and R. C. Monreal, "Dressed tunneling approximation for electronic transport through molecular transistors," Physical Review B, vol. 89, p. 085412, 2014.
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[6]. B. Bhushan, Springer handbook of nanotechnology: Springer, 2010.

ABSTRACT: The present study was carried out in two adjacent areas of a natural forest and jhumland ecosystem in Mopungchuket village and Chuchuyimpang village respectively, under Mokokchung district, Nagaland, which lies at 26o 11' 36'' North latitude and in between 94o 17' 44'' to 94o 45' 42'' (E) longitude. The study was conducted during January 2009 to December 2011. The vertical distribution and abundance of total soil Acarina were found to be more in the natural forest ecosystem (424.82 x 102 m-2) than jhum land ecosystem (264.70 x 102 m-2) and showed a significant decrease from upper layer to deeper layers i.e., from 0 cm to 30 cm depth. The soil Acarina showed a higher population in the natural forest, with the different values during the different seasons being 231.37 x 102 m-2 (rainy season), 116.20 x 102 m-2 (summer) and 77.25 x 102 m-2 (winter season) respectively. The physico-chemical factors exhibited significant correlation with soil Acarina except soil potassium. The community analysis was carried out for soil Acarina because they are one of the major groups of soil microarthropods and their contributions are maximum in term of species, abundance and distribution.

Key words: Community analysis, Acarina, microarthropods, natural forest and jhum land.

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[3]. Badejo, M. A. and Van Straalen, N. M. (1993). Seasonal abundance of Springtails in two contrasting Environments. Biotropica. 25: 222-228.
[4]. Bhandari, S. C. and Somani, L. L. (1994). In "Ecology and Biology of soil organisms", Agrotech publishing Academy, Udaipur.
[5]. Block, W. C. (1966). Seasonal fluctuations and distribution of mite populations in moorland soil with a note on biomass. J. Anim. Ecol. 35: 487-503.
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ABSTRACT: The Fowler-Nordheim carrier tunneling slope constants for electron and hole conduction through MOS devices fabricated on silicon substrate are utilized to determine the conduction and valence band offsets, carrier effective masses in the SiO2 and its unknown bandgap, independent of photoemission spectroscopic measurements of band offsets on SiO2/Si samples. The slope constants are obtained from the electron and hole tunneling currents versus voltage characteristics on a pair of n-MOS and p-MOS devices in accumulation or an n-channel MOSFET device in inversion that allows carrier separation. This characterization technique called BOEMDET, can be applied to other insulating materials grown or deposited on silicon, such as JVD nitride, HfSiON, SiOxNy, and high-K oxides found viable for future MOS technology. To an accuracy of one decimal place, the conduction band offset for the SiO2/Si<100> MIS structure is determined to be 3.2 eV, the valence band offset obtained is 4.6 eV and the bandgap of SiO2 is found to be 8.9 eV. The electron and hole effective masses in the SiO2 are calculated to be 0.42m and 0.58m, where m is the free electron mass. In case of quantum confinement at the SiO2/Si interface, the electron and hole masses correct to 0.51m and 0.65m. Also, the carrier effective masses in thermal SiO2 are found to be the same for all thickness of the oxide.

Keywords: effective mass, FN-tunneling, band offsets, metal-insulator-semiconductor

[1]. J. Robertson, "High dielectric constant oxides", Eur. Phys. J. Appl. Phys., vol. 28, pp.265-291, Dec. 2004.
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ABSTRACT: In this paper we formulate and solve Newton's gravitational Field equations for a static homogeneous spherical distribution of mass in rotational spherical polar coordinates to pave the way for applications such as planetary theory in rotational spherical polar coordinates.

Key Words: Newton's Gravitational Field Equations, Static Homogeneous Spherical distribution of mass, Rotational Spherical Polar Coordinates

[1] D.D. Bakwa and S.X.K. Howusu " Galaxies as a source of Gravitational Radiation", African Journal of Natural sciences, 6 pp 15 - 18

[2] M.R. Spiegel, Theory and Problems of Vector Analysis and Introduction to Tensor Analysis (Mc Graw - Hill, New York, 1974 ) 55 [3] S.X.K Howusu. 2013; Riemannian Revolution in Physics and Mathematics Jos University press Ltd. Jos pp103-115.

ABSTRACT: A strongly surface active, layered structure is formed at the air-water interface when an aqueous solution of fatted human serum albumin (F-HSA) is spread or mixed with a dilute sol of LS-30 silica nanoparticles at 25°C. X-ray and neutron reflectivity show that the film is quickly established and is sensitive to the ionic strength of the sub-phase. The top layer is largely protein, the second contains silica and a third has diffuse protein. Optical circular dichroism in the mixtures shows that the silica changes the protein helical content.
Keywords: human serum albumin, nanoparticle, structure, toxicology

[1] I. Lynch, T. Cedervall, M. Lundqvist, C. Cabaleiro-Lago, S. Linse, K.A. Dawson, The nanoparticle-protein complex as a biological
entity; a complex fluids and surface science challenge for the 21st century, Adv.Colloid Interface Sci.134 (2007) 167-174.
[2] M.P. Monopoli, C. Arberg, A. Salvati, K.A. Dawson, Biomolecular coronas provide the biological identity of nano-sized
materials,Nat. Nanotechnol. 207 (2012) 779-786.
[3] D.A. Winkler, E. Mombelli, A. Pietroiusti, L. Tran, A. Worth, B. Fadeel, M.J. McCall, Applying quantitative structure-activity
relationship approaches to nanotoxicology: Current status and future potential,
Toxicol.(2012)http://dx.doi.org/10.1016/j.tox.2012.11.005.
[4] J.C. Ang, J-M. Lin, P.N. Yaron, J.W. White, Protein trapping of silica nanoparticles, Soft Matter 6 (2010) 383–390.

[5] J.W. White, J-M. Lin, J.C. Ang, R.A. Campbell, V. Laux, M. Haertlein, G. Fragneto, Nanostructure of the "protein-nanoparticle corona" an indicator of toxicity? International Conference on Nanoscience and Nanotechnology (ICONN), 2010,doi/10.1109/ICONN.2010.6045250289 – 292.

ABSTRACT: A coiled tube single pass counter flow heat exchanger was designed and fabricated using locally available materials and its capacity to transmit heat to water to make steam was tested. The heat exchanger was part of components used in solar thermal power production using a parabolic trough solar concentrator. The design of the heat exchanger storage system was done using Auto CAD 2010 software. Higher temperatures of steam were realized when the heat exchanger was used as a steam storage system. The heat transfer fluids used were locally available and they were water, sunflower oil, Rina oil, used engine oil, unused engine oil, 2 M sodium chloride salt solution, 4 M sodium chloride salt solution and 6 M sodium chloride solution. For each of the heat transfer fluids, heat exchanger operating points were obtained and it was operated between

Keywords: Heat transfer fluids, Heat exchanger team storage, Steam flow rate, Solar radiation

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