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Etude de la conductivite electrique de monocristaux entre 140 et 280°C. Le transport electronique est probablement du a un processus de sauts (mecanisme de petits polarons)
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The path of maximum for the annular eclipse of December 26th,2019, includes land areas of Saudi Arabia, India, Sri Lanka, Sumatra, Malasia, Philippines, and Guam; that is, in addition to passing through the Indian and Pacific oceans. A... more
The path of maximum for the annular eclipse of December 26th,2019, includes land areas of Saudi Arabia, India, Sri Lanka, Sumatra, Malasia, Philippines, and Guam; that is, in addition to passing through the Indian and Pacific oceans. A team of interested scientists travel to the city of Jaffna, Sri Lanka, and report their measurements. Jaffna, itself, happens to be on the path of maximum. Spectral intensity variation, surface ozone and hydrogen H-alpha measurements conducted are compared to prior experiments. In our previous experiments, carried out at the University of West Georgia, Carrollton, Georgia, during the time of the solar eclipse of 21st August, 2017, demonstrated that the integrated spectral irradiance in defined wavelength ranges in the ultraviolet and visible reached a minimum at maximum obscuration of the sun, whereas in an infrared range it was maximum. In a surface ozone measurement, a minimum in ozone concentration occurred thirty minutes after the instant of maximum obscuration. This Jafna eclipse allows us an opportunity to conduct an additional trial to previous observations. The results of measurements as well as the journey to the observation camp are discussed
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The analysis of COVID-19 statistics in different regions of the world with the intention of understanding the trend of progression of the pandemic is a task of paramount importance. Publicly available data includes cumulative number of... more
The analysis of COVID-19 statistics in different regions of the world with the intention of understanding the trend of progression of the pandemic is a task of paramount importance. Publicly available data includes cumulative number of cases, new cases each day, and the mortality. Extracting information from this data necessitates mathematical modeling. In this note a simple technique is adopted to determine the trend towards stabilized elimination of the infection, as implicated by saturation of the cumulative number of cases. Results pertaining to several representative regions of the world are presented. In several regions, evidence there to the effect that the pandemic will come to an end. The estimated saturation values of the cumulative numbers are indicated.
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Long-chain normal aliphatic alcohols are found to suppress photocorrosion and increase the efficiency of a cuprous oxide photoelectrochemical cell with aqueous thiocyanate solution as the electrolyte. It is suggested that alcohols inhibit... more
Long-chain normal aliphatic alcohols are found to suppress photocorrosion and increase the efficiency of a cuprous oxide photoelectrochemical cell with aqueous thiocyanate solution as the electrolyte. It is suggested that alcohols inhibit corrosion by surface adsorption.
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Research Interests: Medicine and Dengue fever
A simple theory is presented to explain the observation that heavy metal ferrocyanides and ferricyanides become n- and p-type semiconductors respectively on absorption of trace quantities of water.
Research Interests: Chemistry and Heavy Metal
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Abstract Chlorobenzoic acids(CBA) are completely mineralized into CO 2 and Cl-over UV-illuminated TiO 2 in water according to the following reactivity order : 4-CBA〈2-CBA〈3-CBA. The identification of various intermediates of 2-CBA shows... more
Abstract Chlorobenzoic acids(CBA) are completely mineralized into CO 2 and Cl-over UV-illuminated TiO 2 in water according to the following reactivity order : 4-CBA〈2-CBA〈3-CBA. The identification of various intermediates of 2-CBA shows the decarboxylation and the progressive hydroxylation of the aromatic ring. This study confirms the potentialities of photocatalysis for water detoxification.
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It is shown that the arguments given in the Comment on the solvated polaron by Karvaly to show that the solvation increases the thermal activation energy are fallacious. The misconception has arisen from the use of formulas as in the... more
It is shown that the arguments given in the Comment on the solvated polaron by Karvaly to show that the solvation increases the thermal activation energy are fallacious. The misconception has arisen from the use of formulas as in the polaron theory without identification of their real physical significance.
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Adsorbed water molecules are found to activate electronic conduction in several molecular solids. Experimental data on Malachite Green and Rosaniline are presented to illustrate the phenomenon.
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ABSTRACT Understanding of the charge transport and recombination mechanisms of dye-sensitized solar cells based on semiconductor nanostructures is essential for the improvement of their performance. A great deal of information on these... more
ABSTRACT Understanding of the charge transport and recombination mechanisms of dye-sensitized solar cells based on semiconductor nanostructures is essential for the improvement of their performance. A great deal of information on these systems have been obtained from studies on a single material (mostly TiO2 and to a lesser extent ZnO and SnO2). We have conducted extensive measurements on composite dye-sensitized nanosturctures and found that the composite systems possess unusual properties. Dye-sensitized photoelectrochemical cells made from nanocrystalline films of some materials (e.g., SnO2) yield comparatively small open-circuit voltages and energy and quantum conversion efficiencies, despite excellent dye-semiconductor interaction. However, on deposition of ultra-thin shells of insulators or high band gap semiconductors on the crystallites, a dramatic increase in the above parameters is observed. Outer shells were found to have insignificant or in most cases a negative effect on TiO2 films. We explain the above findings on the basis of vast differences in the leakage rates of trapped electrons in different materials which is sensitive to the effective electron mass. Electrons injected to the conduction band in dye-sensitization enter into shallow traps from which they get thermally reemitted to the conduction band. The building up of the electron quasi-fermi level and transport depends on this process. The spread of the hydrogenic wave function of a trapped electron increases inverse exponentially with the effective mass so that the electron leakage and their recombination with acceptors ‘outside’ become severe when the crystallite size is comparable to the Bohr radius of the trapped electron. Such recombinations are effectively suppressed by deposition of thin films on the crystallites. Excited dye molecules anchored to the outer shell injects electrons to the conduction band via tunneling.
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Solar energy conversion concept based on nanostructured materials has attracted much attention as an avenue to develop cheaper and more efficient solar cells. Both dye molecules and quantum dots can sensitize high band gap semiconductor... more
Solar energy conversion concept based on nanostructured materials has attracted much attention as an avenue to develop cheaper and more efficient solar cells. Both dye molecules and quantum dots can sensitize high band gap semiconductor by injecting carriers to the conduction band (CB) or valence band (VB) of the high band gap material, if energy band levels are in appropriate configuration and have a suitable bond between them. However, other physical properties of dye anchored and quantum dot embedded nanostructured semiconductor films offers the possibility of designing hybrid systems of higher efficiency. The low efficiency of dye-sensitized solar cells is partly attributed to the poor electron transport properties of the dye coated nanocrystalline matrix. Encapsulation of PbS quantum dots could enhance the electronic conductivity of nanostructured ZnO films. PbS quantum dot sensitized ZnO films shows sensitizing response to light absorption in ZnO, PbS QDs and dyes anchored to ZnO. As a result of the improvement of transport properties by the QDs, photocurrent response of composite system due to light absorption by ZnO and dye are also enhanced. Possibilities of adopting this concept in solar cells and multi-band photon detectors will be discussed.
Title: Neutrino halos around the sun and precession of perihelia of planets. Authors: Tennakone, K. Publication: Hadronic J., Vol. 7, p. 728 - 733. Publication Date: 00/1984. Origin: ARI. ARI Keywords: Neutrinos, Planets:Relativistic... more
Title: Neutrino halos around the sun and precession of perihelia of planets. Authors: Tennakone, K. Publication: Hadronic J., Vol. 7, p. 728 - 733. Publication Date: 00/1984. Origin: ARI. ARI Keywords: Neutrinos, Planets:Relativistic Effects. Bibliographic Code: 1984HadJ....7..728T ...
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Abstract K4Fe(CN)6 ⋯ 3H2O is found to be a K+ ion conductor. It is suggested that K+ mobility originates from formation of hydrogen bonded aggregates of H2O molecules in the vicinity of K+ ions.
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Abstract PbFCNS is found to be a F − ion conducting solid of high room temperature conductivity ( σ 30 ∽ 1.2 × 10 -4 ω -1 cm -1 ). The method of preparation and the conductivity properties of the material are described.
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Abstract Pure solid iodine doped with hydrogen iodide is found to exhibit proton conductivity with a thermal activation energy ≃ 0.34 eV. It is suggested that protons are generated via electrolytic dissociation of HI molecules by the... more
Abstract Pure solid iodine doped with hydrogen iodide is found to exhibit proton conductivity with a thermal activation energy ≃ 0.34 eV. It is suggested that protons are generated via electrolytic dissociation of HI molecules by the dielectric medium of solid iodine.
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Polycrystalline copper sulphide (p-CuxS) shows a feeble cathodic photoresponse in electrolytic media. When a thin film of n-CdS is deposited, the cathodic photocurrent quantum efficiency is increased by several orders of magnitude. The... more
Polycrystalline copper sulphide (p-CuxS) shows a feeble cathodic photoresponse in electrolytic media. When a thin film of n-CdS is deposited, the cathodic photocurrent quantum efficiency is increased by several orders of magnitude. The mechanism involved is discussed.