Sri Lankan Journal of Physics, Volume 6, March 2005.
Light Scattering Intensity and Viscosity Correlation for the Letters
Printed on the Tobacco Cigarettes
P. M. Jayaweera*1, C. Pathiraja2 and R. M. S. P.
Rajapaksha1
1Dept. of Chemistry, University of Sri Jayewardenepura, Nugegoda
10250, Sri Lanka, 2Ceylon Tobacco Company, Colombo 01500, Sri Lanka
The quality of the letters printed on the tobacco cigarettes, brand name "John PlayerTM" is found to be viscosity dependent on the ink used for printing. The viscosity changes of the ink used, cause the printed letters to be smudged and of poor quality. At present selection of bad quality prints are done by visual identification, as no scientific technique is available. We have developed a light scattering technique using a 632.8 nm 20 mW He-Ne laser system to correlate the scattering intensity with the viscosity of the ink used, LogoRed TC2582. As a result, a standard has been assigned and quality of the cigarette prints can be maintained during the manufacturing process.
Sri Lankan Journal of Physics, Volume 6, March 2005.
Trends of Rainfall in Sri Lanka over the Last Century
H. K. W. I. Jayawardene1, D. U. J. Sonnadara1,* and D. R.
Jayewardene2
1Department of Physics, University of Colombo, Colombo 00300, Sri Lanka,
2
Department of Mathematics, University of Colombo, Colombo 00300, Sri
Lanka
Utilizing over 100 years of rainfall records in 15 meteorology stations, an analysis was carried out to extract the trends of annual rainfall depth in Sri Lanka over the last century. A statistically significant increasing trend of rate 3.15 mm/year was observed at Colombo and decreasing trends were observed at Nuwara Eliya and Kandy with rates of 4.87 mm/year and 2.88 mm/year respectively. Since no coherent increase or decrease of rainfall in any group of stations in the wet or dry zones was observed, the possibility of large scale change over the past century was ruled out. However, more recent data records (1949 onwards), revealed a decreasing trends in 13 of the 15 stations. Thus, traces of a temporal change seem to be apparent in the rainfall records over the last half century. In general, the downward trends in recent decades are steeper than the long term variations. For the recent data records, the largest downward trend of 11.16 mm/year was observed at Batticaloa.
Sri Lankan Journal of Physics, Volume 6, March 2005.
Human exposure to RF radiation in Sri Lanka
M. A. A. Karunarathna and I. J. Dayawana*
Department of Electronic and Telecommunication, University of Moratuwa, Moratuwa,
10400, Sri Lanka
This paper presents the exposure levels of major cities in Sri Lanka due to the different RF emitters. As the RF emitters, the transmitting antennas of FM radio, TV and Cellular Mobile Base stations were considered. Field strength measurements were made at several locations in big cities and the exposure levels were obtained using a dipole antenna mounted 1.4m above the ground level to consider the exposure to RF radiation by the general public. The results were compared with the internationally recognized FCC standards and the present exposure levels were found to be well below the maximum limits set by the standards. The percentage distribution of electromagnetic field radiated from FM radio, TV and Cellular Mobile services for different environments are also presented. In addition, the unsafe distances to live from different transmitting antennas are presented.
Sri Lankan Journal of Physics, Volume 6, March 2005.
Internal
Dosimetry of Human Brain for 99mtc and 131I
Using Nuclear Imaging in Bangladesh
M. M. Alama, M. I. Kabirb, K. A. Zamanc, M. Rafiuddind, G. U. Ahmadd
aDepartment of Mathematics and Physics, East West University, Dhaka, Bangladesh,
b Department of Physics, International Islamic University Chittagang,
Dhaka Campus, Bangladesh,
c Bangladesh Atomic Energy Commission, Dhaka, Bangladesh, d
Department of Physics, Bangladesh University of Engineering and
Technology, Dhaka, Bangladesh
Internal dosimetry deals with the measurement of the radiation dose absorbed internally by an organ after the application of isotopes for diagnosis and treatment. In the present study radiation absorbed dose has been calculated for 99mTc-pertechnetate, 99m Tc-DTPA, 99m Tchepatate and 131I (NaI) which are used frequently for functioning test of disordered organs and therapeutic treatment of thyroid in Bangladesh. In these cases a small amount of isotopes are accumulated in other soft tissues like brain, gonads etc. Brain tissues are soft and cannot be regenerated if it is damaged. So, to ensure the safety of brain, the internal radiation absorbed dose has been calculated from direct measurement by using planer image of gamma cameras. International Commission for Radiological Protection (ICRP) and National Commission for Radiation Protection (NCRP) have laid emphasis on direct measurement because it provides more accurate result than that of other methods which are based on few mathematical assumption, bio-kinetic modeling and extrapolation of animal data to human etc. Finally these results have been compared with the data of ICRP publication 71.
Sri Lankan Journal of Physics, Volume 6, March 2005.
Synthesis of Triphenylamine
Trisazo Dye and Study of its Uses in Dye Sensitized Solar Cells
G. K. R. Senadeera 1,* and K-J. Jiang2
1Institute of Fundamental Studies, Kandy 20000, Sri Lanka, 2
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080,
P.R. China,
A new triazo dye was synthesized from tri(p-aminophenyl)amine and 2 hydroxy-3-napthoic acid and explored the possibilities of its uses in dye sensitized solar cells for the first time. The photocells were able to generate reasonably high photocurrent in the presence of the electron donating ionic liquids in the electrolyte composed of redox couple I3-/I-. Cells fabricated by sensitizing TiO2 generated a short-circuit photocurrent of ~ 3.5 mA cm-2, an open-circuit photovoltage of ~ 500 mV with a total power conversion efficiency of ~ 1 % under simulated full sunlight of 100 mW cm-2 (Air Mass 1.5).
Sri Lankan Journal of Physics, Volume 6, March 2005.
Redistribution of Energy in Electromagnetic Wave Interactions
Interference of electromagnetic waves; a different approach
C. K. G. Piyadasa
Department of Physics, University of Colombo, Colombo 00300, Sri Lanka
One of the well-known effects of electromagnetic waves is interference. Redistribution of energy in interference is well documented in literature but the mechanism has not been discussed in detail. A set of new experiments has been designed and conducted to observe the actual redistribution of the energy of the electromagnetic waves while being interfered and after leaving the region of interference. In this paper, it is shown that the redistribution of energy in interference of electromagnetic waves maintains the energy distribution prevailed at the moment they leave the disturbance (interference) area. Modified wave fronts which separated after intersection of two coherent waves in microwave frequency is demonstrated. Results are presented in pictorial and graphical models in order to understand the phenomena,. Further experiments are underway and possible mechanism will be discussed later.