Department of Nuclear Science

All living beings on earth are continuously exposed to radiation from primordial radio nuclides 232Th, 238U and 40K present in soils and sands. Due to their long half-lives these radionuclides remain in soils and sands for long periods of time contributing to the natural background radiation. This study was carried out as a part of the island wide survey to measure the radioactivity levels in beaches around the country. The stretch covered in this study was from Beruwala to Dondra. A sand sample at each 1 km interval from Beruwala to Dondra was collected and activity concentrations of 232Th, 238U and 40K were measured using gamma ray spectrometry. Based on the activity concentrations, the annual effective dose rates were calculated. At each sampling location the radiation dose rate at 1 m above ground was also measured using a portable survey meter. The activity concentrations of sand ranged from 6 - 17058 Bq/kg for 232Th, 3 - 3584 Bq/kg for 238U and 3 - 1063 Bq/kg for 40K. Measured gamma dose rates of the sampling locations varied from < 0.01 to 8.61 uSv/h. Annual effective gamma dose rates calculated ranged from 0.01 to 75.38 mSv/yr. The maximum activity concentration of all three radionuclide and the dose rate were measured at Dondra.

Classification of gray images based on their textural features is one of the main tools in medical&lt;br&gt; image processing. Gray Level Co-occurrence Matrix (GLCM) is such a widely used technique&lt;br&gt; which represents how frequently the different gray level combinations occur in an image,&lt;br&gt; traditionally in Cartesian directions. Contrast, correlation, energy and homogeneity are features&lt;br&gt; based on the calculated GLCM. However, in human anatomy, structures often take a curvilinear&lt;br&gt; pattern and therefore the Cartesian GLCM may not be very efficient in medical imaging. In this&lt;br&gt; study, an algorithm was developed to calculate the GLCM in radial and circumferential&lt;br&gt; directions. The texture parameters calculated using the polar GLCM were then tested against&lt;br&gt; those calculated using the traditional Cartesian GLCM, by means of simulated images with&lt;br&gt; varying speckle features. Our results show that the Polar GLCM is better at d...

Frequency dependence of the tissue backscatters provides useful information about the tissue structure. Further, it has been found that structure of tissue changes due to different diseases and these alterations cause observable changes in acoustic scattering properties. Several parameters have been developed to identify these alterations and tissue identification. This study has introduced a new tissue characterization parameter, which is Full width at half maximum (FWHM) of the fitted Gaussian curve of the Fast furrier transformed back scattered signal and it has been used to identify two different tissue samples; bovine liver and chicken liver. The experiment was carried out for nine bovines and nine chicken livers and FWHM of the chicken liver 3.72±0.16 was greater than that of bovine liver 3.28±0.16 (p=2.91E-05). Hence, it can be concluded that the bovine liver and the chicken liver can be differentiate using the FWHM parameter.

All living beings on earth are continuously exposed to radiation from primordial radio nuclides 232-Th, 238-U and 40-K present in soils and sands. Due to their long half lives these radionuclide remain in soils and sands for long periods of time contributing to the natural background radiation. This study was carried out as part of the island wide survey to measure the radioactivity levels in beaches around the country. The stretch covered in this study was from Beruwala to Dondra. A sand sample at each 1 km interval from Beruwala to Dondra was collected and activity concentrations of 232-Th, 238-U and 40-K were measured using gamma ray spectrometry. Based on the activity concentrations the annual effective dose rates were calculated. At each sampling location the radiation dose rate at 1 m above ground was also measured using a potable survey meter. The activity concentrations of sand ranged from 6 to 17058 Bq/kg for 232-Th, 3 to 3584 Bq/kg for 238-U, and 3 to 1063 Bq/kg for 40-K. Measured gamma dose rates of the sampling locations varied from &amp;lt;0.01 to 8.61 µSv/h. Annual effective gamma dose rates calculated ranged from 0.01 to 75.38 mSv/y. The maximum activity concentrations of all three radionuclide and the dose rate were measured at Dondra.

The study was based on simulated magnetic resonance images (MRI) created by MATLAB&lt;br&gt; software. The aim of the study was to estimate the effects of signal to noise ratio (SNR) and&lt;br&gt; flip-angle variations, in the determination of longitudinal relaxation time T1. Simulated MRI&lt;br&gt; experimentswere used to determine the optimal image pixel sampling method to be used in the&lt;br&gt; calculation of T1. Five sampling methods were used to determine mean values of MR image:&lt;br&gt; (1) Dividing the image into four equal blocks, (2) Dividing the image in the direction of flip&lt;br&gt; angle variation, (3) Dividing the image in the direction perpendicular to the flip angle variation,&lt;br&gt; (4) Taking mean pixel value of whole image, and (5) considering the values pixels by pixel.&lt;br&gt; Calculation of T1 using the whole image was identified as the most effective approach, with a&lt;br&gt; minimum deviation of 2.3 ms from the reference value 1000 ms. Minimum and ...

Chronic kidney disease (CKD) of unknown etiology is recognized as a major public health challenge and a leading cause of morbidity and mortality in the dry zone in Sri Lanka. CKD is asymptomatic and are diagnosed only in late stages. Evidence points to strong correlation between progression of CKD and kidney fibrosis. Several biochemical markers of renal fibrosis have been associated with progression of CKD. However, no marker is able to predict CKD consistently and accurately before being detected with traditional clinical tests (serum creatinine, and cystatin C, urine albumin or protein, and ultrasound scanning). In this paper, we hypothesize that fibrosis in the kidney, and therefore the severity of the disease, is reflected in the frequency spectrum of the scattered ultrasound from the kidney. We present a design of a simple ultrasound system, and a set of clinical and laboratory studies to identify spectral characteristics of the scattered ultrasound wave from the kidney that c...

The speci®c radioactivity concentrations of 226 Ra, 232 Th and 40 K have been determined by gamma ray spectrometry with an HPGe detector in clay brick samples from kiln sites located in 17 towns. The average values of the measured activities are 35, 72, and 585 Bq kg À1 , respectively, for the above radionuclides. The average estimated radium equivalent concentration is 183 Bq kg À1 and is comparable with reported values for many countries in the world. This value and the value obtained from the criteria formula suggest that the use of local clay bricks do not pose a radiological hazard. The calculated average absorbed dose rate in air within buildings was found to be 102 nGy h À1 while the population weighted indoor annual eective dose was 0.20 mSv. 7

Elemental concentration of nineteen Ayurvedic drugs have been measured using energy dispersive X-ray fluorescence analysis. Concentrations of nineteen elements: Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe Ni, Cu, Zn, As, Br, Rb, Sr, Zr and Hg have been determined using emission transmission method with Mo target. K, Ca and Fe were detected in all samples and their concentrations ranged from 0.35-2.88%, 0.346-8.65% and 0.007-36.7%, respectively. Maximum concentration measured in other elements ranged from 0.006% to 40.7%. The multi element and non-destructive nature of the method offers a simple way to establish the quality of the drugs that contain heavy metals in considerable concentration.

Air particulate matter of two size fractions (coarse [2.5-10 microns] and fine [less than 2.5 microns]) were collected at an urban residential site (Colombo University ground) over a period of 12 mo during 1996 using a Gent PM10 stacked filter unit. Seventy-five sets of samples collected during this period were analyzed for 10 elements: Al, Si, K, S, Ca, Ti, Fe, Zn, Br, and Pb by energy-dispersive X-ray fluorescence, which is a multielement analysis. This is a highly sensitive technique enabling quantitative analysis of very low masses. The average concentrations of lead, sulfur, and bromine, which are generally associated with combustion products of automotive exhausts, dominate the fine fraction in this study. The minimum and maximum concentration of lead resulting in an annual average of 0.09 microgram/m3 was found to be 0.0042 and 0.441 microgram/m3 in particulate matter with less than 10 microns equivalent aerodynamic diameter. The maximum concentration determined is well below...

Deposits of monazlte bearing soils occur along the Southwest, West and East Coasts of Srl Lanka. High levels of gamma activity in some plant species growing in the West Coast have been reported. The hlgh levels were due to the presence of the daughter nuclides of 232Th, most of which are alpha emitters.

Kandy is the second largest city in Sri Lanka and a major tourist destination. It is a fast growing city with continuous construction of buildings, roads and historical places. More than 100 samples of fine particulate matter (PM) were collected using a GENT stacked filter sampler from a fixed site at the regional sampling station of Department of Meteorology situated in Katugastota, Kandy over the period of 2012 to 2014. Black carbon (BC) in these filters were determined by reflectance measurements while their elemental compositions were determined using the X-ray fluorescence spectrometry. Analysis of the elemental data suggests that the PM in Kandy originates largely from re-suspended soil and anthropogenic sources. The fine particulate matter data including BC and major elements (

Cement used in construction work can cause internal and external radiation exposure due to the presence of natural radionuclides 226 Ra, 232 Th and 40 K. The radiation exposure risk can be estimated by finding the indoor absorbed dose rate and the annual effective dose. If the annual effective dose is within the internationally accepted value, use of cement can be considered safe and the risk will be within acceptable levels. The specific activities of 226 Ra, 232 Th and 40 K in 85 samples from eleven types of cement were measured using gamma spectroscopy with a HPGe detector and the annual effective dose was calculated to determine the radiological hazard from the natural radioactivity in the samples. The average specific activities measured in Bq kg-1 ranged from 21.4 ± 0.9 to 66.8 ± 1.2 ;13.8 ± 0.9 to 62.1 ± 2.3 and 83.7 ± 4.9 to 239.9 ± 5.7 for 226 Ra, 232 Th and 40 K respectively.

Currently, there are several mind models developed as cognitive architectures and their main focus is to explain mind functions. However, few architectures explain the neural basis of the mind. Also, neuroscience explains the neural basis of the brain and is directly related to the mind. The study objective was to identify a mind model with a neural basis established in the model. Therefore, the study uses a systematic review of existing literature to find a mental model with a neural basis. There are 300 articles identified in searching databases of PUBMED and Google Scholar. After duplicated removal, initial screening was done using an independent reviewer and remaining full-text articles were submitted to eligibility assessment. From the assessed full-text articles, 9 full-text articles were selected for synthesis. From those selected architectures, considering the richness of mental functions and richness of neurological assemblies, features of the architectures op of ACT-R (Ada...

The special relativity explains how the matter transforms into energy. According to that matter can be generated with negative energy and matter can destroy with negative energy. The negative energy can be identified as dark energy. According to this matter generation, which is the process of black holes, emitting radiation from the quasar is the evidence. Matter generation as radiation matter. Matter destroying is the process of stars. The energy and dark energy get negated in the supernova and nova explosions. Stars emit the light by the speed of light is the evidence of the matter destroying process. The matter creation process makes the universe grow and the matter destroying process makes the universe to shrink, combining this process makes the universe to curvature. Also, matter generation makes the universe expansion power of -ρc 2 and matter destroying make the universe to compression power of ρc 2 . This makes state equation same as the curvature. Therefore k 0 and compress...

The Λ CDM is the standard model describing the origin and evaluation of the universe. It explains the origin of the universe was Big Bang, before it very hot and highly dense state. Then inflation in small time and universe expands exponential rate. In this universe filled with radiation matter. Then big band nucleosynthesis happens and baryons created in decoupling (radiation and matter equilibrium) era  explained by CMB. Then becomes matter-dominated era. Observed baryonic matter is only 5 % and found 10-30% of masses are hot gasses. This suggests the existence of dark matter. Remain 70 % of the universe consist of dark energy. Dark energy mainly related to the expansion of the universe and believes acceleration of the universe since dark energy. Fluctuations of the matter grow from CMB and evolve as the formation of structures like galaxies and clusters. These fluctuations grow as adiabatic, isothermal, CDM and HDM fluctuations. Adiabatic, CDM makes top-down and isothermal, HDM m...

Currently, there are several mind models developed as cognitive architectures and their main focus is to explain mind functions. However, few architectures explain the neural basis of the mind. Also, neuroscience explains the neural basis of the brain and is directly related to the mind. The study objective was to identify a mind model with a neural basis established in the model. Therefore, the study uses a systematic review of existing literature to find a mental model with a neural basis. There are 300 articles identified in searching databases of PUBMED and Google Scholar. After duplicated removal, initial screening was done using an independent reviewer and remaining full-text articles were submitted to eligibility assessment. From the assessed fulltext articles, 9 full-text articles were selected for synthesis. From those selected architectures, considering the richness of mental functions and richness of neurological assemblies, features of the architectures op of ACT-R (Adaptive control of thoughts-Rational) cognitive architecture, Leabra cognitive architecture and an embodied cognitiveaffective architecture select for inclusion in the final model. The central structure of the mind is the amygdala. It gets sensory inputs through the sensory cortex and external stimuli through the thalamus. It processes those inputs using working memory as mPFC and dLPFC. After processing, the amygdala provides output as behavior. Also, brain structures of the partial cortex, cortex, para hippo cortex, perirhinal cortex, entorhinal cortex, subiculum, dentate gyrus, CA1 and CA3 areas of the hippocampus are used for memory encoding, memory retrieval, and critical learning. Overall, the posterior cortex processes the sensory and semantic information. The hippocampus works as episodic memory. The frontal cortex works as active maintenance of the thinking process. The basal ganglia works as action selection and the main part of the thinking process. This reveals the mind model with neurological circuit assemblies to it. The final model will limit to features of the currently existing literature.