University of Peradeniya

About: University of Peradeniya is a education organization based out in Kandy, Sri Lanka. It is known for research contribution in the topics: Population & Poison control. The organization has 5970 authors who have published 7388 publications receiving 197002 citations.

Comparison of linkage disequilibrium and haplotype diversity on macro- and microchromosomes in chicken.

Abstract: The chicken (Gallus gallus), like most avian species, has a very distinct karyotype consisting of many micro- and a few macrochromosomes. While it is known that recombination frequencies are much higher for micro- as compared to macrochromosomes, there is limited information on differences in linkage disequilibrium (LD) and haplotype diversity between these two classes of chromosomes. In this study, LD and haplotype diversity were systematically characterized in 371 birds from eight chicken populations (commercial lines, fancy breeds, and red jungle fowl) across macro- and microchromosomes. To this end we sampled four regions of ~1 cM each on macrochromosomes (GGA1 and GGA2), and four 1.5 -2 cM regions on microchromosomes (GGA26 and GGA27) at a high density of 1 SNP every 2 kb (total of 889 SNPs). At a similar physical distance, LD, haplotype homozygosity, haploblock structure, and haplotype sharing were all lower for the micro- as compared to the macrochromosomes. These differences were consistent across populations. Heterozygosity, genetic differentiation, and derived allele frequencies were also higher for the microchromosomes. Differences in LD, haplotype variation, and haplotype sharing between populations were largely in line with known demographic history of the commercial chicken. Despite very low levels of LD, as measured by r2 for most populations, some haploblock structure was observed, particularly in the macrochromosomes, but the haploblock sizes were typically less than 10 kb. Differences in LD between micro- and macrochromosomes were almost completely explained by differences in recombination rate. Differences in haplotype diversity and haplotype sharing between micro- and macrochromosomes were explained by differences in recombination rate and genotype variation. Haploblock structure was consistent with demography of the chicken populations, and differences in recombination rates between micro- and macrochromosomes. The limited haploblock structure and LD suggests that future whole-genome marker assays will need 100+K SNPs to exploit haplotype information. Interpretation and transferability of genetic parameters will need to take into account the size of chromosomes in chicken, and, since most birds have microchromosomes, in other avian species as well.

Anthropophagy and aggregation behaviour of the sandfly Phlebotomus argentipes in Sri Lanka

Abstract: The visceral leishmaniasis (VL) vector Phlebotomus argentipes Annandale & Brunetti is widely distributed throughout the Indian sub-continent and S.E. Asia. The absence of VL in areas such as Sri Lanka has been attributed to the zoophilic nature of P.argentipes, since they were not recorded biting man. Field studies on P.argentipes were undertaken in the central highlands of Sri Lanka, near Kandy, in May 1988. Male sandflies outnumbered females on cows by 19:1, and were regularly spaced at all densities. This behaviour is considered analagous to swarming in other Nematocera. However, all-night human-biting catches show the biting rate to be similar (mean = 8.4, range 2-25 bites per night over ten consecutive nights) to that in N.E. India where VL is endemic. This anthropophagy was maintained during laboratory colonization.

Cytomorphometric analysis of squames obtained from normal oral mucosa and lesions of oral leukoplakia and squamous cell carcinoma.

Abstract: Ramaesh T, Mendis BRRN, Ratnatunga N, Thattil RQ: Cytomorphometric analysis of squames obtained from normal oral mucosa and lesions of oral leukoplakia and squamous cell carcinoma. J Oral Pathol Med 1998; 27: 83–6. © Munksgaard, 1998. Cell and nuclear diameters (CD and ND) were measured in squames obtained from normal buccal mucosa and lesions of oral leukoplakia and squamous carcinoma (SCC) also from buccal mucosa. The study groups consisted of Group 1: normal buccal mucosa (n= 40); Group 2: lesions with no epithelial dysplasia (n= 58); Group 3: lesions with epithelial dysplasia (n= 27); and Group 4: SCC lesions (n= 51). The mean CD and ND values were: Group 1: 51.78 (± 0.11) and 8.36 (± 0.49); Group 2: 45.73 (± 0.16) and 8.31(± 0.68); Group 3: 41.32 (± 0.13) and 9.04 (± 0.46); Group 4: 38.58 (± 0.11) and 10.10 (± 0.56) urn, respectively. Correlation between the ND and CD was positive for Group 1 (r= 0.78, P < 0.05) and Group 2 (r= 0.33, P < 0.05). There were no significant correlations in Groups 3 and 4. ANOVA showed significant differences (P < 0.05) for CD between all four groups. Except between Groups 1 and 2, the ND was significantly different (P < 0.05) between all groups. The results indicate that ND and CD could possibly be sensitive parameters in the diagnosis of oral premalignant and malignant lesions.

Cooperative Beamforming and User Selection for Improving the Security of Relay-Aided Systems

Abstract: A relay network in which a source wishes to convey a confidential message to a legitimate destination with the assistance of trusted relays is considered. In particular, cooperative beamforming and user selection techniques are applied to protect the confidential message. The secrecy rate (SR) and secrecy outage probability (SOP) of the network are investigated first, and a tight upper bound for the SR and an exact formula for the SOP are derived. Next, asymptotic approximations for the SR and SOP in the high signal-to-noise ratio (SNR) regime are derived for two different schemes: 1) cooperative beamforming and 2) multiuser selection. Furthermore, a new concept of cooperative diversity gain, namely, adapted cooperative diversity gain (ACDG), which can be used to evaluate the security level of a cooperative relaying network, is investigated. It is shown that the ACDG of cooperative beamforming is equal to the conventional cooperative diversity gain of traditional multiple-input single-output networks, while the ACDG of the multiuser scenario is equal to that of traditional single-input multiple-output networks.