Gapless points of dimerized quantum spin chains: analytical and numerical studies

We study the locations of the gapless points which occur for quantum spin chains of finite length (with a twisted boundary condition) at particular values of the nearest neighbor dimerization, as a function of the spin S and the number of sites. For strong dimerization and large values of S, a tunneling calculation reproduces the same results as those obtained from more involved field theoretic methods using the non-linear sigma-model approach. A different analytical calculation of the matrix element between the two Neel states gives a set of gapless points; for strong dimerization, these differ significantly from the tunneling values. Finally, the exact diagonalization method for a finite number of sites yields a set of gapless points which are in good agreement with the Neel state calculations for all values of the dimerization, but the agreement with the tunneling values is not very good even for large S. This raises questions about possible corrections to the tunneling results.Comment: Revtex4, 10 pages including 5 figure

Exact Haldane mapping for all SS and super universality in spin chains

The low energy dynamics of the anti-ferromagnetic Heisenberg spin $S$ chain in the semiclassical limit $S\to\infty$ is known to map onto the O(3) nonlinear $\sigma$ model with a $\theta$ term in 1+1 dimension. Guided by the underlying dual symmetry of the spin chain, as well as the recently established topological significance of "dangling edge spins," we report an {\em exact} mapping onto the O(3) model that avoids the conventional large $S$ approximation altogether. Our new methodology demonstrates all the super universal features of the $\theta$ angle concept that previously arose in the theory of the quantum Hall effect. It explains why Haldane's original ideas remarkably yield the correct answer in spite of the fundamental complications that generally exist in the idea of semiclassical expansions

A nutrigenetic approach to examine the relationship between vitamin B12 status and metabolic traits in multiple ethnic groups

Low vitamin B12 concentrations have been shown to be risk factors for metabolic traits in numerous observational studies; however, the relationship has remained inconsistent. It is possible that certain genotypes might jointly contribute to obesity and vitamin B12 deficiency, and these may be modulated by lifestyle factors (dietary factors and physical activity levels) across different ethnic groups. The implementation of a genetic approach to establish the relationship between vitamin B12 and obesity could be a more desirable option over observational studies, as results are less prone to confounding factors. Hence, the main aims of this thesis were to examine for the first time the association of common vitamin B12-related single nucleotide polymorphisms (SNPs) and metabolic SNPs with vitamin B12 concentrations and metabolic outcomes in multiple ethnic groups. In addition, the interaction between these SNPs and dietary factors (protein, carbohydrate and fat) on vitamin B12 concentrations and metabolic traits was investigated. A total of five studies with different study designs were used. These studies included a case-control study (Chennai Urban Rural Study; CURES, Asian India, n=900), three cross-sectional cohort studies [Genetics of obesity and Diabetes study (GOOD study; Sinhalese Sri Lankan adults, n=109), The Minangkabau Indonesia Study on Nutrition and Genetics (MINANG study; Indonesian women; n=118) and Brazilian adolescents (n=113)] and a 16 week-dietary randomized, single-blind, parallel-group dietary intervention [Dietary Intervention and VAScular function (DIVAS study; British adults, n=119)]. Gene-diet interactions were observed in the Sri Lankan and Indonesian populations between the vitamin B12-related SNPs and protein energy intake (%) on markers of central obesity (waist circumference (P=0.002) and body fat percentage (P= 0.034), respectively). In the Brazilian adolescent population, the metabolic and vitamin B12 related SNPs showed a significant interaction with carbohydrate and protein intakes on oxidised low density lipoprotein cholesterol (P=0.005) and homocysteine concentrations (P = 0.007), respectively, which are well-known independent risk factors for cardiovascular disease. Additionally, in the Indonesian population, an interaction was observed between vitamin B12-related SNPs and dietary fibre intake (g) on glycated haemoglobin levels (P =0.042), a marker of long-term glycaemic status. Furthermore, for the first time, a novel association between two obesity-related SNPs and vitamin B12 concentrations (P = 0.018) was observed in the Indian population. In summary, these studies in multiple ethnic groups show that the relationship between B12 deficiency and metabolic outcomes may be influenced by dietary factors such as protein and fibre intake. However, in the Indian population, we found that vitamin B12 concentrations may be influenced by a genetic predisposition to obesity, but without a dietary influence. Given the limited sample size in some of the cohorts, replication of the study findings is highly warranted

The Theory of Tamil God Murugan

Murugu means beauty. If the beauty means Lord Muruga, he is the lord. Since Lord Muruga is the god of Tamils, murugan is called tamil god. Let us look at the principles of the great Tamil god Murugan. The principle of Lord Muruga is morality, charity should remain in this world. In this article, one can learn that to attain salvation, one should worship Lord Muruga and follow his righteous ness and attain salvation

Host Defense Mechanisms with Special Reference to Chemokines and Viral Infections

An important role for the mammalian body is to guard against infection by pathogenic micro-organisms. There are 5 main classes of pathogens, namely, viruses, bacteria, parasites, fungi, and worms. The complex relationships between these pathogenic micro-organisms and the vertebrate host are perhaps most clearly understood for viruses. The survival of viruses depends on the survival of susceptible hosts. In recent years, chemokines have been shown to play an integral role in the recruitment of cells to sites of infection, thus mediating the healing process. This review will provide an overview of immune responses with reference to viral infections and chemokines

The Impact Of Clean Development Mechanism Projects On Sustainable Development In South Africa

Clean Development Mechanisms (CDM) have achieved a certain level of cost-effective emission reductions in developing countries. In this context the uneven distribution of CDM projects in certain regions as well as the concentration of CDM projects amongst certain sectors in developing countries have resulted in the issue of whether CDM projects contribute to sustainable development in developing countries. This article examines the impact of CDM projects on sustainable development in South Africa by examining a sample of working CDM projects there and evaluating their impact on environmental, economic and social sustainable development. Based on observations during the study, CDM policy changes are reviewed, and options to enhance the sustainable development implications of CDM projects are explained

Genetic mapping and molecular characterisation of Russian wheat aphid resistance loci in wheat

The Russian wheat aphid (RWA, Diuraphis noxia Kurdmojov) is considered as one of the most destructive pest of wheat around the world, causing significant yield loss in wheat cultivation. A continuous process of searching for novel resistance loci (Dn) to combat evolving new RWA biotypes has been successful in providing RWA resistance to breeding programs. Australia was declared as a RWA free country but Infestation of RWA was first time reported in Tarlee, South Australia in April, 2016. A novel resistance source, PI94365 with expressing resistance to several biotypes found in other countries was selected to incorporate its resistance into the Australian cultivar EGA Gregory. A double haploid (DH) population developed through the microspore technique was phenotyped in South Africa, Turkey and Morocco with respective biotypes. A genetic linkage map was constructed with 4053 molecular markers including simple sequence repeats (SSR), genome by sequencing (GBS) and Diversity array technology (DArT) molecular markers. Major QTLs to RWA resistance were mapped on 1DS, 7DS and 7BL and minor QTLs were mapped on 3BL, 4AS and 4DL. POPSEQ genetic map distances for the QTLs identified on chromosomes 1DS and 7DS were determined by comparative genomics studies with published consensus and POPSEQ maps. A large number of molecular markers have been identified in the region of RWA resistance loci for the marker assisted plant breeding. Proteomics studies in the absence of live aphids (due to quarantine restriction in Australia) were carried out in order to reveal the resistance mechanism driven by constitutive genes. Ten proteins were significantly differentially expressed between resistance and susceptible lines selected from the double haploid population that was mapped in detail through haplotype analysis. These proteins were annotated using the current wheat genome assembly and functional annotation in relation to RWA resistance. Studies identified several induced proteins with RWA infestations. Differentially expressed genes identified in these studies annotated to the wheat genome together with their genetic map location assigned some of the genes to major RWA resistance QTLs and thus this study provided some new insights into RWA resistance. Over all, the work carried out in this study delivered RWA resistant wheat lines for breeding resistance cultivars that are well characterized by a broad range of molecular markers in the regions of the RWA resistance loci. The high density of new molecular markers provides for the efficient tracking of RWA resistance loci in the pipe-line of cultivar development within the framework of quarantine restrictions