Surface and bulk transitions in three-dimensional O(n) models

Using Monte Carlo methods and finite-size scaling, we investigate surface criticality in the O$(n)$ models on the simple-cubic lattice with $n=1$, 2, and 3, i.e. the Ising, XY, and Heisenberg models. For the critical couplings we find $K_{\rm c}(n=2)=0.454 1655 (10)$ and $K_{\rm c}(n=3)= 0.693 002 (2)$. We simulate the three models with open surfaces and determine the surface magnetic exponents at the ordinary transition to be $y_{h1}^{\rm (o)}=0.7374 (15)$, $0.781 (2)$, and $0.813 (2)$ for $n=1$, 2, and 3, respectively. Then we vary the surface coupling $K_1$ and locate the so-called special transition at $\kappa_{\rm c} (n=1)=0.50214 (8)$ and $\kappa_{\rm c} (n=2)=0.6222 (3)$, where $\kappa=K_1/K-1$. The corresponding surface thermal and magnetic exponents are $y_{t1}^{\rm (s)} =0.715 (1)$ and $y_{h1}^{\rm (s)} =1.636 (1)$ for the Ising model, and $y_{t1}^{\rm (s)} =0.608 (4)$ and$y_{h1}^{\rm (s)} =1.675 (1)$ for the XY model. Finite-size corrections with an exponent close to -1/2 occur for both models. Also for the Heisenberg model we find substantial evidence for the existence of a special surface transition.Comment: TeX paper and 10 eps figure

Monte Carlo computation of correlation times of independent relaxation modes at criticality

We investigate aspects of universality of Glauber critical dynamics in two dimensions. We compute the critical exponent $z$ and numerically corroborate its universality for three different models in the static Ising universality class and for five independent relaxation modes. We also present evidence for universality of amplitude ratios, which shows that, as far as dynamic behavior is concerned, each model in a given universality class is characterized by a single non-universal metric factor which determines the overall time scale. This paper also discusses in detail the variational and projection methods that are used to compute relaxation times with high accuracy

Transfer-Matrix Monte Carlo Estimates of Critical Points in the Simple Cubic Ising, Planar and Heisenberg Models

The principle and the efficiency of the Monte Carlo transfer-matrix algorithm are discussed. Enhancements of this algorithm are illustrated by applications to several phase transitions in lattice spin models. We demonstrate how the statistical noise can be reduced considerably by a similarity transformation of the transfer matrix using a variational estimate of its leading eigenvector, in analogy with a common practice in various quantum Monte Carlo techniques. Here we take the two-dimensional coupled $XY$-Ising model as an example. Furthermore, we calculate interface free energies of finite three-dimensional O($n$) models, for the three cases $n=1$, 2 and 3. Application of finite-size scaling to the numerical results yields estimates of the critical points of these three models. The statistical precision of the estimates is satisfactory for the modest amount of computer time spent

Critical Surface Free Energies and Universal Finite-Size Scaling Amplitudes of Three-Dimensional XY Models by Direct Monte Carlo Sampling

Direct Monte Carlo sampling is employed to obtain estimates of excess surface free energies of three-dimensional XY models at criticality. Results for simple-cubic and body-centered-cubic lattices are consistent with universality of finite-size scaling amplitudes. The results are used to estimate the magnitude of the thinning effect, mediated by the incipient long-ranged correlations, on liquid-helium films at the λ point

Surface Free Energies of Three-Dimensional Ising Models and Universality of Finite-Size Scaling Amplitudes by Direct Monte Carlo Sampling

Direct Monte Carlo sampling is employed to obtain estimates of excess surface free energies of three-dimensional Ising models at criticality. Results for simple and body-centered-cubic lattices provide strong evidence for the universality of finite-size scaling amplitudes and in particular the related interaction per unit area, mediated via the incipient long-ranged correlations, of two free surfaces a finite distance apart

Lineage specific recombination rates and microevolution in Listeria monocytogenes

Background: The bacterium Listeria monocytogenes is a saprotroph as well as an opportunistic human foodborne pathogen, which has previously been shown to consist of at least two widespread lineages (termed lineages I and II) and an uncommon lineage (lineage III). While some L. monocytogenes strains show evidence for considerable diversification by homologous recombination, our understanding of the contribution of recombination to L. monocytogenes evolution is still limited. We therefore used STRUCTURE and ClonalFrame, two programs that model the effect of recombination, to make inferences about the population structure and different aspects of the recombination process in L. monocytogenes. Analyses were performed using sequences for seven loci (including the house-keeping genes gap, prs, purM and ribC, the stress response gene sigB, and the virulence genes actA and inlA) for 195 L. monocytogenes isolates. Results: Sequence analyses with ClonalFrame and the Sawyer's test showed that recombination is more prevalent in lineage II than lineage I and is most frequent in two house-keeping genes (ribC and purM) and the two virulence genes (actA and inlA). The relative occurrence of recombination versus point mutation is about six times higher in lineage II than in lineage I, which causes a higher genetic variability in lineage II. Unlike lineage I, lineage II represents a genetically heterogeneous population with a relatively high proportion (30% average) of genetic material imported from external sources. Phylograms, constructed with correcting for recombination, as well as Tajima's D data suggest that both lineages I and II have suffered a population bottleneck. Conclusion: Our study shows that evolutionary lineages within a single bacterial species can differ considerably in the relative contributions of recombination to genetic diversification. Accounting for recombination in phylogenetic studies is critical, and new evolutionary models that account for the possibility of changes in the rate of recombination would be required. While previous studies suggested that only L. monocytogenes lineage I has experienced a recent bottleneck, our analyses clearly show that lineage II experienced a bottleneck at about the same time, which was subsequently obscured by abundant homologous recombination after the lineage II bottleneck. While lineage I and lineage II should be considered separate species from an evolutionary viewpoint, maintaining single species name may be warranted since both lineages cause the same type of human disease

Improved Phenomenological Renormalization Schemes

An analysis is made of various methods of phenomenological renormalization based on finite-size scaling equations for inverse correlation lengths, the singular part of the free energy density, and their derivatives. The analysis is made using two-dimensional Ising and Potts lattices and the three-dimensional Ising model. Variants of equations for the phenomenological renormalization group are obtained which ensure more rapid convergence than the conventionally used Nightingale phenomenological renormalization scheme. An estimate is obtained for the critical finite-size scaling amplitude of the internal energy in the three-dimensional Ising model. It is shown that the two-dimensional Ising and Potts models contain no finite-size corrections to the internal energy so that the positions of the critical points for these models can be determined exactly from solutions for strips of finite width. It is also found that for the two-dimensional Ising model the scaling finite-size equation for the derivative of the inverse correlation length with respect to temperature gives the exact value of the thermal critical exponent.Comment: 14 pages with 1 figure in late

Select \u3cem\u3eListeria monocytogenes\u3c/em\u3e Subtypes Commonly Found in Foods Carry Distinct Nonsense Mutations in \u3cem\u3einlA\u3c/em\u3e, Leading to Expression of Truncated and Secreted Internalin A, and Are Associated with a Reduced Invasion Phenotype for Human Intestinal Epithelial Cells

The surface protein internalin A (InlA) contributes to the invasion of human intestinal epithelial cells by Listeria monocytogenes. Screening of L. monocytogenes strains isolated from human clinical cases (n=46), foods (n=118), and healthy animals (n=58) in the United States revealed mutations in inlA leading to premature stop codons (PMSCs) in L. monocytogenes ribotypes DUP-1052A and DUP-16635A (PMSC mutation type 1), DUP-1025A and DUP-1031A (PMSC mutation type 2), and DUP-1046B and DUP-1062A (PMSC mutation type 3). While all DUP-1046B, DUP-1062A, DUP-16635A, and DUP-1031A isolates (n=76) contained inlA PMSCs, ribotypes DUP-1052A and DUP-1025A (n=72) contained isolates with and without inlA PMSCs. Western immunoblotting showed that all three inlA PMSCs result in the production of truncated and secreted InlA. Searches of the Pathogen Tracker database, which contains subtype and source information for more than 5,000 L. monocytogenes isolates, revealed that the six ribotypes shown to contain isolates with inlA PMSCs were overall more commonly isolated from foods than from human listeriosis cases. L. monocytogenes strains carrying inlA PMSCs also showed significantly (P=0.0004) reduced invasion of Caco-2 cells compared to isolates with homologous 3\u27 inlA sequences without PMSCs. Invasion assays with an isogenic PMSC mutant further supported the observation that inlA PMSCs lead to reduced invasion of Caco-2 cells. Our data show that specific L. monocytogenes subtypes which are common among U.S. food isolates but rare among human listeriosis isolates carry inlA mutations that are associated with, and possibly at least partially responsible for, an attenuated invasion phenotype

A Study on Padarthamarai (படர் தாமரை)

AIM AND OBJECTIVES The skin is a delicate organ and it reflects the status of the body, either healthy or diseased. Padarthamarai is one of the commonest skin problems and it needs special attention because of its troublesome itching and recurrence. Centuries old siddhars provide correct medication in siddha science which gives wonderful relief to the skin ailments. That is why, I have choosed Padarthamarai a skin disease as my dissertation subject in order to make a thorough research study. It is therefore obvious that the practitioners of Siddha medicine primarily make use of herbal compositions. These are invariable easily accessible in rural areas, economical and also received well by human system. The main objective of this study is to highlight the efficacy of siddha drugs among the public. With this basic objective in mind, following specific objectives have been drawn. 1. To collect various literatures and modern text books as literal evidences. 2. regarding the disease Padarthamarai. 3. To expose the unique diagnostic methods mentioned by Siddhars. 4. To know the extent of correlation of the disease with age, sex, socioeconomical status, habit, family history and paruvakaalam (seasons). 5. To have a complete study of a disease Padarthamarai under the heading of mukkutram, udalkattugal, enn vagai thervu etc., in order to evaluate the pathogenesis, pathology of Padarthamarai. 6. To have a detail clinical investigation and to utilize the possible diagnostic tools in the confirmation of the diagnosis and prognosis of the disease. 7. To have a clinical trial on PADARTHAMARAI with VEPPAM PATTAI CHOORANAM as internal medicine and PALASU VITHAI CHOORANA PATTRU as external medicine. 8. To analyse the trial drugs by biochemical and pharmacological studies for complete evaluation of the drugs. 9. To highlight the factors like diet, land, climatic condition and personal hygiene in the incidence of Padarthamarai. 10. To make an awareness among the people about the prevention of the disease (personal hygienic measures). SUMMARY: 1. Twenty cases with Padarthamari cases were diagnosed clinically and admitted in the Inpatient ward were observed for laboratory investigations. Clinical prognosis and efficacy of trial medicines on Padarthamarai cases. 2. Clinical diagnosis of Padarthamarai case as done on the basis of clinical features as described in siddha maruthuvam sirappu, Yugivaidhya chinthamani and Siddha maruthuvam, Noi nadal Noi muthal nadal thirattu. 3. The trial medicines choosen for the clinical treatment of Padarthamarai case were, i) Veepam Pattai chooranam 4 gm two times a day with honey or water (internal), morning and evening after food. ii) Palasu Vithai Choorana Pattru (external application) 4. The various siddha aspects of examinations of this disease were caused out and recorded. 5. The etiology and clinical features of Padarthamarai as described in the siddha literature is more correlated with Dermatophytosis in modern medicine. 6. Females are affected Predominant than males. But the incidence of this disease is found in all age groups. 7. Six seasonal variations was noted that more number of patients were admitted in Elavenil kaalam and muthuvenil kaalam. 8. The patients belonging to poor group were affected 75% and it is due to poor personal hygiene. The onset is gradual in most of the patients. 9. In Uyirthathukkal - Samanan, Uthanan and Viyanan affected in all cases. Abanan in 20% cases and koorman in 15% of cases. Pirasagam and Sathagam are affected in all cases. Ranjagam in 50% of cases, Anarpitham in 15% of cases and Alosagam in 15% of cases and it manifested as itching, active border, constipation and loss of appetite. 10. In Udal kattugal saaram and senneer were affected in all cases . 11. In Envagai thervugal vatha pitha naadi was noted in 55% of patients, pitha vatha naadi in 25% and vatha kaba naadi in 20% of patients. 12. In Neikuri reference of urine from Padarthamarai noi 45% were refered to kaba neer, 35% were refered to pitha neer,20% were refered to vatha neer. 13. The ingredients of trial medicines were found to have the property of controlling the skin disorders especially Padarthamarai. 14. Bio-Chemical Analysis,Veepam pattai chooranam contains Chloride, unsaturated compound. 15. In Pharmacological studies of Veeepam pattai chooranam shows significant anti- inflammatory and significant antihistaminic effects. 16. The pharmacological studies of the Palasu vithai choorana pattru shows significant anti- inflammatory effect. 17. The patients were advised to take care of personal hygiene and preventive measure and to take appropriate diet during and after treatment of Padarthamari cases. CONCLUSION: 1. The treatment was given for Padarthamarai on the basis of Siddha system principles. Deranged three doshas were corrected by the author's medicine given to the padarthamarai case. 2. Veppam Pattai Chooranam as an internal medicine and Palasu Vithai Choorana Pattru as an external application respectively. 3. The internal medicine was selected from Gunapadam - mooligi vagappu and the external medicine also selected from Gunapadam - Mooligai vaguppu. 4. Signs and symptoms were relieved in 90% and reduced in 10% of cases, 5. Clinically the drugs were free from adverse effect. 6. Preparation of both, Internal and External Medicine were simple. 7. Hence it is concluded that the trial drugs were effective against padarthamarai