2,720 research outputs found
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 models on the simple-cubic lattice with , 2, and
3, i.e. the Ising, XY, and Heisenberg models. For the critical couplings we
find and . We
simulate the three models with open surfaces and determine the surface magnetic
exponents at the ordinary transition to be ,
, and for , 2, and 3, respectively. Then we vary
the surface coupling and locate the so-called special transition at
and , where
. The corresponding surface thermal and magnetic exponents are
and for the Ising
model, and and 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 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 -Ising model as an example.
Furthermore, we calculate interface free energies of finite three-dimensional
O() models, for the three cases , 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
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