Influence of the coordination defects on the dynamics and the potential energy landscape of two-dimensional silica.

The main cause of the fragile-to-strong crossover of 3D silica was previously attributed to the presence of a low-energy cutoff in the potential energy landscape. An important question emerges about the microscopic origin of this crossover and its generalizibility to other glass-formers. In this work, the fragile-to-strong crossover of a model two-dimensional (2D) glassy system is analyzed via molecular dynamics simulation, which represents 2D-silica. By separating the sampled defect and defect-free inherent structures, we are able to identify their respective density of state distributions with respect to energy. A low energy cutoff is found in both distributions. It is shown that the fragile-to-strong crossover can be quantitatively related to the parameters of the energy landscape, involving, in particular, the low-energy cutoff of the energy distribution. It is also shown that the low-energy cutoff of the defect-states is determined by the formation energy of a specific defect configuration, involving two silicon and no oxygen defects. The low-temperature behavior of 2D silica is quantitatively compared with that of 3D silica, showing surprisingly similar behavior.

Derivation of a statistical model for classical systems obeying the fractional exclusion principle.

The violation of the Pauli principle has been surmised in several models of the fractional exclusion statistics and successfully applied to several quantum systems. In this paper, a classical alternative of the exclusion statistics is studied using the maximum entropy methods. The difference between the Bose-Einstein statistics and the Maxwell-Boltzmann statistics is understood in terms of a separable quantity, namely the degree of indistinguishability. Starting from the usual Maxwell-Boltzmann microstate counting formula, a special restriction related to the degree of indistinguishability is incorporated using Lagrange multipliers to derive the probability distribution function at equilibrium under NVE conditions. It is found that the resulting probability distribution function generates real positive values within the permissible range of parameters. For a dilute system, the probability distribution function is intermediate between the Fermi-Dirac and Bose-Einstein statistics and follows the exclusion principle. Properties of various variables of this novel statistical model are studied and possible application to classical thermodynamics is discussed.

Effect of ring stiffness and ambient pressure on the dynamical slowdown in ring polymers.

Using extensive molecular dynamics simulations, we investigate the slowdown of dynamics in a 3D system of ring polymers by varying the ambient pressure and the stiffness of the rings. Our study demonstrates that the stiffness of the rings determines the dynamics of the ring polymers, leading to glassiness at lower pressures for stiffer rings. The threading of the ring polymers, a unique feature that emerges only due to the topological nature of such polymers in three dimensions, is shown to be the determinant feature of dynamical slowdown, albeit only in a certain stiffness range. Our results suggest a possible framework for exploring the phase space spanned by ring stiffness and pressure to obtain spontaneously emerging topologically constrained polymer glasses.

Association of duodenal eosinophilia with Helicobacter pylori-negative functional dyspepsia.

BACKGROUND AND STUDY AIMS: The pathogenesis of functional dyspepsia (FD) is complex and still remains to be established. Recent studies support duodenal inflammation with increased infiltration of eosinophils and a higher level of systemic cytokines among patients with FD. These findings may help to understand the underlying pathophysiology of FD. The aim of this study was to evaluate the association between duodenal eosinophilia and FD. PATIENTS AND METHODS: A total of 84 patients (42 cases of FD and 42 subjects without dyspepsia as control, mean age 31 years, 56% female) were recruited for this prospective observational study. FD was diagnosed by validated Bangla version of the ROME III criteria. Patients with no symptoms of FD who were referred for upper gastrointestinal endoscopy for other reasons were included as control. Biopsy specimens were taken from the second part (D2) of the duodenum of all participants. The eosinophil count was quantitatively evaluated by hematoxylin and eosin staining and expressed in numbers per 5 HPF. The association between duodenal eosinophilia (defined as ≥22/5HPF a priori) and FD was assessed. RESULT: Significantly increased duodenal eosinophil count was found in patients with FD than patients without dyspepsia (p = 0.001). 57.1% of patients with FD had duodenal eosinophilia. A significant positive association was found between duodenal eosinophilia and FD (OR = 5.67, 95% CI 1.92-17.2, p = 0.001). A positive association was also observed between duodenal eosinophilia and postprandial distress syndrome (OR = 5.54, 95% CI 0.86-45.24, p = 0.036). A higher odds ratio was noticed among those who complain of early satiety. CONCLUSION: A significant positive association was found between duodenal eosinophilia and FD especially among those with postprandial distress syndrome. It requires further large scale multicenter studies to establish duodenal eosinophilia as a biomarker of FD.

Ring Statistics in 2D Silica: Effective Temperatures in Equilibrium.

The thermodynamic properties of subsystems in strong interaction with the neighborhood can largely differ from the standard behavior. Here we study the thermodynamic properties of rings and triplets in equilibrated disordered 2D silica. Their statistics follows a Boltzmann behavior, albeit with a strongly reduced temperature. This effective temperature strongly depends on the length scale of the chosen subsystem. From a systematic analysis of the 1D Ising model and an analytically solvable model, we suggest that these observations reflect the presence of strong local positive energy correlations.

Relating local structures, energies, and occurrence probabilities in a two-dimensional silica network.

Recently, it became possible to experimentally generate and characterize a very thin silica system on a substrate which can be basically described as a 2D random network. The key structural properties, in particular related to the ring statistics, could be numerically reproduced by performing molecular dynamics simulations with an appropriately chosen 2D force field. Using a maximum entropy formulation it is shown that the probability distribution of the individual rings and triplets can be related to the ring and triplet energies, respectively, obtained from the simulations. Using additional Lagrange parameters, the correct average properties of random networks are guaranteed. In agreement with previous work, based on distributions of complementary rings and triplets, respectively, one finds a Boltzmann-type relation albeit with an effective temperature which largely deviates from the bath temperature. Furthermore, it is shown that the ring and triplet energies can be estimated based on the properties of their average inner angles. This calculation supports, on a quantitative level, the previously suggested angle mismatch theory. It suggests that correlations among adjacent rings originate from the net mismatch in the inner ring angles in a triplet of rings. By taking into account an average effect from the surrounding rings of a triplet, an even better estimate of the correlations can be provided. That approach is also applied to estimate the Aboav-Wearie parameter.

Modelling the atomic arrangement of amorphous 2D silica: a network analysis.

The recent experimental discovery of a semi two-dimensional silica glass has offered a realistic description of the random network theory of a silica glass structure, initially discussed by Zachariasen. To study the structure formation of silica in two dimensions, we introduce a two-body force field, based on a soft core Yukawa potential. The different configurations, sampled via Molecular dynamics simulations, can be directly compared with the experimental structures, which have been provided in the literature. The parameters of the force field are obtained from comparison of the nearest-neighbor distances between experiment and simulation. Further key properties such as angle distributions, distribution of ring sizes and triplets of rings are analyzed and compared with the experiment. Of particular interest is the spatial correlation of ring sizes. In general, we observe a very good agreement between experiment and simulation. Additional insight from the simulations is provided about the temporal and spatial stability of the rings in dependence of their size.

Study on Liver Dysfunction in Type 2 Diabetic Patients in Bangladesh.

AIM: Diabetes mellitus (DM) represents one of the major lifestyle-related pathological conditions; the incidence and prevalence of DM have reached an epidemic level around the world. Diabetes mellitus is usually associated with obesity, coronary diseases, and cerebral pathologies. However, more insights are required to evaluate a temporal relation between DM and hepatic functions. This study assesses whether and to what extent liver functions are modified in DM patients. MATERIALS AND METHODS: A total of 100 patients with type 2 DM and 100 normal healthy controls were enrolled in this study following proper scrutiny of inclusion and exclusion criteria. Different parameters of liver function tests were measured in patients in the two groups. Data were analyzed to assess the extent and magnitude of abnormal liver functions in DM. RESULTS: The levels of bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, and prothrombin time were 0.737 ± 0.311 mg/dL, 39.00 ± 24.21 IU/L, 26.42 ± 10.40 IU/L, 4.10 ± 0.513 g/dL, and 16.46 ± 2.78 seconds in patients with DM and 0.506 ± 0.183 mg/dL, 28.26 ± 6.67 IU/L, 18.90 ± 4.75 IU/L, 4.12 ± 0.277 g/dL, and 14.23 ± 1.04 seconds in control subjects. Statistical analyses revealed that most of these parameters of liver function test were significantly different in DM patients compared to control subjects (p < 0.05). Serum alkaline phosphatase level was 89.61 ± 25.59 mg/dL in type 2 DM patients and 96.83 ± 16.34 mg/dL in control subjects (p > 0.05). The prevalence of abnormal values of serum bilirubin, ALT, AST, prothrombin time, and albumin were 5.17, 31.03, 5.17, 5.17, 43.10, and 10.34% respectively in type 2 DM patients and 0, 2, 0, 2, 3, and 0% respectively in control subjects, indicating high prevalence of DM patients with abnormal liver functions. CONCLUSION: Abnormal liver functions of different extents and magnitudes have been found in type 2 DM patients, and the impact of abnormal liver function should be considered during the management of DM patients and also to assess their long-term follow-up prognosis. HOW TO CITE THIS ARTICLE: Rashid MHO, Haque MZ, Rahman MK, Khan MMR, Rahman ASMM, Al-Mahtab M, Rahman MS, Roy PK, Islam MN. Study on Liver Dysfunction in Type 2 Diabetic Patients in Bangladesh. Euroasian J Hepato-Gastroenterol 2016;6(1):1-4.

A study on efficacy of lamivudine therapy in decompensated cirrhosis of liver due to chronic hepatitis B virus infection.

The prognosis of decompensated cirrhosis of liver resulting from chronic Hepatitis B Virus (HBV) infection is poor and liver transplantation is the only established mode of treatment. The benefits of treatment with interferon are outweighed by serious side effects and risks of fatal exacerbation of disease activity. Lamivudine rapidly reduces hepatitis B viral DNA in serum to undetectable levels. The purpose of this study was to evaluate effectiveness and safety of Lamivudine treatment in patients with advanced and end stage liver disease caused by Hepatitis B. This was a prospective observational study in which a total of 45 patients, 39 (87.0%) male and 6 (13.0%) female who had viral activity and child pugh score e" 8 were given Lamivudine 100 mg orally once daily. Among them 30 patients completed at least 6 months of therapy, majority (27 patients) showed improvement in liver function with decrease in serum ALT from mean (+/- SD) 118.8 +/- 106.5 to 50.2 +/- 57.1 U/L (p < 0.001), decrease in serum bilirubin from 73.9 +/- 80.5 to 44.7 +/- 62.9 micromol/l (p = 0.129), increase in serum albumin from 26.2 +/- 4.2 to 33.2 +/- 3.4 g/l (p < 0.05), decrease in prothrombin time from 8.3 +/- 4.0 to 3.9 +/- 2.9 seconds prolonged (p < 0.05) and reduction in child pugh score from 11.0 +/- 1.7 to 7.0 +/- 1.3 (p < 0.001). Seroconversion was found in 5 (11.1%) patients on Intention to treat analysis. Among the seroconverted group, 1 (2.2%) patient also lost HBsAg. Six (13.0%) patient had procore mutant virus, 2 (4.4%) of them showed virological response. Therefore, total 7 (15.5%) patients showed virological response by intention to treat analysis. We conclude that inhibition of viral replication with Lamivudine results in a significant improvement of liver function in patients with decompensated cirrhosis of liver due to HBV infection.