Utilization Of Language Learning Strategies By Iranian Post-Graduate Students And Their Attitude And Motivation Toward Learning English

This study investigated utilization of language learning strategies by Iranian postgraduate students and the influence of motivation and attitude on the students’ use of language learning strategies. Kerman province was selected according to cluster sampling. Then, 156 second semester post-graduate students in Kerman province were included in the present study. Data were collected through language learning strategy questionnaire developed by Oxford (1997) and Attitude/Motivation Test Battery (AMTB) adapted from Zarafshan (2002). Descriptive statistics showed that Iranian post-graduate students were high strategy users. The respondents reported the use of metacognitive, affective, compensation, social, cognitive, and memory respectively based on the frequency of use while cognitive and memory strategies were reported at a medium level and other strategies were reported at a high level. Descriptive statistics also indicated that Iranian post-graduate students had positive attitude toward learning English. Although students with positive attitude utilized the strategies more than students with negative attitude, independent sample T-test showed that attitude did not have a significant influence on utilization of language learning strategies. To determine motivation level of students, mean score for each motivation level was calculated. It showed that Iranian postgraduate students were instrumentally motivated rather than integratively motivated. It was indicated that integratively motivated students utilized strategies more than instrumentally motivated ones except for memory strategy. However, t-test indicated that instrumental motivation increased the use of memory strategies while integrative motivation increased the use of cognitive strategy. Other differences were not found to be significant. To determine the use of strategies by students of art and science, mean scores of both groups of students in strategy utilization were calculated. It showed that Arts students utilized strategies more than Science students. Overall, t-test showed that the Arts and Science majors had a statistical significant influence [t= 0.546] on the choice of cognitive strategy

Creasing of flexible membranes at vanishing tension

The properties of freestanding tensionless interfaces and membranes at low bending rigidity κ are dominated by strong fluctuations and self-avoidance and are thus outside the range of standard perturbative analysis. We analyze this regime by a simple discretized, self-avoiding membrane model on a frame subject to periodic boundary conditions by use of Monte Carlo simulation and dynamically triangulated surface techniques. We find that at low bending rigidities, the membrane properties fall into three regimes: Below the collapse transition κBP it is subject to branched polymer instability where the framed surface is not defined, in a range below a threshold rigidity κc the conformational correlation function are characterized by power-law behavior with a continuously varying exponent α, 2<α≤4 and above κc, α=4 characteristic for linearized bending excitations. Response functions specific heat and area compressibility display pronounced peaks close to κc. The results may be important for the description of soft interface systems, such as microemulsions and membranes with in-plane cooperative phenomena

Lipid configurations from molecular dynamics simulations.

The extent to which current force fields faithfully reproduce conformational properties of lipids in bilayer membranes, and whether these reflect the structural principles established for phospholipids in bilayer crystals, are central to biomembrane simulations. We determine the distribution of dihedral angles in palmitoyl-oleoyl phosphatidylcholine from molecular dynamics simulations of hydrated fluid bilayer membranes. We compare results from the widely used lipid force field of Berger et al. with those from the most recent C36 release of the CHARMM force field for lipids. Only the CHARMM force field produces the chain inequivalence with sn-1 as leading chain that is characteristic of glycerolipid packing in fluid bilayers. The exposure and high partial charge of the backbone carbonyls in Berger lipids leads to artifactual binding of Na+ ions reported in the literature. Both force fields predict coupled, near-symmetrical distributions of headgroup dihedral angles, which is compatible with models of interconverting mirror-image conformations used originally to interpret NMR order parameters. The Berger force field produces rotamer populations that correspond to the headgroup conformation found in a phosphatidylcholine lipid bilayer crystal, whereas CHARMM36 rotamer populations are closer to the more relaxed crystal conformations of phosphatidylethanolamine and glycerophosphocholine. CHARMM36 alone predicts the correct relative signs of the time-average headgroup order parameters, and reasonably reproduces the full range of NMR data from the phosphate diester to the choline methyls. There is strong motivation to seek further experimental criteria for verifying predicted conformational distributions in the choline headgroup, including the 31P chemical shift anisotropy and 14N and CD3 NMR quadrupole splittings

Computational Approaches to Explore Bacterial Toxin Entry into the Host Cell

Many bacteria secrete toxic protein complexes that modify and disrupt essential processes in the infected cell that can lead to cell death. To conduct their action, these toxins often need to cross the cell membrane and reach a specific substrate inside the cell. The investigation of these protein complexes is essential not only for understanding their biological functions but also for the rational design of targeted drug delivery vehicles that must navigate across the cell membrane to deliver their therapeutic payload. Despite the immense advances in experimental techniques, the investigations of the toxin entry mechanism have remained challenging. Computer simulations are robust complementary tools that allow for the exploration of biological processes in exceptional detail. In this review, we first highlight the strength of computational methods, with a special focus on all-atom molecular dynamics, coarse-grained, and mesoscopic models, for exploring different stages of the toxin protein entry mechanism. We then summarize recent developments that are significantly advancing our understanding, notably of the glycolipid–lectin (GL-Lect) endocytosis of bacterial Shiga and cholera toxins. The methods discussed here are also applicable to the design of membrane-penetrating nanoparticles and the study of the phenomenon of protein phase separation at the surface of the membrane. Finally, we discuss other likely routes for future development

Phenotypic evaluation of feed efficiency, growth and carcass traits in native turkeys

Improving feed efficiency decreases feed intake, total cost, and the environmental emission of poultry production. This study aimed to investigate different feed efficiency, growth and carcass traits between high and low feed efficiency birds in Iranian native turkeys. Growth and carcass characteristics of native turkeys were recorded. Four different feed efficiency traits, including feed conversion ratio (FCR), residual feed intake (RFI), residual body weight gain (RG), and residual intake and body weight gain (RIG) were calculated. The phenotypic correlations were calculated among feed efficiency measurements and different growth traits. High and low feed efficiency birds based on FCR were compared for growth and carcass traits. The phenotypic correlation between FCR and RFI was 0.5 and FCR was strongly correlated with RG and RIG. Breast muscle weight of high feed efficiency birds based of FCR was significantly higher than low feed efficiency birds. The results showed that phenotypic selection based on each of the feed efficiency traits will automatically progress the others, however, using FCR can be more straightforward in local farms and results in producing more beneficial turkeys with better growth and carcass features

Backmapping triangulated surfaces to coarse-grained membrane models

Many biological processes involve large-scale changes in membrane shape. Computer simulations of these processes are challenging since they occur across a wide range of spatiotemporal scales that cannot be investigated in full by any single current simulation technique. A potential solution is to combine different levels of resolution through a multiscale scheme. Here, we present a multiscale algorithm that backmaps a continuum membrane model represented as a dynamically triangulated surface (DTS) to its corresponding molecular model based on the coarse-grained (CG) Martini force field. Thus, we can use DTS simulations to equilibrate slow large-scale membrane conformational changes and then explore the local properties at CG resolution. We demonstrate the power of our method by backmapping a vesicular bud induced by binding of Shiga toxin and by transforming the membranes of an entire mitochondrion to near-atomic resolution. Our approach opens the way to whole cell simulations at molecular detail

Capturing Membrane Phase Separation by Dual Resolution Molecular Dynamics Simulations

[Image: see text] Understanding the lateral organization in plasma membranes remains an open problem and is of great interest to many researchers. Model membranes consisting of coexisting domains are commonly used as simplified models of plasma membranes. The coarse-grained (CG) Martini force field has successfully captured spontaneous separation of ternary membranes into a liquid-disordered and a liquid-ordered domain. With all-atom (AA) models, however, phase separation is much harder to achieve due to the slow underlying dynamics. To remedy this problem, here, we apply the virtual site (VS) hybrid method on a ternary membrane composed of saturated lipids, unsaturated lipids, and cholesterol to investigate the phase separation. The VS scheme couples the two membrane leaflets at CG and AA resolution. We found that the rapid phase separation reached by the CG leaflet can accelerate and guide this process in the AA leaflet