Extreme bendability of DNA double helix due to bending asymmetry

Experimental data of the DNA cyclization (J-factor) at short length scales, as a way to study the elastic behavior of tightly bent DNA, exceed the theoretical expectation based on the wormlike chain (WLC) model by several orders of magnitude. Here, we propose that asymmetric bending rigidity of the double helix in the groove direction can be responsible for extreme bendability of DNA at short length scales and it also facilitates DNA loop formation at these lengths. To account for the bending asymmetry, we consider the asymmetric elastic rod (AER) model which has been introduced and parametrized in an earlier study (B. Eslami-Mossallam and M. Ejtehadi, Phys. Rev. E 80, 011919 (2009)). Exploiting a coarse grained representation of DNA molecule at base pair (bp) level, and using the Monte Carlo simulation method in combination with the umbrella sampling technique, we calculate the loop formation probability of DNA in the AER model. We show that, for DNA molecule has a larger J-factor compared to the WLC model which is in excellent agreement with recent experimental data.Comment: 8 pages, 9 figure

Stretching An Anisotropic DNA

We present a perturbation theory to find the response of an anisotropic DNA to the external tension. It is shown that the anisotropy has a nonzero but small contribution to the force-extension curve of the DNA. Thus an anisotropic DNA behaves like an isotropic one with an effective bending constant equal to the harmonic average of its soft and hard bending constants.Comment: 29 pages and 4 figure. To appear in J. Chem. Phy

Las percepciones de los profesores de EFL sobre los desafíos del desarrollo profesional basado en la tecnología

Pre-service teacher professional development could assume an urgent part in raising teaching quality and learning outcomes. Evolving technologies allow for new and different forms of professional development. However, teacher professional development opportunities are limited and outcomes are controversial. In this study, to capture the challenges of a technology-based professional development, the researchers examined teachers’ perceptions of the barriers to technology integration and instructional practices. Three hundred participants were recruited through an online survey- Technology-Based Professional Development Questionnaire. Through employing Structural Equation Modeling (SEM), the researchers analysed the data. The results of the study indicated that the gap between information and the use of technology-based apparatuses was viewed as related with the difficulties confronting teachers with technology-based directions. Technology-literate teachers knew how to integrate their insight into their commonsense instructing and had higher students’ commitment and inspiration. In any case, technology-illiterate teachers had mechanical troubles that reduced their education. A few ramifications can be drawn from the review, for example, the requirement for teacher instruction projects to further develop teacher consciousness of new educational innovative learning strategies, and the significance of giving chances to get computerized proficiency. Our findings have both theoretical and practical implications for pre-and in-service teacher training programs. Based on these discoveries, suggestions for the plan of online professional development and gaps for future examinations are discussed.El desarrollo profesional de los profesores de pre-servicio podría asumir un papel urgente en el aumento de la calidad de la enseñanza y los resultados del aprendizaje. La evolución de las tecnologías permite nuevas y diferentes formas de desarrollo profesional. Sin embargo, las oportunidades de desarrollo profesional de los docentes son limitadas y los resultados son polémicos. En este estudio, para capturar los desafíos de un desarrollo profesional basado en la tecnología, los investigadores examinaron las percepciones de los profesores de las barreras a la integración de la tecnología y las prácticas instruccionales. Trescientos participantes fueron reclutados a través de una encuesta en línea - cuestionario de desarrollo profesional basado en la tecnología. Mediante el empleo de modelos de ecuaciones estructurales (SEM), los investigadores analizaron los datos. Los resultados del estudio indicaron que la brecha entre la información y el uso de aparatos basados en la tecnología estaba relacionada con las dificultades que enfrentan los profesores con las direcciones basadas en la tecnología. Los maestros alfabetizen tecnología sabían cómo integrar su percepción en su sentido común de la instrucción y tenían un mayor compromiso e inspiración de los estudiantes. En cualquier caso, los profesores analfabetos en tecnología tenían problemas mecánicos que reducían su educación. Se pueden extraer algunas ramificaciones de la revisión, por ejemplo, el requisito de los proyectos de instrucción de los maestros para desarrollar aún más la conciencia de los maestros de las nuevas estrategias educativas innovadoras de aprendizaje, y la importancia de dar oportunidades para obtener dominio computarizado. Nuestros hallazgos tienen implicaciones tanto teóricas como prácticas para los programas de capacitación de maestros antes y durante el servicio. Sobre la base de estos descubrimientos, las sugerencias para el plan de desarrollo profesional en línea y las lagunas para los exámenes futuros se eliminan

Negotiations for meaning in the context of a massively multiplayer online role-playing game

This study investigated negotiations for meaning as conditions for second language (L2) learning in the context of a massively multiplayer online role-playing game, World of Warcraft (WoW) (Blizzard Entertainment, 2004). Varonis and Gass’s (1985) and Smith’s (2003a) models were used to identify negotiation episodes during on-task and off-task talks among the participants while playing WoW. The participants were six non-native (NNS) and one native English speaker (NS). The NNSs were divided into two teams of three: Team 1 (T1) pre-intermediate and Team 2 (T2) upper-intermediate. The NS played the game with both teams. The study lasted for six months and resulted in 59.96 hours of recorded audio and nine hours of screen-recorded gaming sessions. Negotiation patterns were compared across the L2 proficiency levels and three different types of dyads. The results revealed that (a) T1 encountered more communication breakdowns, but T2 engaged in more negotiations, (b) T1 engaged in more complex negotiations, (c) breakdowns and negotiations occurred more during off-task talk, and (d) breakdowns were triggered more by the NS’s utterances in T1 and by NNSs’ utterances in T2. The results also showed the participants’ abundant L2 use to undertake authentically contextualized game-driven tasks, meticulous involvement in bi- and multi-lateral negotiations, and creative strategies to resolve incomprehension

Thermal and mechanical stresses in thick spheres with an extended FGM model

In this study, an exact solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material with a new graded model is presented. The temperature distribution is assumed to be a function of radius. The material properties are graded along the radial direction according to exponential functions of radial direction. The advantage of this model, compared to the other models (linear or power law models), is in satisfaction of the material boundary conditions for several types of material variation profiles. Employing the model, the energy and Navier equations are solved using the generalized Bessel function and the Lagrange method. In addition, a method for solving the governing equations in spherical coordinates is presented. The analytical solution of the heat conduction equation and the Navier equation lead to the temperature profile, radial displacement, radial stress, and hoop stress as a function of radial direction

Effects of Peer Education and Orientation Tour on Anxiety in Patient Candidates for Coronary Angiography

Background: Coronary angiography is a stressful procedure for most patients. The physiological responses caused by anxiety during coronary angiography increase the likelihood of dysrhythmia, coronary artery spasm, and rupture. Objectives: This study compared the effects of peer education and an orientation tour on anxiety in patients who were candidates for coronary artery angiography. Patients and Methods: This single blind quasi-experimental study was conducted in 2014. A total of 177 patients who were candidates for coronary artery angiography were divided into three groups: a peer education group, an orientation tour group, and a control group. The patients in the peer education group were trained by a peer educator, and the patients in in the orientation tour group were trained by the researcher, who worked in the angiography unit. The DASS-21 questionnaire was used to measure the patients’ anxiety levels before the intervention and two hours before undergoing the coronary angiography. The data were analyzed using a Chi-square test, analysis of variance, the Kruskal-Wallis, Wilcoxon, Mann-Whitney U tests, and an interquartile range. Results: The three groups did not significantly differ regarding the mean anxiety scores before the intervention. However, a significant difference was observed between the mean anxiety scores of the three groups after the intervention (P = 0.0001). In the peer education group, the mean anxiety score was 5.34 ± 2.52 and decreased to 3.69 ± 2.87 after the intervention (P = 0.0001). In the orientation tour group, the mean anxiety was 5.53 ± 3.49, which and changed to 3.10 ± 2.22 (P = 0.0001). However, the mean anxiety score significantly increased in the control group (5.66 ± 2.94 vs. 6.53 ± 3.43, P = 0.017). Conclusions: Both methods of peer education and orientation tour decreased the anxiety levels in patients undergoing coronary artery angiography. Therefore, these approaches should be carried out according to the hospital condition and facilities