Ultrafast Processes in Phosphorene and Weyl semimetals

In this dissertation, we study theoretically the nonlinear response of phosphorene and Weyl semimetals to an ultrafast laser pulse. We apply a femtosecond pulse and investigate the electron dynamics of the system in terms of the conduction band population. The optical pulse induces a finite conduction band (CB) population in the reciprocal space. In case of phosphorene, which is a semiconductor with a band gap ~ 2 eV, the electron dynamics is highly irreversible which means that the residual electron CB population after the pulse is large and is comparable to the maximum conduction band population during the pulse. The large CB population appears near the Γpoint where the dipole matrix elements between the valence band and the conduction band is strong. Also, the optical pulse causes both interband and intraband electron dynamics during the pulse which a combination of both produces a net current through the system. The electron dynamics of three-dimensional topological Weyl semimetals in an ultrafast linearly polarized pulse is coherent and highly anisotropic. For some directions of pulse polarization, the electron dynamics is irreversible, while for other directions of polarization, the electron dynamics is highly reversible. Such high anisotropy in electron dynamics is related to anisotropy in interband dipole matrix elements. The optical pulse also causes net charge transfer through the system. The transferred charge has highly anisotropic dependence on polarization direction with almost zero transferred charge for some directions. Furthermore, we use the ultrafast pulse to illustrate the topological properties of Weyl semimetals such as chirality and topological resonance. The femtosecond pulse induces the topological resonance in Weyl semimetals. The topological resonance manifests itself in the distribution of the CB population. Such distribution in the conduction band is highly structured and is determined by the interference of the topological phase and the dynamic phase. The topological phase originates from the dipole. The topological resonance causes the Weyl points to be populated selectively, and this could be useful in applications such as optoelectronic devices

Spatial Analysis of Irans’ Rural Settlement

The analysis of the pattern of the arrangement of settlements in the Iran It is effective in creating and developing population centers. This research in the area of spatial planning and relying on quantitative-analytical method, has analyzed the pattern of spatial arrangement of rural settlements based on environmental factors.Therefore, it analyzes the spatial pattern of rural settlements. Morphology of the space of rural settlements in Iran according to environmental factors such as; Elevation, slope, aspect, convex and concave surfaces, land surface temperature (LST), precipitation, relative humidity have been analyzed. And by analyzing and combining these factors, raster data models and new concepts have been invented and explained. After thresholding and coding the raster data model, the spatial relationships between them have been processed and Iran's Geomorphic systems have been extracted. Then, the pattern of spatial syntax of rural settlements and the potential of environmental civilization in each of the Geomorphic systems and subsystems have been analyzed and studied. Also, the potential of environmental civilization with morphological components including Elevation, slope and aspect was calculated and analyzed. The results of this study show that the pattern of spatial syntax of rural settlements has been in interaction with Geomorphic systems and morphological components. Also, the analysis of the land spatial analysis can play an important and effective role in achieving the strategic goals of the Iranian residential system, within the framework of the principles of fundamental spatial planning

The Sources of Academic Stress among Students of the School of Medical Management and Information

Background & Objective: Studying at a university is one of the important stressful situations. Previous studies have shown the adverse effects of stress on students' physical and mental health. The aim of the current study was to determine the sources of academic stress and its relation to demographic variables in students at the School of Medical Management and Information of Shiraz University of Medical Sciences, Iran. Methods: This cross-sectional study was conducted on 95 students (65 women and 30 men) with a mean age of 21.9 ± 18-30 years (age range: 18-30). The subjects were selected using stratified random sampling method. Data were gathered using the Academic Stress Questionnaire (ASQ) and analyzed using descriptive statistical methods, independent t-test, the Pearson correlation coefficient, and ANOVA. Results: The findings indicated that the domain of "difficulty managing work, family, and university" had the highest mean score (4.02 ± 2.31) and the domain of "difficulty with interaction at the university" had the lowest mean score (2.61 ± 1.84). A significant negative association was found between age and the domain of "difficulty managing work, family, and university" (r = -0.026, P = 0.01). In addition, the mean score of second year students was significantly higher in the domains of "difficulty with academic performance in class" (P = 0.03) and "difficulty with academic performance outside the class" (P = 0.04) compared to other domains. The most common stressors were observed in the domain of "difficulty managing work, family, and university". This domain was more important among younger students. Conclusion: It is recommended that more attention be paid to this important issue in student educational and counseling programs. Key Words: Stress, Stressors, Students, Iran, School of Medical Management and Informatio

Restoring a post-traumatic partial edentulous mandible with the Toronto prosthesis: a clinical report

Implants provide support, stability and retention for restorations used in fully and partially edentulous patients. This clinical report describes prosthetic treatment of a 30-year-old man suffering from a dentoalveolar deficiency due to an old gunshot trauma to the left side of the mandible. The patient was rehabilitated with implant-supported Toronto prosthesis following surgical placement of three implants with undesirable location and angulations due to lack of sufficient bone. This prosthetic option offers advantages of both screw-retained and cement-retained prostheses and provides acceptable aesthetic and functional results

The Intravenous Laser Blood Irradiation in Chronic Pain and Fibromyalgia

Intravenous laser blood irradiation was first introduced into therapy by the Soviet scientists EN.Meschalkin and VS.Sergiewski in 1981. Originally this method was developed for the treatment of cardiovascular diseases. Improvement of rheologic properties of the blood as well as improvement of microcirculation and reduction of the area of infarction has been proved. Further, reduction of dysrhythmia and sudden cardiac death was achieved. At first, only the Helium-Neon laser (632.8 nm) was used in this therapy. For that, a power of 1-3mW and a period of exposure of 20-60 minutes were applied. The treatments were carried out once or twice a day up to ten appointments in all1. In the years after, many, and for the most part Russian studies showed  that helium-neon laser had various effects on many organs and on the hematologic and immunologic system. The studies were published mainly in Russian which were little known in the West because of decades of political separation, and were regarded with disapproval. Besides clinical research and application for patients, the cell biological basis was developed by the Estonian cell biologist Tiina Karuat the same time. An abstract is to be found in her work “The Science of Low-Power Laser-Therapy

Antioxidants rescue stressed embryos at a rate comparable with co-culturing of embryos with human umbilical cord mesenchymal cells

Purpose During laboratory manipulations, oocytes and embryos are inevitably exposed to suboptimal conditions that interfere with the normal development of embryos. Materials and methods In this study, we examined the effects of antioxidants, feeder cells and a conditioned medium on embryo development and cleavage rate following exposure of the embryos to suboptimal conditions. We exposed mouse two-cell embryos to visible light and divided them into four groups: control (E-ctr), co-culture (Co-c), conditioned medium (Cndm) and antioxidant-plus medium (Aopm). We used human umbilical cord matrixderived mesenchymal cells for co-culture. A group of embryos was not exposed to visible light and served as the non-exposed control (NE-ctr) group. Results The developmental rate was higher in NE-ctr embryos than in the E-ctr group. Exposed embryos in the various groups showed a comparable developmental rate at different stages. Blastomere number significantly increased (P<0.05) in the Co-c and Aopm groups compared with the E-ctr and Cndm groups. No significant difference was observed between the Co-c and Aopm groups. Conclusions Our data indicate that in suboptimal conditions, antioxidants could improve the embryo cleavage rate in the same way as feeder cells. Antioxidants probably improve embryo quality through their ability to scavenge reactive oxygen species

The role of co-culture systems on developmental competence of preimplantation mouse embryos against pH fluctuations

Purpose To determine the effect of pH fluctuations of culture media, and the role of co-culture systems on embryo development. Methods Mouse embryos were incubated in phosphate buffered solutions (PBSs) with different pH for various lengths of time. After 3 h incubation of embryos at various pH, the embryos were transferred into four media with human (HEF) and mouse (MEF) embryonic fibroblast cells, and without feeder cells; HTF and MEM-α. Developmental rate at day three (morula), four (expanded blastocyst) and five (hatching or hatched blastocyst) was evaluated. Results Developmental rate at day three, four and five decreased when the incubation time at pH 6.2 and 8 increased to 3 h and more. In addition, significantly less embryos incubated at pH 6.2 and 8 developed to hatching and hatched blastocysts compared with pH 7.35. Embryos incubated at pH 6.2, co-cultured with MEF or HEF showed a significant improvement (P<0.05) at day three in HEF compared to HTF, and at day five in MEF compared to HTF. At pH 8, a significant improvement (P<0.05) was observed at day five in HEF and MEF compared to MEM-α. Conclusions Mouse 2-cell embryos could tolerate minor pH fluctuations, but that major pH changes affect subsequent development. Besides, feeder cells could improve embryo development, especially when embryos are prone to rise or fall in pH

Ethical Challenges Associated with Caring for Sick Children Based on the Experiences of Nursing Students in Pediatric Wards: A Qualitative Content Analysis

Background: Nurses working in pediatric wards face many challenges when caring for sick children of different ages due to their physical and mental needs, especially if they have not been trained professionally. Nursing students and nurses are faced with ethical challenges in pediatric wards, hence their experiences can help identify the ethical problems in the healthcare setting. Since the explanation of ethical challenges depends on the context and factors such as values, beliefs, and hospital culture, this study aimed to explain the ethical challenges associated with caring for sick children based on the experiences of nursing students.Methods: This qualitative study used conventional content analysis to investigate the experiences of undergraduate and postgraduate nursing students and nurses working in pediatric wards selected by purposive sampling. Data collection tools were interviews and field notes. Data were categorized via MAXQDA10 and analyzed using conventional content analysis.Results: The participants included 3 pediatric nurses and 17 nursing students. The mean age of the participants was 24.9 ± 1.2. The findings of the study revealed the main theme i.e., ethical challenges associated with caring for sick children, was classified into two main categories including care challenges and organizational constraints. Care challenges were classified into the following subcategories: feeling worried when caring for sick children, compassionate care, emotional needs of children, inattention to family-centered care, and insufficient capability of the healthcare team. Organizational constraints were classified into facility constraints and hospital managers’ inattention to the environmental design of pediatric wards.Conclusion: The results of the study showed that the ethical challenges associated with caring for sick children were related to the healthcare team and organizational management. With the provision of appropriate training for nurses, as well as proper planning and implementation of policies to standardize the pediatric wards, nurses can provide nursing care to this age group with the least amount of moral distress