Synthesis of silicide nanomaterials using chemical vapour deposition method

Recent research has evidenced that nanotechnology may bring about a material revolution which sweeps through different scientific fields and leads to dramatic changes in the use of natural resources and our everyday life. Compared to their bulk counterparts, the nanomaterials may exhibit significantly improved physical properties by shrinking their size to nanometer scale. Metal silicide are distinguished by their features of combining advantages of both metals and semiconductors which promises superior performance various fields. Despite the progress in the synthesis methods of nanomaterials, it still remains a big challenge in controlled synthesis of 1D silicide nanostructures due to the difficulties of well-controlled synthesis conditions. In this study, synthesis process of NiSix and CoSix with different morphologies using CVD method have been analysed and determined. Synthesis of different structures of NiSix on a number of substrates has been investigated. The mechanisms behind the growth of these nanostructures have been studied for better understanding of the synthesis of these silicides. The detailed characterization techniques such as SEM, TEM and XRD were used

A Hybrid Fuzzy TOPSIS – Best Worst Method for Risk Prioritization in Megaprojects

Megaprojects are usually complex and in many cases encounter failure in terms of finish late or overspent. This study aims to investigate the critical risk factors behind these projects as well as their priority. Project risk management is a mature research stream. But when focus on megaprojects the amount of research decreases significantly. This research provides a hierarchy of risk structure in Tehran-Rasht railway megaproject and prioritizes the risk factors through a two-phase methodology. This method is a new hybrid MCDM technique consist of group fuzzy TOPSIS and fuzzy Best-Worst Method. BWM is the latest MCDM technique which in this paper, its fuzzy version combined with fuzzy TOPSIS is employed.  This research also considers all the project success criteria including time, cost and quality simultaneously and calculates the risk priority Index (RPI) accordingly. The results imply that quality is the most important project success factor and the risk elements with greater impact on project quality, get higher PRI. The identified and ranked risk factors help practitioners and academics to follow the subsequent steps of the risk management process of Iranian transportation megaprojects

True Vertigo Patients in Emergency Department; an Epidemiologic Study

Introduction: Vertigo prevalence is estimated to be 1.8% among young adults and more than 30% in the elderly. 13-38% of the referrals of patients over 65 years old in America are due to vertigo. Vertigo does not increase the risk of mortality but it can affect the patient’s quality of life. Therefore, this study was designed to evaluate the epidemiologic characteristics of vertigo patients referred to the emergency department (ED). Methods: In this 6-month retrospective cross-sectional study, the profiles of all vertigo patients referred to the ED of Imam Hossein Hospital, Tehran, Iran, from October 2013 to March 2014 were evaluated. Demographic data and baseline characteristics of the patients were recorded and then patients were divided into central and peripheral vertigo. The correlation of history and clinical examination with vertigo type was evaluated and screening performance characteristics of history and clinical examination in differentiating central and peripheral vertigo were determined. Results: 379 patients with the mean age of 50.69 ± 11.94 years (minimum 18 and maximum 86) were enrolled (58.13% female). There was no sex difference in vertigo incidence (p = 0.756). A significant correlation existed between older age and increase in frequency of central cases (p < 0.001). No significant difference was detected between the treatment protocols regarding ED length of stay (p = 0.72). There was a significant overlap between the initial diagnosis and the final decision based on imaging and neurologist’s final opinion (p < 0.001). In the end, 361 (95.3%) patients were discharged from ED, while 18 were disposed to the neurology ward. No case of mortality was reported. Conclusion: Sensitivity and specificity of history and clinical examination in differentiating central and peripheral vertigo were 99 (95% CI: 57-99) and 99 (95% CI: 97-99), respectively

Assessment of Differences between Near-Surface Air and Soil Temperatures for Reliable Detection of High-Latitude Freeze and Thaw States

Near-surface air temperature and the underlying soil temperature are among the key components of the Earth’s surface energy budget, and they are important variables for the comprehensive assessment of global climate change. Better understanding of the difference in magnitude between these two variables over high-latitude regions is also crucial for accurate detections of freeze and thaw (FT) states. However, these differences are not usually considered and included in current remote sensing-based FT detection algorithms. In this study, the difference between near-surface air temperature at the 2-meter height and soil temperature at the 5-centimeter depth is assessed using ground-based observations that span a three-year period from 2013 to 2015. Results show noticeable differences between air and soil temperatures over temporal scales that range from diurnal to seasonal. The study also suggests that the ground-based upper layer soil temperature may be a better surrogate than the near-surface air temperature for the reliable detection of FT states at high-latitudes. Furthermore, the results from this study are particularly useful for better understanding the surface energy budget that ultimately drives the land surface processes that are embedded within weather and climate models

Dimensions of Web Information Credibility: Viewpoints and Priorities of Students at Top Universities in Iran

Identifying viewpoints and priorities of students at top universities in the country regarding dimensions of web information credibility. Methodology: The research is descriptive in survey method through which viewpoints of the students were gathered using a researcher-constructed questionnaire. Gathered data were then analyzed by software SPSS in terms of canonical correlation, one sample T-test, and one-way variance analysis. Findings: The canonical correlation model indicated significance statistics in a 95% degree of confidence. Components of trustworthiness were significantly correlated to ones of expertise. Regarding dimension trustworthiness, the highest correlation was related to website identity while in dimension expertise, the highest correlation was related to accuracy. Women showed higher degrees of mean in comparison with men. Students showed different viewpoints regarding dimensions of web information credibility in such a way that expertise was prioritized than trustworthiness. Means and significance of variance analysis related to such variables as age, education, university, and familiarity were also analyzed. Conclusion: Viewpoints and priorities of students at top universities in Iran involve important implications for researchers, policy makers, website designers, and librarians. Consequently, they can be used in optimizing available websites, designing improved websites, and also in instructing and providing services

Investigating the Effect of Capital Structure and Growth Opportunities on Earnings Management

The main goal of this study is to investigate the effect of capital structure and growth opportunities on earnings management in companies accepted in Tehran securities exchange during 2008 to 2013. Before data analysis, Chow test was applied to determine the appropriate model to estimate parameters and independent variables effect on dependent variable. Then, research hypotheses were tested through pooled data method. Research results showed that there is a significant relationship between capital structure index financial leverage and earnings management. Also, research showed that there is a nonlinear and significant relationship between growth opportunities and earnings management and growth opportunities have a significant effect on this relationship

Effect of Mitomycin-C on Endothelial Cell Density and Polymegathism in Laser Assisted Sub-Epithelial Keratectomy

Purpose: To evaluate the corneal endothelial cell density and Polymegathism after laser assisted keratomileusis with mitomycin C.Patients and Methods: One hundred and three eyes from 52 patients undergoing laser assisted sub-epithelial keratomileusis using mitomycin-C 0.02% for 30 seconds entered this study. Specular microscopy was utilized to study the corneal endothelial cells before and one year after the surgery to evaluate the endothelial cell density and polymegathism. The corneal thickness was measured before and one year after the surgery.Results: The mean endothelial cell density before surgery was 2870±368/mm2, which changed to 2828±300/mm2 one year after the surgery (P=0.182). Endothelial cell size variation coefficient was 24±7 before the surgery, which changed to 25±7 one year after the surgery (P=0.039). The average stromal ablation dept was 65 micron (22 to 131 micron) and the remaining corneal thickness one year after the surgery was 488±42 micron (405 to 567 micron) (p<0.001).Conclusion: Using mitomycin C (0, 02% for 30 seconds) during the laser assisted sub-epithelial keratomileusis did not significantly change the corneal endothelial cell density one year after the surgery but the change in polymegathism was significant

Comparison of the High Cycle Fatigue Behavior of the Orthodontic NiTi Wires: An in Vitro Study

Objective: To compare the high-cycle fatigue behavior of four commercially available NiTi orthodontic wires. Material and Methods: Twelve NiTi orthodontic wires, round, 0.016-in, three per brand, were selected and divided into four groups: G1 - Heat-activated NiTi, G2 - Superelastic NiTi, G3 - Therma-Ti, and G4 - CopperNiTi. The atomic absorption spectrometry method was used to determine the chemical composition of investigated NiTi wires. We also performed a fatigue test at three-point bending using a universal testing machine for 1000 cycles in a 35 °C water bath. For the first and thousandth cycle, the average plateau load and the plateau length were determined in the unloading area of the force versus displacement diagram. In addition, we calculated the difference between the average plateau load of the first and thousandth cycle (∆F), as well as the difference between the plateau length of both cases (∆L). Results: According to our results, there were no significant differences between the average plateau load of the first and thousandth cycles of each group (p>0.05) and in the plateau length of the first and thousandth cycles of the groups (p>0.05). Conclusion: There were no significant differences between the groups changing the superelasticity property after high-cycle fatigue

Potential of satellite-based land emissivity estimates for the detection of high-latitude freeze and thaw states

Reliable detection of freeze and thaw (FT) states is crucial for the terrestrial water cycle, biogeochemical transitions, carbon and methane feedback to the atmosphere, and for the surface energy budget and its associated impacts on the global climate system. This paper is novel in that for the first time a unique approach to examine the potential of passive microwave remotely sensed land emissivity and its added-values of being free from the atmospheric effects and being sensitive to surface characteristics is being applied to the detection of FT states for latitudes north of 35°N. Since accurate characterizations of the soil state are highly dependent on land cover types, a novel threshold-based approach specific to different land cover types is proposed for daily FT detection from the use of three years (August 2012 – July 2015) of the Advanced Microwave Scanning Radiometer – 2 land emissivity estimates. Ground-based soil temperature observations are used as reference to develop threshold values for FT states. Preliminary evaluation of the proposed approach with independent ground observations over Alaska for the year 2015 shows that the use of land emissivity estimates for high-latitude FT detection is promising

Evaluation of Tear Function among Acne Vulgaris Patients Undergoing Treatment with Isotretinoin

Purpose: To evaluate the effect of Isotretinoin on tear secretion among patients with Acne Vulgaris.Patients and Methods: In this prospective study patients candidate for isotretinoin (Accutane) therapy for two months underwent complete eye examination. The best corrected visual acuity was measures and slit lamp examination of anterior segment, evaluation of tear break-up-time and Schirmer’s test were performed. The post surgical examination carried out two months post therapy consisted of complete eye examination and evaluation of dry eye level.Findings: Thirty nine patients entered the study. There were 5 patients complaining of eye strain before treatment, which rose to 19 patients after Isotretinoin therapy (p<0.001). The tear break up time was 13±1 seconds which decreased to 9±1 (p<0.001) after therapy and the Schirmer’s test mean reading was 22±2mm, which was reduced to 18±5 (p<0.001) after treatment. There were 4 patients with blepharitis before the treatment which rose to 19 patients after the end of Isotretinoin treatment (p<0.001).Conclusion: Isotretinoin usage (0.5-1mg/kg for two months) impairs the tear secretion and causes dry eye and blepharitis among patients. Considering the young age of patients using this drug, some of them candidates for keratorefractive surgery, a history of Isotretinoin usage should be considered before commencing the surgery. We recommend postponing the refractive surgery among these patients until the signs of dry eye are subsided.