Synthesis and Characterization of Tungstite (WO3.H2O) Nanoleaves and Nanoribbons

An environmentally benign method capable of producing large quantities of materials was used to synthesize tungstite (WO3.H2O) leaf-shaped nanoplatelets (LNPs) and nanoribbons (NRs). These materials were simply obtained by aging of colloidal solutions prepared by adding hydrochloric acid (HCl) to dilute sodium tungstate solutions (Na2WO4.2H2O) at a temperature of 5-10oC. The aging medium and the pH of the precursor solutions were also investigated. Crystallization and growth occurred by Ostwald ripening during the aging of the colloidal solutions at ambient temperature for 24 to 48hrs. When dispersed in water, the LNPs and NRs take many days to settle, which is a clear advantage for some applications (e.g., photocatalysis). The materials were characterized using scanning and transmission electron microscopy, Raman and UV/Vis spectroscopies. The current versus voltage characteristics of the tungstite NRs showed that the material behaved as a Schottky diode with a breakdown electric field of 3.0x105V.m-1. They can also be heat treated at relatively low temperatures (300oC) to form tungsten oxide (WO3) NRs and be used as photoanodes for photoelectrochemical water splitting.Comment: 12 pages, 5 figure

Is Students' Mini-Lecture An Effective Strategy to Learn English?

In most general and special English courses of the Iranian universities, reading comprehension is the main component of the syllabus. Nonetheless, in an attempt to improve listening and speaking skills, some general English courses were accompanied by oral presentations, according to which each student had to give a lecture lasting for nearly 10 minutes. The main objective was to investigate the effect of a 10-minute oral presentation on students' linguistic skills, in a comprehension-oriented syllabus. As such, two linguistically homogeneous general English classes were selected. Students in both classes were taught by the same English teacher, using the same textbook and syllabus, which, as usual, focused on reading comprehension. In one class (group 1) a 10-minute lecture, using a Power-point slide presentation software, was included in the syllabus whereas in the other class (group 2) the usual no-lecture syllabus was followed.  At the beginning of the semester, both groups took a pretest composed of a set of reading comprehension, listening comprehension, vocabulary and grammar items, and at the semester end they sat for a posttest, which was similar to the pretest. The results of the two tests were then compared using the student t-test. Comparison of the mean scores on reading comprehension, listening comprehension, vocabulary and grammar, for the pre-test and post-test,  showed no significant differences between the two groups although score gains on listening comprehension for the first group was noticeable.  The conclusion may be that mini-lectures in a reading comprehension-oriented syllabus can improve students' listening comprehension although the level of improvement may not be so significant.

An Efficient Automatic Mass Classification Method In Digitized Mammograms Using Artificial Neural Network

In this paper we present an efficient computer aided mass classification method in digitized mammograms using Artificial Neural Network (ANN), which performs benign-malignant classification on region of interest (ROI) that contains mass. One of the major mammographic characteristics for mass classification is texture. ANN exploits this important factor to classify the mass into benign or malignant. The statistical textural features used in characterizing the masses are mean, standard deviation, entropy, skewness, kurtosis and uniformity. The main aim of the method is to increase the effectiveness and efficiency of the classification process in an objective manner to reduce the numbers of false-positive of malignancies. Three layers artificial neural network (ANN) with seven features was proposed for classifying the marked regions into benign and malignant and 90.91% sensitivity and 83.87% specificity is achieved that is very much promising compare to the radiologist's sensitivity 75%.Comment: 13 pages, 10 figure

A mini-review on the most important effective medicinal plants to treat hypertension in ethnobotanical evidence of Iran.

Nowadays, cardiovascular diseases are highly prevalent in human communities. Hypertension is a multifactorial disease which causes a mortality twice higher than general population. Given the fact that medicinal plants have long been used to treat hypertension and are currently being administered for this disease, we sought to report the mostly effective and important medicinal plants on hypertension therapy in ethno-botanical evidence of Iran. In this study, hypertension, Iran, ethno-botany, medicinal plants, and traditional medicine were used as key words to search in Web of Science, PubMed, Scopus, EBSCO and EMBASE to select relevant articles. The findings of this study indicated that in Iran 40 plants in various provinces are used to treat hypertension. Because medicinal plants in this study contain effective compounds and have long been used to treat and reduce hypertension, they could provide suitable research arrangements for controlling hypertension, while effective natural drugs could be developed to control hypertension if their properties are confirmed in pharmacological studies

Van der Waals Epitaxy of Pulsed Laser Deposited Antimony Thin Films on Lattice-matched and Amorphous Substrates

Monatomic antimony thin films have recently attracted attention for applications in phase change memory, nanophotonics, and 2D materials. Although some promising results have been reported, the true potential of Sb thin films is still hindered by the scalability issue and the lack of reliable bottom-up production. Here we demonstrate the growth of Sb thin films on a lattice-matching and amorphous substrates using pulsed laser deposition (PLD). C-axis out-of-plane textured Sb thin films were successfully deposited on Sb2Te3 and SiO2/Si3N4 substrates. In the case of growth on Sb2Te3, we show that an intermediate phase is formed at the Sb2Te3-Sb interface playing a crucial role in forming a solid coupling and thus maintaining epitaxy leading to the production of high-quality Sb thin films. A 3 - 4 nm amorphous Sb seed layer was used to induce texture and suitable surface termination for the growth of Sb thin films on amorphous substrates. The deposition parameters were fine-tuned, and the growth was monitored in situ by a Reflective High Energy Electron Diffraction (RHEED). Scanning/Transmission Electron Microscopy (S/TEM) unveiled the local structure of produced films showing the formation of ꞵ-phase Sb thin films. Our results demonstrate the feasibility to produce very smooth high-quality antimony thin films with uniform coverage, from few layers to large thicknesses, using pulsed laser deposition. We believe the results of our work on scalable and controllable Sb growth have the potential to open up research on phase-change materials and optoelectronics research

Aerodynamic inverse design of transonic turbomachinery cascades

An aerodynamic inverse design method for turbomachinery cascades is presented and is implemented in a finite volume method. In this design method, the mass-averaged swirl schedule and the blade thickness distribution are prescribed. The design method then provides the blade shape that would accomplish this loading by imposing the appropriate pressure jump across the blades and satisfying the blade boundary condition, the latter implies that the flow is tangent to the blade surfaces. This inverse design method is implemented using a cell-vertex finite volume method which solves the Euler equations on unstructured triangular meshes. A five-stage Runge-Kutta pseudo-time integration scheme is used to march the solution to steady state. Non-linear artificial viscosity is added to eliminate pressure-velocity decoupling and to capture shocks. Convergence is accelerated using local time stepping and implicit residual smoothing. The boundary conditions at inflow and outflow are based on the method of characteristics. The finite volume discretization method is validated against some standard cases of internal flow as well as linear cascades. The inverse design method is first validated for three different cascades namely, a parabolic cascade, a compressor cascade and a turbine inlet guide vane. It is then used to obtain a shock-free design of an impulse transonic cascade and of the ONERA transonic compressor cascade. A parametric study has shown that the blade profile is rather sensitive to the prescribed loading distributions and that, in most cases, a smooth loading distribution results in a shock-free cascade desig

Aerodynamic inverse design of transonic turbomachinery cascades

An aerodynamic inverse design method for turbomachinery cascades is presented and is implemented in a finite volume method. In this design method, the mass-averaged swirl schedule and the blade thickness distribution are prescribed. The design method then provides the blade shape that would accomplish this loading by imposing the appropriate pressure jump across the blades and satisfying the blade boundary condition, the latter implies that the flow is tangent to the blade surfaces. This inverse design method is implemented using a cell-vertex finite volume method which solves the Euler equations on unstructured triangular meshes. A five-stage Runge-Kutta pseudo-time integration scheme is used to march the solution to steady state. Non-linear artificial viscosity is added to eliminate pressure-velocity decoupling and to capture shocks. Convergence is accelerated using local time stepping and implicit residual smoothing. The boundary conditions at inflow and outflow are based on the method of characteristics. The finite volume discretization method is validated against some standard cases of internal flow as well as linear cascades. The inverse design method is first validated for three different cascades namely, a parabolic cascade, a compressor cascade and a turbine inlet guide vane. It is then used to obtain a shock-free design of an impulse transonic cascade and of the ONERA transonic compressor cascade. A parametric study has shown that the blade profile is rather sensitive to the prescribed loading distributions and that, in most cases, a smooth loading distribution results in a shock-free cascade desig