Sharif Digital Repository

Titania nanofibers were prepared using a colloidal solution of Titania nanoparticles and a templating method. The preparation comprises impregnation of cellulose fibers in the solution containing Titania nanoparticles followed by thermal removal of the cellulose template. It is evidenced by scanning electron microscopy (SEM) that the residue substance consists of micron size fibers with a microstructure of nanofibers. The pore size distribution of the substance is multi-scale and fractal morphology was demonstrated with two fractal regimes with dimensions of 1.78 and 2.97 for sizes below and above 7.5nm, respectively. The surface area of the Titania fibers was measured about 250m2/g. The... 

We consider the fundamental problem of reachability analysis over imperative programs with real variables. Previous works that tackle reachability are either unable to handle programs consisting of general loops (e.g. symbolic execution), or lack completeness guarantees (e.g. abstract interpretation), or are not automated (e.g. incorrectness logic). In contrast, we propose a novel approach for reachability analysis that can handle general and complex loops, is complete, and can be entirely automated for a wide family of programs. Through the notion of Inductive Reachability Witnesses (IRWs), our approach extends ideas from both invariant generation and termination to reachability analysis.... 

This paper introduces a new file manager to support multiple categorization. The proposed file manager is designed based on a subtle idea named Conceptual File Management (CFM). According to this approach, files are not contained by folders; nevertheless, each file can be a member of one or more folders (concepts). A prototype file manager is designed and implemented based on the new approach. Filtering by set operations and also manual concept selection improves retrieval of the files. CFM improves file system's clarity and avoids ambiguity and redundancy. As a result, it reduces the size of file system and enhances file access  

We report a simple, inexpensive and one-step synthesis route of colloidal gold nanoparticles using arc discharge between titanium electrodes in HAuCl 4 solution achieving long-time stability. Gold nanoparticles of 8 nm diameter were formed during reduction of HAuCl4 in the plasma discharge zone. The resulting nanoparticles were characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Optical absorption spectroscopy of as prepared samples at 15 A arc current in HAuCl4 solution shows a surface plasmon resonance around 550 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal... 

Density of surface charges of cellulose fibers and -potential of TiO2 nanoparticles in the solution were measured and controlled by pH. The adsorption and clustering of TiO2 nanoparticles on the surface of cellulose fibers were studied using scanning electron microscopy (SEM) and a scale in different situations of repulsion and attraction between the particles and surface. The experiments show formation of two-dimensional clusters of nanoparticles on the surface. Weight measurement of the adsorbed particles and clusters via the adsorption time results in that there are three stages containing nucleation, two-dimensional growth and saturation for clustering of nanoparticles on the surface.... 

A new and simple method for synthesizing iodohydrins and iodoethers from aromatic alkenes is described. Iodohydrins and iodoether derivatives were prepared in excellent yield using Mercury(II) tetrafluoroborate (Hg(BF4)2.SiO2)/I2 in aqueous THF or alcohols (methanol, iso-propanol and tert-butanol). The reactions take place at room temperature, short reaction times, and high regioselectivity, following Markovnikov fashion. © 2021 Taylor & Francis Group, LLC  

A new and simple method for synthesizing iodohydrins and iodoethers from aromatic alkenes is described. Iodohydrins and iodoether derivatives were prepared in excellent yield using Mercury(II) tetrafluoroborate (Hg(BF4)2.SiO2)/I2 in aqueous THF or alcohols (methanol, iso-propanol and tert-butanol). The reactions take place at room temperature, short reaction times, and high regioselectivity, following Markovnikov fashion. © 2021 Taylor & Francis Group, LLC  

In the present study, metal complexes of 1-amidino-O-alkylureas were designed, synthesized and characterized by elemental analyses, FT-IR spectra, XRD, Mass analyses and scanning electron microscopy (SEM). All synthesized complexes were screen as α-Glucosidase inhibitors. According to the in vitro results, the Cu (II) complexes showed superior potency compared to other tested metal complexes. Particularly, [Cu(L-Me)2](Cl)2 (1b) showed the strongest inhibition against α-Glucosidase with an IC50 value of 2.75 ± 0.3 µM which was comparable to that of acarbose (IC50 = 750 µM). These findings are supported by the ligands and enzyme interactions through molecular docking. © 2021 Elsevier B.V  

A novel and high potent magnetic nanobiocomposite was prepared based on Carboxymethyl cellulose (CMC) and epichlorohydrin (ECH) cross-linker interactions to form a three-dimensional cross-linked CMC hydrogel followed by silk fibroin (SF) and halloysite nanotubes (HNTs) modifications and further in situ Fe3O4 magnetic nanoparticles (MNPs) formation. Different analytical techniques like FT-IR, EDX, FE-SEM, XRD, TGA, and VSM were used to characterize the structure of the prepared nanobiocomposite. The spherical morphology of Fe3O4 MNPs and tubular HNTs were presented in the FE-SEM images. In biological tests, since the hemolysis percent was even less than the negative control, the CMC... 

This paper deals with the nonlinear free vibration analysis of in-plane bi-directional functionally graded (IBFG) rectangular plate with porosities which are resting on Winkler-Pasternak elastic foundations. The material properties of the IBFG plate are assumed to be graded along the length and width of the plate according to the power-law distribution, as well as, even and uneven types are taken into account for porosity distributions. Equations of motion are developed by means of Hamilton's principle and von Karman nonlinearity strain-displacement relations based on classical plate theory (CPT). Afterward, the time-dependent nonlinear equations are derived by applying the Galerkin... 

The safe, highly effective measles vaccine has been recommended globally since 1974, yet in 2017 there were more than 17 million cases of measles and 83,400 deaths in children under 5 years old, and more than 99% of both occurred in low- and middle-income countries (LMICs)1–4. Globally comparable, annual, local estimates of routine first-dose measles-containing vaccine (MCV1) coverage are critical for understanding geographically precise immunity patterns, progress towards the targets of the Global Vaccine Action Plan (GVAP), and high-risk areas amid disruptions to vaccination programmes caused by coronavirus disease 2019 (COVID-19)5–8. Here we generated annual estimates of routine childhood... 

The safe, highly effective measles vaccine has been recommended globally since 1974, yet in 2017 there were more than 17 million cases of measles and 83,400 deaths in children under 5 years old, and more than 99% of both occurred in low- and middle-income countries (LMICs)1–4. Globally comparable, annual, local estimates of routine first-dose measles-containing vaccine (MCV1) coverage are critical for understanding geographically precise immunity patterns, progress towards the targets of the Global Vaccine Action Plan (GVAP), and high-risk areas amid disruptions to vaccination programmes caused by coronavirus disease 2019 (COVID-19)5–8. Here we generated annual estimates of routine childhood...