Hydrothermal preparation and characterization of based-alloy Bi2Te3 nanostructure with different morphology

In this paper, based-alloy Bi₂Te₃ nanostructure with different morphologies was synthesized by a hydrothermal process based on the reaction between Bi(NO₃)₃, TeCl₄, and KBH₄ in water at various conditions. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectrum and inductively coupled plasma-atomic emission spectrometer and transmission electron microscopy (TEM). The result shows that the Bi₂Te₃ crystals have diameters ranging from 20 to 25 nm with high purity. Other factors, such as the reaction time, the different capping agent and the sort of reductant also have influence on the morphology of the final products to some extent. By variation of reductant, conversion rode-like to flower-like was obtained. Organic ligands play a manifold role in the formation of the chainlike nanostructures as both coordinate ligand and architecture template, and a possible formation mechanism is proposed.     

The Impact of Trimethyl Chitosan on In Vitro Mucoadhesive Properties of Pectinate Beads along Different Sections of Gastrointestinal Tract

ABSTRACT

Pectinate (PEC) beads are multiparticulate dosage forms which have been extensively investigated for oral drug delivery; however their mucoadhesive properties in various sections of GI tract have, not been yet reported. This work evaluated the in vitro mucoadhesive properties of PEC bead formulations, on rat everted gastrointestinal sections, either with or without trimethyl chitosan (TMC), an absorption-enhancing and fairly mucoadhesive derivative of chitosan. Reference Carbomer 934P (C934P) granules, as an established mucoadhesive polymer, and ethyl cellulose (EC)-coated pellets, as a nonmucoadhesive dosage form, were also used for comparison. Water uptake studies were also performed to further explain the effect of hydration on mucoadhesive properties. PEC beads showed mucoadhesion, which was in some cases comparable to C934P granules, towards the gastrointestinal tissues with following ranking: duodenum ≈ jejunum ≈ ileum > cecum > colon > stomach. In the dry state, the beads containing TMC were more mucoadhesive, while in the moist state simple PEC beads were shown to be more mucoadhesive. Over-hydration of TMC-containing beads may account for this observation. The results of this study suggest that in cases which prehydration can be avoided, such as when the beads are protected in a site-specific oral capsule, prior to reaching the target tissue, the incorporation of TMC into beads might be useful, as a means of increasing the mucoadhesive properties; However, further studies are needed to clarify their in vivo feasibility.     

Computational investigations of baffle configuration effects on the performance of primary sedimentation tanks

To increase the performance of a primary sedimentation tank (clarifier), it is essential to have a uniform and calm flow field. The use of suitable baffle configurations may help forming favourable flow field and increase the efficiency of the primary sedimentation tank. To find the proper position and height of a baffle in a rectangular primary sedimentation tank, computational investigations are performed. Also, laboratory experiments are conducted to verify the numerical results, and the measured velocity fields that were by acoustic Doppler velocimeter (ADV) are used. The results of computational investigations performed in the present study indicate that the favourable flow field (uniform in the settling zone) would be enhanced for the case that the baffle position and height provide small circulation regions volume, or the recirculation region forms a small portion of the flow field and dissipate the kinetic energy in the tank.     

Synthesis and evaluation of uniformly sized carbamazepine-imprinted microspheres and nanospheres prepared with different mole ratios of methacrylic acid to methyl methacrylate for analytical and biomedical applications

In this work, we initiated to study new synthetic conditions to obtain uniformly sized molecularly imprinted polymers (MIPs) in the micrometer to nanometer range, using carbamazepine (CBZ) as a model template. The MIPs were successfully prepared by precipitation polymerization using methacrylic acid (MAA) and methyl methacrylate (MMA) as functional monomers at different mole ratios. The effect of MAA-to-MMA mole ratios on the morphology, binding, recognition, and release behaviors of the final particles were studied, and the adjusting possibility of these properties was also obtained. The produced polymers were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry, and their morphology was precisely examined by scanning electron microscopy and photon correlation spectroscopy. We obtained very uniform imprinted nanospheres and microspheres with diameter in the range of 120 nm to 1.74 μm under various conditions. Among the MIP nanospheres and microspheres prepared, the MIPs using MAA-to-MMA mole ratio of 1 : 2 showed nanospheres with the lower polydispersity index (0.004) and the highest selectivity factor (10.4), which is defined as the binding ratio of CBZ and oxcarbazepine as template analog. Results from binding experiments proved that MIPs exhibit specific affinity to CBZ in contrast to control polymers, and this performance was affected by pH and concentration of the loading solution. Moreover, release experiments showed the controlled release of CBZ in long-time period. The 50% of loaded CBZ was released from the imprinted nanospheres within the first 30 h, whereas another 50% was released in the following 160 h. The release kinetics of CBZ from the MIPs highly affected with the properties of particles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Using a polymer‐supported azide ion in [2+3] cycloaddition reaction of azide ion with nitriles

The [2+3] cycloaddition between various nitriles and crosslinked poly(4‐vinylpyridine) supported azide ion proceeds smoothly in the presence of ammonium bromide or ammonium chloride in N,N‐dimethyl formamide, to give the corresponding 5‐substituted‐1H‐tetrazoles in good to high yields. Conventional heating was used to promote reaction. It was found that using nitriles with electron‐withdrawing groups result in bout higher yields and lower reaction times. The present procedure offers advantages, such as shorter reaction time, and simple workup. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The novel,one step and facile synthesis of ZnO nanoparticles using heteropolyoxometalates and their photoluminescence behavior

A novel and facile wet chemical method is presented to synthesize zinc oxide nanoparticles (NPs) under ambient atmosphere and temperature. Keggin type heteropolyoxometalate (H₃[PW₁₂O₄₀]) was used as stabilizer and the effect of stirring time and amount of H₃[PW₁₂O₄₀] (HPW) were studied. XRD and TEM techniques were applied for the morphological and structural characterizations of NPs. Size of nanoparticles were determined using TEM, Scherrer’s formula as well as effective mass approximation. The results of these three methods are in good agreements and revealed single hexagonal zincite type crystalline with average particle size in the range of 3–15 nm. Photoluminescence behavior of the prepared sample shows a strong orange to red emission centred at about 620–635 nm, a green emission at around 550 nm and broad UV emission at around 400 nm.     

MHD Equilibrium and Kink Stability in Damavand Tokamak

Magnetohydrodynamic (MHD) equilibrium is vulnerable to numerous destabilizing mechanisms. Instabilities introduce distortions to the plasma magnetic surfaces and its boundaries, their driving force being the radial gradient of plasma toroidal current density. For certain modal numbers, internal kink modes may develop, and their study is feasible according to the energy principle, in which the change in total potential energy due to the disturbance is evaluated. In this article, we present a totally new analysis of MHD equilibrium and stability, and apply it to Damavand tokamak which has a large aspect ratio. For this purpose, we combine perturbation and Green’s function methods to solve for the equilibrium configuration. At this stage, plasma profiles are found explicitly in terms of Bessel functions, and we present a simple expression for estimation of total toroidal plasma current. Then the rest of plasma profiles, including poloidal magnetic flux, safety factor, and toroidal current density, are obtained and plotted. In the next step, we turn to the stability calculations and show that Damavand plasma is resistant to most of the disturbances.     

Modelling and optimization of Fischer–Tropsch products through iron catalyst in fixed-bed reactor

The most important issue for alternative renewable energy source instead of fossil fuels is environmental concern. Human energy supply from carbon waste has an important role in environmental health. Fischer–Tropsch synthesis is a reaction whereby carbon waste such as woods, foodstuffs, sewage, and any material that contains carbon in their structure, produces all oil derivatives including gasoline, diesel, etc. In this paper, the products model and the effective parameters of the model and also, the interaction between the parameters were investigated. $P_{{\text{H}}_2}$ and $T1P_{{\text{H}}_2}$ are effective parameters and interaction in the model, respectively. Finally, the optimization of products was discussed. The best operating conditions for minimizing CO₂ and CH₄ and maximizing C₂H₄ and C₂H₆ were investigated. This method can be suitable for environmental purposes.     

A Review on the Role of Stem Cells against SARS-CoV-2 in Children and Pregnant Women

Since the COVID-19 outbreak was acknowledged by the WHO on 30 January 2020, much research has been conducted to unveil various features of the responsible SARS-CoV-2 virus. Different rates of contagion in adults, children, and pregnant women may guide us to understand the underlying infection conditions of COVID-19. In this study, we first provide a review of recent reports of COVID-19 clinical outcomes in children and pregnant women. We then suggest a mechanism that explains the curious case of COVID-19 in children/pregnant women. The unique stem cell molecular signature, as well as the very low expression of angiotensin-converting enzyme 2 and the lower ACE/ACE2 ratio in stem cells of children/pregnant women compared to adults might be the cause of milder symptoms of COVID-19 in them. This study provides the main molecular keys on how stem cells can function properly and exert their immunomodulatory and regenerative effects in COVID-19-infected children/pregnant women, while failing to replicate their role in adults. This can lay the groundwork for both predicting the pattern of spread and severity of the symptoms in a population and designing novel stem cell-based treatment and prevention strategies for COVID-19.