A fractional-order model for the novel coronavirus (COVID-19) outbreak

Nonlinear Dynamics - The outbreak of the novel coronavirus (COVID-19), which was firstly reported in China, has affected many countries worldwide. To understand and predict the transmission...     

Curing Kinetics Modeling of Epoxy Modified by Fully Vulcanized Elastomer Nanoparticles Using Rheometry Method

In this study, the curing kinetics of epoxy nanocomposites containing ultra-fine full-vulcanized acrylonitrile butadiene rubber nanoparticles (UFNBRP) at different concentrations of 0, 0.5, 1 and 1.5 wt.% was investigated. In addition, the effect of curing temperatures was studied based on the rheological method under isothermal conditions. The epoxy resin/UFNBRP nanocomposites were characterized via Fourier transform infrared spectroscopy (FTIR). FTIR analysis exhibited the successful preparation of epoxy resin/UFNBRP, due to the existence of the UFNBRP characteristic peaks in the final product spectrum. The morphological structure of the epoxy resin/UFNBRP nanocomposites was investigated by both field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) studies. The FESEM and TEM studies showed UFNBRP had a spherical structure and was well dispersed in epoxy resin. The chemorheological analysis showed that due to the interactions between UFNBRP and epoxy resin, by increasing UFNBRP concentration at a constant temperature (65, 70 and 75 °C), the curing rate decreases at the gel point. Furthermore, both the curing kinetics modeling and chemorheological analysis demonstrated that the incorporation of 0.5% UFNBRP in epoxy resin matrix reduces the activation energy. The curing kinetic of epoxy resin/UFNBRP nanocomposite was best fitted with the Sestak–Berggren autocatalytic model.     

The 2 × 1 reconstruction of the rutile TiO2(0 1 1) surface: A combined density functional theory, X-ray diffraction, and scanning tunneling microscopy study

An extensive search for possible structural models of the (2 × 1)-reconstructed rutile TiO₂(0 1 1) surface was carried out by means of density functional theory (DFT) calculations. A number of models were identified that have much lower surface energies than the previously-proposed ‘titanyl’ and ‘microfaceting’ models. These new structures were tested with surface X-ray diffraction (SXRD) and voltage-dependent STM measurements. The model that is (by far) energetically most stable shows also the best agreement with SXRD data. Calculated STM images agree with the experimental ones for appropriate tunneling conditions. In contrast to previously-proposed models, this structure is not of missing-row type; because of its similarity to the fully optimized brookite TiO₂(0 0 1) surface, we call it the ‘brookite (0 0 1)-like’ model. The new surface structure exhibits two different types of undercoordinated oxygen and titanium atoms, and is, in its stoichiometric form, predicted to be rather inert towards the adsorption of probe molecules.     

An asymptotic approach to heat recirculation in diffusion flames fueled by organic particles

Journal of Thermal Analysis and Calorimetry - Owing to their safety, stability and controllability, diffusion flames have found extensive applications in medicine and power generation. Regarding...     

Irreversibility of nanomaterial due to MHD via numerical approach

Journal of Thermal Analysis and Calorimetry - In current research, MAPLE software was utilized to scrutinize the heat transfer of copper–H2O nanomaterial migration over a sheet. Entropy...     

Extraction of nanofibers from polymer blends: A brief review

This review is about the naturally formed and intentionally produced nanofibrils or nanofibers (NFs) that have been extracted and utilized or expected to be used for special applications. The diameter of NFs ranges between a few to a few hundred nanometers. Methods to arrange synthetic NFs assembly in yarns or pads forms have been examined. High throughput productions, versatility of various thermoplastics, and less environmental pollution are the advantages of the methods of extraction, which seems to make it as an economical process. It can also be used for the polymers that are difficult to be converted to NFs by electrospinning. The process is challenging and scientifically fascinating to attract the investigators. There are many more polymers to be considered, and there are many more envisioned applications that have to be practiced in the future. A theoretical base is needed for the evaluation of the effects of polymer flow parameters on the extracted NFs properties.     

Diffusion of dimethyl sulfoxide in tissue engineered collagen scaffolds visualized by computer tomography

Cryopreservation is a convenient method for long-term preservation of natural and engineered tissues in regenerative medicine. Homogeneous loading of tissues with CPAs, however, forms one of the major hurdles in tissue cryopreservation. In this study, computer tomography (CT) as a non-invasive imaging method was used to determine the effective diffusion of Me2SO in tissue-engineered collagen scaffolds. The dimensions of the scaffolds were 30 x 30 x 10 mm3 with a homogeneous pore size of 100 microm and a porosity of 98%. CT images were acquired after equilibrating the scaffolds in phosphate buffered saline (PBS) and transferring them directly in 10% (v/v)Me2SO. The Me2SO loading process of the scaffold could thus be measured and visualized in real time. The experimental data were fitted using a diffusion equation. The calculated effective diffusion constant for Me2SO in the PBS loaded scaffold was determined from experimental diffusion studies to be 2.4 x 10(-6) cm2/s at 20 degrees C.     

A model for quantitative changes in the magnetic resonance parameters of muscle in children after therapeutic irradiation

Purpose/ObjectiveThis study aimed to develop objective models of radiation effects on musculature in children with soft tissue sarcoma using treatment dosimetry and clinical and quantitative magnetic resonance imaging (MRI) parameters that may be used to guide treatment planning or predict side effects.MethodsIn the initial 13 patients undergoing external beam radiation therapy (RT) on a Phase II study of conformal or intensity-modulated RT for the treatment of soft tissue sarcoma approved by an Institutional Review Board, we evaluated quantitative MRI changes in the musculature to assess radiation-related treatment effects. Patients with soft tissue sarcoma, including Ewing's sarcoma, had quantitative T₁, T₂ and dynamic enhanced MRI (DEMRI) performed before, during (Week 4) and after RT (Week 12). Regions of interest were selected in consistent locations within and outside the high-dose regions (on ipsilateral and contralateral sides when available). Mean RT dose, T₁, T₂ and DEMRI parameters were calculated and modeled using a mixed random coefficient dose model.ResultsThe mean doses to the high- and low-dose regions were 56.4 Gy (41.8–75.3 Gy) and 13.0 Gy (0.1–37.5 Gy), respectively. Compared with tissues distant from the tumor bed, maximal enhancement was significantly increased in tissues adjacent to the tumor/tumor bed prior to RT (60.6 vs. 44.2, P=.045) and remained elevated after 12 weeks. T₁ was significantly elevated in tissues adjacent to the tumor bed prior to RT (942.4 vs. 759.0, P=.0078). The slope of longitudinal change in T₁ was greater for tissues that received low-dose irradiation than those that received high-dose irradiation (P=.0488). The effect of dose on the slope of T₂ was different (P=.0333) when younger and older patients are compared.ConclusionsAcute affects of irradiation in muscle are quantifiable via MRI. These models provide evidence that quantifiable MRI parameters may be correlated with patient parameters of radiation dose and clinical factors including patient age. Long-term follow-up will be required to determine if acute changes correlate with clinically significant late effects.     

Simultaneous study of cure kinetics and rheology of montmorillonite/vinyl ester resin nanocomposites

In this work, the effect of quaternary ammonium salt containing nanoclay content (1–5 wt%) on phase morphology, rheology, cure kinetics, and mechanical properties of the vinyl ester resin (VER)‐based nanocomposites was studied. The morphological characterization including d‐spacing measurement, microscopy observation and phase‐height image processing were performed on the prepared nanocomposites using small angel X‐ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). According to the results obtained from these techniques, it was concluded that an intercalated morphology existed for all the nanocomposites. The kinetic analyses of the isothermal curing followed by storage modulus obtained from the rheometry experiments are shown to be an affective rheological characteristic to investigate the cure behavior of VER/clay nanocomposites. In addition, the most important finding regarding the effect of nanoclay on the cross‐linking behavior of VER systems lays on the chemisorption and physisorption of the reacting monomers and initiator molecules on the nanoclay platelets surface which is found to be responsible for the retardation of the cure reaction caused by organoclay. Eventually, the mechanical characterizations were performed through the tensile, flexural and impact analysis tests. In this case, a considerable improvement of the bulk mechanical responses such as tensile and flexural strengths and also the corresponding moduli were observed for the nanocomposites. Copyright © 2011 John Wiley & Sons, Ltd.