Glass Transition Temperature of Cross-Linked Epoxy Polymers: a Molecular Dynamics Study

Recently, epoxy polymers have been used in different applications and research fields due to their superior properties. In this study, the classical molecular dynamics (MD) was used to simulate formation of the epoxy polymer from cross linking of the EPON 828 with DETA curing agent, and calculate the glass transition temperature (Tg) of the material. A series of MD simulations were independently carried out on the cross-linked epoxy polymer in a range of temperatures from 600 K down to 250 K, and the density of the materials was calculated at the end of each run. Through the linear fitting between temperature and density above and below the glass transition temperature, Tg was estimated. The glass transition temperature of the pure DGEBA were also estimated through the same procedure and compared with those of the cross-linked polymer. Molecular simulations revealed significant increase in Tg of the cross-linked epoxy polymer as a result of newly created covalent bonds between individual chains. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3510

Endocrine gland abnormalities in thalassemia major: A brief review

Thalassemia major (β-thalassemia) affects a significant segment of the population in certain areas of the world. Alterations in migration patterns have changed the geographic distribution of this disease and made it a worldwide health problem. Over the course of the past 2-3 decades hypertransfusion therapy has significantly increased the life expectancy, and improved the quality of life of these patients. At the same time there has been an increase in the frequency of complications of this therapy caused by iron overload. Endocrine gland abnormalities contributed little to the morbidity or mortality of β-thalassemia in the past. As a result of hypertransfusion therapy and increased longevity, however, endocrinopathies have become more common and contribute significantly to morbidity in these patients. In this article we briefly review the current understanding of endocrine gland abnormalities, primarily caused by iron overload, in patients with thalassemia major

Effect of Supination Versus Pronation in the Non-Operative Treatment of Pediatric Supracondylar Humerus Fractures

Background: Supracondylar fracture of the humerus is the most common elbow injury that requires reduction and immobilization in the proper position to union. There are a few reports regarding the position of the forearm immobilization on elbow cosmetic outcome. Objectives: This study aimed to compare two modes of the forearm, supination and pronation in elbow deformity incidence after closed reduction and casting of this fracture. Patients and Methods: This prospective and descriptive study was carried out on children with supracondylar fracture of the humerus treated with closed reduction and cast immobilization in one of the two modes of either supination or pronation for a period of three weeks. Twenty-nine patients were immobilized in supination and 35 in pronation. Follow-up lasted for 8 months. Re-displacement was defined as the criteria and subsequent deformities of the elbow in patients, were assessed by clinical and radiographic examination. Results: A total of 64 patients, 50 boys and 14 girls, with the mean age of 4.8 years (3.1 to 8.5 years) participated. All fractures were closed and of the extension type. Forty-five cases had Gartland type II and 19 had type III fracture. Deformity of the elbow had occurred in seven cases (10.94%). Four cases of cubitus varus (CA 5 º - 16º) were observed in the supination group, of these, three patients had type III and one other had a type II fracture. In the pronation group, two cases of cubitus varus (CA 6 º - 14º) and one case of cubitus valgus (CA 17º) were observed, with type III initial fracture in all 3 cases. Conclusions: In regard to elbow malunion deformity, no obvious difference was observed between the two methods of supination and pronation in the closed treatment of supracondylar humerus fracture. However, as cubitus varus and valgus had occurred in both groups with unstable type III fractures, to prevent this complication, operative fixation is advised rather than closed reduction and position of the forearm immobilization

A systematic review of lumped-parameter equivalent circuit models for real-time estimation of lithium-ion battery states

This paper presents a systematic review for the most commonly used lumped-parameter equivalent circuit model structures in lithium-ion battery energy storage applications. These models include the Combined model, Rint model, two hysteresis models, Randles' model, a modified Randles' model and two resistor-capacitor (RC) network models with and without hysteresis included. Two variations of the lithium-ion cell chemistry, namely the lithium-ion iron phosphate (LiFePO4) and lithium nickel-manganese-cobalt oxide (LiNMC) are used for testing purposes. The model parameters and states are recursively estimated using a nonlinear system identification technique based on the dual Extended Kalman Filter (dual-EKF) algorithm. The dynamic performance of the model structures are verified using the results obtained from a self-designed pulsed-current test and an electric vehicle (EV) drive cycle based on the New European Drive Cycle (NEDC) profile over a range of operating temperatures. Analysis on the ten model structures are conducted with respect to state-of-charge (SOC) and state-of-power (SOP) estimation with erroneous initial conditions. Comparatively, both RC model structures provide the best dynamic performance, with an outstanding SOC estimation accuracy. For those cell chemistries with large inherent hysteresis levels (e.g. LiFePO4), the RC model with only one time constant is combined with a dynamic hysteresis model to further enhance the performance of the SOC estimator

The algebraic hyperstructure of elementary particles in physical theory

Algebraic hyperstructures represent a natural extension of classical algebraic structures. In a classical algebraic structure, the composition of two elements is an element, while in an algebraic hyperstructure, the composition of two elements is a set. Algebraic hyperstructure theory has a multiplicity of applications to other disciplines. The main purpose of this paper is to provide examples of hyperstructures associated with elementary particles in physical theory.Comment: 13 page

Effect of salicylic acid treatment on cadmium toxicity and leaf lipid composition in sunflower

The ameliorative effect of salicylic acid (SA) on cadmium (Cd) toxicity in sunflower plants was studied by investigating plant growth and fatty acid composition. Sunflower plants in two leaves stage were exposed to CdCl2 treatment (0, 50, 100, 150 and 200 µM) and then were treated with salicylic acid (0, 250 and 500 µM) as foliage spraying. One week after the last salicylic acid treatment,plants were harvested and growth parameters were measured . Oil of leaf was extracted in a Soxhlet system and fatty acid composition were measured by gas chromatography (GC). Statistical analyses showed excess Cd reduced growth parameters (fresh weight and length of stems and roots, fresh weight and number of leaves)and SA increased them compared with the control. Maximum reduction in these parameters was at 200 µmol Cd and 0µmol of SA. Cd caused a shift in fatty acids composition, resulting in a lower degree of their unsaturation and an increase in saturated fatty acids in sunflower leaves,whereas SA improved them. SA, particularly increased the percentage of linolenic acid and lowered that of palmitic acid by the same proportion. These results sugg membrane integrity due to lipids est that SA could be used as a potential growth regulator and a stabilizer ofprotection of cadmium-induced oxidative stress to improve plant resistance to Cd stres

Thermal instability in ionized plasma

We study magnetothermal instability in the ionized plasmas including the effects of Ohmic, ambipolar and Hall diffusion. Magnetic field in the single fluid approximation does not allow transverse thermal condensations, however, non-ideal effects highly diminish the stabilizing role of the magnetic field in thermally unstable plasmas. Therefore, enhanced growth rate of thermal condensation modes in the presence of the diffusion mechanisms speed up the rate of structure formation.Comment: Accepted for publication in Astrophysics & Space Scienc

A study on the different finite element approaches for laser cutting of aluminum alloy sheet

The effectiveness of finite element simulation techniques for laser cutting of 1.2-mm-thick aluminium sheets has been studied. Lagrangian and Arbitrary Lagrangian-Eulerian techniques were used to model and simulate laser cutting process. The reliability of finite element results were evaluated by general energy balance analysis and experimental results. Temperature and stress distribution along with heat-affected zone were predicted during the laser-induced process in line with experimental conditions under ABAQUS finite element code. Heat transfer analysis relying on thermal loading was employed to reach the best efficiency. By using field-emission scanning electron microscope, morphological, structural, and elemental changes in the cutting sections were analyzed along with the X-ray diffraction technique. Obtained stress and heat-affected zone are highly dependent on the element type as well as numerical method. Both numerical method, ALE and Lagrangian, are compared to each other in terms of power absorption, cut surface morphology, and cutting efficiency. The results show that ALE method is in good agreement with experimental data. A study on the different finite element approaches for laser cutting of aluminum alloy sheet. Available from: https://www.researchgate.net/publication/317579195_A_study_on_the_different_finite_element_approaches_for_laser_cutting_of_aluminum_alloy_sheet [accessed Jul 3, 2017]