Cure kinetics of epoxy nanocomposites affected by MWCNTs functionalization: A review

The current paper provides an overview to emphasize the role of functionalization of multiwalled carbon nanotubes (MWCNTs) in manipulating cure kinetics of epoxy nanocomposites, which itself determines ultimate properties of the resulting compound. In this regard, the most commonly used functionalization schemes, that is, carboxylation and amidation, are thoroughly surveyed to highlight the role of functionalized nanotubes in controlling the rate of autocatalytic and vitrification kinetics. The current literature elucidates that the mechanism of curing in epoxy/MWCNTs nanocomposites remains almost unaffected by the functionalization of carbon nanotubes. On the other hand, early stage facilitation of autocatalytic reactions in the presence of MWCNTs bearing amine groups has been addressed by several researchers. When carboxylated nanotubes were used to modify MWCNTs, the rate of such reactions diminished as a consequence of heterogeneous dispersion within the epoxy matrix. At later stages of curing, however, the prolonged vitrification was seen to be dominant. Thus, the type of functional groups covalently located on the surface of MWCNTs directly affects the degree of polymer-nanotube interaction followed by enhancement of curing reaction. Our survey demonstrated that most widespread efforts ever made to represent multifarious surface-treated MWCNTs have not been directed towards preparation of epoxy nanocomposites, but they could result in property synergism

Outcomes of chronic total occlusion percutaneous coronary intervention from the RAIAN (RAjaie - Iran) registry

Objective: While most of the evidence in CTO interventions emerge from Western and Japanese studies, few data have been published up today from the Middle East. Objective of this study was to evaluate technical success rates and clinical outcomes of an Iranian population undergoing CTO PCI in a tertiary referral hospital. Moreover, we sought to evaluate the efficacy of our CTO teaching program. Methods: This is a retrospective single-center cohort study including 790 patients who underwent CTO PCI performed by operators with different volumes of CTOs PCI performed per year. According to PCI result, all patients have been divided into successful (n = 555, 70.3 %) and unsuccessful (n = 235, 29.7 %) groups. Study endpoints were Major Adverse Cardiovascular Events and Health Status Improvement evaluated using the Seattle Angina Questionnaire at one year. Results: A global success rate of 70 % for antegrade and 80 % for retrograde approach was shown despite the lack of some CTO-dedicated devices. During the enrollment period, the success rate increased significantly among operators with a lower number of CTO procedures per year. One-year MACE rate was similar in both successful and unsuccessful groups (13.5 % in successful and 10.6 % in unsuccessful group, p = 0.173). One year patients' health status improved significantly only in successful group. Conclusions: No significant differences of in-hospital and one-year MACE were found between the successful and unsuccessful groups. Angina symptoms and quality of life significantly improved after successful CTO PCI. The RAIAN registry confirmed the importance of operator expertise for CTO PCI success

Obtaining Adequate Surgical Margins in Breast-Conserving Therapy for Patients with Early-Stage Breast Cancer: Current Modalities and Future Directions

Inadequate surgical margins represent a high risk for adverse clinical outcome in breast-conserving therapy (BCT) for early-stage breast cancer. The majority of studies report positive resection margins in 20% to 40% of the patients who underwent BCT. This may result in an increased local recurrence (LR) rate or additional surgery and, consequently, adverse affects on cosmesis, psychological distress, and health costs. In the literature, various risk factors are reported to be associated with positive margin status after lumpectomy, which may allow the surgeon to distinguish those patients with a higher a priori risk for re-excision. However, most risk factors are related to tumor biology and patient characteristics, which cannot be modified as such. Therefore, efforts to reduce the number of positive margins should focus on optimizing the surgical procedure itself, because the surgeon lacks real-time intraoperative information on the presence of positive resection margins during breast-conserving surgery. This review presents the status of pre- and intraoperative modalities currently used in BCT. Furthermore, innovative intraoperative approaches, such as positron emission tomography, radioguided occult lesion localization, and near-infrared fluorescence optical imaging, are addressed, which have to prove their potential value in improving surgical outcome and reducing the need for re-excision in BCT

Intermediate versus standard-dose prophylactic anticoagulation and statin therapy versus placebo in critically-ill patients with COVID-19: Rationale and design of the INSPIRATION/INSPIRATION-S studies

Background: Microvascular and macrovascular thrombotic events are among the hallmarks of coronavirus disease 2019 (COVID-19). Furthermore, the exuberant immune response is considered an important driver of pulmonary and extrapulmonary manifestations of COVID-19. The optimal management strategy to prevent thrombosis in critically-ill patients with COVID-19 remains unknown. Methods: The Intermediate versus Standard-dose Prophylactic anticoagulation In cRitically-ill pATIents with COVID-19: An opeN label randomized controlled trial (INSPIRATION) and INSPIRATION-statin (INSPIRATION-S) studies test two independent hypotheses within a randomized controlled trial with 2 � 2 factorial design. Hospitalized critically-ill patients with reverse transcription polymerase chain reaction confirmed COVID-19 will be randomized to intermediate-dose versus standard dose prophylactic anticoagulation. The 600 patients undergoing this randomization will be screened and if meeting the eligibility criteria, will undergo an additional double-blind stratified randomization to atorvastatin 20 mg daily versus matching placebo. The primary endpoint, for both hypotheses will be tested for superiority and includes a composite of adjudicated acute arterial thrombosis, venous thromboembolism (VTE), use of extracorporeal membrane oxygenation, or all-cause death within 30 days from enrollment. Key secondary endpoints include all-cause mortality, adjudicated VTE, and ventilator-free days. Key safety endpoints include major bleeding according to the Bleeding Academic Research Consortium definition and severe thrombocytopenia (platelet count 3 times upper normal limit and clinically-diagnosed myopathy. The primary analyses will be performed in the modified intention-to-treat population. Results will be tested in exploratory analyses across key subgroups and in the intention-to-treat and per-protocol cohorts. Conclusions: INSPIRATION and INSPIRATON-S studies will help address clinically-relevant questions for antithrombotic therapy and thromboinflammatory therapy in critically-ill patients with COVID-19. © 2020 Elsevier Lt

Mechanical and Morphological Properties of Short Nylon Fiber Reinforced Acrylonitrile-Butadiene Rubber Composites

Acrylonitrile butadiene rubber (NBR) composites are prepared from waste nylon 66 short fiber using a two-roll mill mixer. The effects of fiber content and bonding agent on the mechanical and morphological properties of the composites are studied. The curing characteristics of the composites have been studied by using cure rheometer. The cure and scorch time of the composites decrease while cure rate is increased when short fiber content is increased. The mechanical properties of the composites show improvement in both longitudinal and transverse directions with increase in short fiber content. The adhesion between the fiber and rubber is enhanced by using a dry bonding system consisting of resorcinol, xamethylenetetramine and hydrated silica (HRH). The swelling behavior of the composites in N,N-dimethylformamide is tested to find the effect of bonding agent on adhesion strength of the matrix and fibers. Fracture surface morphology of composites is studied by scanning electron microscopy. The restriction to swelling is higher for composites containing bonding agent, especially, in the longitudinal direction. The morphology of the fracture surface shows less fiber pull out when the bonding agent is introduced

Nanoclay Effect on the Flow and Thermal Properties of PP/SEBS-g-MA Blend

The effect of nanoclay (Cloisite® 15A) was studied in relation to the flow behavior, mechanical and thermal properties of polypropylene/maleic anhydride-g-(styrene-ethylene-butylene-styrene) triblock copolymer (PP/SEBS(15%)-g-MA) blend. In this regard, the composites based on the blend and various amounts of nanoclay (1,3,5 wt%) were melt compounded using an internal mixer at the temperature of 190°C, rotor speed of 75rpm for 12min. The prepared samples were compression molded in a hot-press machine under the conditions of 190°C, 31 MPa pressure for 9 min to obtain the sheets in various thicknesses. The sheets were then cooled to ambient temperature with cooling water at the rate of 1.5°C.s-1. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the structure and morphology of the samples. In addition, the mechanical and thermal properties were determined by standard methods. The results of X-ray diffraction and transmission electron photographs confirmed both exfoliated and intercalated structures in the prepared samples. There were balanced strength/toughness properties in all the prepared nanocomposites by addition of both SEBS-g-MA and clay simultaneously. The measurement of rheological properties showed that as the shear rate increased, the apparent viscosity of the samples decreased (shear thinning behavior). Gradual increase in incorporation of nanoclay also decreased the melt flow index (MFI) values. In addition, increases in nanoclay content had an insignificant effect on the thermal behavior and in that respect there were slight increases in degree of crystallinity, heat deflection temperature (HDT) as well as Vicat softening point by slight increase in temperatureThe effect of nanoclay (Cloisite® 15A) was studied in relation to the flow behavior, mechanical and thermal properties of polypropylene/maleic anhydride-g-(styrene-ethylene-butylene-styrene) triblock copolymer (PP/SEBS(15%)-g-MA) blend. In this regard, the composites based on the blend and various amounts of nanoclay (1,3,5 wt%) were melt compounded using an internal mixer at the temperature of 190°C, rotor speed of 75rpm for 12min. The prepared samples were compression molded in a hot-press machine under the conditions of 190°C, 31 MPa pressure for 9 min to obtain the sheets in various thicknesses. The sheets were then cooled to ambient temperature with cooling water at the rate of 1.5°C.s-1. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the structure and morphology of the samples. In addition, the mechanical and thermal properties were determined by standard methods. The results of X-ray diffraction and transmission electron photographs confirmed both exfoliated and intercalated structures in the prepared samples. There were balanced strength/toughness properties in all the prepared nanocomposites by addition of both SEBS-g-MA and clay simultaneously. The measurement of rheological properties showed that as the shear rate increased, the apparent viscosity of the samples decreased (shear thinning behavior). Gradual increase in incorporation of nanoclay also decreased the melt flow index (MFI) values. In addition, increases in nanoclay content had an insignificant effect on the thermal behavior and in that respect there were slight increases in degree of crystallinity, heat deflection temperature (HDT) as well as Vicat softening point by slight increase in temperature.The aim of this work is to study effect of nanoclay (Cloisite® 15A) on the flow behavior, mechanical and thermal properties of polypropylene/maleic anhydride grafted-(styrene-ethylene-butylene- styrene) triblock copolymer (PP/15%SEBS-g-MA) blend. In this regard, the composites based on the blend and various amounts of nanoclay (1,3,5 wt.%) were melt compounded using an internal mixer at the temperature of 190oC, rotor speed of 75rpm for 12min. The prepared samples were then compression molded in a hot-press machine under the conditions of 190°C, 31 MPa pressure, for 9 min to obtain the sheets in various thicknesses. Afterwards, the plates were cooled to ambient temperature with cooling water at the rate of 1.5oC.s-1. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the structure and morphology of the samples. In addition, the mechanical and thermal properties were carried out by means of the standard methods. The results of X-ray diffraction and transmission electron photographs confirm both exfoliated and intercalated structures in the prepared samples. There is balanced strength/toughness properties in all the prepared nanocomposites via addition both SEBS-g-MA and clay simultaneously. The measurement of rheological properties show that as the shear rate increases, the apparent viscosity of the samples decreases (shear thinning behavior). Incorporation of nanoclay and increasing its content also decreases the melt flow index (MFI) values. In addition, increase in the nanoclay content have the insignificant effect on the thermal behavior so that slight increase in crystallinity temperature/degree, heat deflection temperature (HDT) as well as vicat softening point are obtained

Computer Simulation of Cure Process of an Axisymmetric Rubber Article Reinforced by Metal Plates Using Extended ABAQUS Code

Afinite element model is developed for simulation of the curing process of a thick axisymmetric rubber article reinforced by metal plates during the molding and cooling stages. The model consists of the heat transfer equation and a newly developed kinetics model for the determination of the state of cure in the rubber. The latter is based on the modification of the well-known Kamal-Sourour model. The thermal contact of the rubber with metallic surfaces (inserts and molds) and the variation of the thermal properties (conductivity and specific heat) with temperature and state-of-cure are taken into consideration. The ABAQUS code is used in conjunction with an in-house developed user subroutine to solve the governing equations. Having compared temperature profile and variation of the state-of-cure with experimentally measured data, the accuracy and applicability of the model is confirmed. It is also shown that this model can be successfully used for the optimization of curing process which gives rise to reduction of the molding time

Effect of Drought Stress and Biological and Chemical Fertilizerson Wheat Flag Leaf Chlorophyll and Correlation with the Grain Yield

The aim of this experiment was that study the effect of drought stress and different chemical and organic fertilizers systems on wheat flag leaf chlorophyll. This experiment was conducted as split plot based on completely randomized block design (CRBD) with four replications during 2009-2010 at experimental fields of Ramin university. Irrigation treatments were achived in I1(irrigation droped from anthesis stage to harvesting 55 zadox) and I2 (spike formation to harvesting 65 zadox) and I3 (full irrigation, control treatment), and fertilizers treatment included chemical fertilizer (NPK), manure fertilizer (M), biological fertilizer (B), biological fertilizer + manure fertilizer (MB) at the beginning of plantation. maximum and minimum chlorophyll leaf content were related to I3 and I1, respectively. Also, maximum chlorooyll was related to biological fertilizer mixed with manure (MB) and chemical fertilizers (NPK) and minimum was for biological fertilizer(B), respectively. A positive corelation was observed between grain yield and flag leaf chlorophyll at with high significance. Therefoere, flag leaf chlorophyll is a good trait selection performance under drought stress conditions and different fertilizer systems.